Administering Platform LSF - SAS

Reserving Memory for Pending Parallel Jobs
Reserving Memory for Pending Parallel Jobs
By default, the rusage string reserves resources for running jobs. Because
resources are not reserved for pending jobs, some memory-intensive jobs
could be pending indefinitely because smaller jobs take the resources
immediately before the larger jobs can start running. The more memory a job
requires, the worse the problem is.
Memory reservation for pending jobs solves this problem by reserving memory
as it becomes available, until the total required memory specified on the
rusage string is accumulated and the job can start. Use memory reservation
for pending jobs if memory-intensive jobs often compete for memory with
smaller jobs in your cluster.
Unlike slot reservation, which only applies to parallel jobs, memory reservation
applies to both sequential and parallel jobs.
Configuring memory reservation for pending parallel jobs
lsb.queues
Use the RESOURCE_RESERVE parameter in lsb.queues to reserve host
memory for pending jobs, as described in “Memory Reservation for Pending
Jobs” on page 272.
Set the RESOURCE_RESERVE parameter in a queue defined in lsb.queues.
The RESOURCE_RESERVE parameter overrides the SLOT_RESERVE parameter.
If both RESOURCE_RESERVE and SLOT_RESERVE are defined in the same
queue, job slot reservation and memory reservation are enabled and an error
is displayed when the cluster is reconfigured. SLOT_RESERVE is ignored.
Backfill on memory may still take place.
The following queue enables both memory reservation and backfill in the same
queue:
Begin Queue
QUEUE_NAME = reservation_backfill
DESCRIPTION = For resource reservation and backfill
PRIORITY = 40
RESOURCE_RESERVE = MAX_RESERVE_TIME[20]
BACKFILL = Y
End Queue
Enabling per-slot memory reservation
By default, memory is reserved for parallel jobs on a per-host basis. For
example, by default, the command:
% bsub -n 4 -R "rusage[mem=500]" -q reservation myjob
requires the job to reserve 500 MB on each host where the job runs.
To enable per-slot memory reservation, define
RESOURCE_RESERVE_PER_SLOT=y in lsb.params. In this example, if perslot
reservation is enabled, the job must reserve 500 MB of memory for each
job slot (4 * 500 = 2 GB) on the host in order to run.
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Administering Platform LSF