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From "Vijay (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-3610) Checksum improvement for CompressedRandomAccessReader
Date Thu, 22 Dec 2011 19:57:31 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-3610?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13175014#comment-13175014
] 

Vijay commented on CASSANDRA-3610:
----------------------------------

Fields: 
1 -> bytes sent to checksum
2 -> Mb/s (trials * size / 1024.0 / 1024.0) by pure java implementation
3 -> Mb/s by Native CRC

5 -> Pure Jave  Random bytes from and till
6 -> Pure Java Mb/S
8 -> Native Random bytes from and till
9 -> Native Java Mb/S

Hope that makes sense... i should have separated the two tests random and constant byte test.
                
> Checksum improvement for CompressedRandomAccessReader
> -----------------------------------------------------
>
>                 Key: CASSANDRA-3610
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3610
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.1
>         Environment: JVM
>            Reporter: Vijay
>            Assignee: Vijay
>            Priority: Minor
>             Fix For: 1.1
>
>         Attachments: 0001-use-pure-java-CRC32-v2.patch, 0001-use-pure-java-CRC32.patch
>
>
> When compression is on, Currently we see checksum taking up about 40% of the CPU more
than snappy library.
> Looks like hadoop solved it by implementing their own checksum, we can either use it
or implement something like that.
> http://images.slidesharecdn.com/1toddlipconyanpeichen-cloudera-hadoopandperformance-final-111110132228-phpapp01-slide-15-768.jpg?1321043717
> in our test env it provided 50% improvement over native implementation which uses jni
to call the OS.

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