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From "Yang Yang (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-3287) limit row cache size as a proportion of sstable size
Date Fri, 30 Sep 2011 20:28:46 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-3287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13118399#comment-13118399
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Yang Yang commented on CASSANDRA-3287:
--------------------------------------

also a cap on the total size of all row caches would also be helpful
                
> limit row cache size as a proportion of sstable size
> ----------------------------------------------------
>
>                 Key: CASSANDRA-3287
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3287
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Yang Yang
>            Priority: Minor
>
> I was debugging some problem,
> then I found that my memory size increased extremely fast, 
> and finally reached my old gen total, and then CMS was starting all the time, back-to-back.
> even after I force a full GC, the old gen space is not decreasing any.
> so I invoked invalidate cache from jmx, then did GC, now the old gen size went down.
> so it's due to row cache.
> but my row cache is really not that big.
> then I realized that it's due to too many small sstables. each sstable has the same size
row cache. then for the smaller sstables, it's too favorable: they have a higher retention
ratio, while in fact we can assume that the hit ratio should be the same for all sstables,
particularly if you have a random access pattern.
> if this makes sense, I can put in a simple patch on calling the constructor of the rowcache


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