Re: 3.9.5: much improved threading

Ian,

>> You will see only a small difference for 2-processor machines, but  
>> on 4 and 8 processor machines, the new threaded code can more than  
>> double your performance (assuming you  aren't on a loser OS like  
>> MacOS X or FreeBSD, that don't posses processor affinity).
>
>http://developer.apple.com/releasenotes/Performance/RN-AffinityAPI/

I gave this a quick scope, and it appears to be inadequate for what we
need, if I translate this page correctly.  It appears you guys are
following the horrible convention of calling one package a processor,
and that this page is then describing that you can use your affinity to
ensure one thread/package, but you cannot ensure one thread/core.  Is
this the case?

If so, you can definitely not do master last, and even persistant worker
will be messed up due to the scheduler moving things around within a
package.  Master and processor affinity (processor == core,
processor != package) can make a huge difference, as you can see:
   http://math-atlas.sourceforge.net/timing/newThr395/index.html

You can read about the techniques themselves in our IPDPS paper:
   http://www.cs.utsa.edu/~whaley/papers/ettIEEE.pdf

Is there any chance apple is going to provide core-level affinity sometime
soon?

Thanks,
Clint

**************************************************************************
** R. Clint Whaley, PhD ** Assist Prof, UTSA ** www.cs.utsa.edu/~whaley **
**************************************************************************

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