JMH Testing with Scala

2018-02-22 Discuss

JMH is the Java Microbenchmark Harness provided by the OpenJDK project. It can be a useful tool for validating assumptions about the performance of small code sections subject to many iterations.

See the following links for more details:

• OpenJDK Code Tools: jmh
• JMH Tutorial

Gradle

A Gradle plugin is available for JMH.

Project layout:

.
├── build.gradle
├── gradle
│   └── wrapper
│       ├── gradle-wrapper.jar
│       └── gradle-wrapper.properties
├── gradlew
├── gradlew.bat
└── src
    └── jmh
        └── scala
            └── io
                └── github
                    └── brharrington
                        ├── AtomicLongUpdate.scala
                        ├── CurrentTimeMillis.scala
                        ├── NanoTime.scala
                        └── TimeLimiting.scala

The build.gradle configuration:

plugins {
    id 'scala'
    id 'idea'
    id 'me.champeau.gradle.jmh' version '0.4.5'
}

repositories {
    jcenter()
}

dependencies {
    compile 'com.netflix.servo:servo-core:0.12.17'
    compile 'org.scala-lang:scala-library:2.12.4'
}

idea {
    module {
        testSourceDirs += sourceSets.jmh.scala.srcDirs
    }
}

Run the tests:

./gradlew jmh

sbt

An sbt plugin is available for JMH.

Example project layout:

.
├── build.sbt
├── project
│   ├── build.properties
│   ├── plugins.sbt
│   ├── sbt
│   └── sbt-launch-1.0.0.jar
└── src
    └── main
        └── scala
            └── io
                └── github
                    └── brharrington
                        ├── AtomicLongUpdate.scala
                        ├── CurrentTimeMillis.scala
                        ├── NanoTime.scala
                        └── TimeLimiting.scala

The build.sbt configuration:

name := "misc-jmh"

organization := "io.github.brharrington"

scalaVersion := "2.12.4"

enablePlugins(JmhPlugin)

libraryDependencies ++= Seq(
    "com.netflix.servo" % "servo-core" % "0.12.17"
)

The plugins.sbt configuration:

addSbtPlugin("pl.project13.scala" % "sbt-jmh" % "0.2.27")

Run the tests:

./project/sbt jmh:run

Example Test Class

package io.github.brharrington

import java.util.concurrent.atomic.AtomicLong

import org.openjdk.jmh.annotations.Benchmark
import org.openjdk.jmh.annotations.Scope
import org.openjdk.jmh.annotations.State
import org.openjdk.jmh.infra.Blackhole

@State(Scope.Thread)
class AtomicLongUpdate {

  private val value = new AtomicLong()

  @Benchmark
  def incrementAndGet(bh: Blackhole): Unit = {
    bh.consume(value.incrementAndGet())
  }

  @Benchmark
  def addAndGet(bh: Blackhole): Unit = {
    bh.consume(value.addAndGet(42))
  }

  @Benchmark
  def get(bh: Blackhole): Unit = {
    bh.consume(value.get())
  }

}