linux-kernel - Re: [PATCH v2 cgroup/for-4.15-fixes] cgroup: add warning about RT not being supported on cgroup2

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Message-ID: <CAKgNAkgGNp_ByeMK52tAyGwB=zvr=HUS5LiYoODC44_xLS_8AA@mail.gmail.com>
Date:   Tue, 5 Dec 2017 19:53:51 +0100
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Lennart Poettering <lennart@...ttering.net>
Subject: Re: [PATCH v2 cgroup/for-4.15-fixes] cgroup: add warning about RT not
 being supported on cgroup2

On 5 December 2017 at 19:29, Tejun Heo <tj@...nel.org> wrote:
> From f0a821260f24ea9378ed0e0c149e3bbc1a1bd008 Mon Sep 17 00:00:00 2001
> From: Tejun Heo <tj@...nel.org>
> Date: Tue, 5 Dec 2017 09:10:17 -0800
>
> We haven't yet figured out what to do with RT threads on cgroup2.
> Document the limitation.
>
> v2: Included the warning about system management software behavior as
>     suggested by Michael.
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Reported-by: "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
> ---
>  Documentation/cgroup-v2.txt | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
> index 779211f..c5e3c21 100644
> --- a/Documentation/cgroup-v2.txt
> +++ b/Documentation/cgroup-v2.txt
> @@ -898,6 +898,13 @@ controller implements weight and absolute bandwidth limit models for
>  normal scheduling policy and absolute bandwidth allocation model for
>  realtime scheduling policy.
>
> +WARNING: cgroup2 doesn't yet support control of realtime processes and
> +the cpu controller can only be enabled when all RT processes are in
> +the root cgroup.  Be aware that that system management software may

Sorry, there was a fault in my text: s/that that/that/

Thanks,

Michael



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/