[slurm-users] Preferential scheduling on a subset of nodes

Paul Edmon pedmon at cfa.harvard.edu
Wed Dec 1 16:49:47 UTC 2021

If you set up a higher priority partition with Preemption OFF on the 
lower priority partition you should be able to accomplish this.  If you 
have preemption turned off for the specific partitions in question Slurm 
will not preempt but will schedule jobs from the higher priority 
partition first regardless of current fairshare scores. See:

    Mechanism used to preempt jobs or enable gang scheduling for this
    partition when *PreemptType=preempt/partition_prio* is configured.
    This partition-specific *PreemptMode* configuration parameter will
    override the cluster-wide *PreemptMode* for this partition. It can
    be set to OFF to disable preemption and gang scheduling for this
    partition. See also *PriorityTier* and the above description of the
    cluster-wide *PreemptMode* parameter for further details. 

This is at least how we manage that.

-Paul Edmon-

On 12/1/2021 11:32 AM, Sean McGrath wrote:
> Hi,
> Apologies for having to ask such a basic question.
> We want to be able to give some users preferential access to some
> nodes. They bought the nodes which are currently in a 'long' partition
> as their jobs need a longer walltime.
> When the purchasing users group is not using the nodes I would like
> other users to be able to run jobs on those nodes but when the owners
> group submit jobs I want those jobs to be queued as soon as currently
> running jobs on those nodes are finished. My understanding is that
> preemption won't work in these circumstances as it will either cancel or
> suspend currently running jobs, I want the currently running jobs to
> finish before the preferential ones start.
> I'm wondering if QOS could do what we need here. Can the following be
> sanity checked please.
> Put the specific nodes in both the long and the compute (standard)
> partition. Then restrict access to the long partition to specified users
> so that all users can access them in the compute queue but only a subset
> of users can use the longer wall time queue.
> $ scontrol update PartitionName=long Users=user1,user2
> We currently don't have QOS enabled so change that in slurm.conf and
> restart the slurmctld.
> -PriorityWeightQOS=0
> +PriorityWeightQOS=1
> Then create a qos and modify its priority
> $ sacctmgr add qos boost
> $ sacctmgr modify qos boost set priority=10
> $ sacctmgr modify user user1 set qos=boost
> Will that do what I expect please?
> Many thanks and again apologies for the basic question.
> Sean
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