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From "shylaja kokoori (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-12787) Reduce instanceOf() type checking to improve performance
Date Wed, 19 Oct 2016 16:18:58 GMT


shylaja kokoori commented on CASSANDRA-12787:

Thank you for the suggestion and comments. I am in the process of collecting some data on
what change can produce a result similar to the change we did in the JVM. I have some ideas
will post an update soon.
On the question about tools used, we use an internal tool to measure CPU cycles. Linux perf
and VTune should be able to provide similar information.

> Reduce instanceOf() type checking to improve performance
> --------------------------------------------------------
>                 Key: CASSANDRA-12787
>                 URL:
>             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: instanceof.png, 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 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.

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