linux-kernel - Re: [PATCH v2] memcg: css_tryget

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Message-ID: <20200304123217.GK16139@dhcp22.suse.cz>
Date:   Wed, 4 Mar 2020 13:32:17 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Roman Gushchin <guro@...com>, Johannes Weiner <hannes@...xchg.org>,
        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 v2] memcg: css_tryget_online cleanups

On Tue 03-03-20 15:49:41, Shakeel Butt wrote:
> On Tue, Mar 3, 2020 at 1:32 AM Michal Hocko <mhocko@...nel.org> wrote:
[...]
> > Could you be more specific about the swap in case please?
> >
> 
> With swap accounting enabled, if the memcg of the swapped out page is
> not online then the memcg extracted from the given 'mm' will be
> charged and if 'mm' is NULL then root memcg will be charged. However I
> could not find a code path where the given 'mm' will be NULL for
> swap-in case.

Yes, this is my understanding as well. All the paths are getting mm from
a vma AFAICS. This is a valuable information for the changelog.

-- 
Michal Hocko
SUSE Labs