linux-kernel - Re: [PATCH] mm: vmscan : pgdemote vmstat is not getting updated when MGLRU is enabled.

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Message-ID: <CAOUHufaZKgNnZBox8wSONrGYRfskmzKoa0tHb5sUNfYRFFHq3w@mail.gmail.com>
Date: Wed, 8 Jan 2025 23:46:36 -0700
From: Yu Zhao <yuzhao@...gle.com>
To: Donet Tom <donettom@...ux.ibm.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Kaiyang Zhao <kaiyang2@...cmu.edu>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Ritesh Harjani <ritesh.list@...il.com>, 
	"Aneesh Kumar K . V" <aneesh.kumar@...nel.org>, David Rientjes <rientjes@...gle.com>, 
	Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, 
	Muchun Song <muchun.song@...ux.dev>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Shakeel Butt <shakeel.butt@...ux.dev>, Wei Xu <weixugc@...gle.com>
Subject: Re: [PATCH] mm: vmscan : pgdemote vmstat is not getting updated when
 MGLRU is enabled.

On Wed, Jan 8, 2025 at 11:05 PM Donet Tom <donettom@...ux.ibm.com> wrote:
>
> When MGLRU is enabled, the pgdemote_kswapd, pgdemote_direct, and
> pgdemote_khugepaged stats in vmstat are not being updated.
>
> 'Commit f77f0c751478 ("mm,memcg: provide per-cgroup counters for
> NUMA balancing operations")' moved the pgdemote vmstat update
> from demote_folio_list() to shrink_inactive_list(), which is in
> the normal LRU path. As a result, the pgdemote stats are updated
> correctly for the normal LRU but not for MGLRU.
>
> To address this, we have added the pgdemote stat update in the
> evict_folios() function, which is in the MGLRU path. With this
> patch, the pgdemote stats will now be updated correctly when MGLRU
> is enabled.
>
> Without this patch vmstat output when MGLRU is enabled
> ======================================================
> pgdemote_kswapd 0
> pgdemote_direct 0
> pgdemote_khugepaged 0
>
> With this patch vmstat output when MGLRU is enabled
> ===================================================
> pgdemote_kswapd 43234
> pgdemote_direct 4691
> pgdemote_khugepaged 0
>
> Fixes: f77f0c751478 ("mm,memcg: provide per-cgroup counters for NUMA balancing operations")
> Signed-off-by: Donet Tom <donettom@...ux.ibm.com>

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