Tim Prince <[log in to unmask]> 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.
>
> > Jeff
>
> --
> Tim Prince
|