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From "ChenFolin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-5188) FairScheduler performance bug
Date Wed, 01 Jun 2016 06:26:13 GMT

    [ https://issues.apache.org/jira/browse/YARN-5188?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15309375#comment-15309375
] 

ChenFolin commented on YARN-5188:
---------------------------------

Thanks Xianyin Xin,

TreeSet oparate time complexity here is : O(log1) + O(log2) + ... + O(log(app num)), and binary
search O(log(app num)).

point 2 is the same with YARN-4090.

And can you tell me your phone number or wechat or qq ? Send a mail to chenfolin@gmail.com


> FairScheduler performance bug
> -----------------------------
>
>                 Key: YARN-5188
>                 URL: https://issues.apache.org/jira/browse/YARN-5188
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: fairscheduler
>    Affects Versions: 2.5.0, 2.8.0
>            Reporter: ChenFolin
>         Attachments: YARN-5188.patch
>
>
>  My Hadoop Cluster has recently encountered a performance problem. Details as Follows.
> There are two point which can cause this performance issue.
> 1: application sort before assign container at FSLeafQueue. TreeSet is not the best,
Why not keep orderly ? and then we can use binary search to help keep orderly when a application's
resource usage has changed.
> 2: queue sort and assignContainerPreCheck will lead to compute all leafqueue resource
usage ,Why can we store the leafqueue usage at memory and update it when assign container
op release container happen?
>        
>        The efficiency of assign container in the Resourcemanager may fall when the number
of running and pending application grows. And the fact is the cluster has too many PendingMB
or PengdingVcore , and the Cluster 
> current utilization rate may below 20%.
>        I checked the resourcemanager logs, I found that every assign container may cost
5 ~ 10 ms, but just 0 ~ 1 ms at usual time.
>      
>        I use TestFairScheduler to reproduce the scene:
>  
>        Just one queue: root.defalut
>      10240 apps.
>  
>        assign container avg time:  6753.9 us ( 6.7539 ms)  
>      apps sort time (FSLeafQueue : Collections.sort(runnableApps, comparator); ): 4657.01
us ( 4.657 ms )
>      compute LeafQueue Resource usage : 905.171 us ( 0.905171 ms )
>      
>      When just root.default, one assign container op contains : ( one apps sort op )
+ 2 * ( compute leafqueue usage op )
>        According to the above situation, I think the assign container op has a performance
problem  . 



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