On Aug 10, 2009, at 23:07 , Tom Elken wrote:
Summary:
IBM, SGI and Platform have some comparisons on clusters with "SMT
On" of running 1 rank for every core compared to running 2 ranks on
every core. In general, on low core-counts, like up to 32 there is
about an 8% advantage for running 2 ranks per core. At larger core
counts, IBM published a pair of results on 64 cores where the 64-
rank performance was equal to the 128-rank performance. Not all of
these applications scale linearly, so on some of them you lose
efficiency at 128 ranks compared to 64 ranks.
Details: Results from this year are mostly on Nehalem:
http://www.spec.org/mpi2007/results/res2009q3/ (IBM)
http://www.spec.org/mpi2007/results/res2009q2/ (Platform)
http://www.spec.org/mpi2007/results/res2009q1/ (SGI)
(Intel has results with Turbo mode turned on and off
in the q2 and q3 results, for a different comparison)
Or you can pick out the Xeon 'X5570' and 'X5560' results from the
list of all results:
http://www.spec.org/mpi2007/results/mpi2007.html
In the result index, when
" Compute Threads Enabled" = 2x "Compute Cores Enabled", then you
know SMT is turned on.
In these cases, you can then check that when
" MPI Ranks" = " Compute Threads Enabled" then you are running 2
ranks per core.
Tom,
Thanks for the neatly compiled information above. I can just add, that
I have conducted a fairly detailed analysis of Nehalem compared to
HarperTown in my paper An evaluation of Intel’s core i7 architecture
using a comparative approach presented at ISC´09. Here, I look at
different aspect of the memory hierarchy of the two processors. The
benefits from hyperthreading on the said 13 SPEC MPI2007 applications
are also studied, although using only a single node, where the
advantage is more pronounced
Thanks,
Håkon
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