Add JFR ClassLoadingStatistics support

Signed-off-by: Gengchen Tuo <gengchen.tuo@ibm.com>

runtime/oti/j9consts.h

@@ -942,6 +942,7 @@ extern "C" {
 #define J9JFR_EVENT_TYPE_OBJECT_WAIT 4
 #define J9JFR_EVENT_TYPE_CPU_LOAD 5
 #define J9JFR_EVENT_TYPE_THREAD_CPU_LOAD 6
+#define J9JFR_EVENT_TYPE_CLASS_LOADING_STATISTICS 7
 
 /* JFR thread states */
 

runtime/oti/j9nonbuilder.h

@@ -434,6 +434,12 @@ typedef struct J9JFRThreadCPULoad {
 	float system;
 } J9JFRThreadCPULoad;
 
+typedef struct J9JFRClassLoadingStatistics {
+	J9JFR_EVENT_COMMON_FIELDS
+	I_64 loadedClassCount;
+	I_64 unloadedClassCount;
+} J9JFRClassLoadingStatistics;
+
 #endif /* defined(J9VM_OPT_JFR) */
 
 /* @ddr_namespace: map_to_type=J9CfrError */
@@ -3601,6 +3607,9 @@ typedef struct J9ClassLoader {
 	omrthread_rwmutex_t cpEntriesMutex;
 	UDATA initClassPathEntryCount;
 	UDATA asyncGetCallTraceUsed;
+#if defined(J9VM_OPT_JFR)
+	UDATA loadedClassCount;
+#endif /* defined(J9VM_OPT_JFR) */
 } J9ClassLoader;
 
 #define J9CLASSLOADER_SHARED_CLASSES_ENABLED  8

runtime/vm/JFRChunkWriter.hpp

@@ -74,6 +74,7 @@ enum MetadataTypeID {
 	CPUInformationID = 92,
 	CPULoadID = 94,
 	ThreadCPULoadID = 95,
+	ClassLoadingStatisticsID = 99,
 	PhysicalMemoryID = 107,
 	ExecutionSampleID = 108,
 	ThreadID = 163,
@@ -164,6 +165,7 @@ class VM_JFRChunkWriter {
 	static constexpr int CPU_LOAD_EVENT_SIZE = (3 * sizeof(float)) + (3 * sizeof(I_64));
 	static constexpr int THREAD_CPU_LOAD_EVENT_SIZE = (2 * sizeof(float)) + (4 * sizeof(I_64));
 	static constexpr int INITIAL_ENVIRONMENT_VARIABLE_EVENT_SIZE = 6000;
+	static constexpr int CLASS_LOADING_STATISTICS_EVENT_SIZE = 5 * sizeof(I_64);
 
 	static constexpr int METADATA_ID = 1;
 
@@ -339,6 +341,8 @@ class VM_JFRChunkWriter {
 
 			pool_do(_constantPoolTypes.getThreadCPULoadTable(), &writeThreadCPULoadEvent, _bufferWriter);
 
+			pool_do(_constantPoolTypes.getClassLoadingStatisticsTable(), &writeClassLoadingStatisticsEvent, _bufferWriter);
+
 			/* Only write constant events in first chunk */
 			if (0 == _vm->jfrState.jfrChunkCount) {
 				writeJVMInformationEvent();
@@ -600,6 +604,31 @@ class VM_JFRChunkWriter {
 		_bufferWriter->writeLEB128PaddedU32(dataStart, _bufferWriter->getCursor() - dataStart);
 	}
 
+	static void
+	writeClassLoadingStatisticsEvent(void *anElement, void *userData)
+	{
+		ClassLoadingStatisticsEntry *entry = (ClassLoadingStatisticsEntry  *)anElement;
+		VM_BufferWriter *_bufferWriter = (VM_BufferWriter *)userData;
+
+		/* reserve size field */
+		U_8 *dataStart = _bufferWriter->getAndIncCursor(sizeof(U_32));
+
+		/* write event type */
+		_bufferWriter->writeLEB128(ClassLoadingStatisticsID);
+
+		/* write start time */
+		_bufferWriter->writeLEB128(entry->ticks);
+
+		/* write user loaded class count */
+		_bufferWriter->writeFloat(entry->loadedClassCount);
+
+		/* write system unloaded class count */
+		_bufferWriter->writeFloat(entry->unloadedClassCount);
+
+		/* write size */
+		_bufferWriter->writeLEB128PaddedU32(dataStart, _bufferWriter->getCursor() - dataStart);
+	}
+
 	void
 	writeJFRChunkToFile()
 	{
@@ -728,6 +757,8 @@ class VM_JFRChunkWriter {
 
 		requiredBufferSize += _constantPoolTypes.getThreadCPULoadCount() * THREAD_CPU_LOAD_EVENT_SIZE;
 
+		requiredBufferSize += _constantPoolTypes.getClassLoadingStatisticsCount() * CLASS_LOADING_STATISTICS_EVENT_SIZE;
+
 		return requiredBufferSize;
 	}
 

runtime/vm/JFRConstantPoolTypes.cpp

@@ -1145,6 +1145,28 @@ VM_JFRConstantPoolTypes::addThreadCPULoadEntry(J9JFRThreadCPULoad *threadCPULoad
 	return index;
 }
 
+U_32
+VM_JFRConstantPoolTypes::addClassLoadingStatisticsEntry(J9JFRClassLoadingStatistics *classLoadingStatisticsData)
+{
+	ClassLoadingStatisticsEntry *entry = (ClassLoadingStatisticsEntry *)pool_newElement(_classLoadingStatisticsTable);
+	U_32 index = U_32_MAX;
+
+	if (NULL == entry) {
+		_buildResult = OutOfMemory;
+		goto done;
+	}
+
+	entry->ticks = classLoadingStatisticsData->startTicks;
+	entry->loadedClassCount = classLoadingStatisticsData->loadedClassCount;
+	entry->unloadedClassCount = classLoadingStatisticsData->unloadedClassCount;
+
+	index = _classLoadingStatisticsCount;
+	_classLoadingStatisticsCount += 1;
+
+done:
+	return index;
+}
+
 void
 VM_JFRConstantPoolTypes::printTables()
 {

runtime/vm/JFRConstantPoolTypes.hpp

@@ -227,6 +227,12 @@ struct ThreadCPULoadEntry {
 	float system;
 };
 
+struct ClassLoadingStatisticsEntry {
+	I_64 ticks;
+	I_64 loadedClassCount;
+	I_64 unloadedClassCount;
+};
+
 struct JVMInformationEntry {
 	const char *jvmName;
 	const char *jvmVersion;
@@ -308,6 +314,8 @@ class VM_JFRConstantPoolTypes {
 	UDATA _cpuLoadCount;
 	J9Pool *_threadCPULoadTable;
 	UDATA _threadCPULoadCount;
+	J9Pool *_classLoadingStatisticsTable;
+	UDATA _classLoadingStatisticsCount;
 
 	/* Processing buffers */
 	StackFrame *_currentStackFrameBuffer;
@@ -560,6 +568,8 @@ class VM_JFRConstantPoolTypes {
 
 	U_32 addThreadCPULoadEntry(J9JFRThreadCPULoad *threadCPULoadData);
 
+	U_32 addClassLoadingStatisticsEntry(J9JFRClassLoadingStatistics *classLoadingStatisticsData);
+
 	J9Pool *getExecutionSampleTable()
 	{
 		return _executionSampleTable;
@@ -595,6 +605,11 @@ class VM_JFRConstantPoolTypes {
 		return _threadCPULoadTable;
 	}
 
+	J9Pool *getClassLoadingStatisticsTable()
+	{
+		return _classLoadingStatisticsTable;
+	}
+
 	UDATA getExecutionSampleCount()
 	{
 		return _executionSampleCount;
@@ -630,6 +645,11 @@ class VM_JFRConstantPoolTypes {
 		return _threadCPULoadCount;
 	}
 
+	UDATA getClassLoadingStatisticsCount()
+	{
+		return _classLoadingStatisticsCount;
+	}
+
 	ClassloaderEntry *getClassloaderEntry()
 	{
 		return _firstClassloaderEntry;
@@ -779,6 +799,9 @@ class VM_JFRConstantPoolTypes {
 			case J9JFR_EVENT_TYPE_THREAD_CPU_LOAD:
 				addThreadCPULoadEntry((J9JFRThreadCPULoad *)event);
 				break;
+			case J9JFR_EVENT_TYPE_CLASS_LOADING_STATISTICS:
+				addClassLoadingStatisticsEntry((J9JFRClassLoadingStatistics *)event);
+				break;
 			default:
 				Assert_VM_unreachable();
 				break;
@@ -1102,6 +1125,8 @@ class VM_JFRConstantPoolTypes {
 		, _cpuLoadCount(0)
 		, _threadCPULoadTable(NULL)
 		, _threadCPULoadCount(0)
+		, _classLoadingStatisticsTable(NULL)
+		, _classLoadingStatisticsCount(0)
 		, _previousStackTraceEntry(NULL)
 		, _firstStackTraceEntry(NULL)
 		, _previousThreadEntry(NULL)
@@ -1216,6 +1241,12 @@ class VM_JFRConstantPoolTypes {
 			goto done;
 		}
 
+		_classLoadingStatisticsTable = pool_new(sizeof(ClassLoadingStatisticsEntry), 0, sizeof(U_64), 0, J9_GET_CALLSITE(), OMRMEM_CATEGORY_VM, POOL_FOR_PORT(privatePortLibrary));
+		if (NULL == _classLoadingStatisticsTable ) {
+			_buildResult = OutOfMemory;
+			goto done;
+		}
+
 		/* Add reserved index for default entries. For strings zero is the empty or NUll string.
 		 * For package zero is the deafult package, for Module zero is the unnamed module. ThreadGroup
 		 * zero is NULL threadGroup.
@@ -1303,6 +1334,7 @@ class VM_JFRConstantPoolTypes {
 		pool_kill(_monitorWaitTable);
 		pool_kill(_cpuLoadTable);
 		pool_kill(_threadCPULoadTable);
+		pool_kill(_classLoadingStatisticsTable);
 		j9mem_free_memory(_globalStringTable);
 	}
 

runtime/vm/classallocation.c

@@ -169,6 +169,11 @@ allocateClassLoader(J9JavaVM *javaVM)
 		classLoader->moduleHashTable = hashModuleNameTableNew(javaVM, INITIAL_MODULE_HASHTABLE_SIZE);
 		classLoader->packageHashTable = hashPackageTableNew(javaVM, INITIAL_PACKAGE_HASHTABLE_SIZE);
 #endif /* JAVA_SPEC_VERSION > 8 */
+
+#if defined(J9VM_OPT_JFR)
+		classLoader->loadedClassCount = 0;
+#endif /* defined(J9VM_OPT_JFR) */
+
 		/* Allocate classLocationHashTable only for bootloader which is the first classloader to be allocated.
 		 * The classLoader being allocated must be the bootloader if javaVM->systemClassLoader is NULL.
 		 */

runtime/vm/createramclass.cpp

@@ -2163,6 +2163,10 @@ internalCreateRAMClassDone(J9VMThread *vmThread, J9ClassLoader *classLoader, J9C
 			javaVM->anonClassCount += 1;
 		}
 
+#if defined(J9VM_OPT_JFR)
+		hostClassLoader->loadedClassCount += 1;
+#endif /* defined(J9VM_OPT_JFR) */
+
 		/* Create all the method IDs if class load is hooked */
 		if (J9_EVENT_IS_HOOKED(javaVM->hookInterface, J9HOOK_VM_CLASS_LOAD)) {
 			U_32 count = romClass->romMethodCount;

runtime/vm/jfr.cpp

@@ -22,6 +22,7 @@
 #include "JFRConstantPoolTypes.hpp"
 #include "j9protos.h"
 #include "omrlinkedlist.h"
+#include "pool_api.h"
 #include "thread_api.h"
 #include "ut_j9vm.h"
 #include "vm_internal.h"
@@ -92,6 +93,9 @@ jfrEventSize(J9JFREvent *jfrEvent)
 	case J9JFR_EVENT_TYPE_THREAD_CPU_LOAD:
 		size = sizeof(J9JFRThreadCPULoad);
 		break;
+	case J9JFR_EVENT_TYPE_CLASS_LOADING_STATISTICS:
+		size = sizeof(J9JFRClassLoadingStatistics);
+		break;
 	default:
 		Assert_VM_unreachable();
 		break;
@@ -939,6 +943,36 @@ jfrThreadCPULoadCallback(J9VMThread *currentThread, IDATA handlerKey, void *user
 	jfrThreadCPULoad(currentThread, currentThread);
 }
 
+void
+jfrClassLoadingStatistics(J9VMThread *currentThread)
+{
+	J9JavaVM *vm = currentThread->javaVM;
+	J9InternalVMFunctions *vmFuncs = vm->internalVMFunctions;
+	J9JFRClassLoadingStatistics *jfrEvent = (J9JFRClassLoadingStatistics *)reserveBuffer(currentThread, sizeof(J9JFRClassLoadingStatistics));
+
+	if (NULL != jfrEvent) {
+		initializeEventFields(currentThread, (J9JFREvent *)jfrEvent, J9JFR_EVENT_TYPE_CLASS_LOADING_STATISTICS);
+
+		UDATA unloadedClassCount = 0;
+		vm->memoryManagerFunctions->j9gc_get_cumulative_class_unloading_stats(currentThread, NULL, &unloadedClassCount, NULL);
+		jfrEvent->unloadedClassCount = (I_64)unloadedClassCount;
+
+		internalReleaseVMAccess(currentThread);
+
+		J9ClassLoaderWalkState walkState = {0};
+		J9ClassLoader *classLoader = vmFuncs->allClassLoadersStartDo(&walkState, vm, 0);
+
+		while (NULL != classLoader) {
+			jfrEvent->loadedClassCount += classLoader->loadedClassCount;
+
+			classLoader= vmFuncs->allClassLoadersNextDo(&walkState);
+		}
+		vmFuncs->allClassLoadersEndDo(&walkState);
+
+		internalAcquireVMAccess(currentThread);
+	}
+}
+
 static int J9THREAD_PROC
 jfrSamplingThreadProc(void *entryArg)
 {
@@ -956,6 +990,7 @@ jfrSamplingThreadProc(void *entryArg)
 				omrthread_monitor_exit(vm->jfrSamplerMutex);
 				internalAcquireVMAccess(currentThread);
 				jfrCPULoad(currentThread);
+				jfrClassLoadingStatistics(currentThread);
 				internalReleaseVMAccess(currentThread);
 				omrthread_monitor_enter(vm->jfrSamplerMutex);
 				if (0 == (count % 1000)) { // 10 seconds