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SubjectRe: Possible bug from kernel 2.6.22 and above, 2.6.24-rc4
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On Tue, 2007-12-11 at 17:11 -0500, Jie Chen wrote:
> Ingo Molnar wrote:
> > * 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
> >

On my dual socket AMD Athlon MP

2.6.20-13-generic

PARALLEL time = 22.751875 microseconds +/- 21.370942
PARALLEL overhead = 7.046595 microseconds +/- 24.370040

2.6.24-rc5

PARALLEL time = 17.365543 microseconds +/- 3.295133
PARALLEL overhead = 2.213722 microseconds +/- 4.797886


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