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From "Wangda Tan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-5540) scheduler spends too much time looking at empty priorities
Date Tue, 13 Sep 2016 00:42:20 GMT

    [ https://issues.apache.org/jira/browse/YARN-5540?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15485794#comment-15485794

Wangda Tan commented on YARN-5540:

Thanks [~jlowe], patch generally looks good, only a few minor comments: 
1) It might be better to rename add/removeSchedulerKeyReference to increase/decreaseSchedulerKeyReference
since schedulerKey ref will not be removed unless value == 0. 
2) Do you think we should remove:
bq. // TODO: Shouldn't we activate even if numContainers = 0?

> scheduler spends too much time looking at empty priorities
> ----------------------------------------------------------
>                 Key: YARN-5540
>                 URL: https://issues.apache.org/jira/browse/YARN-5540
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: capacity scheduler, fairscheduler, resourcemanager
>    Affects Versions: 2.7.2
>            Reporter: Nathan Roberts
>            Assignee: Jason Lowe
>         Attachments: YARN-5540.001.patch, YARN-5540.002.patch
> We're starting to see the capacity scheduler run out of scheduling horsepower when running
500-1000 applications on clusters with 4K nodes or so.
> This seems to be amplified by TEZ applications. TEZ applications have many more priorities
(sometimes in the hundreds) than typical MR applications and therefore the loop in the scheduler
which examines every priority within every running application, starts to be a hotspot. The
priorities appear to stay around forever, even when there is no remaining resource request
at that priority causing us to spend a lot of time looking at nothing.
> jstack snippet:
> {noformat}
> "ResourceManager Event Processor" #28 prio=5 os_prio=0 tid=0x00007fc2d453e800 nid=0x22f3
runnable [0x00007fc2a8be2000]
>    java.lang.Thread.State: RUNNABLE
>         at org.apache.hadoop.yarn.server.resourcemanager.scheduler.SchedulerApplicationAttempt.getResourceRequest(SchedulerApplicationAttempt.java:210)
>         - eliminated <0x00000005e73e5dc0> (a org.apache.hadoop.yarn.server.resourcemanager.scheduler.common.fica.FiCaSchedulerApp)
>         at org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.LeafQueue.assignContainers(LeafQueue.java:852)
>         - locked <0x00000005e73e5dc0> (a org.apache.hadoop.yarn.server.resourcemanager.scheduler.common.fica.FiCaSchedulerApp)
>         - locked <0x00000003006fcf60> (a org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.LeafQueue)
>         at org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.ParentQueue.assignContainersToChildQueues(ParentQueue.java:527)
>         - locked <0x00000003001b22f8> (a org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.ParentQueue)
>         at org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.ParentQueue.assignContainers(ParentQueue.java:415)
>         - locked <0x00000003001b22f8> (a org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.ParentQueue)
>         at org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityScheduler.allocateContainersToNode(CapacityScheduler.java:1224)
>         - locked <0x0000000300041e40> (a org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityScheduler)
> {noformat}

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