Re: [PATCH] mm, memcg: avoid oom if cgroup is not populated

[Yafang Shao <laoar.shao@gmail.com>]

On Wed, Nov 27, 2019 at 12:30 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Tue, Nov 26, 2019 at 08:02:49AM -0500, Yafang Shao wrote:
> > There's one case that the processes in a memcg are all exit (due to OOM
> > group or some other reasons), but the file page caches are still exist.
> > These file page caches may be protected by memory.min so can't be
> > reclaimed. If we can't success to restart the processes in this memcg or
> > don't want to make this memcg offline, then we want to drop the file page
> > caches.
> > The advantage of droping this file caches is it can avoid the reclaimer
> > (either kswapd or direct) scanning and reclaiming pages from all memcgs
> > exist in this system, because currently the reclaimer will fairly reclaim
> > pages from all memcgs if the system is under memory pressure.
> > The possible method to drop these file page caches is setting the
> > hard limit of this memcg to 0. Unfortunately this may invoke the OOM killer
> > and generates lots of misleading outputs, that should not happen.
>
> You can set memory.high instead...?

Well, I will take a look at memory.high and analye whether it is reliable.

Thanks
Yafang