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Date: Tue, 11 Dec 2007 22:23:52 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Jie Chen <chen@jlab.org>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: Possible bug from kernel 2.6.22 and above, 2.6.24-rc4
Message-ID: <20071211212352.GF6902@elte.hu>
References: <20071205210222.GA30089@elte.hu> <47572353.4040606@jlab.org> <20071206104318.GB30838@elte.hu> <47582367.6060602@jlab.org> <20071210105943.GA5370@elte.hu> <475D9BB5.20808@jlab.org> <20071211105149.GA24250@elte.hu> <475EAC81.1020408@jlab.org> <20071211155226.GA1056@elte.hu> <475EBD30.1010506@jlab.org>
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* Jie Chen <chen@jlab.org> wrote:

> The following is pthread_sync output for 2.6.21.7-cfs-v24 #1 SMP 
> kernel.

> 2 threads:

> PARALLEL time =       11.106580 microseconds +/- 0.002460
> PARALLEL overhead =    0.617590 microseconds +/- 0.003409

> Output for Kernel 2.6.24-rc4 #1 SMP

> PARALLEL time =              19.668450 microseconds +/- 0.015782
> PARALLEL overhead =           9.157945 microseconds +/- 0.018217

ok, so the problem is that this PARALLEL time has an additional +9 usecs 
overhead, right? I dont see this myself on a Core2 CPU:

PARALLEL time =                           10.446933 microseconds +/- 0.078849
PARALLEL overhead =                       0.751732 microseconds +/- 0.177446

	Ingo