mm, memcg: periodically schedule when emptying page list
authorHugh Dickins <hughd@google.com>
Wed, 4 Jun 2014 23:11:04 +0000 (16:11 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 4 Jun 2014 23:54:13 +0000 (16:54 -0700)
commit2a7a0e0fdc49a08740a69d51ef44ef09763072b0
tree88d883113fd544867f6b67b4cea3ab663f88a831
parent4a0da71b96b9d4080c0820e9e7d02470ebe62dc6
mm, memcg: periodically schedule when emptying page list

mem_cgroup_force_empty_list() can iterate a large number of pages on an
lru and mem_cgroup_move_parent() doesn't return an errno unless certain
criteria, none of which indicate that the iteration may be taking too
long, is met.

We have encountered the following stack trace many times indicating
"need_resched set for > 51000020 ns (51 ticks) without schedule", for
example:

scheduler_tick()
<timer irq>
mem_cgroup_move_account+0x4d/0x1d5
mem_cgroup_move_parent+0x8d/0x109
mem_cgroup_reparent_charges+0x149/0x2ba
mem_cgroup_css_offline+0xeb/0x11b
cgroup_offline_fn+0x68/0x16b
process_one_work+0x129/0x350

If this iteration is taking too long, we still need to do cond_resched()
even when an individual page is not busy.

[rientjes@google.com: changelog]
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/memcontrol.c