Hi Loris, On Mon, Nov 30, 2015 at 05:03:51AM -0800, Loris Bennett wrote:
> If jobs are sharing nodes, I would say it is desirable to be able to > distinguish between job which wants just any 128 cores and one which > wants 16 complete 8-core-nodes. The former, if cpu-intensive, might > well be able to fill up cores left empty by memory-intensive jobs; the > latter requires that complete nodes be drained to make space for it, > which can be a waste of resources. > > Because our nodes are shared, we usually try to talk users out of > specifying the number of nodes for MPI jobs, because the reduced > wait-time often makes up for any loss of efficiency due to the increased > spread across nodes and switches. Thanks for that insight. We don't have nodes sharing jobs, so the distinction doesn't come into play for us. But I can see how it would make a difference with shared nodes. I think for now we'll just have to watch the users and ask them to play nicely if it comes up again. :) Thanks, Paddy -- Paddy Doyle Trinity Centre for High Performance Computing, Lloyd Building, Trinity College Dublin, Dublin 2, Ireland. Phone: +353-1-896-3725 http://www.tchpc.tcd.ie/
