Re: [PATCH v5 2/4] mm: workingset: use lruvec_page_state_local() to count lru pages

[Kairui Song]

On Fri, Sep 11, 2026 at 10:26 AM Hui Zhu <hui.zhu@xxxxxxxxx> wrote:
>
> From: Hui Zhu <zhuhui@xxxxxxxxxx>
>
> Commit 7404bd37cfbe ("mm: workingset: use lruvec_lru_size() to get the
> number of lru pages") switched count_shadow_nodes() to lruvec_lru_size().
> With CONFIG_MEMCG enabled, lruvec_lru_size() reads mz->lru_zone_size,
> which only the classic LRU paths maintain.  MGLRU accounts its pages
> through __update_lru_size(), which skips that array, so with MGLRU on the
> four evictable LRU lists are always seen as empty.  The shadow node budget
> (pages >> 3) then collapses to slab plus unevictable pages, and the
> workingset shadow shrinker reclaims eviction tokens almost as fast as they
> are created, losing thrashing protection.
>
> lruvec_page_state_local() reads lruvec_stats->state_local instead, which
> both classic LRU and MGLRU maintain.  Switch back to it.  The reparenting
> race this re-exposes on cgroup v2 is closed by the preceding patch that
> redirects dying-memcg stat updates for all hierarchies.

Looks nice! thanks.
>
> Fixes: 7404bd37cfbe ("mm: workingset: use lruvec_lru_size() to get the number of lru pages")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Hui Zhu <zhuhui@xxxxxxxxxx>
> Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
> ---
>  mm/workingset.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/mm/workingset.c b/mm/workingset.c
> index 7ac2b88c80ae5..8412f4840ae35 100644
> --- a/mm/workingset.c
> +++ b/mm/workingset.c
> @@ -688,10 +688,9 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
>
>                 mem_cgroup_flush_stats_ratelimited(sc->memcg);
>                 lruvec = mem_cgroup_lruvec(sc->memcg, NODE_DATA(sc->nid));
> -

Blank line change is not necessary and I think it make the code a bit
more ugly...

>                 for (pages = 0, i = 0; i < NR_LRU_LISTS; i++)
> -                       pages += lruvec_lru_size(lruvec, i, MAX_NR_ZONES - 1);
> -
> +                       pages += lruvec_page_state_local(lruvec,
> +                                                        NR_LRU_BASE + i);
>                 pages += lruvec_page_state_local(
>                         lruvec, NR_SLAB_RECLAIMABLE_B) >> PAGE_SHIFT;
>                 pages += lruvec_page_state_local(

Just a nit pick.

Reviewed-by: Kairui Song <kasong@xxxxxxxxxxx>