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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-1755) BatchWriter blocks all addMutation calls while binning mutations
Date Wed, 02 Mar 2016 14:01:18 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15175625#comment-15175625
] 

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

Github user dlmarion commented on the pull request:

    https://github.com/apache/accumulo/pull/75#issuecomment-191248202
  
    So, I took a different approach. I believe that I resolved the race conditions by synchronizing
on the objects being updated. This would still cause the performance penalty that you are
talking about going to main memory. However, the stats objects being updated are only used
if trace logging is enabled, so I guarded the two methods that update the stats with trace
logging checks. Therefore, you will only pay a performance penalty if trace logging is enabled,
but by turning on trace logging you should expect a little bit of a performance hit anyway.


> 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: 1h 20m
>  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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