From d9ed0d08b6c6a882da1d8e75bb3162fc889fd199 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Wed, 15 Nov 2017 17:37:48 -0800 Subject: [PATCH] mm: only drain per-cpu pagevecs once per pagevec usage When a pagevec is initialised on the stack, it is generally used multiple times over a range of pages, looking up entries and then releasing them. On each pagevec_release, the per-cpu deferred LRU pagevecs are drained on the grounds the page being released may be on those queues and the pages may be cache hot. In many cases only the first drain is necessary as it's unlikely that the range of pages being walked is racing against LRU addition. Even if there is such a race, the impact is marginal where as constantly redraining the lru pagevecs costs. This patch ensures that pagevec is only drained once in a given lifecycle without increasing the cache footprint of the pagevec structure. Only sparsetruncate tiny is shown here as large files have many exceptional entries and calls pagecache_release less frequently. sparsetruncate (tiny) 4.14.0-rc4 4.14.0-rc4 batchshadow-v1r1 onedrain-v1r1 Min Time 141.00 ( 0.00%) 141.00 ( 0.00%) 1st-qrtle Time 142.00 ( 0.00%) 142.00 ( 0.00%) 2nd-qrtle Time 142.00 ( 0.00%) 142.00 ( 0.00%) 3rd-qrtle Time 143.00 ( 0.00%) 143.00 ( 0.00%) Max-90% Time 144.00 ( 0.00%) 144.00 ( 0.00%) Max-95% Time 146.00 ( 0.00%) 145.00 ( 0.68%) Max-99% Time 198.00 ( 0.00%) 194.00 ( 2.02%) Max Time 254.00 ( 0.00%) 208.00 ( 18.11%) Amean Time 145.12 ( 0.00%) 144.30 ( 0.56%) Stddev Time 12.74 ( 0.00%) 9.62 ( 24.49%) Coeff Time 8.78 ( 0.00%) 6.67 ( 24.06%) Best99%Amean Time 144.29 ( 0.00%) 143.82 ( 0.32%) Best95%Amean Time 142.68 ( 0.00%) 142.31 ( 0.26%) Best90%Amean Time 142.52 ( 0.00%) 142.19 ( 0.24%) Best75%Amean Time 142.26 ( 0.00%) 141.98 ( 0.20%) Best50%Amean Time 141.90 ( 0.00%) 141.71 ( 0.13%) Best25%Amean Time 141.80 ( 0.00%) 141.43 ( 0.26%) The impact on bonnie is marginal and within the noise because a significant percentage of the file being truncated has been reclaimed and consists of shadow entries which reduce the hotness of the pagevec_release path. Link: http://lkml.kernel.org/r/20171018075952.10627-5-mgorman@techsingularity.net Signed-off-by: Mel Gorman Cc: Andi Kleen Cc: Dave Chinner Cc: Dave Hansen Cc: Jan Kara Cc: Johannes Weiner Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/pagevec.h | 4 +++- mm/swap.c | 5 ++++- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/include/linux/pagevec.h b/include/linux/pagevec.h index 4f56e0a..95c75c8 100644 --- a/include/linux/pagevec.h +++ b/include/linux/pagevec.h @@ -17,7 +17,8 @@ struct address_space; struct pagevec { unsigned long nr; - unsigned long cold; + bool cold; + bool drained; struct page *pages[PAGEVEC_SIZE]; }; @@ -54,6 +55,7 @@ static inline void pagevec_init(struct pagevec *pvec, int cold) { pvec->nr = 0; pvec->cold = cold; + pvec->drained = false; } static inline void pagevec_reinit(struct pagevec *pvec) diff --git a/mm/swap.c b/mm/swap.c index 4edac53..3e564a9 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -833,7 +833,10 @@ EXPORT_SYMBOL(release_pages); */ void __pagevec_release(struct pagevec *pvec) { - lru_add_drain(); + if (!pvec->drained) { + lru_add_drain(); + pvec->drained = true; + } release_pages(pvec->pages, pagevec_count(pvec), pvec->cold); pagevec_reinit(pvec); } -- 2.7.4