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Re: MT anomaly... [message #15845 is a reply to message #15844]

Sun, 11 May 2008 19:43

mirek
Messages: 14267
Registered: November 2005

Ultimate Member

tvanriper wrote on Sun, 11 May 2008 13:18

Maybe I'm totally off-base here, and I haven't looked at the code, but are you multi-threading at the kernel or user level?

If you're using the POSIX library calls, you're probably multi-threading through user level threading, which means you probably won't get at multiple cores. You're still multi-threading, but at the user level, you can't get at the other core; that requires a system call of some kind that most user level libraries know nothing about.

If you're using the system calls that Linux offers (kernel level threading), then I don't know why you're seeing this kind of performance; you should be seeing both cores used.

AFAIK, pthreads work through system threads.

In any case, 60% means I am actually USING another core...

Anyway, month later I think this is just example of contention problem...

Mirek

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