[Beowulf] [gorelsky at stanford.edu: CCL:dual-coreOpteron275performance]

[Kozin, I (Igor)]

taskset is part of schedutils by Robert Love http://rlove.org/schedutils/

> >> But now for 4cores/2CPUs per Opteron node to force the using of
> >> only 2 cores (from 4), by 1 for each chip, we'll need to have
> >> cpu affinity support in Linux.
> >
> >Mikhail,
> >you can use "taskset" for that purpose. 
> >For example, (perhaps not in the most elegant form)
> >	mpiexec  -n 1 taskset -c 0 $code : -n 1 taskset -c 2 $code
> >But I doubt you want to let the idle cores to do something else 
> >in the mean time. However small you will generally see an increase 
> >in performance if you use all the cores.
> 
> Thanks !
> AFAIK, taskset isn't a part of numactl package. Sorry, where is 
> possible to download taskset ?
> 
> What is about using of all the cores, you are, of course, in
> general right ;-)
> But there may be some cases where using of "pairs of cores" on Opteron
> is bad under parallelization. For example, test178/RHF on the same
> G03 w/Linda, gave more worse performance on 2 cores than for 1 core
> (because of extra memory traffic).
> And, again at least theoretically, I may "occupy" 2 (free) of total
> 4 cores in 2-chip server for example w/some independed cache-friendly 
> tasks.
> 
> Yours
> Mikhail  
>    
> 
> Yours
> Mikhail
> 
> 
> 
> >
> >Best,
> >Igor
> >
> >
> >I. Kozin  (i.kozin at dl.ac.uk)
> >CCLRC Daresbury Laboratory
> >tel: 01925 603308
> >http://www.cse.clrc.ac.uk/disco
> >Distributed Computing Forum
> >http://www.cse.clrc.ac.uk/disco/forums/ubbthreads.php?Cat=0
> >
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