On Wed, 27 Nov 2013, Johannes Weiner wrote:
> > It appears as though this work is being developed in Linus's tree rather
> > than -mm, so I'm asking if we should consider backing some of it out for
> > 3.14 instead.
>
> The changes fix a deadlock problem. Are they creating problems that
> are worse than deadlocks, that would justify their revert?
>
None that I am currently aware of, I'll continue to try them out. I'd
suggest just dropping the stable@xxxxxxxxxx from the whole series though
unless there is another report of such a problem that people are running
into.
> Since we can't physically draw a perfect line, we should strive for a
> reasonable and intuitive line. After that it's rapidly diminishing
> returns. Killing something after that much reclaim effort without
> success is a completely reasonable and intuitive line to draw. It's
> also the line that has been drawn a long time ago and we're not
> breaking this because of a micro optmimization.
>
You don't think something like this is helpful after scanning a memcg will
a large number of processes?
We've had this patch internally since we started using memcg, it has
avoided some unnecessary oom killing.
---
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1836,6 +1836,13 @@ static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
if (!chosen)
return;
points = chosen_points * 1000 / totalpages;
+
+ /* One last chance to see if we really need to kill something */
+ if (mem_cgroup_margin(memcg) >= (1 << order)) {
+ put_task_struct(chosen);
+ return;
+ }
+
oom_kill_process(chosen, gfp_mask, order, points, totalpages, memcg,
NULL, "Memory cgroup out of memory");
}
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