shylaja kokoori created CASSANDRA-12787:

             Summary: Reduce instanceOf() type checking to improve performance
                 Key: CASSANDRA-12787
             Project: Cassandra
          Issue Type: Improvement
         Environment: The tests and examples stated were run on:
Intel (R) Xeon (R) CPU E5-2699 v3 @ 2.30GHz, HT Enabled
Oracle JDK 1.8
Cassandra 3.10-SNAPSHOT
Linux kernel 4.7

            Reporter: shylaja kokoori
             Fix For: 3.x
         Attachments: reduce_instanceof_typechecking.pdf

While performance profiling Cassandra with cassandra-stress test on a  pure 
write workload, we noticed that one of the hot methods for Cassandra server is 
the compareTo( PartitionPosition pos) function in 
org.apache.cassandra.db.DecoratedKey. The actual root cause of the problem is a 
slowdown in Java's instanceof operator.

Our initial performance testing using a hacked JVM shows about 61% increase in 
throughput and about 15% reduction in 99 percentile latency. Data shows that 
improvements are from the removal of thread contention caused by Instanceof 

Currently, we are working on a JDK fix to solve this issue. In the meantime, we 
think it will be beneficial to address this issue at Java application level as 
well. We are in the process of creating a patch to Cassandra replacing 
instanceof check with virtual method calls. The patch will be available in this 
thread for review soon. Please let us know your feedback and comments.

For more details please refer to the attached pdf.

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