Bibin A Chundatt created YARN-3627:
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             Summary: Preemption not triggered in Fair scheduler when 
maxResources is set on parent queue
                 Key: YARN-3627
                 URL: https://issues.apache.org/jira/browse/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.
 
*Fairscheduler.java*

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





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