Re: [PATCH] memcg, thp: do not invoke oom killer on thp charges

From: Michal Hocko
Date: Tue Apr 03 2018 - 11:55:19 EST

On Tue 03-04-18 10:58:53, Johannes Weiner wrote:
> On Wed, Mar 21, 2018 at 09:59:28PM +0100, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@xxxxxxxx>
> >
> > David has noticed that THP memcg charge can trigger the oom killer
> > since 2516035499b9 ("mm, thp: remove __GFP_NORETRY from khugepaged and
> > madvised allocations"). We have used an explicit __GFP_NORETRY
> > previously which ruled the OOM killer automagically.
> >
> > Memcg charge path should be semantically compliant with the allocation
> > path and that means that if we do not trigger the OOM killer for costly
> > orders which should do the same in the memcg charge path as well.
> > Otherwise we are forcing callers to distinguish the two and use
> > different gfp masks which is both non-intuitive and bug prone. Not to
> > mention the maintenance burden.
> >
> > Teach mem_cgroup_oom to bail out on costly order requests to fix the THP
> > issue as well as any other costly OOM eligible allocations to be added
> > in future.
> >
> > Fixes: 2516035499b9 ("mm, thp: remove __GFP_NORETRY from khugepaged and madvised allocations")
> > Reported-by: David Rientjes <rientjes@xxxxxxxxxx>
> > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> I also prefer this fix over having separate OOM behaviors (which is
> user-visible, and not just about technical ability to satisfy the
> allocation) between the allocator and memcg.
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>

I will repost the patch with the currently merged THP specific handling
reverted (see below). While 9d3c3354bb85 might have been an appropriate
quick fix, we shouldn't keep it longterm for 4.17+ IMHO.

Does you ack apply to that patch as well?