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

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Date:	Mon, 07 Sep 2009 08:54:46 +0200
From:	Mike Galbraith <efault@....de>
To:	Anirban Sinha <ASinha@...gmasystems.com>
Cc:	Lucas De Marchi <lucas.de.marchi@...il.com>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>
Subject: RE: question on sched-rt group allocation cap: sched_rt_runtime_us

On Sun, 2009-09-06 at 17:18 -0700, Anirban Sinha wrote:
> 
> 
> > Dunno.  Fly or die little patchlet (toss).
> 
> > sched: allow the user to disable RT bandwidth aggregation.
> 
> Hmm. Interesting. With this change, my results are as follows:
> 
> rt_runtime/rt_period   % of reg iterations
> 
> 0.2                    100%
> 0.25                   100%
> 0.3                    100%
> 0.4                    100%
> 0.5                    82%
> 0.6                    66%
> 0.7                    54%
> 0.8                    46%
> 0.9                    38.5%
> 0.95                   32%
> 
> 
> This results are on a quad core blade. Does it still makes sense
> though?
> Can anyone else run the same tests on a quadcore over the latest
> kernel? I will patch our 2.6.26 kernel with upstream fixes and rerun
> these tests on tuesday.

I tested tip (v2.6.31-rc9-1357-ge6a3cd0) with a little perturbation
measurement proglet on an isolated Q6600 core.

10s measurement interval results:

sched_rt_runtime_us  RT utilization
950000               94.99%
750000               75.00%
500000               50.04%
250000               25.02%
 50000                5.03%

Seems to work fine here.

	-Mike

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