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https://issues.apache.org/jira/browse/MAPREDUCE-3402?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13163206#comment-13163206
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Siddharth Seth commented on MAPREDUCE-3402:
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Possibly different from Vinod's leads. With some changes to the environment -
and maybe a result of a few more commits, the job does complete.
Couple of observations:
- The first tens of thousands of maps finish pretty fast.
- GC kicks in midway through the job and can't reclaim much. Spends several
cycles where nothing is reclaimed before managing to reclaim a small amount.
- Counters are taking up a good amount of heap.
- JobHistory writes cannot keep up.
- Bumping up the AM heapsize does help.
Doesn't explain why the performance was better pre Oct 19 though. Opening and
linking 2 jiras (non blockers since increasing the heap works well) for
possible changes to counters and JobHistory.
> AMScalability test of Sleep job with 100K 1-sec maps regressed into running
> very slowly
> ---------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-3402
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-3402
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: applicationmaster, mrv2
> Affects Versions: 0.23.0
> Reporter: Vinod Kumar Vavilapalli
> Assignee: Vinod Kumar Vavilapalli
> Priority: Blocker
> Fix For: 0.23.1
>
>
> The world was rosier before October 19-25, [~karams] says.
> The 100K 1 second sleep job used to take around 800mins or 13-14 mins. It now
> runs till 45 mins and still manages to complete only about 45K tasks.
> One/more of the flurry of commits for 0.23.0 deserve(s) the blame.
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