Right now, if you inadvertently pass NULL to kmem_cache_create() at boot
time, it crashes much later after boot somewhere deep inside sysfs which
makes it very non obvious to figure out what's going on.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This build bug:
mm/slub.c: In function 'kmem_cache_open':
mm/slub.c:2476: error: 'disable_higher_order_debug' undeclared (first use in this function)
mm/slub.c:2476: error: (Each undeclared identifier is reported only once
mm/slub.c:2476: error: for each function it appears in.)
Triggers because there's no !CONFIG_SLUB_DEBUG definition for
disable_higher_order_debug.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (46 commits)
powerpc64: convert to dynamic percpu allocator
sparc64: use embedding percpu first chunk allocator
percpu: kill lpage first chunk allocator
x86,percpu: use embedding for 64bit NUMA and page for 32bit NUMA
percpu: update embedding first chunk allocator to handle sparse units
percpu: use group information to allocate vmap areas sparsely
vmalloc: implement pcpu_get_vm_areas()
vmalloc: separate out insert_vmalloc_vm()
percpu: add chunk->base_addr
percpu: add pcpu_unit_offsets[]
percpu: introduce pcpu_alloc_info and pcpu_group_info
percpu: move pcpu_lpage_build_unit_map() and pcpul_lpage_dump_cfg() upward
percpu: add @align to pcpu_fc_alloc_fn_t
percpu: make @dyn_size mandatory for pcpu_setup_first_chunk()
percpu: drop @static_size from first chunk allocators
percpu: generalize first chunk allocator selection
percpu: build first chunk allocators selectively
percpu: rename 4k first chunk allocator to page
percpu: improve boot messages
percpu: fix pcpu_reclaim() locking
...
Fix trivial conflict as by Tejun Heo in kernel/sched.c
When SLAB_POISON is used and slab_pad_check() finds an overwrite of the
slab padding, we call restore_bytes() on the whole slab, not only
on the padding.
Acked-by: Christoph Lameer <cl@linux-foundation.org>
Reported-by: Zdenek Kabelac <zdenek.kabelac@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
kmem_cache_destroy() should call rcu_barrier() *after* kmem_cache_close() and
*before* sysfs_slab_remove() or risk rcu_free_slab() being called after
kmem_cache is deleted (kfreed).
rmmod nf_conntrack can crash the machine because it has to kmem_cache_destroy()
a SLAB_DESTROY_BY_RCU enabled cache.
Cc: <stable@kernel.org>
Reported-by: Zdenek Kabelac <zdenek.kabelac@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
When CONFIG_SLUB_DEBUG is enabled, sysfs_slab_add should unlink and put the
kobject if sysfs_create_group failed. Otherwise, sysfs_slab_add returns error
then free kmem_cache s, thus memory of s->kobj is leaked.
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
If the minalign is 64 bytes, then the 96 byte cache should not be created
because it would conflict with the 128 byte cache.
If the minalign is 256 bytes, patching the size_index table should not
result in a buffer overrun.
The calculation "(i - 1) / 8" used to access size_index[] is moved to
a separate function as suggested by Christoph Lameter.
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
SLUB does not support writes to /proc/slabinfo so there should not be write
permission to do that either.
Signed-off-by: WANG Cong <amwang@redhat.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Conflicts:
arch/sparc/kernel/smp_64.c
arch/x86/kernel/cpu/perf_counter.c
arch/x86/kernel/setup_percpu.c
drivers/cpufreq/cpufreq_ondemand.c
mm/percpu.c
Conflicts in core and arch percpu codes are mostly from commit
ed78e1e078dd44249f88b1dd8c76dafb39567161 which substituted many
num_possible_cpus() with nr_cpu_ids. As for-next branch has moved all
the first chunk allocators into mm/percpu.c, the changes are moved
from arch code to mm/percpu.c.
Signed-off-by: Tejun Heo <tj@kernel.org>
kmem_cache->align records the original align parameter value specified
by users. Function calculate_alignment might change it based on cache
line size. So change kmem_cache->align correspondingly.
Signed-off-by: Zhang Yanmin <yanmin_zhang@linux.intel.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
This patch moves the masking of debugging flags which increase a cache's
min order due to metadata when `slub_debug=O' is used from
kmem_cache_flags() to kmem_cache_open().
Instead of defining the maximum metadata size increase in a preprocessor
macro, this approach uses the cache's ->size and ->objsize members to
determine if the min order increased due to debugging options. If so,
the flags specified in the more appropriately named DEBUG_METADATA_FLAGS
are masked off.
This approach was suggested by Christoph Lameter
<cl@linux-foundation.org>.
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
When debugging is enabled, slub requires that additional metadata be
stored in slabs for certain options: SLAB_RED_ZONE, SLAB_POISON, and
SLAB_STORE_USER.
Consequently, it may require that the minimum possible slab order needed
to allocate a single object be greater when using these options. The
most notable example is for objects that are PAGE_SIZE bytes in size.
Higher minimum slab orders may cause page allocation failures when oom or
under heavy fragmentation.
This patch adds a new slub_debug option, which disables debugging by
default for caches that would have resulted in higher minimum orders:
slub_debug=O
When this option is used on systems with 4K pages, kmalloc-4096, for
example, will not have debugging enabled by default even if
CONFIG_SLUB_DEBUG_ON is defined because it would have resulted in a
order-1 minimum slab order.
Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
The kmalloc_large() and kmalloc_large_node() functions were missed when
adding the kmemleak hooks to the slub allocator. However, they should be
traced to avoid false positives.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Pull linus#master to merge PER_CPU_DEF_ATTRIBUTES and alpha build fix
changes. As alpha in percpu tree uses 'weak' attribute instead of
inline assembly, there's no need for __used attribute.
Conflicts:
arch/alpha/include/asm/percpu.h
arch/mn10300/kernel/vmlinux.lds.S
include/linux/percpu-defs.h
Jesper noted that kmem_cache_destroy() invokes synchronize_rcu() rather than
rcu_barrier() in the SLAB_DESTROY_BY_RCU case, which could result in RCU
callbacks accessing a kmem_cache after it had been destroyed.
Cc: <stable@kernel.org>
Acked-by: Matt Mackall <mpm@selenic.com>
Reported-by: Jesper Dangaard Brouer <hawk@comx.dk>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
SLUB uses higher order allocations by default but falls back to small
orders under memory pressure. Make sure the GFP mask used in the initial
allocation doesn't include __GFP_NOFAIL.
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently, the following three different ways to define percpu arrays
are in use.
1. DEFINE_PER_CPU(elem_type[array_len], array_name);
2. DEFINE_PER_CPU(elem_type, array_name[array_len]);
3. DEFINE_PER_CPU(elem_type, array_name)[array_len];
Unify to #1 which correctly separates the roles of the two parameters
and thus allows more flexibility in the way percpu variables are
defined.
[ Impact: cleanup ]
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: linux-mm@kvack.org
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: David S. Miller <davem@davemloft.net>
The page allocator also needs the masking of gfp flags during boot,
so this moves it out of slab/slub and uses it with the page allocator
as well.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* akpm: (182 commits)
fbdev: bf54x-lq043fb: use kzalloc over kmalloc/memset
fbdev: *bfin*: fix __dev{init,exit} markings
fbdev: *bfin*: drop unnecessary calls to memset
fbdev: bfin-t350mcqb-fb: drop unused local variables
fbdev: blackfin has __raw I/O accessors, so use them in fb.h
fbdev: s1d13xxxfb: add accelerated bitblt functions
tcx: use standard fields for framebuffer physical address and length
fbdev: add support for handoff from firmware to hw framebuffers
intelfb: fix a bug when changing video timing
fbdev: use framebuffer_release() for freeing fb_info structures
radeon: P2G2CLK_ALWAYS_ONb tested twice, should 2nd be P2G2CLK_DAC_ALWAYS_ONb?
s3c-fb: CPUFREQ frequency scaling support
s3c-fb: fix resource releasing on error during probing
carminefb: fix possible access beyond end of carmine_modedb[]
acornfb: remove fb_mmap function
mb862xxfb: use CONFIG_OF instead of CONFIG_PPC_OF
mb862xxfb: restrict compliation of platform driver to PPC
Samsung SoC Framebuffer driver: add Alpha Channel support
atmel-lcdc: fix pixclock upper bound detection
offb: use framebuffer_alloc() to allocate fb_info struct
...
Manually fix up conflicts due to kmemcheck in mm/slab.c
num_online_nodes() is called in a number of places but most often by the
page allocator when deciding whether the zonelist needs to be filtered
based on cpusets or the zonelist cache. This is actually a heavy function
and touches a number of cache lines.
This patch stores the number of online nodes at boot time and updates the
value when nodes get onlined and offlined. The value is then used in a
number of important paths in place of num_online_nodes().
[rientjes@google.com: do not override definition of node_set_online() with macro]
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This adds support for tracking the initializedness of memory that
was allocated with the page allocator. Highmem requests are not
tracked.
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
[build fix for !CONFIG_KMEMCHECK]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
[rebased for mainline inclusion]
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Recent change to use slab allocations earlier exposed a bug where
SLUB can call schedule_work and try to call sysfs before it is
safe to do so.
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Parts of this patch were contributed by Pekka Enberg but merged for
atomicity.
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Vegard Nossum <vegardno@ifi.uio.no>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
[rebased for mainline inclusion]
Signed-off-by: Vegard Nossum <vegardno@ifi.uio.no>
We must check for __GFP_NOFAIL like the page allocator does; otherwise we end
up with false positives. While at it, add the printk_ratelimit() check in SLUB
as well.
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Fix this build error when CONFIG_SLUB_DEBUG is not set:
mm/slub.c: In function 'slab_out_of_memory':
mm/slub.c:1551: error: 'struct kmem_cache_node' has no member named 'nr_slabs'
mm/slub.c:1552: error: 'struct kmem_cache_node' has no member named 'total_objects'
[ penberg@cs.helsinki.fi: cleanups ]
Signed-off-by: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
As explained by Benjamin Herrenschmidt:
Oh and btw, your patch alone doesn't fix powerpc, because it's missing
a whole bunch of GFP_KERNEL's in the arch code... You would have to
grep the entire kernel for things that check slab_is_available() and
even then you'll be missing some.
For example, slab_is_available() didn't always exist, and so in the
early days on powerpc, we used a mem_init_done global that is set form
mem_init() (not perfect but works in practice). And we still have code
using that to do the test.
Therefore, mask out __GFP_WAIT, __GFP_IO, and __GFP_FS in the slab allocators
in early boot code to avoid enabling interrupts.
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
* 'for-linus' of git://linux-arm.org/linux-2.6:
kmemleak: Add the corresponding MAINTAINERS entry
kmemleak: Simple testing module for kmemleak
kmemleak: Enable the building of the memory leak detector
kmemleak: Remove some of the kmemleak false positives
kmemleak: Add modules support
kmemleak: Add kmemleak_alloc callback from alloc_large_system_hash
kmemleak: Add the vmalloc memory allocation/freeing hooks
kmemleak: Add the slub memory allocation/freeing hooks
kmemleak: Add the slob memory allocation/freeing hooks
kmemleak: Add the slab memory allocation/freeing hooks
kmemleak: Add documentation on the memory leak detector
kmemleak: Add the base support
Manual conflict resolution (with the slab/earlyboot changes) in:
drivers/char/vt.c
init/main.c
mm/slab.c
This patch makes kmalloc() available earlier in the boot sequence so we can get
rid of some bootmem allocations. The bulk of the changes are due to
kmem_cache_init() being called with interrupts disabled which requires some
changes to allocator boostrap code.
Note: 32-bit x86 does WP protect test in mem_init() so we must setup traps
before we call mem_init() during boot as reported by Ingo Molnar:
We have a hard crash in the WP-protect code:
[ 0.000000] Checking if this processor honours the WP bit even in supervisor mode...BUG: Int 14: CR2 ffcff000
[ 0.000000] EDI 00000188 ESI 00000ac7 EBP c17eaf9c ESP c17eaf8c
[ 0.000000] EBX 000014e0 EDX 0000000e ECX 01856067 EAX 00000001
[ 0.000000] err 00000003 EIP c10135b1 CS 00000060 flg 00010002
[ 0.000000] Stack: c17eafa8 c17fd410 c16747bc c17eafc4 c17fd7e5 000011fd f8616000 c18237cc
[ 0.000000] 00099800 c17bb000 c17eafec c17f1668 000001c5 c17f1322 c166e039 c1822bf0
[ 0.000000] c166e033 c153a014 c18237cc 00020800 c17eaff8 c17f106a 00020800 01ba5003
[ 0.000000] Pid: 0, comm: swapper Not tainted 2.6.30-tip-02161-g7a74539-dirty #52203
[ 0.000000] Call Trace:
[ 0.000000] [<c15357c2>] ? printk+0x14/0x16
[ 0.000000] [<c10135b1>] ? do_test_wp_bit+0x19/0x23
[ 0.000000] [<c17fd410>] ? test_wp_bit+0x26/0x64
[ 0.000000] [<c17fd7e5>] ? mem_init+0x1ba/0x1d8
[ 0.000000] [<c17f1668>] ? start_kernel+0x164/0x2f7
[ 0.000000] [<c17f1322>] ? unknown_bootoption+0x0/0x19c
[ 0.000000] [<c17f106a>] ? __init_begin+0x6a/0x6f
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by Linus Torvalds <torvalds@linux-foundation.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
This patch adds the callbacks to kmemleak_(alloc|free) functions from the
slub allocator.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Reviewed-by: Pekka Enberg <penberg@cs.helsinki.fi>
As suggested by Mel Gorman, add out-of-memory diagnostics to the SLUB allocator
to make debugging OOM conditions easier. This patch helped hunt down a nasty
OOM issue that popped up every now that was caused by SLUB debugging code which
forced 4096 byte allocations to use order 1 pages even in the fallback case.
An example print out looks like this:
<snip page allocator out-of-memory message>
SLUB: Unable to allocate memory on node -1 (gfp=20)
cache: kmalloc-4096, object size: 4096, buffer size: 4168, default order: 3, min order: 1
node 0: slabs: 95, objs: 665, free: 0
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
* 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (244 commits)
Revert "x86, bts: reenable ptrace branch trace support"
tracing: do not translate event helper macros in print format
ftrace/documentation: fix typo in function grapher name
tracing/events: convert block trace points to TRACE_EVENT(), fix !CONFIG_BLOCK
tracing: add protection around module events unload
tracing: add trace_seq_vprint interface
tracing: fix the block trace points print size
tracing/events: convert block trace points to TRACE_EVENT()
ring-buffer: fix ret in rb_add_time_stamp
ring-buffer: pass in lockdep class key for reader_lock
tracing: add annotation to what type of stack trace is recorded
tracing: fix multiple use of __print_flags and __print_symbolic
tracing/events: fix output format of user stack
tracing/events: fix output format of kernel stack
tracing/trace_stack: fix the number of entries in the header
ring-buffer: discard timestamps that are at the start of the buffer
ring-buffer: try to discard unneeded timestamps
ring-buffer: fix bug in ring_buffer_discard_commit
ftrace: do not profile functions when disabled
tracing: make trace pipe recognize latency format flag
...
SLUB does not correctly account reclaim_state.reclaimed_slab, so it will
break memory reclaim. Account it like SLAB does.
Cc: stable@kernel.org
Cc: linux-mm@kvack.org
Cc: Matt Mackall <mpm@selenic.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
slub_max_order may not be equal to or greater than MAX_ORDER.
Additionally, if a single object cannot be placed in a slab of
slub_max_order, it still must allocate slabs below MAX_ORDER.
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Impact: refactor code for future changes
Current kmemtrace.h is used both as header file of kmemtrace and kmem's
tracepoints definition.
Tracepoints' definition file may be used by other code, and should only have
definition of tracepoint.
We can separate include/trace/kmemtrace.h into 2 files:
include/linux/kmemtrace.h: header file for kmemtrace
include/trace/kmem.h: definition of kmem tracepoints
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Acked-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <49DEE68A.5040902@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: also output kfree(NULL) entries
This patch moves the trace_kfree() calls before the ZERO_OR_NULL_PTR
check so that we can trace call-sites that call kfree() with NULL many
times which might be an indication of a bug.
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
LKML-Reference: <1237971957.30175.18.camel@penberg-laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
kmemtrace now uses tracepoints instead of markers. We no longer need to
use format specifiers to pass arguments.
Signed-off-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
[ folded: Use the new TP_PROTO and TP_ARGS to fix the build. ]
[ folded: fix build when CONFIG_KMEMTRACE is disabled. ]
[ folded: define tracepoints when CONFIG_TRACEPOINTS is enabled. ]
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
LKML-Reference: <ae61c0f37156db8ec8dc0d5778018edde60a92e3.1237813499.git.eduard.munteanu@linux360.ro>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Use get_track() in set_track()
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
As suggested by Christoph Lameter, rename calculate_min_partial() to
set_min_partial() as the function doesn't really do any calculations.
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Now that a cache's min_partial has been moved to struct kmem_cache, it's
possible to easily tune it from userspace by adding a sysfs attribute.
It may not be desirable to keep a large number of partial slabs around
if a cache is used infrequently and memory, especially when constrained
by a cgroup, is scarce. It's better to allow userspace to set the
minimum policy per cache instead of relying explicitly on
kmem_cache_shrink().
The memory savings from simply moving min_partial from struct
kmem_cache_node to struct kmem_cache is obviously not significant
(unless maybe you're from SGI or something), at the largest it's
# allocated caches * (MAX_NUMNODES - 1) * sizeof(unsigned long)
The true savings occurs when userspace reduces the number of partial
slabs that would otherwise be wasted, especially on machines with a
large number of nodes (ia64 with CONFIG_NODES_SHIFT at 10 for default?).
As well as the kernel estimates ideal values for n->min_partial and
ensures it's within a sane range, userspace has no other input other
than writing to /sys/kernel/slab/cache/shrink.
There simply isn't any better heuristic to add when calculating the
partial values for a better estimate that works for all possible caches.
And since it's currently a static value, the user really has no way of
reclaiming that wasted space, which can be significant when constrained
by a cgroup (either cpusets or, later, memory controller slab limits)
without shrinking it entirely.
This also allows the user to specify that increased fragmentation and
more partial slabs are actually desired to avoid the cost of allocating
new slabs at runtime for specific caches.
There's also no reason why this should be a per-struct kmem_cache_node
value in the first place. You could argue that a machine would have
such node size asymmetries that it should be specified on a per-node
basis, but we know nobody is doing that right now since it's a purely
static value at the moment and there's no convenient way to tune that
via slub's sysfs interface.
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Although it allows for better cacheline use, it is unnecessary to save a
copy of the cache's min_partial value in each kmem_cache_node.
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
