linux-kernel - Re: Possible bug from kernel 2.6.22 and above, 2.6.24-rc4

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Message-ID: <20071211212352.GF6902@elte.hu>
Date:	Tue, 11 Dec 2007 22:23:52 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jie Chen <chen@...b.org>
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: Possible bug from kernel 2.6.22 and above, 2.6.24-rc4


* Jie Chen <chen@...b.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
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