Re: AMD Magny-Cours

[Esztermann, Ansgar]

On Oct 21, 2010, at 21:54 , Steven Timm wrote:

> When Fermilab did our HW evaluation earlier this year we had
> Magny-Cours based machines, 12 core processors, available.  It did
> work but I don't know what if any tunes were done.

OK, I've found the culprit: we use only very little memory, so 16 GB/Node (4 
GB/Socket) is quite sufficient. These are actually two DIMMs, using only half 
of the available channels. This is not a problem in itself, but since the 
12-core CPUs are actually pairs of 6-core "nodes", one has to make sure that 
the memory is properly distributed: once we've populated Slots 1A and 3A 
(rather than 1A and 2A), performance was back to normal.

That said, there may be a slight difference (3% or so) between SL 5.4 and 5.5, 
but this would require some more careful checking.


A.

-- 
Ansgar Esztermann
DV-Systemadministration
Max-Planck-Institut für biophysikalische Chemie, Abteilung 105

Re: AMD Magny-Cours

[Steven Timm]

When Fermilab did our HW evaluation earlier this year we had
Magny-Cours based machines, 12 core processors, available.  It did
work but I don't know what if any tunes were done.

Steve


On Thu, 21 Oct 2010, Esztermann, Ansgar wrote:


Hi everyone,

can someone tell me what the support status of Magny-Cours is?
In upstream's release notes and knowledgebase, I have found some obscure (to 
me) notes stating that there is some support with 5.4, 2.6.18-164.9, some more 
with 5.5, and still more with 6.
Currently, we have a bunch of 6168-based 4-core machines here, and while they 
are quite stable with 5.4 and kernel 2.6.18-164.11.1, performance of our main 
hpc application is abysmal. It is 48-way multithreaded and yields hardly even 
half the expected performance; what is more, performance is varying from run to 
run by something like +/- 30%.


Thanks,

A.



--
--
Steven C. Timm, Ph.D  (630) 840-8525
t...@fnal.gov  http://home.fnal.gov/~timm/
Fermilab Computing Division, Scientific Computing Facilities,
Grid Facilities Department, FermiGrid Services Group, Assistant Group Leader.