adaptive default heap size
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Key: CASSANDRA-1469
URL: https://issues.apache.org/jira/browse/CASSANDRA-1469
Project: Cassandra
Issue Type: New Feature
Components: Packaging
Reporter: Jonathan Ellis
Fix For: 0.7 beta 2
Cassandra comes out of the box with very conservative defaults, especially in
-Xmx and memtable sizes, which leads to complaints of poor performance or even
OOM conditions under heavy load. But changing these to be aggressive can cause
the same problem: most servers enable swap out of the box, so asking for a 4GB
or 8GB heap could allocate happily but also cause problems when it starts
paging.
Proposed solution is to update the start script to set Xmx to half of system
ram ("free -m | awk '/Mem:/ {print $2}'"). Memtable defaults will have to be
handled by Java, but we can do that based on heap size (Runtime.maxMemory).
An alternative suggestion was to provide "small", "medium", "large"
configurations, but this plays poorly with rpm and deb packages. I think the
adaptive approach is more promising.
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