From: Muchun Song <muchun.song@linux.dev>
To: bingfangguo@tencent.com
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Shakeel Butt <shakeel.butt@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
Dave Chinner <david@fromorbit.com>, Qi Zheng <qi.zheng@linux.dev>,
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>,
David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>, Bingfang Guo <bfguo@icloud.com>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/4] memcg: keep swap charging under RCU protection
Date: Fri, 18 Sep 2026 20:07:59 +0800 [thread overview]
Message-ID: <CEA43253-5A6F-46EF-A7CF-645D5EC95E05@linux.dev> (raw)
In-Reply-To: <20260918-bingfangguo-memcgid-rework-v1-1-5bbf3220d88f@tencent.com>
> On Sep 18, 2026, at 17:18, Bingfang Guo via B4 Relay <devnull+bingfangguo.tencent.com@kernel.org> wrote:
>
> From: Bingfang Guo <bingfangguo@tencent.com>
>
> This is a preparatory work for unbinding memcgid from memcg. No
> functional change.
>
> The swap charging path currently drops its RCU read lock after acquiring
> a private ID reference. This is safe because the ID reference pins the
> memcg's CSS.
>
> Moving private ID references to objcgs will remove that lifetime
> guarantee. Keep the RCU read lock held while accessing the memcg for
> counter charging, statistics and failure handling. (This matches what
> __memcg1_swapout() already does.).
>
> Save the private ID before dropping the RCU read lock, and use the saved
> value when recording the swap entry. The swap cluster locking remains
> outside the RCU read-side critical section.
>
> Signed-off-by: Bingfang Guo <bingfangguo@tencent.com>
Acked-by: Muchun Song <muchun.song@linux.dev>
Thanks.
next prev parent reply other threads:[~2026-09-18 12:08 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-18 9:18 [PATCH 0/4] memcg: move memcgid refcount to objcg to unpin dying memcgs Bingfang Guo via B4 Relay
2026-09-18 9:18 ` Bingfang Guo
2026-09-18 9:18 ` [PATCH 1/4] memcg: keep swap charging under RCU protection Bingfang Guo via B4 Relay
2026-09-18 9:18 ` Bingfang Guo
2026-09-18 12:07 ` Muchun Song [this message]
2026-09-18 16:46 ` Shakeel Butt
2026-09-18 17:51 ` Bingfang Guo
2026-09-18 9:18 ` [PATCH 2/4] memcg: base swap charge accounting on memcgid root status Bingfang Guo via B4 Relay
2026-09-18 9:18 ` Bingfang Guo
2026-09-19 2:56 ` Muchun Song
2026-09-18 9:18 ` [PATCH 3/4] memcg: manipulate memcg private ID references by ID Bingfang Guo via B4 Relay
2026-09-18 9:18 ` Bingfang Guo
2026-09-18 18:14 ` Shakeel Butt
2026-09-18 18:46 ` Bingfang Guo
2026-09-18 20:24 ` Shakeel Butt
2026-09-20 10:07 ` Bingfang Guo
2026-09-19 3:06 ` Muchun Song
2026-09-18 9:18 ` [PATCH 4/4] memcg: move memcg private ID refcount to objcg Bingfang Guo via B4 Relay
2026-09-18 9:18 ` Bingfang Guo
2026-09-18 18:19 ` Shakeel Butt
2026-09-18 19:14 ` Bingfang Guo
2026-09-19 3:32 ` Muchun Song
2026-09-20 10:08 ` Bingfang Guo
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