linux-kernel - Re: [stable] scheduler nice 19 versus 'idle' behavior / static low-priority scheduling

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Date:	Mon, 09 Feb 2009 07:19:36 -0800
From:	Brian Rogers <brian@...w.org>
To:	Greg KH <greg@...ah.com>
CC:	Mike Galbraith <efault@....de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jan Engelhardt <jengelh@...ozas.de>,
	Ingo Molnar <mingo@...e.hu>,
	Nathanael Hoyle <nhoyle@...letech.com>,
	stable <stable@...nel.org>
Subject: Re: [stable] scheduler nice 19 versus 'idle' behavior / static	low-priority
 scheduling

Greg KH wrote:
> On Sat, Jan 31, 2009 at 10:08:13AM +0100, Mike Galbraith wrote:
>   
>> On Sat, 2009-01-31 at 06:38 +0100, Mike Galbraith wrote:
>>     
>>> On Fri, 2009-01-30 at 14:12 -0800, Brian Rogers wrote:
>>>       
>>>> Mike Galbraith wrote:
>>>>         
>>>>> On Fri, 2009-01-30 at 02:59 -0500, Nathanael Hoyle wrote:
>>>>>   
>>>>>           
>>>>>> I am running foldingathome under it at the moment, and it seems to be
>>>>>> improving the situation somewhat, but I still need/want to test with
>>>>>> Mike's referenced patches.
>>>>>>     
>>>>>>             
>>>>> You will most definitely encounter evilness running SCHED_IDLE tasks in
>>>>> a kernel without the SCHED_IDLE fixes.
>>>>>   
>>>>>           
>>>> Speaking of SCHED_IDLE fixes, is 
>>>> 6bc912b71b6f33b041cfde93ca3f019cbaa852bc going to be put into the next 
>>>> stable 2.6.28 release? Without it on 2.6.28.2, I can still produce 
>>>> minutes-long freezes with BOINC or other idle processes.
>>>>
>>>> With the above commit on top of 2.6.28.2 and also 
>>>> cce7ade803699463ecc62a065ca522004f7ccb3d, the problem is solved, though 
>>>> I assume cce7ad isn't actually required to fix that, and I can test that 
>>>> if desired.
>>>>         
>>> I think they both should go to stable, but dunno if they're headed that
>>> direction or not.
>>>
>>> One way to find out, CCs added.
>>>       
>> For those who may want to run SCHED_IDLE tasks in .27, I've integrated
>> and lightly tested the fixes required to do so.  One additional commit
>> was needed to get SCHED_IDLE vs nice 19 working right, namely f9c0b09.
>> Without that, SCHED_IDLE tasks received more CPU than nice 19 tasks.
>>
>> Since .27 is in long-term maintenance, I'd integrate into stable, but
>> that's not my decision.  Anyone who applies the below to their stable
>> kernel gets to keep all the pieces should something break ;-)
>>     
>
> I'm going to hold off and not do this, as it seems too risky.
>
> But thanks for the pointers, perhaps someone else will want to do this
> for their distro kernels if they have problems with this.
>   

Is this statement meant to apply to both 2.6.27 and 2.6.28, or just 2.6.27?

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