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MetronomeDelegate.cpp
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/*******************************************************************************
* Copyright (c) 2019, 2019 IBM Corp. and others
*
* This program and the accompanying materials are made available under
* the terms of the Eclipse Public License 2.0 which accompanies this
* distribution and is available at https://www.eclipse.org/legal/epl-2.0/
* or the Apache License, Version 2.0 which accompanies this distribution and
* is available at https://www.apache.org/licenses/LICENSE-2.0.
*
* This Source Code may also be made available under the following
* Secondary Licenses when the conditions for such availability set
* forth in the Eclipse Public License, v. 2.0 are satisfied: GNU
* General Public License, version 2 with the GNU Classpath
* Exception [1] and GNU General Public License, version 2 with the
* OpenJDK Assembly Exception [2].
*
* [1] https://www.gnu.org/software/classpath/license.html
* [2] http://openjdk.java.net/legal/assembly-exception.html
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
*******************************************************************************/
#include "MetronomeDelegate.hpp"
#if defined(J9VM_GC_REALTIME)
#include "omr.h"
#include "ClassHeapIterator.hpp"
#include "ClassLoaderIterator.hpp"
#include "ClassLoaderLinkedListIterator.hpp"
#include "ClassLoaderManager.hpp"
#include "ClassLoaderSegmentIterator.hpp"
#include "EnvironmentRealtime.hpp"
#include "FinalizableClassLoaderBuffer.hpp"
#include "FinalizableObjectBuffer.hpp"
#include "FinalizableReferenceBuffer.hpp"
#include "FinalizeListManager.hpp"
#include "FinalizerSupport.hpp"
#include "GCExtensionsBase.hpp"
#include "Heap.hpp"
#include "HeapRegionDescriptorRealtime.hpp"
#include "MetronomeAlarmThread.hpp"
#include "JNICriticalRegion.hpp"
#include "OwnableSynchronizerObjectBufferRealtime.hpp"
#include "OwnableSynchronizerObjectList.hpp"
#include "RealtimeAccessBarrier.hpp"
#include "RealtimeGC.hpp"
#include "RealtimeMarkingScheme.hpp"
#include "RealtimeMarkingSchemeRootMarker.hpp"
#include "RealtimeMarkingSchemeRootClearer.hpp"
#include "RealtimeMarkTask.hpp"
#include "RealtimeRootScanner.hpp"
#include "ReferenceObjectBufferRealtime.hpp"
#include "ReferenceObjectList.hpp"
#include "Scheduler.hpp"
#include "UnfinalizedObjectBufferRealtime.hpp"
#include "UnfinalizedObjectList.hpp"
void
MM_MetronomeDelegate::yieldWhenRequested(MM_EnvironmentBase *env)
{
MM_GCExtensionsBase *ext = env->getExtensions();
UDATA accessMask;
MM_Scheduler *sched = (MM_Scheduler *)ext->dispatcher;
if (sched->_mode != MM_Scheduler::MUTATOR) {
MM_JNICriticalRegion::releaseAccess((J9VMThread *)env->getOmrVMThread()->_language_vmthread, &accessMask);
while (sched->_mode != MM_Scheduler::MUTATOR) {
omrthread_sleep(10);
}
MM_JNICriticalRegion::reacquireAccess((J9VMThread *)env->getOmrVMThread()->_language_vmthread, accessMask);
}
}
/**
* C entrypoint for the newly created alarm thread.
*/
int J9THREAD_PROC
MM_MetronomeDelegate::metronomeAlarmThreadWrapper(void* userData)
{
MM_MetronomeAlarmThread *alarmThread = (MM_MetronomeAlarmThread *)userData;
J9JavaVM *javaVM = (J9JavaVM *)alarmThread->getScheduler()->_extensions->getOmrVM()->_language_vm;
PORT_ACCESS_FROM_JAVAVM(javaVM);
uintptr_t rc;
j9sig_protect(MM_MetronomeDelegate::signalProtectedFunction, (void*)userData,
javaVM->internalVMFunctions->structuredSignalHandlerVM, javaVM,
J9PORT_SIG_FLAG_SIGALLSYNC | J9PORT_SIG_FLAG_MAY_CONTINUE_EXECUTION,
&rc);
omrthread_monitor_enter(alarmThread->_mutex);
alarmThread->_alarmThreadActive = MM_MetronomeAlarmThread::ALARM_THREAD_SHUTDOWN;
omrthread_monitor_notify(alarmThread->_mutex);
omrthread_exit(alarmThread->_mutex);
return 0;
}
uintptr_t
MM_MetronomeDelegate::signalProtectedFunction(J9PortLibrary *privatePortLibrary, void* userData)
{
MM_MetronomeAlarmThread *alarmThread = (MM_MetronomeAlarmThread *)userData;
J9JavaVM *javaVM = (J9JavaVM *)alarmThread->getScheduler()->_extensions->getOmrVM()->_language_vm;
J9VMThread *vmThread = NULL;
MM_EnvironmentRealtime *env = NULL;
if (JNI_OK != (javaVM->internalVMFunctions->attachSystemDaemonThread(javaVM, &vmThread, "GC Alarm"))) {
return 0;
}
env = MM_EnvironmentRealtime::getEnvironment(vmThread->omrVMThread);
alarmThread->run(env);
javaVM->internalVMFunctions->DetachCurrentThread((JavaVM*)javaVM);
return 0;
}
void
MM_MetronomeDelegate::clearGCStats()
{
_extensions->markJavaStats.clear();
}
void
MM_MetronomeDelegate::clearGCStatsEnvironment(MM_EnvironmentRealtime *env)
{
env->_markStats.clear();
env->getGCEnvironment()->_markJavaStats.clear();
env->_workPacketStats.clear();
}
void
MM_MetronomeDelegate::mergeGCStats(MM_EnvironmentRealtime *env)
{
GC_Environment *gcEnv = env->getGCEnvironment();
MM_GlobalGCStats *finalGCStats= &_extensions->globalGCStats;
finalGCStats->markStats.merge(&env->_markStats);
_extensions->markJavaStats.merge(&gcEnv->_markJavaStats);
finalGCStats->workPacketStats.merge(&env->_workPacketStats);
}
uintptr_t
MM_MetronomeDelegate::getSplitArraysProcessed(MM_EnvironmentRealtime *env)
{
GC_Environment *gcEnv = env->getGCEnvironment();
return gcEnv->_markJavaStats.splitArraysProcessed;
}
bool
MM_MetronomeDelegate::initialize(MM_EnvironmentBase *env)
{
_scheduler = _realtimeGC->_sched;
_markingScheme = _realtimeGC->getMarkingScheme();
#if defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING)
_unmarkedImpliesClasses = false;
#endif /* defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING) */
_unmarkedImpliesCleared = false;
_unmarkedImpliesStringsCleared = false;
/* allocate and initialize the global reference object lists */
if (!allocateAndInitializeReferenceObjectLists(env)){
return false;
}
/* allocate and initialize the global unfinalized object lists */
if (!allocateAndInitializeUnfinalizedObjectLists(env)) {
return false;
}
/* allocate and initialize the global ownable synchronizer object lists */
if (!allocateAndInitializeOwnableSynchronizerObjectLists(env)) {
return false;
}
J9JavaVM *javaVM = (J9JavaVM *)env->getLanguageVM();
javaVM->extendedRuntimeFlags |= J9_EXTENDED_RUNTIME_USER_REALTIME_ACCESS_BARRIER;
#if defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING)
if (!_extensions->dynamicClassUnloadingThresholdForced) {
_extensions->dynamicClassUnloadingThreshold = 1;
}
if (!_extensions->dynamicClassUnloadingKickoffThresholdForced) {
_extensions->dynamicClassUnloadingKickoffThreshold = 0;
}
#endif /* defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING) */
/* Create the appropriate access barrier for Metronome */
MM_RealtimeAccessBarrier *accessBarrier = NULL;
accessBarrier = allocateAccessBarrier(env);
if (NULL == accessBarrier) {
return false;
}
MM_GCExtensions::getExtensions(_javaVM)->accessBarrier = (MM_ObjectAccessBarrier *)accessBarrier;
_javaVM->realtimeHeapMapBasePageRounded = _markingScheme->_markMap->getHeapMapBaseRegionRounded();
_javaVM->realtimeHeapMapBits = _markingScheme->_markMap->getHeapMapBits();
return true;
}
bool
MM_MetronomeDelegate::allocateAndInitializeReferenceObjectLists(MM_EnvironmentBase *env)
{
const UDATA listCount = getReferenceObjectListCount(env);
Assert_MM_true(0 < listCount);
_extensions->referenceObjectLists = (MM_ReferenceObjectList *)env->getForge()->allocate((sizeof(MM_ReferenceObjectList) * listCount), MM_AllocationCategory::FIXED, J9_GET_CALLSITE());
if (NULL == _extensions->referenceObjectLists) {
return false;
}
for (UDATA index = 0; index < listCount; index++) {
new(&_extensions->referenceObjectLists[index]) MM_ReferenceObjectList();
}
return true;
}
bool
MM_MetronomeDelegate::allocateAndInitializeUnfinalizedObjectLists(MM_EnvironmentBase *env)
{
const UDATA listCount = getUnfinalizedObjectListCount(env);
Assert_MM_true(0 < listCount);
MM_UnfinalizedObjectList *unfinalizedObjectLists = (MM_UnfinalizedObjectList *)env->getForge()->allocate((sizeof(MM_UnfinalizedObjectList) * listCount), MM_AllocationCategory::FIXED, J9_GET_CALLSITE());
if (NULL == unfinalizedObjectLists) {
return false;
}
for (UDATA index = 0; index < listCount; index++) {
new(&unfinalizedObjectLists[index]) MM_UnfinalizedObjectList();
/* add each list to the global list. we need to maintain the doubly linked list
* to ensure uniformity with SE/Balanced.
*/
MM_UnfinalizedObjectList *previousUnfinalizedObjectList = (0 == index) ? NULL : &unfinalizedObjectLists[index-1];
MM_UnfinalizedObjectList *nextUnfinalizedObjectList = ((listCount - 1) == index) ? NULL : &unfinalizedObjectLists[index+1];
unfinalizedObjectLists[index].setNextList(nextUnfinalizedObjectList);
unfinalizedObjectLists[index].setPreviousList(previousUnfinalizedObjectList);
}
_extensions->unfinalizedObjectLists = unfinalizedObjectLists;
return true;
}
bool
MM_MetronomeDelegate::allocateAndInitializeOwnableSynchronizerObjectLists(MM_EnvironmentBase *env)
{
const UDATA listCount = getOwnableSynchronizerObjectListCount(env);
Assert_MM_true(0 < listCount);
MM_OwnableSynchronizerObjectList *ownableSynchronizerObjectLists = (MM_OwnableSynchronizerObjectList *)env->getForge()->allocate((sizeof(MM_OwnableSynchronizerObjectList) * listCount), MM_AllocationCategory::FIXED, J9_GET_CALLSITE());
if (NULL == ownableSynchronizerObjectLists) {
return false;
}
for (UDATA index = 0; index < listCount; index++) {
new(&ownableSynchronizerObjectLists[index]) MM_OwnableSynchronizerObjectList();
/* add each list to the global list. we need to maintain the doubly linked list
* to ensure uniformity with SE/Balanced.
*/
MM_OwnableSynchronizerObjectList *previousOwnableSynchronizerObjectList = (0 == index) ? NULL : &ownableSynchronizerObjectLists[index-1];
MM_OwnableSynchronizerObjectList *nextOwnableSynchronizerObjectList = ((listCount - 1) == index) ? NULL : &ownableSynchronizerObjectLists[index+1];
ownableSynchronizerObjectLists[index].setNextList(nextOwnableSynchronizerObjectList);
ownableSynchronizerObjectLists[index].setPreviousList(previousOwnableSynchronizerObjectList);
}
_extensions->ownableSynchronizerObjectLists = ownableSynchronizerObjectLists;
return true;
}
void
MM_MetronomeDelegate::tearDown(MM_EnvironmentBase *env)
{
if (NULL != _extensions->referenceObjectLists) {
env->getForge()->free(_extensions->referenceObjectLists);
_extensions->referenceObjectLists = NULL;
}
if (NULL != _extensions->unfinalizedObjectLists) {
env->getForge()->free(_extensions->unfinalizedObjectLists);
_extensions->unfinalizedObjectLists = NULL;
}
if (NULL != _extensions->ownableSynchronizerObjectLists) {
env->getForge()->free(_extensions->ownableSynchronizerObjectLists);
_extensions->ownableSynchronizerObjectLists = NULL;
}
if (NULL != _extensions->accessBarrier) {
_extensions->accessBarrier->kill(env);
_extensions->accessBarrier = NULL;
}
_javaVM->realtimeHeapMapBits = NULL;
}
void
MM_MetronomeDelegate::masterSetupForGC(MM_EnvironmentBase *env)
{
#if defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING)
/* Set the dynamic class unloading flag based on command line and runtime state */
switch (_extensions->dynamicClassUnloading) {
case MM_GCExtensions::DYNAMIC_CLASS_UNLOADING_NEVER:
_extensions->runtimeCheckDynamicClassUnloading = false;
break;
case MM_GCExtensions::DYNAMIC_CLASS_UNLOADING_ALWAYS:
_extensions->runtimeCheckDynamicClassUnloading = true;
break;
case MM_GCExtensions::DYNAMIC_CLASS_UNLOADING_ON_CLASS_LOADER_CHANGES:
_extensions->runtimeCheckDynamicClassUnloading = (_extensions->aggressive || _extensions->classLoaderManager->isTimeForClassUnloading(env));
break;
default:
break;
}
#endif /* J9VM_GC_DYNAMIC_CLASS_UNLOADING */
#if defined(J9VM_GC_FINALIZATION)
_finalizationRequired = false;
#endif /* J9VM_GC_FINALIZATION */
}
void
MM_MetronomeDelegate::masterCleanupAfterGC(MM_EnvironmentBase *env)
{
#if defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING)
/* flush the dead class segments if their size exceeds the CacheSize mark.
* Heap fixup should have been completed in this cycle.
*/
if (_extensions->classLoaderManager->reclaimableMemory() > _extensions->deadClassLoaderCacheSize) {
Trc_MM_FlushUndeadSegments_Entry(env->getLanguageVMThread(), "Non-zero reclaimable memory available");
_extensions->classLoaderManager->flushUndeadSegments(env);
Trc_MM_FlushUndeadSegments_Exit(env->getLanguageVMThread());
}
#endif /* defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING) */
}
void
MM_MetronomeDelegate::incrementalCollectStart(MM_EnvironmentRealtime *env)
{
#if defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING)
_dynamicClassUnloadingEnabled = ((_extensions->runtimeCheckDynamicClassUnloading != 0) ? true : false);
#endif /* defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING) */
}
void
MM_MetronomeDelegate::incrementalCollect(MM_EnvironmentRealtime *env)
{
#if defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING)
PORT_ACCESS_FROM_ENVIRONMENT(env);
_dynamicClassUnloadingEnabled = ((_extensions->runtimeCheckDynamicClassUnloading != 0) ? true : false);
if (_extensions->runtimeCheckDynamicClassUnloading != 0) {
MM_ClassUnloadStats *classUnloadStats = &_extensions->globalGCStats.classUnloadStats;
_realtimeGC->setCollectorUnloadingClassLoaders();
reportClassUnloadingStart(env);
classUnloadStats->_startTime = j9time_hires_clock();
unloadDeadClassLoaders(env);
classUnloadStats->_endTime = j9time_hires_clock();
reportClassUnloadingEnd(env);
/* If there was dynamic class unloading checks during the run, record the new number of class
* loaders last seen during a DCU pass
*/
_extensions->classLoaderManager->setLastUnloadNumOfClassLoaders();
_extensions->classLoaderManager->setLastUnloadNumOfAnonymousClasses();
}
/* Handling of classes done. Return back to "mark if necessary" mode */
_unmarkedImpliesClasses = false;
/* Clear the appropriate flags of all classLoaders */
GC_ClassLoaderIterator classLoaderIterator(_javaVM->classLoaderBlocks);
J9ClassLoader *classLoader;
while((classLoader = classLoaderIterator.nextSlot()) != NULL) {
classLoader->gcFlags &= ~J9_GC_CLASS_LOADER_SCANNED;
}
#endif /* J9VM_GC_DYNAMIC_CLASS_UNLOADING */
/* If the J9VM_DEBUG_ATTRIBUTE_ALLOW_USER_HEAP_WALK flag is set,
* or if we are about to unload classes and free class memory segments
* then fix the heap so that it can be walked by debugging tools
*/
#if defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING)
bool fixupForClassUnload = (_extensions->classLoaderManager->reclaimableMemory() > _extensions->deadClassLoaderCacheSize);
#else /* defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING) */
bool fixupForClassUnload = false;
#endif /* defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING) */
if (J9VM_DEBUG_ATTRIBUTE_ALLOW_USER_HEAP_WALK == (((J9JavaVM *)env->getLanguageVM())->requiredDebugAttributes & J9VM_DEBUG_ATTRIBUTE_ALLOW_USER_HEAP_WALK)
|| fixupForClassUnload) {
_realtimeGC->_fixHeapForWalk = true;
}
}
void
MM_MetronomeDelegate::doAuxiliaryGCWork(MM_EnvironmentBase *env)
{
#if defined(J9VM_GC_FINALIZATION)
if(isFinalizationRequired()) {
omrthread_monitor_enter(_javaVM->finalizeMasterMonitor);
_javaVM->finalizeMasterFlags |= J9_FINALIZE_FLAGS_MASTER_WAKE_UP;
omrthread_monitor_notify_all(_javaVM->finalizeMasterMonitor);
omrthread_monitor_exit(_javaVM->finalizeMasterMonitor);
}
#endif /* J9VM_GC_FINALIZATION */
}
#if defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING)
void
MM_MetronomeDelegate::processDyingClasses(MM_EnvironmentRealtime *env, UDATA* classUnloadCountResult, UDATA* anonymousClassUnloadCountResult, UDATA* classLoaderUnloadCountResult, J9ClassLoader** classLoaderUnloadListResult)
{
J9ClassLoader *classLoader = NULL;
J9VMThread *vmThread = (J9VMThread *)env->getLanguageVMThread();
UDATA classUnloadCount = 0;
UDATA anonymousClassUnloadCount = 0;
UDATA classLoaderUnloadCount = 0;
J9ClassLoader *unloadLink = NULL;
J9Class *classUnloadList = NULL;
J9Class *anonymousClassUnloadList = NULL;
/*
* Walk anonymous classes and set unmarked as dying
*
* Do this walk before classloaders to be unloaded walk to create list of anonymous classes to be unloaded and use it
* as sublist to continue to build general list of classes to be unloaded
*
* Anonymous classes suppose to be allocated one per segment
* This is not relevant here however becomes important at segment removal time
*/
anonymousClassUnloadList = addDyingClassesToList(env, _javaVM->anonClassLoader, false, anonymousClassUnloadList, &anonymousClassUnloadCount);
/* class unload list includes anonymous class unload list */
classUnloadList = anonymousClassUnloadList;
classUnloadCount += anonymousClassUnloadCount;
GC_ClassLoaderLinkedListIterator classLoaderIterator(env, _extensions->classLoaderManager);
while(NULL != (classLoader = (J9ClassLoader *)classLoaderIterator.nextSlot())) {
if (0 == (classLoader->gcFlags & J9_GC_CLASS_LOADER_DEAD)) {
Assert_MM_true(NULL == classLoader->unloadLink);
if(_markingScheme->isMarked(classLoader->classLoaderObject) ) {
classLoader->gcFlags &= ~J9_GC_CLASS_LOADER_SCANNED;
} else {
/* Anonymous classloader should not be unloaded */
Assert_MM_true(0 == (classLoader->flags & J9CLASSLOADER_ANON_CLASS_LOADER));
classLoaderUnloadCount += 1;
classLoader->gcFlags |= J9_GC_CLASS_LOADER_DEAD;
/* add this loader to the linked list of loaders being unloaded in this cycle */
classLoader->unloadLink = unloadLink;
unloadLink = classLoader;
classUnloadList = addDyingClassesToList(env, classLoader, true, classUnloadList, &classUnloadCount);
}
}
yieldFromClassUnloading(env);
}
if (0 != classUnloadCount) {
/* Call classes unload hook */
TRIGGER_J9HOOK_VM_CLASSES_UNLOAD(_javaVM->hookInterface, vmThread, classUnloadCount, classUnloadList);
yieldFromClassUnloading(env);
}
if (0 != anonymousClassUnloadCount) {
/* Call anonymous classes unload hook */
TRIGGER_J9HOOK_VM_ANON_CLASSES_UNLOAD(_javaVM->hookInterface, vmThread, anonymousClassUnloadCount, anonymousClassUnloadList);
yieldFromClassUnloading(env);
}
if (0 != classLoaderUnloadCount) {
/* Call classloader unload hook */
TRIGGER_J9HOOK_VM_CLASS_LOADERS_UNLOAD(_javaVM->hookInterface, vmThread, unloadLink);
yieldFromClassUnloading(env);
}
/* Ensure that the VM has an accurate anonymous class count */
_javaVM->anonClassCount -= anonymousClassUnloadCount;
*classUnloadCountResult = classUnloadCount;
*anonymousClassUnloadCountResult = anonymousClassUnloadCount;
*classLoaderUnloadCountResult = classLoaderUnloadCount;
*classLoaderUnloadListResult = unloadLink;
}
J9Class *
MM_MetronomeDelegate::addDyingClassesToList(MM_EnvironmentRealtime *env, J9ClassLoader * classLoader, bool setAll, J9Class *classUnloadListStart, UDATA *classUnloadCountResult)
{
J9VMThread *vmThread = (J9VMThread *)env->getLanguageVMThread();
J9Class *classUnloadList = classUnloadListStart;
UDATA classUnloadCount = 0;
if (NULL != classLoader) {
GC_ClassLoaderSegmentIterator segmentIterator(classLoader, MEMORY_TYPE_RAM_CLASS);
J9MemorySegment *segment = NULL;
while(NULL != (segment = segmentIterator.nextSegment())) {
GC_ClassHeapIterator classHeapIterator(_javaVM, segment);
J9Class *clazz = NULL;
while(NULL != (clazz = classHeapIterator.nextClass())) {
J9CLASS_EXTENDED_FLAGS_CLEAR(clazz, J9ClassGCScanned);
J9Object *classObject = clazz->classObject;
if (setAll || !_markingScheme->isMarked(classObject)) {
/* with setAll all classes must be unmarked */
Assert_MM_true(!_markingScheme->isMarked(classObject));
classUnloadCount += 1;
/* Remove the class from the subclass traversal list */
_extensions->classLoaderManager->removeFromSubclassHierarchy(env, clazz);
/* Mark class as dying */
clazz->classDepthAndFlags |= J9AccClassDying;
/* Call class unload hook */
Trc_MM_cleanUpClassLoadersStart_triggerClassUnload(env->getLanguageVMThread(),clazz,
(UDATA) J9UTF8_LENGTH(J9ROMCLASS_CLASSNAME(clazz->romClass)),
J9UTF8_DATA(J9ROMCLASS_CLASSNAME(clazz->romClass)));
TRIGGER_J9HOOK_VM_CLASS_UNLOAD(_javaVM->hookInterface, vmThread, clazz);
/* add class to dying anonymous classes link list */
clazz->gcLink = classUnloadList;
classUnloadList = clazz;
}
}
}
}
*classUnloadCountResult += classUnloadCount;
return classUnloadList;
}
/**
* Free classloaders which are being unloaded during this GC cycle. Also remove all
* dead classes from the traversal list.
* @note the traversal code belongs in its own function or possibly processDyingClasses
* or possible processDyingClasses. It is currently here for historic reasons.
*
* @param deadClassLoaders Linked list of classloaders dying during this GC cycle
*/
void
MM_MetronomeDelegate::processUnlinkedClassLoaders(MM_EnvironmentBase *envModron, J9ClassLoader *deadClassLoaders)
{
MM_EnvironmentRealtime *env = MM_EnvironmentRealtime::getEnvironment(envModron);
J9ClassLoader *unloadLink = deadClassLoaders;
J9VMThread *vmThread = (J9VMThread *)env->getLanguageVMThread();
J9JavaVM *javaVM = (J9JavaVM *)env->getLanguageVM();
/* Remove dead classes from the traversal list (if necessary) */
J9Class *jlObject = J9VMJAVALANGOBJECT_OR_NULL(javaVM);
J9Class *previousClass = jlObject;
J9Class *nextClass = (NULL != jlObject) ? jlObject->subclassTraversalLink : jlObject;
while ((NULL != nextClass) && (jlObject != nextClass)) {
if (J9CLASS_FLAGS(nextClass) & J9AccClassDying) {
while ((NULL != nextClass->subclassTraversalLink) && (jlObject != nextClass) && (J9CLASS_FLAGS(nextClass) & 0x08000000)) {
nextClass = nextClass->subclassTraversalLink;
}
previousClass->subclassTraversalLink = nextClass;
}
previousClass = nextClass;
nextClass = nextClass->subclassTraversalLink;
/* TODO CRGTMP Do we need to yield here? Is yielding safe? */
}
/* Free memory for dead classloaders */
while (NULL != unloadLink) {
J9ClassLoader *nextUnloadLink = unloadLink->unloadLink;
_javaVM->internalVMFunctions->freeClassLoader(unloadLink, _javaVM, vmThread, 1);
unloadLink = nextUnloadLink;
yieldFromClassUnloading(env);
}
}
void
MM_MetronomeDelegate::updateClassUnloadStats(MM_EnvironmentBase *env, UDATA classUnloadCount, UDATA anonymousClassUnloadCount, UDATA classLoaderUnloadCount)
{
MM_ClassUnloadStats *classUnloadStats = &_extensions->globalGCStats.classUnloadStats;
/* TODO CRGTMP move global stats into super class implementation once it is created */
classUnloadStats->_classesUnloadedCount = classUnloadCount;
classUnloadStats->_anonymousClassesUnloadedCount = anonymousClassUnloadCount;
classUnloadStats->_classLoaderUnloadedCount = classLoaderUnloadCount;
/* Record increment stats */
_extensions->globalGCStats.metronomeStats.classesUnloadedCount = classUnloadCount;
_extensions->globalGCStats.metronomeStats.anonymousClassesUnloadedCount = anonymousClassUnloadCount;
_extensions->globalGCStats.metronomeStats.classLoaderUnloadedCount = classLoaderUnloadCount;
}
/**
* Unload classcloaders that are no longer referenced. If the classloader has shared
* libraries open place it on the finalize queue instead of freeing it.
*
*/
void
MM_MetronomeDelegate::unloadDeadClassLoaders(MM_EnvironmentBase *envModron)
{
MM_EnvironmentRealtime *env = MM_EnvironmentRealtime::getEnvironment(envModron);
J9ClassLoader *unloadLink = NULL;
UDATA classUnloadCount = 0;
UDATA anonymousClassUnloadCount = 0;
UDATA classLoaderUnloadCount = 0;
J9ClassLoader *classLoadersUnloadedList = NULL;
J9MemorySegment *reclaimedSegments = NULL;
/* set the vmState whilst we're unloading classes */
UDATA vmState = env->pushVMstate(OMRVMSTATE_GC_CLEANING_METADATA);
lockClassUnloadMonitor(env);
processDyingClasses(env, &classUnloadCount, &anonymousClassUnloadCount, &classLoaderUnloadCount, &classLoadersUnloadedList);
/* cleanup segments in anonymous classloader */
_extensions->classLoaderManager->cleanUpSegmentsInAnonymousClassLoader(env, &reclaimedSegments);
/* enqueue all the segments we just salvaged from the dead class loaders for delayed free (this work was historically attributed in the unload end operation so it goes after the timer start) */
_extensions->classLoaderManager->enqueueUndeadClassSegments(reclaimedSegments);
yieldFromClassUnloading(env);
GC_FinalizableClassLoaderBuffer buffer(_extensions);
while (NULL != classLoadersUnloadedList) {
/* fetch the next loader immediately, since we will re-use the unloadLink in this loop */
J9ClassLoader* classLoader = classLoadersUnloadedList;
classLoadersUnloadedList = classLoader->unloadLink;
Assert_MM_true(0 == (classLoader->gcFlags & J9_GC_CLASS_LOADER_SCANNED));
Assert_MM_true(J9_GC_CLASS_LOADER_DEAD == (classLoader->gcFlags & J9_GC_CLASS_LOADER_DEAD));
Assert_MM_true(0 == (classLoader->gcFlags & (J9_GC_CLASS_LOADER_UNLOADING | J9_GC_CLASS_LOADER_ENQ_UNLOAD)));
/* Class loader died this collection, so do cleanup work */
reclaimedSegments = NULL;
/* Perform classLoader-specific clean up work, including freeing the classLoader's class hash table and
* class path entries.
*/
_javaVM->internalVMFunctions->cleanUpClassLoader((J9VMThread *)env->getLanguageVMThread(), classLoader);
/* free any ROM classes now and enqueue any RAM classes */
_extensions->classLoaderManager->cleanUpSegmentsAlongClassLoaderLink(_javaVM, classLoader->classSegments, &reclaimedSegments);
/* we are taking responsibility for cleaning these here so free them */
classLoader->classSegments = NULL;
/* enqueue all the segments we just salvaged from the dead class loaders for delayed free (this work was historically attributed in the unload end operation so it goes after the timer start) */
_extensions->classLoaderManager->enqueueUndeadClassSegments(reclaimedSegments);
/* Remove this classloader slot */
_extensions->classLoaderManager->unlinkClassLoader(classLoader);
#if defined(J9VM_GC_FINALIZATION)
/* Determine if the classLoader needs to be enqueued for finalization (for shared library unloading),
* otherwise add it to the list of classLoaders to be unloaded by cleanUpClassLoadersEnd.
*/
if(((NULL != classLoader->sharedLibraries)
&& (0 != pool_numElements(classLoader->sharedLibraries)))
|| (_extensions->fvtest_forceFinalizeClassLoaders)) {
/* Attempt to enqueue the class loader for the finalizer */
buffer.add(env, classLoader);
classLoader->gcFlags |= J9_GC_CLASS_LOADER_ENQ_UNLOAD;
_finalizationRequired = true;
} else
#endif /* J9VM_GC_FINALIZATION */
{
/* Add the classLoader to the list of classLoaders to unloaded by cleanUpClassLoadersEnd */
classLoader->unloadLink = unloadLink;
unloadLink = classLoader;
}
yieldFromClassUnloading(env);
}
buffer.flush(env);
updateClassUnloadStats(env, classUnloadCount, anonymousClassUnloadCount, classLoaderUnloadCount);
processUnlinkedClassLoaders(env, unloadLink);
unlockClassUnloadMonitor(env);
env->popVMstate(vmState);
}
/**
* Check to see if it is time to yield. If it is time to yield the GC
* must release the classUnloadMonitor before yielding. Once the GC
* comes back from the yield it is required to acquire the classUnloadMonitor
* again.
*/
void
MM_MetronomeDelegate::yieldFromClassUnloading(MM_EnvironmentRealtime *env)
{
if (_realtimeGC->shouldYield(env)) {
unlockClassUnloadMonitor(env);
_realtimeGC->yield(env);
lockClassUnloadMonitor(env);
}
}
/**
* The GC is required to hold the classUnloadMonitor while it is unloading classes.
* This will ensure that the JIT will abort and ongoing compilations
*/
void
MM_MetronomeDelegate::lockClassUnloadMonitor(MM_EnvironmentRealtime *env)
{
/* Grab the classUnloadMonitor so that the JIT and the GC will not interfere with each other */
#if defined(J9VM_JIT_CLASS_UNLOAD_RWMONITOR)
if (0 != omrthread_rwmutex_try_enter_write(_javaVM->classUnloadMutex)) {
#else
if (0 != omrthread_monitor_try_enter(_javaVM->classUnloadMutex)) {
#endif /* J9VM_JIT_CLASS_UNLOAD_RWMONITOR */
/* Failed acquire the monitor so interrupt the JIT. This will allow the GC
* to continue unloading classes.
*/
TRIGGER_J9HOOK_MM_INTERRUPT_COMPILATION(_extensions->hookInterface, (J9VMThread *)env->getLanguageVMThread());
#if defined(J9VM_JIT_CLASS_UNLOAD_RWMONITOR)
omrthread_rwmutex_enter_write(_javaVM->classUnloadMutex);
#else
omrthread_monitor_enter(_javaVM->classUnloadMutex);
#endif /* J9VM_JIT_CLASS_UNLOAD_RWMONITOR */
}
}
/**
* Release the classUnloadMonitor. This will allow the JIT to compile new methods.
*/
void
MM_MetronomeDelegate::unlockClassUnloadMonitor(MM_EnvironmentRealtime *env)
{
#if defined(J9VM_JIT_CLASS_UNLOAD_RWMONITOR)
omrthread_rwmutex_exit_write(_javaVM->classUnloadMutex);
#else
omrthread_monitor_exit(_javaVM->classUnloadMutex);
#endif /* J9VM_JIT_CLASS_UNLOAD_RWMONITOR */
}
void
MM_MetronomeDelegate::reportClassUnloadingStart(MM_EnvironmentBase *env)
{
PORT_ACCESS_FROM_ENVIRONMENT(env);
Trc_MM_ClassUnloadingStart(env->getLanguageVMThread());
TRIGGER_J9HOOK_MM_PRIVATE_CLASS_UNLOADING_START(
_extensions->privateHookInterface,
env->getOmrVMThread(),
j9time_hires_clock(),
J9HOOK_MM_PRIVATE_CLASS_UNLOADING_START);
}
void
MM_MetronomeDelegate::reportClassUnloadingEnd(MM_EnvironmentBase *env)
{
PORT_ACCESS_FROM_ENVIRONMENT(env);
MM_ClassUnloadStats *classUnloadStats = &_extensions->globalGCStats.classUnloadStats;
Trc_MM_ClassUnloadingEnd(env->getLanguageVMThread(),
classUnloadStats->_classLoaderUnloadedCount,
classUnloadStats->_classesUnloadedCount);
TRIGGER_J9HOOK_MM_CLASS_UNLOADING_END(
_extensions->hookInterface,
(J9VMThread *)env->getLanguageVMThread(),
j9time_hires_clock(),
J9HOOK_MM_CLASS_UNLOADING_END,
classUnloadStats->_endTime - classUnloadStats->_startTime,
classUnloadStats->_classLoaderUnloadedCount,
classUnloadStats->_classesUnloadedCount,
classUnloadStats->_classUnloadMutexQuiesceTime,
classUnloadStats->_endSetupTime - classUnloadStats->_startSetupTime,
classUnloadStats->_endScanTime - classUnloadStats->_startScanTime,
classUnloadStats->_endPostTime - classUnloadStats->_startPostTime);
}
#endif /* J9VM_GC_DYNAMIC_CLASS_UNLOADING */
void
MM_MetronomeDelegate::reportSyncGCEnd(MM_EnvironmentBase *env)
{
OMRPORT_ACCESS_FROM_ENVIRONMENT(env);
UDATA approximateFreeMemorySize = _extensions->heap->getApproximateActiveFreeMemorySize();
#if defined(OMR_GC_DYNAMIC_CLASS_UNLOADING)
MM_ClassUnloadStats *classUnloadStats = &_extensions->globalGCStats.classUnloadStats;
UDATA classLoaderUnloadCount = classUnloadStats->_classLoaderUnloadedCount;
UDATA classUnloadCount = classUnloadStats->_classesUnloadedCount;
UDATA anonymousClassUnloadCount = classUnloadStats->_anonymousClassesUnloadedCount;
#else /* defined(OMR_GC_DYNAMIC_CLASS_UNLOADING) */
UDATA classLoaderUnloadCount = 0;
UDATA classUnloadCount = 0;
UDATA anonymousClassUnloadCount = 0;
#endif /* defined(OMR_GC_DYNAMIC_CLASS_UNLOADING) */
UDATA weakReferenceCount = _extensions->markJavaStats._weakReferenceStats._cleared;
UDATA softReferenceCount = _extensions->markJavaStats._softReferenceStats._cleared;
UDATA maxSoftReferenceAge = _extensions->getMaxSoftReferenceAge();
UDATA softReferenceAge = _extensions->getDynamicMaxSoftReferenceAge();
UDATA phantomReferenceCount = _extensions->markJavaStats._phantomReferenceStats._cleared;
UDATA finalizerCount = _extensions->globalGCStats.metronomeStats.getWorkPacketOverflowCount();
UDATA packetOverflowCount = _extensions->globalGCStats.metronomeStats.getWorkPacketOverflowCount();
UDATA objectOverflowCount = _extensions->globalGCStats.metronomeStats.getObjectOverflowCount();
Trc_MM_SynchGCEnd(env->getLanguageVMThread(),
approximateFreeMemorySize,
0,
classLoaderUnloadCount,
classUnloadCount,
weakReferenceCount,
softReferenceCount,
maxSoftReferenceAge,
softReferenceAge,
phantomReferenceCount,
finalizerCount,
packetOverflowCount,
objectOverflowCount
);
TRIGGER_J9HOOK_MM_PRIVATE_METRONOME_SYNCHRONOUS_GC_END(_extensions->privateHookInterface,
env->getOmrVMThread(), omrtime_hires_clock(),
J9HOOK_MM_PRIVATE_METRONOME_SYNCHRONOUS_GC_END,
approximateFreeMemorySize,
0,
classLoaderUnloadCount,
classUnloadCount,
anonymousClassUnloadCount,
weakReferenceCount,
softReferenceCount,
maxSoftReferenceAge,
softReferenceAge,
phantomReferenceCount,
finalizerCount,
packetOverflowCount,
objectOverflowCount
);
}
/**
* Factory method for creating the access barrier. Note that the default realtime access barrier
* doesn't handle the RTSJ checks.
*/
MM_RealtimeAccessBarrier*
MM_MetronomeDelegate::allocateAccessBarrier(MM_EnvironmentBase *env)
{
return MM_RealtimeAccessBarrier::newInstance(env);
}
/**
* Iterates over all threads and enables the double barrier for each thread by setting the
* remembered set fragment index to the reserved index.
*/
void
MM_MetronomeDelegate::enableDoubleBarrier(MM_EnvironmentBase *env)
{
MM_GCExtensions* extensions = MM_GCExtensions::getExtensions(env);
MM_RealtimeAccessBarrier* realtimeAccessBarrier = (MM_RealtimeAccessBarrier*)extensions->accessBarrier;
GC_VMThreadListIterator vmThreadListIterator(_javaVM);
/* First, enable the global double barrier flag so new threads will have the double barrier enabled. */
realtimeAccessBarrier->setDoubleBarrierActive();
while(J9VMThread* thread = vmThreadListIterator.nextVMThread()) {
/* Second, enable the double barrier on all threads individually. */
realtimeAccessBarrier->setDoubleBarrierActiveOnThread(MM_EnvironmentBase::getEnvironment(thread->omrVMThread));
}
}
/**
* Disables the double barrier for the specified thread.
*/
void
MM_MetronomeDelegate::disableDoubleBarrierOnThread(MM_EnvironmentBase* env, OMR_VMThread* vmThread)
{
/* This gets called on a per thread basis as threads get scanned. */
MM_GCExtensions* extensions = MM_GCExtensions::getExtensions(env);
MM_RealtimeAccessBarrier* realtimeAccessBarrier = (MM_RealtimeAccessBarrier*)extensions->accessBarrier;
realtimeAccessBarrier->setDoubleBarrierInactiveOnThread(MM_EnvironmentBase::getEnvironment(vmThread));
}
/**
* Disables the global double barrier flag. This should be called after all threads have been scanned
* and disableDoubleBarrierOnThread has been called on each of them.
*/
void
MM_MetronomeDelegate::disableDoubleBarrier(MM_EnvironmentBase* env)
{
/* The enabling of the double barrier must traverse all threads, but the double barrier gets disabled
* on a per thread basis as threads get scanned, so no need to traverse all threads in this method.
*/
MM_GCExtensions* extensions = MM_GCExtensions::getExtensions(env);
MM_RealtimeAccessBarrier* realtimeAccessBarrier = (MM_RealtimeAccessBarrier*)extensions->accessBarrier;
realtimeAccessBarrier->setDoubleBarrierInactive();
}
#if defined(J9VM_GC_DYNAMIC_CLASS_UNLOADING)
/**
* Walk all class loaders marking their classes if the classLoader object has been
* marked.
*
* @return true if any classloaders/classes are marked, false otherwise
*/
bool
MM_MetronomeDelegate::doClassTracing(MM_EnvironmentRealtime *env)
{
J9ClassLoader *classLoader;
bool didWork = false;
MM_GCExtensions* extensions = MM_GCExtensions::getExtensions(env);
GC_ClassLoaderLinkedListIterator classLoaderIterator(env, extensions->classLoaderManager);
while((classLoader = (J9ClassLoader *)classLoaderIterator.nextSlot()) != NULL) {
if (0 == (classLoader->gcFlags & J9_GC_CLASS_LOADER_DEAD)) {
if(J9CLASSLOADER_ANON_CLASS_LOADER == (classLoader->flags & J9CLASSLOADER_ANON_CLASS_LOADER)) {
/* Anonymous classloader should be scanned on level of classes every time */
GC_ClassLoaderSegmentIterator segmentIterator(classLoader, MEMORY_TYPE_RAM_CLASS);
J9MemorySegment *segment = NULL;
while(NULL != (segment = segmentIterator.nextSegment())) {
GC_ClassHeapIterator classHeapIterator(_javaVM, segment);
J9Class *clazz = NULL;
while(NULL != (clazz = classHeapIterator.nextClass())) {
if((0 == (J9CLASS_EXTENDED_FLAGS(clazz) & J9ClassGCScanned)) && _markingScheme->isMarked(clazz->classObject)) {
J9CLASS_EXTENDED_FLAGS_SET(clazz, J9ClassGCScanned);
/* Scan class */
GC_ClassIterator objectSlotIterator(env, clazz);
volatile j9object_t *objectSlotPtr = NULL;
while((objectSlotPtr = objectSlotIterator.nextSlot()) != NULL) {
didWork |= _markingScheme->markObject(env, *objectSlotPtr);
}
GC_ClassIteratorClassSlots classSlotIterator(clazz);
J9Class **classSlotPtr;
while((classSlotPtr = classSlotIterator.nextSlot()) != NULL) {
didWork |= markClass(env, *classSlotPtr);
}
}
}
_realtimeGC->condYield(env, 0);
}
} else {
/* Check if the class loader has not been scanned but the class loader is live */
if( !(classLoader->gcFlags & J9_GC_CLASS_LOADER_SCANNED) && _markingScheme->isMarked((J9Object *)classLoader->classLoaderObject)) {
/* Flag the class loader as being scanned */
classLoader->gcFlags |= J9_GC_CLASS_LOADER_SCANNED;
GC_ClassLoaderSegmentIterator segmentIterator(classLoader, MEMORY_TYPE_RAM_CLASS);
J9MemorySegment *segment = NULL;
J9Class *clazz;
while(NULL != (segment = segmentIterator.nextSegment())) {
GC_ClassHeapIterator classHeapIterator(_javaVM, segment);
while(NULL != (clazz = classHeapIterator.nextClass())) {
/* Scan class */
GC_ClassIterator objectSlotIterator(env, clazz);
volatile j9object_t *objectSlotPtr = NULL;
while((objectSlotPtr = objectSlotIterator.nextSlot()) != NULL) {
didWork |= _markingScheme->markObject(env, *objectSlotPtr);
}
GC_ClassIteratorClassSlots classSlotIterator(clazz);
J9Class **classSlotPtr;
while((classSlotPtr = classSlotIterator.nextSlot()) != NULL) {
didWork |= markClass(env, *classSlotPtr);
}
}
_realtimeGC->condYield(env, 0);
}
/* CMVC 131487 */
J9HashTableState walkState;
/*
* We believe that (NULL == classLoader->classHashTable) is set ONLY for DEAD class loader
* so, if this pointer happened to be NULL at this point let it crash here
*/
Assert_MM_true(NULL != classLoader->classHashTable);
/*
* CMVC 178060 : disable hash table growth to prevent hash table entries from being rehashed during GC yield
* while GC was in the middle of iterating the hash table.
*/
hashTableSetFlag(classLoader->classHashTable, J9HASH_TABLE_DO_NOT_REHASH);
clazz = _javaVM->internalVMFunctions->hashClassTableStartDo(classLoader, &walkState);
while (NULL != clazz) {
didWork |= markClass(env, clazz);
clazz = _javaVM->internalVMFunctions->hashClassTableNextDo(&walkState);
/**
* Jazz103 55784: We cannot rehash the table in the middle of iteration and the Space-opt hashtable cannot grow if
* J9HASH_TABLE_DO_NOT_REHASH is enabled. Don't yield if the hashtable is space-optimized because we run the
* risk of the mutator not being able to grow to accommodate new elements.
*/
if (!hashTableIsSpaceOptimized(classLoader->classHashTable)) {
_realtimeGC->condYield(env, 0);
}
}
/*
* CMVC 178060 : re-enable hash table growth. disable hash table growth to prevent hash table entries from being rehashed during GC yield
* while GC was in the middle of iterating the hash table.
*/
hashTableResetFlag(classLoader->classHashTable, J9HASH_TABLE_DO_NOT_REHASH);
if (NULL != classLoader->moduleHashTable) {
J9Module **modulePtr = (J9Module **)hashTableStartDo(classLoader->moduleHashTable, &walkState);
while (NULL != modulePtr) {
J9Module * const module = *modulePtr;
didWork |= _markingScheme->markObject(env, module->moduleObject);
didWork |= _markingScheme->markObject(env, module->moduleName);
didWork |= _markingScheme->markObject(env, module->version);
modulePtr = (J9Module**)hashTableNextDo(&walkState);
}
}
}