Platform LSF Administration Guide Version 6.2

How Preemptive Scheduling Works
Administering Platform LSF
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Job slot limits specified at the queue level are never affected by preemptive scheduling;
they are always enforced for both running and suspended jobs.
Preemption of multiple job slots
If multiple slots are required, LSF can preempt multiple jobs, until sufficient slots are
available. For example, one or more jobs might be preempted for a job that needs
multiple job slots.
Preemption of parallel jobs
When a high-priority parallel job preempts multiple low-priority parallel jobs, sometimes
LSF preempts more low-priority jobs than are necessary to release sufficient job slots to
start the high-priority job.
Use the PREEMPT_FOR parameter in
lsb.params to enable the optimized
preemption of parallel jobs, so LSF preempts fewer of the low-priority parallel jobs.
See “Optimized Preemption of Parallel Jobs” on page 457 for more information.