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 <20200916144057.GA194430@cmpxchg.org>
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From:   Muchun Song <songmuchun@bytedance.com>
Date:   Wed, 16 Sep 2020 22:47:12 +0800
Message-ID: <CAMZfGtX-q6vB853YCKqW3Yo=N=AFWcQSxYF=mYK6PKC2XAHMAg@mail.gmail.com>
Subject: Re: [External] Re: [PATCH v5] mm: memcontrol: Add the missing
 numa_stat interface for cgroup v2
To:     Johannes Weiner <hannes@cmpxchg.org>
Cc:     Tejun Heo <tj@kernel.org>, Zefan Li <lizefan@huawei.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Michal Hocko <mhocko@kernel.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Shakeel Butt <shakeelb@google.com>,
        Roman Gushchin <guro@fb.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Cgroups <cgroups@vger.kernel.org>, linux-doc@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>
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On Wed, Sep 16, 2020 at 10:42 PM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Wed, Sep 16, 2020 at 12:14:49PM +0800, Muchun Song wrote:
> > On Wed, Sep 16, 2020 at 5:50 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
> > >
> > > On Wed, Sep 16, 2020 at 01:18:01AM +0800, Muchun Song wrote:
> > > > In the cgroup v1, we have a numa_stat interface. This is useful for
> > > > providing visibility into the numa locality information within an
> > > > memcg since the pages are allowed to be allocated from any physical
> > > > node. One of the use cases is evaluating application performance by
> > > > combining this information with the application's CPU allocation.
> > > > But the cgroup v2 does not. So this patch adds the missing information.
> > > >
> > > > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > > > Suggested-by: Shakeel Butt <shakeelb@google.com>
> > > > Reviewed-by: Shakeel Butt <shakeelb@google.com>
> > >
> > > Yup, that would be useful information to have. Just a few comments on
> > > the patch below:
> > >
> > > > @@ -1368,6 +1368,78 @@ PAGE_SIZE multiple when read back.
> > > >               collapsing an existing range of pages. This counter is not
> > > >               present when CONFIG_TRANSPARENT_HUGEPAGE is not set.
> > > >
> > > > +  memory.numa_stat
> > > > +     A read-only flat-keyed file which exists on non-root cgroups.
> > >
> > > It's a nested key file, not flat.
> >
> > This is just copied from memory.stat documentation.Is the memory.stat
> > also a nested key file?
>
> No, memory.stat is a different format. From higher up in the document:
>
>   Flat keyed
>
>         KEY0 VAL0\n
>         KEY1 VAL1\n
>         ...
>
>   Nested keyed
>
>         KEY0 SUB_KEY0=VAL00 SUB_KEY1=VAL01...
>         KEY1 SUB_KEY0=VAL10 SUB_KEY1=VAL11...
>         ...

Got it. Thanks for your explanation.

>
> > > Otherwise, this looks reasonable to me.
> >
> > OK. Will do that.
>
> Thanks!


-- 
Yours,
Muchun