[slurm-users] scheduling according time requirements

[Dietmar Rieder via slurm-users]

Hi,

is it possible to have slurm scheduling jobs automatical according to
the "-t" time requirements to a fitting partition?

e.g. 3 partitions

PartitionName=standard Nodes=c-[01-10] Default=YES MaxTime=04:00:00
DefaultTime=00:10:00 State=UP OverSubscribe=NO
PartitionName=medium Nodes=c-[04-08] Default=NO MaxTime=24:00:00
DefaultTime=04:00:00 State=UP OverSubscribe=NO
PartitionName=long Nodes=c-[09-10] Default=NO MaxTime=336:00:00
DefaultTime=24:00:00 State=UP OverSubscribe=NO


So in the standard partition which is the default we have all nodes and
a max time of 4h, in the medium partition we have 4 nodes with a max
time of 24h and in the long partition we have 2 nodes with a max time of
336h.

I was hoping that if I submit a job with -t 01:00:00 it can be run on
any node (standard partition), whereas when specifying -t 05:00:00 or -t
48:00:00 the job will run on the nodes of the medium or long partition
respectively.

However, my job will not get scheduled at all when -t is greater than
01:00:00

i.e.

]$ srun --cpus-per-task 1 -t 01:00:01 --pty bash
srun: Requested partition configuration not available now
srun: job 42095 queued and waiting for resources

it will wait forever because the standard partition is selected, I was
thinking that slurm would automatically switch to the medium partition.

Do I misunderstand something there? Or can this be somehow configured.

Thanks so much and sorry for the naive question
Dietmar

[Loris Bennett via slurm-users]

Hi Dietmar,

You can specify multiple partitions, e.g.

$ salloc --cpus-per-task=1 --time=01:00:01 --partition=standard,medium,long

Notice that rather than using 'srun ... --pty bash', as far as I
understand, the preferred method is to use 'salloc' as above, and to use
'srun' for starting MPI processes.

Cheers,

Loris

> Thanks so much and sorry for the naive question
> Dietmar

--
Dr. Loris Bennett (Herr/Mr)
FUB-IT (ex-ZEDAT), Freie Universität Berlin

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[Dietmar Rieder via slurm-users]

Hi Loris,

Thanks for the hint. This works nicely, but it would be nice that I
would not need to specify the partition at all. Any thoughts?


Dietmar

[Diego Zuccato via slurm-users]

Try adding to the config:
EnforcePartLimits=ANY
JobSubmitPlugins=all_partitions

Diego

--
Diego Zuccato
DIFA - Dip. di Fisica e Astronomia
Servizi Informatici
Alma Mater Studiorum - Università di Bologna
V.le Berti-Pichat 6/2 - 40127 Bologna - Italy
tel.: +39 051 20 95786

[Loris Bennett via slurm-users]

I am not aware that you can set multiple partition as a default.

The question is why you actually need partitions with different maximum
runtimes.

In our case, a university cluster with a very wide range of codes and
usage patterns, multiple partitions would probably lead to fragmentation
and wastage of resources due to the job mix not always fitting well to
the various partitions. Therefore, I am a member of the "as few
partitions as possible" camp and so in our set-up we have as essentially
only one partition with a DefaultTime of 14 days. We do however let
users set a QOS to gain a priority boost in return for accepting a
shorter run-time and a reduced maximum number of cores.

Occasionally people complain about short jobs having to wait in the
queue for too long, but I have generally been successful in solving the
problem by having them estimate their resource requirements better or
bundling their work in ordert to increase the run-time-to-wait-time
ratio.

Cheers,

Loris

[Dietmar Rieder via slurm-users]

Hi Diego,

thanks a lot, it seems to work as far as I was able to test now.

Dietmar

[Dietmar Rieder via slurm-users]

Hi Loris,

Diego suggested a possible way which seems to work after a quick test.

>
> The question is why you actually need partitions with different maximum
> runtimes.

we would like to have only a sub set of the nodes in a partition for
long running jobs, so that there are enough nodes available for short jobs.

The nodes for the long partition, however are also part of the short
partition so they can also be utilized when no long jobs are running.

That's our idea....

>
> In our case, a university cluster with a very wide range of codes and
> usage patterns, multiple partitions would probably lead to fragmentation
> and wastage of resources due to the job mix not always fitting well to
> the various partitions. Therefore, I am a member of the "as few
> partitions as possible" camp and so in our set-up we have as essentially
> only one partition with a DefaultTime of 14 days. We do however let
> users set a QOS to gain a priority boost in return for accepting a
> shorter run-time and a reduced maximum number of cores.

we didn't look into QOS yet, but this might also a way to go, thanks.

> Occasionally people complain about short jobs having to wait in the
> queue for too long, but I have generally been successful in solving the
> problem by having them estimate their resource requirements better or
> bundling their work in ordert to increase the run-time-to-wait-time
> ratio.
>

Dietmar

[Loris Bennett via slurm-users]

Yes, I wasn't aware of that, but it might also be useful for us, too.

>> The question is why you actually need partitions with different
>> maximum
>> runtimes.
>
> we would like to have only a sub set of the nodes in a partition for
> long running jobs, so that there are enough nodes available for short
> jobs.
>
> The nodes for the long partition, however are also part of the short
> partition so they can also be utilized when no long jobs are running.
>
> That's our idea....

If you have plenty of short running jobs, that is probably a reasonable
approach. On our system, the number of short running jobs would
probably tend to dip significantly over the weekend and public holidays,
so resources would potentially be blocked for the long running jobs. On
the other hand, long-running jobs on our system often run for days, so
one day here or there might not be so significant. And if the
long-running jobs were able to start in the short partition, they could
block short jobs.

The other thing to think about with regard to short jobs is backfilling.
With our mix of jobs, unless a job needs a large amount of memory or
number of cores, those with a run-time of only a few hours should be
backfilled fairly efficiently.

Regards

Loris

>> In our case, a university cluster with a very wide range of codes
>> and
>> usage patterns, multiple partitions would probably lead to fragmentation
>> and wastage of resources due to the job mix not always fitting well to
>> the various partitions. Therefore, I am a member of the "as few
>> partitions as possible" camp and so in our set-up we have as essentially
>> only one partition with a DefaultTime of 14 days. We do however let
>> users set a QOS to gain a priority boost in return for accepting a
>> shorter run-time and a reduced maximum number of cores.
>
> we didn't look into QOS yet, but this might also a way to go, thanks.
>
>> Occasionally people complain about short jobs having to wait in the
>> queue for too long, but I have generally been successful in solving the
>> problem by having them estimate their resource requirements better or
>> bundling their work in ordert to increase the run-time-to-wait-time
>> ratio.
>>
>
> Dietmar

[Thomas Hartmann via slurm-users]

Hi Dietmar,

I was facing quite similar requirements to yours. We ended up using QoS instead of partitions because this approach provides higher flexibility and more features. The basic distinction between the two approaches is that partitions are node-based while QoS are (essentially) resource based. So, instead of saying "Long jobs can only run on nodes 9 and 10" you would be able to say "Long jobs  can only use X CPU cores in total".

However, yes, your partition based approach is going to do the job, as long as you do not need any QoS based preemption.

Cheers,

Thomas

Am 30.04.24 um 16:00 schrieb Dietmar Rieder via slurm-users:

[Dietmar Rieder via slurm-users]

Dear Thomas,

the QoS seems really helpful, we'll look into it.
Perhaps as a starting point for us could you eventually translate my
simple example into a QoS config/setting?

Thanks so much
Dietmar

[Dietmar Rieder via slurm-users]

Hi Loris,

you are absolutely right, and I guess we will nee to optimize using QoS.
Thanks for your input and thoughts.