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Message-ID: <20120917164002.GA18677@google.com>
Date: Mon, 17 Sep 2012 09:40:02 -0700
From: Tejun Heo <tj@...nel.org>
To: Vivek Goyal <vgoyal@...hat.com>
Cc: containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org, Li Zefan <lizefan@...wei.com>,
Michal Hocko <mhocko@...e.cz>,
Glauber Costa <glommer@...allels.com>,
Peter Zijlstra <peterz@...radead.org>,
Paul Turner <pjt@...gle.com>,
Johannes Weiner <hannes@...xchg.org>,
Thomas Graf <tgraf@...g.ch>, Paul Mackerras <paulus@...ba.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
Neil Horman <nhorman@...driver.com>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
Serge Hallyn <serge.hallyn@...ntu.com>
Subject: Re: [RFC] cgroup TODOs
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
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