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From:   Shakeel Butt <shakeelb@google.com>
Date:   Wed, 13 Jan 2021 11:12:54 -0800
Message-ID: <CALvZod4V3M=P8_Z14asBG8bKa=mYic4_OPLeoz5M7J5tsx=Gug@mail.gmail.com>
Subject: Re: [PATCH] mm: net: memcg accounting for TCP rx zerocopy
To:     Roman Gushchin <guro@fb.com>
Cc:     Arjun Roy <arjunroy@google.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        Cgroups <cgroups@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Jan 13, 2021 at 10:43 AM Roman Gushchin <guro@fb.com> wrote:
>
> On Tue, Jan 12, 2021 at 04:18:44PM -0800, Shakeel Butt wrote:
> > On Tue, Jan 12, 2021 at 4:12 PM Arjun Roy <arjunroy@google.com> wrote:
> > >
> > > On Tue, Jan 12, 2021 at 3:48 PM Roman Gushchin <guro@fb.com> wrote:
> > > >
> > [snip]
> > > > Historically we have a corresponding vmstat counter to each charged page.
> > > > It helps with finding accounting/stastistics issues: we can check that
> > > > memory.current ~= anon + file + sock + slab + percpu + stack.
> > > > It would be nice to preserve such ability.
> > > >
> > >
> > > Perhaps one option would be to have it count as a file page, or have a
> > > new category.
> > >
> >
> > Oh these are actually already accounted for in NR_FILE_MAPPED.
>
> Well, it's confusing. Can't we fix this by looking at the new page memcg flag?

Yes we can. I am inclined more towards just using NR_FILE_PAGES (as
Arjun suggested) instead of adding a new metric.