linux-kernel - Re: [RESEND PATCH] mm: bail out from partial cgroup_reclaim inside shrink

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Message-ID: <CABdmKX1NZJ5jOQH_9cxuxTVmn=CiCkXHK7rNrpvGBTT_+405Rw@mail.gmail.com>
Date: Wed, 11 Feb 2026 14:13:13 -0800
From: "T.J. Mercier" <tjmercier@...gle.com>
To: "zhaoyang.huang" <zhaoyang.huang@...soc.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Yu Zhao <yuzhao@...gle.com>, 
	Michal Hocko <mhocko@...nel.org>, Rik van Riel <riel@...riel.com>, 
	Shakeel Butt <shakeel.butt@...ux.dev>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	Zhaoyang Huang <huangzhaoyang@...il.com>, steve.kang@...soc.com
Subject: Re: [RESEND PATCH] mm: bail out from partial cgroup_reclaim inside shrink_lruvec

On Mon, Feb 9, 2026 at 9:44 PM zhaoyang.huang <zhaoyang.huang@...soc.com> wrote:
>
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>

Hi Zhaoyang,

> Nowadays, ANDROID system replaces madivse with memory.reclaim to implement
> user space memory management which desires to reclaim a certain amount of
> memcg's memory. However, oversized reclaiming and high latency are observed
> as there is no limitation over nr_reclaimed inside try_to_shrink_lruvec
> when MGLRU enabled. Besides, this could also affect all none root_reclaim
> such as reclaim_high etc.
> The commit 'b82b530740b9' ("mm: vmscan: restore incremental cgroup
> iteration") introduces sc->memcg_full_walk to limit the walk range of
> mem_cgroup_iter. This commit would like to make single memcg's scanning
> more precised by judging if nr_reclaimed reached when sc->memcg_full_walk
> not set.
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> ---
>  mm/vmscan.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 670fe9fae5ba..03bda1094621 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -4832,8 +4832,8 @@ static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc)
>         int i;
>         enum zone_watermarks mark;
>
> -       /* don't abort memcg reclaim to ensure fairness */
> -       if (!root_reclaim(sc))
> +       /* don't abort full walk memcg reclaim to ensure fairness */
> +       if (!root_reclaim(sc) && sc->memcg_full_walk)
>                 return false;

Can't we just get rid of this if (!root_reclaim(sc)) check entirely
now that commit 'b82b530740b9' ("mm: vmscan: restore incremental
cgroup
iteration") provides eventual fairness for the proactive reclaim case?
That wasn't true when this check was added initially.

Thanks,
T.J.