linux-kernel - Re: [PATCH v2 1/2] mm: memcg: refactor page state unit helpers

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Message-ID: <CAJD7tkbfq8P514-8Y1uZG9E0fMN2HwEaBmxEutBhjVtbtyEdCQ@mail.gmail.com>
Date:   Tue, 3 Oct 2023 12:47:25 -0700
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     Michal Koutný <mkoutny@...e.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Muchun Song <muchun.song@...ux.dev>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] mm: memcg: refactor page state unit helpers

On Tue, Oct 3, 2023 at 11:11 AM Michal Koutný <mkoutny@...e.com> wrote:
>
> On Fri, Sep 22, 2023 at 05:57:39PM +0000, Yosry Ahmed <yosryahmed@...gle.com> wrote:
> > memcg_page_state_unit() is currently used to identify the unit of a
> > memcg state item so that all stats in memory.stat are in bytes. However,
> > it lies about the units of WORKINGSET_* stats. These stats actually
> > represent pages, but we present them to userspace as a scalar number of
> > events. In retrospect, maybe those stats should have been memcg "events"
> > rather than memcg "state".
>
> Why isn't it possible to move WORKINGSET_* stats under the events now?
> (Instead of using internal and external units.)

Those constants are shared with code outside of memcg, namely enum
node_stat_item and enum vm_event_item, and IIUC they are used
differently outside of memcg. Did I miss something?

>
> Thanks,
> Michal