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From "Amar Kamat (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1683) Remove JNI calls from ClusterStatus cstr
Date Fri, 21 May 2010 06:29:19 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12869892#action_12869892
] 

Amar Kamat commented on MAPREDUCE-1683:
---------------------------------------

One suggestion : Instead of printing the total memory, which will remain fixed/clamped, shouldn't
we print the currently used heap memory i.e Runtime.totalMemory() - Runtime.freeMemory()?

> Remove JNI calls from ClusterStatus cstr
> ----------------------------------------
>
>                 Key: MAPREDUCE-1683
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1683
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: jobtracker
>    Affects Versions: 0.20.2
>            Reporter: Chris Douglas
>            Assignee: Luke Lu
>             Fix For: 0.21.0, 0.22.0
>
>         Attachments: MAPREDUCE-1683_part2_yhadoop_20_10.patch, MAPREDUCE-1683_yhadoop_20_9.patch,
MAPREDUCE-1683_yhadoop_20_S.patch, mr-1683-trunk-v1.patch
>
>
> The {{ClusterStatus}} constructor makes two JNI calls to the {{Runtime}} to fetch memory
information. {{ClusterStatus}} instances are often created inside the {{JobTracker}} to obtain
other, unrelated metrics (sometimes from schedulers' inner loops). Given that this information
is related to the {{JobTracker}} process and not the cluster, the metrics are also available
via {{JvmMetrics}}, and the jsps can gather this information for themselves: these fields
can be removed from {{ClusterStatus}}

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