]> git.baikalelectronics.ru Git - kernel.git/commit
mm: bail out in shrink_inactive_list()
authorMinchan Kim <minchan@kernel.org>
Thu, 28 Jul 2016 22:47:40 +0000 (15:47 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 28 Jul 2016 23:07:41 +0000 (16:07 -0700)
commit7b6de2162df997a2903631874623514a60c4e41d
tree2a8e2875018e9e13452f9f49edcd60c90ed5e818
parent82763c0b68b810a259ffc7d3fa72567eac2adbee
mm: bail out in shrink_inactive_list()

With node-lru, if there are enough reclaimable pages in highmem but
nothing in lowmem, VM can try to shrink inactive list although the
requested zone is lowmem.

The problem is that if the inactive list is full of highmem pages then a
direct reclaimer searching for a lowmem page waste CPU scanning
uselessly.  It just burns out CPU.  Even, many direct reclaimers are
stalled by too_many_isolated if lots of parallel reclaimer are going on
although there are no reclaimable memory in inactive list.

I tried the experiment 4 times in 32bit 2G 8 CPU KVM machine to get
elapsed time.

hackbench 500 process 2

 = Old =

  1st: 289s 2nd: 310s 3rd: 112s 4th: 272s

 = Now =

  1st: 31s  2nd: 132s 3rd: 162s 4th: 50s.

[akpm@linux-foundation.org: fixes per Mel]
Link: http://lkml.kernel.org/r/1469433119-1543-1-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/vmscan.c