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References: <20230523205922.3852731-1-kaleshsingh@google.com>
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From:   Yu Zhao <yuzhao@google.com>
Date:   Tue, 23 May 2023 16:04:51 -0600
Message-ID: <CAOUHufb88CBQibAx=jr7xX7y4Witw4HhCSAd-P4q2qoCKBLZSw@mail.gmail.com>
Subject: Re: [PATCH] mm-unstable: Multi-gen LRU: Fix workingset accounting
To:     Kalesh Singh <kaleshsingh@google.com>, akpm@linux-foundation.org
Cc:     surenb@google.com, android-mm@google.com, kernel-team@android.com,
        Charan Teja Kalla <quic_charante@quicinc.com>,
        Oleksandr Natalenko <oleksandr@natalenko.name>,
        "Jan Alexander Steffens (heftig)" <heftig@archlinux.org>,
        Brian Geffon <bgeffon@google.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
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On Tue, May 23, 2023 at 2:59=E2=80=AFPM Kalesh Singh <kaleshsingh@google.co=
m> wrote:
>
> On Android app cycle workloads, MGLRU showed a significant reduction
> in workingset refaults although pgpgin/pswpin remained relatively
> unchanged. This indicated MGLRU may be undercounting workingset
> refaults.
>
> This has impact on userspace programs, like Android's LMKD, that
> monitor workingset refault statistics to detect thrashing.
>
> It was found that refaults were only accounted if the MGLRU shadow
> entry was for a recently evicted folio. However, recently evicted
> folios should be accounted as workingset activation, and refaults
> should be accounted regardless of recency.
>
> Fix MGLRU's workingset refault and activation accounting to more
> closely match that of the conventional active/inactive LRU.
>
> Fixes: ac35a4902374 ("mm: multi-gen LRU: minimal implementation")
> Cc: Yu Zhao <yuzhao@google.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Reported-by: Charan Teja Kalla <quic_charante@quicinc.com>
> Signed-off-by: Kalesh Singh <kaleshsingh@google.com>

Acked-by: Yu Zhao <yuzhao@google.com>