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Author SHA1 Message Date
Kemi Wang
1d90ca897c mm: update NUMA counter threshold size 
There is significant overhead in cache bouncing caused by zone counters
(NUMA associated counters) update in parallel in multi-threaded page
allocation (suggested by Dave Hansen).

This patch updates NUMA counter threshold to a fixed size of MAX_U16 - 2,
as a small threshold greatly increases the update frequency of the global
counter from local per cpu counter(suggested by Ying Huang).

The rationality is that these statistics counters don't affect the
kernel's decision, unlike other VM counters, so it's not a problem to use
a large threshold.

With this patchset, we see 31.3% drop of CPU cycles(537-->369) for per
single page allocation and reclaim on Jesper's page_bench03 benchmark.

Benchmark provided by Jesper D Brouer(increase loop times to 10000000):
https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/mm/
bench

 Threshold   CPU cycles    Throughput(88 threads)
     32          799         241760478
     64          640         301628829
     125         537         358906028 <==> system by default (base)
     256         468         412397590
     512         428         450550704
     4096        399         482520943
     20000       394         489009617
     30000       395         488017817
     65533       369(-31.3%) 521661345(+45.3%) <==> with this patchset
     N/A         342(-36.3%) 562900157(+56.8%) <==> disable zone_statistics

Link: http://lkml.kernel.org/r/1503568801-21305-3-git-send-email-kemi.wang@intel.com
Signed-off-by: Kemi Wang <kemi.wang@intel.com>
Reported-by: Jesper Dangaard Brouer <brouer@redhat.com>
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Suggested-by: Ying Huang <ying.huang@intel.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-09-08 18:26:47 -07:00
Kemi Wang
3a321d2a3d mm: change the call sites of numa statistics items 
Patch series "Separate NUMA statistics from zone statistics", v2.

Each page allocation updates a set of per-zone statistics with a call to
zone_statistics().  As discussed in 2017 MM summit, these are a
substantial source of overhead in the page allocator and are very rarely
consumed.  This significant overhead in cache bouncing caused by zone
counters (NUMA associated counters) update in parallel in multi-threaded
page allocation (pointed out by Dave Hansen).

A link to the MM summit slides:
  http://people.netfilter.org/hawk/presentations/MM-summit2017/MM-summit2017-JesperBrouer.pdf

To mitigate this overhead, this patchset separates NUMA statistics from
zone statistics framework, and update NUMA counter threshold to a fixed
size of MAX_U16 - 2, as a small threshold greatly increases the update
frequency of the global counter from local per cpu counter (suggested by
Ying Huang).  The rationality is that these statistics counters don't
need to be read often, unlike other VM counters, so it's not a problem
to use a large threshold and make readers more expensive.

With this patchset, we see 31.3% drop of CPU cycles(537-->369, see
below) for per single page allocation and reclaim on Jesper's
page_bench03 benchmark.  Meanwhile, this patchset keeps the same style
of virtual memory statistics with little end-user-visible effects (only
move the numa stats to show behind zone page stats, see the first patch
for details).

I did an experiment of single page allocation and reclaim concurrently
using Jesper's page_bench03 benchmark on a 2-Socket Broadwell-based
server (88 processors with 126G memory) with different size of threshold
of pcp counter.

Benchmark provided by Jesper D Brouer(increase loop times to 10000000):
  https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/mm/bench

   Threshold   CPU cycles    Throughput(88 threads)
      32        799         241760478
      64        640         301628829
      125       537         358906028 <==> system by default
      256       468         412397590
      512       428         450550704
      4096      399         482520943
      20000     394         489009617
      30000     395         488017817
      65533     369(-31.3%) 521661345(+45.3%) <==> with this patchset
      N/A       342(-36.3%) 562900157(+56.8%) <==> disable zone_statistics

This patch (of 3):

In this patch, NUMA statistics is separated from zone statistics
framework, all the call sites of NUMA stats are changed to use
numa-stats-specific functions, it does not have any functionality change
except that the number of NUMA stats is shown behind zone page stats
when users *read* the zone info.

E.g. cat /proc/zoneinfo
    ***Base***                           ***With this patch***
nr_free_pages 3976                         nr_free_pages 3976
nr_zone_inactive_anon 0                    nr_zone_inactive_anon 0
nr_zone_active_anon 0                      nr_zone_active_anon 0
nr_zone_inactive_file 0                    nr_zone_inactive_file 0
nr_zone_active_file 0                      nr_zone_active_file 0
nr_zone_unevictable 0                      nr_zone_unevictable 0
nr_zone_write_pending 0                    nr_zone_write_pending 0
nr_mlock     0                             nr_mlock     0
nr_page_table_pages 0                      nr_page_table_pages 0
nr_kernel_stack 0                          nr_kernel_stack 0
nr_bounce    0                             nr_bounce    0
nr_zspages   0                             nr_zspages   0
numa_hit 0                                *nr_free_cma  0*
numa_miss 0                                numa_hit     0
numa_foreign 0                             numa_miss    0
numa_interleave 0                          numa_foreign 0
numa_local   0                             numa_interleave 0
numa_other   0                             numa_local   0
*nr_free_cma 0*                            numa_other 0
    ...                                        ...
vm stats threshold: 10                     vm stats threshold: 10
    ...                                        ...

The next patch updates the numa stats counter size and threshold.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1503568801-21305-2-git-send-email-kemi.wang@intel.com
Signed-off-by: Kemi Wang <kemi.wang@intel.com>
Reported-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Ying Huang <ying.huang@intel.com>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-09-08 18:26:47 -07:00
Huang Ying
cbc65df240 mm, swap: add swap readahead hit statistics 
Patch series "mm, swap: VMA based swap readahead", v4.

The swap readahead is an important mechanism to reduce the swap in
latency.  Although pure sequential memory access pattern isn't very
popular for anonymous memory, the space locality is still considered
valid.

In the original swap readahead implementation, the consecutive blocks in
swap device are readahead based on the global space locality estimation.
But the consecutive blocks in swap device just reflect the order of page
reclaiming, don't necessarily reflect the access pattern in virtual
memory space.  And the different tasks in the system may have different
access patterns, which makes the global space locality estimation
incorrect.

In this patchset, when page fault occurs, the virtual pages near the
fault address will be readahead instead of the swap slots near the fault
swap slot in swap device.  This avoid to readahead the unrelated swap
slots.  At the same time, the swap readahead is changed to work on
per-VMA from globally.  So that the different access patterns of the
different VMAs could be distinguished, and the different readahead
policy could be applied accordingly.  The original core readahead
detection and scaling algorithm is reused, because it is an effect
algorithm to detect the space locality.

In addition to the swap readahead changes, some new sysfs interface is
added to show the efficiency of the readahead algorithm and some other
swap statistics.

This new implementation will incur more small random read, on SSD, the
improved correctness of estimation and readahead target should beat the
potential increased overhead, this is also illustrated in the test
results below.  But on HDD, the overhead may beat the benefit, so the
original implementation will be used by default.

The test and result is as follow,

Common test condition
=====================

Test Machine: Xeon E5 v3 (2 sockets, 72 threads, 32G RAM)
Swap device: NVMe disk

Micro-benchmark with combined access pattern
============================================

vm-scalability, sequential swap test case, 4 processes to eat 50G
virtual memory space, repeat the sequential memory writing until 300
seconds.  The first round writing will trigger swap out, the following
rounds will trigger sequential swap in and out.

At the same time, run vm-scalability random swap test case in
background, 8 processes to eat 30G virtual memory space, repeat the
random memory write until 300 seconds.  This will trigger random swap-in
in the background.

This is a combined workload with sequential and random memory accessing
at the same time.  The result (for sequential workload) is as follow,

			Base		Optimized
			----		---------
throughput		345413 KB/s	414029 KB/s (+19.9%)
latency.average		97.14 us	61.06 us (-37.1%)
latency.50th		2 us		1 us
latency.60th		2 us		1 us
latency.70th		98 us		2 us
latency.80th		160 us		2 us
latency.90th		260 us		217 us
latency.95th		346 us		369 us
latency.99th		1.34 ms		1.09 ms
ra_hit%			52.69%		99.98%

The original swap readahead algorithm is confused by the background
random access workload, so readahead hit rate is lower.  The VMA-base
readahead algorithm works much better.

Linpack
=======

The test memory size is bigger than RAM to trigger swapping.

			Base		Optimized
			----		---------
elapsed_time		393.49 s	329.88 s (-16.2%)
ra_hit%			86.21%		98.82%

The score of base and optimized kernel hasn't visible changes.  But the
elapsed time reduced and readahead hit rate improved, so the optimized
kernel runs better for startup and tear down stages.  And the absolute
value of readahead hit rate is high, shows that the space locality is
still valid in some practical workloads.

This patch (of 5):

The statistics for total readahead pages and total readahead hits are
recorded and exported via the following sysfs interface.

/sys/kernel/mm/swap/ra_hits
/sys/kernel/mm/swap/ra_total

With them, the efficiency of the swap readahead could be measured, so
that the swap readahead algorithm and parameters could be tuned
accordingly.

[akpm@linux-foundation.org: don't display swap stats if CONFIG_SWAP=n]
Link: http://lkml.kernel.org/r/20170807054038.1843-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-09-06 17:27:29 -07:00
SeongJae Park
f113e64121 mm/vmstat.c: fix wrong comment 
Comment for pagetypeinfo_showblockcount() is mistakenly duplicated from
pagetypeinfo_show_free()'s comment.  This commit fixes it.

Link: http://lkml.kernel.org/r/20170809185816.11244-1-sj38.park@gmail.com
Fixes: 467c996c1e ("Print out statistics in relation to fragmentation avoidance to /proc/pagetypeinfo")
Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-09-06 17:27:29 -07:00
Wen Yang
88d6ac40c1 mm/vmstat: fix divide error at __fragmentation_index 
When order is -1 or too big, *1UL << order* will be 0, which will cause
a divide error.  Although it seems that all callers of
__fragmentation_index() will only do so with a valid order, the patch
can make it more robust.

Should prevent reoccurrences of
https://bugzilla.kernel.org/show_bug.cgi?id=196555

Link: http://lkml.kernel.org/r/1501751520-2598-1-git-send-email-wen.yang99@zte.com.cn
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Reviewed-by: Jiang Biao <jiang.biao2@zte.com.cn>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-09-06 17:27:29 -07:00
Michal Hocko
c41f012ade mm: rename global_page_state to global_zone_page_state 
global_page_state is error prone as a recent bug report pointed out [1].
It only returns proper values for zone based counters as the enum it
gets suggests.  We already have global_node_page_state so let's rename
global_page_state to global_zone_page_state to be more explicit here.
All existing users seems to be correct:

$ git grep "global_page_state(NR_" | sed 's@.*(\(NR_[A-Z_]*\)).*@\1@' | sort | uniq -c
      2 NR_BOUNCE
      2 NR_FREE_CMA_PAGES
     11 NR_FREE_PAGES
      1 NR_KERNEL_STACK_KB
      1 NR_MLOCK
      2 NR_PAGETABLE

This patch shouldn't introduce any functional change.

[1] http://lkml.kernel.org/r/201707260628.v6Q6SmaS030814@www262.sakura.ne.jp

Link: http://lkml.kernel.org/r/20170801134256.5400-2-hannes@cmpxchg.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-09-06 17:27:29 -07:00
Huang Ying
fe490cc0fe mm, THP, swap: add THP swapping out fallback counting 
When swapping out THP (Transparent Huge Page), instead of swapping out
the THP as a whole, sometimes we have to fallback to split the THP into
normal pages before swapping, because no free swap clusters are
available, or cgroup limit is exceeded, etc.  To count the number of the
fallback, a new VM event THP_SWPOUT_FALLBACK is added, and counted when
we fallback to split the THP.

Link: http://lkml.kernel.org/r/20170724051840.2309-13-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c]
Cc: Vishal L Verma <vishal.l.verma@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-09-06 17:27:28 -07:00
Huang Ying
225311a464 mm: test code to write THP to swap device as a whole 
To support delay splitting THP (Transparent Huge Page) after swapped
out, we need to enhance swap writing code to support to write a THP as a
whole.  This will improve swap write IO performance.

As Ming Lei <ming.lei@redhat.com> pointed out, this should be based on
multipage bvec support, which hasn't been merged yet.  So this patch is
only for testing the functionality of the other patches in the series.
And will be reimplemented after multipage bvec support is merged.

Link: http://lkml.kernel.org/r/20170724051840.2309-7-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c]
Cc: Shaohua Li <shli@kernel.org>
Cc: Vishal L Verma <vishal.l.verma@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-09-06 17:27:28 -07:00
Vinayak Menon
727c080f03 mm: avoid taking zone lock in pagetypeinfo_showmixed() 
pagetypeinfo_showmixedcount_print is found to take a lot of time to
complete and it does this holding the zone lock and disabling
interrupts.  In some cases it is found to take more than a second (On a
2.4GHz,8Gb RAM,arm64 cpu).

Avoid taking the zone lock similar to what is done by read_page_owner,
which means possibility of inaccurate results.

Link: http://lkml.kernel.org/r/1498045643-12257-1-git-send-email-vinmenon@codeaurora.org
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: zhongjiang <zhongjiang@huawei.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-07-10 16:32:32 -07:00
Johannes Weiner
385386cff4 mm: vmstat: move slab statistics from zone to node counters 
Patch series "mm: per-lruvec slab stats"

Josef is working on a new approach to balancing slab caches and the page
cache.  For this to work, he needs slab cache statistics on the lruvec
level.  These patches implement that by adding infrastructure that
allows updating and reading generic VM stat items per lruvec, then
switches some existing VM accounting sites, including the slab
accounting ones, to this new cgroup-aware API.

I'll follow up with more patches on this, because there is actually
substantial simplification that can be done to the memory controller
when we replace private memcg accounting with making the existing VM
accounting sites cgroup-aware.  But this is enough for Josef to base his
slab reclaim work on, so here goes.

This patch (of 5):

To re-implement slab cache vs.  page cache balancing, we'll need the
slab counters at the lruvec level, which, ever since lru reclaim was
moved from the zone to the node, is the intersection of the node, not
the zone, and the memcg.

We could retain the per-zone counters for when the page allocator dumps
its memory information on failures, and have counters on both levels -
which on all but NUMA node 0 is usually redundant.  But let's keep it
simple for now and just move them.  If anybody complains we can restore
the per-zone counters.

[hannes@cmpxchg.org: fix oops]
  Link: http://lkml.kernel.org/r/20170605183511.GA8915@cmpxchg.org
Link: http://lkml.kernel.org/r/20170530181724.27197-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-07-06 16:24:35 -07:00
Konstantin Khlebnikov
8e675f7af5 mm/oom_kill: count global and memory cgroup oom kills 
Show count of oom killer invocations in /proc/vmstat and count of
processes killed in memory cgroup in knob "memory.events" (in
memory.oom_control for v1 cgroup).

Also describe difference between "oom" and "oom_kill" in memory cgroup
documentation.  Currently oom in memory cgroup kills tasks iff shortage
has happened inside page fault.

These counters helps in monitoring oom kills - for now the only way is
grepping for magic words in kernel log.

[akpm@linux-foundation.org: fix for mem_cgroup_count_vm_event() rename]
[akpm@linux-foundation.org: fix comment, per Konstantin]
Link: http://lkml.kernel.org/r/149570810989.203600.9492483715840752937.stgit@buzz
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Roman Guschin <guroan@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-07-06 16:24:35 -07:00
Michal Hocko
d336e94e44 mm, vmstat: skip reporting offline pages in pagetypeinfo 
pagetypeinfo_showblockcount_print skips over invalid pfns but it would
report pages which are offline because those have a valid pfn.  Their
migrate type is misleading at best.

Now that we have pfn_to_online_page() we can use it instead of
pfn_valid() and fix this.

[mhocko@suse.com: fix build]
  Link: http://lkml.kernel.org/r/20170519072225.GA13041@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/20170515085827.16474-11-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Joonsoo Kim <js1304@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Daniel Kiper <daniel.kiper@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Tobias Regnery <tobias.regnery@gmail.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-07-06 16:24:32 -07:00
Anshuman Khandual
9d85e15f1d mm/vmstat.c: standardize file operations variable names 
Standardize the file operation variable names related to all four memory
management /proc interface files.  Also change all the symbol
permissions (S_IRUGO) into octal permissions (0444) as it got complaints
from checkpatch.pl.  This does not create any functional change to the
interface.

Link: http://lkml.kernel.org/r/20170427030632.8588-1-khandual@linux.vnet.ibm.com
Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-07-06 16:24:31 -07:00
Reza Arbab
8d35bb3106 mm, vmstat: Remove spurious WARN() during zoneinfo print 
After commit e2ecc8a79e ("mm, vmstat: print non-populated zones in
zoneinfo"), /proc/zoneinfo will show unpopulated zones.

A memoryless node, having no populated zones at all, was previously
ignored, but will now trigger the WARN() in is_zone_first_populated().

Remove this warning, as its only purpose was to warn of a situation that
has since been enabled.

Aside: The "per-node stats" are still printed under the first populated
zone, but that's not necessarily the first stanza any more.  I'm not
sure which criteria is more important with regard to not breaking
parsers, but it looks a little weird to the eye.

Fixes:  e2ecc8a79e ("mm, vmstat: print node-based stats in zoneinfo file")
Link: http://lkml.kernel.org/r/1493854905-10918-1-git-send-email-arbab@linux.vnet.ibm.com
Signed-off-by: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-05-12 15:57:15 -07:00
David Rientjes
7dfb8bf3b9 mm, vmstat: suppress pcp stats for unpopulated zones in zoneinfo 
After "mm, vmstat: print non-populated zones in zoneinfo",
/proc/zoneinfo will show unpopulated zones.

The per-cpu pageset statistics are not relevant for unpopulated zones
and can be potentially lengthy, so supress them when they are not
interesting.

Also moves lowmem reserve protection information above pcp stats since
it is relevant for all zones per vm.lowmem_reserve_ratio.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1703061400500.46428@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-05-03 15:52:08 -07:00
David Rientjes
b2bd859819 mm, vmstat: print non-populated zones in zoneinfo 
Initscripts can use the information (protection levels) from
/proc/zoneinfo to configure vm.lowmem_reserve_ratio at boot.

vm.lowmem_reserve_ratio is an array of ratios for each configured zone
on the system.  If a zone is not populated on an arch, /proc/zoneinfo
suppresses its output.

This results in there not being a 1:1 mapping between the set of zones
emitted by /proc/zoneinfo and the zones configured by
vm.lowmem_reserve_ratio.

This patch shows statistics for non-populated zones in /proc/zoneinfo.
The zones exist and hold a spot in the vm.lowmem_reserve_ratio array.
Without this patch, it is not possible to determine which index in the
array controls which zone if one or more zones on the system are not
populated.

Remaining users of walk_zones_in_node() are unchanged.  Files such as
/proc/pagetypeinfo require certain zone data to be initialized properly
for display, which is not done for unpopulated zones.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1703031451310.98023@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-05-03 15:52:08 -07:00
Shaohua Li
f7ad2a6cb9 mm: move MADV_FREE pages into LRU_INACTIVE_FILE list 
madv()'s MADV_FREE indicate pages are 'lazyfree'.  They are still
anonymous pages, but they can be freed without pageout.  To distinguish
these from normal anonymous pages, we clear their SwapBacked flag.

MADV_FREE pages could be freed without pageout, so they pretty much like
used once file pages.  For such pages, we'd like to reclaim them once
there is memory pressure.  Also it might be unfair reclaiming MADV_FREE
pages always before used once file pages and we definitively want to
reclaim the pages before other anonymous and file pages.

To speed up MADV_FREE pages reclaim, we put the pages into
LRU_INACTIVE_FILE list.  The rationale is LRU_INACTIVE_FILE list is tiny
nowadays and should be full of used once file pages.  Reclaiming
MADV_FREE pages will not have much interfere of anonymous and active
file pages.  And the inactive file pages and MADV_FREE pages will be
reclaimed according to their age, so we don't reclaim too many MADV_FREE
pages too.  Putting the MADV_FREE pages into LRU_INACTIVE_FILE_LIST also
means we can reclaim the pages without swap support.  This idea is
suggested by Johannes.

This patch doesn't move MADV_FREE pages to LRU_INACTIVE_FILE list yet to
avoid bisect failure, next patch will do it.

The patch is based on Minchan's original patch.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/2f87063c1e9354677b7618c647abde77b07561e5.1487965799.git.shli@fb.com
Signed-off-by: Shaohua Li <shli@fb.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-05-03 15:52:08 -07:00
Johannes Weiner
c822f6223d mm: delete NR_PAGES_SCANNED and pgdat_reclaimable() 
NR_PAGES_SCANNED counts number of pages scanned since the last page free
event in the allocator.  This was used primarily to measure the
reclaimability of zones and nodes, and determine when reclaim should
give up on them.  In that role, it has been replaced in the preceding
patches by a different mechanism.

Being implemented as an efficient vmstat counter, it was automatically
exported to userspace as well.  It's however unlikely that anyone
outside the kernel is using this counter in any meaningful way.

Remove the counter and the unused pgdat_reclaimable().

Link: http://lkml.kernel.org/r/20170228214007.5621-8-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Jia He <hejianet@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-05-03 15:52:08 -07:00
Johannes Weiner
c73322d098 mm: fix 100% CPU kswapd busyloop on unreclaimable nodes 
Patch series "mm: kswapd spinning on unreclaimable nodes - fixes and
cleanups".

Jia reported a scenario in which the kswapd of a node indefinitely spins
at 100% CPU usage.  We have seen similar cases at Facebook.

The kernel's current method of judging its ability to reclaim a node (or
whether to back off and sleep) is based on the amount of scanned pages
in proportion to the amount of reclaimable pages.  In Jia's and our
scenarios, there are no reclaimable pages in the node, however, and the
condition for backing off is never met.  Kswapd busyloops in an attempt
to restore the watermarks while having nothing to work with.

This series reworks the definition of an unreclaimable node based not on
scanning but on whether kswapd is able to actually reclaim pages in
MAX_RECLAIM_RETRIES (16) consecutive runs.  This is the same criteria
the page allocator uses for giving up on direct reclaim and invoking the
OOM killer.  If it cannot free any pages, kswapd will go to sleep and
leave further attempts to direct reclaim invocations, which will either
make progress and re-enable kswapd, or invoke the OOM killer.

Patch #1 fixes the immediate problem Jia reported, the remainder are
smaller fixlets, cleanups, and overall phasing out of the old method.

Patch #6 is the odd one out.  It's a nice cleanup to get_scan_count(),
and directly related to #5, but in itself not relevant to the series.

If the whole series is too ambitious for 4.11, I would consider the
first three patches fixes, the rest cleanups.

This patch (of 9):

Jia He reports a problem with kswapd spinning at 100% CPU when
requesting more hugepages than memory available in the system:

$ echo 4000 >/proc/sys/vm/nr_hugepages

top - 13:42:59 up  3:37,  1 user,  load average: 1.09, 1.03, 1.01
Tasks:   1 total,   1 running,   0 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.0 us, 12.5 sy,  0.0 ni, 85.5 id,  2.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem:  31371520 total, 30915136 used,   456384 free,      320 buffers
KiB Swap:  6284224 total,   115712 used,  6168512 free.    48192 cached Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
   76 root      20   0       0      0      0 R 100.0 0.000 217:17.29 kswapd3

At that time, there are no reclaimable pages left in the node, but as
kswapd fails to restore the high watermarks it refuses to go to sleep.

Kswapd needs to back away from nodes that fail to balance.  Up until
commit 1d82de618d ("mm, vmscan: make kswapd reclaim in terms of
nodes") kswapd had such a mechanism.  It considered zones whose
theoretically reclaimable pages it had reclaimed six times over as
unreclaimable and backed away from them.  This guard was erroneously
removed as the patch changed the definition of a balanced node.

However, simply restoring this code wouldn't help in the case reported
here: there *are* no reclaimable pages that could be scanned until the
threshold is met.  Kswapd would stay awake anyway.

Introduce a new and much simpler way of backing off.  If kswapd runs
through MAX_RECLAIM_RETRIES (16) cycles without reclaiming a single
page, make it back off from the node.  This is the same number of shots
direct reclaim takes before declaring OOM.  Kswapd will go to sleep on
that node until a direct reclaimer manages to reclaim some pages, thus
proving the node reclaimable again.

[hannes@cmpxchg.org: check kswapd failure against the cumulative nr_reclaimed count]
  Link: http://lkml.kernel.org/r/20170306162410.GB2090@cmpxchg.org
[shakeelb@google.com: fix condition for throttle_direct_reclaim]
  Link: http://lkml.kernel.org/r/20170314183228.20152-1-shakeelb@google.com
Link: http://lkml.kernel.org/r/20170228214007.5621-2-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Reported-by: Jia He <hejianet@gmail.com>
Tested-by: Jia He <hejianet@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-05-03 15:52:07 -07:00
Michal Hocko
80d136e138 mm: make mm_percpu_wq non freezable 
Geert has reported a freeze during PM resume and some additional
debugging has shown that the device_resume worker cannot make a forward
progress because it waits for an event which is stuck waiting in
drain_all_pages:

  INFO: task kworker/u4:0:5 blocked for more than 120 seconds.
        Not tainted 4.11.0-rc7-koelsch-00029-g005882e53d62f25d-dirty #3476
  "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  kworker/u4:0    D    0     5      2 0x00000000
  Workqueue: events_unbound async_run_entry_fn
    __schedule
    schedule
    schedule_timeout
    wait_for_common
    dpm_wait_for_superior
    device_resume
    async_resume
    async_run_entry_fn
    process_one_work
    worker_thread
    kthread
  [...]
  bash            D    0  1703   1694 0x00000000
    __schedule
    schedule
    schedule_timeout
    wait_for_common
    flush_work
    drain_all_pages
    start_isolate_page_range
    alloc_contig_range
    cma_alloc
    __alloc_from_contiguous
    cma_allocator_alloc
    __dma_alloc
    arm_dma_alloc
    sh_eth_ring_init
    sh_eth_open
    sh_eth_resume
    dpm_run_callback
    device_resume
    dpm_resume
    dpm_resume_end
    suspend_devices_and_enter
    pm_suspend
    state_store
    kernfs_fop_write
    __vfs_write
    vfs_write
    SyS_write
  [...]
  Showing busy workqueues and worker pools:
  [...]
  workqueue mm_percpu_wq: flags=0xc
    pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=0/0
      delayed: drain_local_pages_wq, vmstat_update
    pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=0/0
      delayed: drain_local_pages_wq BAR(1703), vmstat_update

Tetsuo has properly noted that mm_percpu_wq is created as WQ_FREEZABLE
so it is frozen this early during resume so we are effectively
deadlocked.  Fix this by dropping WQ_FREEZABLE when creating
mm_percpu_wq.  We really want to have it operational all the time.

Fixes: ce612879dd ("mm: move pcp and lru-pcp draining into single wq")
Reported-and-tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Debugged-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-04-19 15:53:48 -07:00
Michal Hocko
ce612879dd mm: move pcp and lru-pcp draining into single wq 
We currently have 2 specific WQ_RECLAIM workqueues in the mm code.
vmstat_wq for updating pcp stats and lru_add_drain_wq dedicated to drain
per cpu lru caches.  This seems more than necessary because both can run
on a single WQ.  Both do not block on locks requiring a memory
allocation nor perform any allocations themselves.  We will save one
rescuer thread this way.

On the other hand drain_all_pages() queues work on the system wq which
doesn't have rescuer and so this depend on memory allocation (when all
workers are stuck allocating and new ones cannot be created).

Initially we thought this would be more of a theoretical problem but
Hugh Dickins has reported:

: 4.11-rc has been giving me hangs after hours of swapping load.  At
: first they looked like memory leaks ("fork: Cannot allocate memory");
: but for no good reason I happened to do "cat /proc/sys/vm/stat_refresh"
: before looking at /proc/meminfo one time, and the stat_refresh stuck
: in D state, waiting for completion of flush_work like many kworkers.
: kthreadd waiting for completion of flush_work in drain_all_pages().

This worker should be using WQ_RECLAIM as well in order to guarantee a
forward progress.  We can reuse the same one as for lru draining and
vmstat.

Link: http://lkml.kernel.org/r/20170307131751.24936-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Tested-by: Yang Li <pku.leo@gmail.com>
Tested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-04-08 00:47:49 -07:00
Michal Hocko
597b7305dd mm: move mm_percpu_wq initialization earlier 
Yang Li has reported that drain_all_pages triggers a WARN_ON which means
that this function is called earlier than the mm_percpu_wq is
initialized on arm64 with CMA configured:

  WARNING: CPU: 2 PID: 1 at mm/page_alloc.c:2423 drain_all_pages+0x244/0x25c
  Modules linked in:
  CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.11.0-rc1-next-20170310-00027-g64dfbc5 #127
  Hardware name: Freescale Layerscape 2088A RDB Board (DT)
  task: ffffffc07c4a6d00 task.stack: ffffffc07c4a8000
  PC is at drain_all_pages+0x244/0x25c
  LR is at start_isolate_page_range+0x14c/0x1f0
  [...]
   drain_all_pages+0x244/0x25c
   start_isolate_page_range+0x14c/0x1f0
   alloc_contig_range+0xec/0x354
   cma_alloc+0x100/0x1fc
   dma_alloc_from_contiguous+0x3c/0x44
   atomic_pool_init+0x7c/0x208
   arm64_dma_init+0x44/0x4c
   do_one_initcall+0x38/0x128
   kernel_init_freeable+0x1a0/0x240
   kernel_init+0x10/0xfc
   ret_from_fork+0x10/0x20

Fix this by moving the whole setup_vmstat which is an initcall right now
to init_mm_internals which will be called right after the WQ subsystem
is initialized.

Link: http://lkml.kernel.org/r/20170315164021.28532-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Yang Li <pku.leo@gmail.com>
Tested-by: Yang Li <pku.leo@gmail.com>
Tested-by: Xiaolong Ye <xiaolong.ye@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-03-31 17:13:30 -07:00
Yisheng Xie
ce9311cf95 mm/vmstats: add thp_split_pud event for clarity 
We added support for PUD-sized transparent hugepages, however we count
the event "thp split pud" into thp_split_pmd event.

To separate the event count of thp split pud from pmd, add a new event
named thp_split_pud.

Link: http://lkml.kernel.org/r/1488282380-5076-1-git-send-email-xieyisheng1@huawei.com
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-03-09 17:01:10 -08:00
David Rientjes
7f354a548d mm, compaction: add vmstats for kcompactd work 
A "compact_daemon_wake" vmstat exists that represents the number of
times kcompactd has woken up.  This doesn't represent how much work it
actually did, though.

It's useful to understand how much compaction work is being done by
kcompactd versus other methods such as direct compaction and explicitly
triggered per-node (or system) compaction.

This adds two new vmstats: "compact_daemon_migrate_scanned" and
"compact_daemon_free_scanned" to represent the number of pages kcompactd
has scanned as part of its migration scanner and freeing scanner,
respectively.

These values are still accounted for in the general
"compact_migrate_scanned" and "compact_free_scanned" for compatibility.

It could be argued that explicitly triggered compaction could also be
tracked separately, and that could be added if others find it useful.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1612071749390.69852@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2017-02-22 16:41:29 -08:00
Sebastian Andrzej Siewior
5438da977f mm/vmstat: Convert to hotplug state machine 
Install the callbacks via the state machine, but do not invoke them as we
can initialize the node state without calling the callbacks on all online
CPUs.

start_shepherd_timer() is now called outside the get_online_cpus() block
which is safe as it only operates on cpu possible mask.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Cc: rt@linutronix.de
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/20161129145221.ffc3kg3hd7lxiwj6@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
 2016-12-02 00:52:35 +01:00
Sebastian Andrzej Siewior
4c501327b4 mm/vmstat: Avoid on each online CPU loops 
Both iterations over online cpus can be replaced by the proper node
specific functions.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: linux-mm@kvack.org
Cc: rt@linutronix.de
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/20161129145113.fn3lw5aazjjvdrr3@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
 2016-12-02 00:52:35 +01:00
Sebastian Andrzej Siewior
76f290935b mm/vmstat: Drop get_online_cpus() from init_cpu_node_state/vmstat_cpu_dead() 
Both functions are called with protection against cpu hotplug already so
*_online_cpus() could be dropped.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: linux-mm@kvack.org
Cc: rt@linutronix.de
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/20161126231350.10321-8-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
 2016-12-02 00:52:35 +01:00
Joe Perches
75ba1d07fd seq/proc: modify seq_put_decimal_[u]ll to take a const char *, not char 
Allow some seq_puts removals by taking a string instead of a single
char.

[akpm@linux-foundation.org: update vmstat_show(), per Joe]
Link: http://lkml.kernel.org/r/667e1cf3d436de91a5698170a1e98d882905e956.1470704995.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Joe Perches <joe@perches.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-10-07 18:46:30 -07:00
Alexey Dobriyan
68ba0326b4 proc: much faster /proc/vmstat 
Every current KDE system has process named ksysguardd polling files
below once in several seconds:

	$ strace -e trace=open -p $(pidof ksysguardd)
	Process 1812 attached
	open("/etc/mtab", O_RDONLY|O_CLOEXEC)   = 8
	open("/etc/mtab", O_RDONLY|O_CLOEXEC)   = 8
	open("/proc/net/dev", O_RDONLY)         = 8
	open("/proc/net/wireless", O_RDONLY)    = -1 ENOENT (No such file or directory)
	open("/proc/stat", O_RDONLY)            = 8
	open("/proc/vmstat", O_RDONLY)          = 8

Hell knows what it is doing but speed up reading /proc/vmstat by 33%!

Benchmark is open+read+close 1.000.000 times.

			BEFORE
$ perf stat -r 10 taskset -c 3 ./proc-vmstat

 Performance counter stats for 'taskset -c 3 ./proc-vmstat' (10 runs):

      13146.768464      task-clock (msec)         #    0.960 CPUs utilized            ( +-  0.60% )
                15      context-switches          #    0.001 K/sec                    ( +-  1.41% )
                 1      cpu-migrations            #    0.000 K/sec                    ( +- 11.11% )
               104      page-faults               #    0.008 K/sec                    ( +-  0.57% )
    45,489,799,349      cycles                    #    3.460 GHz                      ( +-  0.03% )
     9,970,175,743      stalled-cycles-frontend   #   21.92% frontend cycles idle     ( +-  0.10% )
     2,800,298,015      stalled-cycles-backend    #   6.16% backend cycles idle       ( +-  0.32% )
    79,241,190,850      instructions              #    1.74  insn per cycle
                                                  #    0.13  stalled cycles per insn  ( +-  0.00% )
    17,616,096,146      branches                  # 1339.956 M/sec                    ( +-  0.00% )
       176,106,232      branch-misses             #    1.00% of all branches          ( +-  0.18% )

      13.691078109 seconds time elapsed                                          ( +-  0.03% )
      ^^^^^^^^^^^^

			AFTER
$ perf stat -r 10 taskset -c 3 ./proc-vmstat

 Performance counter stats for 'taskset -c 3 ./proc-vmstat' (10 runs):

       8688.353749      task-clock (msec)         #    0.950 CPUs utilized            ( +-  1.25% )
                10      context-switches          #    0.001 K/sec                    ( +-  2.13% )
                 1      cpu-migrations            #    0.000 K/sec
               104      page-faults               #    0.012 K/sec                    ( +-  0.56% )
    30,384,010,730      cycles                    #    3.497 GHz                      ( +-  0.07% )
    12,296,259,407      stalled-cycles-frontend   #   40.47% frontend cycles idle     ( +-  0.13% )
     3,370,668,651      stalled-cycles-backend    #  11.09% backend cycles idle       ( +-  0.69% )
    28,969,052,879      instructions              #    0.95  insn per cycle
                                                  #    0.42  stalled cycles per insn  ( +-  0.01% )
     6,308,245,891      branches                  #  726.058 M/sec                    ( +-  0.00% )
       214,685,502      branch-misses             #    3.40% of all branches          ( +-  0.26% )

       9.146081052 seconds time elapsed                                          ( +-  0.07% )
       ^^^^^^^^^^^

vsnprintf() is slow because:

1. format_decode() is busy looking for format specifier: 2 branches
   per character (not in this case, but in others)

2. approximately million branches while parsing format mini language
   and everywhere

3.  just look at what string() does /proc/vmstat is good case because
   most of its content are strings

Link: http://lkml.kernel.org/r/20160806125455.GA1187@p183.telecom.by
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-10-07 18:46:30 -07:00
Tim Chen
03e86dba5b cpu: fix node state for whether it contains CPU 
In current kernel code, we only call node_set_state(cpu_to_node(cpu),
N_CPU) when a cpu is hot plugged.  But we do not set the node state for
N_CPU when the cpus are brought online during boot.

So this could lead to failure when we check to see if a node contains
cpu with node_state(node_id, N_CPU).

One use case is in the node_reclaime function:

        /*
         * Only run node reclaim on the local node or on nodes that do
         * not
         * have associated processors. This will favor the local
         * processor
         * over remote processors and spread off node memory allocations
         * as wide as possible.
         */
        if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id !=
                numa_node_id())
                return NODE_RECLAIM_NOSCAN;

I instrumented the kernel to call this function after boot and it always
returns 0 on a x86 desktop machine until I apply the attached patch.

   int num_cpu_node(void)
   {
       int i, nr_cpu_nodes = 0;

       for_each_node(i) {
               if (node_state(i, N_CPU))
                       ++ nr_cpu_nodes;
       }

       return nr_cpu_nodes;
   }

Fix this by checking each node for online CPU when we initialize
vmstat that's responsible for maintaining node state.

Link: http://lkml.kernel.org/r/20160829175922.GA21775@linux.intel.com
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: <Huang@linux.intel.com>
Cc: Ying <ying.huang@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-10-07 18:46:28 -07:00
Joonsoo Kim
e2f612e673 mm/page_owner: move page_owner specific function to page_owner.c 
There is no reason that page_owner specific function resides on
vmstat.c.

Link: http://lkml.kernel.org/r/1471315879-32294-4-git-send-email-iamjoonsoo.kim@lge.com
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-10-07 18:46:27 -07:00
Mel Gorman
5a1c84b404 mm: remove reclaim and compaction retry approximations 
If per-zone LRU accounting is available then there is no point
approximating whether reclaim and compaction should retry based on pgdat
statistics.  This is effectively a revert of "mm, vmstat: remove zone
and node double accounting by approximating retries" with the difference
that inactive/active stats are still available.  This preserves the
history of why the approximation was retried and why it had to be
reverted to handle OOM kills on 32-bit systems.

Link: http://lkml.kernel.org/r/1469110261-7365-4-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Minchan Kim
71c799f498 mm: add per-zone lru list stat 
When I did stress test with hackbench, I got OOM message frequently
which didn't ever happen in zone-lru.

  gfp_mask=0x26004c0(GFP_KERNEL|__GFP_REPEAT|__GFP_NOTRACK), order=0
  ..
  ..
   __alloc_pages_nodemask+0xe52/0xe60
   ? new_slab+0x39c/0x3b0
   new_slab+0x39c/0x3b0
   ___slab_alloc.constprop.87+0x6da/0x840
   ? __alloc_skb+0x3c/0x260
   ? _raw_spin_unlock_irq+0x27/0x60
   ? trace_hardirqs_on_caller+0xec/0x1b0
   ? finish_task_switch+0xa6/0x220
   ? poll_select_copy_remaining+0x140/0x140
   __slab_alloc.isra.81.constprop.86+0x40/0x6d
   ? __alloc_skb+0x3c/0x260
   kmem_cache_alloc+0x22c/0x260
   ? __alloc_skb+0x3c/0x260
   __alloc_skb+0x3c/0x260
   alloc_skb_with_frags+0x4e/0x1a0
   sock_alloc_send_pskb+0x16a/0x1b0
   ? wait_for_unix_gc+0x31/0x90
   ? alloc_set_pte+0x2ad/0x310
   unix_stream_sendmsg+0x28d/0x340
   sock_sendmsg+0x2d/0x40
   sock_write_iter+0x6c/0xc0
   __vfs_write+0xc0/0x120
   vfs_write+0x9b/0x1a0
   ? __might_fault+0x49/0xa0
   SyS_write+0x44/0x90
   do_fast_syscall_32+0xa6/0x1e0
   sysenter_past_esp+0x45/0x74

  Mem-Info:
  active_anon:104698 inactive_anon:105791 isolated_anon:192
   active_file:433 inactive_file:283 isolated_file:22
   unevictable:0 dirty:0 writeback:296 unstable:0
   slab_reclaimable:6389 slab_unreclaimable:78927
   mapped:474 shmem:0 pagetables:101426 bounce:0
   free:10518 free_pcp:334 free_cma:0
  Node 0 active_anon:418792kB inactive_anon:423164kB active_file:1732kB inactive_file:1132kB unevictable:0kB isolated(anon):768kB isolated(file):88kB mapped:1896kB dirty:0kB writeback:1184kB shmem:0kB writeback_tmp:0kB unstable:0kB pages_scanned:1478632 all_unreclaimable? yes
  DMA free:3304kB min:68kB low:84kB high:100kB present:15992kB managed:15916kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:4088kB kernel_stack:0kB pagetables:2480kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
  lowmem_reserve[]: 0 809 1965 1965
  Normal free:3436kB min:3604kB low:4504kB high:5404kB present:897016kB managed:858460kB mlocked:0kB slab_reclaimable:25556kB slab_unreclaimable:311712kB kernel_stack:164608kB pagetables:30844kB bounce:0kB free_pcp:620kB local_pcp:104kB free_cma:0kB
  lowmem_reserve[]: 0 0 9247 9247
  HighMem free:33808kB min:512kB low:1796kB high:3080kB present:1183736kB managed:1183736kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:372252kB bounce:0kB free_pcp:428kB local_pcp:72kB free_cma:0kB
  lowmem_reserve[]: 0 0 0 0
  DMA: 2*4kB (UM) 2*8kB (UM) 0*16kB 1*32kB (U) 1*64kB (U) 2*128kB (UM) 1*256kB (U) 1*512kB (M) 0*1024kB 1*2048kB (U) 0*4096kB = 3192kB
  Normal: 33*4kB (MH) 79*8kB (ME) 11*16kB (M) 4*32kB (M) 2*64kB (ME) 2*128kB (EH) 7*256kB (EH) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3244kB
  HighMem: 2590*4kB (UM) 1568*8kB (UM) 491*16kB (UM) 60*32kB (UM) 6*64kB (M) 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 33064kB
  Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB
  25121 total pagecache pages
  24160 pages in swap cache
  Swap cache stats: add 86371, delete 62211, find 42865/60187
  Free swap  = 4015560kB
  Total swap = 4192252kB
  524186 pages RAM
  295934 pages HighMem/MovableOnly
  9658 pages reserved
  0 pages cma reserved

The order-0 allocation for normal zone failed while there are a lot of
reclaimable memory(i.e., anonymous memory with free swap).  I wanted to
analyze the problem but it was hard because we removed per-zone lru stat
so I couldn't know how many of anonymous memory there are in normal/dma
zone.

When we investigate OOM problem, reclaimable memory count is crucial
stat to find a problem.  Without it, it's hard to parse the OOM message
so I believe we should keep it.

With per-zone lru stat,

  gfp_mask=0x26004c0(GFP_KERNEL|__GFP_REPEAT|__GFP_NOTRACK), order=0
  Mem-Info:
  active_anon:101103 inactive_anon:102219 isolated_anon:0
   active_file:503 inactive_file:544 isolated_file:0
   unevictable:0 dirty:0 writeback:34 unstable:0
   slab_reclaimable:6298 slab_unreclaimable:74669
   mapped:863 shmem:0 pagetables:100998 bounce:0
   free:23573 free_pcp:1861 free_cma:0
  Node 0 active_anon:404412kB inactive_anon:409040kB active_file:2012kB inactive_file:2176kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:3452kB dirty:0kB writeback:136kB shmem:0kB writeback_tmp:0kB unstable:0kB pages_scanned:1320845 all_unreclaimable? yes
  DMA free:3296kB min:68kB low:84kB high:100kB active_anon:5540kB inactive_anon:0kB active_file:0kB inactive_file:0kB present:15992kB managed:15916kB mlocked:0kB slab_reclaimable:248kB slab_unreclaimable:2628kB kernel_stack:792kB pagetables:2316kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
  lowmem_reserve[]: 0 809 1965 1965
  Normal free:3600kB min:3604kB low:4504kB high:5404kB active_anon:86304kB inactive_anon:0kB active_file:160kB inactive_file:376kB present:897016kB managed:858524kB mlocked:0kB slab_reclaimable:24944kB slab_unreclaimable:296048kB kernel_stack:163832kB pagetables:35892kB bounce:0kB free_pcp:3076kB local_pcp:656kB free_cma:0kB
  lowmem_reserve[]: 0 0 9247 9247
  HighMem free:86156kB min:512kB low:1796kB high:3080kB active_anon:312852kB inactive_anon:410024kB active_file:1924kB inactive_file:2012kB present:1183736kB managed:1183736kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:365784kB bounce:0kB free_pcp:3868kB local_pcp:720kB free_cma:0kB
  lowmem_reserve[]: 0 0 0 0
  DMA: 8*4kB (UM) 8*8kB (UM) 4*16kB (M) 2*32kB (UM) 2*64kB (UM) 1*128kB (M) 3*256kB (UME) 2*512kB (UE) 1*1024kB (E) 0*2048kB 0*4096kB = 3296kB
  Normal: 240*4kB (UME) 160*8kB (UME) 23*16kB (ME) 3*32kB (UE) 3*64kB (UME) 2*128kB (ME) 1*256kB (U) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3408kB
  HighMem: 10942*4kB (UM) 3102*8kB (UM) 866*16kB (UM) 76*32kB (UM) 11*64kB (UM) 4*128kB (UM) 1*256kB (M) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 86344kB
  Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB
  54409 total pagecache pages
  53215 pages in swap cache
  Swap cache stats: add 300982, delete 247765, find 157978/226539
  Free swap  = 3803244kB
  Total swap = 4192252kB
  524186 pages RAM
  295934 pages HighMem/MovableOnly
  9642 pages reserved
  0 pages cma reserved

With that, we can see normal zone has a 86M reclaimable memory so we can
know something goes wrong(I will fix the problem in next patch) in
reclaim.

[mgorman@techsingularity.net: rename zone LRU stats in /proc/vmstat]
 Link: http://lkml.kernel.org/r/20160725072300.GK10438@techsingularity.net
Link: http://lkml.kernel.org/r/1469110261-7365-2-git-send-email-mgorman@techsingularity.net
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Mel Gorman
bca6759258 mm, vmstat: remove zone and node double accounting by approximating retries 
The number of LRU pages, dirty pages and writeback pages must be
accounted for on both zones and nodes because of the reclaim retry
logic, compaction retry logic and highmem calculations all depending on
per-zone stats.

Many lowmem allocations are immune from OOM kill due to a check in
__alloc_pages_may_oom for (ac->high_zoneidx < ZONE_NORMAL) since commit
03668b3ceb ("oom: avoid oom killer for lowmem allocations").  The
exception is costly high-order allocations or allocations that cannot
fail.  If the __alloc_pages_may_oom avoids OOM-kill for low-order lowmem
allocations then it would fall through to __alloc_pages_direct_compact.

This patch will blindly retry reclaim for zone-constrained allocations
in should_reclaim_retry up to MAX_RECLAIM_RETRIES.  This is not ideal
but without per-zone stats there are not many alternatives.  The impact
it that zone-constrained allocations may delay before considering the
OOM killer.

As there is no guarantee enough memory can ever be freed to satisfy
compaction, this patch avoids retrying compaction for zone-contrained
allocations.

In combination, that means that the per-node stats can be used when
deciding whether to continue reclaim using a rough approximation.  While
it is possible this will make the wrong decision on occasion, it will
not infinite loop as the number of reclaim attempts is capped by
MAX_RECLAIM_RETRIES.

The final step is calculating the number of dirtyable highmem pages.  As
those calculations only care about the global count of file pages in
highmem.  This patch uses a global counter used instead of per-zone
stats as it is sufficient.

In combination, this allows the per-zone LRU and dirty state counters to
be removed.

[mgorman@techsingularity.net: fix acct_highmem_file_pages()]
  Link: http://lkml.kernel.org/r/1468853426-12858-4-git-send-email-mgorman@techsingularity.netLink: http://lkml.kernel.org/r/1467970510-21195-35-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Suggested by: Michal Hocko <mhocko@kernel.org>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Mel Gorman
e2ecc8a79e mm, vmstat: print node-based stats in zoneinfo file 
There are a number of stats that were previously accessible via zoneinfo
that are now invisible.  While it is possible to create a new file for
the node stats, this may be missed by users.  Instead this patch prints
the stats under the first populated zone in /proc/zoneinfo.

Link: http://lkml.kernel.org/r/1467970510-21195-34-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Mel Gorman
7cc30fcfd2 mm: vmstat: account per-zone stalls and pages skipped during reclaim 
The vmstat allocstall was fairly useful in the general sense but
node-based LRUs change that.  It's important to know if a stall was for
an address-limited allocation request as this will require skipping
pages from other zones.  This patch adds pgstall_* counters to replace
allocstall.  The sum of the counters will equal the old allocstall so it
can be trivially recalculated.  A high number of address-limited
allocation requests may result in a lot of useless LRU scanning for
suitable pages.

As address-limited allocations require pages to be skipped, it's
important to know how much useless LRU scanning took place so this patch
adds pgskip* counters.  This yields the following model

1. The number of address-space limited stalls can be accounted for (pgstall)
2. The amount of useless work required to reclaim the data is accounted (pgskip)
3. The total number of scans is available from pgscan_kswapd and pgscan_direct
   so from that the ratio of useful to useless scans can be calculated.

[mgorman@techsingularity.net: s/pgstall/allocstall/]
  Link: http://lkml.kernel.org/r/1468404004-5085-3-git-send-email-mgorman@techsingularity.netLink: http://lkml.kernel.org/r/1467970510-21195-33-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Mel Gorman
e6cbd7f2ef mm, page_alloc: remove fair zone allocation policy 
The fair zone allocation policy interleaves allocation requests between
zones to avoid an age inversion problem whereby new pages are reclaimed
to balance a zone.  Reclaim is now node-based so this should no longer
be an issue and the fair zone allocation policy is not free.  This patch
removes it.

Link: http://lkml.kernel.org/r/1467970510-21195-30-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Mel Gorman
c4a25635b6 mm: move vmscan writes and file write accounting to the node 
As reclaim is now node-based, it follows that page write activity due to
page reclaim should also be accounted for on the node.  For consistency,
also account page writes and page dirtying on a per-node basis.

After this patch, there are a few remaining zone counters that may appear
strange but are fine.  NUMA stats are still per-zone as this is a
user-space interface that tools consume.  NR_MLOCK, NR_SLAB_*,
NR_PAGETABLE, NR_KERNEL_STACK and NR_BOUNCE are all allocations that
potentially pin low memory and cannot trivially be reclaimed on demand.
This information is still useful for debugging a page allocation failure
warning.

Link: http://lkml.kernel.org/r/1467970510-21195-21-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Mel Gorman
11fb998986 mm: move most file-based accounting to the node 
There are now a number of accounting oddities such as mapped file pages
being accounted for on the node while the total number of file pages are
accounted on the zone.  This can be coped with to some extent but it's
confusing so this patch moves the relevant file-based accounted.  Due to
throttling logic in the page allocator for reliable OOM detection, it is
still necessary to track dirty and writeback pages on a per-zone basis.

[mgorman@techsingularity.net: fix NR_ZONE_WRITE_PENDING accounting]
  Link: http://lkml.kernel.org/r/1468404004-5085-5-git-send-email-mgorman@techsingularity.net
Link: http://lkml.kernel.org/r/1467970510-21195-20-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Mel Gorman
50658e2e04 mm: move page mapped accounting to the node 
Reclaim makes decisions based on the number of pages that are mapped but
it's mixing node and zone information.  Account NR_FILE_MAPPED and
NR_ANON_PAGES pages on the node.

Link: http://lkml.kernel.org/r/1467970510-21195-18-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Mel Gorman
1e6b10857f mm, workingset: make working set detection node-aware 
Working set and refault detection is still zone-based, fix it.

Link: http://lkml.kernel.org/r/1467970510-21195-16-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Mel Gorman
599d0c954f mm, vmscan: move LRU lists to node 
This moves the LRU lists from the zone to the node and related data such
as counters, tracing, congestion tracking and writeback tracking.

Unfortunately, due to reclaim and compaction retry logic, it is
necessary to account for the number of LRU pages on both zone and node
logic.  Most reclaim logic is based on the node counters but the retry
logic uses the zone counters which do not distinguish inactive and
active sizes.  It would be possible to leave the LRU counters on a
per-zone basis but it's a heavier calculation across multiple cache
lines that is much more frequent than the retry checks.

Other than the LRU counters, this is mostly a mechanical patch but note
that it introduces a number of anomalies.  For example, the scans are
per-zone but using per-node counters.  We also mark a node as congested
when a zone is congested.  This causes weird problems that are fixed
later but is easier to review.

In the event that there is excessive overhead on 32-bit systems due to
the nodes being on LRU then there are two potential solutions

1. Long-term isolation of highmem pages when reclaim is lowmem

   When pages are skipped, they are immediately added back onto the LRU
   list. If lowmem reclaim persisted for long periods of time, the same
   highmem pages get continually scanned. The idea would be that lowmem
   keeps those pages on a separate list until a reclaim for highmem pages
   arrives that splices the highmem pages back onto the LRU. It potentially
   could be implemented similar to the UNEVICTABLE list.

   That would reduce the skip rate with the potential corner case is that
   highmem pages have to be scanned and reclaimed to free lowmem slab pages.

2. Linear scan lowmem pages if the initial LRU shrink fails

   This will break LRU ordering but may be preferable and faster during
   memory pressure than skipping LRU pages.

Link: http://lkml.kernel.org/r/1467970510-21195-4-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Mel Gorman
75ef718405 mm, vmstat: add infrastructure for per-node vmstats 
Patchset: "Move LRU page reclaim from zones to nodes v9"

This series moves LRUs from the zones to the node.  While this is a
current rebase, the test results were based on mmotm as of June 23rd.
Conceptually, this series is simple but there are a lot of details.
Some of the broad motivations for this are;

1. The residency of a page partially depends on what zone the page was
   allocated from.  This is partially combatted by the fair zone allocation
   policy but that is a partial solution that introduces overhead in the
   page allocator paths.

2. Currently, reclaim on node 0 behaves slightly different to node 1. For
   example, direct reclaim scans in zonelist order and reclaims even if
   the zone is over the high watermark regardless of the age of pages
   in that LRU. Kswapd on the other hand starts reclaim on the highest
   unbalanced zone. A difference in distribution of file/anon pages due
   to when they were allocated results can result in a difference in
   again. While the fair zone allocation policy mitigates some of the
   problems here, the page reclaim results on a multi-zone node will
   always be different to a single-zone node.
   it was scheduled on as a result.

3. kswapd and the page allocator scan zones in the opposite order to
   avoid interfering with each other but it's sensitive to timing.  This
   mitigates the page allocator using pages that were allocated very recently
   in the ideal case but it's sensitive to timing. When kswapd is allocating
   from lower zones then it's great but during the rebalancing of the highest
   zone, the page allocator and kswapd interfere with each other. It's worse
   if the highest zone is small and difficult to balance.

4. slab shrinkers are node-based which makes it harder to identify the exact
   relationship between slab reclaim and LRU reclaim.

The reason we have zone-based reclaim is that we used to have
large highmem zones in common configurations and it was necessary
to quickly find ZONE_NORMAL pages for reclaim. Today, this is much
less of a concern as machines with lots of memory will (or should) use
64-bit kernels. Combinations of 32-bit hardware and 64-bit hardware are
rare. Machines that do use highmem should have relatively low highmem:lowmem
ratios than we worried about in the past.

Conceptually, moving to node LRUs should be easier to understand. The
page allocator plays fewer tricks to game reclaim and reclaim behaves
similarly on all nodes.

The series has been tested on a 16 core UMA machine and a 2-socket 48
core NUMA machine. The UMA results are presented in most cases as the NUMA
machine behaved similarly.

pagealloc
---------

This is a microbenchmark that shows the benefit of removing the fair zone
allocation policy. It was tested uip to order-4 but only orders 0 and 1 are
shown as the other orders were comparable.

                                           4.7.0-rc4                  4.7.0-rc4
                                      mmotm-20160623                 nodelru-v9
Min      total-odr0-1               490.00 (  0.00%)           457.00 (  6.73%)
Min      total-odr0-2               347.00 (  0.00%)           329.00 (  5.19%)
Min      total-odr0-4               288.00 (  0.00%)           273.00 (  5.21%)
Min      total-odr0-8               251.00 (  0.00%)           239.00 (  4.78%)
Min      total-odr0-16              234.00 (  0.00%)           222.00 (  5.13%)
Min      total-odr0-32              223.00 (  0.00%)           211.00 (  5.38%)
Min      total-odr0-64              217.00 (  0.00%)           208.00 (  4.15%)
Min      total-odr0-128             214.00 (  0.00%)           204.00 (  4.67%)
Min      total-odr0-256             250.00 (  0.00%)           230.00 (  8.00%)
Min      total-odr0-512             271.00 (  0.00%)           269.00 (  0.74%)
Min      total-odr0-1024            291.00 (  0.00%)           282.00 (  3.09%)
Min      total-odr0-2048            303.00 (  0.00%)           296.00 (  2.31%)
Min      total-odr0-4096            311.00 (  0.00%)           309.00 (  0.64%)
Min      total-odr0-8192            316.00 (  0.00%)           314.00 (  0.63%)
Min      total-odr0-16384           317.00 (  0.00%)           315.00 (  0.63%)
Min      total-odr1-1               742.00 (  0.00%)           712.00 (  4.04%)
Min      total-odr1-2               562.00 (  0.00%)           530.00 (  5.69%)
Min      total-odr1-4               457.00 (  0.00%)           433.00 (  5.25%)
Min      total-odr1-8               411.00 (  0.00%)           381.00 (  7.30%)
Min      total-odr1-16              381.00 (  0.00%)           356.00 (  6.56%)
Min      total-odr1-32              372.00 (  0.00%)           346.00 (  6.99%)
Min      total-odr1-64              372.00 (  0.00%)           343.00 (  7.80%)
Min      total-odr1-128             375.00 (  0.00%)           351.00 (  6.40%)
Min      total-odr1-256             379.00 (  0.00%)           351.00 (  7.39%)
Min      total-odr1-512             385.00 (  0.00%)           355.00 (  7.79%)
Min      total-odr1-1024            386.00 (  0.00%)           358.00 (  7.25%)
Min      total-odr1-2048            390.00 (  0.00%)           362.00 (  7.18%)
Min      total-odr1-4096            390.00 (  0.00%)           362.00 (  7.18%)
Min      total-odr1-8192            388.00 (  0.00%)           363.00 (  6.44%)

This shows a steady improvement throughout. The primary benefit is from
reduced system CPU usage which is obvious from the overall times;

           4.7.0-rc4   4.7.0-rc4
        mmotm-20160623nodelru-v8
User          189.19      191.80
System       2604.45     2533.56
Elapsed      2855.30     2786.39

The vmstats also showed that the fair zone allocation policy was definitely
removed as can be seen here;

                             4.7.0-rc3   4.7.0-rc3
                         mmotm-20160623 nodelru-v8
DMA32 allocs               28794729769           0
Normal allocs              48432501431 77227309877
Movable allocs                       0           0

tiobench on ext4
----------------

tiobench is a benchmark that artifically benefits if old pages remain resident
while new pages get reclaimed. The fair zone allocation policy mitigates this
problem so pages age fairly. While the benchmark has problems, it is important
that tiobench performance remains constant as it implies that page aging
problems that the fair zone allocation policy fixes are not re-introduced.

                                         4.7.0-rc4             4.7.0-rc4
                                    mmotm-20160623            nodelru-v9
Min      PotentialReadSpeed        89.65 (  0.00%)       90.21 (  0.62%)
Min      SeqRead-MB/sec-1          82.68 (  0.00%)       82.01 ( -0.81%)
Min      SeqRead-MB/sec-2          72.76 (  0.00%)       72.07 ( -0.95%)
Min      SeqRead-MB/sec-4          75.13 (  0.00%)       74.92 ( -0.28%)
Min      SeqRead-MB/sec-8          64.91 (  0.00%)       65.19 (  0.43%)
Min      SeqRead-MB/sec-16         62.24 (  0.00%)       62.22 ( -0.03%)
Min      RandRead-MB/sec-1          0.88 (  0.00%)        0.88 (  0.00%)
Min      RandRead-MB/sec-2          0.95 (  0.00%)        0.92 ( -3.16%)
Min      RandRead-MB/sec-4          1.43 (  0.00%)        1.34 ( -6.29%)
Min      RandRead-MB/sec-8          1.61 (  0.00%)        1.60 ( -0.62%)
Min      RandRead-MB/sec-16         1.80 (  0.00%)        1.90 (  5.56%)
Min      SeqWrite-MB/sec-1         76.41 (  0.00%)       76.85 (  0.58%)
Min      SeqWrite-MB/sec-2         74.11 (  0.00%)       73.54 ( -0.77%)
Min      SeqWrite-MB/sec-4         80.05 (  0.00%)       80.13 (  0.10%)
Min      SeqWrite-MB/sec-8         72.88 (  0.00%)       73.20 (  0.44%)
Min      SeqWrite-MB/sec-16        75.91 (  0.00%)       76.44 (  0.70%)
Min      RandWrite-MB/sec-1         1.18 (  0.00%)        1.14 ( -3.39%)
Min      RandWrite-MB/sec-2         1.02 (  0.00%)        1.03 (  0.98%)
Min      RandWrite-MB/sec-4         1.05 (  0.00%)        0.98 ( -6.67%)
Min      RandWrite-MB/sec-8         0.89 (  0.00%)        0.92 (  3.37%)
Min      RandWrite-MB/sec-16        0.92 (  0.00%)        0.93 (  1.09%)

           4.7.0-rc4   4.7.0-rc4
        mmotm-20160623 approx-v9
User          645.72      525.90
System        403.85      331.75
Elapsed      6795.36     6783.67

This shows that the series has little or not impact on tiobench which is
desirable and a reduction in system CPU usage. It indicates that the fair
zone allocation policy was removed in a manner that didn't reintroduce
one class of page aging bug. There were only minor differences in overall
reclaim activity

                             4.7.0-rc4   4.7.0-rc4
                          mmotm-20160623nodelru-v8
Minor Faults                    645838      647465
Major Faults                       573         640
Swap Ins                             0           0
Swap Outs                            0           0
DMA allocs                           0           0
DMA32 allocs                  46041453    44190646
Normal allocs                 78053072    79887245
Movable allocs                       0           0
Allocation stalls                   24          67
Stall zone DMA                       0           0
Stall zone DMA32                     0           0
Stall zone Normal                    0           2
Stall zone HighMem                   0           0
Stall zone Movable                   0          65
Direct pages scanned             10969       30609
Kswapd pages scanned          93375144    93492094
Kswapd pages reclaimed        93372243    93489370
Direct pages reclaimed           10969       30609
Kswapd efficiency                  99%         99%
Kswapd velocity              13741.015   13781.934
Direct efficiency                 100%        100%
Direct velocity                  1.614       4.512
Percentage direct scans             0%          0%

kswapd activity was roughly comparable. There were differences in direct
reclaim activity but negligible in the context of the overall workload
(velocity of 4 pages per second with the patches applied, 1.6 pages per
second in the baseline kernel).

pgbench read-only large configuration on ext4
---------------------------------------------

pgbench is a database benchmark that can be sensitive to page reclaim
decisions. This also checks if removing the fair zone allocation policy
is safe

pgbench Transactions
                        4.7.0-rc4             4.7.0-rc4
                   mmotm-20160623            nodelru-v8
Hmean    1       188.26 (  0.00%)      189.78 (  0.81%)
Hmean    5       330.66 (  0.00%)      328.69 ( -0.59%)
Hmean    12      370.32 (  0.00%)      380.72 (  2.81%)
Hmean    21      368.89 (  0.00%)      369.00 (  0.03%)
Hmean    30      382.14 (  0.00%)      360.89 ( -5.56%)
Hmean    32      428.87 (  0.00%)      432.96 (  0.95%)

Negligible differences again. As with tiobench, overall reclaim activity
was comparable.

bonnie++ on ext4
----------------

No interesting performance difference, negligible differences on reclaim
stats.

paralleldd on ext4
------------------

This workload uses varying numbers of dd instances to read large amounts of
data from disk.

                               4.7.0-rc3             4.7.0-rc3
                          mmotm-20160623            nodelru-v9
Amean    Elapsd-1       186.04 (  0.00%)      189.41 ( -1.82%)
Amean    Elapsd-3       192.27 (  0.00%)      191.38 (  0.46%)
Amean    Elapsd-5       185.21 (  0.00%)      182.75 (  1.33%)
Amean    Elapsd-7       183.71 (  0.00%)      182.11 (  0.87%)
Amean    Elapsd-12      180.96 (  0.00%)      181.58 ( -0.35%)
Amean    Elapsd-16      181.36 (  0.00%)      183.72 ( -1.30%)

           4.7.0-rc4   4.7.0-rc4
        mmotm-20160623 nodelru-v9
User         1548.01     1552.44
System       8609.71     8515.08
Elapsed      3587.10     3594.54

There is little or no change in performance but some drop in system CPU usage.

                             4.7.0-rc3   4.7.0-rc3
                        mmotm-20160623  nodelru-v9
Minor Faults                    362662      367360
Major Faults                      1204        1143
Swap Ins                            22           0
Swap Outs                         2855        1029
DMA allocs                           0           0
DMA32 allocs                  31409797    28837521
Normal allocs                 46611853    49231282
Movable allocs                       0           0
Direct pages scanned                 0           0
Kswapd pages scanned          40845270    40869088
Kswapd pages reclaimed        40830976    40855294
Direct pages reclaimed               0           0
Kswapd efficiency                  99%         99%
Kswapd velocity              11386.711   11369.769
Direct efficiency                 100%        100%
Direct velocity                  0.000       0.000
Percentage direct scans             0%          0%
Page writes by reclaim            2855        1029
Page writes file                     0           0
Page writes anon                  2855        1029
Page reclaim immediate             771        1628
Sector Reads                 293312636   293536360
Sector Writes                 18213568    18186480
Page rescued immediate               0           0
Slabs scanned                   128257      132747
Direct inode steals                181          56
Kswapd inode steals                 59        1131

It basically shows that kswapd was active at roughly the same rate in
both kernels. There was also comparable slab scanning activity and direct
reclaim was avoided in both cases. There appears to be a large difference
in numbers of inodes reclaimed but the workload has few active inodes and
is likely a timing artifact.

stutter
-------

stutter simulates a simple workload. One part uses a lot of anonymous
memory, a second measures mmap latency and a third copies a large file.
The primary metric is checking for mmap latency.

stutter
                             4.7.0-rc4             4.7.0-rc4
                        mmotm-20160623            nodelru-v8
Min         mmap     16.6283 (  0.00%)     13.4258 ( 19.26%)
1st-qrtle   mmap     54.7570 (  0.00%)     34.9121 ( 36.24%)
2nd-qrtle   mmap     57.3163 (  0.00%)     46.1147 ( 19.54%)
3rd-qrtle   mmap     58.9976 (  0.00%)     47.1882 ( 20.02%)
Max-90%     mmap     59.7433 (  0.00%)     47.4453 ( 20.58%)
Max-93%     mmap     60.1298 (  0.00%)     47.6037 ( 20.83%)
Max-95%     mmap     73.4112 (  0.00%)     82.8719 (-12.89%)
Max-99%     mmap     92.8542 (  0.00%)     88.8870 (  4.27%)
Max         mmap   1440.6569 (  0.00%)    121.4201 ( 91.57%)
Mean        mmap     59.3493 (  0.00%)     42.2991 ( 28.73%)
Best99%Mean mmap     57.2121 (  0.00%)     41.8207 ( 26.90%)
Best95%Mean mmap     55.9113 (  0.00%)     39.9620 ( 28.53%)
Best90%Mean mmap     55.6199 (  0.00%)     39.3124 ( 29.32%)
Best50%Mean mmap     53.2183 (  0.00%)     33.1307 ( 37.75%)
Best10%Mean mmap     45.9842 (  0.00%)     20.4040 ( 55.63%)
Best5%Mean  mmap     43.2256 (  0.00%)     17.9654 ( 58.44%)
Best1%Mean  mmap     32.9388 (  0.00%)     16.6875 ( 49.34%)

This shows a number of improvements with the worst-case outlier greatly
improved.

Some of the vmstats are interesting

                             4.7.0-rc4   4.7.0-rc4
                          mmotm-20160623nodelru-v8
Swap Ins                           163         502
Swap Outs                            0           0
DMA allocs                           0           0
DMA32 allocs                 618719206  1381662383
Normal allocs                891235743   564138421
Movable allocs                       0           0
Allocation stalls                 2603           1
Direct pages scanned            216787           2
Kswapd pages scanned          50719775    41778378
Kswapd pages reclaimed        41541765    41777639
Direct pages reclaimed          209159           0
Kswapd efficiency                  81%         99%
Kswapd velocity              16859.554   14329.059
Direct efficiency                  96%          0%
Direct velocity                 72.061       0.001
Percentage direct scans             0%          0%
Page writes by reclaim         6215049           0
Page writes file               6215049           0
Page writes anon                     0           0
Page reclaim immediate           70673          90
Sector Reads                  81940800    81680456
Sector Writes                100158984    98816036
Page rescued immediate               0           0
Slabs scanned                  1366954       22683

While this is not guaranteed in all cases, this particular test showed
a large reduction in direct reclaim activity. It's also worth noting
that no page writes were issued from reclaim context.

This series is not without its hazards. There are at least three areas
that I'm concerned with even though I could not reproduce any problems in
that area.

1. Reclaim/compaction is going to be affected because the amount of reclaim is
   no longer targetted at a specific zone. Compaction works on a per-zone basis
   so there is no guarantee that reclaiming a few THP's worth page pages will
   have a positive impact on compaction success rates.

2. The Slab/LRU reclaim ratio is affected because the frequency the shrinkers
   are called is now different. This may or may not be a problem but if it
   is, it'll be because shrinkers are not called enough and some balancing
   is required.

3. The anon/file reclaim ratio may be affected. Pages about to be dirtied are
   distributed between zones and the fair zone allocation policy used to do
   something very similar for anon. The distribution is now different but not
   necessarily in any way that matters but it's still worth bearing in mind.

VM statistic counters for reclaim decisions are zone-based.  If the kernel
is to reclaim on a per-node basis then we need to track per-node
statistics but there is no infrastructure for that.  The most notable
change is that the old node_page_state is renamed to
sum_zone_node_page_state.  The new node_page_state takes a pglist_data and
uses per-node stats but none exist yet.  There is some renaming such as
vm_stat to vm_zone_stat and the addition of vm_node_stat and the renaming
of mod_state to mod_zone_state.  Otherwise, this is mostly a mechanical
patch with no functional change.  There is a lot of similarity between the
node and zone helpers which is unfortunate but there was no obvious way of
reusing the code and maintaining type safety.

Link: http://lkml.kernel.org/r/1467970510-21195-2-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-28 16:07:41 -07:00
Kirill A. Shutemov
65c453778a mm, rmap: account shmem thp pages 
Let's add ShmemHugePages and ShmemPmdMapped fields into meminfo and
smaps.  It indicates how many times we allocate and map shmem THP.

NR_ANON_TRANSPARENT_HUGEPAGES is renamed to NR_ANON_THPS.

Link: http://lkml.kernel.org/r/1466021202-61880-27-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-26 16:19:19 -07:00
Kirill A. Shutemov
95ecedcd6a thp, vmstats: add counters for huge file pages 
THP_FILE_ALLOC: how many times huge page was allocated and put page
cache.

THP_FILE_MAPPED: how many times file huge page was mapped.

Link: http://lkml.kernel.org/r/1466021202-61880-13-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-26 16:19:19 -07:00
Minchan Kim
91537fee00 mm: add NR_ZSMALLOC to vmstat 
zram is very popular for some of the embedded world (e.g., TV, mobile
phones).  On those system, zsmalloc's consumed memory size is never
trivial (one of example from real product system, total memory: 800M,
zsmalloc consumed: 150M), so we have used this out of tree patch to
monitor system memory behavior via /proc/vmstat.

With zsmalloc in vmstat, it helps in tracking down system behavior due
to memory usage.

[minchan@kernel.org: zsmalloc: follow up zsmalloc vmstat]
  Link: http://lkml.kernel.org/r/20160607091737.GC23435@bbox
[akpm@linux-foundation.org: fix build with CONFIG_ZSMALLOC=m]
Link: http://lkml.kernel.org/r/1464919731-13255-1-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Sangseok Lee <sangseok.lee@lge.com>
Cc: Chanho Min <chanho.min@lge.com>
Cc: Chan Gyun Jeong <chan.jeong@lge.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-07-26 16:19:19 -07:00
Yang Shi
f86e427197 mm: check the return value of lookup_page_ext for all call sites 
Per the discussion with Joonsoo Kim [1], we need check the return value
of lookup_page_ext() for all call sites since it might return NULL in
some cases, although it is unlikely, i.e.  memory hotplug.

Tested with ltp with "page_owner=0".

[1] http://lkml.kernel.org/r/20160519002809.GA10245@js1304-P5Q-DELUXE

[akpm@linux-foundation.org: fix build-breaking typos]
[arnd@arndb.de: fix build problems from lookup_page_ext]
  Link: http://lkml.kernel.org/r/6285269.2CksypHdYp@wuerfel
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1464023768-31025-1-git-send-email-yang.shi@linaro.org
Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-06-03 15:06:22 -07:00
Christoph Lameter
7b8da4c7f0 vmstat: get rid of the ugly cpu_stat_off variable 
The cpu_stat_off variable is unecessary since we can check if a
workqueue request is pending otherwise.  Removal of cpu_stat_off makes
it pretty easy for the vmstat shepherd to ensure that the proper things
happen.

Removing the state also removes all races related to it.  Should a
workqueue not be scheduled as needed for vmstat_update then the shepherd
will notice and schedule it as needed.  Should a workqueue be
unecessarily scheduled then the vmstat updater will disable it.

[akpm@linux-foundation.org: fix indentation, per Michal]
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1605061306460.17934@east.gentwo.org
Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <htejun@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-05-20 17:58:30 -07:00
Mel Gorman
0b423ca22f mm, page_alloc: inline pageblock lookup in page free fast paths 
The function call overhead of get_pfnblock_flags_mask() is measurable in
the page free paths.  This patch uses an inlined version that is faster.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-05-19 19:12:14 -07:00
Mel Gorman
060e74173f mm, page_alloc: inline zone_statistics 
zone_statistics has one call-site but it's a public function.  Make it
static and inline.

The performance difference on a page allocator microbenchmark is;

                                             4.6.0-rc2                  4.6.0-rc2
                                      statbranch-v1r20           statinline-v1r20
  Min      alloc-odr0-1               419.00 (  0.00%)           412.00 (  1.67%)
  Min      alloc-odr0-2               305.00 (  0.00%)           301.00 (  1.31%)
  Min      alloc-odr0-4               250.00 (  0.00%)           247.00 (  1.20%)
  Min      alloc-odr0-8               219.00 (  0.00%)           215.00 (  1.83%)
  Min      alloc-odr0-16              203.00 (  0.00%)           199.00 (  1.97%)
  Min      alloc-odr0-32              195.00 (  0.00%)           191.00 (  2.05%)
  Min      alloc-odr0-64              191.00 (  0.00%)           187.00 (  2.09%)
  Min      alloc-odr0-128             189.00 (  0.00%)           185.00 (  2.12%)
  Min      alloc-odr0-256             198.00 (  0.00%)           193.00 (  2.53%)
  Min      alloc-odr0-512             210.00 (  0.00%)           207.00 (  1.43%)
  Min      alloc-odr0-1024            216.00 (  0.00%)           213.00 (  1.39%)
  Min      alloc-odr0-2048            221.00 (  0.00%)           220.00 (  0.45%)
  Min      alloc-odr0-4096            227.00 (  0.00%)           226.00 (  0.44%)
  Min      alloc-odr0-8192            232.00 (  0.00%)           229.00 (  1.29%)
  Min      alloc-odr0-16384           232.00 (  0.00%)           229.00 (  1.29%)

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-05-19 19:12:14 -07:00
Mel Gorman
b9f00e147f mm, page_alloc: reduce branches in zone_statistics 
zone_statistics has more branches than it really needs to take an
unlikely GFP flag into account.  Reduce the number and annotate the
unlikely flag.

The performance difference on a page allocator microbenchmark is;

                                             4.6.0-rc2                  4.6.0-rc2
                                      nocompound-v1r10           statbranch-v1r10
  Min      alloc-odr0-1               417.00 (  0.00%)           419.00 ( -0.48%)
  Min      alloc-odr0-2               308.00 (  0.00%)           305.00 (  0.97%)
  Min      alloc-odr0-4               253.00 (  0.00%)           250.00 (  1.19%)
  Min      alloc-odr0-8               221.00 (  0.00%)           219.00 (  0.90%)
  Min      alloc-odr0-16              205.00 (  0.00%)           203.00 (  0.98%)
  Min      alloc-odr0-32              199.00 (  0.00%)           195.00 (  2.01%)
  Min      alloc-odr0-64              193.00 (  0.00%)           191.00 (  1.04%)
  Min      alloc-odr0-128             191.00 (  0.00%)           189.00 (  1.05%)
  Min      alloc-odr0-256             200.00 (  0.00%)           198.00 (  1.00%)
  Min      alloc-odr0-512             212.00 (  0.00%)           210.00 (  0.94%)
  Min      alloc-odr0-1024            219.00 (  0.00%)           216.00 (  1.37%)
  Min      alloc-odr0-2048            225.00 (  0.00%)           221.00 (  1.78%)
  Min      alloc-odr0-4096            231.00 (  0.00%)           227.00 (  1.73%)
  Min      alloc-odr0-8192            234.00 (  0.00%)           232.00 (  0.85%)
  Min      alloc-odr0-16384           234.00 (  0.00%)           232.00 (  0.85%)

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-05-19 19:12:14 -07:00
Hugh Dickins
52b6f46bc1 mm: /proc/sys/vm/stat_refresh to force vmstat update 
Provide /proc/sys/vm/stat_refresh to force an immediate update of
per-cpu into global vmstats: useful to avoid a sleep(2) or whatever
before checking counts when testing.  Originally added to work around a
bug which left counts stranded indefinitely on a cpu going idle (an
inaccuracy magnified when small below-batch numbers represent "huge"
amounts of memory), but I believe that bug is now fixed: nonetheless,
this is still a useful knob.

Its schedule_on_each_cpu() is probably too expensive just to fold into
reading /proc/meminfo itself: give this mode 0600 to prevent abuse.
Allow a write or a read to do the same: nothing to read, but "grep -h
Shmem /proc/sys/vm/stat_refresh /proc/meminfo" is convenient.  Oh, and
since global_page_state() itself is careful to disguise any underflow as
0, hack in an "Invalid argument" and pr_warn() if a counter is negative
after the refresh - this helped to fix a misaccounting of
NR_ISOLATED_FILE in my migration code.

But on recent kernels, I find that NR_ALLOC_BATCH and NR_PAGES_SCANNED
often go negative some of the time.  I have not yet worked out why, but
have no evidence that it's actually harmful.  Punt for the moment by
just ignoring the anomaly on those.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Yang Shi <yang.shi@linaro.org>
Cc: Ning Qu <quning@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-05-19 19:12:14 -07:00
Joonsoo Kim
e87d59f7a2 mm/vmstat: make node_page_state() handles all zones by itself 
node_page_state() manually adds statistics per each zone and returns
total value for all zones.  Whenever we add a new zone, we need to
consider this function and it's really troublesome.  Make it handle all
zones by itself.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-05-19 19:12:14 -07:00
Joonsoo Kim
a91c43c731 mm/vmstat: add zone range overlapping check 
There is a system thats node's pfns are overlapped as follows:

  -----pfn-------->
  N0 N1 N2 N0 N1 N2

Therefore, we need to care this overlapping when iterating pfn range.

There are two places in vmstat.c that iterates pfn range and they don't
consider this overlapping.  Add it.

Without this patch, above system could over count pageblock number on a
zone.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-05-19 19:12:14 -07:00
Kirill A. Shutemov
f9719a03de thp, vmstats: count deferred split events 
Count how many times we put a THP in split queue.  Currently, it happens
on partial unmap of a THP.

Rapidly growing value can indicate that an application behaves
unfriendly wrt THP: often fault in huge page and then unmap part of it.
This leads to unnecessary memory fragmentation and the application may
require tuning.

The event also can help with debugging kernel [mis-]behaviour.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-03-17 15:09:34 -07:00
Vlastimil Babka
698b1b3064 mm, compaction: introduce kcompactd 
Memory compaction can be currently performed in several contexts:

 - kswapd balancing a zone after a high-order allocation failure
 - direct compaction to satisfy a high-order allocation, including THP
   page fault attemps
 - khugepaged trying to collapse a hugepage
 - manually from /proc

The purpose of compaction is two-fold.  The obvious purpose is to
satisfy a (pending or future) high-order allocation, and is easy to
evaluate.  The other purpose is to keep overal memory fragmentation low
and help the anti-fragmentation mechanism.  The success wrt the latter
purpose is more

The current situation wrt the purposes has a few drawbacks:

 - compaction is invoked only when a high-order page or hugepage is not
   available (or manually).  This might be too late for the purposes of
   keeping memory fragmentation low.
 - direct compaction increases latency of allocations.  Again, it would
   be better if compaction was performed asynchronously to keep
   fragmentation low, before the allocation itself comes.
 - (a special case of the previous) the cost of compaction during THP
   page faults can easily offset the benefits of THP.
 - kswapd compaction appears to be complex, fragile and not working in
   some scenarios.  It could also end up compacting for a high-order
   allocation request when it should be reclaiming memory for a later
   order-0 request.

To improve the situation, we should be able to benefit from an
equivalent of kswapd, but for compaction - i.e. a background thread
which responds to fragmentation and the need for high-order allocations
(including hugepages) somewhat proactively.

One possibility is to extend the responsibilities of kswapd, which could
however complicate its design too much.  It should be better to let
kswapd handle reclaim, as order-0 allocations are often more critical
than high-order ones.

Another possibility is to extend khugepaged, but this kthread is a
single instance and tied to THP configs.

This patch goes with the option of a new set of per-node kthreads called
kcompactd, and lays the foundations, without introducing any new
tunables.  The lifecycle mimics kswapd kthreads, including the memory
hotplug hooks.

For compaction, kcompactd uses the standard compaction_suitable() and
ompact_finished() criteria and the deferred compaction functionality.
Unlike direct compaction, it uses only sync compaction, as there's no
allocation latency to minimize.

This patch doesn't yet add a call to wakeup_kcompactd.  The kswapd
compact/reclaim loop for high-order pages will be replaced by waking up
kcompactd in the next patch with the description of what's wrong with
the old approach.

Waking up of the kcompactd threads is also tied to kswapd activity and
follows these rules:
 - we don't want to affect any fastpaths, so wake up kcompactd only from
   the slowpath, as it's done for kswapd
 - if kswapd is doing reclaim, it's more important than compaction, so
   don't invoke kcompactd until kswapd goes to sleep
 - the target order used for kswapd is passed to kcompactd

Future possible future uses for kcompactd include the ability to wake up
kcompactd on demand in special situations, such as when hugepages are
not available (currently not done due to __GFP_NO_KSWAPD) or when a
fragmentation event (i.e.  __rmqueue_fallback()) occurs.  It's also
possible to perform periodic compaction with kcompactd.

[arnd@arndb.de: fix build errors with kcompactd]
[paul.gortmaker@windriver.com: don't use modular references for non modular code]
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-03-17 15:09:34 -07:00
Vlastimil Babka
7dd80b8af0 mm, page_owner: convert page_owner_inited to static key 
CONFIG_PAGE_OWNER attempts to impose negligible runtime overhead when
enabled during compilation, but not actually enabled during runtime by
boot param page_owner=on.  This overhead can be further reduced using
the static key mechanism, which this patch does.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-03-15 16:55:16 -07:00
Vlastimil Babka
60f30350fd mm, page_owner: print migratetype of page and pageblock, symbolic flags 
The information in /sys/kernel/debug/page_owner includes the migratetype
of the pageblock the page belongs to.  This is also checked against the
page's migratetype (as declared by gfp_flags during its allocation), and
the page is reported as Fallback if its migratetype differs from the
pageblock's one.  t This is somewhat misleading because in fact fallback
allocation is not the only reason why these two can differ.  It also
doesn't direcly provide the page's migratetype, although it's possible
to derive that from the gfp_flags.

It's arguably better to print both page and pageblock's migratetype and
leave the interpretation to the consumer than to suggest fallback
allocation as the only possible reason.  While at it, we can print the
migratetypes as string the same way as /proc/pagetypeinfo does, as some
of the numeric values depend on kernel configuration.  For that, this
patch moves the migratetype_names array from #ifdef CONFIG_PROC_FS part
of mm/vmstat.c to mm/page_alloc.c and exports it.

With the new format strings for flags, we can now also provide symbolic
page and gfp flags in the /sys/kernel/debug/page_owner file.  This
replaces the positional printing of page flags as single letters, which
might have looked nicer, but was limited to a subset of flags, and
required the user to remember the letters.

Example page_owner entry after the patch:

  Page allocated via order 0, mask 0x24213ca(GFP_HIGHUSER_MOVABLE|__GFP_COLD|__GFP_NOWARN|__GFP_NORETRY)
  PFN 520 type Movable Block 1 type Movable Flags 0xfffff8001006c(referenced|uptodate|lru|active|mappedtodisk)
   [<ffffffff811682c4>] __alloc_pages_nodemask+0x134/0x230
   [<ffffffff811b4058>] alloc_pages_current+0x88/0x120
   [<ffffffff8115e386>] __page_cache_alloc+0xe6/0x120
   [<ffffffff8116ba6c>] __do_page_cache_readahead+0xdc/0x240
   [<ffffffff8116bd05>] ondemand_readahead+0x135/0x260
   [<ffffffff8116bfb1>] page_cache_sync_readahead+0x31/0x50
   [<ffffffff81160523>] generic_file_read_iter+0x453/0x760
   [<ffffffff811e0d57>] __vfs_read+0xa7/0xd0

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-03-15 16:55:16 -07:00
Michal Hocko
ccde8bd401 vmstat: make vmstat_update deferrable 
Commit 0eb77e9880 ("vmstat: make vmstat_updater deferrable again and
shut down on idle") made vmstat_shepherd deferrable.  vmstat_update
itself is still useing standard timer which might interrupt idle task.
This is possible because "mm, vmstat: make quiet_vmstat lighter" removed
cancel_delayed_work from the quiet_vmstat.

Change vmstat_work to use DEFERRABLE_WORK to prevent from pointless
wakeups from the idle context.

Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-02-05 18:10:40 -08:00
Michal Hocko
f01f17d370 mm, vmstat: make quiet_vmstat lighter 
Mike has reported a considerable overhead of refresh_cpu_vm_stats from
the idle entry during pipe test:

    12.89%  [kernel]       [k] refresh_cpu_vm_stats.isra.12
     4.75%  [kernel]       [k] __schedule
     4.70%  [kernel]       [k] mutex_unlock
     3.14%  [kernel]       [k] __switch_to

This is caused by commit 0eb77e9880 ("vmstat: make vmstat_updater
deferrable again and shut down on idle") which has placed quiet_vmstat
into cpu_idle_loop.  The main reason here seems to be that the idle
entry has to get over all zones and perform atomic operations for each
vmstat entry even though there might be no per cpu diffs.  This is a
pointless overhead for _each_ idle entry.

Make sure that quiet_vmstat is as light as possible.

First of all it doesn't make any sense to do any local sync if the
current cpu is already set in oncpu_stat_off because vmstat_update puts
itself there only if there is nothing to do.

Then we can check need_update which should be a cheap way to check for
potential per-cpu diffs and only then do refresh_cpu_vm_stats.

The original patch also did cancel_delayed_work which we are not doing
here.  There are two reasons for that.  Firstly cancel_delayed_work from
idle context will blow up on RT kernels (reported by Mike):

  CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.5.0-rt3 #7
  Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.20C 09/23/2013
  Call Trace:
    dump_stack+0x49/0x67
    ___might_sleep+0xf5/0x180
    rt_spin_lock+0x20/0x50
    try_to_grab_pending+0x69/0x240
    cancel_delayed_work+0x26/0xe0
    quiet_vmstat+0x75/0xa0
    cpu_idle_loop+0x38/0x3e0
    cpu_startup_entry+0x13/0x20
    start_secondary+0x114/0x140

And secondly, even on !RT kernels it might add some non trivial overhead
which is not necessary.  Even if the vmstat worker wakes up and preempts
idle then it will be most likely a single shot noop because the stats
were already synced and so it would end up on the oncpu_stat_off anyway.
We just need to teach both vmstat_shepherd and vmstat_update to stop
scheduling the worker if there is nothing to do.

[mgalbraith@suse.de: cancel pending work of the cpu_stat_off CPU]
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-02-05 18:10:40 -08:00
Christoph Lameter
587198ba52 vmstat: Remove BUG_ON from vmstat_update 
If we detect that there is nothing to do just set the flag and do not
check if it was already set before.  Races really do not matter.  If the
flag is set by any code then the shepherd will start dealing with the
situation and reenable the vmstat workers when necessary again.

Since commit 0eb77e9880 ("vmstat: make vmstat_updater deferrable again
and shut down on idle") quiet_vmstat might update cpu_stat_off and mark
a particular cpu to be handled by vmstat_shepherd.  This might trigger a
VM_BUG_ON in vmstat_update because the work item might have been
sleeping during the idle period and see the cpu_stat_off updated after
the wake up.  The VM_BUG_ON is therefore misleading and no more
appropriate.  Moreover it doesn't really suite any protection from real
bugs because vmstat_shepherd will simply reschedule the vmstat_work
anytime it sees a particular cpu set or vmstat_update would do the same
from the worker context directly.  Even when the two would race the
result wouldn't be incorrect as the counters update is fully idempotent.

Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-01-24 08:55:52 -08:00
Minchan Kim
854e9ed09d mm: support madvise(MADV_FREE) 
Linux doesn't have an ability to free pages lazy while other OS already
have been supported that named by madvise(MADV_FREE).

The gain is clear that kernel can discard freed pages rather than
swapping out or OOM if memory pressure happens.

Without memory pressure, freed pages would be reused by userspace
without another additional overhead(ex, page fault + allocation +
zeroing).

Jason Evans said:

: Facebook has been using MAP_UNINITIALIZED
: (https://lkml.org/lkml/2012/1/18/308) in some of its applications for
: several years, but there are operational costs to maintaining this
: out-of-tree in our kernel and in jemalloc, and we are anxious to retire it
: in favor of MADV_FREE.  When we first enabled MAP_UNINITIALIZED it
: increased throughput for much of our workload by ~5%, and although the
: benefit has decreased using newer hardware and kernels, there is still
: enough benefit that we cannot reasonably retire it without a replacement.
:
: Aside from Facebook operations, there are numerous broadly used
: applications that would benefit from MADV_FREE.  The ones that immediately
: come to mind are redis, varnish, and MariaDB.  I don't have much insight
: into Android internals and development process, but I would hope to see
: MADV_FREE support eventually end up there as well to benefit applications
: linked with the integrated jemalloc.
:
: jemalloc will use MADV_FREE once it becomes available in the Linux kernel.
: In fact, jemalloc already uses MADV_FREE or equivalent everywhere it's
: available: *BSD, OS X, Windows, and Solaris -- every platform except Linux
: (and AIX, but I'm not sure it even compiles on AIX).  The lack of
: MADV_FREE on Linux forced me down a long series of increasingly
: sophisticated heuristics for madvise() volume reduction, and even so this
: remains a common performance issue for people using jemalloc on Linux.
: Please integrate MADV_FREE; many people will benefit substantially.

How it works:

When madvise syscall is called, VM clears dirty bit of ptes of the
range.  If memory pressure happens, VM checks dirty bit of page table
and if it found still "clean", it means it's a "lazyfree pages" so VM
could discard the page instead of swapping out.  Once there was store
operation for the page before VM peek a page to reclaim, dirty bit is
set so VM can swap out the page instead of discarding.

One thing we should notice is that basically, MADV_FREE relies on dirty
bit in page table entry to decide whether VM allows to discard the page
or not.  IOW, if page table entry includes marked dirty bit, VM
shouldn't discard the page.

However, as a example, if swap-in by read fault happens, page table
entry doesn't have dirty bit so MADV_FREE could discard the page
wrongly.

For avoiding the problem, MADV_FREE did more checks with PageDirty and
PageSwapCache.  It worked out because swapped-in page lives on swap
cache and since it is evicted from the swap cache, the page has PG_dirty
flag.  So both page flags check effectively prevent wrong discarding by
MADV_FREE.

However, a problem in above logic is that swapped-in page has PG_dirty
still after they are removed from swap cache so VM cannot consider the
page as freeable any more even if madvise_free is called in future.

Look at below example for detail.

    ptr = malloc();
    memset(ptr);
    ..
    ..
    .. heavy memory pressure so all of pages are swapped out
    ..
    ..
    var = *ptr; -> a page swapped-in and could be removed from
                   swapcache. Then, page table doesn't mark
                   dirty bit and page descriptor includes PG_dirty
    ..
    ..
    madvise_free(ptr); -> It doesn't clear PG_dirty of the page.
    ..
    ..
    ..
    .. heavy memory pressure again.
    .. In this time, VM cannot discard the page because the page
    .. has *PG_dirty*

To solve the problem, this patch clears PG_dirty if only the page is
owned exclusively by current process when madvise is called because
PG_dirty represents ptes's dirtiness in several processes so we could
clear it only if we own it exclusively.

Firstly, heavy users would be general allocators(ex, jemalloc, tcmalloc
and hope glibc supports it) and jemalloc/tcmalloc already have supported
the feature for other OS(ex, FreeBSD)

  barrios@blaptop:~/benchmark/ebizzy$ lscpu
  Architecture:          x86_64
  CPU op-mode(s):        32-bit, 64-bit
  Byte Order:            Little Endian
  CPU(s):                12
  On-line CPU(s) list:   0-11
  Thread(s) per core:    1
  Core(s) per socket:    1
  Socket(s):             12
  NUMA node(s):          1
  Vendor ID:             GenuineIntel
  CPU family:            6
  Model:                 2
  Stepping:              3
  CPU MHz:               3200.185
  BogoMIPS:              6400.53
  Virtualization:        VT-x
  Hypervisor vendor:     KVM
  Virtualization type:   full
  L1d cache:             32K
  L1i cache:             32K
  L2 cache:              4096K
  NUMA node0 CPU(s):     0-11
  ebizzy benchmark(./ebizzy -S 10 -n 512)

  Higher avg is better.

   vanilla-jemalloc             MADV_free-jemalloc

  1 thread
  records: 10                   records: 10
  avg:   2961.90                avg:  12069.70
  std:     71.96(2.43%)         std:    186.68(1.55%)
  max:   3070.00                max:  12385.00
  min:   2796.00                min:  11746.00

  2 thread
  records: 10                   records: 10
  avg:   5020.00                avg:  17827.00
  std:    264.87(5.28%)         std:    358.52(2.01%)
  max:   5244.00                max:  18760.00
  min:   4251.00                min:  17382.00

  4 thread
  records: 10                   records: 10
  avg:   8988.80                avg:  27930.80
  std:   1175.33(13.08%)        std:   3317.33(11.88%)
  max:   9508.00                max:  30879.00
  min:   5477.00                min:  21024.00

  8 thread
  records: 10                   records: 10
  avg:  13036.50                avg:  33739.40
  std:    170.67(1.31%)         std:   5146.22(15.25%)
  max:  13371.00                max:  40572.00
  min:  12785.00                min:  24088.00

  16 thread
  records: 10                   records: 10
  avg:  11092.40                avg:  31424.20
  std:    710.60(6.41%)         std:   3763.89(11.98%)
  max:  12446.00                max:  36635.00
  min:   9949.00                min:  25669.00

  32 thread
  records: 10                   records: 10
  avg:  11067.00                avg:  34495.80
  std:    971.06(8.77%)         std:   2721.36(7.89%)
  max:  12010.00                max:  38598.00
  min:   9002.00                min:  30636.00

In summary, MADV_FREE is about much faster than MADV_DONTNEED.

This patch (of 12):

Add core MADV_FREE implementation.

[akpm@linux-foundation.org: small cleanups]
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Mika Penttil <mika.penttila@nextfour.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Jason Evans <je@fb.com>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Shaohua Li <shli@kernel.org>
Cc: <yalin.wang2010@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: "Shaohua Li" <shli@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen Gang <gang.chen.5i5j@gmail.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Helge Deller <deller@gmx.de>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Roland Dreier <roland@kernel.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Shaohua Li <shli@kernel.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-01-15 17:56:32 -08:00
Kirill A. Shutemov
122afea962 mm, vmstats: new THP splitting event 
The patch replaces THP_SPLIT with tree events: THP_SPLIT_PAGE,
THP_SPLIT_PAGE_FAILED and THP_SPLIT_PMD.  It reflects the fact that we
are going to be able split PMD without the compound page and that
split_huge_page() can fail.

Signed-off-by: Kirill A.  Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Christoph Lameter <cl@linux.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-01-15 17:56:32 -08:00
Christoph Lameter
0eb77e9880 vmstat: make vmstat_updater deferrable again and shut down on idle 
Currently the vmstat updater is not deferrable as a result of commit
ba4877b9ca ("vmstat: do not use deferrable delayed work for
vmstat_update").  This in turn can cause multiple interruptions of the
applications because the vmstat updater may run at

Make vmstate_update deferrable again and provide a function that folds
the differentials when the processor is going to idle mode thus
addressing the issue of the above commit in a clean way.

Note that the shepherd thread will continue scanning the differentials
from another processor and will reenable the vmstat workers if it
detects any changes.

Fixes: ba4877b9ca ("vmstat: do not use deferrable delayed work for vmstat_update")
Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-01-14 16:00:49 -08:00
Michal Hocko
751e5f5c75 vmstat: allocate vmstat_wq before it is used 
kernel test robot has reported the following crash:

  BUG: unable to handle kernel NULL pointer dereference at 00000100
  IP: [<c1074df6>] __queue_work+0x26/0x390
  *pdpt = 0000000000000000 *pde = f000ff53f000ff53 *pde = f000ff53f000ff53
  Oops: 0000 [#1] PREEMPT PREEMPT SMP SMP
  CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 4.4.0-rc4-00139-g373ccbe #1
  Workqueue: events vmstat_shepherd
  task: cb684600 ti: cb7ba000 task.ti: cb7ba000
  EIP: 0060:[<c1074df6>] EFLAGS: 00010046 CPU: 0
  EIP is at __queue_work+0x26/0x390
  EAX: 00000046 EBX: cbb37800 ECX: cbb37800 EDX: 00000000
  ESI: 00000000 EDI: 00000000 EBP: cb7bbe68 ESP: cb7bbe38
   DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
  CR0: 8005003b CR2: 00000100 CR3: 01fd5000 CR4: 000006b0
  Stack:
  Call Trace:
    __queue_delayed_work+0xa1/0x160
    queue_delayed_work_on+0x36/0x60
    vmstat_shepherd+0xad/0xf0
    process_one_work+0x1aa/0x4c0
    worker_thread+0x41/0x440
    kthread+0xb0/0xd0
    ret_from_kernel_thread+0x21/0x40

The reason is that start_shepherd_timer schedules the shepherd work item
which uses vmstat_wq (vmstat_shepherd) before setup_vmstat allocates
that workqueue so if the further initialization takes more than HZ we
might end up scheduling on a NULL vmstat_wq.  This is really unlikely
but not impossible.

Fixes: 373ccbe592 ("mm, vmstat: allow WQ concurrency to discover memory reclaim doesn't make any progress")
Reported-by: kernel test robot <ying.huang@linux.intel.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Tested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: stable@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2016-01-08 23:47:54 -08:00
Heiko Carstens
6cdb18ad98 mm/vmstat: fix overflow in mod_zone_page_state() 
mod_zone_page_state() takes a "delta" integer argument.  delta contains
the number of pages that should be added or subtracted from a struct
zone's vm_stat field.

If a zone is larger than 8TB this will cause overflows.  E.g.  for a
zone with a size slightly larger than 8TB the line

    mod_zone_page_state(zone, NR_ALLOC_BATCH, zone->managed_pages);

in mm/page_alloc.c:free_area_init_core() will result in a negative
result for the NR_ALLOC_BATCH entry within the zone's vm_stat, since 8TB
contain 0x8xxxxxxx pages which will be sign extended to a negative
value.

Fix this by changing the delta argument to long type.

This could fix an early boot problem seen on s390, where we have a 9TB
system with only one node.  ZONE_DMA contains 2GB and ZONE_NORMAL the
rest.  The system is trying to allocate a GFP_DMA page but ZONE_DMA is
completely empty, so it tries to reclaim pages in an endless loop.

This was seen on a heavily patched 3.10 kernel.  One possible
explaination seem to be the overflows caused by mod_zone_page_state().
Unfortunately I did not have the chance to verify that this patch
actually fixes the problem, since I don't have access to the system
right now.  However the overflow problem does exist anyway.

Given the description that a system with slightly less than 8TB does
work, this seems to be a candidate for the observed problem.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2015-12-29 17:45:49 -08:00
Michal Hocko
373ccbe592 mm, vmstat: allow WQ concurrency to discover memory reclaim doesn't make any progress 
Tetsuo Handa has reported that the system might basically livelock in
OOM condition without triggering the OOM killer.

The issue is caused by internal dependency of the direct reclaim on
vmstat counter updates (via zone_reclaimable) which are performed from
the workqueue context.  If all the current workers get assigned to an
allocation request, though, they will be looping inside the allocator
trying to reclaim memory but zone_reclaimable can see stalled numbers so
it will consider a zone reclaimable even though it has been scanned way
too much.  WQ concurrency logic will not consider this situation as a
congested workqueue because it relies that worker would have to sleep in
such a situation.  This also means that it doesn't try to spawn new
workers or invoke the rescuer thread if the one is assigned to the
queue.

In order to fix this issue we need to do two things.  First we have to
let wq concurrency code know that we are in trouble so we have to do a
short sleep.  In order to prevent from issues handled by 0e093d9976
("writeback: do not sleep on the congestion queue if there are no
congested BDIs or if significant congestion is not being encountered in
the current zone") we limit the sleep only to worker threads which are
the ones of the interest anyway.

The second thing to do is to create a dedicated workqueue for vmstat and
mark it WQ_MEM_RECLAIM to note it participates in the reclaim and to
have a spare worker thread for it.

Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Tejun Heo <tj@kernel.org>
Cc: Cristopher Lameter <clameter@sgi.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Arkadiusz Miskiewicz <arekm@maven.pl>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2015-12-12 10:15:34 -08:00
Vlastimil Babka
475a2f905d mm: fix swapped Movable and Reclaimable in /proc/pagetypeinfo 
Commit 016c13daa5 ("mm, page_alloc: use masks and shifts when
converting GFP flags to migrate types") has swapped MIGRATE_MOVABLE and
MIGRATE_RECLAIMABLE in the enum definition.  However, migratetype_names
wasn't updated to reflect that.

As a result, the file /proc/pagetypeinfo shows the counts for Movable as
Reclaimable and vice versa.

Additionally, commit 0aaa29a56e ("mm, page_alloc: reserve pageblocks
for high-order atomic allocations on demand") introduced
MIGRATE_HIGHATOMIC, but did not add a letter to distinguish it into
show_migration_types(), so it doesn't appear in the listing of free
areas during page alloc failures or oom kills.

This patch fixes both problems.  The atomic reserves will show with a
letter 'H' in the free areas listings.

Fixes: 016c13daa5 ("mm, page_alloc: use masks and shifts when converting GFP flags to migrate types")
Fixes: 0aaa29a56e ("mm, page_alloc: reserve pageblocks for high-order atomic allocations on demand")
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2015-12-12 10:15:34 -08:00
Mel Gorman
0aaa29a56e mm, page_alloc: reserve pageblocks for high-order atomic allocations on demand 
High-order watermark checking exists for two reasons -- kswapd high-order
awareness and protection for high-order atomic requests.  Historically the
kernel depended on MIGRATE_RESERVE to preserve min_free_kbytes as
high-order free pages for as long as possible.  This patch introduces
MIGRATE_HIGHATOMIC that reserves pageblocks for high-order atomic
allocations on demand and avoids using those blocks for order-0
allocations.  This is more flexible and reliable than MIGRATE_RESERVE was.

A MIGRATE_HIGHORDER pageblock is created when an atomic high-order
allocation request steals a pageblock but limits the total number to 1% of
the zone.  Callers that speculatively abuse atomic allocations for
long-lived high-order allocations to access the reserve will quickly fail.
 Note that SLUB is currently not such an abuser as it reclaims at least
once.  It is possible that the pageblock stolen has few suitable
high-order pages and will need to steal again in the near future but there
would need to be strong justification to search all pageblocks for an
ideal candidate.

The pageblocks are unreserved if an allocation fails after a direct
reclaim attempt.

The watermark checks account for the reserved pageblocks when the
allocation request is not a high-order atomic allocation.

The reserved pageblocks can not be used for order-0 allocations.  This may
allow temporary wastage until a failed reclaim reassigns the pageblock.
This is deliberate as the intent of the reservation is to satisfy a
limited number of atomic high-order short-lived requests if the system
requires them.

The stutter benchmark was used to evaluate this but while it was running
there was a systemtap script that randomly allocated between 1 high-order
page and 12.5% of memory's worth of order-3 pages using GFP_ATOMIC.  This
is much larger than the potential reserve and it does not attempt to be
realistic.  It is intended to stress random high-order allocations from an
unknown source, show that there is a reduction in failures without
introducing an anomaly where atomic allocations are more reliable than
regular allocations.  The amount of memory reserved varied throughout the
workload as reserves were created and reclaimed under memory pressure.
The allocation failures once the workload warmed up were as follows;

4.2-rc5-vanilla		70%
4.2-rc5-atomic-reserve	56%

The failure rate was also measured while building multiple kernels.  The
failure rate was 14% but is 6% with this patch applied.

Overall, this is a small reduction but the reserves are small relative to
the number of allocation requests.  In early versions of the patch, the
failure rate reduced by a much larger amount but that required much larger
reserves and perversely made atomic allocations seem more reliable than
regular allocations.

[yalin.wang2010@gmail.com: fix redundant check and a memory leak]
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2015-11-06 17:50:42 -08:00
Mel Gorman
974a786e63 mm, page_alloc: remove MIGRATE_RESERVE 
MIGRATE_RESERVE preserves an old property of the buddy allocator that
existed prior to fragmentation avoidance -- min_free_kbytes worth of pages
tended to remain contiguous until the only alternative was to fail the
allocation.  At the time it was discovered that high-order atomic
allocations relied on this property so MIGRATE_RESERVE was introduced.  A
later patch will introduce an alternative MIGRATE_HIGHATOMIC so this patch
deletes MIGRATE_RESERVE and supporting code so it'll be easier to review.
Note that this patch in isolation may look like a false regression if
someone was bisecting high-order atomic allocation failures.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2015-11-06 17:50:42 -08:00
Andrew Morton
c2d42c16ad mm/vmstat.c: uninline node_page_state() 
With x86_64 (config http://ozlabs.org/~akpm/config-akpm2.txt) and old gcc
(4.4.4), drivers/base/node.c:node_read_meminfo() is using 2344 bytes of
stack.  Uninlining node_page_state() reduces this to 440 bytes.

The stack consumption issue is fixed by newer gcc (4.8.4) however with
that compiler this patch reduces the node.o text size from 7314 bytes to
4578.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2015-11-05 19:34:48 -08:00
Linus Torvalds
176bed1de5 vmstat: explicitly schedule per-cpu work on the CPU we need it to run on 
The vmstat code uses "schedule_delayed_work_on()" to do the initial
startup of the delayed work on the right CPU, but then once it was
started it would use the non-cpu-specific "schedule_delayed_work()" to
re-schedule it on that CPU.

That just happened to schedule it on the same CPU historically (well, in
almost all situations), but the code _requires_ this work to be per-cpu,
and should say so explicitly rather than depend on the non-cpu-specific
scheduling to schedule on the current CPU.

The timer code is being changed to not be as single-minded in always
running things on the calling CPU.

See also commit 874bbfe600 ("workqueue: make sure delayed work run in
local cpu") that for now maintains the local CPU guarantees just in case
there are other broken users that depended on the accidental behavior.

Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2015-10-15 13:01:50 -07:00
Christoph Lameter
57c2e36b6f vmstat: Reduce time interval to stat update on idle cpu 
It was noted that the vm stat shepherd runs every 2 seconds and that the
vmstat update is then scheduled 2 seconds in the future.

This yields an interval of double the time interval which is not desired.

Change the shepherd so that it does not delay the vmstat update on the
other cpu.  We stil have to use schedule_delayed_work since we are using a
delayed_work_struct but we can set the delay to 0.

Signed-off-by: Christoph Lameter <cl@linux.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2015-02-11 17:06:07 -08:00
Michal Hocko
ba4877b9ca vmstat: do not use deferrable delayed work for vmstat_update 
Vinayak Menon has reported that an excessive number of tasks was throttled
in the direct reclaim inside too_many_isolated() because NR_ISOLATED_FILE
was relatively high compared to NR_INACTIVE_FILE.  However it turned out
that the real number of NR_ISOLATED_FILE was 0 and the per-cpu
vm_stat_diff wasn't transferred into the global counter.

vmstat_work which is responsible for the sync is defined as deferrable
delayed work which means that the defined timeout doesn't wake up an idle
CPU.  A CPU might stay in an idle state for a long time and general effort
is to keep such a CPU in this state as long as possible which might lead
to all sorts of troubles for vmstat consumers as can be seen with the
excessive direct reclaim throttling.

This patch basically reverts 39bf6270f5 ("VM statistics: Make timer
deferrable") but it shouldn't cause any problems for idle CPUs because
only CPUs with an active per-cpu drift are woken up since 7cc36bbddd
("vmstat: on-demand vmstat workers v8") and CPUs which are idle for a
longer time shouldn't have per-cpu drift.

Fixes: 39bf6270f5 (VM statistics: Make timer deferrable)
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reported-by: Vinayak Menon <vinmenon@codeaurora.org>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2015-02-11 17:06:07 -08:00
Andrew Morton
3c48687109 mm/vmstat.c: fix/cleanup ifdefs 
CONFIG_COMPACTION=y, CONFIG_DEBUG_FS=n:

  mm/vmstat.c:690: warning: 'frag_start' defined but not used
  mm/vmstat.c:702: warning: 'frag_next' defined but not used
  mm/vmstat.c:710: warning: 'frag_stop' defined but not used
  mm/vmstat.c:715: warning: 'walk_zones_in_node' defined but not used

It's all a bit of a tangly mess and it's unclear why CONFIG_COMPACTION
figures in there at all.  Move frag_start/frag_next/frag_stop and
migratetype_names[] into the existing CONFIG_PROC_FS block.

walk_zones_in_node() gets a special ifdef.

Also move the #include lines up to where #include lines live.

[axel.lin@ingics.com: fix build error when !CONFIG_PROC_FS]
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Tested-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2015-02-10 14:30:30 -08:00
Davidlohr Bueso
f5f302e212 mm,vmacache: count number of system-wide flushes 
These flushes deal with sequence number overflows, such as for long lived
threads.  These are rare, but interesting from a debugging PoV.  As such,
display the number of flushes when vmacache debugging is enabled.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-12-13 12:42:48 -08:00
Joonsoo Kim
48c96a3685 mm/page_owner: keep track of page owners 
This is the page owner tracking code which is introduced so far ago.  It
is resident on Andrew's tree, though, nobody tried to upstream so it
remain as is.  Our company uses this feature actively to debug memory leak
or to find a memory hogger so I decide to upstream this feature.

This functionality help us to know who allocates the page.  When
allocating a page, we store some information about allocation in extra
memory.  Later, if we need to know status of all pages, we can get and
analyze it from this stored information.

In previous version of this feature, extra memory is statically defined in
struct page, but, in this version, extra memory is allocated outside of
struct page.  It enables us to turn on/off this feature at boottime
without considerable memory waste.

Although we already have tracepoint for tracing page allocation/free,
using it to analyze page owner is rather complex.  We need to enlarge the
trace buffer for preventing overlapping until userspace program launched.
And, launched program continually dump out the trace buffer for later
analysis and it would change system behaviour with more possibility rather
than just keeping it in memory, so bad for debug.

Moreover, we can use page_owner feature further for various purposes.  For
example, we can use it for fragmentation statistics implemented in this
patch.  And, I also plan to implement some CMA failure debugging feature
using this interface.

I'd like to give the credit for all developers contributed this feature,
but, it's not easy because I don't know exact history.  Sorry about that.
Below is people who has "Signed-off-by" in the patches in Andrew's tree.

Contributor:
Alexander Nyberg <alexn@dsv.su.se>
Mel Gorman <mgorman@suse.de>
Dave Hansen <dave@linux.vnet.ibm.com>
Minchan Kim <minchan@kernel.org>
Michal Nazarewicz <mina86@mina86.com>
Andrew Morton <akpm@linux-foundation.org>
Jungsoo Son <jungsoo.son@lge.com>

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Dave Hansen <dave@sr71.net>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Jungsoo Son <jungsoo.son@lge.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-12-13 12:42:48 -08:00
Christoph Lameter
7cc36bbddd vmstat: on-demand vmstat workers V8 
vmstat workers are used for folding counter differentials into the zone,
per node and global counters at certain time intervals.  They currently
run at defined intervals on all processors which will cause some holdoff
for processors that need minimal intrusion by the OS.

The current vmstat_update mechanism depends on a deferrable timer firing
every other second by default which registers a work queue item that runs
on the local CPU, with the result that we have 1 interrupt and one
additional schedulable task on each CPU every 2 seconds If a workload
indeed causes VM activity or multiple tasks are running on a CPU, then
there are probably bigger issues to deal with.

However, some workloads dedicate a CPU for a single CPU bound task.  This
is done in high performance computing, in high frequency financial
applications, in networking (Intel DPDK, EZchip NPS) and with the advent
of systems with more and more CPUs over time, this may become more and
more common to do since when one has enough CPUs one cares less about
efficiently sharing a CPU with other tasks and more about efficiently
monopolizing a CPU per task.

The difference of having this timer firing and workqueue kernel thread
scheduled per second can be enormous.  An artificial test measuring the
worst case time to do a simple "i++" in an endless loop on a bare metal
system and under Linux on an isolated CPU with dynticks and with and
without this patch, have Linux match the bare metal performance (~700
cycles) with this patch and loose by couple of orders of magnitude (~200k
cycles) without it[*].  The loss occurs for something that just calculates
statistics.  For networking applications, for example, this could be the
difference between dropping packets or sustaining line rate.

Statistics are important and useful, but it would be great if there would
be a way to not cause statistics gathering produce a huge performance
difference.  This patche does just that.

This patch creates a vmstat shepherd worker that monitors the per cpu
differentials on all processors.  If there are differentials on a
processor then a vmstat worker local to the processors with the
differentials is created.  That worker will then start folding the diffs
in regular intervals.  Should the worker find that there is no work to be
done then it will make the shepherd worker monitor the differentials
again.

With this patch it is possible then to have periods longer than
2 seconds without any OS event on a "cpu" (hardware thread).

The patch shows a very minor increased in system performance.

hackbench -s 512 -l 2000 -g 15 -f 25 -P

Results before the patch:

Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks)
Each sender will pass 2000 messages of 512 bytes
Time: 4.992
Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks)
Each sender will pass 2000 messages of 512 bytes
Time: 4.971
Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks)
Each sender will pass 2000 messages of 512 bytes
Time: 5.063

Hackbench after the patch:

Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks)
Each sender will pass 2000 messages of 512 bytes
Time: 4.973
Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks)
Each sender will pass 2000 messages of 512 bytes
Time: 4.990
Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks)
Each sender will pass 2000 messages of 512 bytes
Time: 4.993

[fengguang.wu@intel.com: cpu_stat_off can be static]
Signed-off-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Max Krasnyansky <maxk@qti.qualcomm.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-10-09 22:26:02 -04:00
Konstantin Khlebnikov
09316c09dd mm/balloon_compaction: add vmstat counters and kpageflags bit 
Always mark pages with PageBalloon even if balloon compaction is disabled
and expose this mark in /proc/kpageflags as KPF_BALLOON.

Also this patch adds three counters into /proc/vmstat: "balloon_inflate",
"balloon_deflate" and "balloon_migrate".  They accumulate balloon
activity.  Current size of balloon is (balloon_inflate - balloon_deflate)
pages.

All generic balloon code now gathered under option CONFIG_MEMORY_BALLOON.
It should be selected by ballooning driver which wants use this feature.
Currently virtio-balloon is the only user.

Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-10-09 22:26:01 -04:00
Mel Gorman
bb0b6dffa2 mm: vmscan: only update per-cpu thresholds for online CPU 
When kswapd is awake reclaiming, the per-cpu stat thresholds are lowered
to get more accurate counts to avoid breaching watermarks.  This
threshold update iterates over all possible CPUs which is unnecessary.
Only online CPUs need to be updated.  If a new CPU is onlined,
refresh_zone_stat_thresholds() will set the thresholds correctly.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-08-06 18:01:20 -07:00
Mel Gorman
0d5d823ab4 mm: move zone->pages_scanned into a vmstat counter 
zone->pages_scanned is a write-intensive cache line during page reclaim
and it's also updated during page free.  Move the counter into vmstat to
take advantage of the per-cpu updates and do not update it in the free
paths unless necessary.

On a small UMA machine running tiobench the difference is marginal.  On
a 4-node machine the overhead is more noticable.  Note that automatic
NUMA balancing was disabled for this test as otherwise the system CPU
overhead is unpredictable.

          3.16.0-rc3  3.16.0-rc3  3.16.0-rc3
             vanillarearrange-v5   vmstat-v5
User          746.94      759.78      774.56
System      65336.22    58350.98    32847.27
Elapsed     27553.52    27282.02    27415.04

Note that the overhead reduction will vary depending on where exactly
pages are allocated and freed.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-08-06 18:01:20 -07:00
Mel Gorman
3484b2de94 mm: rearrange zone fields into read-only, page alloc, statistics and page reclaim lines 
The arrangement of struct zone has changed over time and now it has
reached the point where there is some inappropriate sharing going on.
On x86-64 for example

o The zone->node field is shared with the zone lock and zone->node is
  accessed frequently from the page allocator due to the fair zone
  allocation policy.

o span_seqlock is almost never used by shares a line with free_area

o Some zone statistics share a cache line with the LRU lock so
  reclaim-intensive and allocator-intensive workloads can bounce the cache
  line on a stat update

This patch rearranges struct zone to put read-only and read-mostly
fields together and then splits the page allocator intensive fields, the
zone statistics and the page reclaim intensive fields into their own
cache lines.  Note that the type of lowmem_reserve changes due to the
watermark calculations being signed and avoiding a signed/unsigned
conversion there.

On the test configuration I used the overall size of struct zone shrunk
by one cache line.  On smaller machines, this is not likely to be
noticable.  However, on a 4-node NUMA machine running tiobench the
system CPU overhead is reduced by this patch.

          3.16.0-rc3  3.16.0-rc3
             vanillarearrange-v5r9
User          746.94      759.78
System      65336.22    58350.98
Elapsed     27553.52    27282.02

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-08-06 18:01:20 -07:00
Jianyu Zhan
bea04b0732 mm: use the light version __mod_zone_page_state in mlocked_vma_newpage() 
mlocked_vma_newpage() is called with pte lock held(a spinlock), which
implies preemtion disabled, and the vm stat counter is not modified from
interrupt context, so we need not use an irq-safe mod_zone_page_state()
here, using a light-weight version __mod_zone_page_state() would be OK.

This patch also documents __mod_zone_page_state() and some of its
callsites.  The comment above __mod_zone_page_state() is from Hugh
Dickins, and acked by Christoph.

Most credits to Hugh and Christoph for the clarification on the usage of
the __mod_zone_page_state().

[akpm@linux-foundation.org: coding-style fixes]
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-06-04 16:54:07 -07:00
Christoph Lameter
7c8e0181e6 mm: replace __get_cpu_var uses with this_cpu_ptr 
Replace places where __get_cpu_var() is used for an address calculation
with this_cpu_ptr().

Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-06-04 16:54:03 -07:00
Davidlohr Bueso
4f115147ff mm,vmacache: add debug data 
Introduce a CONFIG_DEBUG_VM_VMACACHE option to enable counting the cache
hit rate -- exported in /proc/vmstat.

Any updates to the caching scheme needs this kind of data, thus it can
save some work re-implementing the counting all the time.

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-06-04 16:53:57 -07:00
Linus Torvalds
467a9e1633 CPU hotplug notifiers registration fixes for 3.15-rc1 
The purpose of this single series of commits from Srivatsa S Bhat (with
 a small piece from Gautham R Shenoy) touching multiple subsystems that use
 CPU hotplug notifiers is to provide a way to register them that will not
 lead to deadlocks with CPU online/offline operations as described in the
 changelog of commit 93ae4f978c (CPU hotplug: Provide lockless versions
 of callback registration functions).
 
 The first three commits in the series introduce the API and document it
 and the rest simply goes through the users of CPU hotplug notifiers and
 converts them to using the new method.
 
 /
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Merge tag 'cpu-hotplug-3.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull CPU hotplug notifiers registration fixes from Rafael Wysocki:
 "The purpose of this single series of commits from Srivatsa S Bhat
  (with a small piece from Gautham R Shenoy) touching multiple
  subsystems that use CPU hotplug notifiers is to provide a way to
  register them that will not lead to deadlocks with CPU online/offline
  operations as described in the changelog of commit 93ae4f978c ("CPU
  hotplug: Provide lockless versions of callback registration
  functions").

  The first three commits in the series introduce the API and document
  it and the rest simply goes through the users of CPU hotplug notifiers
  and converts them to using the new method"

* tag 'cpu-hotplug-3.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (52 commits)
  net/iucv/iucv.c: Fix CPU hotplug callback registration
  net/core/flow.c: Fix CPU hotplug callback registration
  mm, zswap: Fix CPU hotplug callback registration
  mm, vmstat: Fix CPU hotplug callback registration
  profile: Fix CPU hotplug callback registration
  trace, ring-buffer: Fix CPU hotplug callback registration
  xen, balloon: Fix CPU hotplug callback registration
  hwmon, via-cputemp: Fix CPU hotplug callback registration
  hwmon, coretemp: Fix CPU hotplug callback registration
  thermal, x86-pkg-temp: Fix CPU hotplug callback registration
  octeon, watchdog: Fix CPU hotplug callback registration
  oprofile, nmi-timer: Fix CPU hotplug callback registration
  intel-idle: Fix CPU hotplug callback registration
  clocksource, dummy-timer: Fix CPU hotplug callback registration
  drivers/base/topology.c: Fix CPU hotplug callback registration
  acpi-cpufreq: Fix CPU hotplug callback registration
  zsmalloc: Fix CPU hotplug callback registration
  scsi, fcoe: Fix CPU hotplug callback registration
  scsi, bnx2fc: Fix CPU hotplug callback registration
  scsi, bnx2i: Fix CPU hotplug callback registration
  ...
 2014-04-07 14:55:46 -07:00
Dave Hansen
5509a5d27b drop_caches: add some documentation and info message 
There is plenty of anecdotal evidence and a load of blog posts
suggesting that using "drop_caches" periodically keeps your system
running in "tip top shape".  Perhaps adding some kernel documentation
will increase the amount of accurate data on its use.

If we are not shrinking caches effectively, then we have real bugs.
Using drop_caches will simply mask the bugs and make them harder to
find, but certainly does not fix them, nor is it an appropriate
"workaround" to limit the size of the caches.  On the contrary, there
have been bug reports on issues that turned out to be misguided use of
cache dropping.

Dropping caches is a very drastic and disruptive operation that is good
for debugging and running tests, but if it creates bug reports from
production use, kernel developers should be aware of its use.

Add a bit more documentation about it, a syslog message to track down
abusers, and vmstat drop counters to help analyze problem reports.

[akpm@linux-foundation.org: checkpatch fixes]
[hannes@cmpxchg.org: add runtime suppression control]
Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-04-03 16:21:04 -07:00
Johannes Weiner
449dd6984d mm: keep page cache radix tree nodes in check 
Previously, page cache radix tree nodes were freed after reclaim emptied
out their page pointers.  But now reclaim stores shadow entries in their
place, which are only reclaimed when the inodes themselves are
reclaimed.  This is problematic for bigger files that are still in use
after they have a significant amount of their cache reclaimed, without
any of those pages actually refaulting.  The shadow entries will just
sit there and waste memory.  In the worst case, the shadow entries will
accumulate until the machine runs out of memory.

To get this under control, the VM will track radix tree nodes
exclusively containing shadow entries on a per-NUMA node list.  Per-NUMA
rather than global because we expect the radix tree nodes themselves to
be allocated node-locally and we want to reduce cross-node references of
otherwise independent cache workloads.  A simple shrinker will then
reclaim these nodes on memory pressure.

A few things need to be stored in the radix tree node to implement the
shadow node LRU and allow tree deletions coming from the list:

1. There is no index available that would describe the reverse path
   from the node up to the tree root, which is needed to perform a
   deletion.  To solve this, encode in each node its offset inside the
   parent.  This can be stored in the unused upper bits of the same
   member that stores the node's height at no extra space cost.

2. The number of shadow entries needs to be counted in addition to the
   regular entries, to quickly detect when the node is ready to go to
   the shadow node LRU list.  The current entry count is an unsigned
   int but the maximum number of entries is 64, so a shadow counter
   can easily be stored in the unused upper bits.

3. Tree modification needs tree lock and tree root, which are located
   in the address space, so store an address_space backpointer in the
   node.  The parent pointer of the node is in a union with the 2-word
   rcu_head, so the backpointer comes at no extra cost as well.

4. The node needs to be linked to an LRU list, which requires a list
   head inside the node.  This does increase the size of the node, but
   it does not change the number of objects that fit into a slab page.

[akpm@linux-foundation.org: export the right function]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Metin Doslu <metin@citusdata.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ozgun Erdogan <ozgun@citusdata.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-04-03 16:21:01 -07:00
Johannes Weiner
a528910e12 mm: thrash detection-based file cache sizing 
The VM maintains cached filesystem pages on two types of lists.  One
list holds the pages recently faulted into the cache, the other list
holds pages that have been referenced repeatedly on that first list.
The idea is to prefer reclaiming young pages over those that have shown
to benefit from caching in the past.  We call the recently usedbut
ultimately was not significantly better than a FIFO policy and still
thrashed cache based on eviction speed, rather than actual demand for
cache.

This patch solves one half of the problem by decoupling the ability to
detect working set changes from the inactive list size.  By maintaining
a history of recently evicted file pages it can detect frequently used
pages with an arbitrarily small inactive list size, and subsequently
apply pressure on the active list based on actual demand for cache, not
just overall eviction speed.

Every zone maintains a counter that tracks inactive list aging speed.
When a page is evicted, a snapshot of this counter is stored in the
now-empty page cache radix tree slot.  On refault, the minimum access
distance of the page can be assessed, to evaluate whether the page
should be part of the active list or not.

This fixes the VM's blindness towards working set changes in excess of
the inactive list.  And it's the foundation to further improve the
protection ability and reduce the minimum inactive list size of 50%.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Metin Doslu <metin@citusdata.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ozgun Erdogan <ozgun@citusdata.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2014-04-03 16:21:01 -07:00
Srivatsa S. Bhat
0be94bad0b mm, vmstat: Fix CPU hotplug callback registration 
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Instead, the correct and race-free way of performing the callback
registration is:

	cpu_notifier_register_begin();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	/* Note the use of the double underscored version of the API */
	__register_cpu_notifier(&foobar_cpu_notifier);

	cpu_notifier_register_done();

Fix the vmstat code in the MM subsystem by using this latter form of callback
registration.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
 2014-03-20 13:43:48 +01:00
Mel Gorman
ec65993443 mm, x86: Account for TLB flushes only when debugging 
Bisection between 3.11 and 3.12 fingered commit 9824cf97 ("mm:
vmstats: tlb flush counters") to cause overhead problems.

The counters are undeniably useful but how often do we really
need to debug TLB flush related issues?  It does not justify
taking the penalty everywhere so make it a debugging option.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Tested-by: Davidlohr Bueso <davidlohr@hp.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Alex Shi <alex.shi@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-XzxjntugxuwpxXhcrxqqh53b@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2014-01-25 09:10:41 +01:00
Mel Gorman
72403b4a0f mm: numa: return the number of base pages altered by protection changes 
Commit 0255d49184 ("mm: Account for a THP NUMA hinting update as one
PTE update") was added to account for the number of PTE updates when
marking pages prot_numa.  task_numa_work was using the old return value
to track how much address space had been updated.  Altering the return
value causes the scanner to do more work than it is configured or
documented to in a single unit of work.

This patch reverts that commit and accounts for the number of THP
updates separately in vmstat.  It is up to the administrator to
interpret the pair of values correctly.  This is a straight-forward
operation and likely to only be of interest when actively debugging NUMA
balancing problems.

The impact of this patch is that the NUMA PTE scanner will scan slower
when THP is enabled and workloads may converge slower as a result.  On
the flip size system CPU usage should be lower than recent tests
reported.  This is an illustrative example of a short single JVM specjbb
test

specjbb
                       3.12.0                3.12.0
                      vanilla      acctupdates
TPut 1      26143.00 (  0.00%)     25747.00 ( -1.51%)
TPut 7     185257.00 (  0.00%)    183202.00 ( -1.11%)
TPut 13    329760.00 (  0.00%)    346577.00 (  5.10%)
TPut 19    442502.00 (  0.00%)    460146.00 (  3.99%)
TPut 25    540634.00 (  0.00%)    549053.00 (  1.56%)
TPut 31    512098.00 (  0.00%)    519611.00 (  1.47%)
TPut 37    461276.00 (  0.00%)    474973.00 (  2.97%)
TPut 43    403089.00 (  0.00%)    414172.00 (  2.75%)

              3.12.0      3.12.0
             vanillaacctupdates
User         5169.64     5184.14
System        100.45       80.02
Elapsed       252.75      251.85

Performance is similar but note the reduction in system CPU time.  While
this showed a performance gain, it will not be universal but at least
it'll be behaving as documented.  The vmstats are obviously different but
here is an obvious interpretation of them from mmtests.

                                3.12.0      3.12.0
                               vanillaacctupdates
NUMA page range updates        1408326    11043064
NUMA huge PMD updates                0       21040
NUMA PTE updates               1408326      291624

"NUMA page range updates" == nr_pte_updates and is the value returned to
the NUMA pte scanner.  NUMA huge PMD updates were the number of THP
updates which in combination can be used to calculate how many ptes were
updated from userspace.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reported-by: Alex Thorlton <athorlton@sgi.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-11-13 12:09:11 +09:00
Toshi Kani
807a1bd2b2 mm: clear N_CPU from node_states at CPU offline 
vmstat_cpuup_callback() is a CPU notifier callback, which marks N_CPU to a
node at CPU online event.  However, it does not update this N_CPU info at
CPU offline event.

Changed vmstat_cpuup_callback() to clear N_CPU when the last CPU in the
node is put into offline, i.e.  the node no longer has any online CPU.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Acked-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Tested-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-11-13 12:09:09 +09:00
Toshi Kani
d7e0b37a87 mm: set N_CPU to node_states during boot 
After a system booted, N_CPU is not set to any node as has_cpu shows an
empty line.

  # cat /sys/devices/system/node/has_cpu
  (show-empty-line)

setup_vmstat() registers its CPU notifier callback,
vmstat_cpuup_callback(), which marks N_CPU to a node when a CPU is put
into online.  However, setup_vmstat() is called after all CPUs are
launched in the boot sequence.

Changed setup_vmstat() to mark N_CPU to the nodes with online CPUs at
boot, which is consistent with other operations in
vmstat_cpuup_callback(), i.e.  start_cpu_timer() and
refresh_zone_stat_thresholds().

Also added get_online_cpus() to protect the for_each_online_cpu() loop.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Acked-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Tested-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-11-13 12:09:09 +09:00
Lisa Du
6e543d5780 mm: vmscan: fix do_try_to_free_pages() livelock 
This patch is based on KOSAKI's work and I add a little more description,
please refer https://lkml.org/lkml/2012/6/14/74.

Currently, I found system can enter a state that there are lots of free
pages in a zone but only order-0 and order-1 pages which means the zone is
heavily fragmented, then high order allocation could make direct reclaim
path's long stall(ex, 60 seconds) especially in no swap and no compaciton
enviroment.  This problem happened on v3.4, but it seems issue still lives
in current tree, the reason is do_try_to_free_pages enter live lock:

kswapd will go to sleep if the zones have been fully scanned and are still
not balanced.  As kswapd thinks there's little point trying all over again
to avoid infinite loop.  Instead it changes order from high-order to
0-order because kswapd think order-0 is the most important.  Look at
73ce02e9 in detail.  If watermarks are ok, kswapd will go back to sleep
and may leave zone->all_unreclaimable =3D 0.  It assume high-order users
can still perform direct reclaim if they wish.

Direct reclaim continue to reclaim for a high order which is not a
COSTLY_ORDER without oom-killer until kswapd turn on
zone->all_unreclaimble= .  This is because to avoid too early oom-kill.
So it means direct_reclaim depends on kswapd to break this loop.

In worst case, direct-reclaim may continue to page reclaim forever when
kswapd sleeps forever until someone like watchdog detect and finally kill
the process.  As described in:
http://thread.gmane.org/gmane.linux.kernel.mm/103737

We can't turn on zone->all_unreclaimable from direct reclaim path because
direct reclaim path don't take any lock and this way is racy.  Thus this
patch removes zone->all_unreclaimable field completely and recalculates
zone reclaimable state every time.

Note: we can't take the idea that direct-reclaim see zone->pages_scanned
directly and kswapd continue to use zone->all_unreclaimable.  Because, it
is racy.  commit 929bea7c71 (vmscan: all_unreclaimable() use
zone->all_unreclaimable as a name) describes the detail.

[akpm@linux-foundation.org: uninline zone_reclaimable_pages() and zone_reclaimable()]
Cc: Aaditya Kumar <aaditya.kumar.30@gmail.com>
Cc: Ying Han <yinghan@google.com>
Cc: Nick Piggin <npiggin@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Bob Liu <lliubbo@gmail.com>
Cc: Neil Zhang <zhangwm@marvell.com>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Lisa Du <cldu@marvell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-09-11 15:58:01 -07:00
Christoph Lameter
fbc2edb053 vmstat: use this_cpu() to avoid irqon/off sequence in refresh_cpu_vm_stats 
Disabling interrupts repeatedly can be avoided in the inner loop if we use
a this_cpu operation.

Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Tejun Heo <tj@kernel.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-09-11 15:57:31 -07:00
Christoph Lameter
4edb0748b2 vmstat: create fold_diff 
Both functions that update global counters use the same mechanism.

Create a function that contains the common code.

Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Tejun Heo <tj@kernel.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-09-11 15:57:31 -07:00
Christoph Lameter
2bb921e526 vmstat: create separate function to fold per cpu diffs into local counters 
The main idea behind this patchset is to reduce the vmstat update overhead
by avoiding interrupt enable/disable and the use of per cpu atomics.

This patch (of 3):

It is better to have a separate folding function because
refresh_cpu_vm_stats() also does other things like expire pages in the
page allocator caches.

If we have a separate function then refresh_cpu_vm_stats() is only called
from the local cpu which allows additional optimizations.

The folding function is only called when a cpu is being downed and
therefore no other processor will be accessing the counters.  Also
simplifies synchronization.

[akpm@linux-foundation.org: fix UP build]
Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Tejun Heo <tj@kernel.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-09-11 15:57:31 -07:00
Johannes Weiner
81c0a2bb51 mm: page_alloc: fair zone allocator policy 
Each zone that holds userspace pages of one workload must be aged at a
speed proportional to the zone size.  Otherwise, the time an individual
page gets to stay in memory depends on the zone it happened to be
allocated in.  Asymmetry in the zone aging creates rather unpredictable
aging behavior and results in the wrong pages being reclaimed, activated
etc.

But exactly this happens right now because of the way the page allocator
and kswapd interact.  The page allocator uses per-node lists of all zones
in the system, ordered by preference, when allocating a new page.  When
the first iteration does not yield any results, kswapd is woken up and the
allocator retries.  Due to the way kswapd reclaims zones below the high
watermark while a zone can be allocated from when it is above the low
watermark, the allocator may keep kswapd running while kswapd reclaim
ensures that the page allocator can keep allocating from the first zone in
the zonelist for extended periods of time.  Meanwhile the other zones
rarely see new allocations and thus get aged much slower in comparison.

The result is that the occasional page placed in lower zones gets
relatively more time in memory, even gets promoted to the active list
after its peers have long been evicted.  Meanwhile, the bulk of the
working set may be thrashing on the preferred zone even though there may
be significant amounts of memory available in the lower zones.

Even the most basic test -- repeatedly reading a file slightly bigger than
memory -- shows how broken the zone aging is.  In this scenario, no single
page should be able stay in memory long enough to get referenced twice and
activated, but activation happens in spades:

  $ grep active_file /proc/zoneinfo
      nr_inactive_file 0
      nr_active_file 0
      nr_inactive_file 0
      nr_active_file 8
      nr_inactive_file 1582
      nr_active_file 11994
  $ cat data data data data >/dev/null
  $ grep active_file /proc/zoneinfo
      nr_inactive_file 0
      nr_active_file 70
      nr_inactive_file 258753
      nr_active_file 443214
      nr_inactive_file 149793
      nr_active_file 12021

Fix this with a very simple round robin allocator.  Each zone is allowed a
batch of allocations that is proportional to the zone's size, after which
it is treated as full.  The batch counters are reset when all zones have
been tried and the allocator enters the slowpath and kicks off kswapd
reclaim.  Allocation and reclaim is now fairly spread out to all
available/allowable zones:

  $ grep active_file /proc/zoneinfo
      nr_inactive_file 0
      nr_active_file 0
      nr_inactive_file 174
      nr_active_file 4865
      nr_inactive_file 53
      nr_active_file 860
  $ cat data data data data >/dev/null
  $ grep active_file /proc/zoneinfo
      nr_inactive_file 0
      nr_active_file 0
      nr_inactive_file 666622
      nr_active_file 4988
      nr_inactive_file 190969
      nr_active_file 937

When zone_reclaim_mode is enabled, allocations will now spread out to all
zones on the local node, not just the first preferred zone (which on a 4G
node might be a tiny Normal zone).

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Paul Bolle <paul.bollee@gmail.com>
Cc: Zlatko Calusic <zcalusic@bitsync.net>
Tested-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-09-11 15:57:23 -07:00
Dave Hansen
6df46865ff mm: vmstats: track TLB flush stats on UP too 
The previous patch doing vmstats for TLB flushes ("mm: vmstats: tlb flush
counters") effectively missed UP since arch/x86/mm/tlb.c is only compiled
for SMP.

UP systems do not do remote TLB flushes, so compile those counters out on
UP.

arch/x86/kernel/cpu/mtrr/generic.c calls __flush_tlb() directly.  This is
probably an optimization since both the mtrr code and __flush_tlb() write
cr4.  It would probably be safe to make that a flush_tlb_all() (and then
get these statistics), but the mtrr code is ancient and I'm hesitant to
touch it other than to just stick in the counters.

[akpm@linux-foundation.org: tweak comments]
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-09-11 15:57:09 -07:00
Dave Hansen
9824cf9753 mm: vmstats: tlb flush counters 
I was investigating some TLB flush scaling issues and realized that we do
not have any good methods for figuring out how many TLB flushes we are
doing.

It would be nice to be able to do these in generic code, but the
arch-independent calls don't explicitly specify whether we actually need
to do remote flushes or not.  In the end, we really need to know if we
actually _did_ global vs.  local invalidations, so that leaves us with few
options other than to muck with the counters from arch-specific code.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-09-11 15:57:08 -07:00
Paul Gortmaker
0db0628d90 kernel: delete __cpuinit usage from all core kernel files 
The __cpuinit type of throwaway sections might have made sense
some time ago when RAM was more constrained, but now the savings
do not offset the cost and complications.  For example, the fix in
commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time")
is a good example of the nasty type of bugs that can be created
with improper use of the various __init prefixes.

After a discussion on LKML[1] it was decided that cpuinit should go
the way of devinit and be phased out.  Once all the users are gone,
we can then finally remove the macros themselves from linux/init.h.

This removes all the uses of the __cpuinit macros from C files in
the core kernel directories (kernel, init, lib, mm, and include)
that don't really have a specific maintainer.

[1] https://lkml.org/lkml/2013/5/20/589

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
 2013-07-14 19:36:59 -04:00
Cody P Schafer
40f4b1ead0 mm/vmstat: add note on safety of drain_zonestat 
Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-04-29 15:54:38 -07:00
Yijing Wang
f1cb08798e mm: remove CONFIG_HOTPLUG ifdefs 
CONFIG_HOTPLUG is going away as an option, cleanup CONFIG_HOTPLUG
ifdefs in mm files.

Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-04-29 15:54:37 -07:00
Cody P Schafer
108bcc96ef mm: add & use zone_end_pfn() and zone_spans_pfn() 
Add 2 helpers (zone_end_pfn() and zone_spans_pfn()) to reduce code
duplication.

This also switches to using them in compaction (where an additional
variable needed to be renamed), page_alloc, vmstat, memory_hotplug, and
kmemleak.

Note that in compaction.c I avoid calling zone_end_pfn() repeatedly
because I expect at some point the sycronization issues with start_pfn &
spanned_pages will need fixing, either by actually using the seqlock or
clever memory barrier usage.

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Hansen <dave@linux.vnet.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-02-23 17:50:20 -08:00
Zlatko Calusic
258401a60c mm: don't wait on congested zones in balance_pgdat() 
From: Zlatko Calusic <zlatko.calusic@iskon.hr>

Commit 92df3a723f ("mm: vmscan: throttle reclaim if encountering too
many dirty pages under writeback") introduced waiting on congested zones
based on a sane algorithm in shrink_inactive_list().

What this means is that there's no more need for throttling and
additional heuristics in balance_pgdat().  So, let's remove it and tidy
up the code.

Signed-off-by: Zlatko Calusic <zlatko.calusic@iskon.hr>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-02-23 17:50:15 -08:00
Minchan Kim
194159fbcc mm: remove MIGRATE_ISOLATE check in hotpath 
Several functions test MIGRATE_ISOLATE and some of those are hotpath but
MIGRATE_ISOLATE is used only if we enable CONFIG_MEMORY_ISOLATION(ie,
CMA, memory-hotplug and memory-failure) which are not common config
option.  So let's not add unnecessary overhead and code when we don't
enable CONFIG_MEMORY_ISOLATION.

Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-02-23 17:50:15 -08:00
Jiang Liu
b40da04946 mm: use zone->present_pages instead of zone->managed_pages where appropriate 
Now we have zone->managed_pages for "pages managed by the buddy system
in the zone", so replace zone->present_pages with zone->managed_pages if
what the user really wants is number of allocatable pages.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jiang Liu <jiang.liu@huawei.com>
Cc: Maciej Rutecki <maciej.rutecki@gmail.com>
Cc: Chris Clayton <chris2553@googlemail.com>
Cc: "Rafael J . Wysocki" <rjw@sisk.pl>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Jianguo Wu <wujianguo@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2013-02-23 17:50:14 -08:00
Linus Torvalds
3d59eebc5e Automatic NUMA Balancing V11 
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Merge tag 'balancenuma-v11' of git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux-balancenuma

Pull Automatic NUMA Balancing bare-bones from Mel Gorman:
 "There are three implementations for NUMA balancing, this tree
  (balancenuma), numacore which has been developed in tip/master and
  autonuma which is in aa.git.

  In almost all respects balancenuma is the dumbest of the three because
  its main impact is on the VM side with no attempt to be smart about
  scheduling.  In the interest of getting the ball rolling, it would be
  desirable to see this much merged for 3.8 with the view to building
  scheduler smarts on top and adapting the VM where required for 3.9.

  The most recent set of comparisons available from different people are

    mel:    https://lkml.org/lkml/2012/12/9/108
    mingo:  https://lkml.org/lkml/2012/12/7/331
    tglx:   https://lkml.org/lkml/2012/12/10/437
    srikar: https://lkml.org/lkml/2012/12/10/397

  The results are a mixed bag.  In my own tests, balancenuma does
  reasonably well.  It's dumb as rocks and does not regress against
  mainline.  On the other hand, Ingo's tests shows that balancenuma is
  incapable of converging for this workloads driven by perf which is bad
  but is potentially explained by the lack of scheduler smarts.  Thomas'
  results show balancenuma improves on mainline but falls far short of
  numacore or autonuma.  Srikar's results indicate we all suffer on a
  large machine with imbalanced node sizes.

  My own testing showed that recent numacore results have improved
  dramatically, particularly in the last week but not universally.
  We've butted heads heavily on system CPU usage and high levels of
  migration even when it shows that overall performance is better.
  There are also cases where it regresses.  Of interest is that for
  specjbb in some configurations it will regress for lower numbers of
  warehouses and show gains for higher numbers which is not reported by
  the tool by default and sometimes missed in treports.  Recently I
  reported for numacore that the JVM was crashing with
  NullPointerExceptions but currently it's unclear what the source of
  this problem is.  Initially I thought it was in how numacore batch
  handles PTEs but I'm no longer think this is the case.  It's possible
  numacore is just able to trigger it due to higher rates of migration.

  These reports were quite late in the cycle so I/we would like to start
  with this tree as it contains much of the code we can agree on and has
  not changed significantly over the last 2-3 weeks."

* tag 'balancenuma-v11' of git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux-balancenuma: (50 commits)
  mm/rmap, migration: Make rmap_walk_anon() and try_to_unmap_anon() more scalable
  mm/rmap: Convert the struct anon_vma::mutex to an rwsem
  mm: migrate: Account a transhuge page properly when rate limiting
  mm: numa: Account for failed allocations and isolations as migration failures
  mm: numa: Add THP migration for the NUMA working set scanning fault case build fix
  mm: numa: Add THP migration for the NUMA working set scanning fault case.
  mm: sched: numa: Delay PTE scanning until a task is scheduled on a new node
  mm: sched: numa: Control enabling and disabling of NUMA balancing if !SCHED_DEBUG
  mm: sched: numa: Control enabling and disabling of NUMA balancing
  mm: sched: Adapt the scanning rate if a NUMA hinting fault does not migrate
  mm: numa: Use a two-stage filter to restrict pages being migrated for unlikely task<->node relationships
  mm: numa: migrate: Set last_nid on newly allocated page
  mm: numa: split_huge_page: Transfer last_nid on tail page
  mm: numa: Introduce last_nid to the page frame
  sched: numa: Slowly increase the scanning period as NUMA faults are handled
  mm: numa: Rate limit setting of pte_numa if node is saturated
  mm: numa: Rate limit the amount of memory that is migrated between nodes
  mm: numa: Structures for Migrate On Fault per NUMA migration rate limiting
  mm: numa: Migrate pages handled during a pmd_numa hinting fault
  mm: numa: Migrate on reference policy
  ...
 2012-12-16 15:18:08 -08:00
Jiang Liu
9feedc9d83 mm: introduce new field "managed_pages" to struct zone 
Currently a zone's present_pages is calcuated as below, which is
inaccurate and may cause trouble to memory hotplug.

	spanned_pages - absent_pages - memmap_pages - dma_reserve.

During fixing bugs caused by inaccurate zone->present_pages, we found
zone->present_pages has been abused.  The field zone->present_pages may
have different meanings in different contexts:

1) pages existing in a zone.
2) pages managed by the buddy system.

For more discussions about the issue, please refer to:
  http://lkml.org/lkml/2012/11/5/866
  https://patchwork.kernel.org/patch/1346751/

This patchset tries to introduce a new field named "managed_pages" to
struct zone, which counts "pages managed by the buddy system".  And revert
zone->present_pages to count "physical pages existing in a zone", which
also keep in consistence with pgdat->node_present_pages.

We will set an initial value for zone->managed_pages in function
free_area_init_core() and will adjust it later if the initial value is
inaccurate.

For DMA/normal zones, the initial value is set to:

	(spanned_pages - absent_pages - memmap_pages - dma_reserve)

Later zone->managed_pages will be adjusted to the accurate value when the
bootmem allocator frees all free pages to the buddy system in function
free_all_bootmem_node() and free_all_bootmem().

The bootmem allocator doesn't touch highmem pages, so highmem zones'
managed_pages is set to the accurate value "spanned_pages - absent_pages"
in function free_area_init_core() and won't be updated anymore.

This patch also adds a new field "managed_pages" to /proc/zoneinfo
and sysrq showmem.

[akpm@linux-foundation.org: small comment tweaks]
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Maciej Rutecki <maciej.rutecki@gmail.com>
Tested-by: Chris Clayton <chris2553@googlemail.com>
Cc: "Rafael J . Wysocki" <rjw@sisk.pl>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Jianguo Wu <wujianguo@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-12-12 17:38:34 -08:00
Lai Jiangshan
a47b53c5f9 vmstat: use N_MEMORY instead N_HIGH_MEMORY 
N_HIGH_MEMORY stands for the nodes that has normal or high memory.
N_MEMORY stands for the nodes that has any memory.

The code here need to handle with the nodes which have memory, we should
use N_MEMORY instead.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Lin Feng <linfeng@cn.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-12-12 17:38:33 -08:00
Kirill A. Shutemov
d8a8e1f0da thp, vmstat: implement HZP_ALLOC and HZP_ALLOC_FAILED events 
hzp_alloc is incremented every time a huge zero page is successfully
	allocated. It includes allocations which where dropped due
	race with other allocation. Note, it doesn't count every map
	of the huge zero page, only its allocation.

hzp_alloc_failed is incremented if kernel fails to allocate huge zero
	page and falls back to using small pages.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@linux.intel.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-12-12 17:38:32 -08:00
Mel Gorman
03c5a6e163 mm: numa: Add pte updates, hinting and migration stats 
It is tricky to quantify the basic cost of automatic NUMA placement in a
meaningful manner. This patch adds some vmstats that can be used as part
of a basic costing model.

u    = basic unit = sizeof(void *)
Ca   = cost of struct page access = sizeof(struct page) / u
Cpte = Cost PTE access = Ca
Cupdate = Cost PTE update = (2 * Cpte) + (2 * Wlock)
	where Cpte is incurred twice for a read and a write and Wlock
	is a constant representing the cost of taking or releasing a
	lock
Cnumahint = Cost of a minor page fault = some high constant e.g. 1000
Cpagerw = Cost to read or write a full page = Ca + PAGE_SIZE/u
Ci = Cost of page isolation = Ca + Wi
	where Wi is a constant that should reflect the approximate cost
	of the locking operation
Cpagecopy = Cpagerw + (Cpagerw * Wnuma) + Ci + (Ci * Wnuma)
	where Wnuma is the approximate NUMA factor. 1 is local. 1.2
	would imply that remote accesses are 20% more expensive

Balancing cost = Cpte * numa_pte_updates +
		Cnumahint * numa_hint_faults +
		Ci * numa_pages_migrated +
		Cpagecopy * numa_pages_migrated

Note that numa_pages_migrated is used as a measure of how many pages
were isolated even though it would miss pages that failed to migrate. A
vmstat counter could have been added for it but the isolation cost is
pretty marginal in comparison to the overall cost so it seemed overkill.

The ideal way to measure automatic placement benefit would be to count
the number of remote accesses versus local accesses and do something like

	benefit = (remote_accesses_before - remove_access_after) * Wnuma

but the information is not readily available. As a workload converges, the
expection would be that the number of remote numa hints would reduce to 0.

	convergence = numa_hint_faults_local / numa_hint_faults
		where this is measured for the last N number of
		numa hints recorded. When the workload is fully
		converged the value is 1.

This can measure if the placement policy is converging and how fast it is
doing it.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
 2012-12-11 14:42:48 +00:00
Mel Gorman
397487db69 mm: compaction: Add scanned and isolated counters for compaction 
Compaction already has tracepoints to count scanned and isolated pages
but it requires that ftrace be enabled and if that information has to be
written to disk then it can be disruptive. This patch adds vmstat counters
for compaction called compact_migrate_scanned, compact_free_scanned and
compact_isolated.

With these counters, it is possible to define a basic cost model for
compaction. This approximates of how much work compaction is doing and can
be compared that with an oprofile showing TLB misses and see if the cost of
compaction is being offset by THP for example. Minimally a compaction patch
can be evaluated in terms of whether it increases or decreases cost. The
basic cost model looks like this

Fundamental unit u:	a word	sizeof(void *)

Ca  = cost of struct page access = sizeof(struct page) / u

Cmc = Cost migrate page copy = (Ca + PAGE_SIZE/u) * 2
Cmf = Cost migrate failure   = Ca * 2
Ci  = Cost page isolation    = (Ca + Wi)
	where Wi is a constant that should reflect the approximate
	cost of the locking operation.

Csm = Cost migrate scanning = Ca
Csf = Cost free    scanning = Ca

Overall cost =	(Csm * compact_migrate_scanned) +
	      	(Csf * compact_free_scanned)    +
	      	(Ci  * compact_isolated)	+
		(Cmc * pgmigrate_success)	+
		(Cmf * pgmigrate_failed)

Where the values are read from /proc/vmstat.

This is very basic and ignores certain costs such as the allocation cost
to do a migrate page copy but any improvement to the model would still
use the same vmstat counters.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
 2012-12-11 14:28:35 +00:00
Mel Gorman
5647bc293a mm: compaction: Move migration fail/success stats to migrate.c 
The compact_pages_moved and compact_pagemigrate_failed events are
convenient for determining if compaction is active and to what
degree migration is succeeding but it's at the wrong level. Other
users of migration may also want to know if migration is working
properly and this will be particularly true for any automated
NUMA migration. This patch moves the counters down to migration
with the new events called pgmigrate_success and pgmigrate_fail.
The compact_blocks_moved counter is removed because while it was
useful for debugging initially, it's worthless now as no meaningful
conclusions can be drawn from its value.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
 2012-12-11 14:28:35 +00:00
Hugh Dickins
8befedfe67 mm: remove unevictable_pgs_mlockfreed 
Simply remove UNEVICTABLE_MLOCKFREED and unevictable_pgs_mlockfreed line
from /proc/vmstat: Johannes and Mel point out that it was very unlikely to
have been used by any tool, and of course we can restore it easily enough
if that turns out to be wrong.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ying Han <yinghan@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-10-09 16:22:59 +09:00
Minchan Kim
5a88381384 memory-hotplug: fix zone stat mismatch 
During memory-hotplug, I found NR_ISOLATED_[ANON|FILE] are increasing,
causing the kernel to hang.  When the system doesn't have enough free
pages, it enters reclaim but never reclaim any pages due to
too_many_isolated()==true and loops forever.

The cause is that when we do memory-hotadd after memory-remove,
__zone_pcp_update() clears a zone's ZONE_STAT_ITEMS in setup_pageset()
although the vm_stat_diff of all CPUs still have values.

In addtion, when we offline all pages of the zone, we reset them in
zone_pcp_reset without draining so we loss some zone stat item.

Reviewed-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-10-09 16:22:59 +09:00
Hugh Dickins
a0c5e813f0 mm: remove free_page_mlock 
We should not be seeing non-0 unevictable_pgs_mlockfreed any longer.  So
remove free_page_mlock() from the page freeing paths: __PG_MLOCKED is
already in PAGE_FLAGS_CHECK_AT_FREE, so free_pages_check() will now be
checking it, reporting "BUG: Bad page state" if it's ever found set.
Comment UNEVICTABLE_MLOCKFREED and unevictable_pgs_mlockfreed always 0.

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-10-09 16:22:56 +09:00
Bartlomiej Zolnierkiewicz
d1ce749a0d cma: count free CMA pages 
Add NR_FREE_CMA_PAGES counter to be later used for checking watermark in
__zone_watermark_ok().  For simplicity and to avoid #ifdef hell make this
counter always available (not only when CONFIG_CMA=y).

[akpm@linux-foundation.org: use conventional migratetype naming]
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-10-09 16:22:44 +09:00
Tejun Heo
203b42f731 workqueue: make deferrable delayed_work initializer names consistent 
Initalizers for deferrable delayed_work are confused.

* __DEFERRED_WORK_INITIALIZER()
* DECLARE_DEFERRED_WORK()
* INIT_DELAYED_WORK_DEFERRABLE()

Rename them to

* __DEFERRABLE_WORK_INITIALIZER()
* DECLARE_DEFERRABLE_WORK()
* INIT_DEFERRABLE_WORK()

This patch doesn't cause any functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
 2012-08-21 13:18:23 -07:00
Mel Gorman
68243e76ee mm: account for the number of times direct reclaimers get throttled 
Under significant pressure when writing back to network-backed storage,
direct reclaimers may get throttled.  This is expected to be a short-lived
event and the processes get woken up again but processes do get stalled.
This patch counts how many times such stalling occurs.  It's up to the
administrator whether to reduce these stalls by increasing
min_free_kbytes.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: David Miller <davem@davemloft.net>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-07-31 18:42:46 -07:00
Sasikantha babu
bde8bd8a1d mm/vmstat.c: remove debug fs entries on failure of file creation and made extfrag_debug_root dentry local 
Remove debug fs files and directory on failure.  Since no one is using
"extfrag_debug_root" dentry outside of extfrag_debug_init(), make it
local to the function.

Signed-off-by: Sasikantha babu <sasikanth.v19@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-05-29 16:22:19 -07:00
Michal Nazarewicz
47118af076 mm: mmzone: MIGRATE_CMA migration type added 
The MIGRATE_CMA migration type has two main characteristics:
(i) only movable pages can be allocated from MIGRATE_CMA
pageblocks and (ii) page allocator will never change migration
type of MIGRATE_CMA pageblocks.

This guarantees (to some degree) that page in a MIGRATE_CMA page
block can always be migrated somewhere else (unless there's no
memory left in the system).

It is designed to be used for allocating big chunks (eg. 10MiB)
of physically contiguous memory.  Once driver requests
contiguous memory, pages from MIGRATE_CMA pageblocks may be
migrated away to create a contiguous block.

To minimise number of migrations, MIGRATE_CMA migration type
is the last type tried when page allocator falls back to other
migration types when requested.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Rob Clark <rob.clark@linaro.org>
Tested-by: Ohad Ben-Cohen <ohad@wizery.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Robert Nelson <robertcnelson@gmail.com>
Tested-by: Barry Song <Baohua.Song@csr.com>
 2012-05-21 15:09:32 +02:00
Ying Han
904249aa68 mm: fix up the vmscan stat in vmstat 
The "pgsteal" stat is confusing because it counts both direct reclaim as
well as background reclaim.  However, we have "kswapd_steal" which also
counts background reclaim value.

This patch fixes it and also makes it match the existng "pgscan_" stats.

Test:
pgsteal_kswapd_dma32 447623
pgsteal_kswapd_normal 42272677
pgsteal_kswapd_movable 0
pgsteal_direct_dma32 2801
pgsteal_direct_normal 44353270
pgsteal_direct_movable 0

Signed-off-by: Ying Han <yinghan@google.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Mel Gorman <mel@csn.ul.ie>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-04-25 21:26:33 -07:00
Heiko Carstens
4156153c4d mm,x86,um: move CMPXCHG_LOCAL config option 
Move CMPXCHG_LOCAL and rename it to HAVE_CMPXCHG_LOCAL so architectures
can simply select the option if it is supported.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-01-12 20:13:03 -08:00
Dimitri Sivanich
a1cb2c60dd mm/vmstat.c: cache align vm_stat 
Avoid false sharing of the vm_stat array.

This was found to adversely affect tmpfs I/O performance.

Tests run on a 640 cpu UV system.

With 120 threads doing parallel writes, each to different tmpfs mounts:
No patch:		~300 MB/sec
With vm_stat alignment:	~430 MB/sec

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Acked-by: Christoph Lameter <cl@gentwo.org>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-10-31 17:30:51 -07:00
Mel Gorman
49ea7eb65e mm: vmscan: immediately reclaim end-of-LRU dirty pages when writeback completes 
When direct reclaim encounters a dirty page, it gets recycled around the
LRU for another cycle.  This patch marks the page PageReclaim similar to
deactivate_page() so that the page gets reclaimed almost immediately after
the page gets cleaned.  This is to avoid reclaiming clean pages that are
younger than a dirty page encountered at the end of the LRU that might
have been something like a use-once page.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <jweiner@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Alex Elder <aelder@sgi.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-10-31 17:30:47 -07:00
Mel Gorman
ee72886d8e mm: vmscan: do not writeback filesystem pages in direct reclaim 
Testing from the XFS folk revealed that there is still too much I/O from
the end of the LRU in kswapd.  Previously it was considered acceptable by
VM people for a small number of pages to be written back from reclaim with
testing generally showing about 0.3% of pages reclaimed were written back
(higher if memory was low).  That writing back a small number of pages is
ok has been heavily disputed for quite some time and Dave Chinner
explained it well;

	It doesn't have to be a very high number to be a problem. IO
	is orders of magnitude slower than the CPU time it takes to
	flush a page, so the cost of making a bad flush decision is
	very high. And single page writeback from the LRU is almost
	always a bad flush decision.

To complicate matters, filesystems respond very differently to requests
from reclaim according to Christoph Hellwig;

	xfs tries to write it back if the requester is kswapd
	ext4 ignores the request if it's a delayed allocation
	btrfs ignores the request

As a result, each filesystem has different performance characteristics
when under memory pressure and there are many pages being dirtied.  In
some cases, the request is ignored entirely so the VM cannot depend on the
IO being dispatched.

The objective of this series is to reduce writing of filesystem-backed
pages from reclaim, play nicely with writeback that is already in progress
and throttle reclaim appropriately when writeback pages are encountered.
The assumption is that the flushers will always write pages faster than if
reclaim issues the IO.

A secondary goal is to avoid the problem whereby direct reclaim splices
two potentially deep call stacks together.

There is a potential new problem as reclaim has less control over how long
before a page in a particularly zone or container is cleaned and direct
reclaimers depend on kswapd or flusher threads to do the necessary work.
However, as filesystems sometimes ignore direct reclaim requests already,
it is not expected to be a serious issue.

Patch 1 disables writeback of filesystem pages from direct reclaim
	entirely. Anonymous pages are still written.

Patch 2 removes dead code in lumpy reclaim as it is no longer able
	to synchronously write pages. This hurts lumpy reclaim but
	there is an expectation that compaction is used for hugepage
	allocations these days and lumpy reclaim's days are numbered.

Patches 3-4 add warnings to XFS and ext4 if called from
	direct reclaim. With patch 1, this "never happens" and is
	intended to catch regressions in this logic in the future.

Patch 5 disables writeback of filesystem pages from kswapd unless
	the priority is raised to the point where kswapd is considered
	to be in trouble.

Patch 6 throttles reclaimers if too many dirty pages are being
	encountered and the zones or backing devices are congested.

Patch 7 invalidates dirty pages found at the end of the LRU so they
	are reclaimed quickly after being written back rather than
	waiting for a reclaimer to find them

I consider this series to be orthogonal to the writeback work but it is
worth noting that the writeback work affects the viability of patch 8 in
particular.

I tested this on ext4 and xfs using fs_mark, a simple writeback test based
on dd and a micro benchmark that does a streaming write to a large mapping
(exercises use-once LRU logic) followed by streaming writes to a mix of
anonymous and file-backed mappings.  The command line for fs_mark when
botted with 512M looked something like

./fs_mark -d  /tmp/fsmark-2676  -D  100  -N  150  -n  150  -L  25  -t  1  -S0  -s  10485760

The number of files was adjusted depending on the amount of available
memory so that the files created was about 3xRAM.  For multiple threads,
the -d switch is specified multiple times.

The test machine is x86-64 with an older generation of AMD processor with
4 cores.  The underlying storage was 4 disks configured as RAID-0 as this
was the best configuration of storage I had available.  Swap is on a
separate disk.  Dirty ratio was tuned to 40% instead of the default of
20%.

Testing was run with and without monitors to both verify that the patches
were operating as expected and that any performance gain was real and not
due to interference from monitors.

Here is a summary of results based on testing XFS.

512M1P-xfs           Files/s  mean                 32.69 ( 0.00%)     34.44 ( 5.08%)
512M1P-xfs           Elapsed Time fsmark                    51.41     48.29
512M1P-xfs           Elapsed Time simple-wb                114.09    108.61
512M1P-xfs           Elapsed Time mmap-strm                113.46    109.34
512M1P-xfs           Kswapd efficiency fsmark                 62%       63%
512M1P-xfs           Kswapd efficiency simple-wb              56%       61%
512M1P-xfs           Kswapd efficiency mmap-strm              44%       42%
512M-xfs             Files/s  mean                 30.78 ( 0.00%)     35.94 (14.36%)
512M-xfs             Elapsed Time fsmark                    56.08     48.90
512M-xfs             Elapsed Time simple-wb                112.22     98.13
512M-xfs             Elapsed Time mmap-strm                219.15    196.67
512M-xfs             Kswapd efficiency fsmark                 54%       56%
512M-xfs             Kswapd efficiency simple-wb              54%       55%
512M-xfs             Kswapd efficiency mmap-strm              45%       44%
512M-4X-xfs          Files/s  mean                 30.31 ( 0.00%)     33.33 ( 9.06%)
512M-4X-xfs          Elapsed Time fsmark                    63.26     55.88
512M-4X-xfs          Elapsed Time simple-wb                100.90     90.25
512M-4X-xfs          Elapsed Time mmap-strm                261.73    255.38
512M-4X-xfs          Kswapd efficiency fsmark                 49%       50%
512M-4X-xfs          Kswapd efficiency simple-wb              54%       56%
512M-4X-xfs          Kswapd efficiency mmap-strm              37%       36%
512M-16X-xfs         Files/s  mean                 60.89 ( 0.00%)     65.22 ( 6.64%)
512M-16X-xfs         Elapsed Time fsmark                    67.47     58.25
512M-16X-xfs         Elapsed Time simple-wb                103.22     90.89
512M-16X-xfs         Elapsed Time mmap-strm                237.09    198.82
512M-16X-xfs         Kswapd efficiency fsmark                 45%       46%
512M-16X-xfs         Kswapd efficiency simple-wb              53%       55%
512M-16X-xfs         Kswapd efficiency mmap-strm              33%       33%

Up until 512-4X, the FSmark improvements were statistically significant.
For the 4X and 16X tests the results were within standard deviations but
just barely.  The time to completion for all tests is improved which is an
important result.  In general, kswapd efficiency is not affected by
skipping dirty pages.

1024M1P-xfs          Files/s  mean                 39.09 ( 0.00%)     41.15 ( 5.01%)
1024M1P-xfs          Elapsed Time fsmark                    84.14     80.41
1024M1P-xfs          Elapsed Time simple-wb                210.77    184.78
1024M1P-xfs          Elapsed Time mmap-strm                162.00    160.34
1024M1P-xfs          Kswapd efficiency fsmark                 69%       75%
1024M1P-xfs          Kswapd efficiency simple-wb              71%       77%
1024M1P-xfs          Kswapd efficiency mmap-strm              43%       44%
1024M-xfs            Files/s  mean                 35.45 ( 0.00%)     37.00 ( 4.19%)
1024M-xfs            Elapsed Time fsmark                    94.59     91.00
1024M-xfs            Elapsed Time simple-wb                229.84    195.08
1024M-xfs            Elapsed Time mmap-strm                405.38    440.29
1024M-xfs            Kswapd efficiency fsmark                 79%       71%
1024M-xfs            Kswapd efficiency simple-wb              74%       74%
1024M-xfs            Kswapd efficiency mmap-strm              39%       42%
1024M-4X-xfs         Files/s  mean                 32.63 ( 0.00%)     35.05 ( 6.90%)
1024M-4X-xfs         Elapsed Time fsmark                   103.33     97.74
1024M-4X-xfs         Elapsed Time simple-wb                204.48    178.57
1024M-4X-xfs         Elapsed Time mmap-strm                528.38    511.88
1024M-4X-xfs         Kswapd efficiency fsmark                 81%       70%
1024M-4X-xfs         Kswapd efficiency simple-wb              73%       72%
1024M-4X-xfs         Kswapd efficiency mmap-strm              39%       38%
1024M-16X-xfs        Files/s  mean                 42.65 ( 0.00%)     42.97 ( 0.74%)
1024M-16X-xfs        Elapsed Time fsmark                   103.11     99.11
1024M-16X-xfs        Elapsed Time simple-wb                200.83    178.24
1024M-16X-xfs        Elapsed Time mmap-strm                397.35    459.82
1024M-16X-xfs        Kswapd efficiency fsmark                 84%       69%
1024M-16X-xfs        Kswapd efficiency simple-wb              74%       73%
1024M-16X-xfs        Kswapd efficiency mmap-strm              39%       40%

All FSMark tests up to 16X had statistically significant improvements.
For the most part, tests are completing faster with the exception of the
streaming writes to a mixture of anonymous and file-backed mappings which
were slower in two cases

In the cases where the mmap-strm tests were slower, there was more
swapping due to dirty pages being skipped.  The number of additional pages
swapped is almost identical to the fewer number of pages written from
reclaim.  In other words, roughly the same number of pages were reclaimed
but swapping was slower.  As the test is a bit unrealistic and stresses
memory heavily, the small shift is acceptable.

4608M1P-xfs          Files/s  mean                 29.75 ( 0.00%)     30.96 ( 3.91%)
4608M1P-xfs          Elapsed Time fsmark                   512.01    492.15
4608M1P-xfs          Elapsed Time simple-wb                618.18    566.24
4608M1P-xfs          Elapsed Time mmap-strm                488.05    465.07
4608M1P-xfs          Kswapd efficiency fsmark                 93%       86%
4608M1P-xfs          Kswapd efficiency simple-wb              88%       84%
4608M1P-xfs          Kswapd efficiency mmap-strm              46%       45%
4608M-xfs            Files/s  mean                 27.60 ( 0.00%)     28.85 ( 4.33%)
4608M-xfs            Elapsed Time fsmark                   555.96    532.34
4608M-xfs            Elapsed Time simple-wb                659.72    571.85
4608M-xfs            Elapsed Time mmap-strm               1082.57   1146.38
4608M-xfs            Kswapd efficiency fsmark                 89%       91%
4608M-xfs            Kswapd efficiency simple-wb              88%       82%
4608M-xfs            Kswapd efficiency mmap-strm              48%       46%
4608M-4X-xfs         Files/s  mean                 26.00 ( 0.00%)     27.47 ( 5.35%)
4608M-4X-xfs         Elapsed Time fsmark                   592.91    564.00
4608M-4X-xfs         Elapsed Time simple-wb                616.65    575.07
4608M-4X-xfs         Elapsed Time mmap-strm               1773.02   1631.53
4608M-4X-xfs         Kswapd efficiency fsmark                 90%       94%
4608M-4X-xfs         Kswapd efficiency simple-wb              87%       82%
4608M-4X-xfs         Kswapd efficiency mmap-strm              43%       43%
4608M-16X-xfs        Files/s  mean                 26.07 ( 0.00%)     26.42 ( 1.32%)
4608M-16X-xfs        Elapsed Time fsmark                   602.69    585.78
4608M-16X-xfs        Elapsed Time simple-wb                606.60    573.81
4608M-16X-xfs        Elapsed Time mmap-strm               1549.75   1441.86
4608M-16X-xfs        Kswapd efficiency fsmark                 98%       98%
4608M-16X-xfs        Kswapd efficiency simple-wb              88%       82%
4608M-16X-xfs        Kswapd efficiency mmap-strm              44%       42%

Unlike the other tests, the fsmark results are not statistically
significant but the min and max times are both improved and for the most
part, tests completed faster.

There are other indications that this is an improvement as well.  For
example, in the vast majority of cases, there were fewer pages scanned by
direct reclaim implying in many cases that stalls due to direct reclaim
are reduced.  KSwapd is scanning more due to skipping dirty pages which is
unfortunate but the CPU usage is still acceptable

In an earlier set of tests, I used blktrace and in almost all cases
throughput throughout the entire test was higher.  However, I ended up
discarding those results as recording blktrace data was too heavy for my
liking.

On a laptop, I plugged in a USB stick and ran a similar tests of tests
using it as backing storage.  A desktop environment was running and for
the entire duration of the tests, firefox and gnome terminal were
launching and exiting to vaguely simulate a user.

1024M-xfs            Files/s  mean               0.41 ( 0.00%)        0.44 ( 6.82%)
1024M-xfs            Elapsed Time fsmark               2053.52   1641.03
1024M-xfs            Elapsed Time simple-wb            1229.53    768.05
1024M-xfs            Elapsed Time mmap-strm            4126.44   4597.03
1024M-xfs            Kswapd efficiency fsmark              84%       85%
1024M-xfs            Kswapd efficiency simple-wb           92%       81%
1024M-xfs            Kswapd efficiency mmap-strm           60%       51%
1024M-xfs            Avg wait ms fsmark                5404.53     4473.87
1024M-xfs            Avg wait ms simple-wb             2541.35     1453.54
1024M-xfs            Avg wait ms mmap-strm             3400.25     3852.53

The mmap-strm results were hurt because firefox launching had a tendency
to push the test out of memory.  On the postive side, firefox launched
marginally faster with the patches applied.  Time to completion for many
tests was faster but more importantly - the "Avg wait" time as measured by
iostat was far lower implying the system would be more responsive.  It was
also the case that "Avg wait ms" on the root filesystem was lower.  I
tested it manually and while the system felt slightly more responsive
while copying data to a USB stick, it was marginal enough that it could be
my imagination.

This patch: do not writeback filesystem pages in direct reclaim.

When kswapd is failing to keep zones above the min watermark, a process
will enter direct reclaim in the same manner kswapd does.  If a dirty page
is encountered during the scan, this page is written to backing storage
using mapping->writepage.

This causes two problems.  First, it can result in very deep call stacks,
particularly if the target storage or filesystem are complex.  Some
filesystems ignore write requests from direct reclaim as a result.  The
second is that a single-page flush is inefficient in terms of IO.  While
there is an expectation that the elevator will merge requests, this does
not always happen.  Quoting Christoph Hellwig;

	The elevator has a relatively small window it can operate on,
	and can never fix up a bad large scale writeback pattern.

This patch prevents direct reclaim writing back filesystem pages by
checking if current is kswapd.  Anonymous pages are still written to swap
as there is not the equivalent of a flusher thread for anonymous pages.
If the dirty pages cannot be written back, they are placed back on the LRU
lists.  There is now a direct dependency on dirty page balancing to
prevent too many pages in the system being dirtied which would prevent
reclaim making forward progress.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Alex Elder <aelder@sgi.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-10-31 17:30:46 -07:00
David Rientjes
0d6617c773 numa: fix NUMA compile error when sysfs and procfs are disabled 
The vmstat_text array is only defined for CONFIG_SYSFS or CONFIG_PROC_FS,
yet it is referenced for per-node vmstat with CONFIG_NUMA:

	drivers/built-in.o: In function `node_read_vmstat':
	node.c:(.text+0x1106df): undefined reference to `vmstat_text'

Introduced in commit fa25c503df ("mm: per-node vmstat: show proper
vmstats").

Define the array for CONFIG_NUMA as well.

[akpm@linux-foundation.org: remove unneeded ifdefs]
Signed-off-by: David Rientjes <rientjes@google.com>
Reported-by: Cong Wang <amwang@redhat.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-09-14 18:09:37 -07:00
KOSAKI Motohiro
a6cccdc36c mm, mem-hotplug: update pcp->stat_threshold when memory hotplug occur 
Currently, cpu hotplug updates pcp->stat_threshold, but memory hotplug
doesn't.  There is no reason for this.

[akpm@linux-foundation.org: fix CONFIG_SMP=n build]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-05-25 08:39:09 -07:00
KOSAKI Motohiro
fa25c503df mm: per-node vmstat: show proper vmstats 
commit 2ac390370a ("writeback: add
/sys/devices/system/node/<node>/vmstat") added vmstat entry.  But
strangely it only show nr_written and nr_dirtied.

        # cat /sys/devices/system/node/node20/vmstat
        nr_written 0
        nr_dirtied 0

Of course, It's not adequate.  With this patch, the vmstat show all vm
stastics as /proc/vmstat.

        # cat /sys/devices/system/node/node0/vmstat
	nr_free_pages 899224
	nr_inactive_anon 201
	nr_active_anon 17380
	nr_inactive_file 31572
	nr_active_file 28277
	nr_unevictable 0
	nr_mlock 0
	nr_anon_pages 17321
	nr_mapped 8640
	nr_file_pages 60107
	nr_dirty 33
	nr_writeback 0
	nr_slab_reclaimable 6850
	nr_slab_unreclaimable 7604
	nr_page_table_pages 3105
	nr_kernel_stack 175
	nr_unstable 0
	nr_bounce 0
	nr_vmscan_write 0
	nr_writeback_temp 0
	nr_isolated_anon 0
	nr_isolated_file 0
	nr_shmem 260
	nr_dirtied 1050
	nr_written 938
	numa_hit 962872
	numa_miss 0
	numa_foreign 0
	numa_interleave 8617
	numa_local 962872
	numa_other 0
	nr_anon_transparent_hugepages 0

[akpm@linux-foundation.org: no externs in .c files]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-05-25 08:39:07 -07:00
Andi Kleen
81ab4201fb mm: add VM counters for transparent hugepages 
I found it difficult to make sense of transparent huge pages without
having any counters for its actions.  Add some counters to vmstat for
allocation of transparent hugepages and fallback to smaller pages.

Optional patch, but useful for development and understanding the system.

Contains improvements from Andrea Arcangeli and Johannes Weiner

[akpm@linux-foundation.org: coding-style fixes]
[hannes@cmpxchg.org: fix vmstat_text[] entries]
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-04-14 16:06:55 -07:00
Christoph Lameter
d3bc236718 vmstat: update comment regarding stat_threshold 
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-04-14 16:06:54 -07:00
Andi Kleen
78afd5612d mm: add __GFP_OTHER_NODE flag 
Add a new __GFP_OTHER_NODE flag to tell the low level numa statistics in
zone_statistics() that an allocation is on behalf of another thread.  This
way the local and remote counters can be still correct, even when
background daemons like khugepaged are changing memory mappings.

This only affects the accounting, but I think it's worth doing that right
to avoid confusing users.

I first tried to just pass down the right node, but this required a lot of
changes to pass down this parameter and at least one addition of a 10th
argument to a 9 argument function.  Using the flag is a lot less
intrusive.

Open: should be also used for migration?

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-03-22 17:44:05 -07:00
Andrea Arcangeli
79134171df thp: transparent hugepage vmstat 
Add hugepage stat information to /proc/vmstat and /proc/meminfo.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-01-13 17:32:43 -08:00
Mel Gorman
b44129b306 mm: vmstat: use a single setter function and callback for adjusting percpu thresholds 
reduce_pgdat_percpu_threshold() and restore_pgdat_percpu_threshold() exist
to adjust the per-cpu vmstat thresholds while kswapd is awake to avoid
errors due to counter drift.  The functions duplicate some code so this
patch replaces them with a single set_pgdat_percpu_threshold() that takes
a callback function to calculate the desired threshold as a parameter.

[akpm@linux-foundation.org: readability tweak]
[kosaki.motohiro@jp.fujitsu.com: set_pgdat_percpu_threshold(): don't use for_each_online_cpu]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Christoph Lameter <cl@linux.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-01-13 17:32:31 -08:00
Mel Gorman
88f5acf88a mm: page allocator: adjust the per-cpu counter threshold when memory is low 
Commit aa45484 ("calculate a better estimate of NR_FREE_PAGES when memory
is low") noted that watermarks were based on the vmstat NR_FREE_PAGES.  To
avoid synchronization overhead, these counters are maintained on a per-cpu
basis and drained both periodically and when a threshold is above a
threshold.  On large CPU systems, the difference between the estimate and
real value of NR_FREE_PAGES can be very high.  The system can get into a
case where pages are allocated far below the min watermark potentially
causing livelock issues.  The commit solved the problem by taking a better
reading of NR_FREE_PAGES when memory was low.

Unfortately, as reported by Shaohua Li this accurate reading can consume a
large amount of CPU time on systems with many sockets due to cache line
bouncing.  This patch takes a different approach.  For large machines
where counter drift might be unsafe and while kswapd is awake, the per-cpu
thresholds for the target pgdat are reduced to limit the level of drift to
what should be a safe level.  This incurs a performance penalty in heavy
memory pressure by a factor that depends on the workload and the machine
but the machine should function correctly without accidentally exhausting
all memory on a node.  There is an additional cost when kswapd wakes and
sleeps but the event is not expected to be frequent - in Shaohua's test
case, there was one recorded sleep and wake event at least.

To ensure that kswapd wakes up, a safe version of zone_watermark_ok() is
introduced that takes a more accurate reading of NR_FREE_PAGES when called
from wakeup_kswapd, when deciding whether it is really safe to go back to
sleep in sleeping_prematurely() and when deciding if a zone is really
balanced or not in balance_pgdat().  We are still using an expensive
function but limiting how often it is called.

When the test case is reproduced, the time spent in the watermark
functions is reduced.  The following report is on the percentage of time
spent cumulatively spent in the functions zone_nr_free_pages(),
zone_watermark_ok(), __zone_watermark_ok(), zone_watermark_ok_safe(),
zone_page_state_snapshot(), zone_page_state().

vanilla                      11.6615%
disable-threshold            0.2584%

David said:

: We had to pull aa454840 "mm: page allocator: calculate a better estimate
: of NR_FREE_PAGES when memory is low and kswapd is awake" from 2.6.36
: internally because tests showed that it would cause the machine to stall
: as the result of heavy kswapd activity.  I merged it back with this fix as
: it is pending in the -mm tree and it solves the issue we were seeing, so I
: definitely think this should be pushed to -stable (and I would seriously
: consider it for 2.6.37 inclusion even at this late date).

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reported-by: Shaohua Li <shaohua.li@intel.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Tested-by: Nicolas Bareil <nico@chdir.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: <stable@kernel.org>		[2.6.37.1, 2.6.36.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2011-01-13 17:32:31 -08:00
Linus Torvalds
72eb6a7914 Merge branch 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 
* 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (30 commits)
  gameport: use this_cpu_read instead of lookup
  x86: udelay: Use this_cpu_read to avoid address calculation
  x86: Use this_cpu_inc_return for nmi counter
  x86: Replace uses of current_cpu_data with this_cpu ops
  x86: Use this_cpu_ops to optimize code
  vmstat: User per cpu atomics to avoid interrupt disable / enable
  irq_work: Use per cpu atomics instead of regular atomics
  cpuops: Use cmpxchg for xchg to avoid lock semantics
  x86: this_cpu_cmpxchg and this_cpu_xchg operations
  percpu: Generic this_cpu_cmpxchg() and this_cpu_xchg support
  percpu,x86: relocate this_cpu_add_return() and friends
  connector: Use this_cpu operations
  xen: Use this_cpu_inc_return
  taskstats: Use this_cpu_ops
  random: Use this_cpu_inc_return
  fs: Use this_cpu_inc_return in buffer.c
  highmem: Use this_cpu_xx_return() operations
  vmstat: Use this_cpu_inc_return for vm statistics
  x86: Support for this_cpu_add, sub, dec, inc_return
  percpu: Generic support for this_cpu_add, sub, dec, inc_return
  ...

Fixed up conflicts: in arch/x86/kernel/{apic/nmi.c, apic/x2apic_uv_x.c, process.c}
as per Tejun.
 2011-01-07 17:02:58 -08:00
Linus Torvalds
23d69b09b7 Merge branch 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 
* 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: (33 commits)
  usb: don't use flush_scheduled_work()
  speedtch: don't abuse struct delayed_work
  media/video: don't use flush_scheduled_work()
  media/video: explicitly flush request_module work
  ioc4: use static work_struct for ioc4_load_modules()
  init: don't call flush_scheduled_work() from do_initcalls()
  s390: don't use flush_scheduled_work()
  rtc: don't use flush_scheduled_work()
  mmc: update workqueue usages
  mfd: update workqueue usages
  dvb: don't use flush_scheduled_work()
  leds-wm8350: don't use flush_scheduled_work()
  mISDN: don't use flush_scheduled_work()
  macintosh/ams: don't use flush_scheduled_work()
  vmwgfx: don't use flush_scheduled_work()
  tpm: don't use flush_scheduled_work()
  sonypi: don't use flush_scheduled_work()
  hvsi: don't use flush_scheduled_work()
  xen: don't use flush_scheduled_work()
  gdrom: don't use flush_scheduled_work()
  ...

Fixed up trivial conflict in drivers/media/video/bt8xx/bttv-input.c
as per Tejun.
 2011-01-07 16:58:04 -08:00
Christoph Lameter
7c83912062 vmstat: User per cpu atomics to avoid interrupt disable / enable 
Currently the operations to increment vm counters must disable interrupts
in order to not mess up their housekeeping of counters.

So use this_cpu_cmpxchg() to avoid the overhead. Since we can no longer
count on preremption being disabled we still have some minor issues.
The fetching of the counter thresholds is racy.
A threshold from another cpu may be applied if we happen to be
rescheduled on another cpu.  However, the following vmstat operation
will then bring the counter again under the threshold limit.

The operations for __xxx_zone_state are not changed since the caller
has taken care of the synchronization needs (and therefore the cycle
count is even less than the optimized version for the irq disable case
provided here).

The optimization using this_cpu_cmpxchg will only be used if the arch
supports efficient this_cpu_ops (must have CONFIG_CMPXCHG_LOCAL set!)

The use of this_cpu_cmpxchg reduces the cycle count for the counter
operations by %80 (inc_zone_page_state goes from 170 cycles to 32).

Signed-off-by: Christoph Lameter <cl@linux.com>
 2010-12-18 15:54:49 +01:00
Christoph Lameter
908ee0f122 vmstat: Use this_cpu_inc_return for vm statistics 
this_cpu_inc_return() saves us a memory access there. Code
size does not change.

V1->V2:
	- Fixed the location of the __per_cpu pointer attributes
	- Sparse checked
V2->V3:
	- Move fixes to __percpu attribute usage to earlier patch

Reviewed-by: Pekka Enberg <penberg@kernel.org>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
 2010-12-17 15:18:04 +01:00
Christoph Lameter
12938a9220 vmstat: Optimize zone counter modifications through the use of this cpu operations 
this cpu operations can be used to slightly optimize the function. The
changes will avoid some address calculations and replace them with the
use of the percpu segment register.

If one would have this_cpu_inc_return and this_cpu_dec_return then it
would be possible to optimize inc_zone_page_state and
dec_zone_page_state even more.

V1->V2:
	- Fix __dec_zone_state overflow handling
	- Use s8 variables for temporary storage.

V2->V3:
	- Put __percpu annotations in correct places.

Reviewed-by: Pekka Enberg <penberg@kernel.org>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
 2010-12-17 15:07:18 +01:00
Tejun Heo
afe2c511fb workqueue: convert cancel_rearming_delayed_work[queue]() users to cancel_delayed_work_sync() 
cancel_rearming_delayed_work[queue]() has been superceded by
cancel_delayed_work_sync() quite some time ago.  Convert all the
in-kernel users.  The conversions are completely equivalent and
trivial.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: "David S. Miller" <davem@davemloft.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Jeff Garzik <jgarzik@pobox.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Cc: netdev@vger.kernel.org
Cc: Anton Vorontsov <cbou@mail.ru>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Neil Brown <neilb@suse.de>
Cc: Alex Elder <aelder@sgi.com>
Cc: xfs-masters@oss.sgi.com
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: netfilter-devel@vger.kernel.org
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: linux-nfs@vger.kernel.org
 2010-12-15 10:56:11 +01:00
Wu Fengguang
e172662d11 vmstat: fix dirty threshold ordering 
The nr_dirty_[background_]threshold fields are misplaced before the
numa_* fields, and users will read strange values.

This is the right order.  Before patch, nr_dirty_background_threshold
will read as 0 (the value from numa_miss).

	numa_hit 128501
	numa_miss 0
	numa_foreign 0
	numa_interleave 7388
	numa_local 128501
	numa_other 0
	nr_dirty_threshold 144291
	nr_dirty_background_threshold 72145

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Michael Rubin <mrubin@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2010-12-02 14:51:14 -08:00
Wu Fengguang
ff8b16d7e1 vmstat: fix offset calculation on void* 
Fix regression introduced by commit 79da826aee ("writeback: report
dirty thresholds in /proc/vmstat").

The incorrect pointer arithmetic can result in problems like this:

  BUG: unable to handle kernel paging request at 07c06d16
  IP: [<c050c336>] strnlen+0x6/0x20
  Call Trace:
   [<c050a249>] ? string+0x39/0xe0
   [<c042be6b>] ? __wake_up_common+0x4b/0x80
   [<c050afcc>] ? vsnprintf+0x1ec/0x380
   [<c04b380e>] ? seq_printf+0x2e/0x60
   [<c04829a6>] ? vmstat_show+0x26/0x30
   [<c04b3bb6>] ? seq_read+0xa6/0x380
   [<c04b3b10>] ? seq_read+0x0/0x380
   [<c04d5d2f>] ? proc_reg_read+0x5f/0x90
   [<c049c4a1>] ? vfs_read+0xa1/0x140
   [<c04d5cd0>] ? proc_reg_read+0x0/0x90
   [<c049c981>] ? sys_read+0x41/0x70
   [<c0402bd0>] ? sysenter_do_call+0x12/0x26

Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2010-11-03 14:39:58 -04:00
Namhyung Kim
36deb0be31 vmstat: include compaction.h when CONFIG_COMPACTION 
This removes following warning from sparse:

 mm/vmstat.c:466:5: warning: symbol 'fragmentation_index' was not declared. Should it be static?

[akpm@linux-foundation.org: move the include to top-of-file]
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2010-10-26 16:52:10 -07:00
Michael Rubin
79da826aee writeback: report dirty thresholds in /proc/vmstat 
The kernel already exposes the user desired thresholds in /proc/sys/vm
with dirty_background_ratio and background_ratio.  But the kernel may
alter the number requested without giving the user any indication that is
the case.

Knowing the actual ratios the kernel is honoring can help app developers
understand how their buffered IO will be sent to the disk.

        $ grep threshold /proc/vmstat
        nr_dirty_threshold 409111
        nr_dirty_background_threshold 818223

Signed-off-by: Michael Rubin <mrubin@google.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2010-10-26 16:52:06 -07:00
Michael Rubin
ea941f0e2a writeback: add nr_dirtied and nr_written to /proc/vmstat 
To help developers and applications gain visibility into writeback
behaviour adding two entries to vm_stat_items and /proc/vmstat.  This will
allow us to track the "written" and "dirtied" counts.

   # grep nr_dirtied /proc/vmstat
   nr_dirtied 3747
   # grep nr_written /proc/vmstat
   nr_written 3618

Signed-off-by: Michael Rubin <mrubin@google.com>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2010-10-26 16:52:06 -07:00
Christoph Lameter
aa45484031 mm: page allocator: calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake 
Ordinarily watermark checks are based on the vmstat NR_FREE_PAGES as it is
cheaper than scanning a number of lists.  To avoid synchronization
overhead, counter deltas are maintained on a per-cpu basis and drained
both periodically and when the delta is above a threshold.  On large CPU
systems, the difference between the estimated and real value of
NR_FREE_PAGES can be very high.  If NR_FREE_PAGES is much higher than
number of real free page in buddy, the VM can allocate pages below min
watermark, at worst reducing the real number of pages to zero.  Even if
the OOM killer kills some victim for freeing memory, it may not free
memory if the exit path requires a new page resulting in livelock.

This patch introduces a zone_page_state_snapshot() function (courtesy of
Christoph) that takes a slightly more accurate view of an arbitrary vmstat
counter.  It is used to read NR_FREE_PAGES while kswapd is awake to avoid
the watermark being accidentally broken.  The estimate is not perfect and
may result in cache line bounces but is expected to be lighter than the
IPI calls necessary to continually drain the per-cpu counters while kswapd
is awake.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2010-09-09 18:57:25 -07:00
KAMEZAWA Hiroyuki
5ee28a4476 vmstat: update zone stat threshold when onlining a cpu 
refresh_zone_stat_thresholds() calculates parameter based on the number of
online cpus.  It's called at cpu offlining but needs to be called at
onlining, too.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2010-09-09 18:57:25 -07:00