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23.0 Preemption > Preemption tasks > Using QoS preemption

Conventions

23.1.6 Using QoS preemption

ClosedContext

This section breaks down how to configure the moab.cfg file to set up preemption with QoS. Using QoS, you can specify preemption rules and control access to preemption privileges by using the QFLAGS PREEMPTEE and PREEMPTOR credentials. For information about the PREEMPTEE and PREEMPTOR flags, see Preemption flags.

QoS-based preemption only occurs when the following three conditions are satisfied:

  • The preemptor job has the PREEMPTOR value set.
  • The preemptee job has the PREEMPTEE value set.
  • The preemptor job has a higher priority than the preemptee job.

To configure moab.cfg for QoS preemption

  1. Set GUARANTEEDPREEMPTION to TRUE. (This causes Moab to lock PREEMPTOR jobs until JOBRETRYTIME expires.)
  2. Make sure that JOBNODEMATCHPOLICY is not set to EXACTNODE, which is not currently supported for preemption (for more information, see Testing and troubleshooting preemption).
  3. If it is not already, set NODEACCESSPOLICY to SHARED.
  4. Set the PREEMPTPOLICY policy type (for more information, see PREEMPTPOLICY types).
  5. Set up QFLAGS to mark jobs as PREEMPTEE (a lower-priority job that can be preempted by a higher-priority job), or as PREEMPTOR (a higher-priority job that can preempt a lower-priority job). As in the example:
    6. QOSCFG[test1] QFLAGS=PREEMPTEE MEMBERULIST=<user> PRIORITY=100
QOSCFG[test2] QFLAGS=PREEMPTOR MEMBERULIST=<user> PRIORITY=10000

    For more information, see Preemption flags.

  6. Make sure that the PREEMPTEE job has a lower priority than the PREEMPTOR job. As in the example:
    7. QOSCFG[test1] QFLAGS=PREEMPTEE MEMBERULIST=<user> PRIORITY=100
QOSCFG[test2] QFLAGS=PREEMPTOR MEMBERULIST=<user> PRIORITY=10000

For example:

GUARANTEEDPREEMPTION TRUE
PREEMPTPOLICY <policy>
 
QOSCFG[test1] QFLAGS=PREEMPTEE MEMBERULIST=<user> PRIORITY=100
QOSCFG[test2] QFLAGS=PREEMPTOR MEMBERULIST=<user> PRIORITY=10000

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