Re: AIM7 40% regression with 2.6.26-rc1

[Matthew Wilcox]

On Tue, May 06, 2008 at 01:48:24PM +0800, Zhang, Yanmin wrote:
> Comparing with kernel 2.6.25, ???AIM7 (use tmpfs) has ???more than 40% with 2.6.26-rc1
> on my 8-core stoakley, 16-core tigerton, and Itanium Montecito. Bisect located
> below patch.
> 
> 64ac24e738823161693bf791f87adc802cf529ff is first bad commit
> commit 64ac24e738823161693bf791f87adc802cf529ff
> Author: Matthew Wilcox <matthew@xxxxxx>
> Date:   Fri Mar 7 21:55:58 2008 -0500
> 
>     Generic semaphore implementation
> 
> 
> After I manually reverted the patch against 2.6.26-rc1 while fixing lots of
> conflictions/errors, aim7 regression became less than 2%.

40%?!  That's shocking.  Can you tell which semaphore was heavily
contended?  I have a horrible feeling that it's the BKL.

-- 
Intel are signing my paycheques ... these opinions are still mine
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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