Re: Bizarre x86 segment layout problem causing select() slowdown
Re: Bizarre x86 segment layout problem causing select() slowdown
- Subject: Re: Bizarre x86 segment layout problem causing select() slowdown
- From: John Daniel <email@hidden>
- Date: Mon, 5 Feb 2007 21:20:02 -0600
As soon as I sent this I had an epiphany. You may not have context
switch issues at all. Whatever you are doing with segment sizes may
be causing you to go into or out of actual parallel execution of your
code. It is the same type of issue, just lots more complicated and
harder to debug.
One thing you might try instead of Shark is Thread Viewer. It is
still a sampler-type tool, but you can pause your program and see
where each thread is and has been (relative to the sampling, of
course). I have used Thread Viewer and have gotten meaningful results
from it.
John
On Feb 5, 2007, at 8:57 PM, John Daniel wrote:
I think that changing the size of segments, adding no-ops, and
adding an empty function is changing the behavior of your problem.
It is changing the point at which a context switch occurs. Do you
have a clear handle on which specific parts of code can be run by
multiple threads? Remember, a dual-core x86 processor is going to
have radically different behavior than a PPC in these spots. I
think that is where you need to look.
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