Re: [patch] mm, oom: make a last minute check to prevent unnecessary memcg oom kills

[Michal Hocko]

On Tue 17-03-20 12:00:45, Ami Fischman wrote:
> On Tue, Mar 17, 2020 at 11:26 AM Robert Kolchmeyer
> <rkolchmeyer@xxxxxxxxxx> wrote:
> >
> > On Tue, Mar 10, 2020 at 3:54 PM David Rientjes <rientjes@xxxxxxxxxx> wrote:
> > >
> > > Robert, could you elaborate on the user-visible effects of this issue that
> > > caused it to initially get reported?
> >
> > Ami (now cc'ed) knows more, but here is my understanding.
> 
> Robert's description of the mechanics we observed is accurate.
> 
> We discovered this regression in the oom-killer's behavior when
> attempting to upgrade our system. The fraction of the system that
> went unhealthy due to this issue was approximately equal to the
> _sum_ of all other causes of unhealth, which are many and varied,
> but each of which contribute only a small amount of
> unhealth. This issue forced a rollback to the previous kernel
> where we ~never see this behavior, returning our unhealth levels
> to the previous background levels.

Could you be more specific on the good vs. bad kernel versions? Because
I do not remember any oom changes that would affect the
time-to-check-time-to-kill race. The timing might be slightly different
in each kernel version of course.

-- 
Michal Hocko
SUSE Labs