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Date:   Tue, 15 Oct 2019 11:24:17 -0400
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc:     linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        Michal Hocko <mhocko@kernel.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>
Subject: Re: [PATCH] mm/memcontrol: update lruvec counters in
 mem_cgroup_move_account
Message-ID: <20191015152417.GA141964@cmpxchg.org>
References: <157112699975.7360.1062614888388489788.stgit@buzz>
 <20191015135348.GA139269@cmpxchg.org>
 <89171a94-8b6f-e949-0078-10fa8fd26dfc@yandex-team.ru>
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On Tue, Oct 15, 2019 at 05:04:44PM +0300, Konstantin Khlebnikov wrote:
> On 15/10/2019 16.53, Johannes Weiner wrote:
> > On Tue, Oct 15, 2019 at 11:09:59AM +0300, Konstantin Khlebnikov wrote:
> > > Mapped, dirty and writeback pages are also counted in per-lruvec stats.
> > > These counters needs update when page is moved between cgroups.
> > > 
> > > Fixes: 00f3ca2c2d66 ("mm: memcontrol: per-lruvec stats infrastructure")
> > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> > 
> > Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> > 
> > Please mention in the changelog that currently is nobody *consuming*
> > the lruvec versions of these counters and that there is no
> > user-visible effect. Thanks
> > 
> 
> Maybe just kill all these per-lruvec counters?
> I see only one user which have no alternative data source: WORKINGSET_ACTIVATE.
> 
> This will save some memory: 32 * sizeof(long) * nr_nodes * nr_cpus bytes

This is backwards, see my reply to Michal, as well as the patches at
https://lore.kernel.org/linux-mm/20190603210746.15800-1-hannes@cmpxchg.org/

We're not using the lruvec counters in all places where we should.