From: Shakeel Butt <shakeel.butt@linux.dev>
To: Hui Zhu <hui.zhu@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@kernel.org>,
Qi Zheng <qi.zheng@linux.dev>, Lorenzo Stoakes <ljs@kernel.org>,
Kairui Song <kasong@tencent.com>, Barry Song <baohua@kernel.org>,
Axel Rasmussen <axelrasmussen@google.com>,
Yuanchu Xie <yuanchu@google.com>, Wei Xu <weixugc@google.com>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Hui Zhu <zhuhui@kylinos.cn>
Subject: Re: [PATCH v2 2/3] mm: memcg: redirect stats updates of dying memcgs for all hierarchies
Date: Thu, 3 Sep 2026 10:56:22 -0700 [thread overview]
Message-ID: <apm0nHGog6c0o3iO@linux.dev> (raw)
In-Reply-To: <0214c0228695db474b86d3b4778b681a6c47a6e2.1788169145.git.zhuhui@kylinos.cn>
On Mon, Aug 31, 2026 at 05:46:10PM +0800, Hui Zhu wrote:
> From: Hui Zhu <zhuhui@kylinos.cn>
>
> get_non_dying_memcg_start() redirects the stat updates of a dying memcg to
> its closest non-dying ancestor, but only on cgroup v1; on cgroup v2 the
> stats keep being accounted to the dying memcg itself.
>
> The previous patch restored lruvec_page_state_local() in
> count_shadow_nodes(), which reads those state_locals on cgroup v2 too, so
> apply the redirection to all hierarchies. Offlining is rare, so the added
> cost on the stat update fast path is limited to an rcu_read_lock() and a
> css_is_dying() check; the upward walk happens only while a memcg is dying.
>
> Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
Please CC to stable and add a sentence on user visible impact of the bug in the
commit message. With that:
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
next prev parent reply other threads:[~2026-09-03 17:56 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-31 9:46 [PATCH v2 0/3] mm: workingset: fix the shadow node budget under MGLRU Hui Zhu
2026-08-31 9:46 ` [PATCH v2 1/3] mm: workingset: use lruvec_page_state_local() to count lru pages Hui Zhu
2026-09-03 17:51 ` Shakeel Butt
2026-09-03 17:55 ` Shakeel Butt
2026-08-31 9:46 ` [PATCH v2 2/3] mm: memcg: redirect stats updates of dying memcgs for all hierarchies Hui Zhu
2026-09-03 17:52 ` Shakeel Butt
2026-09-03 17:56 ` Shakeel Butt [this message]
2026-08-31 9:46 ` [PATCH v2 3/3] mm: memcg: skip the RCU lock when the memcg is not dying Hui Zhu
2026-09-03 17:57 ` Shakeel Butt
2026-09-03 17:53 ` [PATCH v2 0/3] mm: workingset: fix the shadow node budget under MGLRU Shakeel Butt
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