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https://issues.apache.org/jira/browse/HADOOP-4018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12634113#action_12634113
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Amar Kamat commented on HADOOP-4018:
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Few comments :
_Main :_
1. There is no need to do the cleanup in init tasks. Simply throwing an
exception in init tasks should do the cleanup and kill/fail the job. There
seems to be a bug in the framework and I have opened HADOOP-4261 to address it.
2. mapred.max.tasks.per.job should be set at the jobtracker level and not at
the job level. It should be something like an expert-final parameter
_Testcase :_
1. Remove the commented assert statement
2. Most of the imports are not needed.
3. Rewrite the test to reflect the changes
> limit memory usage in jobtracker
> --------------------------------
>
> Key: HADOOP-4018
> URL: https://issues.apache.org/jira/browse/HADOOP-4018
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Attachments: maxSplits.patch, maxSplits2.patch, maxSplits3.patch,
> maxSplits4.patch, maxSplits5.patch, maxSplits6.patch, maxSplits7.patch,
> maxSplits8.patch
>
>
> We have seen instances when a user submitted a job with many thousands of
> mappers. The JobTracker was running with 3GB heap, but it was still not
> enough to prevent memory trashing from Garbage collection; effectively the
> Job Tracker was not able to serve jobs and had to be restarted.
> One simple proposal would be to limit the maximum number of tasks per job.
> This can be a configurable parameter. Is there other things that eat huge
> globs of memory in job Tracker?
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