Fix Version/s: None
The tests and examples stated were run on:
Intel (R) Xeon (R) CPU E5-2699 v3 @ 2.30GHz, HT Enabled
Oracle JDK 1.8
Linux kernel 4.7
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 operator.
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.