Message-ID: <492AC715.9080602@nortel.com>
Date: Mon, 24 Nov 2008 09:24:05 -0600
From: "Chris Friesen" <cfriesen@nortel.com>
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To: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Dhaval Giani <dhaval@linux.vnet.ibm.com>, bharata@linux.vnet.ibm.com,
       linux-kernel@vger.kernel.org,
       Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
       Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH] sched: Don't allow priority switch to realtime when the
 task doesn't belong to init_task_group and when CONFIG_RT_GROUP_SCHED isn't
 set
References: <20081120061854.GA4349@in.ibm.com>	 <1227402676.7685.19942.camel@twins> <20081124035807.GA3278@in.ibm.com>	 <1227515526.7685.21861.camel@twins>	 <20081124084644.GA26526@linux.vnet.ibm.com> <1227517575.7685.21906.camel@twins>
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Peter Zijlstra wrote:
> On Mon, 2008-11-24 at 14:16 +0530, Dhaval Giani wrote:
> 
> 
>>Which would mean the init_task_group becase it contains those tasks which are
>>not grouped.
> 
> 
> Only because of implementation details (we implement the !group case by
> having them all part of a single group), conceptually they don't belong
> to any group, hence talking about moving it to some group is just wrong.

> Furthermore your statement shows another misconception, a group of
> ungrouped tasks doesn't make sense.

Arguably there is such a group, which is "the set of all RT tasks".

Whether or not they should map to the top-level cgroup is a different 
question.  Maybe in the !group case there should be a second top-level 
"rt" cgroup?  We could even make the RT sched tuning knobs available there.

Chris

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