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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8714) row-cache: use preloaded jemalloc w/ Unsafe
Date Wed, 04 Mar 2015 19:41:38 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8714?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14347435#comment-14347435
] 

Ariel Weisberg commented on CASSANDRA-8714:
-------------------------------------------

Looking at the micro benchmark it isn't measuring the right thing. The same call site has
to potentially contain direct and non-direct buffers. The JVM also does JVM wide class hierarchy
analysis, but I don't know what it does for call site specific analysis. There are actually
several potential direct and non-direct byte buffer classes. Take a look at the type hierarchy
for ByteBuffer it's pretty long.

This would only be a factor for very small copies Say 4-16 bytes or similar. Say when serializing
variable length fields that can be very small. You would end up calling this which is basically
a memcpy equivalent, and that is where the overhead of starting the memcpy matters.

> row-cache: use preloaded jemalloc w/ Unsafe
> -------------------------------------------
>
>                 Key: CASSANDRA-8714
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8714
>             Project: Cassandra
>          Issue Type: Sub-task
>            Reporter: Robert Stupp
>            Assignee: Robert Stupp
>             Fix For: 3.0
>
>         Attachments: 8714-2.txt, 8714-3.txt, 8714-4.txt, 8714.txt
>
>
> Using jemalloc via Java's {{Unsafe}} is a better alternative on Linux than using jemalloc
via JNA.



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