Jan-Frode Myklebust wrote:
> On 2007-04-04, Michael E. Thomadakis <miket@sc.tamu.edu> wrote:
>> More specifically, I would expect that SMT ON would benefit workload
>> mixes with high thread concurrency but with low contention on common
>> thread resources (L1/L2/L3 and functional units). For instance, I would
>> expect a cluster with a large number of distributed (and multithreaded)
>> processes running to benefit from SMT ON: twice as many h/w threads can
>> be active at a time, obviating the need for costly thread-switch.
>
> I did some benchmarking on a P5+ cluster last fall, and was
> quite surprised that SMT=ON (and 1 task per virtuall cpu vs.
> 1 task per physical cpu in SMT=OFF) was giving best performance
> on all the benchmarks we did. Even for 16 node (~250 task)
> mpi-jobs.
>
>
> -jf

Jan thanks for your reply. We have a 40 node p5-575 cluster with 32GB
DRAM/node. Nodes are attached to 2 planes of HPS. I was contending that
SMT ON should benefit the cluster since all of the cluster control
processes (RSCT, GPFS, HPS assistance, etc.) are heavily multi-threaded
and by not being compute-intensive, they should benefit from SMT ON.

Are there any public benchmarks that I can run to demonstrate the
benefits of SMT ?

thanks again,
Michael