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https://issues.apache.org/jira/browse/YARN-6487?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16782897#comment-16782897
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Wilfred Spiegelenburg commented on YARN-6487:
---------------------------------------------

It works both ways:

Before we can schedule we need to update the current usage and shares etc. This 
runs in an update thread. Continuous scheduling triggers that update. The 
heartbeats when they are processed do the same. This updating requires a lock 
of the scheduler as does the scheduling process itself. The extra update demand 
is the trigger/
So you get into a state that the heartbeat, the updates and the scheduling 
itself are all waiting for the lock. The larger the number of nodes, the larger 
the number of applications is (in most cases) and the larger the number of 
queues (again in most cases). All this combined causes processing to start 
lagging and the continuous scheduling really loses its function.

Node numbers influence continuous scheduling and the other way around.

> FairScheduler: remove continuous scheduling (YARN-1010)
> -------------------------------------------------------
>
>                 Key: YARN-6487
>                 URL: https://issues.apache.org/jira/browse/YARN-6487
>             Project: Hadoop YARN
>          Issue Type: Task
>          Components: fairscheduler
>    Affects Versions: 2.7.0
>            Reporter: Wilfred Spiegelenburg
>            Assignee: Wilfred Spiegelenburg
>            Priority: Major
>
> Remove deprecated FairScheduler continuous scheduler code



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