linux-kernel - Re: [PATCH] memcg: effective memory.high reclaim for remote charging

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Message-ID: <20200507174949.GN6345@dhcp22.suse.cz>
Date:   Thu, 7 May 2020 19:49:49 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>, Roman Gushchin <guro@...com>,
        Greg Thelen <gthelen@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Cgroups <cgroups@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] memcg: effective memory.high reclaim for remote charging

On Thu 07-05-20 10:00:07, Shakeel Butt wrote:
> On Thu, May 7, 2020 at 9:47 AM Michal Hocko <mhocko@...nel.org> wrote:
> >
> > On Thu 07-05-20 09:33:01, Shakeel Butt wrote:
> > [...]
> > > @@ -2600,8 +2596,23 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
> > >                               schedule_work(&memcg->high_work);
> > >                               break;
> > >                       }
> > > -                     current->memcg_nr_pages_over_high += batch;
> > > -                     set_notify_resume(current);
> > > +
> > > +                     if (gfpflags_allow_blocking(gfp_mask))
> > > +                             reclaim_over_high(memcg, gfp_mask, batch);
> > > +
> > > +                     if (page_counter_read(&memcg->memory) <=
> > > +                         READ_ONCE(memcg->high))
> > > +                             break;
> >
> > I am half way to a long weekend so bear with me. Shouldn't this be continue? The
> > parent memcg might be still in excess even the child got reclaimed,
> > right?
> >
> 
> The reclaim_high() actually already does this walk up to the root and
> reclaim from ones who are still over their high limit. Though having
> 'continue' here is correct too.

Ohh, right. As I've said weekend brain. I will have a proper look next
week. This just hit my eyes.

-- 
Michal Hocko
SUSE Labs