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From "stack (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-4714) Don't ship w/ icms enabled by default
Date Tue, 01 Nov 2011 16:11:32 GMT

     [ https://issues.apache.org/jira/browse/HBASE-4714?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

stack updated HBASE-4714:

    Attachment: icms.txt

Disable icms and add a bit of doc that newer jvms are a bit better around avoiding fragmentation.
> Don't ship w/ icms enabled by default
> -------------------------------------
>                 Key: HBASE-4714
>                 URL: https://issues.apache.org/jira/browse/HBASE-4714
>             Project: HBase
>          Issue Type: Task
>            Reporter: stack
>             Fix For: 0.92.0
>         Attachments: icms-v2.txt, icms.txt
> "Incremental CMS (iCMS) was written for a specific use case - 1 or 2 hardware
> threads where concurrent activity by CMS would look like a STW (if
> only 1 hardware thread) or a high tax on the cpu cycles (2 hardware
> threads).   It has a higher overhead and also is less efficient in terms
> of identifying garbage.  The latter is because iCMS spreads out the
> concurrent work so that objects that it has identified as live earlier
> may actually be dead when the dead objects are swept up.  It's
> worth testing with regular CMS instead of iCMS."
> From recent hotspot mailing list message.
> Rare is the case where we run on systems of 1 or 2 hardware threads (other than fellows
laptops and there the above likely doesn't matter).

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