Reduce GC overhead
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Key: CASSANDRA-504
URL: https://issues.apache.org/jira/browse/CASSANDRA-504
Project: Cassandra
Issue Type: Improvement
Environment: debian lenny amd64 Java(TM) SE Runtime Environment (build
1.6.0_12-b04)
Reporter: Brandon Williams
Priority: Minor
The Concurrent Mark Sweep GC is using about 30% of the cpu during inserts.
This is not reported as GC time by jconsole, but can be observed by finding the
thread with jstack and watching it via top. This is due to the
CMSInitiatingOccupancyFraction=1 setting being passed to the JVM. Setting this
to 1 is nonsensical, the default is 68.
I tested with some runs of stress.py with 200k inserts, and removing
CMSInitiatingOccupancyFraction causes the 30% cpu usage to disappear. ParNew
GC time was 28-29s. Adding SurvivorRatio=128 and MaxTenuringThreshold=0 drops
the GC time to 18-20s.
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