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authorMel Gorman <mgorman@techsingularity.net>2017-11-15 17:37:48 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-15 18:21:06 -0800
commitd9ed0d08b6c6a882da1d8e75bb3162fc889fd199 (patch)
tree90b08bbc6146e01cf9f7e03f0acec14f6694b98b /mm
parentf2187599189d94aeeee2fa5d9806186c7732ed37 (diff)
download96b-common-d9ed0d08b6c6a882da1d8e75bb3162fc889fd199.tar.gz
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 <mgorman@techsingularity.net> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/swap.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/swap.c b/mm/swap.c
index 4edac536fe24..3e564a95ee73 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);
}