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Deadline Constraint Scheduling
Deadline constraints
Deadline constraints will suspend or terminate running jobs at a certain time. There are 2 kinds of deadline constraints:
- A run window, specified at the queue level, suspends a running job
-
A termination time, specified at the job level (
bsub -t), terminates a running job
Time-based resource usage limits
- A CPU limit, specified at job or queue level, terminates a running job when it has used up a certain amount of CPU time.
- A run limit, specified at the job or queue level, terminates a running job after it has spent a certain amount of time in the RUN state.
How deadline constraint scheduling works
If deadline constraint scheduling is enabled, LSF will not place a job that will be interrupted by a deadline constraint before its run limit expires, or before its CPU limit expires, if the job has no run limit. In this case, deadline constraint scheduling could prevent a job from ever starting. If a job has neither a run limit nor a CPU limit, deadline constraint scheduling has no effect.
Deadline constraint scheduling only affects the placement of jobs. Once a job starts, if it is still running at the time of the deadline, it will be suspended or terminated because of the deadline constraint or resource usage limit.
Disabling deadline constraint scheduling
Deadline constraint scheduling is enabled by default. To disable it for a queue,
set IGNORE_DEADLINE=y in lsb.queues.
LSF will schedule jobs in the liberal queue without observing the deadline
constraints.
Begin Queue QUEUE_NAME = liberal IGNORE_DEADLINE=y End Queue
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Exclusive Scheduling
About exclusive scheduling
Exclusive scheduling gives a job exclusive use of the host that it runs on. LSF dispatches the job to a host that has no other jobs running, and does not place any more jobs on the host until the exclusive job is finished.
How exclusive scheduling works
When an exclusive job (bsub -x) is submitted to an exclusive queue
(EXCLUSIVE = Y in lsb.queues) and dispatched to a host, LSF locks the host
(lockU status) until the job finishes.
LSF cannot place an exclusive job unless there is a host that has no jobs running on it.
To make sure exclusive jobs can be placed promptly, configure some hosts to run one job at a time. Otherwise, a job could wait indefinitely for a host in a busy cluster to become completely idle.
An exclusive job cannot preempt another job, and cannot be preempted by another job.
Configuring an exclusive queue
To configure an exclusive queue, set EXCLUSIVE in the queue definition
(lsb.queues) to Y.
Configuring a host to run one job at a time
To make sure exclusive jobs can be placed promptly, configure some single-
processor hosts to run one job at a time. To do so, set SLOTS=1 and HOSTS=all
in lsb.resources.
Submitting an exclusive job
To submit an exclusive job, use the -x option of bsub and submit the job to
an exclusive queue.
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Date Modified: January 12, 2004
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