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From "Yang Yang (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-3287) limit row cache size as a proportion of sstable size
Date Fri, 30 Sep 2011 20:26:45 GMT
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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