linux-kernel - Re: [PATCH] cgroup: replace global percpu_rwsem with signal_struct->group

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Message-ID: <aLhykIPSGV1k_OG0@slm.duckdns.org>
Date: Wed, 3 Sep 2025 06:53:36 -1000
From: Tejun Heo <tj@...nel.org>
To: Yi Tao <escape@...ux.alibaba.com>
Cc: hannes@...xchg.org, mkoutny@...e.com, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cgroup: replace global percpu_rwsem with
 signal_struct->group_rwsem when writing cgroup.procs/threads

Hello,

On Wed, Sep 03, 2025 at 07:11:07PM +0800, Yi Tao wrote:
> As computer hardware advances, modern systems are typically equipped
> with many CPU cores and large amounts of memory, enabling the deployment
> of numerous applications. On such systems, container creation and
> deletion become frequent operations, making cgroup process migration no
> longer a cold path. This leads to noticeable contention with common
> process operations such as fork, exec, and exit.

If you use CLONE_INTO_CGROUP, cgroup migration doesn't just become cold. It
disappears completely and CLONE_INTO_CGROUP doesn't need any global locks
from cgroup side. Are there reasons why you can't use CLONE_INTO_CGROUP?

Thanks.

-- 
tejun