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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-3168) Arena allocation causes excessive flushing on small heaps
Date Fri, 09 Sep 2011 13:54:08 GMT
Arena allocation causes excessive flushing on small heaps
---------------------------------------------------------

                 Key: CASSANDRA-3168
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3168
             Project: Cassandra
          Issue Type: Bug
    Affects Versions: 1.0
            Reporter: Jonathan Ellis
            Assignee: Jonathan Ellis
             Fix For: 1.0


adding allocator.size() to Memtable.getLiveSize has two problems:

1) it double-counts allocated parts of regions
2) it makes the size of an empty memtable the size of a single region

(2) is a particular problem because flushing a nearly-empty memtable will not actually free
up much memory -- we just trade one almost-empty region, for another.  In testing, I even
saw this happening to the low-traffic system tables like LocationInfo.

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