linux/mm
Vlastimil Babka 3286222fc6 mm, slub: better heuristic for number of cpus when calculating slab order
When creating a new kmem cache, SLUB determines how large the slab pages
will based on number of inputs, including the number of CPUs in the
system.  Larger slab pages mean that more objects can be allocated/free
from per-cpu slabs before accessing shared structures, but also
potentially more memory can be wasted due to low slab usage and
fragmentation.  The rough idea of using number of CPUs is that larger
systems will be more likely to benefit from reduced contention, and also
should have enough memory to spare.

Number of CPUs used to be determined as nr_cpu_ids, which is number of
possible cpus, but on some systems many will never be onlined, thus
commit 045ab8c948 ("mm/slub: let number of online CPUs determine the
slub page order") changed it to nr_online_cpus().  However, for kmem
caches created early before CPUs are onlined, this may lead to
permamently low slab page sizes.

Vincent reports a regression [1] of hackbench on arm64 systems:

  "I'm facing significant performances regression on a large arm64
   server system (224 CPUs). Regressions is also present on small arm64
   system (8 CPUs) but in a far smaller order of magnitude

   On 224 CPUs system : 9 iterations of hackbench -l 16000 -g 16
   v5.11-rc4 : 9.135sec (+/- 0.45%)
   v5.11-rc4 + revert this patch: 3.173sec (+/- 0.48%)
   v5.10: 3.136sec (+/- 0.40%)"

Mel reports a regression [2] of hackbench on x86_64, with lockstat suggesting
page allocator contention:

  "i.e. the patch incurs a 7% to 32% performance penalty. This bisected
   cleanly yesterday when I was looking for the regression and then
   found the thread.

   Numerous caches change size. For example, kmalloc-512 goes from
   order-0 (vanilla) to order-2 with the revert.

   So mostly this is down to the number of times SLUB calls into the
   page allocator which only caches order-0 pages on a per-cpu basis"

Clearly num_online_cpus() doesn't work too early in bootup.  We could
change the order dynamically in a memory hotplug callback, but runtime
order changing for existing kmem caches has been already shown as
dangerous, and removed in 32a6f409b6 ("mm, slub: remove runtime
allocation order changes").

It could be resurrected in a safe manner with some effort, but to fix
the regression we need something simpler.

We could use num_present_cpus() that should be the number of physically
present CPUs even before they are onlined.  That would work for PowerPC
[3], which triggered the original commit, but that still doesn't work on
arm64 [4] as explained in [5].

So this patch tries to determine the best available value without
specific arch knowledge.

 - num_present_cpus() if the number is larger than 1, as that means the
   arch is likely setting it properly

 - nr_cpu_ids otherwise

This should fix the reported regressions while also keeping the effect
of 045ab8c948 for PowerPC systems.  It's possible there are
configurations where num_present_cpus() is 1 during boot while
nr_cpu_ids is at the same time bloated, so these (if they exist) would
keep the large orders based on nr_cpu_ids as was before 045ab8c948.

[1] https://lore.kernel.org/linux-mm/CAKfTPtA_JgMf_+zdFbcb_V9rM7JBWNPjAz9irgwFj7Rou=xzZg@mail.gmail.com/
[2] https://lore.kernel.org/linux-mm/20210128134512.GF3592@techsingularity.net/
[3] https://lore.kernel.org/linux-mm/20210123051607.GC2587010@in.ibm.com/
[4] https://lore.kernel.org/linux-mm/CAKfTPtAjyVmS5VYvU6DBxg4-JEo5bdmWbngf-03YsY18cmWv_g@mail.gmail.com/
[5] https://lore.kernel.org/linux-mm/20210126230305.GD30941@willie-the-truck/

Link: https://lkml.kernel.org/r/20210208134108.22286-1-vbabka@suse.cz
Fixes: 045ab8c948 ("mm/slub: let number of online CPUs determine the slub page order")
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Vincent Guittot <vincent.guittot@linaro.org>
Reported-by: Mel Gorman <mgorman@techsingularity.net>
Tested-by: Mel Gorman <mgorman@techsingularity.net>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Jann Horn <jannh@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Will Deacon <will@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-02-10 11:19:27 -08:00
..
kasan kasan: fix stack traces dependency for HW_TAGS 2021-02-09 17:26:44 -08:00
backing-dev.c mm:backing-dev: use sysfs_emit in macro defining functions 2020-12-15 12:13:47 -08:00
balloon_compaction.c mm/balloon_compaction: suppress allocation warnings 2019-09-04 07:42:01 -04:00
cleancache.c Driver Core and debugfs changes for 5.3-rc1 2019-07-12 12:24:03 -07:00
cma_debug.c debugfs: make sure we can remove u32_array files cleanly 2020-07-10 13:54:00 -07:00
cma.c mm: cma: improve pr_debug log in cma_release() 2020-12-15 12:13:46 -08:00
cma.h mm: cma: use CMA_MAX_NAME to define the length of cma name array 2020-09-01 09:19:43 +02:00
compaction.c mm, compaction: move high_pfn to the for loop scope 2021-02-05 11:03:47 -08:00
debug_page_ref.c
debug_vm_pgtable.c mm/debug_vm_pgtable: avoid doing memory allocation with pgtable_t mapped. 2020-10-16 11:11:14 -07:00
debug.c mm: memcontrol: Use helpers to read page's memcg data 2020-12-02 18:28:05 -08:00
dmapool.c mm/dmapool.c: replace hard coded function name with __func__ 2020-10-13 18:38:32 -07:00
early_ioremap.c mm/early_ioremap.c: use %pa to print resource_size_t variables 2020-01-31 10:30:38 -08:00
fadvise.c mm, fadvise: improve the expensive remote LRU cache draining after FADV_DONTNEED 2020-10-13 18:38:29 -07:00
failslab.c mm/failslab.c: by default, do not fail allocations with direct reclaim only 2019-07-12 11:05:43 -07:00
filemap.c mm/filemap: add missing mem_cgroup_uncharge() to __add_to_page_cache_locked() 2021-02-05 11:03:47 -08:00
frame_vector.c mmap locking API: convert mmap_sem comments 2020-06-09 09:39:14 -07:00
frontswap.c mm/frontswap: mark various intentional data races 2020-08-14 19:56:56 -07:00
gup_test.c mm/gup_test.c: mark gup_test_init as __init function 2020-12-15 12:13:38 -08:00
gup_test.h selftests/vm: gup_test: introduce the dump_pages() sub-test 2020-12-15 12:13:38 -08:00
gup.c Merge branch 'akpm' (patches from Andrew) 2020-12-15 12:53:37 -08:00
highmem.c mm/highmem: prepare for overriding set_pte_at() 2021-01-24 10:34:52 -08:00
hmm.c mm: do page fault accounting in handle_mm_fault 2020-08-12 10:58:02 -07:00
huge_memory.c mm: thp: fix MADV_REMOVE deadlock on shmem THP 2021-02-05 11:03:47 -08:00
hugetlb_cgroup.c hugetlb_cgroup: fix offline of hugetlb cgroup with reservations 2020-12-06 10:19:07 -08:00
hugetlb.c mm: hugetlb: fix missing put_page in gather_surplus_pages() 2021-02-05 11:03:47 -08:00
hwpoison-inject.c mm,hwpoison-inject: don't pin for hwpoison_filter 2020-10-16 11:11:16 -07:00
init-mm.c mm/gup: prevent gup_fast from racing with COW during fork 2020-12-15 12:13:39 -08:00
internal.h mm, page_alloc: disable pcplists during memory offline 2020-12-15 12:13:43 -08:00
interval_tree.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 248 2019-06-19 17:09:08 +02:00
ioremap.c mm: move p?d_alloc_track to separate header file 2020-08-07 11:33:26 -07:00
Kconfig mm/Kconfig: fix spelling mistake "whats" -> "what's" 2020-12-19 11:25:41 -08:00
Kconfig.debug mm, page_poison: remove CONFIG_PAGE_POISONING_ZERO 2020-12-15 12:13:46 -08:00
khugepaged.c mm: fix some spelling mistakes in comments 2020-12-15 22:46:19 -08:00
kmemleak.c mm/kmemleak: rely on rcu for task stack scanning 2020-10-13 18:38:27 -07:00
ksm.c mm: cleanup kstrto*() usage 2020-12-15 12:13:47 -08:00
list_lru.c mm: list_lru: set shrinker map bit when child nr_items is not zero 2020-12-06 10:19:07 -08:00
maccess.c uaccess: add force_uaccess_{begin,end} helpers 2020-08-12 10:57:59 -07:00
madvise.c mm,memory_failure: always pin the page in madvise_inject_error 2020-12-15 12:13:44 -08:00
Makefile mm: mmap_lock: add tracepoints around lock acquisition 2020-12-15 12:13:41 -08:00
mapping_dirty_helpers.c mm/mapping_dirty_helpers: enhance the kernel-doc markups 2020-12-15 12:13:41 -08:00
memblock.c memblock: do not start bottom-up allocations with kernel_end 2021-02-05 11:03:47 -08:00
memcontrol.c Revert "mm: memcontrol: avoid workload stalls when lowering memory.high" 2021-02-09 17:26:44 -08:00
memfd.c mm: page cache: store only head pages in i_pages 2019-09-24 15:54:08 -07:00
memory_hotplug.c mm: memmap defer init doesn't work as expected 2020-12-29 15:36:49 -08:00
memory-failure.c mm: fix page reference leak in soft_offline_page() 2021-01-24 10:34:52 -08:00
memory.c mm: generalise COW SMC TLB flushing race comment 2020-12-29 15:36:49 -08:00
mempolicy.c mm: migrate: initialize err in do_migrate_pages 2021-01-12 18:12:54 -08:00
mempool.c kasan, mm: rename kasan_poison_kfree 2020-12-22 12:55:09 -08:00
memremap.c mm/mremap_pages: fix static key devmap_managed_key updates 2020-11-02 12:14:18 -08:00
memtest.c
migrate.c mm: migrate: do not migrate HugeTLB page whose refcount is one 2021-02-05 11:03:47 -08:00
mincore.c mm: factor find_get_incore_page out of mincore_page 2020-10-13 18:38:29 -07:00
mlock.c mm/lru: introduce relock_page_lruvec() 2020-12-15 14:48:04 -08:00
mm_init.c mm: fix fall-through warnings for Clang 2020-12-15 12:13:47 -08:00
mmap_lock.c mm: mmap_lock: add tracepoints around lock acquisition 2020-12-15 12:13:41 -08:00
mmap.c UAPI Changes: 2020-12-18 12:38:28 -08:00
mmu_gather.c mmap locking API: convert mmap_sem comments 2020-06-09 09:39:14 -07:00
mmu_notifier.c mm: track mmu notifiers in fs_reclaim_acquire/release 2020-12-15 12:13:41 -08:00
mmzone.c mm/lru: replace pgdat lru_lock with lruvec lock 2020-12-15 14:48:04 -08:00
mprotect.c mm: Add 'mprotect' hook to struct vm_operations_struct 2020-11-17 14:36:14 +01:00
mremap.c mm/mremap: fix BUILD_BUG_ON() error in get_extent 2021-02-09 17:26:44 -08:00
msync.c mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
nommu.c mm: cleanup: remove unused tsk arg from __access_remote_vm 2020-12-15 12:13:40 -08:00
oom_kill.c mm/oom_kill: change comment and rename is_dump_unreclaim_slabs() 2020-12-15 12:13:45 -08:00
page_alloc.c Revert "mm: fix initialization of struct page for holes in memory layout" 2021-01-26 10:39:46 -08:00
page_counter.c mm/page_counter: use page_counter_read in page_counter_set_max 2020-12-15 12:13:40 -08:00
page_ext.c mm: fix some spelling mistakes in comments 2020-12-15 22:46:19 -08:00
page_idle.c mm: page_idle_get_page() does not need lru_lock 2020-12-15 14:48:03 -08:00
page_io.c mm: memcontrol: Use helpers to read page's memcg data 2020-12-02 18:28:05 -08:00
page_isolation.c mm/page_isolation: do not isolate the max order page 2020-12-15 12:13:45 -08:00
page_owner.c mm/page_owner: record timestamp and pid 2020-12-15 12:13:38 -08:00
page_poison.c kasan, mm: reset tags when accessing metadata 2020-12-22 12:55:08 -08:00
page_reporting.c mm: rename page_order() to buddy_order() 2020-10-16 11:11:19 -07:00
page_reporting.h mm: introduce include/linux/pgtable.h 2020-06-09 09:39:13 -07:00
page_vma_mapped.c mm/page_vma_mapped.c: add colon to fix kernel-doc markups error for check_pte 2020-12-15 12:13:41 -08:00
page-writeback.c mm: make wait_on_page_writeback() wait for multiple pending writebacks 2021-01-05 11:33:00 -08:00
pagewalk.c mmap locking API: convert mmap_sem comments 2020-06-09 09:39:14 -07:00
percpu-internal.h mm: memcg/percpu: account percpu memory to memory cgroups 2020-08-12 10:57:55 -07:00
percpu-km.c mm: memcg/percpu: account percpu memory to memory cgroups 2020-08-12 10:57:55 -07:00
percpu-stats.c mm: memcg/percpu: account percpu memory to memory cgroups 2020-08-12 10:57:55 -07:00
percpu-vm.c mm: memcg/percpu: account percpu memory to memory cgroups 2020-08-12 10:57:55 -07:00
percpu.c percpu: convert flexible array initializers to use struct_size() 2020-10-30 23:02:28 +00:00
pgalloc-track.h mm: move p?d_alloc_track to separate header file 2020-08-07 11:33:26 -07:00
pgtable-generic.c mm: introduce include/linux/pgtable.h 2020-06-09 09:39:13 -07:00
process_vm_access.c mm/process_vm_access.c: include compat.h 2021-01-12 18:12:54 -08:00
ptdump.c kasan, arm64: expand CONFIG_KASAN checks 2020-12-22 12:55:08 -08:00
readahead.c mm: use limited read-ahead to satisfy read 2020-10-17 13:49:08 -06:00
rmap.c mm/lru: revise the comments of lru_lock 2020-12-15 14:48:04 -08:00
rodata_test.c mm/rodata_test.c: fix missing function declaration 2020-08-21 09:52:53 -07:00
shmem.c mm: shmem: convert shmem_enabled_show to use sysfs_emit_at 2020-12-15 12:13:47 -08:00
shuffle.c mm: rename page_order() to buddy_order() 2020-10-16 11:11:19 -07:00
shuffle.h mm/shuffle: remove dynamic reconfiguration 2020-08-07 11:33:29 -07:00
slab_common.c kasan, mm: allow cache merging with no metadata 2020-12-22 12:55:09 -08:00
slab.c mm: introduce debug_pagealloc_{map,unmap}_pages() helpers 2020-12-15 12:13:43 -08:00
slab.h Networking updates for 5.11 2020-12-15 13:22:29 -08:00
slob.c mm: extract might_alloc() debug check 2020-12-15 12:13:41 -08:00
slub.c mm, slub: better heuristic for number of cpus when calculating slab order 2021-02-10 11:19:27 -08:00
sparse-vmemmap.c mm/sparse: only sub-section aligned range would be populated 2020-08-07 11:33:27 -07:00
sparse.c mm/memory_hotplug: guard more declarations by CONFIG_MEMORY_HOTPLUG 2020-10-16 11:11:18 -07:00
swap_cgroup.c mm: memcontrol: make swap tracking an integral part of memory control 2020-06-03 20:09:48 -07:00
swap_slots.c mm/swap_slots.c: remove always zero and unused return value of enable_swap_slots_cache() 2020-10-13 18:38:30 -07:00
swap_state.c mm: use sysfs_emit for struct kobject * uses 2020-12-15 12:13:47 -08:00
swap.c mm/lru: introduce relock_page_lruvec() 2020-12-15 14:48:04 -08:00
swapfile.c mm: fix a race on nr_swap_pages 2020-12-15 22:46:15 -08:00
truncate.c mm: fix kernel-doc markups 2020-12-15 12:13:47 -08:00
usercopy.c mm/usercopy.c: delete duplicated word 2020-08-12 10:57:58 -07:00
userfaultfd.c mm/vmscan: protect the workingset on anonymous LRU 2020-08-12 10:57:55 -07:00
util.c mm: introduce vma_set_file function v5 2020-11-19 10:36:36 +01:00
vmacache.c kernel: better document the use_mm/unuse_mm API contract 2020-06-10 19:14:18 -07:00
vmalloc.c mm/vmalloc.c: fix potential memory leak 2021-01-12 18:12:54 -08:00
vmpressure.c mm: vmpressure: use mem_cgroup_is_root API 2020-04-02 09:35:31 -07:00
vmscan.c mm: don't put pinned pages into the swap cache 2021-01-17 12:08:04 -08:00
vmstat.c arm: remove CONFIG_ARCH_HAS_HOLES_MEMORYMODEL 2020-12-15 12:13:42 -08:00
workingset.c Merge branch 'akpm' (patches from Andrew) 2020-12-15 14:55:10 -08:00
z3fold.c z3fold: remove preempt disabled sections for RT 2020-12-15 12:13:45 -08:00
zbud.c mm/zbud: remove redundant initialization 2020-10-13 18:38:34 -07:00
zpool.c mm/zpool.c: delete duplicated word and fix grammar 2020-08-12 10:57:58 -07:00
zsmalloc.c mm/zsmalloc.c: rework the list_add code in insert_zspage() 2020-12-15 12:13:46 -08:00
zswap.c mm/zswap: move to use crypto_acomp API for hardware acceleration 2020-12-15 12:13:46 -08:00