JMH intro

原文链接

JMH (Java Microbenchmark Harness)

package com.mkyong.benchmark;

import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.RunnerException;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.TimeUnit;

@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.MILLISECONDS)
@State(Scope.Benchmark)
@Fork(value = 2, jvmArgs = {"-Xms2G", "-Xmx2G"})
//@Warmup(iterations = 3)
//@Measurement(iterations = 8)
public class BenchmarkLoop {

    @Param({"10000000"})
    private int N;

    private List<String> DATA_FOR_TESTING;

    public static void main(String[] args) throws RunnerException {

        Options opt = new OptionsBuilder()
                .include(BenchmarkLoop.class.getSimpleName())
                .forks(1)
                .build();

        new Runner(opt).run();
    }

    @Setup
    public void setup() {
        DATA_FOR_TESTING = createData();
    }

    @Benchmark
    public void loopFor(Blackhole bh) {
        for (int i = 0; i < DATA_FOR_TESTING.size(); i++) {
            String s = DATA_FOR_TESTING.get(i); //take out n consume, fair with foreach
            bh.consume(s);
        }
    }

    @Benchmark
    public void loopWhile(Blackhole bh) {
        int i = 0;
        while (i < DATA_FOR_TESTING.size()) {
            String s = DATA_FOR_TESTING.get(i);
            bh.consume(s);
            i++;
        }
    }

    @Benchmark
    public void loopForEach(Blackhole bh) {
        for (String s : DATA_FOR_TESTING) {
            bh.consume(s);
        }
    }

    @Benchmark
    public void loopIterator(Blackhole bh) {
        Iterator<String> iterator = DATA_FOR_TESTING.iterator();
        while (iterator.hasNext()) {
            String s = iterator.next();
            bh.consume(s);
        }
    }

    private List<String> createData() {
        List<String> data = new ArrayList<>();
        for (int i = 0; i < N; i++) {
            data.add("Number : " + i);
        }
        return data;
    }

}

主要是针对单个函数部分进行benchmark的测试

<build>
	<plugins>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-shade-plugin</artifactId>
			<version>3.2.0</version>
			<executions>
				<execution>
					<phase>package</phase>
					<goals>
						<goal>shade</goal>
					</goals>
					<configuration>
						<finalName>benchmarks</finalName>
						<transformers>
							<transformer
									implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
								<mainClass>org.openjdk.jmh.Main</mainClass>
							</transformer>
						</transformers>
					</configuration>
				</execution>
			</executions>
		</plugin>
	</plugins>
</build>