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ParallelGlobalGC.cpp
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ParallelGlobalGC.cpp
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/*******************************************************************************
* Copyright (c) 1991, 2021 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 "omrcfg.h"
#include "omrmodroncore.h"
#include "gcutils.h"
#include "ModronAssertions.h"
#include "modronbase.h"
#include "modronopt.h"
#include "modronapicore.hpp"
#include "AllocateDescription.hpp"
#include "AllocationFailureStats.hpp"
#include "CollectionStatisticsStandard.hpp"
#include "CollectorLanguageInterface.hpp"
#if defined(OMR_GC_MODRON_COMPACTION)
#include "CompactScheme.hpp"
#endif /* OMR_GC_MODRON_COMPACTION */
#include "Configuration.hpp"
#include "CycleState.hpp"
#include "EnvironmentBase.hpp"
#include "GlobalAllocationManager.hpp"
#include "Heap.hpp"
#include "HeapMapIterator.hpp"
#include "HeapRegionDescriptorStandard.hpp"
#include "HeapRegionIteratorStandard.hpp"
#include "MarkingScheme.hpp"
#include "MemorySpace.hpp"
#include "MemorySubSpace.hpp"
#include "MemorySubSpaceSemiSpace.hpp"
#include "MemoryPoolLargeObjects.hpp"
#include "ObjectAllocationInterface.hpp"
#if defined(OMR_GC_OBJECT_MAP)
#include "ObjectMap.hpp"
#endif /* defined(OMR_GC_OBJECT_MAP) */
#include "OMRVMInterface.hpp"
#include "ObjectIterator.hpp"
#if defined(OMR_GC_MODRON_COMPACTION)
#include "ParallelCompactTask.hpp"
#endif /* OMR_GC_MODRON_COMPACTION */
#include "ParallelDispatcher.hpp"
#include "ParallelGlobalGC.hpp"
#include "ParallelMarkTask.hpp"
#include "ParallelSweepScheme.hpp"
#include "ParallelTask.hpp"
#if defined(OMR_GC_MODRON_SCAVENGER)
#include "Scavenger.hpp"
#endif /* OMR_GC_MODRON_SCAVENGER */
#include "WorkPackets.hpp"
/* OMRTODO temporary workaround to allow both ut_j9mm.h and ut_omrmm.h to be included.
* Dependency on ut_j9mm.h should be removed in the future.
*/
#undef UT_MODULE_LOADED
#undef UT_MODULE_UNLOADED
#include "ut_omrmm.h"
#if defined(OMR_VALGRIND_MEMCHECK)
#include "MemcheckWrapper.hpp"
#endif /* defined(OMR_VALGRIND_MEMCHECK) */
#if defined(OMR_ENV_DATA64) && defined(OMR_GC_FULL_POINTERS)
void
poisonReferenceSlot(MM_EnvironmentBase *env, GC_SlotObject *slotObject)
{
MM_GCExtensionsBase *extensions = env->getExtensions();
uintptr_t heapBase = (uintptr_t)extensions->heap->getHeapBase();
uintptr_t heapTop = (uintptr_t)extensions->heap->getHeapTop();
uintptr_t referenceFromSlot = (uintptr_t)slotObject->readReferenceFromSlot();
if ((heapTop > referenceFromSlot) && (heapBase <= referenceFromSlot)) {
uintptr_t shadowHeapBase = (uintptr_t)extensions->shadowHeapBase;
uintptr_t poisonedAddress = shadowHeapBase + (referenceFromSlot - heapBase);
slotObject->writeReferenceToSlot((omrobjectptr_t)poisonedAddress);
}
}
void
poisonReferenceSlots(OMR_VMThread *omrVMThread, MM_HeapRegionDescriptor *region, omrobjectptr_t object, void *userData)
{
GC_ObjectIterator objectIterator(omrVMThread->_vm, object);
GC_SlotObject *slotObject = NULL;
MM_EnvironmentBase *env = MM_EnvironmentBase::getEnvironment(omrVMThread);
while (NULL != (slotObject = objectIterator.nextSlot())) {
poisonReferenceSlot(env, slotObject);
}
}
void
healReferenceSlot(MM_EnvironmentBase *env, GC_SlotObject *slotObject)
{
MM_GCExtensionsBase *extensions = env->getExtensions();
uintptr_t shadowHeapBase = (uintptr_t)extensions->shadowHeapBase;
uintptr_t referenceFromSlot = (uintptr_t)slotObject->readReferenceFromSlot();
uintptr_t shadowHeapTop = (uintptr_t)extensions->shadowHeapTop;
if ((shadowHeapTop > referenceFromSlot) && (shadowHeapBase <= referenceFromSlot)) {
uintptr_t heapBase = (uintptr_t)extensions->heap->getHeapBase();
uintptr_t healedHeapAddress = heapBase + (referenceFromSlot - shadowHeapBase);
/* This healing occurs at the start of GC, hence, does not need atomic write */
slotObject->writeReferenceToSlot((omrobjectptr_t)healedHeapAddress);
}
}
void
healReferenceSlots(OMR_VMThread *omrVMThread, MM_HeapRegionDescriptor *region, omrobjectptr_t object, void *userData)
{
GC_ObjectIterator objectIterator(omrVMThread->_vm, object);
GC_SlotObject *slotObject = NULL;
MM_EnvironmentBase *env = MM_EnvironmentBase::getEnvironment(omrVMThread);
while (NULL != (slotObject = objectIterator.nextSlot())) {
healReferenceSlot(env, slotObject);
}
}
#endif /* defined(OMR_ENV_DATA64) && defined(OMR_GC_FULL_POINTERS) */
/* Define hook routines to be called on AF start and End */
static void globalGCHookAFCycleStart(J9HookInterface** hook, uintptr_t eventNum, void* eventData, void* userData);
static void globalGCHookAFCycleEnd(J9HookInterface** hook, uintptr_t eventNum, void* eventData, void* userData);
#if defined(OMR_GC_MODRON_CONCURRENT_MARK)
static void globalGCHookCCStart(J9HookInterface** hook, uintptr_t eventNum, void* eventData, void* userData);
static void globalGCHookCCEnd(J9HookInterface** hook, uintptr_t eventNum, void* eventData, void* userData);
#endif /* OMR_GC_MODRON_CONCURRENT_MARK */
static void globalGCHookSysStart(J9HookInterface** hook, uintptr_t eventNum, void* eventData, void* userData);
static void globalGCHookSysEnd(J9HookInterface** hook, uintptr_t eventNum, void* eventData, void* userData);
/**
* Function to fix single dead object on the heap
*
* NOTE that this function is expected to represent the SUPERSET of dead object fixup needs in that it will
* fix all objects which are known to be dead. Any optimizations to this function must be careful not to
* violate that meaning (see CMVC 122959 for an example of such a mistake).
*/
static void
fixObject(OMR_VMThread *omrVMThread, MM_HeapRegionDescriptor *region, omrobjectptr_t object, void *userData)
{
MM_GCExtensionsBase *extensions = MM_GCExtensionsBase::getExtensions(omrVMThread->_vm);
MM_ParallelGlobalGC *collector = (MM_ParallelGlobalGC *)extensions->getGlobalCollector();
/* Check the mark state of each object. If it isn't marked, build a dead object */
if( !collector->getMarkingScheme()->isMarked(object) ) {
MM_MemorySubSpace *memorySubSpace = region->getSubSpace();
uintptr_t deadObjectByteSize = extensions->objectModel.getConsumedSizeInBytesWithHeader(object);
#if defined(OMR_VALGRIND_MEMCHECK)
/* Also clear dead object from valgrind pool
* This could have been done directly inside internalRecycleHeapChunk (MemoryPoolAddressOrderedListBase.hpp)
* but due to current limitation of API that requires address of object to be freed
* which we need to check from a set stored in extensions, which weren't further passed
* we will check it here. But in case new API is added, it is better to move there.
*/
if(valgrindCheckObjectInPool(extensions,(uintptr_t) object))
valgrindFreeObject(extensions,(uintptr_t) object);
#endif /* defined(OMR_VALGRIND_MEMCHECK) */
memorySubSpace->abandonHeapChunk(object, ((U_8*)object) + deadObjectByteSize);
/* the userdata is a counter of dead objects fixed up so increment it here as a uintptr_t */
*((uintptr_t *)userData) += 1;
}
}
#if defined(OMR_GC_MODRON_SCAVENGER)
/**
* Fix the heap if the remembered set for the scavenger is in an overflow state.
*/
static void
hookGlobalGcSweepEndRsoSafetyFixHeap(J9HookInterface** hook, uintptr_t eventNum, void* eventData, void* userData)
{
MM_SweepEndEvent* event = (MM_SweepEndEvent*)eventData;
MM_EnvironmentBase *env = MM_EnvironmentBase::getEnvironment(event->currentThread);
MM_GCExtensionsBase *extensions = env->getExtensions();
extensions->scavengerRsoScanUnsafe = !extensions->isRememberedSetInOverflowState();
if (!extensions->scavengerRsoScanUnsafe) {
MM_ParallelGlobalGC *pggc = (MM_ParallelGlobalGC *)userData;
pggc->fixHeapForWalk(env, MEMORY_TYPE_OLD_RAM, FIXUP_DEBUG_TOOLING, fixObject);
}
}
#if defined(OMR_GC_CONCURRENT_SCAVENGER)
static void
hookGlobalGcSweepEndAbortedCSFixHeap(J9HookInterface** hook, UDATA eventNum, void* eventData, void* userData)
{
MM_SweepEndEvent* event = (MM_SweepEndEvent*)eventData;
MM_EnvironmentStandard *env = MM_EnvironmentStandard::getEnvironment(event->currentThread);
MM_GCExtensionsBase *extensions = env->getExtensions();
uintptr_t holeCount = 0;
Trc_MM_FixHeapForWalk_Entry(env->getLanguageVMThread(), MEMORY_TYPE_NEW);
if (extensions->isScavengerBackOutFlagRaised()) {
GC_HeapRegionIteratorStandard regionIterator(extensions->getHeap()->getHeapRegionManager());
MM_HeapRegionDescriptorStandard *region = NULL;
/* create holes between two marked objects */
while(NULL != (region = regionIterator.nextRegion())) {
if (MEMORY_TYPE_NEW == (region->getTypeFlags() & MEMORY_TYPE_NEW)) {
void *lowAddress = region->getLowAddress();
void *highAddress = region->getHighAddress();
MM_HeapMapIterator markedObjectIterator(extensions, ((MM_ParallelGlobalGC *)extensions->getGlobalCollector())->getMarkingScheme()->getMarkMap(), (UDATA *)lowAddress, (UDATA *)highAddress);
void * prevEndObjectPtr = lowAddress;
omrobjectptr_t objectPtr = NULL;
while (NULL != (objectPtr = markedObjectIterator.nextObject())) {
UDATA objectSize = extensions->objectModel.getConsumedSizeInBytesWithHeader(objectPtr);
if (prevEndObjectPtr != objectPtr) {
region->getSubSpace()->abandonHeapChunk(prevEndObjectPtr, objectPtr);
holeCount += 1;
}
prevEndObjectPtr = (void *)((U_8*)objectPtr + objectSize);
}
if (prevEndObjectPtr != highAddress) {
region->getSubSpace()->abandonHeapChunk(prevEndObjectPtr, highAddress);
holeCount += 1;
}
}
}
}
Trc_MM_FixHeapForWalk_Exit(env->getLanguageVMThread(), holeCount);
}
#endif /* OMR_GC_CONCURRENT_SCAVENGER */
#endif /* OMR_GC_MODRON_SCAVENGER */
/**
* Initialization
*/
MM_ParallelGlobalGC *
MM_ParallelGlobalGC::newInstance(MM_EnvironmentBase *env)
{
MM_ParallelGlobalGC *globalGC;
globalGC = (MM_ParallelGlobalGC *)env->getForge()->allocate(sizeof(MM_ParallelGlobalGC), OMR::GC::AllocationCategory::FIXED, OMR_GET_CALLSITE());
if (globalGC) {
new(globalGC) MM_ParallelGlobalGC(env);
if (!globalGC->initialize(env)) {
globalGC->kill(env);
globalGC = NULL;
}
}
return globalGC;
}
void
MM_ParallelGlobalGC::kill(MM_EnvironmentBase *env)
{
tearDown(env);
env->getForge()->free(this);
}
/**
* Initialize the collector's internal structures and values.
* @return true if initialization completed, false otherwise
*/
bool
MM_ParallelGlobalGC::initialize(MM_EnvironmentBase *env)
{
J9HookInterface** mmPrivateHooks = J9_HOOK_INTERFACE(_extensions->privateHookInterface);
if (gc_policy_nogc == env->getExtensions()->configurationOptions._gcPolicy) {
_cycleType = OMR_GC_CYCLE_TYPE_EPSILON;
_disableGC = true;
}
_markingScheme = MM_MarkingScheme::newInstance(env);
if (NULL == _markingScheme) {
goto error_no_memory;
}
_delegate.initialize(env, this, _markingScheme);
_sweepScheme = createSweepScheme(env, this);
if (NULL == _sweepScheme) {
goto error_no_memory;
}
#if defined(OMR_GC_OBJECT_MAP)
_extensions->setObjectMap(MM_ObjectMap::newInstance(env));
if(NULL == _extensions->getObjectMap()) {
goto error_no_memory;
}
#endif /* defined(OMR_GC_OBJECT_MAP) */
#if defined(OMR_GC_MODRON_COMPACTION)
_compactScheme = MM_CompactScheme::newInstance(env, _markingScheme);
if(NULL == _compactScheme) {
goto error_no_memory;
}
#endif /* defined(OMR_GC_MODRON_COMPACTION) */
_heapWalker = MM_ParallelHeapWalker::newInstance(this, _markingScheme->getMarkMap(), env);
if (NULL == _heapWalker) {
goto error_no_memory;
}
/* Attach to hooks required by the global collector's
* heap resize (expand/contraction) functions
*/
(*mmPrivateHooks)->J9HookRegisterWithCallSite(mmPrivateHooks, J9HOOK_MM_PRIVATE_ALLOCATION_FAILURE_CYCLE_START, globalGCHookAFCycleStart, OMR_GET_CALLSITE(), NULL);
(*mmPrivateHooks)->J9HookRegisterWithCallSite(mmPrivateHooks, J9HOOK_MM_PRIVATE_ALLOCATION_FAILURE_CYCLE_END, globalGCHookAFCycleEnd, OMR_GET_CALLSITE(), NULL);
#if defined(OMR_GC_MODRON_CONCURRENT_MARK)
(*mmPrivateHooks)->J9HookRegisterWithCallSite(mmPrivateHooks, J9HOOK_MM_PRIVATE_CONCURRENT_COLLECTION_START, globalGCHookCCStart, OMR_GET_CALLSITE(), NULL);
(*mmPrivateHooks)->J9HookRegisterWithCallSite(mmPrivateHooks, J9HOOK_MM_PRIVATE_CONCURRENT_COLLECTION_END, globalGCHookCCEnd, OMR_GET_CALLSITE(), NULL);
#endif /* OMR_GC_MODRON_CONCURRENT_MARK */
(*mmPrivateHooks)->J9HookRegisterWithCallSite(mmPrivateHooks, J9HOOK_MM_PRIVATE_SYSTEM_GC_START, globalGCHookSysStart, OMR_GET_CALLSITE(), NULL);
(*mmPrivateHooks)->J9HookRegisterWithCallSite(mmPrivateHooks, J9HOOK_MM_PRIVATE_SYSTEM_GC_END, globalGCHookSysEnd, OMR_GET_CALLSITE(), NULL);
#if defined(OMR_GC_MODRON_SCAVENGER)
if (_extensions->scavengerEnabled) {
/* Hook the global collector to guarantee heap walk safety in the event of an RSO */
/* NOTE: This will be a one time hook across all instances as the function and user data will be identical - i.e.,
* we will only get one Hook registered no matter how many scavengers are created/initialized
*/
(*mmPrivateHooks)->J9HookRegisterWithCallSite(mmPrivateHooks, J9HOOK_MM_PRIVATE_SWEEP_END, hookGlobalGcSweepEndRsoSafetyFixHeap, OMR_GET_CALLSITE(), this);
#if defined(OMR_GC_CONCURRENT_SCAVENGER)
if (_extensions->isConcurrentScavengerEnabled()) {
(*mmPrivateHooks)->J9HookRegisterWithCallSite(mmPrivateHooks, J9HOOK_MM_PRIVATE_SWEEP_END, hookGlobalGcSweepEndAbortedCSFixHeap, OMR_GET_CALLSITE(), this);
}
#endif /* OMR_GC_CONCURRENT_SCAVENGER */
}
#endif /* OMR_GC_MODRON_SCAVENGER */
return true;
error_no_memory:
return false;
}
/**
* Free any internal structures associated to the receiver.
*/
void
MM_ParallelGlobalGC::tearDown(MM_EnvironmentBase *env)
{
_delegate.tearDown(env);
if(NULL != _markingScheme) {
_markingScheme->kill(env);
_markingScheme = NULL;
}
if(NULL != _sweepScheme) {
_sweepScheme->kill(env);
_sweepScheme = NULL;
}
#if defined(OMR_GC_MODRON_COMPACTION)
if(NULL != _compactScheme) {
_compactScheme->kill(env);
_compactScheme = NULL;
}
#endif /* OMR_GC_MODRON_COMPACTION */
if (NULL != _heapWalker) {
_heapWalker->kill(env);
_heapWalker = NULL;
}
}
uintptr_t
MM_ParallelGlobalGC::getVMStateID()
{
return OMRVMSTATE_GC_COLLECTOR_GLOBALGC;
}
/****************************************
* Thread work routines
****************************************
*/
void
MM_ParallelGlobalGC::cleanupAfterGC(MM_EnvironmentBase *env, MM_AllocateDescription *allocDescription)
{
updateTuningStatistics(env);
/* Perform the resize now. The decision was earlier */
env->_cycleState->_activeSubSpace->performResize(env, allocDescription);
/* Heap size now fixed for next cycle so reset heap statistics */
_extensions->heap->resetHeapStatistics(true);
#if defined(OMR_GC_MODRON_SCAVENGER)
GC_OMRVMThreadListIterator threadIterator(_extensions->getOmrVM());
OMR_VMThread *walkThread = NULL;
/* Null tenure TLH (Copy Cache) references for all GC worker and Mutator (for concurrent scavenger) threads as the memory will be invalidated on sweep cycle*/
while((walkThread = threadIterator.nextOMRVMThread()) != NULL) {
MM_EnvironmentStandard *threadEnvironment = MM_EnvironmentStandard::getEnvironment(walkThread);
threadEnvironment->_tenureTLHRemainderBase = NULL;
threadEnvironment->_tenureTLHRemainderTop = NULL;
}
_extensions->_mainThreadTenureTLHRemainderTop = NULL;
_extensions->_mainThreadTenureTLHRemainderBase = NULL;
#endif /* OMR_GC_MODRON_SCAVENGER */
}
void
MM_ParallelGlobalGC::mainThreadGarbageCollect(MM_EnvironmentBase *env, MM_AllocateDescription *allocDescription, bool initMarkMap, bool rebuildMarkBits)
{
if (_extensions->trackMutatorThreadCategory) {
/* This thread is doing GC work, account for the time spent into the GC bucket */
omrthread_set_category(env->getOmrVMThread()->_os_thread, J9THREAD_CATEGORY_SYSTEM_GC_THREAD, J9THREAD_TYPE_SET_GC);
}
/* Perform any main-specific setup */
/* Tell the GAM to flush its contexts */
MM_GlobalAllocationManager *gam = _extensions->globalAllocationManager;
if (NULL != gam) {
gam->flushAllocationContexts(env);
}
/* ----- start of setupForCollect ------*/
/* ensure heap base is aligned to region size */
uintptr_t heapBase = (uintptr_t)_extensions->heap->getHeapBase();
uintptr_t regionSize = _extensions->regionSize;
Assert_MM_true((0 != regionSize) && (0 == (heapBase % regionSize)));
/* Reset memory pools of associated memory spaces */
_extensions->heap->resetSpacesForGarbageCollect(env);
/* Clear the gc stats structure */
_extensions->globalGCStats.clear();
#if defined(OMR_GC_MODRON_COMPACTION)
_compactThisCycle = false;
#endif /* OMR_GC_MODRON_COMPACTION */
_fixHeapForWalkCompleted = false;
_delegate.mainThreadGarbageCollectStarted(env);
/* ----- end of setupForCollect ------*/
/* Run a garbage collect */
/* Mark */
markAll(env, initMarkMap);
_delegate.postMarkProcessing(env);
sweep(env, allocDescription, rebuildMarkBits);
#if defined(OMR_GC_MODRON_COMPACTION)
/* If a compaction was required, then do one */
if (_compactThisCycle) {
_collectionStatistics._tenureFragmentation = MICRO_FRAGMENTATION;
if (GLOBALGC_ESTIMATE_FRAGMENTATION == (_extensions->estimateFragmentation & GLOBALGC_ESTIMATE_FRAGMENTATION)) {
_collectionStatistics._tenureFragmentation |= MACRO_FRAGMENTATION;
}
mainThreadCompact(env, allocDescription, rebuildMarkBits);
_collectionStatistics._tenureFragmentation = NO_FRAGMENTATION;
if (_extensions->processLargeAllocateStats) {
processLargeAllocateStatsAfterCompact(env);
}
} else {
/* If a compaction was prevented, report the reason */
CompactPreventedReason compactPreventedReason = (CompactPreventedReason)(_extensions->globalGCStats.compactStats._compactPreventedReason);
if(COMPACT_PREVENTED_NONE != compactPreventedReason) {
MM_CompactStats *compactStats = &_extensions->globalGCStats.compactStats;
reportCompactStart(env);
Trc_MM_CompactPrevented(env->getLanguageVMThread(), getCompactionPreventedReasonAsString(compactPreventedReason));
compactStats->_startTime = 0;
compactStats->_endTime = 0;
reportCompactEnd(env);
}
_collectionStatistics._tenureFragmentation = MICRO_FRAGMENTATION;
if (GLOBALGC_ESTIMATE_FRAGMENTATION == (_extensions->estimateFragmentation & GLOBALGC_ESTIMATE_FRAGMENTATION)) {
_collectionStatistics._tenureFragmentation |= MACRO_FRAGMENTATION;
}
}
#endif /* defined(OMR_GC_MODRON_COMPACTION) */
bool compactedThisCycle = false;
#if defined(OMR_GC_MODRON_COMPACTION)
compactedThisCycle = _compactThisCycle;
#endif /* OMR_GC_MODRON_COMPACTION */
/* If the delegate has isAllowUserHeapWalk set, fix the heap so that it can be walked */
if (_delegate.isAllowUserHeapWalk() || env->_cycleState->_gcCode.isRASDumpGC()) {
if (!_fixHeapForWalkCompleted) {
#if defined(OMR_GC_MODRON_COMPACTION)
if (compactedThisCycle) {
OMRPORT_ACCESS_FROM_ENVIRONMENT(env);
U_64 startTime = omrtime_hires_clock();
getCompactScheme(env)->fixHeapForWalk(env);
_extensions->globalGCStats.fixHeapForWalkTime = omrtime_hires_delta(startTime, omrtime_hires_clock(), OMRPORT_TIME_DELTA_IN_MICROSECONDS);
_extensions->globalGCStats.fixHeapForWalkReason = FIXUP_DEBUG_TOOLING;
} else
#endif /* OMR_GC_MODRON_COMPACTION */
{
fixHeapForWalk(env, MEMORY_TYPE_RAM, FIXUP_DEBUG_TOOLING, fixObject);
}
/* since this is the superset of all walk operations, we can safely set the flag that states other walks
* can be omitted for this cycle as redundant (CMVC 122959)
*/
_fixHeapForWalkCompleted = true;
}
}
_delegate.mainThreadGarbageCollectFinished(env, compactedThisCycle);
#if defined(OMR_GC_MODRON_COMPACTION)
if (compactedThisCycle) {
/* Free space will have changed as a result of compaction so recalculate
* any expand or contract target.
* Concurrent Scavenger requires this be done after fixup heap for walk pass.
*/
env->_cycleState->_activeSubSpace->checkResize(env, allocDescription, env->_cycleState->_gcCode.isExplicitGC());
}
#endif
#if defined(OMR_GC_MODRON_SCAVENGER)
/* Merge sublists in the remembered set (if necessary) */
_extensions->rememberedSet.compact(env);
_extensions->oldHeapSizeOnLastGlobalGC = _extensions->heap->getActiveMemorySize(MEMORY_TYPE_OLD);
_extensions->freeOldHeapSizeOnLastGlobalGC = _extensions->heap->getApproximateActiveFreeMemorySize(MEMORY_TYPE_OLD);
#endif /* OMR_GC_MODRON_SCAVENGER */
/* Restart the allocation caches associated to all threads */
mainThreadRestartAllocationCaches(env);
/* ----- start of cleanupAfterCollect ------*/
reportGlobalGCCollectComplete(env);
cleanupAfterGC(env, allocDescription);
if (_extensions->trackMutatorThreadCategory) {
/* Done doing GC, reset the category back to the old one */
omrthread_set_category(env->getOmrVMThread()->_os_thread, 0, J9THREAD_TYPE_SET_GC);
}
}
#if defined(OMR_GC_MODRON_COMPACTION)
bool
MM_ParallelGlobalGC::shouldCompactThisCycle(MM_EnvironmentBase *env, MM_AllocateDescription *allocDescription, uintptr_t activeSubspaceMaxExpansionInSpace, MM_GCCode gcCode)
{
MM_Heap *heap = _extensions->heap;
MM_AllocationStats *allocStats = &_extensions->allocationStats;
CompactReason compactReason = COMPACT_NONE;
CompactPreventedReason compactPreventedReason = COMPACT_PREVENTED_NONE;
uintptr_t tlhPercent, totalBytesAllocated;
/* Assume no compaction is required until we prove otherwise*/
/* If user has specified -XnoCompact then were done */
if(_extensions->noCompactOnGlobalGC) {
compactReason = COMPACT_NONE;
goto nocompact;
}
#if defined(OMR_GC_IDLE_HEAP_MANAGER)
if((_extensions->compactOnIdle) && (J9MMCONSTANT_EXPLICIT_GC_IDLE_GC == gcCode.getCode())) {
compactReason = COMPACT_FORCED_GC;
goto compactionReqd;
}
#endif
/* RAS dump compact requests override all other options. If a dump agent requested
* a compact we always honour it in order to produce optimal heap dumps
*/
if (J9MMCONSTANT_EXPLICIT_GC_RASDUMP_COMPACT == gcCode.getCode()) {
compactReason = COMPACT_FORCED_GC;
goto compactionReqd;
}
/* If user has specified -XCompact then we compact every time */
if(_extensions->compactOnGlobalGC) {
compactReason = COMPACT_ALWAYS;
goto compactionReqd;
}
/* Aborted CS needs global GC with Nursery compaction */
if (_extensions->isConcurrentScavengerEnabled() && _extensions->isScavengerBackOutFlagRaised()) {
compactReason = COMPACT_ABORTED_SCAVENGE;
goto compactionReqd;
}
/* Is this a system GC ? */
if(gcCode.isExplicitGC()) {
/* If the user as specified -XcompactexplicitGC then compact*/
if(_extensions->compactOnSystemGC){
compactReason = COMPACT_FORCED_GC;
goto compactionReqd;
} else if(_extensions->nocompactOnSystemGC){
compactReason = COMPACT_NONE;
/* The user as specified -XnocompactexplicitGC then we don't compact*/
goto nocompact;
}
}
/* Has GC found enough storage to satisfy the allocation request ? */
if(allocDescription){
MM_MemorySpace *memorySpace = env->getMemorySpace();
uintptr_t largestFreeEntry = memorySpace->findLargestFreeEntry(env, allocDescription);
uintptr_t bytesRequested = allocDescription->getBytesRequested();
if(bytesRequested > largestFreeEntry){
compactReason = COMPACT_LARGE;
goto compactionReqd;
}
}
/* If -Xgc:compactToSatisfyAllocate has been specified, then we skip the rest of the triggers */
if (_extensions->compactToSatisfyAllocate) {
compactReason = COMPACT_NONE;
goto nocompact;
}
#if defined(OMR_GC_MODRON_SCAVENGER)
if (_extensions->scavengerEnabled) {
/* Get size of largest object we failed to tenure on last scavenege */
uintptr_t failedTenureLargest = _extensions->scavengerStats._failedTenureLargest;
if (failedTenureLargest > 0) {
MM_MemorySpace *memorySpace = env->getMemorySpace();
MM_AllocateDescription tenureAllocDescription(failedTenureLargest, OMR_GC_ALLOCATE_OBJECT_TENURED, false, true);
uintptr_t largestTenureFreeEntry = memorySpace->findLargestFreeEntry(env, &tenureAllocDescription);
if(failedTenureLargest > largestTenureFreeEntry){
compactReason = COMPACT_LARGE;
goto compactionReqd;
}
}
}
#endif /* OMR_GC_MODRON_SCAVENGER */
/* If this is an aggressive collect and the last collect did not compact then
* make sure we do this time.
*/
if (gcCode.isAggressiveGC() &&
(_extensions->globalGCStats.compactStats._lastHeapCompaction + 1 < _extensions->globalGCStats.gcCount)) {
compactReason = COMPACT_AGGRESSIVE;
goto compactionReqd;
}
#if defined(OMR_GC_THREAD_LOCAL_HEAP)
/* Now check for signs of fragmentation by checking the average size of TLH
* allocated since the last global collection
*/
if (allocStats->_tlhRefreshCountFresh > 0) {
Assert_MM_true(allocStats->_tlhAllocatedFresh > 0);
}
/* Calculate total bytes allocated in tenure area since last global collection */
totalBytesAllocated = allocStats->_allocationBytes + allocStats->_tlhAllocatedFresh;
/* ..and what percentage of allocations were tlh's */
tlhPercent = allocStats->_tlhRefreshCountFresh > 0 ? (uintptr_t) (((uint64_t) allocStats->_tlhAllocatedFresh * 100) / (uint64_t) totalBytesAllocated) : 0;
/* Check at least 50% of free space at end of last GC has been consumed by tlh allocations */
if( tlhPercent > 50 ) {
/* Calculate average size of tlh allocated since tenure area last collected */
uintptr_t avgTlh= allocStats->_tlhAllocatedFresh / allocStats->_tlhRefreshCountFresh;
/* Compaction trigger is a multiple of the minimum tlh size */
uintptr_t compaction_trigger_avgtlh= _extensions->tlhMinimumSize * MINIMUM_TLHSIZE_MULTIPLIER;
if(avgTlh < compaction_trigger_avgtlh) {
compactReason = COMPACT_FRAGMENTED;
goto compactionReqd;
}
}
#endif
/* We know if we get here we know:
* o we can meet the allocation request out of available free memory, and
* o the heap is not fragmented
*
* So if we are not fully expanded but we are low on storage there is little point doing
* a compaction, we just need to expand. However, if we are fully expanded but low
* on free memory there is little more we can do to avoid OOM at this point other than
* compact to get as much free memory as possible.
*/
if ( activeSubspaceMaxExpansionInSpace == 0) {
uintptr_t oldFree = heap->getApproximateActiveFreeMemorySize(MEMORY_TYPE_OLD);
uintptr_t oldSize = heap->getActiveMemorySize(MEMORY_TYPE_OLD);
uintptr_t desperateFree = (oldSize / OLDFREE_DESPERATE_RATIO_DIVISOR) * OLDFREE_DESPERATE_RATIO_MULTIPLIER;
/* Is heap space getting tight? */
if(oldFree < desperateFree) {
compactReason = COMPACT_AVOID_DESPERATE;
goto compactionReqd;
}
if(oldFree < OLDFREE_INSUFFICIENT ) {
compactReason = COMPACT_MEMORY_INSUFFICIENT;
goto compactionReqd;
}
}
{
/* Tenure space dark matter trigger */
MM_MemorySubSpace *memorySubSpace = heap->getDefaultMemorySpace()->getTenureMemorySubSpace();
uintptr_t totalSize = memorySubSpace->getActiveMemorySize();
MM_MemoryPool *memoryPool= memorySubSpace->getMemoryPool();
uintptr_t darkMatterBytes = 0;
if (!_extensions->concurrentSweep) {
darkMatterBytes = memoryPool->getDarkMatterBytes();
}
uintptr_t freeMemorySize = memoryPool->getActualFreeMemorySize();
/* Consider the trigger only if heap fully expanded */
if (heap->getMemorySize() == heap->getMaximumMemorySize()) {
float darkMatterRatio = ((float)darkMatterBytes)/((float)freeMemorySize + (float)totalSize / 2);
if (darkMatterRatio > _extensions->getDarkMatterCompactThreshold()) {
compactReason = COMPACT_MICRO_FRAG;
goto compactionReqd;
}
}
#if defined(OMR_GC_IDLE_HEAP_MANAGER)
if ((J9MMCONSTANT_EXPLICIT_GC_IDLE_GC == gcCode.getCode()) && (_extensions->gcOnIdle)){
MM_LargeObjectAllocateStats *stats = memoryPool->getLargeObjectAllocateStats();
uintptr_t pageSize = heap->getPageSize();
uintptr_t reusableFreeMemory = stats->getPageAlignedFreeMemory(pageSize);
uintptr_t memoryFragmentationDiff = freeMemorySize - reusableFreeMemory;
uintptr_t totalFragmentation = memoryFragmentationDiff + darkMatterBytes;
float totalFragmentationRatio = ((float)totalFragmentation)/((float)freeMemorySize + (float)totalSize / 2);
Trc_ParallelGlobalGC_shouldCompactThisCycle(env->getLanguageVMThread(), totalFragmentationRatio, _extensions->gcOnIdleCompactThreshold);
if (totalFragmentationRatio > _extensions->gcOnIdleCompactThreshold) {
compactReason = COMPACT_PAGE;
goto compactionReqd;
}
}
#endif /* OMR_GC_IDLE_HEAP_MANAGER */
}
nocompact:
/* Compaction not required or prevented from running */
_extensions->globalGCStats.compactStats._compactReason = compactReason;
_extensions->globalGCStats.compactStats._compactPreventedReason = compactPreventedReason;
return false;
compactionReqd:
compactPreventedReason = _delegate.checkIfCompactionShouldBePrevented(env);
if (COMPACT_PREVENTED_NONE != compactPreventedReason) {
goto nocompact;
}
_extensions->globalGCStats.compactStats._compactReason = compactReason;
_extensions->globalGCStats.compactStats._compactPreventedReason = compactPreventedReason;
return true;
}
/**
* Determine if a compact is required to aid contraction.
* A heap contraction is due so decide whether a compaction would be
* beneficial before we attempt to contract the heap.
* @return true if a compaction is required, false otherwise.
*/
bool
MM_ParallelGlobalGC::compactRequiredBeforeHeapContraction(MM_EnvironmentBase *env, MM_AllocateDescription *allocDescription, uintptr_t contractionSize)
{
uintptr_t lengthLastFree;
/* Assume no compaction is required until we prove otherwise*/
/* if the user specified -XnoCompact then we're done */
if (_extensions->noCompactOnGlobalGC) {
return false;
}
if (env->_cycleState->_gcCode.isExplicitGC() && _extensions->nocompactOnSystemGC){
/* if the user specified -XnocompactexplicitGC then we don't compact*/
return false;
}
uintptr_t actualSoftMx = _extensions->heap->getActualSoftMxSize(env);
if(0 != actualSoftMx) {
if(actualSoftMx < _extensions->heap->getActiveMemorySize()) {
/* a softmx has been set that's less than the current heap size - it's
* highly likely we'll need to compact in order to meet the contract, so do it */
goto compactionReqd;
}
}
/* We should compact to assist a later contraction if:
*
* - no compaction performed this GC (if we get here then we have decided not to compact for other
* reasons so non eed to check that)
* - the last GC did not do a shrink and compact
* - there is no free chunk at the end of the heap or the chunk at the end of the heap
* is less than 10% of required shrink size
*/
if((_extensions->globalGCStats.compactStats._lastHeapCompaction + 1 == _extensions->globalGCStats.gcCount) &&
(_extensions->heap->getResizeStats()->getLastHeapContractionGCCount() + 1 == _extensions->globalGCStats.gcCount)) {
return false;
}
/* Determine length of free chunk at top of heap */
/* Note: We know based on the collector that this is a single contiguous area */
lengthLastFree = env->_cycleState->_activeSubSpace->getAvailableContractionSize(env, allocDescription);
/* If chunk at end of heap is free then check its at least minimumContractionRatio percent of the
* requested contraction amount
*/
if (lengthLastFree > 0) {
uintptr_t minContractSize = (contractionSize / MINIMUM_CONTRACTION_RATIO_DIVISOR)
* _extensions->minimumContractionRatio;
if (lengthLastFree > minContractSize) {
return false;
}
}
compactionReqd:
_extensions->globalGCStats.compactStats._compactPreventedReason = _delegate.checkIfCompactionShouldBePrevented(env);
if (COMPACT_PREVENTED_NONE != _extensions->globalGCStats.compactStats._compactPreventedReason) {
return false;
}
/* If we get here we need to compact to assist the contraction.
* Remember why for verbose
*/
_extensions->globalGCStats.compactStats._compactReason = COMPACT_CONTRACT;
return true;
}
#endif /* defined(OMR_GC_MODRON_COMPACTION) */
void
MM_ParallelGlobalGC::sweep(MM_EnvironmentBase *env, MM_AllocateDescription *allocDescription, bool rebuildMarkBits)
{
OMRPORT_ACCESS_FROM_OMRPORT(env->getPortLibrary());
MM_SweepStats *sweepStats = &_extensions->globalGCStats.sweepStats;
reportSweepStart(env);
sweepStats->_startTime = omrtime_hires_clock();
mainThreadSweepStart(env, allocDescription);
if (_extensions->processLargeAllocateStats) {
processLargeAllocateStatsAfterSweep(env);
}
MM_MemorySubSpace *activeSubSpace = env->_cycleState->_activeSubSpace;
bool isExplicitGC = env->_cycleState->_gcCode.isExplicitGC();
#if defined(OMR_GC_MODRON_COMPACTION)
/* Decide is a compaction is required - this decision must be made after we sweep since we use the largestFreeEntrySize, as changed by sweep, to determine if a compaction should be done */
_compactThisCycle = shouldCompactThisCycle(env, allocDescription, activeSubSpace->maxExpansionInSpace(env), env->_cycleState->_gcCode);
if (!_compactThisCycle)
#endif /* OMR_GC_MODRON_COMPACTION */
{
/* Decide whether we need to expand or shrink the heap. If the decision is to
* shrink, we may need to force a compaction to assist the contraction.
*/
activeSubSpace->checkResize(env, allocDescription, isExplicitGC);
}
/* If we need to completely rebuild the freeelist (impending compaction or contraction), then do it */
SweepCompletionReason reason = NOT_REQUIRED;
if(completeFreelistRebuildRequired(env, &reason)) {
mainThreadSweepComplete(env, reason);
#if defined(OMR_GC_MODRON_COMPACTION)
if (!_compactThisCycle)
#endif /* OMR_GC_MODRON_COMPACTION */
{
/* We now have accurate free space statistics so recalculate any expand/contract amount
* as it will no doubt have changed
*/
activeSubSpace->checkResize(env, allocDescription, isExplicitGC);
}
}
#if defined(OMR_GC_MODRON_COMPACTION)
if (0 != activeSubSpace->getContractionSize()) {
_compactThisCycle = compactRequiredBeforeHeapContraction(env, allocDescription, activeSubSpace->getContractionSize());
}
#endif /* OMR_GC_MODRON_COMPACTION */
sweepStats->_endTime = omrtime_hires_clock();
reportSweepEnd(env);
}
bool
MM_ParallelGlobalGC::completeFreelistRebuildRequired(MM_EnvironmentBase *env, SweepCompletionReason *reason)
{
*reason = NOT_REQUIRED;
MM_MemorySubSpace *activeSubSpace = env->_cycleState->_activeSubSpace;
#if defined(OMR_GC_MODRON_COMPACTION)
if (_compactThisCycle) {
*reason = COMPACTION_REQUIRED;
} else
#endif /* OMR_GC_MODRON_COMPACTION */
if (activeSubSpace->getActiveLOAMemorySize(MEMORY_TYPE_OLD) > 0 && 0 != activeSubSpace->getExpansionSize()) {
//todo remove once we sort out how to reallocate sweep chunks if heap expands
// after a concurrent sweep cycle has started but for now we need to complete sweep
// if current LOA size is > 0.
*reason = EXPANSION_REQUIRED;
} else if (0 != activeSubSpace->getContractionSize()) {
*reason = CONTRACTION_REQUIRED;
} else if (activeSubSpace->completeFreelistRebuildRequired(env)) {
*reason = LOA_RESIZE;
} else if (env->_cycleState->_gcCode.isExplicitGC()) {
*reason = SYSTEM_GC;
}
return (*reason == NOT_REQUIRED ? false : true);
}
void
MM_ParallelGlobalGC::markAll(MM_EnvironmentBase *env, bool initMarkMap)
{
OMRPORT_ACCESS_FROM_OMRPORT(env->getPortLibrary());
MM_MarkStats *markStats = &_extensions->globalGCStats.markStats;
reportMarkStart(env);
markStats->_startTime = omrtime_hires_clock();
_markingScheme->mainSetupForGC(env);
if (env->_cycleState->_gcCode.isOutOfMemoryGC()) {
env->_cycleState->_referenceObjectOptions |= MM_CycleState::references_soft_as_weak;
}
/* run the mark */
MM_ParallelMarkTask markTask(env, _dispatcher, _markingScheme, initMarkMap, env->_cycleState);
_dispatcher->run(env, &markTask);
Assert_MM_true(_markingScheme->getWorkPackets()->isAllPacketsEmpty());
/* Do any post mark checks */
postMark(env);
_markingScheme->mainCleanupAfterGC(env);
markStats->_endTime = omrtime_hires_clock();
reportMarkEnd(env);
}
void
MM_ParallelGlobalGC::mainThreadSweepStart(MM_EnvironmentBase *env, MM_AllocateDescription *allocDescription)
{
_sweepScheme->setMarkMap(_markingScheme->getMarkMap());
_sweepScheme->sweepForMinimumSize(env, env->_cycleState->_activeSubSpace, allocDescription);
}
void
MM_ParallelGlobalGC::mainThreadSweepComplete(MM_EnvironmentBase *env, SweepCompletionReason reason)
{
_sweepScheme->completeSweep(env, reason);
}
#if defined(OMR_GC_MODRON_COMPACTION)
void
MM_ParallelGlobalGC::mainThreadCompact(MM_EnvironmentBase *env, MM_AllocateDescription *allocDescription, bool rebuildMarkBits)
{
OMRPORT_ACCESS_FROM_OMRPORT(env->getPortLibrary());
MM_CompactStats *compactStats = &_extensions->globalGCStats.compactStats;
MM_MarkMap *markMap = _markingScheme->getMarkMap();
markMap->setMarkMapValid(false);
_compactScheme->setMarkMap(markMap);
reportCompactStart(env);
compactStats->_startTime = omrtime_hires_clock();
MM_ParallelCompactTask compactTask(env, _dispatcher, _compactScheme, rebuildMarkBits, env->_cycleState->_gcCode.shouldAggressivelyCompact());
_dispatcher->run(env, &compactTask);
compactStats->_endTime = omrtime_hires_clock();
reportCompactEnd(env);
/* Remember the gc count of the last compaction */
_extensions->globalGCStats.compactStats._lastHeapCompaction= _extensions->globalGCStats.gcCount;
}