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From "GAO Rui (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9494) Parallel optimization of DFSStripedOutputStream#flushAllInternals( )
Date Tue, 22 Dec 2015 01:02:46 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15067363#comment-15067363
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GAO Rui commented on HDFS-9494:
-------------------------------

Thanks Nicholas. I have considered {{checkStreamers()}} issue before too. Cause in {{checkStreamers()}},
we just read {{streamers}} and {{failedStreamers}}, no operation to change them. So, even
different thread call {{checkStreamers()}}, there may not have a conflict I think. For race
condition, could you share more details?

> Parallel optimization of DFSStripedOutputStream#flushAllInternals( )
> --------------------------------------------------------------------
>
>                 Key: HDFS-9494
>                 URL: https://issues.apache.org/jira/browse/HDFS-9494
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: GAO Rui
>            Assignee: GAO Rui
>            Priority: Minor
>         Attachments: HDFS-9494-origin-trunk.00.patch, HDFS-9494-origin-trunk.01.patch,
HDFS-9494-origin-trunk.02.patch, HDFS-9494-origin-trunk.03.patch
>
>
> Currently, in DFSStripedOutputStream#flushAllInternals( ), we trigger and 
> wait for flushInternal( ) in sequence. So the runtime flow is like:
> {code}
> Streamer0#flushInternal( )
> Streamer0#waitForAckedSeqno( )
> Streamer1#flushInternal( )
> Streamer1#waitForAckedSeqno( )
> …
> Streamer8#flushInternal( )
> Streamer8#waitForAckedSeqno( )
> {code}
> It could be better to trigger all the streamers to flushInternal( ) and
> wait for all of them to return from waitForAckedSeqno( ),  and then flushAllInternals(
) returns.



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