From p.dalgaard at biostat.ku.dk  Tue Mar  2 16:18:12 2004
From: p.dalgaard at biostat.ku.dk (Peter Dalgaard)
Date: Tue Mar  2 16:21:36 2004
Subject: [Rd] Some timings for 64 bit Opteron (ATLAS, GOTO, std)
In-Reply-To: <3A822319EB35174CA3714066D590DCD504AF78D7@usrymx25.merck.com>
References: <3A822319EB35174CA3714066D590DCD504AF78D7@usrymx25.merck.com>
Message-ID: <x2llmjwa4r.fsf@biostat.ku.dk>

"Liaw, Andy" <andy_liaw@merck.com> writes:

> Hi Martin,
> 
> When I attended the LinuxWorld Expo in NYC back in January, I chatted with
> some folks at the AMD booth, as well as guys from Penguin Computing (where
> we bought our Opteron box).  I was told that the Operton has this somewhat
> strange setup that the memory is controlled by one CPU.  The net effect of
> this being that when both CPUs are running, one might only be running at
> around 90% instead of 99%.  The `NUMA' kernel is supposed to fix this
> problem.  I wonder if this is related to the performance of the threaded
> GOTO lib that you saw.  Has anyone tried the NUMA kernel?
> 
> Best,
> Andy

My understanding is slightly different (I could be wrong though, I'm
hardly a hardware engineer): Each CPU controls one block of memory,
and only some motherboard have memory slots for both CPUs. If CPU2
wants to talk to CPU1's memory it has to ask CPU1 for it, with the
obvious potential for a performance hit.

I'll see if I can get around to redoing my Opteron builds and trying
Martin's benchmarks in the next couple of days.

        -p

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907


[Rd] Some timings for 64 bit Opteron (ATLAS, GOTO, std)
Peter Dalgaard