rocksdb/java/jmh/README.md
Adam Retter 6477075f2c JMH microbenchmarks for RocksJava (#6241)
Summary:
This is the start of some JMH microbenchmarks for RocksJava.

Such benchmarks can help us decide on performance improvements of the Java API.

At the moment, I have only added benchmarks for various Comparator options, as that is one of the first areas where I want to improve performance. I plan to expand this to many more tests.

Details of how to compile and run the benchmarks are in the `README.md`.

A run of these on a XEON 3.5 GHz 4vCPU (QEMU Virtual CPU version 2.5+) / 8GB RAM KVM with Ubuntu 18.04, OpenJDK 1.8.0_232, and gcc 8.3.0 produced the following:

```
# Run complete. Total time: 01:43:17

REMEMBER: The numbers below are just data. To gain reusable insights, you need to follow up on
why the numbers are the way they are. Use profilers (see -prof, -lprof), design factorial
experiments, perform baseline and negative tests that provide experimental control, make sure
the benchmarking environment is safe on JVM/OS/HW level, ask for reviews from the domain experts.
Do not assume the numbers tell you what you want them to tell.

Benchmark                                         (comparatorName)   Mode  Cnt       Score       Error  Units
ComparatorBenchmarks.put                           native_bytewise thrpt   25   122373.920 ±  2200.538  ops/s
ComparatorBenchmarks.put              java_bytewise_adaptive_mutex thrpt   25    17388.201 ±  1444.006  ops/s
ComparatorBenchmarks.put          java_bytewise_non-adaptive_mutex thrpt   25    16887.150 ±  1632.204  ops/s
ComparatorBenchmarks.put       java_direct_bytewise_adaptive_mutex thrpt   25    15644.572 ±  1791.189  ops/s
ComparatorBenchmarks.put   java_direct_bytewise_non-adaptive_mutex thrpt   25    14869.601 ±  2252.135  ops/s
ComparatorBenchmarks.put                   native_reverse_bytewise thrpt   25   116528.735 ±  4168.797  ops/s
ComparatorBenchmarks.put      java_reverse_bytewise_adaptive_mutex thrpt   25    10651.975 ±   545.998  ops/s
ComparatorBenchmarks.put  java_reverse_bytewise_non-adaptive_mutex thrpt   25    10514.224 ±   930.069  ops/s
```

Indicating a ~7x difference between comparators implemented natively (C++) and those implemented in Java. Let's see if we can't improve on that in the near future...
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6241

Differential Revision: D19290410

Pulled By: pdillinger

fbshipit-source-id: 25d44bf3a31de265502ed0c5d8a28cf4c7cb9c0b
2020-01-07 15:46:09 -08:00

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Markdown

# JMH Benchmarks for RocksJava
These are micro-benchmarks for RocksJava functionality, using [JMH (Java Microbenchmark Harness)](https://openjdk.java.net/projects/code-tools/jmh/).
## Compiling
**Note**: This uses a specific build of RocksDB that is set in the `<version>` element of the `dependencies` section of the `pom.xml` file. If you are testing local changes you should build and install a SNAPSHOT version of rocksdbjni, and update the `pom.xml` of rocksdbjni-jmh file to test with this.
```bash
$ mvn package
```
## Running
```bash
$ java -jar target/rocksdbjni-jmh-1.0-SNAPSHOT-benchmarks.jar
```
NOTE: you can append `-help` to the command above to see all of the JMH runtime options.