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https://issues.apache.org/jira/browse/ACCUMULO-1755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15180139#comment-15180139
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Dave Marion commented on ACCUMULO-1755:
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[~afuchs] [~kturner] FWIW, I have been doing some testing locally. I have not
been able to show any real performance improvement. Running an application with
this patch still shows multiple client threads blocking on
TabletServerBatchWriter.addMutation() because of the synchronization on that
method. All this patch did was make 1 of the client threads execute that method
faster. I think the real performance improvement will be removing the
synchronization modifier from the addMutation method.
> 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: 1.6.6, 1.7.2, 1.8.0
>
> Attachments: ACCUMULO-1755.patch
>
> Time Spent: 2h
> 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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