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From:   Muchun Song <songmuchun@bytedance.com>
Date:   Tue, 8 Dec 2020 10:42:58 +0800
Message-ID: <CAMZfGtUKvTLOud1cL6mtisq6gtMu-X8th8uoyGtTD4d7LXPa+Q@mail.gmail.com>
Subject: Re: [External] Re: [RESEND PATCH v2 00/12] Convert all vmstat
 counters to pages or bytes
To:     Hugh Dickins <hughd@google.com>
Cc:     Roman Gushchin <guro@fb.com>, Michal Hocko <mhocko@suse.com>,
        Greg KH <gregkh@linuxfoundation.org>, rafael@kernel.org,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Will Deacon <will@kernel.org>, Mike Rapoport <rppt@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, esyr@redhat.com,
        peterx@redhat.com, krisman@collabora.com,
        Suren Baghdasaryan <surenb@google.com>, avagin@openvz.org,
        Marco Elver <elver@google.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
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On Tue, Dec 8, 2020 at 4:33 AM Hugh Dickins <hughd@google.com> wrote:
>
> On Mon, 7 Dec 2020, Roman Gushchin wrote:
> > On Mon, Dec 07, 2020 at 04:02:54PM +0100, Michal Hocko wrote:
> > >
> > > As I've said the THP accounting change makes more sense to me because it
> > > allows future changes which are already undergoing so there is more
> > > merit in those.
> >
> > +1
> > And this part is absolutely trivial.
>
> It does need to be recognized that, with these changes, every THP stats
> update overflows the per-cpu counter, resorting to atomic global updates.
> And I'd like to see that mentioned in the commit message.

Thanks for reminding me. Will add.

>
> But this change is consistent with 4.7's 8f182270dfec ("mm/swap.c: flush
> lru pvecs on compound page arrival"): we accepted greater overhead for
> greater accuracy back then, so I think it's okay to do so for THP stats.

Agree. Thanks.

>
> Hugh


-- 
Yours,
Muchun