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Date: Sat, 27 Feb 2016 00:42:18 +0000 (UTC)
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Subject: [jira] [Commented] (ACCUMULO-1755) BatchWriter blocks all
 addMutation calls while binning mutations
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    [ https://issues.apache.org/jira/browse/ACCUMULO-1755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15170204#comment-15170204 ] 

ASF GitHub Bot commented on ACCUMULO-1755:
------------------------------------------

Github user keith-turner commented on the pull request:

    https://github.com/apache/accumulo/pull/75#issuecomment-189540148
  
    > Leaving at 10 (or some other number) provides back pressure to the client threads adding mutations. 
    
    I beilieve doing this makes it harder to understand the batch writer from a user perspective.   This batch writer already provides back pressure based on memory usage.  This constraint would provide back pressure in another way that I would not want to attempt to write up in user facing javadocs.


> BatchWriter blocks all addMutation calls while binning mutations
> ----------------------------------------------------------------
>
>                 Key: ACCUMULO-1755
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-1755
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: client
>            Reporter: Adam Fuchs
>            Assignee: Dave Marion
>             Fix For: 1.8.0
>
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> Through code inspection, we found that the BatchWriter bins mutations inside of a synchronized block that covers calls to addMutation. Binning potentially involves lookups of tablet metadata and processes a fair amount of information. We will get better parallelism if we can either unlock the lock while binning, dedicate another thread to do the binning, or use one of the send threads to do the binning.
> This has not been verified empirically yet, so there is not yet any profiling info to indicate the level of improvement that we should expect. Profiling and repeatable demonstration of this performance bottleneck should be the first step on this ticket.


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