JMH convention plugin

buildSrc/build.gradle.kts

@@ -109,6 +109,8 @@ dependencies {
   implementation("com.fasterxml.jackson.core:jackson-core")
 
   compileOnly(libs.develocity)
+
+  testImplementation("me.champeau.jmh:jmh-gradle-plugin:0.7.3")
 }
 
 tasks.compileKotlin {

buildSrc/src/main/kotlin/datadog/gradle/plugin/testJvmConstraints/TestJvmConstraintsPlugin.kt

@@ -13,6 +13,10 @@ import org.gradle.testing.jacoco.plugins.JacocoTaskExtension
 
 class TestJvmConstraintsPlugin : Plugin<Project> {
   override fun apply(project: Project) {
+    if (project.extensions.findByName(TEST_JVM_CONSTRAINTS) != null) {
+      return
+    }
+
     project.pluginManager.apply(JavaPlugin::class.java)
 
     val projectExtension = project.extensions.create<TestJvmConstraintsExtension>(TEST_JVM_CONSTRAINTS)

buildSrc/src/main/kotlin/dd-trace-java.jmh-conventions.gradle.kts

@@ -0,0 +1,54 @@
+import datadog.gradle.plugin.testJvmConstraints.TestJvmSpec
+import org.gradle.api.provider.ListProperty
+import org.gradle.api.provider.Property
+
+/*
+ * Applies JMH with defaults from `-PtestJvm` and `-Pjmh.*`. Modules can override them in their
+ * `jmh {}` block.
+ */
+// This plugin is produced by the same buildSrc build, so it cannot be resolved from this
+// precompiled script's `plugins {}` block. Apply it by ID once both plugins are available at runtime.
+pluginManager.apply("dd-trace-java.test-jvm-constraints")
+
+// JMH is versioned in the root build with `apply false`, not added to buildSrc's implementation
+// classpath. Applying it by ID here reuses the consuming build's plugin classpath.
+pluginManager.apply("me.champeau.jmh")
+
+val testJvmSpec = TestJvmSpec(project)
+val jmh = extensions.getByName("jmh")
+
+
+jmhProperty<String>("getJvm").convention(testJvmSpec.javaTestLauncher.map { it.executablePath.asFile.absolutePath })
+providers.gradleProperty("jmh.includes").map(::commaSeparated).let {
+  if (it.isPresent) {
+    jmhListProperty("getIncludes").convention(it.map { includes -> listOf(includes.joinToString("|")) })
+  }
+}
+providers.gradleProperty("jmh.profilers").map(::commaSeparated).let {
+  if (it.isPresent) {
+    jmhListProperty("getProfilers").convention(it)
+  }
+}
+providers.gradleProperty("jmh.forks").map(String::toInt).let {
+  if (it.isPresent) {
+    jmhProperty<Int>("getFork").convention(it)
+  }
+}
+providers.gradleProperty("jmh.threads").map(String::toInt).let {
+  if (it.isPresent) {
+    jmhProperty<Int>("getThreads").convention(it)
+  }
+}
+
+// JMH types are not on buildSrc's compile classpath, so access its extension through Gradle's public
+// property types.
+@Suppress("UNCHECKED_CAST")
+fun <T : Any> jmhProperty(getterName: String): Property<T> =
+  jmh.javaClass.getMethod(getterName).invoke(jmh) as Property<T>
+
+@Suppress("UNCHECKED_CAST")
+fun jmhListProperty(getterName: String): ListProperty<String> =
+  jmh.javaClass.getMethod(getterName).invoke(jmh) as ListProperty<String>
+
+fun commaSeparated(value: String): List<String> =
+  value.split(",").map(String::trim).filter(String::isNotEmpty)

buildSrc/src/test/kotlin/datadog/gradle/plugin/jmh/JmhConventionsPluginTest.kt

@@ -0,0 +1,126 @@
+package datadog.gradle.plugin.jmh
+
+import datadog.gradle.plugin.testJvmConstraints.TestJvmConstraintsExtension.Companion.TEST_JVM_CONSTRAINTS
+import datadog.gradle.plugin.testJvmConstraints.TestJvmSpec
+import me.champeau.jmh.JmhParameters
+import org.assertj.core.api.Assertions.assertThat
+import org.gradle.api.JavaVersion
+import org.gradle.testfixtures.ProjectBuilder
+import org.junit.jupiter.api.Test
+
+class JmhConventionsPluginTest {
+  @Test
+  fun `plugin applies jmh and test-jvm-constraints`() {
+    val project = ProjectBuilder.builder().build()
+
+    project.pluginManager.apply("dd-trace-java.jmh-conventions")
+
+    assertThat(project.plugins.hasPlugin("me.champeau.jmh")).isTrue()
+    assertThat(project.extensions.findByName(TEST_JVM_CONSTRAINTS)).isNotNull()
+  }
+
+  @Test
+  fun `plugin provides the test jvm as an overridable default`() {
+    val propertyName = "org.gradle.project.${TestJvmSpec.TEST_JVM}"
+    val previousValue = System.setProperty(propertyName, JavaVersion.current().majorVersion)
+
+    try {
+      val project = ProjectBuilder.builder().build()
+
+      project.pluginManager.apply("dd-trace-java.jmh-conventions")
+
+      val jmh = project.extensions.getByType(JmhParameters::class.java)
+      val expectedExecutable = TestJvmSpec(project).javaTestLauncher.get().executablePath.asFile.absolutePath
+      assertThat(jmh.jvm.get()).isEqualTo(expectedExecutable)
+
+      jmh.jvm.set("module-jvm")
+      assertThat(jmh.jvm.get()).isEqualTo("module-jvm")
+    } finally {
+      if (previousValue == null) {
+        System.clearProperty(propertyName)
+      } else {
+        System.setProperty(propertyName, previousValue)
+      }
+    }
+  }
+
+  @Test
+  fun `plugin provides jmh project properties as defaults`() {
+    withGradleProperties(
+      "jmh.includes" to "FooBenchmark, BarBenchmark",
+      "jmh.profilers" to "stack, gc",
+      "jmh.forks" to "1",
+      "jmh.threads" to "1",
+    ) {
+      val project = ProjectBuilder.builder().build()
+
+      project.pluginManager.apply("dd-trace-java.jmh-conventions")
+
+      val jmh = project.extensions.getByType(JmhParameters::class.java)
+      assertThat(jmh.includes.get()).containsExactly("FooBenchmark|BarBenchmark")
+      assertThat(jmh.profilers.get()).containsExactly("stack", "gc")
+      assertThat(jmh.fork.get()).isEqualTo(1)
+      assertThat(jmh.threads.get()).isEqualTo(1)
+    }
+  }
+
+  @Test
+  fun `jmh properties are absent when the project properties are not set`() {
+    val project = ProjectBuilder.builder().build()
+
+    project.pluginManager.apply("dd-trace-java.jmh-conventions")
+
+    val jmh = project.extensions.getByType(JmhParameters::class.java)
+    assertThat(jmh.includes.get()).isEmpty()
+    assertThat(jmh.profilers.get()).isEmpty()
+    assertThat(jmh.fork.isPresent).isFalse()
+    assertThat(jmh.threads.isPresent).isFalse()
+  }
+
+  @Test
+  fun `module jmh settings override project property defaults`() {
+    withGradleProperties(
+      "jmh.profilers" to "async",
+      "jmh.forks" to "1",
+    ) {
+      val project = ProjectBuilder.builder().build()
+
+      project.pluginManager.apply("dd-trace-java.jmh-conventions")
+
+      val jmh = project.extensions.getByType(JmhParameters::class.java)
+      jmh.profilers.set(listOf("gc"))
+      jmh.fork.set(4)
+
+      assertThat(jmh.profilers.get()).containsExactly("gc")
+      assertThat(jmh.fork.get()).isEqualTo(4)
+    }
+  }
+
+  @Test
+  fun `applying test-jvm-constraints before jmh-conventions is idempotent`() {
+    val project = ProjectBuilder.builder().build()
+
+    project.pluginManager.apply("dd-trace-java.test-jvm-constraints")
+    project.pluginManager.apply("dd-trace-java.jmh-conventions")
+
+    assertThat(project.extensions.findByName(TEST_JVM_CONSTRAINTS)).isNotNull()
+  }
+
+  private fun withGradleProperties(vararg properties: Pair<String, String>, assertions: () -> Unit) {
+    val systemProperties = properties.associate { (name, value) -> "org.gradle.project.$name" to value }
+    val previousValues = systemProperties.keys.associateWith(System::getProperty)
+
+    try {
+      systemProperties.forEach(System::setProperty)
+      assertions()
+    } finally {
+      previousValues.forEach { (name, value) ->
+        if (value == null) {
+          System.clearProperty(name)
+        } else {
+          System.setProperty(name, value)
+        }
+      }
+    }
+  }
+}

buildSrc/src/test/kotlin/datadog/gradle/plugin/testJvmConstraints/TestJvmConstraintsPluginTest.kt

@@ -21,6 +21,19 @@ class TestJvmConstraintsPluginTest {
     assertThat(testTask.extensions.findByName(TEST_JVM_CONSTRAINTS)).isInstanceOf(TestJvmConstraintsExtension::class.java)
   }
 
+  @Test
+  fun `plugin is idempotent when applied more than once`() {
+    val project = ProjectBuilder.builder().build()
+
+    project.pluginManager.apply("dd-trace-java.test-jvm-constraints")
+    TestJvmConstraintsPlugin().apply(project)
+
+    val testTask = project.tasks.named("test", GradleTest::class.java).get()
+
+    assertThat(project.extensions.findByName(TEST_JVM_CONSTRAINTS)).isInstanceOf(TestJvmConstraintsExtension::class.java)
+    assertThat(testTask.extensions.findByName(TEST_JVM_CONSTRAINTS)).isInstanceOf(TestJvmConstraintsExtension::class.java)
+  }
+
   @Test
   fun `jacoco is disabled for additional test jvm when coverage is not checked`() {
     val testTask = testTaskWithJacoco()

components/json/build.gradle.kts

@@ -1,5 +1,5 @@
 plugins {
-  id("me.champeau.jmh")
+  id("dd-trace-java.jmh-conventions")
 }
 
 apply(from = "$rootDir/gradle/java.gradle")

dd-java-agent/agent-bootstrap/build.gradle

@@ -1,7 +1,7 @@
 // The shadowJar of this project will be injected into the JVM's bootstrap classloader
 plugins {
   id 'com.gradleup.shadow'
-  id 'me.champeau.jmh'
+  id 'dd-trace-java.jmh-conventions'
 }
 
 apply from: "$rootDir/gradle/java.gradle"

dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/dbm/SharedDBCommenterBenchmark.java

@@ -32,11 +32,8 @@
  * short-circuits on the first check.
  *
  * <pre>
- *   # agent-bootstrap has no -Pjmh.includes wiring yet (a generalization is in flight), so for now
- *   # either run the whole module (only a handful of benchmarks) ...
- *   ./gradlew :dd-java-agent:agent-bootstrap:jmh
- *   # ... or hack a temporary filter into agent-bootstrap/build.gradle: jmh { includes = ['SharedDBCommenter.*'] }
- *   # add -prof gc (gc.alloc.rate.norm) to corroborate the allocation delta.
+ *   ./gradlew :dd-java-agent:agent-bootstrap:jmh -Pjmh.includes=SharedDBCommenterBenchmark -Pjmh.profilers=gc
+ *   # gc.alloc.rate.norm (B/op) corroborates the allocation delta.
  * </pre>
  *
  * <p><b>Results</b> (JDK 17, MacBook M-series, {@code @Threads(8)}, {@code @Fork(5)}, {@code -prof

dd-java-agent/agent-iast/build.gradle

@@ -3,7 +3,7 @@ import net.ltgt.gradle.errorprone.CheckSeverity
 
 plugins {
   id 'com.gradleup.shadow'
-  id 'me.champeau.jmh'
+  id 'dd-trace-java.jmh-conventions'
   id 'com.google.protobuf' version '0.10.0'
   id 'net.ltgt.errorprone' version '3.1.0'
   id 'dd-trace-java.version-file'

dd-java-agent/agent-profiling/profiling-ddprof/build.gradle

@@ -1,6 +1,6 @@
 plugins {
   id 'com.gradleup.shadow'
-  id 'me.champeau.jmh'
+  id 'dd-trace-java.jmh-conventions'
 }
 
 ext {

dd-java-agent/agent-tooling/build.gradle

@@ -1,5 +1,5 @@
 plugins {
-  id 'me.champeau.jmh'
+  id 'dd-trace-java.jmh-conventions'
   id 'java-test-fixtures'
 }
 apply from: "$rootDir/gradle/java.gradle"

dd-java-agent/appsec/build.gradle

@@ -2,7 +2,7 @@ import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 
 plugins {
   id 'com.gradleup.shadow'
-  id 'me.champeau.jmh'
+  id 'dd-trace-java.jmh-conventions'
   id 'dd-trace-java.version-file'
 }
 

dd-java-agent/benchmark/build.gradle

@@ -1,5 +1,5 @@
 plugins {
-  id 'me.champeau.jmh'
+  id 'dd-trace-java.jmh-conventions'
 }
 
 apply from: "$rootDir/gradle/java.gradle"

dd-java-agent/instrumentation/jdbc/build.gradle

@@ -1,6 +1,6 @@
 plugins {
   id 'java-test-fixtures'
-  id 'me.champeau.jmh'
+  id 'dd-trace-java.jmh-conventions'
 }
 
 muzzle {

dd-trace-core/build.gradle

@@ -1,7 +1,5 @@
-import datadog.gradle.plugin.testJvmConstraints.TestJvmSpec
-
 plugins {
-  id 'me.champeau.jmh'
+  id 'dd-trace-java.jmh-conventions'
   id 'dd-trace-java.version-file'
 }
 
@@ -129,14 +127,4 @@ dependencies {
 jmh {
   jmhVersion = libs.versions.jmh.get()
   duplicateClassesStrategy = DuplicatesStrategy.EXCLUDE
-  if (project.hasProperty('jmh.includes')) {
-    includes = [project.property('jmh.includes').replace(',', '|')]
-  }
-  if (project.hasProperty('jmh.profilers')) {
-    profilers = project.property('jmh.profilers').tokenize(',')
-  }
-  if (project.hasProperty('testJvm')) {
-    def testJvmSpec = new TestJvmSpec(project)
-    jvm = testJvmSpec.javaTestLauncher.map { it.executablePath.asFile.absolutePath }
-  }
 }

dd-trace-ot/build.gradle.kts

@@ -3,7 +3,7 @@ import groovy.lang.Closure
 plugins {
   `java-library`
   id("com.gradleup.shadow")
-  id("me.champeau.jmh")
+  id("dd-trace-java.jmh-conventions")
 }
 
 description = "dd-trace-ot"

docs/how_to_work_with_gradle.md

@@ -971,6 +971,49 @@ tasks.named<Test>("latestDepTest") {
 ./gradlew allTests -PtestJvm=zulu11
 ```
 
+### JMH Benchmarks (`dd-trace-java.jmh-conventions` Plugin)
+
+The convention uses the JVM selected by the `dd-trace-java.test-jvm-constraints` plugin via `-PtestJvm` as the 
+JMH launcher. It also maps optional `-Pjmh.*` project properties to JMH parameters, allowing an individual run 
+to be adjusted without editing benchmark annotations.
+Explicit settings in a module’s `jmh {}` block take precedence (i.e. the managed property won't apply).
+
+The new properties enable to override the defaults, in other words 
+
+* without `jmh.forks` or `jmh.threads`, forks and threads come from `@Fork` and `@Threads`; otherwise JMH defaults apply,
+* without `jmh.includes`, JMH runs all discovered benchmarks,
+* without `jmh.profilers`, no profiler is attached unless configured elsewhere.
+
+```Gradle Kotlin DSL
+plugins {
+    id("dd-trace-java.jmh-conventions")
+}
+
+jmh {
+    jmhVersion = libs.versions.jmh.get()
+    duplicateClassesStrategy = DuplicatesStrategy.EXCLUDE
+
+    // jvm, fork, profilers are managed by the jmh convention plugin 
+    threads = 10 // Threads is enforced and jmh.threads won't be applied
+}
+```
+
+| Property        | Effect                                                        |
+|-----------------|---------------------------------------------------------------|
+| `jmh.includes`  | Comma-separated benchmark name patterns to run (a subset run) |
+| `jmh.profilers` | Comma-separated JMH profilers to attach (e.g. `stack`, `gc`)  |
+| `jmh.forks`     | Overrides the fork count for a spot-check run                 |
+| `jmh.threads`   | Overrides the thread count for a spot-check run               |
+
+```bash
+./gradlew :dd-trace-core:jmh -Pjmh.includes=SpanCreationBenchmark -Pjmh.forks=1 -Pjmh.threads=1 -PtestJvm=21
+```
+
+**Tips:**
+
+* Keep the benchmark's fork and thread settings aligned with what it measures.
+* Use `-Pjmh.profilers=gc` when investigating allocations.
+
 ### `tracerJava` Extension
 
 Manages multi-version Java source sets, allowing a single project to compile code targeting different JVM versions.
@@ -1576,4 +1619,3 @@ The report shows exactly which code paths capture disallowed references.
 # Validate build logic without running tasks
 ./gradlew help --scan
 ```
-