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From:   Yang Shi <shy828301@gmail.com>
Date:   Mon, 8 Aug 2022 10:55:09 -0700
Message-ID: <CAHbLzkp27aP4JYLPLzv2vtyzVe63bkhuZhw1jnxTF1Buvt4rew@mail.gmail.com>
Subject: Re: [PATCH v3] mm: add thp_utilization metrics to /proc/thp_utilization
To:     "Alex Zhu (Kernel)" <alexlzhu@fb.com>
Cc:     Matthew Wilcox <willy@infradead.org>, Rik van Riel <riel@fb.com>,
        Kernel Team <Kernel-team@fb.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>
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On Fri, Aug 5, 2022 at 12:52 PM Alex Zhu (Kernel) <alexlzhu@fb.com> wrote:
>
>
> >
> > Ah!  So when that exists, this interface tells us "how well" we're doin=
g.
> >
>
> Yes, exactly.
> >
> > Yeah, debugfs seems like a better place.  And I'd love to see the shrin=
ker
> > code.  Before you mentioned that I was having all kinds of peculiar
> > feelings about this code.  For example, suppose you have incredibly hot
> > 256kB of data, but the other 1792kB of data are never touched ... that
> > could cause us to do entirely the wrong thing and break up this THP.
> > Having it as a shrinker makes sense because the hot 256kB will keep the
> > THP from reaching the end of the list and being reclaimed.
>
> Sounds good, I=E2=80=99ll move this to debugfs then. Will follow up with =
the shrinker code
> in another patch. The shrinker relies on this scanning thread to figure o=
ut which
> THPs to reclaim.

I'm wondering whether you could reuse the THP deferred split shrinker
or not. It is already memcg aware.

>
> What are your thoughts regarding integrating this with DAMON?