Ingo Molnar wrote:
* Jie Chen <[email protected]> wrote:
Since I am using affinity flag to bind each thread to a different
core, the synchronization overhead should increases as the number of
cores/threads increases. But what we observed in the new kernel is the
opposite. The barrier overhead of two threads is 8.93 micro seconds vs
1.86 microseconds for 8 threads (the old kernel is 0.49 vs 1.86). This
will confuse most of people who study the
synchronization/communication scalability. I know my test code is not
real-world computation which usually use up all cores. I hope I have
explained myself clearly. Thank you very much.
btw., could you try to not use the affinity mask and let the scheduler
manage the spreading of tasks? It generally has a better knowledge about
how tasks interrelate.
Ingo
Hi, Ingo:
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.
--
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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)
[email protected]
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