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

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Date:	Thu, 16 Sep 2010 12:35:58 -0700
From:	Yinghai Lu <yinghai.lu@...cle.com>
To:	Greg KH <gregkh@...e.de>
CC:	Mike Galbraith <efault@....de>, 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 09/16/2010 07:42 AM, Greg KH wrote:
> 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.
> 

why not just revert that patch?

wonder if SLES11SP1 or RHEL 6 have this patch or not.

Yinghai

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