From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny-IBi9RG/b67k@public.gmane.org>
Subject: Re: [PATCH v2 09/10] sched/psi: per-cgroup PSI stats
 disable/re-enable interface
Date: Fri, 12 Aug 2022 12:14:44 +0200
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References: <20220808110341.15799-1-zhouchengming@bytedance.com>
 <20220808110341.15799-10-zhouchengming@bytedance.com>
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To: Chengming Zhou <zhouchengming-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>
Cc: hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, corbet-T1hC0tSOHrs@public.gmane.org, surenb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, vincent.guittot-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, dietmar.eggemann-5wv7dgnIgG8@public.gmane.org, rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org, bsegall-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, songmuchun-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org

Hello Chengming.

On Mon, Aug 08, 2022 at 07:03:40PM +0800, Chengming Zhou <zhouchengming-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org> wrote:
> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
> index dd84e34bc051..ade40506ab80 100644
> --- a/Documentation/admin-guide/cgroup-v2.rst
> +++ b/Documentation/admin-guide/cgroup-v2.rst
> @@ -968,6 +968,13 @@ All cgroup core files are prefixed with "cgroup."
>  	killing cgroups is a process directed operation, i.e. it affects
>  	the whole thread-group.
>  
> +  cgroup.psi
> +	A read-write single value file that allowed values are "0" and "1".
> +	The default is "1".
> +
> +	Writing "0" to the file will disable the cgroup PSI stats accounting.
> +	Writing "1" to the file will re-enable the cgroup PSI stats accounting.
> +

I'd suggest explaining here explicitely, this control attribute is not
hierarchical (i.e. PSI accounting in a cgroup does not affect accounting
in descendants and doesn't need pass enablement via ancestors from
root). And the purpose that it "saves" cycles (where).

Regards,
Michal