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From "Luke Lu (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-3612) Task.TaskReporter.done method blocked for some time when task is finishing
Date Sat, 07 Apr 2012 00:19:18 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-3612?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13249084#comment-13249084
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Luke Lu commented on MAPREDUCE-3612:
------------------------------------

See MAPREDUCE-2450 for why this is needed. We saw a fairly significant performance regression
(vs. 0.20.2) in Hadoop 1.x for some small jobs workloads due to this issue as well.

Regarding the patch, I don't think it address the issue in MAPREDUCE-2450. Will post a patch
later.
                
> Task.TaskReporter.done method blocked for some time when task is finishing
> --------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-3612
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3612
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: Binglin Chang
>            Assignee: Binglin Chang
>         Attachments: MAPREDUCE-3612.patch
>
>
> We recently have done some tests to evaluate performances of different Hadoop versions(1.0,
0.23, Baidu internal version), and found some weird results. One of them is in 1.0 Task.TaskReporter.done()
takes too much time, about 2s, this is bad for small tasks. After reviewing source code and
add some log, the following code block Task.TaskReporter.done
> {code:title=src/mapred/org/apache/hadoop/mapred/Task.java}
>  658           try {
>  659             Thread.sleep(PROGRESS_INTERVAL);
>  660           }
>  723     public void stopCommunicationThread() throws InterruptedException {
>  724       // Updating resources specified in ResourceCalculatorPlugin
>  725       if (pingThread != null) {
>  726         synchronized(lock) {
>  727           while(!done) {
>  728             lock.wait();
>  729           }
>  730         }
>  731         pingThread.interrupt();
>  732         pingThread.join();
>  733       }
>  734     }
> {code}
> Originally line 724-730 don't exists, I don't know why it is added. If it is needed,
we can replace Thread.sleep with Object.wait(timeout) and Object.notify instead, so it won't
block.

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