Re: altix cpu set support

On Jan 26, 2007, at 11:01 AM, Malcolm Tobias wrote:

> Brock,
>
> On Friday 26 January 2007 09:06, you wrote:
> > Any tips would be helpful!   Or insight into the benefits of
> > cpusets.  I understand the thory.  But I so far see no difference.
> > (manually setting with dplace)
>
> Greetings.  I've been running an Altix for years, but went with  
> PBSPro because
> at the time it was the only queuing system that supported cpusets.

Yeah we are aware that pbsPro supports it, I found some posts about  
work going into torque which we use on all our clusters.

> When you see no difference using cpusets, you mean there's no  
> performance
> difference between running with cpusets and without?

Yes our test is a collection of codes,  the system we are evaluating  
has 16 useable cores,  For example if i run a 8 cpu without placement  
(no dplace)   vs with dplace i see no runtime change over the few  
hour long run.  I will try and force the system to push processes  
around.  But so far i have not seen a difference,

>   You'll only see
> performance hits if the OS migrates one of the processes from one  
> CPU to
> another.  The cost of doing this also depends on how much memory  
> each process
> is using.

One test was a abaqus model,  it was using 24GB of ram (system is  
equipped with 64GB) Even when using /dev/shm as scratch (another  
20GB  total 44 GB ram used)  I see no change.

> Malcolm
>
> --
> Malcolm Tobias
> 314.362.1594