linux-kernel - Re: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28

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Message-ID: <4926FBBB.3050002@cosmosbay.com>
Date:	Fri, 21 Nov 2008 19:19:39 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...e.hu>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Mike Galbraith <efault@....de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [Bug #11308] tbench regression on each kernel release from 2.6.22
 -&gt; 2.6.28

Eric Dumazet a écrit :
> Christoph Lameter a écrit :
>> AIM9 results:
>>         TCP        UDP
>> 2.6.22        104868.00    489970.03
>> 2.6.28-rc5    110007.00    518640.00
>> net-next    108207.00    514790.00
>>
>> net-next looses here for some reason against 2.6.28-rc5. But the numbers
>> are better than 2.6.22 in any case.
>>
> 
> I found that on current net-next, running oprofile in background can 
> give better bench
> results. Thats really curious... no ?
> 
> 
> So the single loop on close(socket()), on all my 8 cpus is almost 10% 
> faster if oprofile
> is running... (20 secs instead of 23 secs)
> 

Oh well, thats normal, since when a cpu is interrupted by a NMI, and
distracted by oprofile code, it doesnt fight with other cpus on dcache_lock
and other contended cache lines...


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