Subject: + mm-avoid-unnecessary-atomic-operations-during-end_page_writeback.patch added to -mm tree To: mgorman@xxxxxxx From: akpm@xxxxxxxxxxxxxxxxxxxx Date: Mon, 19 May 2014 15:05:34 -0700 The patch titled Subject: mm: avoid unnecessary atomic operations during end_page_writeback() has been added to the -mm tree. Its filename is mm-avoid-unnecessary-atomic-operations-during-end_page_writeback.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-avoid-unnecessary-atomic-operations-during-end_page_writeback.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-avoid-unnecessary-atomic-operations-during-end_page_writeback.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Mel Gorman <mgorman@xxxxxxx> Subject: mm: avoid unnecessary atomic operations during end_page_writeback() If a page is marked for immediate reclaim then it is moved to the tail of the LRU list. This occurs when the system is under enough memory pressure for pages under writeback to reach the end of the LRU but we test for this using atomic operations on every writeback. This patch uses an optimistic non-atomic test first. It'll miss some pages in rare cases but the consequences are not severe enough to warrant such a penalty. While the function does not dominate profiles during a simple dd test the cost of it is reduced. 73048 0.7428 vmlinux-3.15.0-rc5-mmotm-20140513 end_page_writeback 23740 0.2409 vmlinux-3.15.0-rc5-lessatomic end_page_writeback Signed-off-by: Mel Gorman <mgorman@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/filemap.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff -puN mm/filemap.c~mm-avoid-unnecessary-atomic-operations-during-end_page_writeback mm/filemap.c --- a/mm/filemap.c~mm-avoid-unnecessary-atomic-operations-during-end_page_writeback +++ a/mm/filemap.c @@ -753,8 +753,17 @@ EXPORT_SYMBOL(unlock_page); */ void end_page_writeback(struct page *page) { - if (TestClearPageReclaim(page)) + /* + * TestClearPageReclaim could be used here but it is an atomic + * operation and overkill in this particular case. Failing to + * shuffle a page marked for immediate reclaim is too mild to + * justify taking an atomic operation penalty at the end of + * ever page writeback. + */ + if (PageReclaim(page)) { + ClearPageReclaim(page); rotate_reclaimable_page(page); + } if (!test_clear_page_writeback(page)) BUG(); _ 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-use-jump-labels-to-avoid-checking-number_of_cpusets-fix.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-calculate-classzone_idx-once-from-the-zonelist-ref.patch mm-avoid-unnecessary-atomic-operations-during-end_page_writeback.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 smp-print-more-useful-debug-info-upon-receiving-ipi-on-an-offline-cpu-v5.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 cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu-v5.patch cpu-hotplug-smp-flush-any-pending-ipi-callbacks-before-cpu-offline.patch linux-next.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html