From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/pagevec.h | 4 +++-
mm/swap.c | 5 ++++-
2 files changed, 7 insertions(+), 2 deletions(-)
diff -puN include/linux/pagevec.h~mm-only-drain-per-cpu-pagevecs-once-per-pagevec-usage include/linux/pagevec.h
--- a/include/linux/pagevec.h~mm-only-drain-per-cpu-pagevecs-once-per-pagevec-usage
+++ a/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 p
{
pvec->nr = 0;
pvec->cold = cold;
+ pvec->drained = false;
}
static inline void pagevec_reinit(struct pagevec *pvec)
diff -puN mm/swap.c~mm-only-drain-per-cpu-pagevecs-once-per-pagevec-usage mm/swap.c
--- a/mm/swap.c~mm-only-drain-per-cpu-pagevecs-once-per-pagevec-usage
+++ a/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);
}
_
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