JMH Java基准测试

JMH是什么

JMH(Java Microbenchmark Harness)是Java基准测试工具

JMH使用方式

官方参考案例：https://github.com/openjdk/jmh/tree/master/jmh-samples/src/main/java/org/openjdk/jmh/samples

引入jmh依赖

        <dependency>
            <groupId>org.openjdk.jmh</groupId>
            <artifactId>jmh-core</artifactId>
            <version>1.23</version>
        </dependency>
        <dependency>
            <groupId>org.openjdk.jmh</groupId>
            <artifactId>jmh-generator-annprocess</artifactId>
            <version>1.23</version>
        </dependency>

实现代码

package com.test;

import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;
import org.openjdk.jmh.results.format.ResultFormatType;
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.concurrent.TimeUnit;

@BenchmarkMode(Mode.AverageTime)
@Warmup(iterations = 3)
@Measurement(iterations = 5)
@Threads(4)
@Fork(1)
@State(value = Scope.Benchmark)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
public class AddTest {

    @Param(value = {"100", "1000", "10000"})
    private int length;

    private static int val1 = 0;
    private static int val2 = 0;
    private static int val3 = 0;
    private Object o2 = new Object();
    private Object o3 = new Object();

    @Benchmark
    public void method1(Blackhole blackhole) {
        for (int i = 0; i < length; i++) {
            m1();
        }
        blackhole.consume(val1);
    }

    public synchronized void m1() {
        val1++;
    }

    public synchronized void m2() {
        synchronized (o2) {
            val2++;
        }
    }

    public void m3() {
        synchronized (o3) {
            val3++;
        }
    }

    @Benchmark
    public void method2(Blackhole blackhole) {
        for (int i = 0; i < length; i++) {
            m2();
        }
        blackhole.consume(val2);
    }

    @Benchmark
    public void method3(Blackhole blackhole) {
        for (int i = 0; i < length; i++) {
            m3();
        }
        blackhole.consume(val3);
    }

    public static void main(String[] args) throws RunnerException {
        Options opt = new OptionsBuilder()
                .include(AddTest.class.getSimpleName())
                .result("result.json")
                .resultFormat(ResultFormatType.JSON).build();
        new Runner(opt).run();
    }
}

以上代码，会将method1、method2、method3分别将 Param中的length 100、1000、10000执行一次，预热执行3次、正式执行5次，统计时间。也就是method1、method2、method3分别会执行24次

注释解释

@BenchmarkMode(Mode.AverageTime)

基准测试的模式，可选择吞吐量、平均响应时间等

Throughput("thrpt", "Throughput, ops/time"),
AverageTime("avgt", "Average time, time/op"),
SampleTime("sample", "Sampling time"),
SingleShotTime("ss", "Single shot invocation time"),
All("all", "All benchmark modes");