Re: [RFC] [PATCH] Cgroup based OOM killer controller

David Rientjes
2009-01-22T09:42:35Z

On Thu, 22 Jan 2009, Nikanth Karthikesan wrote:

> > You can't specify different behavior for an oom cgroup depending on what
> > type of oom it is, which is the problem with this proposal.
> >
>
> No. This does not disable any such special selection criteria which is used
> without this controller.
>

I didn't say it disabled it; the cpuset preference is actually implemented
in the badness() score and not specifically excluded in
select_bad_process(). That's because it's quite possible that a task has
allocated memory in a cpuset and then either moved to a separate cpuset or
had it's mems_allowed changed.

Please try it and you'll see. Create two cpusets, cpuset A and cpuset B.
Elevate cpuset A's oom.victim value and then trigger an oom in cpuset B.
Your patch will cause a task from cpuset A to be killed for a cpuset B
triggered oom which, more often than not, will not lead to future memory
freeing.

It's quite possible that cpuset A would be preferred to be killed in a
global unconstrained oom condition, however. That's the only reason why
one would elevate its oom.victim score to begin with. But it doesn't work
for cpuset-constrained ooms.

It's not going to help if it I explain it further and you don't try it out
on your own. Thanks.