Subject: Re: question on sched-rt group allocation cap: sched_rt_runtime_us
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Anirban Sinha <ani@anirban.org>
Cc: Anirban Sinha <ASinha@zeugmasystems.com>, Mike Galbraith <efault@gmx.de>,
       linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
       Dario Faggioli <raistlin@linux.it>
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Date: Tue, 08 Sep 2009 10:42:27 +0200
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On Tue, 2009-09-08 at 00:08 -0700, Anirban Sinha wrote:

> > Actually there is, use cpusets to carve the system into partitions.
> 
> hmm. ok. I looked at the code a little bit. It seems to me that the  
> 'borrowing' of RT runtimes occurs only from rt runqueues belonging to  
> the same root domain. And partition_sched_domains() is the only  
> external interface that can be used to create root domain out of a CPU  
> set. But then I think it needs to have CGROUPS/USER groups enabled?  
> Right?

No you need cpusets, you create a partition by disabling load-balancing
on the top set, thereby only allowing load-balancing withing the
children.

The runtime sharing is a form of load-balancing.

CONFIG_CPUSETS=y

Documentation/cgroups/cpusets.txt

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