Call System.gc only when when log level is debug, fixes KT-11022

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/CleanUpBuildListener.kt

@@ -21,12 +21,7 @@ import org.gradle.BuildAdapter
 import org.gradle.BuildResult
 import org.gradle.api.logging.Logging
 import java.util.concurrent.ScheduledExecutorService
-
-internal fun getUsedMemoryKb(): Long {
-    System.gc()
-    val rt = Runtime.getRuntime()
-    return (rt.totalMemory() - rt.freeMemory()) / 1024
-}
+import kotlin.properties.Delegates
 
 
 private fun comparableVersionStr(version: String) =
@@ -39,13 +34,23 @@ private fun comparableVersionStr(version: String) =
                 ?.let { if (it.all { (it?.value?.length ?: 0).let { it > 0 && it < 4 }}) it else null }
                 ?.joinToString(".", transform = { it!!.value.padStart(3, '0') })
 
+class CleanUpBuildListener(pluginClassLoader: ClassLoader) : BuildAdapter() {
+    companion object {
+        const val FORCE_SYSTEM_GC_MESSAGE = "Forcing System.gc()"
+    }
 
-class FinishBuildListener(pluginClassLoader: ClassLoader, val startMemory: Long) : BuildAdapter() {
-    val log = Logging.getLogger(this.javaClass)
-
+    private val log = Logging.getLogger(this.javaClass)
     private var threadTracker: ThreadTracker? = ThreadTracker()
-
     private val cleanup = CompilerServicesCleanup(pluginClassLoader)
+    private var startMemory: Long? = null
+
+    // There is function with the same name in BuildAdapter,
+    // but it is called before any plugin can attach build listener
+    fun buildStarted() {
+        if (log.isDebugEnabled) {
+            startMemory = getUsedMemoryKb()!!
+        }
+    }
 
     override fun buildFinished(result: BuildResult?) {
         log.kotlinDebug("Build finished listener")
@@ -60,9 +65,22 @@ class FinishBuildListener(pluginClassLoader: ClassLoader, val startMemory: Long)
             gradle.removeListener(this)
         }
 
-        // the value reported here is not necessarily a leak, since it is calculated before collecting the plugin classes
-        // but on subsequent runs in the daemon it should be rather small, then the classes are actually reused by the daemon (see above)
-        getUsedMemoryKb().let { log.kotlinDebug("[PERF] Used memory after build: $it kb (${"%+d".format(it - startMemory)} kb)") }
+        startMemory?.let { startMemoryCopy ->
+            getUsedMemoryKb()?.let { endMemory ->
+                // the value reported here is not necessarily a leak, since it is calculated before collecting the plugin classes
+                // but on subsequent runs in the daemon it should be rather small, then the classes are actually reused by the daemon (see above)
+                log.kotlinDebug("[PERF] Used memory after build: $endMemory kb (difference since build start: ${"%+d".format(endMemory - startMemoryCopy)} kb)")
+            }
+        }
+    }
+
+    private fun getUsedMemoryKb(): Long? {
+        if (!log.isDebugEnabled) return null
+
+        log.lifecycle(FORCE_SYSTEM_GC_MESSAGE)
+        System.gc()
+        val rt = Runtime.getRuntime()
+        return (rt.totalMemory() - rt.freeMemory()) / 1024
     }
 }
 

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinPluginWrapper.kt

@@ -2,18 +2,10 @@ package org.jetbrains.kotlin.gradle.plugin
 
 import org.gradle.api.Plugin
 import org.gradle.api.Project
-import org.gradle.api.artifacts.dsl.DependencyHandler
-import org.gradle.api.artifacts.ConfigurationContainer
-import java.net.URL
-import org.gradle.api.logging.Logging
-import java.util.Properties
-import java.io.FileNotFoundException
 import org.gradle.api.initialization.dsl.ScriptHandler
-import org.gradle.api.invocation.Gradle
 import org.gradle.api.logging.Logger
-import java.lang.reflect.Method
+import org.gradle.api.logging.Logging
 import org.jetbrains.kotlin.gradle.tasks.KotlinTasksProvider
-import java.net.URLClassLoader
 
 // TODO: simplify: the complicated structure is a leftover from dynamic loading of plugin core, could be significantly simplified now
 
@@ -21,9 +13,10 @@ abstract class KotlinBasePluginWrapper: Plugin<Project> {
 
     val log = Logging.getLogger(this.javaClass)
 
-    public override fun apply(project: Project) {
-
-        val startMemory = getUsedMemoryKb()
+    override fun apply(project: Project) {
+        val cleanUpBuildListener = CleanUpBuildListener(this.javaClass.classLoader)
+        cleanUpBuildListener.buildStarted()
+        project.gradle.addBuildListener(cleanUpBuildListener)
 
         val sourceBuildScript = findSourceBuildScript(project)
         if (sourceBuildScript == null) {
@@ -38,7 +31,6 @@ abstract class KotlinBasePluginWrapper: Plugin<Project> {
         val plugin = getPlugin(this.javaClass.classLoader, sourceBuildScript)
         plugin.apply(project)
 
-        project.gradle.addBuildListener(FinishBuildListener(this.javaClass.classLoader, startMemory))
     }
 
     protected abstract fun getPlugin(pluginClassLoader: ClassLoader, scriptHandler: ScriptHandler): Plugin<Project>

libraries/tools/kotlin-gradle-plugin/src/test/kotlin/org/jetbrains/kotlin/gradle/BasicKotlinGradlePluginIT.kt

@@ -1,9 +1,7 @@
 package org.jetbrains.kotlin.gradle
 
-import org.junit.Test
-import org.jetbrains.kotlin.gradle.BaseGradleIT.Project
 import org.gradle.api.logging.LogLevel
-import org.junit.Ignore
+import org.junit.Test
 
 class SimpleKotlinGradleIT : BaseGradleIT() {
 

libraries/tools/kotlin-gradle-plugin/src/test/kotlin/org/jetbrains/kotlin/gradle/KotlinGradlePluginIT.kt

@@ -1,6 +1,7 @@
 package org.jetbrains.kotlin.gradle
 
-import org.jetbrains.kotlin.gradle.BaseGradleIT.Project
+import org.gradle.api.logging.LogLevel
+import org.jetbrains.kotlin.gradle.plugin.CleanUpBuildListener
 import org.junit.Test
 
 class KotlinGradleIT: BaseGradleIT() {
@@ -81,6 +82,19 @@ class KotlinGradleIT: BaseGradleIT() {
         }
     }
 
+    @Test
+    fun testLogLevelForceGC() {
+        val debugProject = Project("simpleProject", "1.12", minLogLevel = LogLevel.DEBUG)
+        debugProject.build("build") {
+            assertContains(CleanUpBuildListener.FORCE_SYSTEM_GC_MESSAGE)
+        }
+
+        val infoProject = Project("simpleProject", "1.12", minLogLevel = LogLevel.INFO)
+        infoProject.build("clean", "build") {
+            assertNotContains(CleanUpBuildListener.FORCE_SYSTEM_GC_MESSAGE)
+        }
+    }
+
     @Test
     fun testKotlinClasspath() {
         Project("classpathTest", "1.6").build("build") {