blob: af7acbc45bd947e287776f93b9b02895e2d63b8b [file] [log] [blame]
/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "concurrent_copying.h"
#include "art_field-inl.h"
#include "base/stl_util.h"
#include "debugger.h"
#include "gc/accounting/heap_bitmap-inl.h"
#include "gc/accounting/space_bitmap-inl.h"
#include "gc/reference_processor.h"
#include "gc/space/image_space.h"
#include "gc/space/space-inl.h"
#include "intern_table.h"
#include "mirror/class-inl.h"
#include "mirror/object-inl.h"
#include "scoped_thread_state_change.h"
#include "thread-inl.h"
#include "thread_list.h"
#include "well_known_classes.h"
namespace art {
namespace gc {
namespace collector {
static constexpr size_t kDefaultGcMarkStackSize = 2 * MB;
ConcurrentCopying::ConcurrentCopying(Heap* heap, const std::string& name_prefix)
: GarbageCollector(heap,
name_prefix + (name_prefix.empty() ? "" : " ") +
"concurrent copying + mark sweep"),
region_space_(nullptr), gc_barrier_(new Barrier(0)),
gc_mark_stack_(accounting::ObjectStack::Create("concurrent copying gc mark stack",
kDefaultGcMarkStackSize,
kDefaultGcMarkStackSize)),
mark_stack_lock_("concurrent copying mark stack lock", kMarkSweepMarkStackLock),
thread_running_gc_(nullptr),
is_marking_(false), is_active_(false), is_asserting_to_space_invariant_(false),
heap_mark_bitmap_(nullptr), live_stack_freeze_size_(0), mark_stack_mode_(kMarkStackModeOff),
weak_ref_access_enabled_(true),
skipped_blocks_lock_("concurrent copying bytes blocks lock", kMarkSweepMarkStackLock),
rb_table_(heap_->GetReadBarrierTable()),
force_evacuate_all_(false) {
static_assert(space::RegionSpace::kRegionSize == accounting::ReadBarrierTable::kRegionSize,
"The region space size and the read barrier table region size must match");
cc_heap_bitmap_.reset(new accounting::HeapBitmap(heap));
Thread* self = Thread::Current();
{
ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
// Cache this so that we won't have to lock heap_bitmap_lock_ in
// Mark() which could cause a nested lock on heap_bitmap_lock_
// when GC causes a RB while doing GC or a lock order violation
// (class_linker_lock_ and heap_bitmap_lock_).
heap_mark_bitmap_ = heap->GetMarkBitmap();
}
{
MutexLock mu(self, mark_stack_lock_);
for (size_t i = 0; i < kMarkStackPoolSize; ++i) {
accounting::AtomicStack<mirror::Object>* mark_stack =
accounting::AtomicStack<mirror::Object>::Create(
"thread local mark stack", kMarkStackSize, kMarkStackSize);
pooled_mark_stacks_.push_back(mark_stack);
}
}
}
void ConcurrentCopying::MarkHeapReference(mirror::HeapReference<mirror::Object>* from_ref) {
// Used for preserving soft references, should be OK to not have a CAS here since there should be
// no other threads which can trigger read barriers on the same referent during reference
// processing.
from_ref->Assign(Mark(from_ref->AsMirrorPtr()));
DCHECK(!from_ref->IsNull());
}
ConcurrentCopying::~ConcurrentCopying() {
STLDeleteElements(&pooled_mark_stacks_);
}
void ConcurrentCopying::RunPhases() {
CHECK(kUseBakerReadBarrier || kUseTableLookupReadBarrier);
CHECK(!is_active_);
is_active_ = true;
Thread* self = Thread::Current();
thread_running_gc_ = self;
Locks::mutator_lock_->AssertNotHeld(self);
{
ReaderMutexLock mu(self, *Locks::mutator_lock_);
InitializePhase();
}
FlipThreadRoots();
{
ReaderMutexLock mu(self, *Locks::mutator_lock_);
MarkingPhase();
}
// Verify no from space refs. This causes a pause.
if (kEnableNoFromSpaceRefsVerification || kIsDebugBuild) {
TimingLogger::ScopedTiming split("(Paused)VerifyNoFromSpaceReferences", GetTimings());
ScopedPause pause(this);
CheckEmptyMarkStack();
if (kVerboseMode) {
LOG(INFO) << "Verifying no from-space refs";
}
VerifyNoFromSpaceReferences();
if (kVerboseMode) {
LOG(INFO) << "Done verifying no from-space refs";
}
CheckEmptyMarkStack();
}
{
ReaderMutexLock mu(self, *Locks::mutator_lock_);
ReclaimPhase();
}
FinishPhase();
CHECK(is_active_);
is_active_ = false;
thread_running_gc_ = nullptr;
}
void ConcurrentCopying::BindBitmaps() {
Thread* self = Thread::Current();
WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
// Mark all of the spaces we never collect as immune.
for (const auto& space : heap_->GetContinuousSpaces()) {
if (space->GetGcRetentionPolicy() == space::kGcRetentionPolicyNeverCollect ||
space->GetGcRetentionPolicy() == space::kGcRetentionPolicyFullCollect) {
CHECK(space->IsZygoteSpace() || space->IsImageSpace());
immune_spaces_.AddSpace(space);
const char* bitmap_name = space->IsImageSpace() ? "cc image space bitmap" :
"cc zygote space bitmap";
// TODO: try avoiding using bitmaps for image/zygote to save space.
accounting::ContinuousSpaceBitmap* bitmap =
accounting::ContinuousSpaceBitmap::Create(bitmap_name, space->Begin(), space->Capacity());
cc_heap_bitmap_->AddContinuousSpaceBitmap(bitmap);
cc_bitmaps_.push_back(bitmap);
} else if (space == region_space_) {
accounting::ContinuousSpaceBitmap* bitmap =
accounting::ContinuousSpaceBitmap::Create("cc region space bitmap",
space->Begin(), space->Capacity());
cc_heap_bitmap_->AddContinuousSpaceBitmap(bitmap);
cc_bitmaps_.push_back(bitmap);
region_space_bitmap_ = bitmap;
}
}
}
void ConcurrentCopying::InitializePhase() {
TimingLogger::ScopedTiming split("InitializePhase", GetTimings());
if (kVerboseMode) {
LOG(INFO) << "GC InitializePhase";
LOG(INFO) << "Region-space : " << reinterpret_cast<void*>(region_space_->Begin()) << "-"
<< reinterpret_cast<void*>(region_space_->Limit());
}
CheckEmptyMarkStack();
immune_spaces_.Reset();
bytes_moved_.StoreRelaxed(0);
objects_moved_.StoreRelaxed(0);
if (GetCurrentIteration()->GetGcCause() == kGcCauseExplicit ||
GetCurrentIteration()->GetGcCause() == kGcCauseForNativeAlloc ||
GetCurrentIteration()->GetClearSoftReferences()) {
force_evacuate_all_ = true;
} else {
force_evacuate_all_ = false;
}
BindBitmaps();
if (kVerboseMode) {
LOG(INFO) << "force_evacuate_all=" << force_evacuate_all_;
LOG(INFO) << "Largest immune region: " << immune_spaces_.GetLargestImmuneRegion().Begin()
<< "-" << immune_spaces_.GetLargestImmuneRegion().End();
for (space::ContinuousSpace* space : immune_spaces_.GetSpaces()) {
LOG(INFO) << "Immune space: " << *space;
}
LOG(INFO) << "GC end of InitializePhase";
}
}
// Used to switch the thread roots of a thread from from-space refs to to-space refs.
class ThreadFlipVisitor : public Closure {
public:
ThreadFlipVisitor(ConcurrentCopying* concurrent_copying, bool use_tlab)
: concurrent_copying_(concurrent_copying), use_tlab_(use_tlab) {
}
virtual void Run(Thread* thread) OVERRIDE SHARED_REQUIRES(Locks::mutator_lock_) {
// Note: self is not necessarily equal to thread since thread may be suspended.
Thread* self = Thread::Current();
CHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc)
<< thread->GetState() << " thread " << thread << " self " << self;
thread->SetIsGcMarking(true);
if (use_tlab_ && thread->HasTlab()) {
if (ConcurrentCopying::kEnableFromSpaceAccountingCheck) {
// This must come before the revoke.
size_t thread_local_objects = thread->GetThreadLocalObjectsAllocated();
concurrent_copying_->region_space_->RevokeThreadLocalBuffers(thread);
reinterpret_cast<Atomic<size_t>*>(&concurrent_copying_->from_space_num_objects_at_first_pause_)->
FetchAndAddSequentiallyConsistent(thread_local_objects);
} else {
concurrent_copying_->region_space_->RevokeThreadLocalBuffers(thread);
}
}
if (kUseThreadLocalAllocationStack) {
thread->RevokeThreadLocalAllocationStack();
}
ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
thread->VisitRoots(concurrent_copying_);
concurrent_copying_->GetBarrier().Pass(self);
}
private:
ConcurrentCopying* const concurrent_copying_;
const bool use_tlab_;
};
// Called back from Runtime::FlipThreadRoots() during a pause.
class FlipCallback : public Closure {
public:
explicit FlipCallback(ConcurrentCopying* concurrent_copying)
: concurrent_copying_(concurrent_copying) {
}
virtual void Run(Thread* thread) OVERRIDE REQUIRES(Locks::mutator_lock_) {
ConcurrentCopying* cc = concurrent_copying_;
TimingLogger::ScopedTiming split("(Paused)FlipCallback", cc->GetTimings());
// Note: self is not necessarily equal to thread since thread may be suspended.
Thread* self = Thread::Current();
CHECK(thread == self);
Locks::mutator_lock_->AssertExclusiveHeld(self);
cc->region_space_->SetFromSpace(cc->rb_table_, cc->force_evacuate_all_);
cc->SwapStacks();
if (ConcurrentCopying::kEnableFromSpaceAccountingCheck) {
cc->RecordLiveStackFreezeSize(self);
cc->from_space_num_objects_at_first_pause_ = cc->region_space_->GetObjectsAllocated();
cc->from_space_num_bytes_at_first_pause_ = cc->region_space_->GetBytesAllocated();
}
cc->is_marking_ = true;
cc->mark_stack_mode_.StoreRelaxed(ConcurrentCopying::kMarkStackModeThreadLocal);
if (UNLIKELY(Runtime::Current()->IsActiveTransaction())) {
CHECK(Runtime::Current()->IsAotCompiler());
TimingLogger::ScopedTiming split2("(Paused)VisitTransactionRoots", cc->GetTimings());
Runtime::Current()->VisitTransactionRoots(cc);
}
}
private:
ConcurrentCopying* const concurrent_copying_;
};
// Switch threads that from from-space to to-space refs. Forward/mark the thread roots.
void ConcurrentCopying::FlipThreadRoots() {
TimingLogger::ScopedTiming split("FlipThreadRoots", GetTimings());
if (kVerboseMode) {
LOG(INFO) << "time=" << region_space_->Time();
region_space_->DumpNonFreeRegions(LOG(INFO));
}
Thread* self = Thread::Current();
Locks::mutator_lock_->AssertNotHeld(self);
gc_barrier_->Init(self, 0);
ThreadFlipVisitor thread_flip_visitor(this, heap_->use_tlab_);
FlipCallback flip_callback(this);
heap_->ThreadFlipBegin(self); // Sync with JNI critical calls.
size_t barrier_count = Runtime::Current()->FlipThreadRoots(
&thread_flip_visitor, &flip_callback, this);
heap_->ThreadFlipEnd(self);
{
ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun);
gc_barrier_->Increment(self, barrier_count);
}
is_asserting_to_space_invariant_ = true;
QuasiAtomic::ThreadFenceForConstructor();
if (kVerboseMode) {
LOG(INFO) << "time=" << region_space_->Time();
region_space_->DumpNonFreeRegions(LOG(INFO));
LOG(INFO) << "GC end of FlipThreadRoots";
}
}
void ConcurrentCopying::SwapStacks() {
heap_->SwapStacks();
}
void ConcurrentCopying::RecordLiveStackFreezeSize(Thread* self) {
WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
live_stack_freeze_size_ = heap_->GetLiveStack()->Size();
}
// Used to visit objects in the immune spaces.
class ConcurrentCopyingImmuneSpaceObjVisitor {
public:
explicit ConcurrentCopyingImmuneSpaceObjVisitor(ConcurrentCopying* cc)
: collector_(cc) {}
void operator()(mirror::Object* obj) const SHARED_REQUIRES(Locks::mutator_lock_)
SHARED_REQUIRES(Locks::heap_bitmap_lock_) {
DCHECK(obj != nullptr);
DCHECK(collector_->immune_spaces_.ContainsObject(obj));
accounting::ContinuousSpaceBitmap* cc_bitmap =
collector_->cc_heap_bitmap_->GetContinuousSpaceBitmap(obj);
DCHECK(cc_bitmap != nullptr)
<< "An immune space object must have a bitmap";
if (kIsDebugBuild) {
DCHECK(collector_->heap_->GetMarkBitmap()->Test(obj))
<< "Immune space object must be already marked";
}
// This may or may not succeed, which is ok.
if (kUseBakerReadBarrier) {
obj->AtomicSetReadBarrierPointer(ReadBarrier::WhitePtr(), ReadBarrier::GrayPtr());
}
if (cc_bitmap->AtomicTestAndSet(obj)) {
// Already marked. Do nothing.
} else {
// Newly marked. Set the gray bit and push it onto the mark stack.
CHECK(!kUseBakerReadBarrier || obj->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
collector_->PushOntoMarkStack(obj);
}
}
private:
ConcurrentCopying* const collector_;
};
class EmptyCheckpoint : public Closure {
public:
explicit EmptyCheckpoint(ConcurrentCopying* concurrent_copying)
: concurrent_copying_(concurrent_copying) {
}
virtual void Run(Thread* thread) OVERRIDE NO_THREAD_SAFETY_ANALYSIS {
// Note: self is not necessarily equal to thread since thread may be suspended.
Thread* self = Thread::Current();
CHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc)
<< thread->GetState() << " thread " << thread << " self " << self;
// If thread is a running mutator, then act on behalf of the garbage collector.
// See the code in ThreadList::RunCheckpoint.
concurrent_copying_->GetBarrier().Pass(self);
}
private:
ConcurrentCopying* const concurrent_copying_;
};
// Concurrently mark roots that are guarded by read barriers and process the mark stack.
void ConcurrentCopying::MarkingPhase() {
TimingLogger::ScopedTiming split("MarkingPhase", GetTimings());
if (kVerboseMode) {
LOG(INFO) << "GC MarkingPhase";
}
CHECK(weak_ref_access_enabled_);
{
// Mark the image root. The WB-based collectors do not need to
// scan the image objects from roots by relying on the card table,
// but it's necessary for the RB to-space invariant to hold.
TimingLogger::ScopedTiming split1("VisitImageRoots", GetTimings());
for (space::ContinuousSpace* space : heap_->GetContinuousSpaces()) {
if (space->IsImageSpace()) {
gc::space::ImageSpace* image = space->AsImageSpace();
if (image != nullptr) {
mirror::ObjectArray<mirror::Object>* image_root = image->GetImageHeader().GetImageRoots();
mirror::Object* marked_image_root = Mark(image_root);
CHECK_EQ(image_root, marked_image_root) << "An image object does not move";
if (ReadBarrier::kEnableToSpaceInvariantChecks) {
AssertToSpaceInvariant(nullptr, MemberOffset(0), marked_image_root);
}
}
}
}
}
{
TimingLogger::ScopedTiming split2("VisitConcurrentRoots", GetTimings());
Runtime::Current()->VisitConcurrentRoots(this, kVisitRootFlagAllRoots);
}
{
// TODO: don't visit the transaction roots if it's not active.
TimingLogger::ScopedTiming split5("VisitNonThreadRoots", GetTimings());
Runtime::Current()->VisitNonThreadRoots(this);
}
// Immune spaces.
for (auto& space : immune_spaces_.GetSpaces()) {
DCHECK(space->IsImageSpace() || space->IsZygoteSpace());
accounting::ContinuousSpaceBitmap* live_bitmap = space->GetLiveBitmap();
ConcurrentCopyingImmuneSpaceObjVisitor visitor(this);
live_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(space->Begin()),
reinterpret_cast<uintptr_t>(space->Limit()),
visitor);
}
Thread* self = Thread::Current();
{
TimingLogger::ScopedTiming split7("ProcessMarkStack", GetTimings());
// We transition through three mark stack modes (thread-local, shared, GC-exclusive). The
// primary reasons are the fact that we need to use a checkpoint to process thread-local mark
// stacks, but after we disable weak refs accesses, we can't use a checkpoint due to a deadlock
// issue because running threads potentially blocking at WaitHoldingLocks, and that once we
// reach the point where we process weak references, we can avoid using a lock when accessing
// the GC mark stack, which makes mark stack processing more efficient.
// Process the mark stack once in the thread local stack mode. This marks most of the live
// objects, aside from weak ref accesses with read barriers (Reference::GetReferent() and system
// weaks) that may happen concurrently while we processing the mark stack and newly mark/gray
// objects and push refs on the mark stack.
ProcessMarkStack();
// Switch to the shared mark stack mode. That is, revoke and process thread-local mark stacks
// for the last time before transitioning to the shared mark stack mode, which would process new
// refs that may have been concurrently pushed onto the mark stack during the ProcessMarkStack()
// call above. At the same time, disable weak ref accesses using a per-thread flag. It's
// important to do these together in a single checkpoint so that we can ensure that mutators
// won't newly gray objects and push new refs onto the mark stack due to weak ref accesses and
// mutators safely transition to the shared mark stack mode (without leaving unprocessed refs on
// the thread-local mark stacks), without a race. This is why we use a thread-local weak ref
// access flag Thread::tls32_.weak_ref_access_enabled_ instead of the global ones.
SwitchToSharedMarkStackMode();
CHECK(!self->GetWeakRefAccessEnabled());
// Now that weak refs accesses are disabled, once we exhaust the shared mark stack again here
// (which may be non-empty if there were refs found on thread-local mark stacks during the above
// SwitchToSharedMarkStackMode() call), we won't have new refs to process, that is, mutators
// (via read barriers) have no way to produce any more refs to process. Marking converges once
// before we process weak refs below.
ProcessMarkStack();
CheckEmptyMarkStack();
// Switch to the GC exclusive mark stack mode so that we can process the mark stack without a
// lock from this point on.
SwitchToGcExclusiveMarkStackMode();
CheckEmptyMarkStack();
if (kVerboseMode) {
LOG(INFO) << "ProcessReferences";
}
// Process weak references. This may produce new refs to process and have them processed via
// ProcessMarkStack (in the GC exclusive mark stack mode).
ProcessReferences(self);
CheckEmptyMarkStack();
if (kVerboseMode) {
LOG(INFO) << "SweepSystemWeaks";
}
SweepSystemWeaks(self);
if (kVerboseMode) {
LOG(INFO) << "SweepSystemWeaks done";
}
// Process the mark stack here one last time because the above SweepSystemWeaks() call may have
// marked some objects (strings alive) as hash_set::Erase() can call the hash function for
// arbitrary elements in the weak intern table in InternTable::Table::SweepWeaks().
ProcessMarkStack();
CheckEmptyMarkStack();
// Re-enable weak ref accesses.
ReenableWeakRefAccess(self);
// Free data for class loaders that we unloaded.
Runtime::Current()->GetClassLinker()->CleanupClassLoaders();
// Marking is done. Disable marking.
DisableMarking();
CheckEmptyMarkStack();
}
CHECK(weak_ref_access_enabled_);
if (kVerboseMode) {
LOG(INFO) << "GC end of MarkingPhase";
}
}
void ConcurrentCopying::ReenableWeakRefAccess(Thread* self) {
if (kVerboseMode) {
LOG(INFO) << "ReenableWeakRefAccess";
}
weak_ref_access_enabled_.StoreRelaxed(true); // This is for new threads.
QuasiAtomic::ThreadFenceForConstructor();
// Iterate all threads (don't need to or can't use a checkpoint) and re-enable weak ref access.
{
MutexLock mu(self, *Locks::thread_list_lock_);
std::list<Thread*> thread_list = Runtime::Current()->GetThreadList()->GetList();
for (Thread* thread : thread_list) {
thread->SetWeakRefAccessEnabled(true);
}
}
// Unblock blocking threads.
GetHeap()->GetReferenceProcessor()->BroadcastForSlowPath(self);
Runtime::Current()->BroadcastForNewSystemWeaks();
}
class DisableMarkingCheckpoint : public Closure {
public:
explicit DisableMarkingCheckpoint(ConcurrentCopying* concurrent_copying)
: concurrent_copying_(concurrent_copying) {
}
void Run(Thread* thread) OVERRIDE NO_THREAD_SAFETY_ANALYSIS {
// Note: self is not necessarily equal to thread since thread may be suspended.
Thread* self = Thread::Current();
DCHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc)
<< thread->GetState() << " thread " << thread << " self " << self;
// Disable the thread-local is_gc_marking flag.
// Note a thread that has just started right before this checkpoint may have already this flag
// set to false, which is ok.
thread->SetIsGcMarking(false);
// If thread is a running mutator, then act on behalf of the garbage collector.
// See the code in ThreadList::RunCheckpoint.
concurrent_copying_->GetBarrier().Pass(self);
}
private:
ConcurrentCopying* const concurrent_copying_;
};
void ConcurrentCopying::IssueDisableMarkingCheckpoint() {
Thread* self = Thread::Current();
DisableMarkingCheckpoint check_point(this);
ThreadList* thread_list = Runtime::Current()->GetThreadList();
gc_barrier_->Init(self, 0);
size_t barrier_count = thread_list->RunCheckpoint(&check_point);
// If there are no threads to wait which implies that all the checkpoint functions are finished,
// then no need to release the mutator lock.
if (barrier_count == 0) {
return;
}
// Release locks then wait for all mutator threads to pass the barrier.
Locks::mutator_lock_->SharedUnlock(self);
{
ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun);
gc_barrier_->Increment(self, barrier_count);
}
Locks::mutator_lock_->SharedLock(self);
}
void ConcurrentCopying::DisableMarking() {
// Change the global is_marking flag to false. Do a fence before doing a checkpoint to update the
// thread-local flags so that a new thread starting up will get the correct is_marking flag.
is_marking_ = false;
QuasiAtomic::ThreadFenceForConstructor();
// Use a checkpoint to turn off the thread-local is_gc_marking flags and to ensure no threads are
// still in the middle of a read barrier which may have a from-space ref cached in a local
// variable.
IssueDisableMarkingCheckpoint();
if (kUseTableLookupReadBarrier) {
heap_->rb_table_->ClearAll();
DCHECK(heap_->rb_table_->IsAllCleared());
}
is_mark_stack_push_disallowed_.StoreSequentiallyConsistent(1);
mark_stack_mode_.StoreSequentiallyConsistent(kMarkStackModeOff);
}
void ConcurrentCopying::IssueEmptyCheckpoint() {
Thread* self = Thread::Current();
EmptyCheckpoint check_point(this);
ThreadList* thread_list = Runtime::Current()->GetThreadList();
gc_barrier_->Init(self, 0);
size_t barrier_count = thread_list->RunCheckpoint(&check_point);
// If there are no threads to wait which implys that all the checkpoint functions are finished,
// then no need to release the mutator lock.
if (barrier_count == 0) {
return;
}
// Release locks then wait for all mutator threads to pass the barrier.
Locks::mutator_lock_->SharedUnlock(self);
{
ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun);
gc_barrier_->Increment(self, barrier_count);
}
Locks::mutator_lock_->SharedLock(self);
}
void ConcurrentCopying::ExpandGcMarkStack() {
DCHECK(gc_mark_stack_->IsFull());
const size_t new_size = gc_mark_stack_->Capacity() * 2;
std::vector<StackReference<mirror::Object>> temp(gc_mark_stack_->Begin(),
gc_mark_stack_->End());
gc_mark_stack_->Resize(new_size);
for (auto& ref : temp) {
gc_mark_stack_->PushBack(ref.AsMirrorPtr());
}
DCHECK(!gc_mark_stack_->IsFull());
}
void ConcurrentCopying::PushOntoMarkStack(mirror::Object* to_ref) {
CHECK_EQ(is_mark_stack_push_disallowed_.LoadRelaxed(), 0)
<< " " << to_ref << " " << PrettyTypeOf(to_ref);
Thread* self = Thread::Current(); // TODO: pass self as an argument from call sites?
CHECK(thread_running_gc_ != nullptr);
MarkStackMode mark_stack_mode = mark_stack_mode_.LoadRelaxed();
if (LIKELY(mark_stack_mode == kMarkStackModeThreadLocal)) {
if (LIKELY(self == thread_running_gc_)) {
// If GC-running thread, use the GC mark stack instead of a thread-local mark stack.
CHECK(self->GetThreadLocalMarkStack() == nullptr);
if (UNLIKELY(gc_mark_stack_->IsFull())) {
ExpandGcMarkStack();
}
gc_mark_stack_->PushBack(to_ref);
} else {
// Otherwise, use a thread-local mark stack.
accounting::AtomicStack<mirror::Object>* tl_mark_stack = self->GetThreadLocalMarkStack();
if (UNLIKELY(tl_mark_stack == nullptr || tl_mark_stack->IsFull())) {
MutexLock mu(self, mark_stack_lock_);
// Get a new thread local mark stack.
accounting::AtomicStack<mirror::Object>* new_tl_mark_stack;
if (!pooled_mark_stacks_.empty()) {
// Use a pooled mark stack.
new_tl_mark_stack = pooled_mark_stacks_.back();
pooled_mark_stacks_.pop_back();
} else {
// None pooled. Create a new one.
new_tl_mark_stack =
accounting::AtomicStack<mirror::Object>::Create(
"thread local mark stack", 4 * KB, 4 * KB);
}
DCHECK(new_tl_mark_stack != nullptr);
DCHECK(new_tl_mark_stack->IsEmpty());
new_tl_mark_stack->PushBack(to_ref);
self->SetThreadLocalMarkStack(new_tl_mark_stack);
if (tl_mark_stack != nullptr) {
// Store the old full stack into a vector.
revoked_mark_stacks_.push_back(tl_mark_stack);
}
} else {
tl_mark_stack->PushBack(to_ref);
}
}
} else if (mark_stack_mode == kMarkStackModeShared) {
// Access the shared GC mark stack with a lock.
MutexLock mu(self, mark_stack_lock_);
if (UNLIKELY(gc_mark_stack_->IsFull())) {
ExpandGcMarkStack();
}
gc_mark_stack_->PushBack(to_ref);
} else {
CHECK_EQ(static_cast<uint32_t>(mark_stack_mode),
static_cast<uint32_t>(kMarkStackModeGcExclusive))
<< "ref=" << to_ref
<< " self->gc_marking=" << self->GetIsGcMarking()
<< " cc->is_marking=" << is_marking_;
CHECK(self == thread_running_gc_)
<< "Only GC-running thread should access the mark stack "
<< "in the GC exclusive mark stack mode";
// Access the GC mark stack without a lock.
if (UNLIKELY(gc_mark_stack_->IsFull())) {
ExpandGcMarkStack();
}
gc_mark_stack_->PushBack(to_ref);
}
}
accounting::ObjectStack* ConcurrentCopying::GetAllocationStack() {
return heap_->allocation_stack_.get();
}
accounting::ObjectStack* ConcurrentCopying::GetLiveStack() {
return heap_->live_stack_.get();
}
// The following visitors are that used to verify that there's no
// references to the from-space left after marking.
class ConcurrentCopyingVerifyNoFromSpaceRefsVisitor : public SingleRootVisitor {
public:
explicit ConcurrentCopyingVerifyNoFromSpaceRefsVisitor(ConcurrentCopying* collector)
: collector_(collector) {}
void operator()(mirror::Object* ref) const
SHARED_REQUIRES(Locks::mutator_lock_) ALWAYS_INLINE {
if (ref == nullptr) {
// OK.
return;
}
collector_->AssertToSpaceInvariant(nullptr, MemberOffset(0), ref);
if (kUseBakerReadBarrier) {
if (collector_->RegionSpace()->IsInToSpace(ref)) {
CHECK(ref->GetReadBarrierPointer() == nullptr)
<< "To-space ref " << ref << " " << PrettyTypeOf(ref)
<< " has non-white rb_ptr " << ref->GetReadBarrierPointer();
} else {
CHECK(ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr() ||
(ref->GetReadBarrierPointer() == ReadBarrier::WhitePtr() &&
collector_->IsOnAllocStack(ref)))
<< "Non-moving/unevac from space ref " << ref << " " << PrettyTypeOf(ref)
<< " has non-black rb_ptr " << ref->GetReadBarrierPointer()
<< " but isn't on the alloc stack (and has white rb_ptr)."
<< " Is it in the non-moving space="
<< (collector_->GetHeap()->GetNonMovingSpace()->HasAddress(ref));
}
}
}
void VisitRoot(mirror::Object* root, const RootInfo& info ATTRIBUTE_UNUSED)
OVERRIDE SHARED_REQUIRES(Locks::mutator_lock_) {
DCHECK(root != nullptr);
operator()(root);
}
private:
ConcurrentCopying* const collector_;
};
class ConcurrentCopyingVerifyNoFromSpaceRefsFieldVisitor {
public:
explicit ConcurrentCopyingVerifyNoFromSpaceRefsFieldVisitor(ConcurrentCopying* collector)
: collector_(collector) {}
void operator()(mirror::Object* obj, MemberOffset offset, bool is_static ATTRIBUTE_UNUSED) const
SHARED_REQUIRES(Locks::mutator_lock_) ALWAYS_INLINE {
mirror::Object* ref =
obj->GetFieldObject<mirror::Object, kDefaultVerifyFlags, kWithoutReadBarrier>(offset);
ConcurrentCopyingVerifyNoFromSpaceRefsVisitor visitor(collector_);
visitor(ref);
}
void operator()(mirror::Class* klass, mirror::Reference* ref) const
SHARED_REQUIRES(Locks::mutator_lock_) ALWAYS_INLINE {
CHECK(klass->IsTypeOfReferenceClass());
this->operator()(ref, mirror::Reference::ReferentOffset(), false);
}
void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const
SHARED_REQUIRES(Locks::mutator_lock_) {
if (!root->IsNull()) {
VisitRoot(root);
}
}
void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const
SHARED_REQUIRES(Locks::mutator_lock_) {
ConcurrentCopyingVerifyNoFromSpaceRefsVisitor visitor(collector_);
visitor(root->AsMirrorPtr());
}
private:
ConcurrentCopying* const collector_;
};
class ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor {
public:
explicit ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor(ConcurrentCopying* collector)
: collector_(collector) {}
void operator()(mirror::Object* obj) const
SHARED_REQUIRES(Locks::mutator_lock_) {
ObjectCallback(obj, collector_);
}
static void ObjectCallback(mirror::Object* obj, void *arg)
SHARED_REQUIRES(Locks::mutator_lock_) {
CHECK(obj != nullptr);
ConcurrentCopying* collector = reinterpret_cast<ConcurrentCopying*>(arg);
space::RegionSpace* region_space = collector->RegionSpace();
CHECK(!region_space->IsInFromSpace(obj)) << "Scanning object " << obj << " in from space";
ConcurrentCopyingVerifyNoFromSpaceRefsFieldVisitor visitor(collector);
obj->VisitReferences(visitor, visitor);
if (kUseBakerReadBarrier) {
if (collector->RegionSpace()->IsInToSpace(obj)) {
CHECK(obj->GetReadBarrierPointer() == nullptr)
<< "obj=" << obj << " non-white rb_ptr " << obj->GetReadBarrierPointer();
} else {
CHECK(obj->GetReadBarrierPointer() == ReadBarrier::BlackPtr() ||
(obj->GetReadBarrierPointer() == ReadBarrier::WhitePtr() &&
collector->IsOnAllocStack(obj)))
<< "Non-moving space/unevac from space ref " << obj << " " << PrettyTypeOf(obj)
<< " has non-black rb_ptr " << obj->GetReadBarrierPointer()
<< " but isn't on the alloc stack (and has white rb_ptr). Is it in the non-moving space="
<< (collector->GetHeap()->GetNonMovingSpace()->HasAddress(obj));
}
}
}
private:
ConcurrentCopying* const collector_;
};
// Verify there's no from-space references left after the marking phase.
void ConcurrentCopying::VerifyNoFromSpaceReferences() {
Thread* self = Thread::Current();
DCHECK(Locks::mutator_lock_->IsExclusiveHeld(self));
// Verify all threads have is_gc_marking to be false
{
MutexLock mu(self, *Locks::thread_list_lock_);
std::list<Thread*> thread_list = Runtime::Current()->GetThreadList()->GetList();
for (Thread* thread : thread_list) {
CHECK(!thread->GetIsGcMarking());
}
}
ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor visitor(this);
// Roots.
{
ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
ConcurrentCopyingVerifyNoFromSpaceRefsVisitor ref_visitor(this);
Runtime::Current()->VisitRoots(&ref_visitor);
}
// The to-space.
region_space_->WalkToSpace(ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor::ObjectCallback,
this);
// Non-moving spaces.
{
WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
heap_->GetMarkBitmap()->Visit(visitor);
}
// The alloc stack.
{
ConcurrentCopyingVerifyNoFromSpaceRefsVisitor ref_visitor(this);
for (auto* it = heap_->allocation_stack_->Begin(), *end = heap_->allocation_stack_->End();
it < end; ++it) {
mirror::Object* const obj = it->AsMirrorPtr();
if (obj != nullptr && obj->GetClass() != nullptr) {
// TODO: need to call this only if obj is alive?
ref_visitor(obj);
visitor(obj);
}
}
}
// TODO: LOS. But only refs in LOS are classes.
}
// The following visitors are used to assert the to-space invariant.
class ConcurrentCopyingAssertToSpaceInvariantRefsVisitor {
public:
explicit ConcurrentCopyingAssertToSpaceInvariantRefsVisitor(ConcurrentCopying* collector)
: collector_(collector) {}
void operator()(mirror::Object* ref) const
SHARED_REQUIRES(Locks::mutator_lock_) ALWAYS_INLINE {
if (ref == nullptr) {
// OK.
return;
}
collector_->AssertToSpaceInvariant(nullptr, MemberOffset(0), ref);
}
private:
ConcurrentCopying* const collector_;
};
class ConcurrentCopyingAssertToSpaceInvariantFieldVisitor {
public:
explicit ConcurrentCopyingAssertToSpaceInvariantFieldVisitor(ConcurrentCopying* collector)
: collector_(collector) {}
void operator()(mirror::Object* obj, MemberOffset offset, bool is_static ATTRIBUTE_UNUSED) const
SHARED_REQUIRES(Locks::mutator_lock_) ALWAYS_INLINE {
mirror::Object* ref =
obj->GetFieldObject<mirror::Object, kDefaultVerifyFlags, kWithoutReadBarrier>(offset);
ConcurrentCopyingAssertToSpaceInvariantRefsVisitor visitor(collector_);
visitor(ref);
}
void operator()(mirror::Class* klass, mirror::Reference* ref ATTRIBUTE_UNUSED) const
SHARED_REQUIRES(Locks::mutator_lock_) ALWAYS_INLINE {
CHECK(klass->IsTypeOfReferenceClass());
}
void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const
SHARED_REQUIRES(Locks::mutator_lock_) {
if (!root->IsNull()) {
VisitRoot(root);
}
}
void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const
SHARED_REQUIRES(Locks::mutator_lock_) {
ConcurrentCopyingAssertToSpaceInvariantRefsVisitor visitor(collector_);
visitor(root->AsMirrorPtr());
}
private:
ConcurrentCopying* const collector_;
};
class ConcurrentCopyingAssertToSpaceInvariantObjectVisitor {
public:
explicit ConcurrentCopyingAssertToSpaceInvariantObjectVisitor(ConcurrentCopying* collector)
: collector_(collector) {}
void operator()(mirror::Object* obj) const
SHARED_REQUIRES(Locks::mutator_lock_) {
ObjectCallback(obj, collector_);
}
static void ObjectCallback(mirror::Object* obj, void *arg)
SHARED_REQUIRES(Locks::mutator_lock_) {
CHECK(obj != nullptr);
ConcurrentCopying* collector = reinterpret_cast<ConcurrentCopying*>(arg);
space::RegionSpace* region_space = collector->RegionSpace();
CHECK(!region_space->IsInFromSpace(obj)) << "Scanning object " << obj << " in from space";
collector->AssertToSpaceInvariant(nullptr, MemberOffset(0), obj);
ConcurrentCopyingAssertToSpaceInvariantFieldVisitor visitor(collector);
obj->VisitReferences(visitor, visitor);
}
private:
ConcurrentCopying* const collector_;
};
class RevokeThreadLocalMarkStackCheckpoint : public Closure {
public:
RevokeThreadLocalMarkStackCheckpoint(ConcurrentCopying* concurrent_copying,
bool disable_weak_ref_access)
: concurrent_copying_(concurrent_copying),
disable_weak_ref_access_(disable_weak_ref_access) {
}
virtual void Run(Thread* thread) OVERRIDE NO_THREAD_SAFETY_ANALYSIS {
// Note: self is not necessarily equal to thread since thread may be suspended.
Thread* self = Thread::Current();
CHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc)
<< thread->GetState() << " thread " << thread << " self " << self;
// Revoke thread local mark stacks.
accounting::AtomicStack<mirror::Object>* tl_mark_stack = thread->GetThreadLocalMarkStack();
if (tl_mark_stack != nullptr) {
MutexLock mu(self, concurrent_copying_->mark_stack_lock_);
concurrent_copying_->revoked_mark_stacks_.push_back(tl_mark_stack);
thread->SetThreadLocalMarkStack(nullptr);
}
// Disable weak ref access.
if (disable_weak_ref_access_) {
thread->SetWeakRefAccessEnabled(false);
}
// If thread is a running mutator, then act on behalf of the garbage collector.
// See the code in ThreadList::RunCheckpoint.
concurrent_copying_->GetBarrier().Pass(self);
}
private:
ConcurrentCopying* const concurrent_copying_;
const bool disable_weak_ref_access_;
};
void ConcurrentCopying::RevokeThreadLocalMarkStacks(bool disable_weak_ref_access) {
Thread* self = Thread::Current();
RevokeThreadLocalMarkStackCheckpoint check_point(this, disable_weak_ref_access);
ThreadList* thread_list = Runtime::Current()->GetThreadList();
gc_barrier_->Init(self, 0);
size_t barrier_count = thread_list->RunCheckpoint(&check_point);
// If there are no threads to wait which implys that all the checkpoint functions are finished,
// then no need to release the mutator lock.
if (barrier_count == 0) {
return;
}
Locks::mutator_lock_->SharedUnlock(self);
{
ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun);
gc_barrier_->Increment(self, barrier_count);
}
Locks::mutator_lock_->SharedLock(self);
}
void ConcurrentCopying::RevokeThreadLocalMarkStack(Thread* thread) {
Thread* self = Thread::Current();
CHECK_EQ(self, thread);
accounting::AtomicStack<mirror::Object>* tl_mark_stack = thread->GetThreadLocalMarkStack();
if (tl_mark_stack != nullptr) {
CHECK(is_marking_);
MutexLock mu(self, mark_stack_lock_);
revoked_mark_stacks_.push_back(tl_mark_stack);
thread->SetThreadLocalMarkStack(nullptr);
}
}
void ConcurrentCopying::ProcessMarkStack() {
if (kVerboseMode) {
LOG(INFO) << "ProcessMarkStack. ";
}
bool empty_prev = false;
while (true) {
bool empty = ProcessMarkStackOnce();
if (empty_prev && empty) {
// Saw empty mark stack for a second time, done.
break;
}
empty_prev = empty;
}
}
bool ConcurrentCopying::ProcessMarkStackOnce() {
Thread* self = Thread::Current();
CHECK(thread_running_gc_ != nullptr);
CHECK(self == thread_running_gc_);
CHECK(self->GetThreadLocalMarkStack() == nullptr);
size_t count = 0;
MarkStackMode mark_stack_mode = mark_stack_mode_.LoadRelaxed();
if (mark_stack_mode == kMarkStackModeThreadLocal) {
// Process the thread-local mark stacks and the GC mark stack.
count += ProcessThreadLocalMarkStacks(false);
while (!gc_mark_stack_->IsEmpty()) {
mirror::Object* to_ref = gc_mark_stack_->PopBack();
ProcessMarkStackRef(to_ref);
++count;
}
gc_mark_stack_->Reset();
} else if (mark_stack_mode == kMarkStackModeShared) {
// Process the shared GC mark stack with a lock.
{
MutexLock mu(self, mark_stack_lock_);
CHECK(revoked_mark_stacks_.empty());
}
while (true) {
std::vector<mirror::Object*> refs;
{
// Copy refs with lock. Note the number of refs should be small.
MutexLock mu(self, mark_stack_lock_);
if (gc_mark_stack_->IsEmpty()) {
break;
}
for (StackReference<mirror::Object>* p = gc_mark_stack_->Begin();
p != gc_mark_stack_->End(); ++p) {
refs.push_back(p->AsMirrorPtr());
}
gc_mark_stack_->Reset();
}
for (mirror::Object* ref : refs) {
ProcessMarkStackRef(ref);
++count;
}
}
} else {
CHECK_EQ(static_cast<uint32_t>(mark_stack_mode),
static_cast<uint32_t>(kMarkStackModeGcExclusive));
{
MutexLock mu(self, mark_stack_lock_);
CHECK(revoked_mark_stacks_.empty());
}
// Process the GC mark stack in the exclusive mode. No need to take the lock.
while (!gc_mark_stack_->IsEmpty()) {
mirror::Object* to_ref = gc_mark_stack_->PopBack();
ProcessMarkStackRef(to_ref);
++count;
}
gc_mark_stack_->Reset();
}
// Return true if the stack was empty.
return count == 0;
}
size_t ConcurrentCopying::ProcessThreadLocalMarkStacks(bool disable_weak_ref_access) {
// Run a checkpoint to collect all thread local mark stacks and iterate over them all.
RevokeThreadLocalMarkStacks(disable_weak_ref_access);
size_t count = 0;
std::vector<accounting::AtomicStack<mirror::Object>*> mark_stacks;
{
MutexLock mu(Thread::Current(), mark_stack_lock_);
// Make a copy of the mark stack vector.
mark_stacks = revoked_mark_stacks_;
revoked_mark_stacks_.clear();
}
for (accounting::AtomicStack<mirror::Object>* mark_stack : mark_stacks) {
for (StackReference<mirror::Object>* p = mark_stack->Begin(); p != mark_stack->End(); ++p) {
mirror::Object* to_ref = p->AsMirrorPtr();
ProcessMarkStackRef(to_ref);
++count;
}
{
MutexLock mu(Thread::Current(), mark_stack_lock_);
if (pooled_mark_stacks_.size() >= kMarkStackPoolSize) {
// The pool has enough. Delete it.
delete mark_stack;
} else {
// Otherwise, put it into the pool for later reuse.
mark_stack->Reset();
pooled_mark_stacks_.push_back(mark_stack);
}
}
}
return count;
}
inline void ConcurrentCopying::ProcessMarkStackRef(mirror::Object* to_ref) {
DCHECK(!region_space_->IsInFromSpace(to_ref));
if (kUseBakerReadBarrier) {
DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr())
<< " " << to_ref << " " << to_ref->GetReadBarrierPointer()
<< " is_marked=" << IsMarked(to_ref);
}
// Scan ref fields.
Scan(to_ref);
// Mark the gray ref as white or black.
if (kUseBakerReadBarrier) {
DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr())
<< " " << to_ref << " " << to_ref->GetReadBarrierPointer()
<< " is_marked=" << IsMarked(to_ref);
}
#ifdef USE_BAKER_OR_BROOKS_READ_BARRIER
if (UNLIKELY((to_ref->GetClass<kVerifyNone, kWithoutReadBarrier>()->IsTypeOfReferenceClass() &&
to_ref->AsReference()->GetReferent<kWithoutReadBarrier>() != nullptr &&
!IsInToSpace(to_ref->AsReference()->GetReferent<kWithoutReadBarrier>())))) {
// Leave this Reference gray in the queue so that GetReferent() will trigger a read barrier. We
// will change it to black or white later in ReferenceQueue::DequeuePendingReference().
DCHECK(to_ref->AsReference()->IsEnqueued()) << "Left unenqueued ref gray " << to_ref;
} else {
// We may occasionally leave a Reference black or white in the queue if its referent happens to
// be concurrently marked after the Scan() call above has enqueued the Reference, in which case
// the above IsInToSpace() evaluates to true and we change the color from gray to black or white
// here in this else block.
if (kUseBakerReadBarrier) {
if (region_space_->IsInToSpace(to_ref)) {
// If to-space, change from gray to white.
bool success = to_ref->AtomicSetReadBarrierPointer</*kCasRelease*/true>(
ReadBarrier::GrayPtr(),
ReadBarrier::WhitePtr());
DCHECK(success) << "Must succeed as we won the race.";
DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::WhitePtr());
} else {
// If non-moving space/unevac from space, change from gray
// to black. We can't change gray to white because it's not
// safe to use CAS if two threads change values in opposite
// directions (A->B and B->A). So, we change it to black to
// indicate non-moving objects that have been marked
// through. Note we'd need to change from black to white
// later (concurrently).
bool success = to_ref->AtomicSetReadBarrierPointer</*kCasRelease*/true>(
ReadBarrier::GrayPtr(),
ReadBarrier::BlackPtr());
DCHECK(success) << "Must succeed as we won the race.";
DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr());
}
}
}
#else
DCHECK(!kUseBakerReadBarrier);
#endif
if (ReadBarrier::kEnableToSpaceInvariantChecks || kIsDebugBuild) {
ConcurrentCopyingAssertToSpaceInvariantObjectVisitor visitor(this);
visitor(to_ref);
}
}
void ConcurrentCopying::SwitchToSharedMarkStackMode() {
Thread* self = Thread::Current();
CHECK(thread_running_gc_ != nullptr);
CHECK_EQ(self, thread_running_gc_);
CHECK(self->GetThreadLocalMarkStack() == nullptr);
MarkStackMode before_mark_stack_mode = mark_stack_mode_.LoadRelaxed();
CHECK_EQ(static_cast<uint32_t>(before_mark_stack_mode),
static_cast<uint32_t>(kMarkStackModeThreadLocal));
mark_stack_mode_.StoreRelaxed(kMarkStackModeShared);
CHECK(weak_ref_access_enabled_.LoadRelaxed());
weak_ref_access_enabled_.StoreRelaxed(false);
QuasiAtomic::ThreadFenceForConstructor();
// Process the thread local mark stacks one last time after switching to the shared mark stack
// mode and disable weak ref accesses.
ProcessThreadLocalMarkStacks(true);
if (kVerboseMode) {
LOG(INFO) << "Switched to shared mark stack mode and disabled weak ref access";
}
}
void ConcurrentCopying::SwitchToGcExclusiveMarkStackMode() {
Thread* self = Thread::Current();
CHECK(thread_running_gc_ != nullptr);
CHECK_EQ(self, thread_running_gc_);
CHECK(self->GetThreadLocalMarkStack() == nullptr);
MarkStackMode before_mark_stack_mode = mark_stack_mode_.LoadRelaxed();
CHECK_EQ(static_cast<uint32_t>(before_mark_stack_mode),
static_cast<uint32_t>(kMarkStackModeShared));
mark_stack_mode_.StoreRelaxed(kMarkStackModeGcExclusive);
QuasiAtomic::ThreadFenceForConstructor();
if (kVerboseMode) {
LOG(INFO) << "Switched to GC exclusive mark stack mode";
}
}
void ConcurrentCopying::CheckEmptyMarkStack() {
Thread* self = Thread::Current();
CHECK(thread_running_gc_ != nullptr);
CHECK_EQ(self, thread_running_gc_);
CHECK(self->GetThreadLocalMarkStack() == nullptr);
MarkStackMode mark_stack_mode = mark_stack_mode_.LoadRelaxed();
if (mark_stack_mode == kMarkStackModeThreadLocal) {
// Thread-local mark stack mode.
RevokeThreadLocalMarkStacks(false);
MutexLock mu(Thread::Current(), mark_stack_lock_);
if (!revoked_mark_stacks_.empty()) {
for (accounting::AtomicStack<mirror::Object>* mark_stack : revoked_mark_stacks_) {
while (!mark_stack->IsEmpty()) {
mirror::Object* obj = mark_stack->PopBack();
if (kUseBakerReadBarrier) {
mirror::Object* rb_ptr = obj->GetReadBarrierPointer();
LOG(INFO) << "On mark queue : " << obj << " " << PrettyTypeOf(obj) << " rb_ptr=" << rb_ptr
<< " is_marked=" << IsMarked(obj);
} else {
LOG(INFO) << "On mark queue : " << obj << " " << PrettyTypeOf(obj)
<< " is_marked=" << IsMarked(obj);
}
}
}
LOG(FATAL) << "mark stack is not empty";
}
} else {
// Shared, GC-exclusive, or off.
MutexLock mu(Thread::Current(), mark_stack_lock_);
CHECK(gc_mark_stack_->IsEmpty());
CHECK(revoked_mark_stacks_.empty());
}
}
void ConcurrentCopying::SweepSystemWeaks(Thread* self) {
TimingLogger::ScopedTiming split("SweepSystemWeaks", GetTimings());
ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
Runtime::Current()->SweepSystemWeaks(this);
}
void ConcurrentCopying::Sweep(bool swap_bitmaps) {
{
TimingLogger::ScopedTiming t("MarkStackAsLive", GetTimings());
accounting::ObjectStack* live_stack = heap_->GetLiveStack();
if (kEnableFromSpaceAccountingCheck) {
CHECK_GE(live_stack_freeze_size_, live_stack->Size());
}
heap_->MarkAllocStackAsLive(live_stack);
live_stack->Reset();
}
CheckEmptyMarkStack();
TimingLogger::ScopedTiming split("Sweep", GetTimings());
for (const auto& space : GetHeap()->GetContinuousSpaces()) {
if (space->IsContinuousMemMapAllocSpace()) {
space::ContinuousMemMapAllocSpace* alloc_space = space->AsContinuousMemMapAllocSpace();
if (space == region_space_ || immune_spaces_.ContainsSpace(space)) {
continue;
}
TimingLogger::ScopedTiming split2(
alloc_space->IsZygoteSpace() ? "SweepZygoteSpace" : "SweepAllocSpace", GetTimings());
RecordFree(alloc_space->Sweep(swap_bitmaps));
}
}
SweepLargeObjects(swap_bitmaps);
}
void ConcurrentCopying::SweepLargeObjects(bool swap_bitmaps) {
TimingLogger::ScopedTiming split("SweepLargeObjects", GetTimings());
RecordFreeLOS(heap_->GetLargeObjectsSpace()->Sweep(swap_bitmaps));
}
class ConcurrentCopyingClearBlackPtrsVisitor {
public:
explicit ConcurrentCopyingClearBlackPtrsVisitor(ConcurrentCopying* cc)
: collector_(cc) {}
void operator()(mirror::Object* obj) const SHARED_REQUIRES(Locks::mutator_lock_)
SHARED_REQUIRES(Locks::heap_bitmap_lock_) {
DCHECK(obj != nullptr);
DCHECK(collector_->heap_->GetMarkBitmap()->Test(obj)) << obj;
DCHECK_EQ(obj->GetReadBarrierPointer(), ReadBarrier::BlackPtr()) << obj;
obj->AtomicSetReadBarrierPointer(ReadBarrier::BlackPtr(), ReadBarrier::WhitePtr());
DCHECK_EQ(obj->GetReadBarrierPointer(), ReadBarrier::WhitePtr()) << obj;
}
private:
ConcurrentCopying* const collector_;
};
// Clear the black ptrs in non-moving objects back to white.
void ConcurrentCopying::ClearBlackPtrs() {
CHECK(kUseBakerReadBarrier);
TimingLogger::ScopedTiming split("ClearBlackPtrs", GetTimings());
ConcurrentCopyingClearBlackPtrsVisitor visitor(this);
for (auto& space : heap_->GetContinuousSpaces()) {
if (space == region_space_) {
continue;
}
accounting::ContinuousSpaceBitmap* mark_bitmap = space->GetMarkBitmap();
if (kVerboseMode) {
LOG(INFO) << "ClearBlackPtrs: " << *space << " bitmap: " << *mark_bitmap;
}
mark_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(space->Begin()),
reinterpret_cast<uintptr_t>(space->Limit()),
visitor);
}
space::LargeObjectSpace* large_object_space = heap_->GetLargeObjectsSpace();
large_object_space->GetMarkBitmap()->VisitMarkedRange(
reinterpret_cast<uintptr_t>(large_object_space->Begin()),
reinterpret_cast<uintptr_t>(large_object_space->End()),
visitor);
// Objects on the allocation stack?
if (ReadBarrier::kEnableReadBarrierInvariantChecks || kIsDebugBuild) {
size_t count = GetAllocationStack()->Size();
auto* it = GetAllocationStack()->Begin();
auto* end = GetAllocationStack()->End();
for (size_t i = 0; i < count; ++i, ++it) {
CHECK_LT(it, end);
mirror::Object* obj = it->AsMirrorPtr();
if (obj != nullptr) {
// Must have been cleared above.
CHECK_EQ(obj->GetReadBarrierPointer(), ReadBarrier::WhitePtr()) << obj;
}
}
}
}
void ConcurrentCopying::ReclaimPhase() {
TimingLogger::ScopedTiming split("ReclaimPhase", GetTimings());
if (kVerboseMode) {
LOG(INFO) << "GC ReclaimPhase";
}
Thread* self = Thread::Current();
{
// Double-check that the mark stack is empty.
// Note: need to set this after VerifyNoFromSpaceRef().
is_asserting_to_space_invariant_ = false;
QuasiAtomic::ThreadFenceForConstructor();
if (kVerboseMode) {
LOG(INFO) << "Issue an empty check point. ";
}
IssueEmptyCheckpoint();
// Disable the check.
is_mark_stack_push_disallowed_.StoreSequentiallyConsistent(0);
CheckEmptyMarkStack();
}
{
// Record freed objects.
TimingLogger::ScopedTiming split2("RecordFree", GetTimings());
// Don't include thread-locals that are in the to-space.
uint64_t from_bytes = region_space_->GetBytesAllocatedInFromSpace();
uint64_t from_objects = region_space_->GetObjectsAllocatedInFromSpace();
uint64_t unevac_from_bytes = region_space_->GetBytesAllocatedInUnevacFromSpace();
uint64_t unevac_from_objects = region_space_->GetObjectsAllocatedInUnevacFromSpace();
uint64_t to_bytes = bytes_moved_.LoadSequentiallyConsistent();
uint64_t to_objects = objects_moved_.LoadSequentiallyConsistent();
if (kEnableFromSpaceAccountingCheck) {
CHECK_EQ(from_space_num_objects_at_first_pause_, from_objects + unevac_from_objects);
CHECK_EQ(from_space_num_bytes_at_first_pause_, from_bytes + unevac_from_bytes);
}
CHECK_LE(to_objects, from_objects);
CHECK_LE(to_bytes, from_bytes);
int64_t freed_bytes = from_bytes - to_bytes;
int64_t freed_objects = from_objects - to_objects;
if (kVerboseMode) {
LOG(INFO) << "RecordFree:"
<< " from_bytes=" << from_bytes << " from_objects=" << from_objects
<< " unevac_from_bytes=" << unevac_from_bytes << " unevac_from_objects=" << unevac_from_objects
<< " to_bytes=" << to_bytes << " to_objects=" << to_objects
<< " freed_bytes=" << freed_bytes << " freed_objects=" << freed_objects
<< " from_space size=" << region_space_->FromSpaceSize()
<< " unevac_from_space size=" << region_space_->UnevacFromSpaceSize()
<< " to_space size=" << region_space_->ToSpaceSize();
LOG(INFO) << "(before) num_bytes_allocated=" << heap_->num_bytes_allocated_.LoadSequentiallyConsistent();
}
RecordFree(ObjectBytePair(freed_objects, freed_bytes));
if (kVerboseMode) {
LOG(INFO) << "(after) num_bytes_allocated=" << heap_->num_bytes_allocated_.LoadSequentiallyConsistent();
}
}
{
TimingLogger::ScopedTiming split3("ComputeUnevacFromSpaceLiveRatio", GetTimings());
ComputeUnevacFromSpaceLiveRatio();
}
{
TimingLogger::ScopedTiming split4("ClearFromSpace", GetTimings());
region_space_->ClearFromSpace();
}
{
WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
if (kUseBakerReadBarrier) {
ClearBlackPtrs();
}
Sweep(false);
SwapBitmaps();
heap_->UnBindBitmaps();
// Remove bitmaps for the immune spaces.
while (!cc_bitmaps_.empty()) {
accounting::ContinuousSpaceBitmap* cc_bitmap = cc_bitmaps_.back();
cc_heap_bitmap_->RemoveContinuousSpaceBitmap(cc_bitmap);
delete cc_bitmap;
cc_bitmaps_.pop_back();
}
region_space_bitmap_ = nullptr;
}
CheckEmptyMarkStack();
if (kVerboseMode) {
LOG(INFO) << "GC end of ReclaimPhase";
}
}
class ConcurrentCopyingComputeUnevacFromSpaceLiveRatioVisitor {
public:
explicit ConcurrentCopyingComputeUnevacFromSpaceLiveRatioVisitor(ConcurrentCopying* cc)
: collector_(cc) {}
void operator()(mirror::Object* ref) const SHARED_REQUIRES(Locks::mutator_lock_)
SHARED_REQUIRES(Locks::heap_bitmap_lock_) {
DCHECK(ref != nullptr);
DCHECK(collector_->region_space_bitmap_->Test(ref)) << ref;
DCHECK(collector_->region_space_->IsInUnevacFromSpace(ref)) << ref;
if (kUseBakerReadBarrier) {
DCHECK_EQ(ref->GetReadBarrierPointer(), ReadBarrier::BlackPtr()) << ref;
// Clear the black ptr.
ref->AtomicSetReadBarrierPointer(ReadBarrier::BlackPtr(), ReadBarrier::WhitePtr());
DCHECK_EQ(ref->GetReadBarrierPointer(), ReadBarrier::WhitePtr()) << ref;
}
size_t obj_size = ref->SizeOf();
size_t alloc_size = RoundUp(obj_size, space::RegionSpace::kAlignment);
collector_->region_space_->AddLiveBytes(ref, alloc_size);
}
private:
ConcurrentCopying* const collector_;
};
// Compute how much live objects are left in regions.
void ConcurrentCopying::ComputeUnevacFromSpaceLiveRatio() {
region_space_->AssertAllRegionLiveBytesZeroOrCleared();
ConcurrentCopyingComputeUnevacFromSpaceLiveRatioVisitor visitor(this);
region_space_bitmap_->VisitMarkedRange(reinterpret_cast<uintptr_t>(region_space_->Begin()),
reinterpret_cast<uintptr_t>(region_space_->Limit()),
visitor);
}
// Assert the to-space invariant.
void ConcurrentCopying::AssertToSpaceInvariant(mirror::Object* obj, MemberOffset offset,
mirror::Object* ref) {
CHECK(heap_->collector_type_ == kCollectorTypeCC) << static_cast<size_t>(heap_->collector_type_);
if (is_asserting_to_space_invariant_) {
if (region_space_->IsInToSpace(ref)) {
// OK.
return;
} else if (region_space_->IsInUnevacFromSpace(ref)) {
CHECK(region_space_bitmap_->Test(ref)) << ref;
} else if (region_space_->IsInFromSpace(ref)) {
// Not OK. Do extra logging.
if (obj != nullptr) {
LogFromSpaceRefHolder(obj, offset);
}
ref->GetLockWord(false).Dump(LOG(INTERNAL_FATAL));
CHECK(false) << "Found from-space ref " << ref << " " << PrettyTypeOf(ref);
} else {
AssertToSpaceInvariantInNonMovingSpace(obj, ref);
}
}
}
class RootPrinter {
public:
RootPrinter() { }
template <class MirrorType>
ALWAYS_INLINE void VisitRootIfNonNull(mirror::CompressedReference<MirrorType>* root)
SHARED_REQUIRES(Locks::mutator_lock_) {
if (!root->IsNull()) {
VisitRoot(root);
}
}
template <class MirrorType>
void VisitRoot(mirror::Object** root)
SHARED_REQUIRES(Locks::mutator_lock_) {
LOG(INTERNAL_FATAL) << "root=" << root << " ref=" << *root;
}
template <class MirrorType>
void VisitRoot(mirror::CompressedReference<MirrorType>* root)
SHARED_REQUIRES(Locks::mutator_lock_) {
LOG(INTERNAL_FATAL) << "root=" << root << " ref=" << root->AsMirrorPtr();
}
};
void ConcurrentCopying::AssertToSpaceInvariant(GcRootSource* gc_root_source,
mirror::Object* ref) {
CHECK(heap_->collector_type_ == kCollectorTypeCC) << static_cast<size_t>(heap_->collector_type_);
if (is_asserting_to_space_invariant_) {
if (region_space_->IsInToSpace(ref)) {
// OK.
return;
} else if (region_space_->IsInUnevacFromSpace(ref)) {
CHECK(region_space_bitmap_->Test(ref)) << ref;
} else if (region_space_->IsInFromSpace(ref)) {
// Not OK. Do extra logging.
if (gc_root_source == nullptr) {
// No info.
} else if (gc_root_source->HasArtField()) {
ArtField* field = gc_root_source->GetArtField();
LOG(INTERNAL_FATAL) << "gc root in field " << field << " " << PrettyField(field);
RootPrinter root_printer;
field->VisitRoots(root_printer);
} else if (gc_root_source->HasArtMethod()) {
ArtMethod* method = gc_root_source->GetArtMethod();
LOG(INTERNAL_FATAL) << "gc root in method " << method << " " << PrettyMethod(method);
RootPrinter root_printer;
method->VisitRoots(root_printer, sizeof(void*));
}
ref->GetLockWord(false).Dump(LOG(INTERNAL_FATAL));
region_space_->DumpNonFreeRegions(LOG(INTERNAL_FATAL));
PrintFileToLog("/proc/self/maps", LogSeverity::INTERNAL_FATAL);
MemMap::DumpMaps(LOG(INTERNAL_FATAL), true);
CHECK(false) << "Found from-space ref " << ref << " " << PrettyTypeOf(ref);
} else {
AssertToSpaceInvariantInNonMovingSpace(nullptr, ref);
}
}
}
void ConcurrentCopying::LogFromSpaceRefHolder(mirror::Object* obj, MemberOffset offset) {
if (kUseBakerReadBarrier) {
LOG(INFO) << "holder=" << obj << " " << PrettyTypeOf(obj)
<< " holder rb_ptr=" << obj->GetReadBarrierPointer();
} else {
LOG(INFO) << "holder=" << obj << " " << PrettyTypeOf(obj);
}
if (region_space_->IsInFromSpace(obj)) {
LOG(INFO) << "holder is in the from-space.";
} else if (region_space_->IsInToSpace(obj)) {
LOG(INFO) << "holder is in the to-space.";
} else if (region_space_->IsInUnevacFromSpace(obj)) {
LOG(INFO) << "holder is in the unevac from-space.";
if (region_space_bitmap_->Test(obj)) {
LOG(INFO) << "holder is marked in the region space bitmap.";
} else {
LOG(INFO) << "holder is not marked in the region space bitmap.";
}
} else {
// In a non-moving space.
if (immune_spaces_.ContainsObject(obj)) {
LOG(INFO) << "holder is in an immune image or the zygote space.";
accounting::ContinuousSpaceBitmap* cc_bitmap =
cc_heap_bitmap_->GetContinuousSpaceBitmap(obj);
CHECK(cc_bitmap != nullptr)
<< "An immune space object must have a bitmap.";
if (cc_bitmap->Test(obj)) {
LOG(INFO) << "holder is marked in the bit map.";
} else {
LOG(INFO) << "holder is NOT marked in the bit map.";
}
} else {
LOG(INFO) << "holder is in a non-immune, non-moving (or main) space.";
accounting::ContinuousSpaceBitmap* mark_bitmap =
heap_mark_bitmap_->GetContinuousSpaceBitmap(obj);
accounting::LargeObjectBitmap* los_bitmap =
heap_mark_bitmap_->GetLargeObjectBitmap(obj);
CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
bool is_los = mark_bitmap == nullptr;
if (!is_los && mark_bitmap->Test(obj)) {
LOG(INFO) << "holder is marked in the mark bit map.";
} else if (is_los && los_bitmap->Test(obj)) {
LOG(INFO) << "holder is marked in the los bit map.";
} else {
// If ref is on the allocation stack, then it is considered
// mark/alive (but not necessarily on the live stack.)
if (IsOnAllocStack(obj)) {
LOG(INFO) << "holder is on the alloc stack.";
} else {
LOG(INFO) << "holder is not marked or on the alloc stack.";
}
}
}
}
LOG(INFO) << "offset=" << offset.SizeValue();
}
void ConcurrentCopying::AssertToSpaceInvariantInNonMovingSpace(mirror::Object* obj,
mirror::Object* ref) {
// In a non-moving spaces. Check that the ref is marked.
if (immune_spaces_.ContainsObject(ref)) {
accounting::ContinuousSpaceBitmap* cc_bitmap =
cc_heap_bitmap_->GetContinuousSpaceBitmap(ref);
CHECK(cc_bitmap != nullptr)
<< "An immune space ref must have a bitmap. " << ref;
if (kUseBakerReadBarrier) {
CHECK(cc_bitmap->Test(ref))
<< "Unmarked immune space ref. obj=" << obj << " rb_ptr="
<< obj->GetReadBarrierPointer() << " ref=" << ref;
} else {
CHECK(cc_bitmap->Test(ref))
<< "Unmarked immune space ref. obj=" << obj << " ref=" << ref;
}
} else {
accounting::ContinuousSpaceBitmap* mark_bitmap =
heap_mark_bitmap_->GetContinuousSpaceBitmap(ref);
accounting::LargeObjectBitmap* los_bitmap =
heap_mark_bitmap_->GetLargeObjectBitmap(ref);
CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
bool is_los = mark_bitmap == nullptr;
if ((!is_los && mark_bitmap->Test(ref)) ||
(is_los && los_bitmap->Test(ref))) {
// OK.
} else {
// If ref is on the allocation stack, then it may not be
// marked live, but considered marked/alive (but not
// necessarily on the live stack).
CHECK(IsOnAllocStack(ref)) << "Unmarked ref that's not on the allocation stack. "
<< "obj=" << obj << " ref=" << ref;
}
}
}
// Used to scan ref fields of an object.
class ConcurrentCopyingRefFieldsVisitor {
public:
explicit ConcurrentCopyingRefFieldsVisitor(ConcurrentCopying* collector)
: collector_(collector) {}
void operator()(mirror::Object* obj, MemberOffset offset, bool /* is_static */)
const ALWAYS_INLINE SHARED_REQUIRES(Locks::mutator_lock_)
SHARED_REQUIRES(Locks::heap_bitmap_lock_) {
collector_->Process(obj, offset);
}
void operator()(mirror::Class* klass, mirror::Reference* ref) const
SHARED_REQUIRES(Locks::mutator_lock_) ALWAYS_INLINE {
CHECK(klass->IsTypeOfReferenceClass());
collector_->DelayReferenceReferent(klass, ref);
}
void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const
ALWAYS_INLINE
SHARED_REQUIRES(Locks::mutator_lock_) {
if (!root->IsNull()) {
VisitRoot(root);
}
}
void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const
ALWAYS_INLINE
SHARED_REQUIRES(Locks::mutator_lock_) {
collector_->MarkRoot(root);
}
private:
ConcurrentCopying* const collector_;
};
// Scan ref fields of an object.
inline void ConcurrentCopying::Scan(mirror::Object* to_ref) {
DCHECK(!region_space_->IsInFromSpace(to_ref));
ConcurrentCopyingRefFieldsVisitor visitor(this);
to_ref->VisitReferences(visitor, visitor);
}
// Process a field.
inline void ConcurrentCopying::Process(mirror::Object* obj, MemberOffset offset) {
mirror::Object* ref = obj->GetFieldObject<
mirror::Object, kVerifyNone, kWithoutReadBarrier, false>(offset);
mirror::Object* to_ref = Mark(ref);
if (to_ref == ref) {
return;
}
// This may fail if the mutator writes to the field at the same time. But it's ok.
mirror::Object* expected_ref = ref;
mirror::Object* new_ref = to_ref;
do {
if (expected_ref !=
obj->GetFieldObject<mirror::Object, kVerifyNone, kWithoutReadBarrier, false>(offset)) {
// It was updated by the mutator.
break;
}
} while (!obj->CasFieldWeakRelaxedObjectWithoutWriteBarrier<
false, false, kVerifyNone>(offset, expected_ref, new_ref));
}
// Process some roots.
inline void ConcurrentCopying::VisitRoots(
mirror::Object*** roots, size_t count, const RootInfo& info ATTRIBUTE_UNUSED) {
for (size_t i = 0; i < count; ++i) {
mirror::Object** root = roots[i];
mirror::Object* ref = *root;
mirror::Object* to_ref = Mark(ref);
if (to_ref == ref) {
continue;
}
Atomic<mirror::Object*>* addr = reinterpret_cast<Atomic<mirror::Object*>*>(root);
mirror::Object* expected_ref = ref;
mirror::Object* new_ref = to_ref;
do {
if (expected_ref != addr->LoadRelaxed()) {
// It was updated by the mutator.
break;
}
} while (!addr->CompareExchangeWeakRelaxed(expected_ref, new_ref));
}
}
inline void ConcurrentCopying::MarkRoot(mirror::CompressedReference<mirror::Object>* root) {
DCHECK(!root->IsNull());
mirror::Object* const ref = root->AsMirrorPtr();
mirror::Object* to_ref = Mark(ref);
if (to_ref != ref) {
auto* addr = reinterpret_cast<Atomic<mirror::CompressedReference<mirror::Object>>*>(root);
auto expected_ref = mirror::CompressedReference<mirror::Object>::FromMirrorPtr(ref);
auto new_ref = mirror::CompressedReference<mirror::Object>::FromMirrorPtr(to_ref);
// If the cas fails, then it was updated by the mutator.
do {
if (ref != addr->LoadRelaxed().AsMirrorPtr()) {
// It was updated by the mutator.
break;
}
} while (!addr->CompareExchangeWeakRelaxed(expected_ref, new_ref));
}
}
inline void ConcurrentCopying::VisitRoots(
mirror::CompressedReference<mirror::Object>** roots, size_t count,
const RootInfo& info ATTRIBUTE_UNUSED) {
for (size_t i = 0; i < count; ++i) {
mirror::CompressedReference<mirror::Object>* const root = roots[i];
if (!root->IsNull()) {
MarkRoot(root);
}
}
}
// Fill the given memory block with a dummy object. Used to fill in a
// copy of objects that was lost in race.
void ConcurrentCopying::FillWithDummyObject(mirror::Object* dummy_obj, size_t byte_size) {
CHECK_ALIGNED(byte_size, kObjectAlignment);
memset(dummy_obj, 0, byte_size);
mirror::Class* int_array_class = mirror::IntArray::GetArrayClass();
CHECK(int_array_class != nullptr);
AssertToSpaceInvariant(nullptr, MemberOffset(0), int_array_class);
size_t component_size = int_array_class->GetComponentSize();
CHECK_EQ(component_size, sizeof(int32_t));
size_t data_offset = mirror::Array::DataOffset(component_size).SizeValue();
if (data_offset > byte_size) {
// An int array is too big. Use java.lang.Object.
mirror::Class* java_lang_Object = WellKnownClasses::ToClass(WellKnownClasses::java_lang_Object);
AssertToSpaceInvariant(nullptr, MemberOffset(0), java_lang_Object);
CHECK_EQ(byte_size, java_lang_Object->GetObjectSize());
dummy_obj->SetClass(java_lang_Object);
CHECK_EQ(byte_size, dummy_obj->SizeOf());
} else {
// Use an int array.
dummy_obj->SetClass(int_array_class);
CHECK(dummy_obj->IsArrayInstance());
int32_t length = (byte_size - data_offset) / component_size;
dummy_obj->AsArray()->SetLength(length);
CHECK_EQ(dummy_obj->AsArray()->GetLength(), length)
<< "byte_size=" << byte_size << " length=" << length
<< " component_size=" << component_size << " data_offset=" << data_offset;
CHECK_EQ(byte_size, dummy_obj->SizeOf())
<< "byte_size=" << byte_size << " length=" << length
<< " component_size=" << component_size << " data_offset=" << data_offset;
}
}
// Reuse the memory blocks that were copy of objects that were lost in race.
mirror::Object* ConcurrentCopying::AllocateInSkippedBlock(size_t alloc_size) {
// Try to reuse the blocks that were unused due to CAS failures.
CHECK_ALIGNED(alloc_size, space::RegionSpace::kAlignment);
Thread* self = Thread::Current();
size_t min_object_size = RoundUp(sizeof(mirror::Object), space::RegionSpace::kAlignment);
MutexLock mu(self, skipped_blocks_lock_);
auto it = skipped_blocks_map_.lower_bound(alloc_size);
if (it == skipped_blocks_map_.end()) {
// Not found.
return nullptr;
}
{
size_t byte_size = it->first;
CHECK_GE(byte_size, alloc_size);
if (byte_size > alloc_size && byte_size - alloc_size < min_object_size) {
// If remainder would be too small for a dummy object, retry with a larger request size.
it = skipped_blocks_map_.lower_bound(alloc_size + min_object_size);
if (it == skipped_blocks_map_.end()) {
// Not found.
return nullptr;
}
CHECK_ALIGNED(it->first - alloc_size, space::RegionSpace::kAlignment);
CHECK_GE(it->first - alloc_size, min_object_size)
<< "byte_size=" << byte_size << " it->first=" << it->first << " alloc_size=" << alloc_size;
}
}
// Found a block.
CHECK(it != skipped_blocks_map_.end());
size_t byte_size = it->first;
uint8_t* addr = it->second;
CHECK_GE(byte_size, alloc_size);
CHECK(region_space_->IsInToSpace(reinterpret_cast<mirror::Object*>(addr)));
CHECK_ALIGNED(byte_size, space::RegionSpace::kAlignment);
if (kVerboseMode) {
LOG(INFO) << "Reusing skipped bytes : " << reinterpret_cast<void*>(addr) << ", " << byte_size;
}
skipped_blocks_map_.erase(it);
memset(addr, 0, byte_size);
if (byte_size > alloc_size) {
// Return the remainder to the map.
CHECK_ALIGNED(byte_size - alloc_size, space::RegionSpace::kAlignment);
CHECK_GE(byte_size - alloc_size, min_object_size);
FillWithDummyObject(reinterpret_cast<mirror::Object*>(addr + alloc_size),
byte_size - alloc_size);
CHECK(region_space_->IsInToSpace(reinterpret_cast<mirror::Object*>(addr + alloc_size)));
skipped_blocks_map_.insert(std::make_pair(byte_size - alloc_size, addr + alloc_size));
}
return reinterpret_cast<mirror::Object*>(addr);
}
mirror::Object* ConcurrentCopying::Copy(mirror::Object* from_ref) {
DCHECK(region_space_->IsInFromSpace(from_ref));
// No read barrier to avoid nested RB that might violate the to-space
// invariant. Note that from_ref is a from space ref so the SizeOf()
// call will access the from-space meta objects, but it's ok and necessary.
size_t obj_size = from_ref->SizeOf<kDefaultVerifyFlags, kWithoutReadBarrier>();
size_t region_space_alloc_size = RoundUp(obj_size, space::RegionSpace::kAlignment);
size_t region_space_bytes_allocated = 0U;
size_t non_moving_space_bytes_allocated = 0U;
size_t bytes_allocated = 0U;
size_t dummy;
mirror::Object* to_ref = region_space_->AllocNonvirtual<true>(
region_space_alloc_size, &region_space_bytes_allocated, nullptr, &dummy);
bytes_allocated = region_space_bytes_allocated;
if (to_ref != nullptr) {
DCHECK_EQ(region_space_alloc_size, region_space_bytes_allocated);
}
bool fall_back_to_non_moving = false;
if (UNLIKELY(to_ref == nullptr)) {
// Failed to allocate in the region space. Try the skipped blocks.
to_ref = AllocateInSkippedBlock(region_space_alloc_size);
if (to_ref != nullptr) {
// Succeeded to allocate in a skipped block.
if (heap_->use_tlab_) {
// This is necessary for the tlab case as it's not accounted in the space.
region_space_->RecordAlloc(to_ref);
}
bytes_allocated = region_space_alloc_size;
} else {
// Fall back to the non-moving space.
fall_back_to_non_moving = true;
if (kVerboseMode) {
LOG(INFO) << "Out of memory in the to-space. Fall back to non-moving. skipped_bytes="
<< to_space_bytes_skipped_.LoadSequentiallyConsistent()
<< " skipped_objects=" << to_space_objects_skipped_.LoadSequentiallyConsistent();
}
fall_back_to_non_moving = true;
to_ref = heap_->non_moving_space_->Alloc(Thread::Current(), obj_size,
&non_moving_space_bytes_allocated, nullptr, &dummy);
CHECK(to_ref != nullptr) << "Fall-back non-moving space allocation failed";
bytes_allocated = non_moving_space_bytes_allocated;
// Mark it in the mark bitmap.
accounting::ContinuousSpaceBitmap* mark_bitmap =
heap_mark_bitmap_->GetContinuousSpaceBitmap(to_ref);
CHECK(mark_bitmap != nullptr);
CHECK(!mark_bitmap->AtomicTestAndSet(to_ref));
}
}
DCHECK(to_ref != nullptr);
// Attempt to install the forward pointer. This is in a loop as the
// lock word atomic write can fail.
while (true) {
// Copy the object. TODO: copy only the lockword in the second iteration and on?
memcpy(to_ref, from_ref, obj_size);
LockWord old_lock_word = to_ref->GetLockWord(false);
if (old_lock_word.GetState() == LockWord::kForwardingAddress) {
// Lost the race. Another thread (either GC or mutator) stored
// the forwarding pointer first. Make the lost copy (to_ref)
// look like a valid but dead (dummy) object and keep it for
// future reuse.
FillWithDummyObject(to_ref, bytes_allocated);
if (!fall_back_to_non_moving) {
DCHECK(region_space_->IsInToSpace(to_ref));
if (bytes_allocated > space::RegionSpace::kRegionSize) {
// Free the large alloc.
region_space_->FreeLarge(to_ref, bytes_allocated);
} else {
// Record the lost copy for later reuse.
heap_->num_bytes_allocated_.FetchAndAddSequentiallyConsistent(bytes_allocated);
to_space_bytes_skipped_.FetchAndAddSequentiallyConsistent(bytes_allocated);
to_space_objects_skipped_.FetchAndAddSequentiallyConsistent(1);
MutexLock mu(Thread::Current(), skipped_blocks_lock_);
skipped_blocks_map_.insert(std::make_pair(bytes_allocated,
reinterpret_cast<uint8_t*>(to_ref)));
}
} else {
DCHECK(heap_->non_moving_space_->HasAddress(to_ref));
DCHECK_EQ(bytes_allocated, non_moving_space_bytes_allocated);
// Free the non-moving-space chunk.
accounting::ContinuousSpaceBitmap* mark_bitmap =
heap_mark_bitmap_->GetContinuousSpaceBitmap(to_ref);
CHECK(mark_bitmap != nullptr);
CHECK(mark_bitmap->Clear(to_ref));
heap_->non_moving_space_->Free(Thread::Current(), to_ref);
}
// Get the winner's forward ptr.
mirror::Object* lost_fwd_ptr = to_ref;
to_ref = reinterpret_cast<mirror::Object*>(old_lock_word.ForwardingAddress());
CHECK(to_ref != nullptr);
CHECK_NE(to_ref, lost_fwd_ptr);
CHECK(region_space_->IsInToSpace(to_ref) || heap_->non_moving_space_->HasAddress(to_ref));
CHECK_NE(to_ref->GetLockWord(false).GetState(), LockWord::kForwardingAddress);
return to_ref;
}
// Set the gray ptr.
if (kUseBakerReadBarrier) {
to_ref->SetReadBarrierPointer(ReadBarrier::GrayPtr());
}
LockWord new_lock_word = LockWord::FromForwardingAddress(reinterpret_cast<size_t>(to_ref));
// Try to atomically write the fwd ptr.
bool success = from_ref->CasLockWordWeakSequentiallyConsistent(old_lock_word, new_lock_word);
if (LIKELY(success)) {
// The CAS succeeded.
objects_moved_.FetchAndAddSequentiallyConsistent(1);
bytes_moved_.FetchAndAddSequentiallyConsistent(region_space_alloc_size);
if (LIKELY(!fall_back_to_non_moving)) {
DCHECK(region_space_->IsInToSpace(to_ref));
} else {
DCHECK(heap_->non_moving_space_->HasAddress(to_ref));
DCHECK_EQ(bytes_allocated, non_moving_space_bytes_allocated);
}
if (kUseBakerReadBarrier) {
DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
}
DCHECK(GetFwdPtr(from_ref) == to_ref);
CHECK_NE(to_ref->GetLockWord(false).GetState(), LockWord::kForwardingAddress);
PushOntoMarkStack(to_ref);
return to_ref;
} else {
// The CAS failed. It may have lost the race or may have failed
// due to monitor/hashcode ops. Either way, retry.
}
}
}
mirror::Object* ConcurrentCopying::IsMarked(mirror::Object* from_ref) {
DCHECK(from_ref != nullptr);
space::RegionSpace::RegionType rtype = region_space_->GetRegionType(from_ref);
if (rtype == space::RegionSpace::RegionType::kRegionTypeToSpace) {
// It's already marked.
return from_ref;
}
mirror::Object* to_ref;
if (rtype == space::RegionSpace::RegionType::kRegionTypeFromSpace) {
to_ref = GetFwdPtr(from_ref);
DCHECK(to_ref == nullptr || region_space_->IsInToSpace(to_ref) ||
heap_->non_moving_space_->HasAddress(to_ref))
<< "from_ref=" << from_ref << " to_ref=" << to_ref;
} else if (rtype == space::RegionSpace::RegionType::kRegionTypeUnevacFromSpace) {
if (region_space_bitmap_->Test(from_ref)) {
to_ref = from_ref;
} else {
to_ref = nullptr;
}
} else {
// from_ref is in a non-moving space.
if (immune_spaces_.ContainsObject(from_ref)) {
accounting::ContinuousSpaceBitmap* cc_bitmap =
cc_heap_bitmap_->GetContinuousSpaceBitmap(from_ref);
DCHECK(cc_bitmap != nullptr)
<< "An immune space object must have a bitmap";
if (kIsDebugBuild) {
DCHECK(heap_mark_bitmap_->GetContinuousSpaceBitmap(from_ref)->Test(from_ref))
<< "Immune space object must be already marked";
}
if (cc_bitmap->Test(from_ref)) {
// Already marked.
to_ref = from_ref;
} else {
// Newly marked.
to_ref = nullptr;
}
} else {
// Non-immune non-moving space. Use the mark bitmap.
accounting::ContinuousSpaceBitmap* mark_bitmap =
heap_mark_bitmap_->GetContinuousSpaceBitmap(from_ref);
accounting::LargeObjectBitmap* los_bitmap =
heap_mark_bitmap_->GetLargeObjectBitmap(from_ref);
CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
bool is_los = mark_bitmap == nullptr;
if (!is_los && mark_bitmap->Test(from_ref)) {
// Already marked.
to_ref = from_ref;
} else if (is_los && los_bitmap->Test(from_ref)) {
// Already marked in LOS.
to_ref = from_ref;
} else {
// Not marked.
if (IsOnAllocStack(from_ref)) {
// If on the allocation stack, it's considered marked.
to_ref = from_ref;
} else {
// Not marked.
to_ref = nullptr;
}
}
}
}
return to_ref;
}
bool ConcurrentCopying::IsOnAllocStack(mirror::Object* ref) {
QuasiAtomic::ThreadFenceAcquire();
accounting::ObjectStack* alloc_stack = GetAllocationStack();
return alloc_stack->Contains(ref);
}
mirror::Object* ConcurrentCopying::MarkNonMoving(mirror::Object* ref) {
// ref is in a non-moving space (from_ref == to_ref).
DCHECK(!region_space_->HasAddress(ref)) << ref;
if (immune_spaces_.ContainsObject(ref)) {
accounting::ContinuousSpaceBitmap* cc_bitmap =
cc_heap_bitmap_->GetContinuousSpaceBitmap(ref);
DCHECK(cc_bitmap != nullptr)
<< "An immune space object must have a bitmap";
if (kIsDebugBuild) {
DCHECK(heap_mark_bitmap_->GetContinuousSpaceBitmap(ref)->Test(ref))
<< "Immune space object must be already marked";
}
// This may or may not succeed, which is ok.
if (kUseBakerReadBarrier) {
ref->AtomicSetReadBarrierPointer(ReadBarrier::WhitePtr(), ReadBarrier::GrayPtr());
}
if (cc_bitmap->AtomicTestAndSet(ref)) {
// Already marked.
} else {
// Newly marked.
if (kUseBakerReadBarrier) {
DCHECK_EQ(ref->GetReadBarrierPointer(), ReadBarrier::GrayPtr());
}
PushOntoMarkStack(ref);
}
} else {
// Use the mark bitmap.
accounting::ContinuousSpaceBitmap* mark_bitmap =
heap_mark_bitmap_->GetContinuousSpaceBitmap(ref);
accounting::LargeObjectBitmap* los_bitmap =
heap_mark_bitmap_->GetLargeObjectBitmap(ref);
CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
bool is_los = mark_bitmap == nullptr;
if (!is_los && mark_bitmap->Test(ref)) {
// Already marked.
if (kUseBakerReadBarrier) {
DCHECK(ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr() ||
ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr());
}
} else if (is_los && los_bitmap->Test(ref)) {
// Already marked in LOS.
if (kUseBakerReadBarrier) {
DCHECK(ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr() ||
ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr());
}
} else {
// Not marked.
if (IsOnAllocStack(ref)) {
// If it's on the allocation stack, it's considered marked. Keep it white.
// Objects on the allocation stack need not be marked.
if (!is_los) {
DCHECK(!mark_bitmap->Test(ref));
} else {
DCHECK(!los_bitmap->Test(ref));
}
if (kUseBakerReadBarrier) {
DCHECK_EQ(ref->GetReadBarrierPointer(), ReadBarrier::WhitePtr());
}
} else {
// Not marked or on the allocation stack. Try to mark it.
// This may or may not succeed, which is ok.
if (kUseBakerReadBarrier) {
ref->AtomicSetReadBarrierPointer(ReadBarrier::WhitePtr(), ReadBarrier::GrayPtr());
}
if (!is_los && mark_bitmap->AtomicTestAndSet(ref)) {
// Already marked.
} else if (is_los && los_bitmap->AtomicTestAndSet(ref)) {
// Already marked in LOS.
} else {
// Newly marked.
if (kUseBakerReadBarrier) {
DCHECK_EQ(ref->GetReadBarrierPointer(), ReadBarrier::GrayPtr());
}
PushOntoMarkStack(ref);
}
}
}
}
return ref;
}
void ConcurrentCopying::FinishPhase() {
Thread* const self = Thread::Current();
{
MutexLock mu(self, mark_stack_lock_);
CHECK_EQ(pooled_mark_stacks_.size(), kMarkStackPoolSize);
}
region_space_ = nullptr;
{
MutexLock mu(Thread::Current(), skipped_blocks_lock_);
skipped_blocks_map_.clear();
}
ReaderMutexLock mu(self, *Locks::mutator_lock_);
WriterMutexLock mu2(self, *Locks::heap_bitmap_lock_);
heap_->ClearMarkedObjects();
}
bool ConcurrentCopying::IsMarkedHeapReference(mirror::HeapReference<mirror::Object>* field) {
mirror::Object* from_ref = field->AsMirrorPtr();
mirror::Object* to_ref = IsMarked(from_ref);
if (to_ref == nullptr) {
return false;
}
if (from_ref != to_ref) {
QuasiAtomic::ThreadFenceRelease();
field->Assign(to_ref);
QuasiAtomic::ThreadFenceSequentiallyConsistent();
}
return true;
}
mirror::Object* ConcurrentCopying::MarkObject(mirror::Object* from_ref) {
return Mark(from_ref);
}
void ConcurrentCopying::DelayReferenceReferent(mirror::Class* klass, mirror::Reference* reference) {
heap_->GetReferenceProcessor()->DelayReferenceReferent(klass, reference, this);
}
void ConcurrentCopying::ProcessReferences(Thread* self) {
TimingLogger::ScopedTiming split("ProcessReferences", GetTimings());
// We don't really need to lock the heap bitmap lock as we use CAS to mark in bitmaps.
WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
GetHeap()->GetReferenceProcessor()->ProcessReferences(
true /*concurrent*/, GetTimings(), GetCurrentIteration()->GetClearSoftReferences(), this);
}
void ConcurrentCopying::RevokeAllThreadLocalBuffers() {
TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings());
region_space_->RevokeAllThreadLocalBuffers();
}
} // namespace collector
} // namespace gc
} // namespace art