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SubjectRe: Possible bug from kernel 2.6.22 and above, 2.6.24-rc4
Ingo Molnar wrote:
> * Jie Chen <chen@jlab.org> wrote:
>
>> I just disabled the affinity mask and reran the test. There were no
>> significant changes for two threads (barrier overhead is around 9
>> microseconds). As for 8 threads, the barrier overhead actually drops a
>> little, which is good. Let me know whether I can be any help. Thank
>> you very much.
>
> sorry to be dense, but could you give me instructions how i could remove
> the affinity mask and test the "barrier overhead" myself? I have built
> "pthread_sync" and it outputs numbers for me - which one would be the
> barrier overhead: Reference_time_1 ?
>
> Ingo
Hi, Ingo:

To disable affinity, do configure --enable-public-release
--disable-thread_affinity. You should see barrier overhead like the
following:
Computing BARRIER time

Sample_size Average Min Max S.D. Outliers
20 19.486162 19.482250 19.491400 0.002740 0

BARRIER time = 19.486162 microseconds +/- 0.005371
BARRIER overhead = 8.996257 microseconds +/- 0.006575

The Reference_time_1 is the elapsed time for single thread doing simple
loop without any synchronization. Thank you.

--
###############################################
Jie Chen
Scientific Computing Group
Thomas Jefferson National Accelerator Facility
12000, Jefferson Ave.
Newport News, VA 23606
(757)269-5046 (office) (757)269-6248 (fax)
chen@jlab.org
###############################################


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