CPU time and run time normalization

To set the CPU time limit and run time limit for jobs in a platform-independent way, LSF scales the limits by the CPU factor of the hosts involved. When a job is dispatched to a host for execution, the limits are then normalized according to the CPU factor of the execution host.

Whenever a normalized CPU time or run time is given, the actual time on the execution host is the specified time multiplied by the CPU factor of the normalization host then divided by the CPU factor of the execution host.

If ABS_RUNLIMIT=Y is defined in lsb.params or in lsb.applications for the application associated with your job, the run time limit and run time estimate are not normalized by the host CPU factor. Absolute wall-clock run time is used for all jobs submitted with a run time limit or a run time estimate.

Parent topic: Runtime Resource Usage Limits

Normalization host

If no host or host model is given with the CPU time or run time, LSF uses the default CPU time normalization host defined at the queue level (DEFAULT_HOST_SPEC in lsb.queues) if it has been configured, otherwise uses the default CPU time normalization host defined at the cluster level (DEFAULT_HOST_SPEC in lsb.params) if it has been configured, otherwise uses the submission host.

Example

CPULIMIT=10/hostA

If hostA has a CPU factor of 2, and hostB has a CPU factor of 1 (hostB is slower than hostA), this specifies an actual time limit of 10 minutes on hostA, or on any other host that has a CPU factor of 2. However, if hostB is the execution host, the actual time limit on hostB is 20 minutes (10 * 2 / 1).

Normalization hosts for default CPU and run time limits

The first valid CPU factor encountered is used for both CPU limit and run time limit. To be valid, a host specification must be a valid host name that is a member of the LSF cluster. The CPU factor is used even if the specified limit is not valid.

If the CPU and run limit have different host specifications, the CPU limit host specification is enforced.

If no host or host model is given with the CPU or run time limits, LSF determines the default normalization host according to the following priority:

  1. DEFAULT_HOST_SPEC is configured in lsb.queues

  2. DEFAULT_HOST_SPEC is configured in lsb.params

  3. If DEFAULT_HOST_SPEC is not configured in lsb.queues or lsb.params, host with the largest CPU factor is used.

CPU time display (bacct, bhist, bqueues)

Normalized CPU time is displayed in the output of bqueues. CPU time is not normalized in the output if bacct and bhist.