Re: [PATCH resend] memcg: introduce per-memcg reclaim interface

[Yosry Ahmed <yosryahmed@google.com>]

On Fri, Apr 1, 2022 at 1:39 AM Vaibhav Jain <vaibhav@linux.ibm.com> wrote:
>
>
> Yosry Ahmed <yosryahmed@google.com> writes:
> > From: Shakeel Butt <shakeelb@google.com>
> >
> > Introduce an memcg interface to trigger memory reclaim on a memory cgroup.
> <snip>
>
> > +
> > +     while (nr_reclaimed < nr_to_reclaim) {
> > +             unsigned long reclaimed;
> > +
> > +             if (signal_pending(current))
> > +                     break;
> > +
> > +             reclaimed = try_to_free_mem_cgroup_pages(memcg,
> > +                                             nr_to_reclaim - nr_reclaimed,
> > +                                             GFP_KERNEL, true);
> > +
> > +             if (!reclaimed && !nr_retries--)
> > +                     break;
> > +
> > +             nr_reclaimed += reclaimed;
>
> I think there should be a cond_resched() in this loop before
> try_to_free_mem_cgroup_pages() to have better chances of reclaim
> succeding early.
>
Thanks for taking the time to look at this!

I believe this loop is modeled after the loop in memory_high_write()
for the memory.high interface. Is there a reason why it should be
needed here but not there?

> <snip>
>
> --
> Cheers
> ~ Vaibhav