From eb709b0d062efd653a61183af8e27b2711c3cf5c Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Tue, 24 May 2011 17:12:55 -0700 Subject: mm: batch activate_page() to reduce lock contention The zone->lru_lock is heavily contented in workload where activate_page() is frequently used. We could do batch activate_page() to reduce the lock contention. The batched pages will be added into zone list when the pool is full or page reclaim is trying to drain them. For example, in a 4 socket 64 CPU system, create a sparse file and 64 processes, processes shared map to the file. Each process read access the whole file and then exit. The process exit will do unmap_vmas() and cause a lot of activate_page() call. In such workload, we saw about 58% total time reduction with below patch. Other workloads with a lot of activate_page also benefits a lot too. Andrew Morton suggested activate_page() and putback_lru_pages() should follow the same path to active pages, but this is hard to implement (see commit 7a608572a282a ("Revert "mm: batch activate_page() to reduce lock contention")). On the other hand, do we really need putback_lru_pages() to follow the same path? I tested several FIO/FFSB benchmark (about 20 scripts for each benchmark) in 3 machines here from 2 sockets to 4 sockets. My test doesn't show anything significant with/without below patch (there is slight difference but mostly some noise which we found even without below patch before). Below patch basically returns to the same as my first post. I tested some microbenchmarks: case-anon-cow-rand-mt 0.58% case-anon-cow-rand -3.30% case-anon-cow-seq-mt -0.51% case-anon-cow-seq -5.68% case-anon-r-rand-mt 0.23% case-anon-r-rand 0.81% case-anon-r-seq-mt -0.71% case-anon-r-seq -1.99% case-anon-rx-rand-mt 2.11% case-anon-rx-seq-mt 3.46% case-anon-w-rand-mt -0.03% case-anon-w-rand -0.50% case-anon-w-seq-mt -1.08% case-anon-w-seq -0.12% case-anon-wx-rand-mt -5.02% case-anon-wx-seq-mt -1.43% case-fork 1.65% case-fork-sleep -0.07% case-fork-withmem 1.39% case-hugetlb -0.59% case-lru-file-mmap-read-mt -0.54% case-lru-file-mmap-read 0.61% case-lru-file-mmap-read-rand -2.24% case-lru-file-readonce -0.64% case-lru-file-readtwice -11.69% case-lru-memcg -1.35% case-mmap-pread-rand-mt 1.88% case-mmap-pread-rand -15.26% case-mmap-pread-seq-mt 0.89% case-mmap-pread-seq -69.72% case-mmap-xread-rand-mt 0.71% case-mmap-xread-seq-mt 0.38% The most significent are: case-lru-file-readtwice -11.69% case-mmap-pread-rand -15.26% case-mmap-pread-seq -69.72% which use activate_page a lot. others are basically variations because each run has slightly difference. In UP case, 'size mm/swap.o' before the two patches: text data bss dec hex filename 6466 896 4 7366 1cc6 mm/swap.o after the two patches: text data bss dec hex filename 6343 896 4 7243 1c4b mm/swap.o Signed-off-by: Shaohua Li Cc: KOSAKI Motohiro Cc: Hiroyuki Kamezawa Cc: Andi Kleen Cc: Minchan Kim Cc: Rik van Riel Cc: Mel Gorman Cc: Johannes Weiner Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/swap.c | 45 ++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 40 insertions(+), 5 deletions(-) (limited to 'mm') diff --git a/mm/swap.c b/mm/swap.c index 2f365d1..3a442f1 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -272,14 +272,10 @@ static void update_page_reclaim_stat(struct zone *zone, struct page *page, memcg_reclaim_stat->recent_rotated[file]++; } -/* - * FIXME: speed this up? - */ -void activate_page(struct page *page) +static void __activate_page(struct page *page, void *arg) { struct zone *zone = page_zone(page); - spin_lock_irq(&zone->lru_lock); if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { int file = page_is_file_cache(page); int lru = page_lru_base_type(page); @@ -292,8 +288,45 @@ void activate_page(struct page *page) update_page_reclaim_stat(zone, page, file, 1); } +} + +#ifdef CONFIG_SMP +static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs); + +static void activate_page_drain(int cpu) +{ + struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu); + + if (pagevec_count(pvec)) + pagevec_lru_move_fn(pvec, __activate_page, NULL); +} + +void activate_page(struct page *page) +{ + if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { + struct pagevec *pvec = &get_cpu_var(activate_page_pvecs); + + page_cache_get(page); + if (!pagevec_add(pvec, page)) + pagevec_lru_move_fn(pvec, __activate_page, NULL); + put_cpu_var(activate_page_pvecs); + } +} + +#else +static inline void activate_page_drain(int cpu) +{ +} + +void activate_page(struct page *page) +{ + struct zone *zone = page_zone(page); + + spin_lock_irq(&zone->lru_lock); + __activate_page(page, NULL); spin_unlock_irq(&zone->lru_lock); } +#endif /* * Mark a page as having seen activity. @@ -464,6 +497,8 @@ static void drain_cpu_pagevecs(int cpu) pvec = &per_cpu(lru_deactivate_pvecs, cpu); if (pagevec_count(pvec)) pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL); + + activate_page_drain(cpu); } /** -- cgit v1.1