LSF Version 7.3 - Platform LSF Configuration Reference

Feature: Preemptive scheduling
The preemptive scheduling feature allows a pending high-priority job to preempt a running
job of lower priority. The lower-priority job is suspended and is resumed as soon as possible.
Use preemptive scheduling if you have long-running, low-priority jobs causing high-priority
jobs to wait an unacceptably long time.
Contents
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About preemptive scheduling
•
Scope
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Configuration to enable preemptive scheduling
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Preemptive scheduling behavior
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Configuration to modify preemptive scheduling behavior
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Preemptive scheduling commands
About preemptive scheduling
Preemptive scheduling takes effect when two jobs compete for the same job slots. If a high-
priority job is pending, LSF can suspend a lower-priority job that is running, and then start
the high-priority job instead. For this to happen, the high-priority job must be pending in a
preemptive queue (a queue that can preempt other queues), or the low-priority job must belong
to a preemptable queue (a queue that can be preempted by other queues).
If multiple slots are required, LSF can preempt multiple jobs until sufficient slots are available.
For example, one or more jobs can be preempted for a job that needs multiple job slots.
A preempted job is resumed as soon as more job slots become available; it does not necessarily
have to wait for the preempting job to finish.
Preemptive
queue
Jobs in a preemptive queue can preempt jobs in any queue of lower priority,
even if the lower-priority queues are not specified as preemptable.
Preemptive queues are more aggressive at scheduling jobs because a slot
that is not available to a low-priority queue may be available by preemption
to a high-priority queue.
Preemptable
queue
Jobs in a preemptable queue can be preempted by jobs from any queue of
a higher priority, even if the higher-priority queues are not specified as
preemptive.
When multiple preemptable jobs exist (low-priority jobs holding the
required slots), and preemption occurs, LSF preempts a job from the least-
loaded host.
Scope
Preemptive scheduling does not apply to jobs that have been forced to run or backfill and
exclusive jobs.
Feature: Preemptive scheduling
46 Platform LSF Configuration Reference