Re: [RFC] mm: memcg: add priority for soft limit reclaiming

Hillf Danton
2019-09-23T13:05:16Z

On Thu, 19 Sep 2019 21:32:31 +0800 Michal Hocko wrote:
>
> On Thu 19-09-19 21:13:32, Hillf Danton wrote:
> >
> > Currently memory controler is playing increasingly important role in
> > how memory is used and how pages are reclaimed on memory pressure.
> >
> > In daily works memcg is often created for critical tasks and their pre
> > configured memory usage is supposed to be met even on memory pressure.
> > Administrator wants to make it configurable that the pages consumed by
> > memcg-B can be reclaimed by page allocations invoked not by memcg-A but
> > by memcg-C.
>
> I am not really sure I understand the usecase well but this sounds like
> what memory reclaim protection in v2 is aiming at.
>
A tipoint to the v2 stuff please.

> > That configurability is addressed by adding priority for soft limit
> > reclaiming to make sure that no pages will be reclaimed from memcg of
> > higer priortiy in favor of memcg of lower priority.
>
> cgroup v1 interfaces are generally frozen and mostly aimed at backward
> compatibility. I am especially concerned about adding a new way to
> control soft limit which is known to be misdesigned and unfixable to
> behave reasonably.
>
An URL to the drafts/works about the new way in your git tree.

Thanks
Hillf