Re: Possible bug from kernel 2.6.22 and above

[Peter Zijlstra]

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.



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