LSF Version 7.3 - Administering Platform LSF

Administering Platform LSF 405
C HAPTER
23
Reserving Resources
Contents
◆ About Resource Reservation on page 405
◆ Using Resource Reservation on page 406
◆ Memory Reservation for Pending Jobs on page 408
◆ Time-based Slot Reservation on page 410
◆ Viewing Resource Reservation Information on page 417
About Resource Reservation
When a job is dispatched, the system assumes that the resources that the job
consumes will be reflected in the load information. However, many jobs do not
consume the resources they require when they first start. Instead, they will typically
use the resources over a period of time.
For example, a job requiring 100 MB of swap is dispatched to a host having 150 MB
of available swap. The job starts off initially allocating 5 MB and gradually increases
the amount consumed to 100 MB over a period of 30 minutes. During this period,
another job requiring more than 50 MB of swap should not be started on the same
host to avoid over-committing the resource.
Resources can be reserved to prevent overcommitment by LSF. Resource
reservation requirements can be specified as part of the resource requirements
when submitting a job, or can be configured into the queue level resource
requirements.
How resource reservation works
When deciding whether to schedule a job on a host, LSF considers the reserved
resources of jobs that have previously started on that host. For each load index, the
amount reserved by all jobs on that host is summed up and subtracted (or added if
the index is increasing) from the current value of the resources as reported by the
LIM to get amount available for scheduling new jobs:
available amount = current value - reserved amount for all jobs