Re: [RFC] cgroup TODOs

[Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

Hello,

On Mon, Sep 17, 2012 at 11:05:18AM -0400, Vivek Goyal wrote:
> As a developer, I will be happy to support only one model and keep code
> simple. I am only concerned that for blkcg we have still not charted
> out a clear migration path. The warning message your patch is giving
> out will work only if we decide to not treat task and groups at same
> level.

It may not be enough but it still is in the right direction.

> > Another problem is that configuration isn't contained in cgroup
> > proper.  We need a way to assign weights to individual tasks which can
> > be somehow directly compared against group weights.  cpu cooks
> > priority for this and blkcg may be able to cook ioprio but it's nasty
> > and unobvious.  Also, let's say we grow network bandwidth controller
> > for whatever reason.  What value are we gonna use?
> 
> So if somebody cares about settting SO_PRIORITY for traffic originating
> from a tasks, move it into a cgroup. Otherwise they all get default
> priority.

I don't know.  Do we wanna add, say, prctl for memory weight too?

> So to me, leaving this decision to userspace based on their requirement
> makes sense.

Leaving too many decisions to userland is one of the reasons that got
us into this mess, so I'm not sold on flexibility for flexibility's
sake.

> Yes, creating a hidden group for tasks in current group should not be
> hard from implementation point of view. But again, I am concerned about
> configuration of hidden group and I also don't like the idea of taking
> flexibility away from user to treat tasks and group at same level.

I don't know.  Create a reserved directory for it?  I do like the idea
of taking flexibility away form user unless it's actually useful but
am a bit worried we might be too late for that. :(

Thanks.

-- 
tejun