Re: Possible bug from kernel 2.6.22 and above

[Jie Chen <chen@jlab.org>]

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.

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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@jlab.org
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