JMH (Java Microbenchmark Harness) Lightning Talk

• JMH is a Java harness for building, running, and analysing nano/micro/milli/macro benchmarks written in Java and other languages targeting the JVM.
• Developed by OpenJDK team
• Provides annotation driven API to easily develop correctly designed benchmarks
• Allows to modify behavior of compiler

Hello world example:

    @Benchmark
    @BenchmarkMode(Mode.AverageTime)
    @OutputTimeUnit(TimeUnit.MICROSECONDS)
    public void testRecursiveFibonacci30(Blackhole blackhole){
        blackhole.consume(recursiveFibonacci(30));
    }

    private static long recursiveFibonacci(int n) {
        if (n <= 1) return n;
        else return recursiveFibonacci(n-1) + recursiveFibonacci(n-2);
    }

Official samples

Pitfalls of Java benchmarks:

• JIT
• Loop optimizations
• dead-code elimination

Alternatives:

• Google Caliper

Resources:

• JMH vs Caliper: reference thread
• How do I write a correct micro-benchmark in Java?