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

Yu Zhao
2025-01-09T06:47:17Z

On Wed, Jan 8, 2025 at 11:05 PM Donet Tom <donettom@linux.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@linux.ibm.com>

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