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Date: Thu, 4 Dec 2008 09:14:44 -0800 (PST)
From: "Runping Qi (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-4766) Hadoop performance degrades
 significantly as more and more jobs complete
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    [ https://issues.apache.org/jira/browse/HADOOP-4766?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12653365#action_12653365 ] 

Runping Qi commented on HADOOP-4766:
------------------------------------


This is my first time to set 500 jobs in memory. I set that because
I intended to compare the behaviors of the two gridmix2 runs.

If the number of tasks kept in memory is critical for the performance of JobTracker (and thus to the whole cluster), then we should set limit on that, instead of the
number of jobs, because the numbers of tasks of jobs can vary a lot. 
Also, we need to understand how the number of tasks kept in memory impacts the performance.


> Hadoop performance degrades significantly as more and more jobs complete
> ------------------------------------------------------------------------
>
>                 Key: HADOOP-4766
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4766
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.18.2, 0.19.0
>            Reporter: Runping Qi
>            Priority: Blocker
>             Fix For: 0.18.3, 0.19.1, 0.20.0
>
>
> When I ran the gridmix 2 benchmark load on a fresh cluster of 500 nodes with hadoop trunk, 
> the gridmix load, consisting of 202 map/reduce jobs of various sizes, completed in 32 minutes. 
> Then I ran the same set of the jobs on the same cluster, yhey completed in 43 minutes.
> When I ran them the third times, it took (almost) forever --- the job tracker became non-responsive.
> The job  tracker's heap size was set to 2GB. 
> The cluster is configured to keep up to 500 jobs in memory.
> The job tracker kept one cpu busy all the time. Look like it was due to GC.
> I believe the release 0.18/0.19 have the similar behavior.
> I believe 0.18 and 0.18 also have the similar behavior.

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