The patch titled
vmscan: add block plug for page reclaim
has been added to the -mm tree. Its filename is
vmscan-add-block-plug-for-page-reclaim.patch
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------------------------------------------------------
Subject: vmscan: add block plug for page reclaim
From: Shaohua Li <shaohua.li@xxxxxxxxx>
per-task block plug can reduce block queue lock contention and increase
request merge. Currently page reclaim doesn't support it. I originally
thought page reclaim doesn't need it, because kswapd thread count is
limited and file cache write is done at flusher mostly.
When I test a workload with heavy swap in a 4-node machine, each CPU is
doing direct page reclaim and swap. This causes block queue lock
contention. In my test, without below patch, the CPU utilization is about
2% ~ 7%. With the patch, the CPU utilization is about 1% ~ 3%. Disk
throughput isn't changed. This should improve normal kswapd write and
file cache write too (increase request merge for example), but might not
be so obvious as I explain above.
Signed-off-by: Shaohua Li <shaohua.li@xxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 3 +++
1 file changed, 3 insertions(+)
diff -puN mm/vmscan.c~vmscan-add-block-plug-for-page-reclaim mm/vmscan.c
--- a/mm/vmscan.c~vmscan-add-block-plug-for-page-reclaim
+++ a/mm/vmscan.c
@@ -2022,12 +2022,14 @@ static void shrink_zone(int priority, st
enum lru_list l;
unsigned long nr_reclaimed, nr_scanned;
unsigned long nr_to_reclaim = sc->nr_to_reclaim;
+ struct blk_plug plug;
restart:
nr_reclaimed = 0;
nr_scanned = sc->nr_scanned;
get_scan_count(zone, sc, nr, priority);
+ blk_start_plug(&plug);
while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
nr[LRU_INACTIVE_FILE]) {
for_each_evictable_lru(l) {
@@ -2051,6 +2053,7 @@ restart:
if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
break;
}
+ blk_finish_plug(&plug);
sc->nr_reclaimed += nr_reclaimed;
/*
_
Patches currently in -mm which might be from shaohua.li@xxxxxxxxx are
origin.patch
linux-next.patch
acpi-add-missing-_osi-strings-resend.patch
vmscan-add-block-plug-for-page-reclaim.patch
intel_idle-fix-api-misuse.patch
intel_idle-disable-auto_demotion-for-hotplugged-cpus.patch
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