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From "Gopal V (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-10681) Remove synchronized blocks from SnappyCodec and ZlibCodec buffering
Date Thu, 12 Jun 2014 07:12:04 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-10681?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Gopal V updated HADOOP-10681:
-----------------------------

    Attachment: snappy-perf-unsync.png

With sed -i ~ "s/synchronized //" snappy/*.java, the cpu fractions look more sane

!snappy-perf-unsync.png!

> Remove synchronized blocks from SnappyCodec and ZlibCodec buffering
> -------------------------------------------------------------------
>
>                 Key: HADOOP-10681
>                 URL: https://issues.apache.org/jira/browse/HADOOP-10681
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: performance
>    Affects Versions: 2.2.0, 2.4.0, 2.5.0
>            Reporter: Gopal V
>            Assignee: Gopal V
>              Labels: perfomance
>         Attachments: compress-cmpxchg-small.png, perf-top-spill-merge.png, snappy-perf-unsync.png
>
>
> The current implementation of SnappyCompressor spends more time within the java loop
of copying from the user buffer into the direct buffer allocated to the compressor impl, than
the time it takes to compress the buffers.
> !perf-top-spill-merge.png!
> The bottleneck was found to be java monitor code inside SnappyCompressor.
> The methods are neatly inlined by the JIT into the parent caller (BlockCompressorStream::write),
which unfortunately does not flatten out the synchronized blocks.
> !compress-cmpxchg-small.png!
> The loop does a write of small byte[] buffers (each IFile key+value). 
> I counted approximately 6 monitor enter/exit blocks per k-v pair written.



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