[jira] [Updated] (CASSANDRA-4937) CRAR improvements (object cache + CompressionMetadata chunk offset storage moved off-heap).

["Pavel Yaskevich (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-4937?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Pavel Yaskevich updated CASSANDRA-4937:
---------------------------------------

    Attachment: CASSANDRA-4937.patch
    
> CRAR improvements (object cache + CompressionMetadata chunk offset storage moved off-heap).
> -------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-4937
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4937
>             Project: Cassandra
>          Issue Type: Bug
>    Affects Versions: 1.1.6
>            Reporter: Pavel Yaskevich
>            Assignee: Pavel Yaskevich
>             Fix For: 1.1.7
>
>         Attachments: CASSANDRA-4937.patch
>
>
> After good amount of testing on one of the clusters it was found that in order to improve read latency we need to minimize allocation rate that compression involves, that minimizes GC (as well as heap usage) and substantially decreases latency on read heavy workloads. 
> I have also discovered that RAR skip cache harms performance in situation when reads are done in parallel with compaction working with relatively big SSTable files (few GB and more). The attached patch removes possibility to skip cache from compressed files (I can also add changes to RAR to remove skip cache functionality as a separate patch). 

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