LSF Version 7.3 - Administering Platform LSF

Administering Platform LSF 511
Running Parallel Jobs
Minimum, default, and maximum processor limits
PROCLIMIT is specified in lsb.queues as:
PROCLIMIT = 4 6 9
◆ Minimum number of processors that can be allocated for this queue is 4
◆ Default number of processors for the queue is 6
◆ Maximum number of processors that can be allocated for this queue is 9
Reserving Processors
About processor reservation
When parallel jobs have to compete with sequential jobs for job slots, the slots that
become available are likely to be taken immediately by a sequential job. Parallel jobs
need multiple job slots to be available before they can be dispatched. If the cluster
is always busy, a large parallel job could be pending indefinitely. The more
processors a parallel job requires, the worse the problem is.
Processor reservation solves this problem by reserving job slots as they become
available, until there are enough reserved job slots to run the parallel job.
You might want to configure processor reservation if your cluster has a lot of
sequential jobs that compete for job slots with parallel jobs.
How processor reservation works
Processor reservation is disabled by default.
If processor reservation is enabled, and a parallel job cannot be dispatched because
there are not enough job slots to satisfy its minimum processor requirements, the
job slots that are currently available is reserved and accumulated.
A reserved job slot is unavailable to any other job. To avoid deadlock situations in
which the system reserves job slots for multiple parallel jobs and none of them can
acquire sufficient resources to start, a parallel job gives up all its reserved job slots
if it has not accumulated enough to start within a specified time. The reservation
Example Description
bsub -n 5 myjob The job myjob runs on 5 processors.
bsub -n 2 myjob The job myjob is rejected from the queue because the number of
processors requested is less than the minimum number of processors
configured for the queue (3).
bsub -n 4,5 myjob The job myjob runs on 4 or 5 processors.
bsub -n 2,6 myjob The job myjob runs on 3 to 6 processors.
bsub -n 4,9 myjob The job myjob runs on 4 to 8 processors.
bsub myjob The default number of processors is equal to the minimum number (3).
The job
myjob runs on 3 processors.
Example Description
bsub myjob Because a default number of processors is configured, the job myjob runs
on 6 processors.