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From "Jonathan Ellis (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-3618) OpenBitSet can allocate more bytes than it needs
Date Tue, 13 Dec 2011 16:39:30 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-3618?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jonathan Ellis updated CASSANDRA-3618:
--------------------------------------

             Reviewer: jbellis
    Affects Version/s:     (was: 1.0.0)
                       1.0.1

Committed.

(This affects 1.0.1+, introduced by CASSANDRA-2466.)
                
> OpenBitSet can allocate more bytes than it needs
> ------------------------------------------------
>
>                 Key: CASSANDRA-3618
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3618
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.0.1
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>             Fix For: 1.0.7
>
>         Attachments: 0001-Fix-openBitSet.patch
>
>
> CASSANDRA-2466 changed OpenBitSet to break big long arrays into pages. However, it always
allocate full pages, each page being of size 4096 * 8 bytes. This means that we almost always
allocate too much bytes, and for a row that has 1 column, the associated row bloom filter
allocates 32760 more bytes than it should.
> This has a significant impact on performance. In a small test using the SSTableSimpleUnsortedWriter
to generate rows with 1 column, 0.8 is about twice as fast as 1.0 because of that (the difference
shrink when there is more columns obviously).

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