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Posted to mapreduce-issues@hadoop.apache.org by "jaehoon ko (JIRA)" <ji...@apache.org> on 2014/06/27 03:16:25 UTC

[jira] [Updated] (MAPREDUCE-5946) Last spill of map task is not necessary for final merge

     [ https://issues.apache.org/jira/browse/MAPREDUCE-5946?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

jaehoon ko updated MAPREDUCE-5946:
----------------------------------

    Component/s:     (was: security)
                 task
    Description: 
In map task, merge starts only after the last spill is completely written to disk. This is not necessary nor efficient because the last spill should to be reloaded soon for merge, probably immediately because spills are merged in the order of their sizes and the last spill is likely smallest. OS page cache is not the answer due to its opportunistic nature.

I'm starting to work on this. Please give me your thoughts.

  was:
In map task, merge starts only after the last spill is completely written to disk. This is not necessary nor efficient because the last spill should to be reloaded soon for merge, probably immediately because spills are merged in the order of their sizes and the last spill is likely smallest. OS page cache is not the answer due to its opportunistic nature.

I'm starting to work on it. Please give me your thoughts.


> Last spill of map task is not necessary for final merge
> -------------------------------------------------------
>
>                 Key: MAPREDUCE-5946
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5946
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: performance, task
>    Affects Versions: 2.4.0
>            Reporter: jaehoon ko
>            Assignee: jaehoon ko
>              Labels: newbie, performance
>
> In map task, merge starts only after the last spill is completely written to disk. This is not necessary nor efficient because the last spill should to be reloaded soon for merge, probably immediately because spills are merged in the order of their sizes and the last spill is likely smallest. OS page cache is not the answer due to its opportunistic nature.
> I'm starting to work on this. Please give me your thoughts.



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