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From "Vijay (Updated) (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-3623) use MMapedBuffer in CompressedSegmentedFile.getSegment
Date Tue, 27 Dec 2011 03:06:32 GMT


Vijay updated CASSANDRA-3623:

    Attachment: CRC+MMapIO.xlsx

Alright i think i found the the missing peace:
1) Plz reapply v2 from CASSANDRA-3611 (which also depends on CASSANDRA-3610)
2) Plz reapply v3 which has the mark() (this seem to be used by range slice and Stress tool
does it).

The Test Results are attached, let me know in case of any questions... the performance seem
to be better.

I Used stress test so we are in the same page, and when the Column size or the range of columns
to be fetched increases the performance gets better (rebuffers)
> use MMapedBuffer in CompressedSegmentedFile.getSegment
> ------------------------------------------------------
>                 Key: CASSANDRA-3623
>                 URL:
>             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-v3.patch,
0001-MMaped-Compression-segmented-file.patch, 0002-tests-for-MMaped-Compression-segmented-file-v2.patch,
0002-tests-for-MMaped-Compression-segmented-file-v3.patch, CRC+MMapIO.xlsx, MMappedIO-Performance.docx
> 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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