Qsub interactive job does not limit ncpu

Users/Site Administrators
1

Hi,

New to openpbs and just setup a pbs server with one pbs node. It took a while for me to figure out opening the ephemeral ports for interactive jobs to work.

My pbs node has ‘resources_available.ncpus = 256’.

When I try ‘qsub -I -l nodes=1:ppn=8’ I get the command prompt for the pbs worker node.
However, nproc shows 256.

Do interactive job automatically give you the resources for an entire node? Is it possible for 2 different users to have an interactive job on the same worker node sharing the resources (ie: CPUs or Mem)?

Thanks!

2

Please use the new syntax
qsub -I -l select=1:ncpus=8 <hit return>
check the output qstat -fx <of this jobid in another terminal> and qstat -answ1

The resource request via qsub for is for the scheduler to find a resource that can satisfy that request.
It would not restrict the user to user 8 cpu cores. If you would like to restrict then you would have to go through advance approach of PBS with Cgroups.

Yes, by default

3

Thank you for taking time to answer my questions.

Your answers are very helpful and informative! I will try your commands and I’ll try the Cgroups later at work!

1 Like
4

I read up on how to use cgroups with openpbs and added this to the pbs_cgroups.json and qmgr -c “import hook pbs_cgroups application/x-config default pbs_cgroups.json”

“cpu” : {
“enabled” : true,
“exclude_hosts” : ,
“exclude_vntypes” : ,
“enforce_per_period_quotas” : true
},

When I qsub -I -l select=1:ncpus=8, nproc still shows 256.
I ran stress -c 16 -t 60 and in top, I see 16 cpu threads go to 100% instead of 8.

Am I missing something?

Thanks!

5

Yes. You want to enable cpuset, not cpu.