linux-kernel - Re: RFC: documentation of the autogroup feature

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Date:   Tue, 29 Nov 2016 14:46:15 +0100
From:   Mike Galbraith <efault@....de>
To:     mtk.manpages@...il.com
Cc:     Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        linux-man <linux-man@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: RFC: documentation of the autogroup feature

On Tue, 2016-11-29 at 10:10 +0100, Michael Kerrisk (man-pages) wrote:
> Let's try and go further. How's this:
> 
>        When scheduling non-real-time  processes  (i.e.,  those  scheduled
>        under  the SCHED_OTHER, SCHED_BATCH, and SCHED_IDLE policies), the
>        CFS scheduler employs a technique known as "group scheduling",  if
>        the  kernel was configured with the CONFIG_FAIR_GROUP_SCHED option
>        (which is typical).
> 
>        Under group scheduling, threads are scheduled  in  "task  groups".
>        Task  groups  have  a  hierarchical relationship, rooted under the
>        initial task group on the system, known as the "root task  group".
>        Task groups are formed in the following circumstances:
> 
>        *  All of the threads in a CPU cgroup form a task group.  The par‐
>           ent of this task group is the task group of  the  corresponding
>           parent cgroup.
> 
>        *  If  autogrouping  is  enabled, then all of the threads that are
>           (implicitly) placed in an autogroup (i.e., the same session, as
>           created by setsid(2)) form a task group.  Each new autogroup is
>           thus a separate task group.  The root task group is the  parent
>           of all such autogroups.
> 
>        *  If  autogrouping  is enabled, then the root task group consists
>           of all processes in the root CPU cgroup that were not otherwise
>           implicitly placed into a new autogroup.
> 
>        *  If  autogrouping is disabled, then the root task group consists
>           of all processes in the root CPU cgroup.
> 
>        *  If group scheduling was disabled (i.e., the kernel was  config‐
>           ured  without  CONFIG_FAIR_GROUP_SCHED),  then  all of the pro‐
>           cesses on the system are notionally placed  in  a  single  task
>           group.

Notionally works for me.

	-Mike