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Status Delivered
Workspace Spectrum LSF
Created by Guest
Created on Apr 28, 2020

RELATED IDEAS

Prevention of Spectrum LSF over-preemption

See this idea on ideas.ibm.com

The current LSF preemption design does not prevent over-preemption (i.e. preempt more jobs than needed). When the preemption of a large low job takes some time like several minutes, the following incoming high priority jobs could preempt other running jobs even if the ongoing preemption would release enough resource for them eventually.



We hope over-preemption can be prevented. Scheduler can check if the resources to be released by the ongoing preemptions is enough for the incoming high priority jobs. If it is, then preemption will not be triggered immediately for the high priority jobs, they will wait for some configurable time for the finish of the ongoing preemptions, and preempt only when the timer expires.



Below is an example of over-preemption. There are 3 queues with priorities prod > preprod > devonprod. "JOB_CONTROLS=TERMINATE[SIGTERM]" and "TERMINATE_WHEN=PREEMPT" are set in the queues.



J1: bsub -q preprod -n 3 sleep 2000

J2: bsub -q preprod -n 3 sleep 2000

J3: bsub -n 30 -q devonprod "sh /scratch/support/gordonc/tmp/trap.sh" <<< the preemption of this job would take 100sec



Following jobs are submitted after J 1 ~ 3 are running



J4: bsub -q prod sleep 1000

J5: bsub -q prod sleep 1000

J6: bsub -q prod sleep 1000

J7: bsub -q prod sleep 1000

J8: bsub -q prod sleep 1000

J9: bsub -q prod sleep 1000



J4 would preempt J3. Some jobs among J5~9 would preempt J1 and/or J2, and eventually J3 will be preempted too.

  • Guest
    Reply
    |     Sep 10, 2020

    The observed behavior, while undesirable in your situation, is correct. If a job is taking too long to free up resources, the scheduler will try to get the resources from elsewhere.

    As an alternative, have you considered using the Planner capability that was released in LSF 10 Service Pack 6? This effectively makes the scheduler more deterministic/less aggressive, and will ensure that once a decision is made to schedule a job on resource ABC, it will stick to that decision, even if it is less optimal.

    https://www.ibm.com/support/knowledgecenter/SSWRJV_10.1.0/lsf_release_notes/lsf_relnotes_jobschedulingexecution10.1.0.6.html

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