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https://issues.apache.org/jira/browse/YARN-6215?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15881721#comment-15881721
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Tao Jie commented on YARN-6215:
-------------------------------
[~kasha] thank you for you comment!
I understand your concern. It may bring some performance loss if we add a
read-lock, but it is risky if we don't. Doing preemption when fairshare of
queues is incomplete would not only miss containers that should be preempted,
but also may preempt containers that should not be preempted by mistake. It
would be unpredictable.
In earlier FS code, updating fairshare and preempting containers took place in
one thread, so I think a readlock here would not make the performance worse.
> TestFairSchedulerPreemption.testPreemptionBetweenNonSiblingQueues fails in
> trunk
> --------------------------------------------------------------------------------
>
> Key: YARN-6215
> URL: https://issues.apache.org/jira/browse/YARN-6215
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: fairscheduler, test
> Reporter: Sunil G
> Assignee: Tao Jie
> Attachments: YARN-6215.001.patch
>
>
> *Error Message*
> Incorrect number of containers on the greedy app expected:<4> but was:<8>
> Failed test case
> [link|https://builds.apache.org/job/PreCommit-YARN-Build/15038/testReport/org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair/TestFairSchedulerPreemption/testPreemptionBetweenNonSiblingQueues_FairSharePreemptionWithDRF_/]
> *Stacktrace*
> {noformat}
> java.lang.AssertionError: Incorrect number of containers on the greedy app
> expected:<4> but was:<8>
> at org.junit.Assert.fail(Assert.java:88)
> at org.junit.Assert.failNotEquals(Assert.java:743)
> at org.junit.Assert.assertEquals(Assert.java:118)
> at org.junit.Assert.assertEquals(Assert.java:555)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.TestFairSchedulerPreemption.verifyPreemption(TestFairSchedulerPreemption.java:282)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.TestFairSchedulerPreemption.testPreemptionBetweenNonSiblingQueues(TestFairSchedulerPreemption.java:323)
> {noformat}
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