linux-kernel - Re: [PATCH V2] Documentation: cgroups: Add notes on removing PIDs from tasks and cgroups requiring setup

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Message-Id: <20110311102328.19aa7c32.rdunlap@xenotime.net>
Date:	Fri, 11 Mar 2011 10:23:28 -0800
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Paul Menage <menage@...gle.com>
Cc:	Eric B Munson <emunson@...bm.net>, linux-doc@...r.kernel.org,
	containers@...ts.linux-foundation.org, rdunlap@...otime.net,
	linux-kernel@...r.kernel.org, kirill@...temov.name,
	mike@...rato.com
Subject: Re: [PATCH V2] Documentation: cgroups: Add notes on removing PIDs
 from tasks and cgroups requiring setup

On Thu, 10 Mar 2011 19:00:09 -0800 Paul Menage wrote:

> On Thu, Mar 10, 2011 at 9:07 AM, Eric B Munson <emunson@...bm.net> wrote:
> > The cgroup documentation does not specify how a process can be removed from a
> > particular group.  This patch adds a note at the end of the simple example
> > about how this is done.  Also, some cgroups (like cpusets) require user input
> > before a new group can be used.  This is noted in the patch as well.
> >
> > Signed-off-by: Eric B Munson <emunson@...bm.net>
> 
> Acked-by: Paul Menage <menage@...gle.com>

Applied to my documentation patch queue.  Thanks.


> > ---
> > Changes from V1:
> >  Rework the note about removing a process from a cgroup
> >  Add note about ns cgroup causing failure when moving processes between groups
> >
> >  Documentation/cgroups/cgroups.txt |   12 ++++++++++++
> >  1 files changed, 12 insertions(+), 0 deletions(-)
> >
> > diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
> > index 44b8b7a..cbdfb7d 100644
> > --- a/Documentation/cgroups/cgroups.txt
> > +++ b/Documentation/cgroups/cgroups.txt
> > @@ -349,6 +349,10 @@ To mount a cgroup hierarchy with all available subsystems, type:
> >  The "xxx" is not interpreted by the cgroup code, but will appear in
> >  /proc/mounts so may be any useful identifying string that you like.
> >
> > +Note: Some subsystems do not work without some user input first.  For instance,
> > +if cpusets are enabled the user will have to populate the cpus and mems files
> > +for each new cgroup created before that group can be used.
> > +
> >  To mount a cgroup hierarchy with just the cpuset and memory
> >  subsystems, type:
> >  # mount -t cgroup -o cpuset,memory hier1 /dev/cgroup
> > @@ -426,6 +430,14 @@ You can attach the current shell task by echoing 0:
> >
> >  # echo 0 > tasks
> >
> > +Note: Since every task is always a member of exactly one cgroup in each
> > +mounted hierarchy, to remove a task from its current cgroup you must
> > +move it into a new cgroup (possibly the root cgroup) by writing to the
> > +new cgroup's tasks file.
> > +
> > +Note: If the ns cgroup is active, moving a process to another cgroup can
> > +fail.
> > +
> >  2.3 Mounting hierarchies by name
> >  --------------------------------
> >
> > --
> > 1.7.1


---
~Randy
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