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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8614) Select optimal CRC32 implementation at runtime
Date Mon, 09 Feb 2015 19:04:35 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14312650#comment-14312650
] 

Benedict commented on CASSANDRA-8614:
-------------------------------------

+1 with one nit: we tend (rightly or wrongly) to avoid the use of "final" as a local variable
modifier except where necessary

i'll commit it with a raft of other upcoming commits I'll need to merge, probably post 2.1.3
to simplify that release process

> Select optimal CRC32 implementation at runtime
> ----------------------------------------------
>
>                 Key: CASSANDRA-8614
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8614
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Ariel Weisberg
>            Assignee: Ariel Weisberg
>              Labels: performance
>         Attachments: 8614.patch, Sample.java
>
>
> JDK 8 has support for an intrinsic for CRC32 that runs at 12-13 gigabytes/sec per core
in my quick and dirty test. PureJavaCRC32 is < 800 megabytes/sec if I recall and it has
a lookup table that evicts random cache lines every time it runs.
> In order to capture the benefit of that when it is available we can select a CRC32 implementation
at startup in a static block.
> If JDK 8 is not what is running we can fall back to the existing PureJavaCRC32 implementation.



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