linux-kernel - Re: [RFC PATCH 0/2] support cgroup pool in v1

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Message-ID: <YTjmP0EGEWGYhroM@slm.duckdns.org>
Date:   Wed, 8 Sep 2021 06:35:11 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Yi Tao <escape@...ux.alibaba.com>
Cc:     gregkh@...uxfoundation.org, lizefan.x@...edance.com,
        hannes@...xchg.org, mcgrof@...nel.org, keescook@...omium.org,
        yzaikin@...gle.com, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        shanpeic@...ux.alibaba.com
Subject: Re: [RFC PATCH 0/2] support cgroup pool in v1

Hello,

On Wed, Sep 08, 2021 at 08:15:11PM +0800, Yi Tao wrote:
> In order to solve this long-tail delay problem, we designed a cgroup
> pool. The cgroup pool will create a certain number of cgroups in advance.
> When a user creates a cgroup through the mkdir system call, a clean cgroup
> can be quickly obtained from the pool. Cgroup pool draws on the idea of
> cgroup rename. By creating pool and rename in advance, it reduces the
> critical area of cgroup creation, and uses a spinlock different from
> cgroup_mutex, which reduces scheduling overhead on the one hand, and eases
> competition with attaching processes on the other hand.

I'm not sure this is the right way to go about it. There are more
conventional ways to improve scalability - making locking more granular and
hunting down specific operations which take long time. I don't think cgroup
management operations need the level of scalability which requires front
caching.

Thanks.

-- 
tejun