Subject: + mm-do-not-use-unnecessary-atomic-operations-when-adding-pages-to-the-lru.patch added to -mm tree
To: mgorman@xxxxxxx,dave.hansen@xxxxxxxxx,hannes@xxxxxxxxxxx,hughd@xxxxxxxxxx,jack@xxxxxxx,mhocko@xxxxxxx,oleg@xxxxxxxxxx,paulmck@xxxxxxxxxxxxxxxxxx,peterz@xxxxxxxxxxxxx,riel@xxxxxxxxxx,tytso@xxxxxxx,vbabka@xxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 13 May 2014 15:41:08 -0700
The patch titled
Subject: mm: do not use unnecessary atomic operations when adding pages to the LRU
has been added to the -mm tree. Its filename is
mm-do-not-use-unnecessary-atomic-operations-when-adding-pages-to-the-lru.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-do-not-use-unnecessary-atomic-operations-when-adding-pages-to-the-lru.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-do-not-use-unnecessary-atomic-operations-when-adding-pages-to-the-lru.patch
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------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxx>
Subject: mm: do not use unnecessary atomic operations when adding pages to the LRU
When adding pages to the LRU we clear the active bit unconditionally. As
the page could be reachable from other paths we cannot use unlocked
operations without risk of corruption such as a parallel
mark_page_accessed. This patch tests if is necessary to clear the active
flag before using an atomic operation. This potentially opens a tiny race
when PageActive is checked as mark_page_accessed could be called after
PageActive was checked. The race already exists but this patch changes it
slightly. The consequence is that that the page may be promoted to the
active list that might have been left on the inactive list before the
patch. It's too tiny a race and too marginal a consequence to always use
atomic operations for.
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swap.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff -puN mm/swap.c~mm-do-not-use-unnecessary-atomic-operations-when-adding-pages-to-the-lru mm/swap.c
--- a/mm/swap.c~mm-do-not-use-unnecessary-atomic-operations-when-adding-pages-to-the-lru
+++ a/mm/swap.c
@@ -631,13 +631,15 @@ static void __lru_cache_add(struct page
*/
void lru_cache_add_anon(struct page *page)
{
- ClearPageActive(page);
+ if (PageActive(page))
+ ClearPageActive(page);
__lru_cache_add(page);
}
void lru_cache_add_file(struct page *page)
{
- ClearPageActive(page);
+ if (PageActive(page))
+ ClearPageActive(page);
__lru_cache_add(page);
}
EXPORT_SYMBOL(lru_cache_add_file);
_
Patches currently in -mm which might be from mgorman@xxxxxxx are
x86-require-x86-64-for-automatic-numa-balancing.patch
x86-define-_page_numa-by-reusing-software-bits-on-the-pmd-and-pte-levels.patch
x86-define-_page_numa-by-reusing-software-bits-on-the-pmd-and-pte-levels-fix-2.patch
mm-introduce-do_shared_fault-and-drop-do_fault-fix-fix.patch
mm-compactionc-isolate_freepages_block-small-tuneup.patch
mm-only-force-scan-in-reclaim-when-none-of-the-lrus-are-big-enough.patch
mm-huge_memoryc-complete-conversion-to-pr_foo.patch
mm-disable-zone_reclaim_mode-by-default.patch
mm-page_alloc-do-not-cache-reclaim-distances.patch
mm-page_alloc-do-not-cache-reclaim-distances-fix.patch
mm-page_alloc-prevent-migrate_reserve-pages-from-being-misplaced.patch
mm-compaction-clean-up-unused-code-lines.patch
mm-compaction-cleanup-isolate_freepages.patch
mm-compaction-cleanup-isolate_freepages-fix.patch
mm-compaction-cleanup-isolate_freepages-fix-2.patch
mm-compaction-cleanup-isolate_freepages-fix3.patch
mm-swapc-clean-up-lru_cache_add-functions.patch
mm-vmscan-do-not-throttle-based-on-pfmemalloc-reserves-if-node-has-no-zone_normal.patch
mm-vmscan-do-not-throttle-based-on-pfmemalloc-reserves-if-node-has-no-zone_normal-checkpatch-fixes.patch
mm-vmscan-do-not-throttle-based-on-pfmemalloc-reserves-if-node-has-no-zone_normal-fix.patch
mm-numa-add-migrated-transhuge-pages-to-lru-the-same-way-as-base-pages.patch
mm-swapc-introduce-put_refcounted_compound_page-helpers-for-spliting-put_compound_page.patch
mm-swapc-split-put_compound_page-function.patch
mm-introdule-compound_head_by_tail.patch
mm-x86-pgtable-drop-unneeded-preprocessor-ifdef.patch
mm-x86-pgtable-require-x86_64-for-soft-dirty-tracker.patch
mm-mempolicyc-parameter-doc-uniformization.patch
mm-migration-add-destination-page-freeing-callback.patch
mm-compaction-return-failed-migration-target-pages-back-to-freelist.patch
mm-compaction-add-per-zone-migration-pfn-cache-for-async-compaction.patch
mm-compaction-embed-migration-mode-in-compact_control.patch
mm-thp-avoid-excessive-compaction-latency-during-fault.patch
mm-thp-avoid-excessive-compaction-latency-during-fault-fix.patch
mm-compaction-terminate-async-compaction-when-rescheduling.patch
mm-compaction-do-not-count-migratepages-when-unnecessary.patch
mm-compaction-avoid-rescanning-pageblocks-in-isolate_freepages.patch
swap-change-swap_info-singly-linked-list-to-list_head.patch
plist-add-helper-functions.patch
plist-add-plist_requeue.patch
swap-change-swap_list_head-to-plist-add-swap_avail_head.patch
mm-page_alloc-do-not-update-zlc-unless-the-zlc-is-active.patch
mm-page_alloc-do-not-treat-a-zone-that-cannot-be-used-for-dirty-pages-as-full.patch
jump_label-expose-the-reference-count.patch
mm-page_alloc-use-jump-labels-to-avoid-checking-number_of_cpusets.patch
mm-page_alloc-only-check-the-zone-id-check-if-pages-are-buddies.patch
mm-page_alloc-only-check-the-alloc-flags-and-gfp_mask-for-dirty-once.patch
mm-page_alloc-take-the-alloc_no_watermark-check-out-of-the-fast-path.patch
mm-page_alloc-use-word-based-accesses-for-get-set-pageblock-bitmaps.patch
mm-page_alloc-reduce-number-of-times-page_to_pfn-is-called.patch
mm-page_alloc-lookup-pageblock-migratetype-with-irqs-enabled-during-free.patch
mm-page_alloc-use-unsigned-int-for-order-in-more-places.patch
mm-page_alloc-convert-hot-cold-parameter-and-immediate-callers-to-bool.patch
mm-shmem-avoid-atomic-operation-during-shmem_getpage_gfp.patch
mm-do-not-use-atomic-operations-when-releasing-pages.patch
mm-do-not-use-unnecessary-atomic-operations-when-adding-pages-to-the-lru.patch
fs-buffer-do-not-use-unnecessary-atomic-operations-when-discarding-buffers.patch
fs-buffer-do-not-use-unnecessary-atomic-operations-when-discarding-buffers-fix.patch
mm-non-atomically-mark-page-accessed-during-page-cache-allocation-where-possible.patch
mm-page_alloc-debug_vm-checks-for-free_list-placement-of-cma-and-reserve-pages.patch
do_shared_fault-check-that-mmap_sem-is-held.patch
smp-print-more-useful-debug-info-upon-receiving-ipi-on-an-offline-cpu.patch
smp-print-more-useful-debug-info-upon-receiving-ipi-on-an-offline-cpu-fix.patch
cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu.patch
cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu-v3.patch
linux-next.patch
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