[Beowulf] Can one Infiniband net support MPI and a parallel
hahn at mcmaster.ca
Thu Aug 14 09:44:07 PDT 2008
>> It appears we've averaged almost 77% utilisation
>> since the beginning of 2004 (when our current usage
>> system records begin).
> Thank you very much for the data point!
> I've insisted here that above 70% utilization is very good,
> given the random nature of demand and jobs on queues in the academia, etc.
that sounds very strange to me. do you really mean that
30% of your cpu time is idle? I wonder whether there could be a big
difference in methodology. for instance, if you're using an MPI library
(probably based on tcp) that doesn't spin-wait but blocks as for disk IO
say 20% of the time, then you might consider this to be 80% utilization.
an MPI that spin-waits might show 100% with the same perf/throughput.
70% utilization is terrible if you really mean "fraction of allocatable cpu
time occupied by jobs". that is at the job scheduler level, not at the
kernel scheduler level.
> However, some folks would want more than 90% efficiency to get happy.
I would be embarassed to have less than 90%. perhaps 70% would make sense
for a cluster dedicated to a small or narrowly-defined group. I find that
a sufficient userbase means you _always_ have something to run, of any
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