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Administering Platform LSF - SAS

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Configuring Preemptive Scheduling<br />

Queue 3 is preemptive and preemptable, so it can preempt jobs in all<br />

lower-priority queues (Queue 4), and its jobs can be preempted by all<br />

higher-priority queues (Queues 1 and 2).<br />

Configuring additional job slot limits for preemptive scheduling<br />

PREEMPT_FOR in<br />

lsb.params<br />

The following job slot limits are always affected by preemptive scheduling:<br />

◆ Total job slot limit for hosts, specified at the host level (SLOTS and HOSTS<br />

in lsb.resources)<br />

◆ Total job slot limit for individual users, specified at the user level (SLOTS<br />

and USERS in lsb.resources); by default, suspended jobs still count<br />

against the limit for user groups<br />

To configure additional job slot limits to be affected by preemptive scheduling,<br />

set PREEMPT_FOR in lsb.params, and use one or more of the following<br />

keywords to indicate that suspended jobs do not count against that job slot<br />

limit:<br />

◆ GROUP_MAX—total job slot limit for user groups, specified at the user<br />

level (MAX_JOBS in lsb.users); if preemptive scheduling is enabled,<br />

suspended jobs never count against the limit for individual users<br />

◆ HOST_JLU—total number of jobs for users and user groups, specified at<br />

the host level (JL/U in lsb.hosts)<br />

◆ USER_JLP—user-processor job slot limit for individual users, specified at<br />

the user level (JL/P in lsb.users)<br />

◆ GROUP_JLP—per-processor job slot limit for user groups, specified at the<br />

user level (JL/P in lsb.users)<br />

Job slot limits specified at the queue level are never affected by preemptive<br />

scheduling.<br />

Configuring preemptable queue preference<br />

For preemptive queues, you can specify which preemptable queues are<br />

considered first for preemption by configuring queue preference in the queue<br />

with the highest priority.<br />

To indicate the order of preference for the preemptable queues, put a plus sign<br />

(+) after the names of the preemptable queues and a preference level as a<br />

positive integer. Higher numbers indicate higher preferences for preempting a<br />

job in that queue. If no queue preference is specified, it is assumed to be 0. If<br />

there are multiple queues, <strong>LSF</strong> preempts jobs in the queue with the highest<br />

preference; queues at the same level of preference are ordered by queue<br />

priority.<br />

When preemtable queue preference is enabled, <strong>LSF</strong> considers jobs from<br />

preferred queues first instead of choosing running jobs based on best hosts:<br />

◆ Queues with a preference number are preferred over queues without a<br />

preference number<br />

◆ Queues with a higher preference number are preferred over queues with<br />

lower preference number<br />

182<br />

<strong>Administering</strong> <strong>Platform</strong> <strong>LSF</strong>

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