[
https://issues.apache.org/jira/browse/YARN-4002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15217334#comment-15217334
]
Hong Zhiguo commented on YARN-4002:
-----------------------------------
Including return statement into readlock critical seciton doesn't make
difference except longer critical section and worse performance.
Since hostsList and excludeList of hostReader is updated by reference
assignment, no race condition would exist even the lookup is not protected by
readlock.
> make ResourceTrackerService.nodeHeartbeat more concurrent
> ---------------------------------------------------------
>
> Key: YARN-4002
> URL: https://issues.apache.org/jira/browse/YARN-4002
> Project: Hadoop YARN
> Issue Type: Improvement
> Reporter: Hong Zhiguo
> Assignee: Hong Zhiguo
> Priority: Critical
> Attachments: 0001-YARN-4002.patch, YARN-4002-lockless-read.patch,
> YARN-4002-rwlock-v2.patch, YARN-4002-rwlock.patch, YARN-4002-v0.patch
>
>
> We have multiple RPC threads to handle NodeHeartbeatRequest from NMs. By
> design the method ResourceTrackerService.nodeHeartbeat should be concurrent
> enough to scale for large clusters.
> But we have a "BIG" lock in NodesListManager.isValidNode which I think it's
> unnecessary.
> First, the fields "includes" and "excludes" of HostsFileReader are only
> updated on "refresh nodes". All RPC threads handling node heartbeats are
> only readers. So RWLock could be used to alow concurrent access by RPC
> threads.
> Second, since he fields "includes" and "excludes" of HostsFileReader are
> always updated by "reference assignment", which is atomic in Java, the reader
> side lock could just be skipped.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
