Opteron kernel

Derek Richardson derek.richardson at pgs.com
Wed Nov 26 13:23:47 EST 2003

Sorry for the late reply, bloody Exchange server didn't drop it in my 
inbox until late this morning.  Memory and scheduling would probably be 
the biggest factor.  Processor affinity doesn't matter as much, because 
in my experience we haven't had problems w/ processes bouncing between 
CPUs.  PCI bus is almost a non-issue, since our application is 
embarassingly parallel and therefore has no need for > 100 Mbit 
ethernet, and there is no disk on a PCI-attached controller, so we have 
very little information passing over the PCI bus.
By interleaving, I assume you mean at the physical level, which I had a 
quick peek at when we got the system ( it's an IBM eServer 325, a loaner 
for testing ) and I assumed to be correct.  But given the poor 
performance I have seen ( 2 GHz Opterons coming in at ~15% slower than a 
3 GHz P4 on a compute/memory intensive application when most benchmarks 
I have seen would imply the inverse ), I will double-check that when 
given a chance.
I will probably just try the latest 2.6 kernel and a few other tweaks as 
well, and AMD has also offerred help, but that would more likely be at 
the application layer ( which I don't have control of, unfortunately ).
Thanks for the response, and my apologies for the vagueness of the question.
Derek R.

Donald Becker wrote:

>On Mon, 24 Nov 2003, Derek Richardson wrote:
>>Does anyone know where to find info on tuning the linux kernel for 
>>Opterons?  Googling hasn't turned up much useful information.
>What type of tuning?
>PCI bus transactions (the Itanium required more, but the Opteron still
>benefits)?  Scheduling?  Processor affinity?  What kernel version?
>If you ask specific questions, there is likely someone on the list that
>knows the specific answer.
>The easiest performance improvement comes from proper memory DIMM
>configuration to match the application layout.  Each processor has its
>own local memory controller, and understanding how the memory slots are
>filled and the options e.g. interleave can make a 30% difference on a
>dual processor system.

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derek.richardson at ieee.org
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