LSF Version 7.3 - Platform LSF Configuration Reference

Configuration to enable preemptive scheduling
The preemptive scheduling feature is enabled by defining at least one queue as preemptive or
preemptable, using the PREEMPTION parameter in the lsb.queues file. Preemption does
not actually occur until at least one queue is assigned a higher relative priority than another
queue, using the PRIORITY parameter, which is also set in the lsb.queues file.
Both PREEMPTION and PRIORITY are used to determine which queues can preempt other
queues, either by establishing relative priority of queues or by specifically defining preemptive
properties for a queue.
Configuration file Parameter and syntax Default behavior
lsb.queues
PREEMPTION=PREEMPTIV
E
•
Enables preemptive scheduling
•
Jobs in this queue can preempt jobs in any queue of
lower priority, even if the lower-priority queue is not
specified as preemptable
PREEMPTION=PREEMPTAB
LE
•
Enables preemptive scheduling
•
Jobs in this queue can be preempted by jobs from
any queue of higher priority, even if the higher-
priority queue is not specified as preemptive
PRIORITY=integer
•
Sets the priority for this queue relative to all other
queues
•
The larger the number, the higher the priority—a
queue with PRIORITY=99 has a higher priority than
a queue with PRIORITY=1
Preemptive scheduling behavior
Preemptive scheduling is based primarily on parameters specified at the queue level: some
queues are eligible for preemption, others are not. Once a hierarchy of queues has been
established, other factors determine which jobs from a queue should be preempted.
There are three ways to establish which queues should be preempted:
•
Based on queue priority—the PREEMPTION parameter defines a queue as preemptive or
preemptable and preemption is based on queue priority, where jobs from higher-priority
queues can preempt jobs from lower-priority queues
•
Based on a preferred order—the PREEMPTION parameter defines queues that can
preempt other queues, in a preferred order
•
Explicitly, by specific queues—the PREEMPTION parameter defines queues that can be
preempted, and by which queues
When …
The behavior is …
Preemption is not enabled—no queue is
defined as preemptable, and no queue is
defined as preemptive
•
High-priority jobs do not preempt jobs that are already running
A queue is defined as preemptable, but no
specific queues are listed that can preempt
it
•
Jobs from this queue can be preempted by jobs from any queue
with a higher value for priority
Feature: Preemptive scheduling
48 Platform LSF Configuration Reference