On 9 March 2012 16:28, Rob Fay <[log in to unmask]> wrote:

Hi Alessandra,

On 09/03/2012 16:13, Alessandra Forti wrote:

Hi Rob,

This is what Manchester is doing following the Glue schema. Of course we loose
out when the cluster is half full but we try to keep it full and we use all the
24 slots so not being full is less systematic than what you want to do.

That's an option, but I don't think we'd really want to do that on our nodes. Aside from the increased contention for I/O, our benchmarking shows total HS06 not only virtually flatlines but actually goes down as you reach full hyperthreaded capacity on these boxes - the total HS06 for 24 runs is less than the total HS06 for 18 runs.

Sure, but if you mean you're actually benchmarking with HS06, there's a caveat to consider: real life performance of jobs (especially analysis jobs, which are more I/O, and less CPU, heavy) is not precisely HS06-like.

The real-life performance figures I've managed to get out of ATLAS's experimental monitoring system (built out of HammerCloud) suggest that performance for QMUL's hyperthreaded cores converges on 50% (from above) those of non-hyperthreaded cores, for their analysis load. This is somewhat better than the pessimistic figure that HS06 gives you (although I suspect production will look more like the HS06 figures).

Sam

Cheers,

Rob

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Robert Fay [log in to unmask]
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