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Subject: Re: Try RC5 w/ HT

Author: Matthew White

Date: 13:53:57 05/24/03

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On May 23, 2003 at 23:40:23, Aaron Gordon wrote:

>>What are they measuring?
>>
>>IE running two copies _should_ see each copy run about 1/2 as fast with SMT
>>on, since each copy is getting roughly 50% of available cpu core resources
>>when running the same instruction streams.
>>
>>Or do you mean something else?
>
>It's keys per second for RC5, nodes per second for OGR. What I mean is it spawns
>1 thread per processor (or virtual processor in HT's case).
>My Dual Celeron 400MHz box gets an exact 2.00x speedup with this, I'm assuming
>because it doesn't hit the main memory at all. Any other dual processor system
>should also get a 2.00x speedup as well.. however I saw some results that were
>puzzling. Here they are...
>
>Dual Xeon (P4) 2.0GHz without HT - 2.8 million keys/sec per thread (5.6mk/s
>total), 2 threads total.
>
>Dual Xeon (P4) 2.0GHz with HT enabled - 0.72 million keys/sec per thread
>(2.88mk/s total), 4 threads total.
>
>I was just wondering if you could run the same tests and confirm this. I would
>have figured RC5/OGR would have managed a nice boost from HT, so it's surprising
>to me.
I have seen similarly poor performance on my Dual Xeon 2.4 GHz with HT enabled.
I manually configured the client to only spawn 2 threads.

Matt



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