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Date:	Wed, 05 Dec 2007 15:53:59 -0500
From:	Jie Chen <chen@...b.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	linux-kernel@...r.kernel.org, Eric Dumazet <dada1@...mosbay.com>,
	Ingo Molnar <mingo@...e.hu>,
	Simon Holm Th??gersen <odie@...aau.dk>
Subject: Re: Possible bug from kernel 2.6.22 and above

Peter Zijlstra wrote:
> On Wed, 2007-11-21 at 15:34 -0500, Jie Chen wrote:
> 
>> It is clearly that the synchronization overhead increases as the number 
>> of threads increases in the kernel 2.6.21. But the synchronization 
>> overhead actually decreases as the number of threads increases in the 
>> kernel 2.6.23.8 (We observed the same behavior on kernel 2.6.22 as 
>> well). This certainly is not a correct behavior. The kernels are 
>> configured with CONFIG_SMP, CONFIG_NUMA, CONFIG_SCHED_MC, 
>> CONFIG_PREEMPT_NONE, CONFIG_DISCONTIGMEM set. The complete kernel 
>> configuration file is in the attachment of this e-mail.
>>
>>  From what we have read, there was a new scheduler (CFS) appeared from 
>> 2.6.22. We are not sure whether the above behavior is caused by the new 
>> scheduler.
> 
> If I read this correctly, you say that: .22 is the first bad one right?
> 
> The new scheduler (CFS) was introduced in .23, so it seems another
> change would be responsible for this.
> 
> 
> 
Hi, Peter:

Yes. We did observe this in 2.6.22. Thank you.

-- 
###############################################
Jie Chen
Scientific Computing Group
Thomas Jefferson National Accelerator Facility
12000, Jefferson Ave.
Newport News, VA 23606

(757)269-5046 (office) (757)269-6248 (fax)
chen@...b.org
###############################################

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