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From "Vinod Kumar Vavilapalli (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-2349) speed up list[located]status calls from input formats
Date Thu, 20 Mar 2014 02:09:45 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2349?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13941313#comment-13941313
] 

Vinod Kumar Vavilapalli commented on MAPREDUCE-2349:
----------------------------------------------------

Okay, the latest patch looks good. Will check it in when Jenkins says okay..

> speed up list[located]status calls from input formats
> -----------------------------------------------------
>
>                 Key: MAPREDUCE-2349
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2349
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: task
>            Reporter: Joydeep Sen Sarma
>            Assignee: Siddharth Seth
>         Attachments: MAPREDUCE-2349.1.wip.txt, MAPREDUCE-2349.2.txt, MAPREDUCE-2349.3.txt,
MAPREDUCE-2349.4.txt, MAPREDUCE-2349.5.txt
>
>
> when a job has many input paths - listStatus - or the improved listLocatedStatus - calls
(invoked from the getSplits() method) can take a long time. Most of the time is spent waiting
for the previous call to complete and then dispatching the next call. 
> This can be greatly speeded up by dispatching multiple calls at once (via executors).
If the same filesystem client is used - then the calls are much better pipelined (since calls
are serialized) and don't impose extra burden on the namenode while at the same time greatly
reducing the latency to the client. In a simple test on non-peak hours, this resulted in the
getSplits() time reducing from about 3s to about 0.5s.



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