[Beowulf] Re: Opteron 275 performance
philippe.blaise at cea.fr
Thu Jul 28 08:42:40 PDT 2005
Hopefully, you show that dual core is quite superior to
"hyper"-threading for some scientific programs,
and is cost-friendly, very nice ! but page 14 you write
"It is worth noting that since AMBER8 does consume significant memory
memory contention issue that could reduce overall performance on a AMD
processor based 2p/4c system under heavy memory usage shows a small
effect, at most".
Please, what do you mean by "significant memory bandwith" ? may be no
more than 50 % ?
have you got an estimation value ?
Joe Landman wrote:
> Hi Steve:
> Not knowing the details of your calculations might be an issue, but
> you can read about our experiences with a number of chemistry and
> informatics codes on dual core Opteron systems. See
> http://enterprise2.amd.com/downloadables/Dual_Core_Performance.pdf for
> more details.
> Steve Cousins wrote:
>> On Thu, 14 Jul 2005 11:25:12 +0100 Igor Kozin wrote:
>>> But now for 4cores/2CPUs per Opteron node to force the using of
>>>> only 2 cores (from 4), by 1 for each chip, we'll need to have
>>>> cpu affinity support in Linux.
>>> you can use "taskset" for that purpose. For example, (perhaps not in
>>> the most elegant form)
>>> mpiexec -n 1 taskset -c 0 $code : -n 1 taskset -c 2 $code
>>> But I doubt you want to let the idle cores to do something else in
>>> the mean time. However small you will generally see an increase in
>>> performance if you use all the cores.
>> We are considering getting a Dual Dual-Core Opteron system vs. two Dual
>> Opteron systems. We like the ability to use all four cores on one model
>> but a lot of what we'll do is have two models running at the same time,
>> each using two cores.
>> We are worried that running two models on one system with four cores
>> model using two cores) will not work as well as using two systems, each
>> with two cores/cpu's. Is this what you were refering to (Igor) when you
>>> But I doubt you want to let the idle cores to do something else
>>> in the mean time.
>> We have an 8 CPU SGI Origin 3200 that has no problem doing this sort of
>> thing. I'm just curious what the implications are of doing this with
>> Dual Core Opteron cpu's.
>> Steve Cousins, Ocean Modeling Group Email: cousins at umit.maine.edu
>> Marine Sciences, 208 Libby Hall http://rocky.umeoce.maine.edu
>> Univ. of Maine, Orono, ME 04469 Phone: (207) 581-4302
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