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https://issues.apache.org/jira/browse/YARN-6407?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15947594#comment-15947594
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Yufei Gu commented on YARN-6407:
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Hi [~zhengchenyu], thanks for filing this jira. IIUC, you reduced frequency of
NM node update to avoid flooding the network in a 5k nodes cluster, but
Continuous Scheduling is not necessary when there are still enough node update
events in the clusters. Besides the improvement of lock in FS, we can always
balance time interval of continuous scheduling and frequency of NM node update
to get better scheduling latency.
> Improve and fix locks of RM scheduler
> -------------------------------------
>
> Key: YARN-6407
> URL: https://issues.apache.org/jira/browse/YARN-6407
> Project: Hadoop YARN
> Issue Type: Bug
> Components: fairscheduler
> Affects Versions: 2.7.1
> Environment: CentOS 7, 1 Gigabit Ethernet
> Reporter: zhengchenyu
> Fix For: 2.7.1
>
> Original Estimate: 2m
> Remaining Estimate: 2m
>
> First，this issue dose not duplicate the YARN-3091.
> In our cluster, we have 5k nodes, and the server is configured with 1 Gigabit
> Ethernet. So network is bottleneck in our cluster.
> We must distcp data from warehouse, because of 1 Gigabit Ethernet, we must
> set yarn.scheduler.fair.max.assign to 5, or must lead to hotspot.
> The setting that max.assign is 5 lead to the assigned ability decreased. So
> we start the ContinuousSchedulingThread.
> As more applicaitons running in our cluster , and with
> ContinuousSchedulingThread, the problem of lock contention is more serious.
> In our cluster, the callqueue of ApplicationMasterSeriver's rpc is high
> occasionally. we worried that more problem occure in future with more
> application are running.
> Here is our logical graph:
> "1 Gigabit Ethernet" and "data hot spot" ==> "set
> yarn.scheduler.fair.max.assign to 5" ==> "ContinuousSchedulingThread is
> started" and "more applcations" => "lock contention"
> I know YARN-3091 solved this problem, but the patch aims that change the
> object lock to read write lock. This change is still Coarse-Grained. So I
> think we lock the resources or not lock the large section code.
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