2.8 配套代码：JMH 与 kotlinx-benchmark 的完整配置

// build.gradle.kts
plugins {
    kotlin("jvm") version "2.0.20"
    kotlin("kapt") version "2.0.20"                 // ← Kotlin 用 JMH 必须
    id("me.champeau.jmh") version "0.7.2"
}

repositories { mavenCentral() }

dependencies {
    jmh("org.openjdk.jmh:jmh-core:1.37")
    jmh("org.openjdk.jmh:jmh-generator-annprocess:1.37")
    kaptJmh("org.openjdk.jmh:jmh-generator-annprocess:1.37")   // ← 关键，缺了会静默失败
}

// 基准源码放在 src/jmh/kotlin，与 main/test 分开

// src/jmh/kotlin/bench/SumBenchmark.kt
package bench

import org.openjdk.jmh.annotations.*
import org.openjdk.jmh.infra.Blackhole
import java.util.concurrent.TimeUnit
import kotlin.random.Random

@State(Scope.Benchmark)
@BenchmarkMode(Mode.Throughput)
@OutputTimeUnit(TimeUnit.MILLISECONDS)
@Warmup(iterations = 3, time = 1)
@Measurement(iterations = 5, time = 1)
@Fork(2)
@Threads(1)
open class SumBenchmark {

    private lateinit var data: IntArray

    @Setup(Level.Trial)
    fun setup() {
        val rnd = Random(42)
        data = IntArray(4096) { rnd.nextInt() }        // 运行时随机输入
    }

    @Benchmark
    fun sumForLoop(bh: Blackhole) {
        var s = 0L
        for (v in data) s += v
        bh.consume(s)                                  // 消费结果
    }

    @Benchmark
    fun sumWhileLoop(bh: Blackhole) {
        var s = 0L
        var i = 0
        while (i < data.size) { s += data[i]; i++ }
        bh.consume(s)
    }
}

./gradlew jmh

# 结果在 build/reports/jmh/ 下
cat build/reports/jmh/results.txt

Benchmark                  Mode  Cnt   Score    Error   Units
SumBenchmark.sumForLoop   thrpt    2  16.234           ops/ms
SumBenchmark.sumWhileLoop thrpt    2  16.180           ops/ms
SumBenchmark.sumForLoop:gc.alloc.rate   2   0.001     MB/sec

# 覆盖注解里的配置（便于快速试参数）
./gradlew jmh -PjmhFork=3 -PjmhWarmupIterations=5 -PjmhIterations=10

# 打开 GC profiler
./gradlew jmh -PjmhProfilers=gc

# 只跑某个基准
./gradlew jmh -PjmhIncludes="SumBenchmark.sumForLoop"

# 加 JVM 参数（对比不同 GC）
./gradlew jmh -PjmhJvmArgs="-XX:+UseZGC -Xmx4g"

// build.gradle.kts
plugins {
    kotlin("jvm") version "2.0.20"
    id("org.jetbrains.kotlinx.benchmark") version "0.4.11"
}

dependencies {
    implementation("org.jetbrains.kotlinx:kotlinx-benchmark-runtime:0.4.11")
}

benchmark {
    targets { register("main") }
    configurations {
        register("main") {
            warmups = 3
            iterations = 5
            iterationTime = 1
            iterationTimeUnit = "s"
            mode = "thrpt"        // thrpt=吞吐, avgt=平均耗时, sample=采样
            outputTimeUnit = "ms"
        }
    }
}

// src/main/kotlin/bench/SumBenchmark.kt
package bench

import kotlinx.benchmark.*
import kotlin.random.Random

@State(Scope.Benchmark)
class SumBenchmark {

    private lateinit var data: IntArray

    @Setup
    fun setup() {
        val rnd = Random(42)
        data = IntArray(4096) { rnd.nextInt() }
    }

    @Benchmark
    fun sumForLoop(bh: Blackhole) {         // Blackhole 需要 0.4.9+
        var s = 0L
        for (v in data) s += v
        bh.consume(s)
    }
}

./gradlew benchmark        # 任务名随插件版本略有差异

# 结果默认在 build/reports/benchmarks/，格式为结构化 JSON
ls build/reports/benchmarks/
cat build/reports/benchmarks/main.json

{
  "benchmarks": [
    {
      "name": "bench.SumBenchmark.sumForLoop",
      "mode": "thrpt",
      "score": 16234.5,
      "scoreUnit": "ops/s"
    }
  ]
}