Tim Prince wrote:
>On Sunday 23 February 2003 04:41, Jeffrey B. Layton wrote:
>
>
>>Tim Prince wrote:
>>
>>
>>>In my experience,
>>>'mpirun -np 2' on a single CPU P4 increases throughput by about 10% from
>>>-np 1, but that gain doesn't hold up for scaling to a large cluster with
>>>simple interconnects.
>>>
>>>
>>Tim,
>>
>> My experience agrees with yours. When I ran the NASA Parallel
>>Benchmarks on a Xeon cluster with even plain Fast Ethernet, it
>>was always faster to turn off HT (we did it at the kernel level and
>>at the BIOS level) These results are also supported by the following:
>>
>>http://computational-battery.org/Maskinvare/Hyperthreading.html
>>
>>
>>
>Apparently, those results were obtained with an early Xeon model with small
>cache. Not that I dare to judge the issue, but results like this, where
>simply turning on HT hurts performance, have sometimes been traced to errors
>in the BIOS.
>
Sorry, I didn't look too closely at the URL. However, our
results were on a Xeon 2.4 cluster that was tuned (correct
BIOS) we checked by running many benchmarks including
the Stream benchmarks to look for memory setting errors.
I haven't heard of problems in the BIOS causing the difference
between results with and without HT. Do you have any
references on this?
Thanks!
Jeff
>
>
>
>>Jeff
>>
>>
>
>--
>Tim Prince
>
>
>
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