linux-kernel - Re: 2.6.32.y stable kernel regression with taskset

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Date:	Thu, 16 Sep 2010 07:42:16 -0700
From:	Greg KH <gregkh@...e.de>
To:	Mike Galbraith <efault@....de>
Cc:	Yinghai Lu <yinghai.lu@...cle.com>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	John Wright <john.wright@...com>
Subject: Re: 2.6.32.y stable kernel regression with taskset

On Thu, Sep 16, 2010 at 05:45:12AM +0200, Mike Galbraith wrote:
> On Wed, 2010-09-15 at 11:47 -0700, Yinghai Lu wrote:
> > found problem with cpuscaling test.
> > 
> > Under 2.6.32.21   Userspace gov  
> > min freq load test time is nearly the same as max freq load test time around  ~16 seconds
> > 
> > under 2.6.18-194
> > min freq load test time is ~40 seconds
> > max freq load test time	  is ~ 17 seconds
> > 
> > the test is 
> > 1. set governor for one cpu to userspace
> > 2. set freq to min for that cpu
> > 3. using taskset to put load test only on that cpu, and get the time for load test.
> > 
> > so that mean taskset did not put load test on cpu that we want. and other cpu still have ondemand governor and load test get done much faster
> > 
> > git bisect report:
> > 
> > c6fc81afa2d7ef2f775e48672693d8a0a8a7325d is the first bad commit
> > commit c6fc81afa2d7ef2f775e48672693d8a0a8a7325d
> > Author: John Wright <john.wright@...com>
> > Date:   Tue Apr 13 16:55:37 2010 -0600
> > 
> >     sched: Fix a race between ttwu() and migrate_task()
> 
> Known issue.  There's a sched series for 32-stable in the pipeline.

Yes, sorry, I'm working my way through to them, hope to have them
finished and applied soon.

thanks,

greg k-h
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