Re: [PATCH] mm: memcg: Fix memcg reclaim soft lockup

Michal Hocko
2020-08-26T11:00:19Z

On Wed 26-08-20 18:41:18, xunlei wrote:
> On 2020/8/26 下午4:11, Michal Hocko wrote:
> > On Wed 26-08-20 15:27:02, Xunlei Pang wrote:
> >> We've met softlockup with "CONFIG_PREEMPT_NONE=y", when
> >> the target memcg doesn't have any reclaimable memory.
> >
> > Do you have any scenario when this happens or is this some sort of a
> > test case?
>
> It can happen on tiny guest scenarios.

OK, you made me more curious. If this is a tiny guest and this is a hard
limit reclaim path then we should trigger an oom killer which should
kill the offender and that in turn bail out from the try_charge lopp
(see should_force_charge). So how come this repeats enough in your setup
that it causes soft lockups?
--
Michal Hocko
SUSE Labs