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2a791f4412
linux/mm
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Mel Gorman 2a791f4412 mm/page_alloc: do not prefetch buddies during bulk free 
free_pcppages_bulk() has taken two passes through the pcp lists since
commit 0a5f4e5b45 ("mm/free_pcppages_bulk: do not hold lock when
picking pages to free") due to deferring the cost of selecting PCP lists
until the zone lock is held.

As the list processing now takes place under the zone lock, it's less
clear that this will always benefit for two reasons.

1. There is a guaranteed cost to calculating the buddy which definitely
   has to be calculated again. However, as the zone lock is held and
   there is no deferring of buddy merging, there is no guarantee that the
   prefetch will have completed when the second buddy calculation takes
   place and buddies are being merged.  With or without the prefetch, there
   may be further stalls depending on how many pages get merged. In other
   words, a stall due to merging is inevitable and at best only one stall
   might be avoided at the cost of calculating the buddy location twice.

2. As the zone lock is held, prefetch_nr makes less sense as once
   prefetch_nr expires, the cache lines of interest have already been
   merged.

The main concern is that there is a definite cost to calculating the
buddy location early for the prefetch and it is a "maybe win" depending
on whether the CPU prefetch logic and memory is fast enough.  Remove the
prefetch logic on the basis that reduced instructions in a path is
always a saving where as the prefetch might save one memory stall
depending on the CPU and memory.

In most cases, this has marginal benefit as the calculations are a small
part of the overall freeing of pages.  However, it was detectable on at
least one machine.

                              5.17.0-rc3             5.17.0-rc3
                    mm-highpcplimit-v2r1     mm-noprefetch-v1r1
Min       elapsed      630.00 (   0.00%)      610.00 (   3.17%)
Amean     elapsed      639.00 (   0.00%)      623.00 *   2.50%*
Max       elapsed      660.00 (   0.00%)      660.00 (   0.00%)

Link: https://lkml.kernel.org/r/20220221094119.15282-2-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Suggested-by: Aaron Lu <aaron.lu@intel.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Aaron Lu <aaron.lu@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
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>
2022-03-22 15:57:06 -07:00
..
damon mm/damon: hide kernel pointer from tracepoint event 2022-01-15 16:30:33 +02:00
kasan lib/stackdepot: always do filter_irq_stacks() in stack_depot_save() 2022-01-22 08:33:38 +02:00
kfence kfence: make test case compatible with run time set sample interval 2022-02-11 17:55:00 -08:00
backing-dev.c remove congestion tracking framework 2022-03-22 15:57:01 -07:00
balloon_compaction.c
bootmem_info.c bootmem: Use page->index instead of page->freelist 2022-01-06 12:27:03 +01:00
cma_debug.c
cma_sysfs.c
cma.c cma: factor out minimum alignment requirement 2022-03-22 15:57:05 -07:00
cma.h
compaction.c mm: compaction: fix the migration stats in trace_mm_compaction_migratepages() 2022-01-15 16:30:30 +02:00
debug_page_ref.c
debug_vm_pgtable.c mm/debug_vm_pgtable: remove pte entry from the page table 2022-02-04 09:25:04 -08:00
debug.c mm,fs: split dump_mapping() out from dump_page() 2022-01-15 16:30:26 +02:00
dmapool.c mm/dmapool.c: revert "make dma pool to use kmalloc_node" 2022-01-15 16:30:28 +02:00
early_ioremap.c mm/early_ioremap.c: remove redundant early_ioremap_shutdown() 2021-09-08 11:50:24 -07:00
fadvise.c remove inode_congested() 2022-03-22 15:57:01 -07:00
failslab.c
filemap.c tmpfs: do not allocate pages on read 2022-03-22 15:57:02 -07:00
folio-compat.c filemap: Add filemap_release_folio() 2022-01-04 13:15:34 -05:00
frontswap.c frontswap: remove support for multiple ops 2022-01-22 08:33:38 +02:00
gup_test.c
gup_test.h
gup.c mm/gup: remove unused get_user_pages_locked() 2022-03-22 15:57:01 -07:00
highmem.c Fixes for 5.16 folios: 2021-11-25 10:13:56 -08:00
hmm.c mm/hmm.c: allow VM_MIXEDMAP to work with hmm_range_fault 2022-01-15 16:30:31 +02:00
huge_memory.c mm: thp: fix wrong cache flush in remove_migration_pmd() 2022-03-22 15:57:04 -07:00
hugetlb_cgroup.c hugetlb: add hugetlb.*.numa_stat file 2022-01-15 16:30:29 +02:00
hugetlb_vmemmap.c mm: hugetlb: introduce CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON 2021-06-30 20:47:26 -07:00
hugetlb_vmemmap.h mm: hugetlb: introduce nr_free_vmemmap_pages in the struct hstate 2021-06-30 20:47:25 -07:00
hugetlb.c mm: hugetlb: fix missing cache flush in hugetlb_mcopy_atomic_pte() 2022-03-22 15:57:04 -07:00
hwpoison-inject.c mm: hwpoison: don't drop slab caches for offlining non-LRU page 2021-09-03 09:58:15 -07:00
init-mm.c mm: add setup_initial_init_mm() helper 2021-07-08 11:48:21 -07:00
internal.h mm/sparse: make mminit_validate_memmodel_limits() static 2022-03-22 15:57:05 -07:00
interval_tree.c
io-mapping.c
ioremap.c mm: move ioremap_page_range to vmalloc.c 2021-09-08 11:50:24 -07:00
Kconfig mm: enforce pageblock_order < MAX_ORDER 2022-03-22 15:57:06 -07:00
Kconfig.debug mm: page table check 2022-01-15 16:30:28 +02:00
khugepaged.c mm/page_table_check: check entries at pmd levels 2022-02-04 09:25:04 -08:00
kmemleak.c mm/kmemleak: avoid scanning potential huge holes 2022-02-04 09:25:05 -08:00
ksm.c mm: ksm: fix use-after-free kasan report in ksm_might_need_to_copy 2022-01-15 16:30:31 +02:00
list_lru.c mm: memcontrol: rename memcg_cache_id to memcg_kmem_id 2022-03-22 15:57:04 -07:00
maccess.c ARM: 9115/1: mm/maccess: fix unaligned copy_{from,to}_kernel_nofault 2021-08-20 11:39:25 +01:00
madvise.c mm: fix use-after-free when anon vma name is used after vma is freed 2022-03-05 11:08:32 -08:00
Makefile mm: remove cleancache 2022-01-22 08:33:38 +02:00
mapping_dirty_helpers.c mm: move tlb_flush_pending inline helpers to mm_inline.h 2022-01-15 16:30:27 +02:00
memblock.c memblock: use kfree() to release kmalloced memblock regions 2022-02-20 08:45:39 +02:00
memcontrol.c mm: memcontrol: fix cannot alloc the maximum memcg ID 2022-03-22 15:57:03 -07:00
memfd.c memfd: fix F_SEAL_WRITE after shmem huge page allocated 2022-03-05 11:08:32 -08:00
memory_hotplug.c treewide: Add missing includes masked by cgroup -> bpf dependency 2021-12-03 10:58:13 -08:00
memory-failure.c memory-failure: fetch compound_head after pgmap_pfn_valid() 2022-01-30 09:56:58 +02:00
memory.c mm/memory.c: use helper macro min and max in unmap_mapping_range_tree() 2022-03-22 15:57:05 -07:00
mempolicy.c mm: change lookup_node() to use get_user_pages_fast() 2022-03-22 15:57:01 -07:00
mempool.c mm: remove spurious blkdev.h includes 2021-10-18 06:17:01 -06:00
memremap.c mm/memremap: avoid calling kasan_remove_zero_shadow() for device private memory 2022-03-22 15:57:01 -07:00
memtest.c
migrate.c mm: replace multiple dcache flush with flush_dcache_folio() 2022-03-22 15:57:04 -07:00
mincore.c
mlock.c mm: refactor vm_area_struct::anon_vma_name usage code 2022-03-05 11:08:32 -08:00
mm_init.c
mmap_lock.c mm: mmap_lock: fix disabling preemption directly 2021-07-23 17:43:28 -07:00
mmap.c mm/mmap: remove obsolete comment in ksys_mmap_pgoff 2022-03-22 15:57:05 -07:00
mmu_gather.c mm: move tlb_flush_pending inline helpers to mm_inline.h 2022-01-15 16:30:27 +02:00
mmu_notifier.c
mmzone.c mm/mmzone.c: use try_cmpxchg() in page_cpupid_xchg_last() 2022-03-22 15:57:05 -07:00
mprotect.c mm: refactor vm_area_struct::anon_vma_name usage code 2022-03-05 11:08:32 -08:00
mremap.c mm/mremap:: use vma_lookup() instead of find_vma() 2022-03-22 15:57:05 -07:00
msync.c
nommu.c Merge branch 'akpm' (patches from Andrew) 2021-11-06 14:08:17 -07:00
oom_kill.c Merge branch 'signal-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2022-01-17 05:49:30 +02:00
page_alloc.c mm/page_alloc: do not prefetch buddies during bulk free 2022-03-22 15:57:06 -07:00
page_counter.c mm/page_counter: remove an incorrect call to propagate_protected_usage() 2022-01-15 16:30:27 +02:00
page_ext.c mm: make some vars and functions static or __init 2022-01-15 16:30:31 +02:00
page_idle.c mm/idle_page_tracking: make PG_idle reusable 2021-09-08 11:50:24 -07:00
page_io.c delayacct: support swapin delay accounting for swapping without blkio 2022-01-20 08:52:55 +02:00
page_isolation.c Revert "mm/page_isolation: unset migratetype directly for non Buddy page" 2022-02-04 09:25:04 -08:00
page_owner.c lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() 2022-01-22 08:33:37 +02:00
page_poison.c
page_reporting.c
page_reporting.h
page_table_check.c mm/page_table_check: check entries at pmd levels 2022-02-04 09:25:04 -08:00
page_vma_mapped.c mm: device exclusive memory access 2021-07-01 11:06:03 -07:00
page-writeback.c mm/writeback: minor clean up for highmem_dirtyable_memory 2022-03-22 15:57:01 -07:00
pagewalk.c
percpu-internal.h mm: memcg/percpu: account extra objcg space to memory cgroups 2022-01-15 16:30:31 +02:00
percpu-km.c percpu: flush tlb in pcpu_reclaim_populated() 2021-07-04 18:30:17 +00:00
percpu-stats.c
percpu-vm.c percpu: flush tlb in pcpu_reclaim_populated() 2021-07-04 18:30:17 +00:00
percpu.c bitmap patches for 5.17-rc1 2022-01-23 06:20:44 +02:00
pgalloc-track.h
pgtable-generic.c mm: move tlb_flush_pending inline helpers to mm_inline.h 2022-01-15 16:30:27 +02:00
process_vm_access.c
ptdump.c
readahead.c remove inode_congested() 2022-03-22 15:57:01 -07:00
rmap.c mm/rmap: fix potential batched TLB flush race 2022-01-15 16:30:31 +02:00
rodata_test.c
secretmem.c mm/secretmem: avoid letting secretmem_users drop to zero 2021-10-28 17:18:55 -07:00
shmem.c mm: shmem: fix missing cache flush in shmem_mfill_atomic_pte() 2022-03-22 15:57:04 -07:00
shuffle.c
shuffle.h
slab_common.c Merge branch 'akpm' (patches from Andrew) 2022-01-15 20:37:06 +02:00
slab.c mm: introduce kmem_cache_alloc_lru 2022-03-22 15:57:03 -07:00
slab.h mm: introduce kmem_cache_alloc_lru 2022-03-22 15:57:03 -07:00
slob.c mm: introduce kmem_cache_alloc_lru 2022-03-22 15:57:03 -07:00
slub.c mm: introduce kmem_cache_alloc_lru 2022-03-22 15:57:03 -07:00
sparse-vmemmap.c mm: remove redundant smp_wmb() 2021-11-06 13:30:36 -07:00
sparse.c mm/sparse: make mminit_validate_memmodel_limits() static 2022-03-22 15:57:05 -07:00
swap_cgroup.c
swap_slots.c treewide: Add missing includes masked by cgroup -> bpf dependency 2021-12-03 10:58:13 -08:00
swap_state.c mm: swap: get rid of livelock in swapin readahead 2022-03-17 11:02:13 -07:00
swap.c mm/swap: fix confusing comment in folio_mark_accessed 2022-03-22 15:57:01 -07:00
swapfile.c mm: mark swap_lock and swap_active_head static 2022-01-22 08:33:38 +02:00
truncate.c mm: remove cleancache 2022-01-22 08:33:38 +02:00
usercopy.c mm: Convert check_heap_object() to use struct slab 2022-01-06 12:25:51 +01:00
userfaultfd.c mm: userfaultfd: fix missing cache flush in mcopy_atomic_pte() and __mcopy_atomic() 2022-03-22 15:57:04 -07:00
util.c mm: Consider __GFP_NOWARN flag for oversized kvmalloc() calls 2022-03-04 10:00:37 -08:00
vmacache.c
vmalloc.c mm/vmalloc.c: fix "unused function" warning 2022-03-22 15:57:05 -07:00
vmpressure.c mm/vmpressure: fix data-race with memcg->socket_pressure 2021-11-06 13:30:40 -07:00
vmscan.c remove bdi_congested() and wb_congested() and related functions 2022-03-22 15:57:01 -07:00
vmstat.c mm/vmstat: add events for THP max_ptes_* exceeds 2022-01-15 16:30:29 +02:00
workingset.c xarray: use kmem_cache_alloc_lru to allocate xa_node 2022-03-22 15:57:03 -07:00
z3fold.c mm/z3fold: add kerneldoc fields for z3fold_pool 2021-07-01 11:06:03 -07:00
zbud.c mm/zbud: add kerneldoc fields for zbud_pool 2021-07-01 11:06:03 -07:00
zpool.c zpool: remove the list of pools_head 2022-01-15 16:30:31 +02:00
zsmalloc.c zsmalloc: replace get_cpu_var with local_lock 2022-01-22 08:33:37 +02:00
zswap.c frontswap: remove support for multiple ops 2022-01-22 08:33:38 +02:00