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From "Daniel Templeton (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3091) [Umbrella] Improve and fix locks of RM scheduler
Date Tue, 07 Nov 2017 23:32:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-3091?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16243089#comment-16243089
] 

Daniel Templeton commented on YARN-3091:
----------------------------------------

I've been doing some performance testing lately as part of the resource types (YARN-3926)
work, and I'm not sure the idea of using read/write locks to *improve* performance is sound.
 See: https://stackoverflow.com/questions/34611106/synchronized-vs-readwritelock-performance
 Read/write locks are slower in scenarios where there isn't a significant amount of contention,
which we don't have.  My testing shows that by replacing the read/write locks with a simple
reentrant lock, I can get a notable performance boost.  I'm looking at reverting the read/write
lock changes within the fair scheduler at least.  Thoughts?

> [Umbrella] Improve and fix locks of RM scheduler
> ------------------------------------------------
>
>                 Key: YARN-3091
>                 URL: https://issues.apache.org/jira/browse/YARN-3091
>             Project: Hadoop YARN
>          Issue Type: Task
>          Components: capacityscheduler, fairscheduler, resourcemanager, scheduler
>            Reporter: Wangda Tan
>
> In existing YARN RM scheduler, there're some issues of using locks. For example:
> - Many unnecessary synchronized locks, we have seen several cases recently that too frequent
access of scheduler makes scheduler hang. Which could be addressed by using read/write lock.
Components include scheduler, CS queues, apps
> - Some fields not properly locked (Like clusterResource)
> We can address them together in this ticket.
> (More details see comments below)



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