mm/memcontrol.c: keep local VM counters in sync with the hierarchical ones
authorYafang Shao <laoar.shao@gmail.com>
Tue, 16 Jul 2019 23:26:06 +0000 (16:26 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 17 Jul 2019 02:23:21 +0000 (19:23 -0700)
commit766a4c19d880887c457811b86f1f68525e416965
treed249e91205876cc0126f1765cd71de40958ddfd2
parentf1549cb5ab2bd04cb370502b720268f610e21baa
mm/memcontrol.c: keep local VM counters in sync with the hierarchical ones

After commit 815744d75152 ("mm: memcontrol: don't batch updates of local
VM stats and events"), the local VM counter are not in sync with the
hierarchical ones.

Below is one example in a leaf memcg on my server (with 8 CPUs):

inactive_file 3567570944
total_inactive_file 3568029696

We find that the deviation is very great because the 'val' in
__mod_memcg_state() is in pages while the effective value in
memcg_stat_show() is in bytes.

So the maximum of this deviation between local VM stats and total VM
stats can be (32 * number_of_cpu * PAGE_SIZE), that may be an
unacceptably great value.

We should keep the local VM stats in sync with the total stats.  In
order to keep this behavior the same across counters, this patch updates
__mod_lruvec_state() and __count_memcg_events() as well.

Link: http://lkml.kernel.org/r/1562851979-10610-1-git-send-email-laoar.shao@gmail.com
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Yafang Shao <shaoyafang@didiglobal.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/memcontrol.c