JMH Gradle Plugin

This plugin integrates the JMH micro-benchmarking framework with Gradle.

Usage

To enable the plugin, you must add this to your build.gradle file:

build.gradle

buildscript {
   repositories {
      jcenter()
   }
   dependencies {
      classpath 'me.champeau.gradle:jmh-gradle-plugin:0.1'
   }
}

repositories {
   jcenter() // repository from which JMH will be downloaded
}

apply plugin: 'me.champeau.gradle.jmh'

Configuration

The plugin makes it easy to integrate into an existing project thanks to a specific configuration. In particular, benchmark source files are expected to be found in the src/jmh directory:

src/jmh
     |- java       : java sources for benchmarks
     |- resources  : resources for benchmarks

The plugin creates a jmh configuration that you should use if your benchmark files depend on a 3rd party library. For example, if you want to use commons-io, you can add the dependency like this:

build.gradle

dependencies {
    jmh 'commons-io:commons-io:2.4'
}

The plugin uses JMH 0.9. You can upgrade the version just by changing the version in the dependencies block:

build.gradle

dependencies {
    jmh 'org.openjdk.jmh:jmh-core:0.9'
    jmh 'org.openjdk.jmh:jmh-generator-annprocess:0.9'
}

Tasks

The project will add several tasks:

• jhmClasses : compiles the benchmarks

• jhmJar : builds the JMH jar containing the JHM runtime and your compiled benchmark classes

• jmh : executes the benchmarks

The jmh task is the main task and depends on the others so it is in general sufficient to execute this task:

gradle jmh

Configuration options

By default, all benchmarks will be executed, and the results will be generated into $buildDir/reports/jmh. But you can change various options thanks to the jmh configuration block. All configurations variables apart from include are unset, implying that they fall back to the default JMH values:

build.gradle

jmh {
   include = 'some regular expression' // include pattern (regular expression) for benchmarks to be executed
   exclude = 'some regular expression' // exclude pattern (regular expression) for benchmarks to be executed
   iterations = 10 // Number of measurement iterations to do.
   benchmarkMode = 'thrpt' // Benchmark mode. Available modes are: [Throughput/thrpt, AverageTime/avgt, SampleTime/sample, SingleShotTime/ss, All/all]
   batchSize = 1 // Batch size: number of benchmark method calls per operation. (some benchmark modes can ignore this setting)
   fork = 2 // How many times to forks a single benchmark. Use 0 to disable forking altogether
   failOnError = false // Should JMH fail immediately if any benchmark had experienced the unrecoverable error?
   forceGC = false // Should JMH force GC between iterations?
   jvm = 'myjvm' // Custom JVM to use when forking.
   jvmArgs = 'Custom JVM args to use when forking.'
   jvmArgsAppend = 'Custom JVM args to use when forking (append these)'
   jvmArgsPrepend = 'Custom JVM args to use when forking (prepend these)'
   humanOutputFile = project.file("${project.buildDir}/reports/jmh/human.txt") // human-readable output file
   resultsFile = project.file("${project.buildDir}/reports/jmh/results.txt") // results file
   operationsPerInvocation = 10 // Operations per invocation.
   benchmarkParameters =  [:] // Benchmark parameters.
   profilers = [] // Use profilers to collect additional data.
   timeOnIteration = '1s' // Time to spend at each measurement iteration.
   resultFormat = 'op/s' // Result format type.
   synchronizeIterations = false // Synchronize iterations?
   threads = 4 // Number of worker threads to run with.
   threadGroups = [2,3,4] //Override thread group distribution for asymmetric benchmarks.
   timeUnit = 'ms' // Output time unit. Available time units are: [m, s, ms, us, ns].
   verbosity = 'NORMAL' // Verbosity mode. Available modes are: [SILENT, NORMAL, EXTRA]
   warmup = '1s' // Time to spend at each warmup iteration.
   warmupBatchSize = 10 // Warmup batch size: number of benchmark method calls per operation.
   warmupForks = 0 // How many warmup forks to make for a single benchmark. 0 to disable warmup forks.
   warmupIterations = 1 // Number of warmup iterations to do.
   warmupMode = 'INDI' // Warmup mode for warming up selected benchmarks. Warmup modes are: [INDI, BULK, BULK_INDI].
   warmupBenchmarks = ['.*Warmup'] // Warmup benchmarks to include in the run in addition to already selected. JMH will not measure these benchmarks, but only use them for the warmup.
}

Dependency on project files

The jmh plugin makes it easy to test existing sources without having to create a separate project for this. This is the reason why you must put your files into src/jmh/java instead of src/main/java. This means that by default, the jmh task depends on your main source set.