linux-kernel - Re: CFS review

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Date:	Tue, 28 Aug 2007 23:42:38 -0400
From:	Bill Davidsen <davidsen@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Al Boldi <a1426z@...ab.com>, Peter Zijlstra <peterz@...radead.org>,
	Mike Galbraith <efault@....de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: CFS review

Ingo Molnar wrote:
> * Al Boldi <a1426z@...ab.com> wrote:
> 
>>> ok. I think i might finally have found the bug causing this. Could 
>>> you try the fix below, does your webserver thread-startup test work 
>>> any better?
>> It seems to help somewhat, but the problem is still visible.  Even 
>> v20.3 on 2.6.22.5 didn't help.
>>
>> It does look related to ia-boosting, so I turned off __update_curr 
>> like Roman mentioned, which had an enormous smoothing effect, but then 
>> nice levels completely break down and lockup the system.
> 
> you can turn sleeper-fairness off via:
> 
>    echo 28 > /proc/sys/kernel/sched_features
> 
> another thing to try would be:
> 
>    echo 12 > /proc/sys/kernel/sched_features

14, and drop the granularity to 500000.
> 
> (that's the new-task penalty turned off.)
> 
> Another thing to try would be to edit this:
> 
>         if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
>                 p->se.wait_runtime = -(sched_granularity(cfs_rq) / 2);
> 
> to:
> 
>         if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
>                 p->se.wait_runtime = -(sched_granularity(cfs_rq);
> 
> and could you also check 20.4 on 2.6.22.5 perhaps, or very latest -git? 
> (Peter has experienced smaller spikes with that.)
> 
> 	Ingo


-- 
Bill Davidsen <davidsen@....com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
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