Bibin A Chundatt created YARN-3627:

             Summary: Preemption not triggered in Fair scheduler when 
maxResources is set on parent queue
                 Key: YARN-3627
             Project: Hadoop YARN
          Issue Type: Bug
          Components: fairscheduler, scheduler
         Environment: Suse 11 SP3, 2 NM 
            Reporter: Bibin A Chundatt

Consider the below scenario of fair configuration 
Root (10Gb cluster resource)
--Q1 (maxResources  4gb) 
----Q1.1 (maxResources 4gb) 
----Q1.2  (maxResources  4gb)         
--Q2 (maxResources 6GB)
No applications are running in Q2
Submit one application with to Q1.1 with 50 maps  & 4Gb gets allocated to Q1.1
Now submit application to  Q1.2 the same will be starving for memory always.
Preemption will never get triggered since 
yarn.scheduler.fair.preemption.cluster-utilization-threshold =.8 and the 
cluster utilization is below .8.

  private boolean shouldAttemptPreemption() {
    if (preemptionEnabled) {
      return (preemptionUtilizationThreshold < Math.max(
          (float) rootMetrics.getAllocatedMB() / clusterResource.getMemory(),
          (float) rootMetrics.getAllocatedVirtualCores() /
    return false;

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