[jira] [Resolved] (CASSANDRA-3432) Avoid large array allocation for compressed chunk offsets

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

     [ https://issues.apache.org/jira/browse/CASSANDRA-3432?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Pavel Yaskevich resolved CASSANDRA-3432.
----------------------------------------

    Resolution: Fixed

Committed.
                
> Avoid large array allocation for compressed chunk offsets
> ---------------------------------------------------------
>
>                 Key: CASSANDRA-3432
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3432
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.0.0
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>            Priority: Minor
>              Labels: compression
>             Fix For: 1.0.2
>
>         Attachments: 0001-Break-down-large-long-array.patch
>
>
> For each compressed file we keep the chunk offsets in memory (a long[]). The size of this array is directly proportional to the sstable file and the chunk_length_kb used, but say for a 64GB sstable, we're talking ~8MB in memory by default.
> Without being absolutely huge, this probably makes the life of the GC harder than necessary for the same reasons than CASSANDRA-2466, and this ticket proposes the same solution, i.e. to break down those big array into smaller ones to ease fragmentation.
> Note that this is only a concern for size tiered compaction. But until leveled compaction is battle tested, the default and we know nobody uses size tiered anymore, it's probably worth making the optimization.

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