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https://issues.apache.org/jira/browse/MAPREDUCE-2124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12919943#action_12919943
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Scott Chen commented on MAPREDUCE-2124:
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bq. Will it? The shuffle phase can be delayed by the map scheduling, the sort
phase is often a noop, and the reduce phase takes whatever time it requires.
I agree with you. But we will have more information about how much time
actually spent on reduce and how much time spent by the framework (map schedule
delay and the merge sorting).
> Add job counters for measuring time spent in three different phases in
> reducers
> -------------------------------------------------------------------------------
>
> Key: MAPREDUCE-2124
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2124
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: jobtracker
> Affects Versions: 0.22.0
> Reporter: Scott Chen
> Assignee: Scott Chen
> Priority: Minor
> Fix For: 0.22.0
>
>
> We currently have SLOTS_MILLIS_REDUCES which measures the total slot time of
> reducer.
> It will be useful if we have
> {code}
> SLOTS_MILLIS_REDUCES_COPY
> SLOTS_MILLIS_REDUCES_SORT
> SLOTS_MILLIS_REDUCES_REDUCE
> {code}
> which measures three different phases of a reducer.
> This will help us identify the bottleneck of the reducers.
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