[ https://issues.apache.org/jira/browse/YARN-4134?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Xianyin Xin reassigned YARN-4134: --------------------------------- Assignee: Xianyin Xin > FairScheduler preemption stops at queue level that all child queues are not > over their fairshare > ------------------------------------------------------------------------------------------------ > > Key: YARN-4134 > URL: https://issues.apache.org/jira/browse/YARN-4134 > Project: Hadoop YARN > Issue Type: Bug > Components: fairscheduler > Reporter: Xianyin Xin > Assignee: Xianyin Xin > > Now FairScheudler uses a choose-a-candidate method to select a container from > leaf queues that to be preempted, in {{FSParentQueue.preemptContainer()}}, > {code} > readLock.lock(); > try { > for (FSQueue queue : childQueues) { > if (candidateQueue == null || > comparator.compare(queue, candidateQueue) > 0) { > candidateQueue = queue; > } > } > } finally { > readLock.unlock(); > } > // Let the selected queue choose which of its container to preempt > if (candidateQueue != null) { > toBePreempted = candidateQueue.preemptContainer(); > } > {code} > a candidate child queue is selected. However, if the queue's usage isn't over > it's fairshare, preemption will not happen: > {code} > if (!preemptContainerPreCheck()) { > return toBePreempted; > } > {code} > A scenario: > {code} > root > / \ > queue1 queue2 > / \ > queue2.3, ( queue2.4 ) > {code} > suppose there're 8 containers, and queues at any level have the same weight. > queue1 takes 4 and queue2.3 takes 4, so both queue1 and queue2 are at their > fairshare. Now we submit an app in queue2.4 with 4 containers needs, it > should preempt 2 from queue2.3, but the candidate-containers selection > procedure will stop at queue1, so none of the containers will be preempted. -- This message was sent by Atlassian JIRA (v6.3.4#6332)