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Date:   Mon, 7 Dec 2020 12:33:18 -0800 (PST)
From:   Hugh Dickins <hughd@google.com>
To:     Roman Gushchin <guro@fb.com>
cc:     Michal Hocko <mhocko@suse.com>,
        Muchun Song <songmuchun@bytedance.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>,
        Hugh Dickins <hughd@google.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>,
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Subject: Re: [External] Re: [RESEND PATCH v2 00/12] Convert all vmstat counters
 to pages or bytes
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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.

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.

Hugh