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Date: Wed, 15 Sep 2010 11:18:35 -0400 (EDT)
From: "Hudson (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Subject: [jira] Commented: (CASSANDRA-1469) adaptive default heap size
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    [ https://issues.apache.org/jira/browse/CASSANDRA-1469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12909765#action_12909765 ] 

Hudson commented on CASSANDRA-1469:
-----------------------------------

Integrated in Cassandra #536 (See [https://hudson.apache.org/hudson/job/Cassandra/536/])
    Adaptively set the heap size and memtable thresholds at runtime.  Patch by brandonwilliams, reviewed by jbellis for CASSANDRA-1469


> adaptive default heap size
> --------------------------
>
>                 Key: CASSANDRA-1469
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1469
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Packaging
>            Reporter: Jonathan Ellis
>            Assignee: Brandon Williams
>             Fix For: 0.7.0
>
>         Attachments: 0001_adaptively_determine_heap_size.txt, 0002_determine_memtable_thresholds_at_runtime.txt
>
>
> Cassandra comes out of the box with very conservative defaults, especially in -Xmx and memtable sizes, which leads to complaints of poor performance or even OOM conditions under heavy load.  But changing these to be aggressive can cause the same problem: most servers enable swap out of the box, so asking for a 4GB or 8GB heap could allocate happily but also cause problems when it starts paging.
> Proposed solution is to update the start script to set Xmx to half of system ram ("free -m | awk '/Mem:/ {print $2}'").  Memtable defaults will have to be handled by Java, but we can do that based on heap size (Runtime.maxMemory).
> An alternative suggestion was to provide "small", "medium", "large" configurations, but this plays poorly with rpm and deb packages.  I think the adaptive approach is more promising.

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