[slurm-users] Meaning of --cpus-per-task and --mem-per-cpu when SMT processors are used

[Loris Bennett]

Hi Alexander,

Alexander Grund <alexander.grund at tu-dresden.de> writes:

> Hi,
>
> we have a Power9 partition with 44 processors having 4 cores each
> totaling 176.
>
> `scontrol show node <node>` shows "CoresPerSocket=22" and "CPUTot=176"
> which confuses me. Especially as `whypending` reports e.g. "172 cores
> free: 1"

What's 'whypending'?

> So what are "CPUs" and what are "Cores" to SLURM? Why does it mix up those 2?

This is just historical as far as I can tell.  I think 'CPU' almost
always means 'core'.

> Most importantly: Does this mean `--cpus-per-task` can be as high as
> 176 on this node and `--mem-per-cpu` can be up to the reported
> "RealMemory"/176?

Yes.

Cheers,

Loris

-- 
Dr. Loris Bennett (Mr.)
ZEDAT, Freie Universität Berlin         Email loris.bennett at fu-berlin.de