Re: [PATCH] mm,oom: Hold oom_victims counter while OOM reaping.

[Michal Hocko <mhocko@kernel.org>]

On Thu 26-05-16 20:47:47, Tetsuo Handa wrote:
> Continued from http://lkml.kernel.org/r/201605252330.IAC82384.OOSQHVtFFFLOMJ@I-love.SAKURA.ne.jp :
> > > I do not think we want to wait inside the oom_lock as it is a global
> > > lock shared by all OOM killer contexts. Another option would be to use
> > > the oom_lock inside __oom_reap_task. It is not super cool either because
> > > now we have a dependency on the lock but looks like reasonably easy
> > > solution.
> > 
> > It would be nice if we can wait until memory reclaimed from the OOM victim's
> > mm is queued to freelist for allocation. But I don't have idea other than
> > oomkiller_holdoff_timer.
> > 
> > I think this problem should be discussed another day in a new thread.
> > 
> 
> Can we use per "struct signal_struct" oom_victims instead of global oom_lock?

The problem with signal_struct is that we will not help if the task gets
unhashed from the task list which usually happens quite early after
exit_mm. The oom_lock will keep other OOM killer activity away until we
reap the address space and free up the memory so it would cover that
case. So I think the oom_lock is a more robust solution. I plan to post
the patch with the full changelog soon I just wanted to finish the other
pile before.
-- 
Michal Hocko
SUSE Labs

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