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From "Gopal V (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-10681) Remove synchronized blocks from SnappyCodec and ZlibCodec buffering inner loop
Date Sat, 12 Jul 2014 21:33:05 GMT

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

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

    Attachment: HADOOP-10681.4.patch

Go back to the initial approach of unsynchronized streams, but retain the multi-threaded test-case.

The JNI locks remain in-place.

> Remove synchronized blocks from SnappyCodec and ZlibCodec buffering inner loop
> ------------------------------------------------------------------------------
>
>                 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: HADOOP-10681.1.patch, HADOOP-10681.2.patch, HADOOP-10681.3.patch,
HADOOP-10681.4.patch, 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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