[jira] [Commented] (CASSANDRA-3623) use MMapedBuffer in CompressedSegmentedFile.getSegment

["Vijay (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-3623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13173365#comment-13173365 ] 

Vijay commented on CASSANDRA-3623:
----------------------------------

This gets complicated because the rows boundary is not the chunk boundary, I tried to map more blocks than needed for a given boundary but there is a possibility of running out of memory, hence i am planning to do the following:

Make boundaries for the chunk instead of the row position
Chunks between the boundaries will over-lap.
                
> 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
>             Fix For: 1.1
>
>
> 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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