From: Michal Hocko <mhocko@xxxxxxxx>
Subject: mm, oom: remove sleep from under oom_lock
Tetsuo has pointed out that since 27ae357fa82b ("mm, oom: fix concurrent
munlock and oom reaper unmap, v3") we have a strong synchronization
between the oom_killer and victim's exiting because both have to take the
oom_lock. Therefore the original heuristic to sleep for a short time in
out_of_memory doesn't serve the original purpose.
Moreover Tetsuo has noticed that the short sleep can be more harmful than
actually useful. Hammering the system with many processes can lead to a
starvation when the task holding the oom_lock can block for a long time
(minutes) and block any further progress because the oom_reaper depends on
the oom_lock as well.
Drop the short sleep from out_of_memory when we hold the lock. Keep the
sleep when the trylock fails to throttle the concurrent OOM paths a bit.
This should be solved in a more reasonable way (e.g. sleep proportional
to the time spent in the active reclaiming etc.) but this is much more
complex thing to achieve. This is a quick fixup to remove a stale code.
Link: http://lkml.kernel.org/r/20180709074706.30635-1-mhocko@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Reported-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/oom_kill.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
--- a/mm/oom_kill.c~mm-oom-remove-sleep-from-under-oom_lock
+++ a/mm/oom_kill.c
@@ -1077,15 +1077,9 @@ bool out_of_memory(struct oom_control *o
dump_header(oc, NULL);
panic("Out of memory and no killable processes...\n");
}
- if (oc->chosen && oc->chosen != (void *)-1UL) {
+ if (oc->chosen && oc->chosen != (void *)-1UL)
oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
"Memory cgroup out of memory");
- /*
- * Give the killed process a good chance to exit before trying
- * to allocate memory again.
- */
- schedule_timeout_killable(1);
- }
return !!oc->chosen;
}
_
