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

[Jie Chen <chen@jlab.org>]

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
>
> 	Ingo
Hi, Ingo:

Yes, the extra 9 usecs overhead for running two threads in the 2.6.24 
kernel when there are total of 8 cores (2 quad opterons). What is the 
total number of cores do you have? I do not have machines that have dual 
quad Xeons here for direct comparisons. Thank you.

--
#############################################################################
# Jie Chen
# Scientific Computing Group
# Thomas Jefferson National Accelerator Facility
# Newport News, VA 23606
#
# chen@jlab.org
# (757)269-5046 (office)
# (757)269-6248 (fax)
#############################################################################
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/