[Bro] So uh...how do you know which pin_cpus to use?

[Azoff, Justin S]

> On Oct 18, 2016, at 4:34 PM, James Lay <jlay at slave-tothe-box.net> wrote:
> 
> Never really understood this:
> 
> "The correct pin_cpus setting to use is dependent on your CPU 
> architecture. Intel and AMD systems enumerate processors in different 
> ways. Using the wrong pin_cpus setting can cause poor performance."
> 
> Is there a magical formula?  Any advice would help thanks.

The best thing to do is to install the hwloc package and use the lstopo or lstopo-no-graphics tool to render a big ascii art image of the system.


on centos7 this works:

lstopo-no-graphics  --of txt


You'll get something that looks like this:

https://www.open-mpi.org/projects/hwloc/lstopo/images/2XeonE5v2+2cuda+1display_v1.11.png

or

https://www.open-mpi.org/projects/hwloc/lstopo/images/4Opteron6200.v1.11.png

The numbers towards the bottom are the cpu ids.  So you can see that using something like

1,3,5,7,9,11,13,15,17,19,21,23,25

on an intel cpu would be the worst thing you could do since 21,23,25 are on the same physical cores as 1,3, and 5

-- 
- Justin Azoff