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From "Vijay (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-3623) use MMapedBuffer in CompressedSegmentedFile.getSegment
Date Fri, 23 Dec 2011 22:14:30 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-3623?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vijay updated CASSANDRA-3623:
-----------------------------

    Attachment: 0002-tests-for-MMaped-Compression-segmented-file-v2.patch
                0001-MMaped-Compression-segmented-file-v2.patch

Attached patch has optimization on memcpy which the earlier one didnt.

Performance:
Current trunk: 400+ms Avg
Removing CRC (CASSANDRA-3611): 200+ms Avg
With this patch: 100+ms Avg


                
> use MMapedBuffer in CompressedSegmentedFile.getSegment
> ------------------------------------------------------
>
>                 Key: CASSANDRA-3623
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3623
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.1
>            Reporter: Vijay
>            Assignee: Vijay
>              Labels: compression
>             Fix For: 1.1
>
>         Attachments: 0001-MMaped-Compression-segmented-file-v2.patch, 0001-MMaped-Compression-segmented-file.patch,
0002-tests-for-MMaped-Compression-segmented-file-v2.patch
>
>
> CompressedSegmentedFile.getSegment seem to open a new file and doesnt seem to use the
MMap and hence a higher CPU on the nodes and higher latencies on reads. 
> This ticket is to implement the TODO mentioned in CompressedRandomAccessReader
> // TODO refactor this to separate concept of "buffer to avoid lots of read() syscalls"
and "compression buffer"
> but i think a separate class for the Buffer will be better.

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