linux-kernel - Re: question on sched-rt group allocation cap: sched_rt_runtime

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Date:	Tue, 8 Sep 2009 00:08:31 -0700
From:	Anirban Sinha <ani@...rban.org>
To:	Anirban Sinha <ASinha@...gmasystems.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Galbraith <efault@....de>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>, Dario Faggioli <raistlin@...ux.it>
Cc:	Anirban Sinha <ani@...rban.org>
Subject: Re: question on sched-rt group allocation cap: sched_rt_runtime_us


On 2009-09-07, at 9:42 AM, Anirban Sinha wrote:

>
>
>
> -----Original Message-----
> From: Peter Zijlstra [mailto:a.p.zijlstra@...llo.nl]
> Sent: Mon 9/7/2009 12:59 AM
> To: Mike Galbraith
> Cc: Anirban Sinha; Lucas De Marchi; linux-kernel@...r.kernel.org;  
> Ingo Molnar
> Subject: Re: question on sched-rt group allocation cap:  
> sched_rt_runtime_us
>
> On Sun, 2009-09-06 at 08:32 +0200, Mike Galbraith wrote:
> > On Sat, 2009-09-05 at 19:32 -0700, Ani wrote:
> > > On Sep 5, 3:50 pm, Lucas De Marchi <lucas.de.mar...@...il.com>  
> wrote:
> > > >
> > > > Indeed. I've tested this same test program in a single core  
> machine and it
> > > > produces the expected behavior:
> > > >
> > > > rt_runtime_us / rt_period_us     % loops executed in SCHED_OTHER
> > > > 95%                              4.48%
> > > > 60%                              54.84%
> > > > 50%                              86.03%
> > > > 40%                              OTHER completed first
> > > >
> > >
> > > Hmm. This does seem to indicate that there is some kind of
> > > relationship with SMP. So I wonder whether there is a way to  
> turn this
> > > 'RT bandwidth accumulation' heuristic off.
> >
> > No there isn't..
>
> 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?

--Ani


>
>
>

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