[Beowulf] [gorelsky at stanford.edu: CCL:dual-core Opteron 275performance]

[Alan Louis Scheinine]

Jakob Oestergaard wrote:
  > Guys, the results are very interesting - it would be very interesting to
  > know, too, which kernels you have been running on.

Four-cpu single core (Celestica): Linux version 2.6.7

Two nodes of a cluster (Tyan 2882), each node single core,
    sometimes the fastest of all, they have: Linux version 2.6.10

Two "chips" Opteron 875 on a board Tyan 2882, each chip dual core: Linux version 2.6.9-11.ELsmp
(The last from CentOS 4.1 with Red Hat June update.  By the way, the board has the 875
because the 275 was not available.)

In all cases the memory was 400 MHz DDR Registered ECC.

I'm not giving all the details such as CPU speed because I mostly wanted
to give a word of warning to do benchmarking on dual core in order to take into
consideration to memory bandwidth.  Towards the end of the day someone came
into my office to say that, instead of running an MPI job with 4 processes,
if he ran two MPI jobs each with 2 processes, the dual-core machine was
much better.  Evidently there is more to learn.

Jakob wrote: I'm pretty sure at least 2.6.12 had NUMA/dual-core fixes in it.
The CentOS 4.1 is very recent, being rebuilds, perhaps also Rocks Clusters
and Scientific Linux have 2.6.9-11.ELsmp -- I didn't check.  It is useful
to learn that we should upgrade to at least 2.6.12 to get important fixes
to NUMA.
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