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In this section I try to explain how your job requests are treated on the
Inside a project, say, HEP 2016/1-4, it doesn't matter who you are, if you're member of the project your requests will be processed FIFO: first in, first out. The first to submit will be the first to have their jobs processed.
As long as the SLURM scheduler can find resources to match the ones requested by a job, the job will be started soon after being submitted.
But if there are no resources available, the job will have to wait in line and any job submitted earlier for the same project will have a higher priority due to a longer waiting time. There are some modifications of priority based on job size, but there is no priority or fair share among members of the same project.
It's as if all members were a single person submitting jobs, with many names.
The exception to this rule is that there are limits to how many jobs a single user can submit and how many resources a single user can utilise simultaneously. Thus, if a user has reached any of these limits, other members of the same project are still able to submit and run jobs within the bounds of similar, but higher limits for the project as a whole.
If the cluster is busy, requesting an interactive session may take time and fail. The scheduler will happily schedule resources for a user, but if the user asks for an interactive session with say 6 cores and there is no machine with 6 cores free, the scheduler cannot fulfil the request at the moment.
The scheduler treats an interactive job the same as a batch job, queueing it with the FIFO strategy described above. However, an exception to the FIFO scheduling appears when a parallel job is waiting for other jobs to finish and release resources. Then a short job can be promoted ahead of the queue, if it fits into an empty slot that is reserved for later use by the parallel job, so called backfill. Thus, queueing interactive jobs with shorter wall times have a higher probability of starting earlier.
Fairness is enforced among the three projects using the hep partition (HEP 2016/1-3, HEP 2016/1-4, HEP 2016/1-5) that means every project is allocated 1/3 of computing power (core/hours) per month. Once one project exceeds that 1/3, it will be harder for members of that project to get resources when the other projects are running, because there is a debt of computing power towards them.
This happens only when the cluster is being used intensively by all, which is quite rare at the moment of writing.
But if at some point each project is using a considerable amount of computing power, it is for sure that all project members will have to wait in the queue to be allocated. Remember that the allocation is what you ASK for in the sbatch script: once is allocated is yours and others cannot take it.