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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-1968) Increase JVM young generation size
Date Fri, 21 Jan 2011 05:49:46 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1968?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12984580#action_12984580
] 

Jonathan Ellis commented on CASSANDRA-1968:
-------------------------------------------

Yes, I meant young gen.

An insert-heavy workload will have more of the young gen survive since we have to keep data
around in memtables until flush.  With a read-heavy load almost all of it is discarded.  Here
are some ParNew collections with about a 1.5G young gen, mTT=1, serving mostly reads:

{code}
49527.273: [GC 49527.274: [ParNew
Desired survivor size 107347968 bytes, new threshold 1 (max 1)
- age   1:   15782840 bytes,   15782840 total
: 1696530K->21789K(1887488K), 0.0737280 secs] 6279370K->4617936K(12373248K), 0.0745280
secs] [Times: user=0.41 sys=0.00, real=0.07 secs] 
Total time for which application threads were stopped: 0.1053180 seconds
49534.739: [GC 49534.739: [ParNew
Desired survivor size 107347968 bytes, new threshold 1 (max 1)
- age   1:   14990096 bytes,   14990096 total
: 1699613K->18988K(1887488K), 0.0777830 secs] 6295760K->4629494K(12373248K), 0.0786270
secs]
{code}


> Increase JVM young generation size
> ----------------------------------
>
>                 Key: CASSANDRA-1968
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1968
>             Project: Cassandra
>          Issue Type: Improvement
>    Affects Versions: 0.7.0
>            Reporter: Brandon Williams
>            Assignee: Brandon Williams
>             Fix For: 0.7.1
>
>         Attachments: 1968.txt, 1968_v2.txt
>
>   Original Estimate: 4h
>  Remaining Estimate: 4h
>
> Increasing the young generation size has a profound effect on performance and cpu utilization.
 We should set it explicitly.

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