linux-kernel - Re: [v7 PATCH 09/12] mm: vmscan: use per memcg nr

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Date:   Tue, 9 Feb 2021 17:52:23 -0800
From:   Yang Shi <shy828301@...il.com>
To:     Roman Gushchin <guro@...com>
Cc:     Kirill Tkhai <ktkhai@...tuozzo.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Shakeel Butt <shakeelb@...gle.com>,
        Dave Chinner <david@...morbit.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [v7 PATCH 09/12] mm: vmscan: use per memcg nr_deferred of shrinker

On Tue, Feb 9, 2021 at 5:27 PM Roman Gushchin <guro@...com> wrote:
>
> On Tue, Feb 09, 2021 at 09:46:43AM -0800, Yang Shi wrote:
> > Use per memcg's nr_deferred for memcg aware shrinkers.  The shrinker's nr_deferred
> > will be used in the following cases:
> >     1. Non memcg aware shrinkers
> >     2. !CONFIG_MEMCG
> >     3. memcg is disabled by boot parameter
> >
> > Signed-off-by: Yang Shi <shy828301@...il.com>
> > ---
> >  mm/vmscan.c | 78 ++++++++++++++++++++++++++++++++++++++++++++---------
> >  1 file changed, 66 insertions(+), 12 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index d4b030a0b2a9..748aa6e90f83 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -368,6 +368,24 @@ static void unregister_memcg_shrinker(struct shrinker *shrinker)
> >       up_write(&shrinker_rwsem);
> >  }
> >
> > +static long count_nr_deferred_memcg(int nid, struct shrinker *shrinker,
> > +                                 struct mem_cgroup *memcg)
>
> "Count" is not associated with xchg() semantics in my head, but I don't know
> what's the better version. Maybe steal or pop?

It is used to retrieve the nr_deferred value. I don't think "steal" or
"pop" helps understand. Actually "count" is borrowed from
count_objects() method of shrinker.

>
> Otherwise the patch looks good to me.
>
> Thanks!