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* Copyright (C) 2013 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <memory>
#include "atomic.h"
#include "base/macros.h"
#include "base/mutex.h"
#include "garbage_collector.h"
#include "gc/accounting/heap_bitmap.h"
#include "immune_region.h"
#include "object_callbacks.h"
#include "offsets.h"
namespace art {
class Thread;
namespace mirror {
class Class;
class Object;
} // namespace mirror
namespace gc {
class Heap;
namespace accounting {
template <typename T> class AtomicStack;
typedef AtomicStack<mirror::Object*> ObjectStack;
} // namespace accounting
namespace space {
class ContinuousMemMapAllocSpace;
class ContinuousSpace;
} // namespace space
namespace collector {
class SemiSpace : public GarbageCollector {
// If true, use remembered sets in the generational mode.
static constexpr bool kUseRememberedSet = true;
explicit SemiSpace(Heap* heap, bool generational = false, const std::string& name_prefix = "");
~SemiSpace() {}
virtual void InitializePhase();
virtual void MarkingPhase() EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_)
virtual void ReclaimPhase() EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_)
virtual void FinishPhase() EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_);
void MarkReachableObjects()
EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_, Locks::heap_bitmap_lock_);
virtual GcType GetGcType() const OVERRIDE {
return kGcTypePartial;
virtual CollectorType GetCollectorType() const OVERRIDE {
return generational_ ? kCollectorTypeGSS : kCollectorTypeSS;
// Sets which space we will be copying objects to.
void SetToSpace(space::ContinuousMemMapAllocSpace* to_space);
// Set the space where we copy objects from.
void SetFromSpace(space::ContinuousMemMapAllocSpace* from_space);
// Set whether or not we swap the semi spaces in the heap. This needs to be done with mutators
// suspended.
void SetSwapSemiSpaces(bool swap_semi_spaces) {
swap_semi_spaces_ = swap_semi_spaces;
// Initializes internal structures.
void Init();
// Find the default mark bitmap.
void FindDefaultMarkBitmap();
// Returns the new address of the object.
template<bool kPoisonReferences>
void MarkObject(mirror::ObjectReference<kPoisonReferences, mirror::Object>* obj_ptr)
EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
void ScanObject(mirror::Object* obj)
EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
void VerifyNoFromSpaceReferences(mirror::Object* obj)
SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
// Marks the root set at the start of a garbage collection.
void MarkRoots()
EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
// Bind the live bits to the mark bits of bitmaps for spaces that are never collected, ie
// the image. Mark that portion of the heap as immune.
virtual void BindBitmaps() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
void UnBindBitmaps()
void ProcessReferences(Thread* self) EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_)
// Sweeps unmarked objects to complete the garbage collection.
virtual void Sweep(bool swap_bitmaps) EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
// Sweeps unmarked objects to complete the garbage collection.
void SweepLargeObjects(bool swap_bitmaps) EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
void SweepSystemWeaks()
SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
static void MarkRootCallback(mirror::Object** root, void* arg, uint32_t /*tid*/,
RootType /*root_type*/)
EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
static mirror::Object* MarkObjectCallback(mirror::Object* root, void* arg)
EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
static void MarkHeapReferenceCallback(mirror::HeapReference<mirror::Object>* obj_ptr, void* arg)
EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
static void ProcessMarkStackCallback(void* arg)
EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_, Locks::heap_bitmap_lock_);
static void DelayReferenceReferentCallback(mirror::Class* klass, mirror::Reference* ref,
void* arg)
SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
virtual mirror::Object* MarkNonForwardedObject(mirror::Object* obj)
EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
// Schedules an unmarked object for reference processing.
void DelayReferenceReferent(mirror::Class* klass, mirror::Reference* reference)
SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
// Returns null if the object is not marked, otherwise returns the forwarding address (same as
// object for non movable things).
mirror::Object* GetMarkedForwardAddress(mirror::Object* object) const
static bool HeapReferenceMarkedCallback(mirror::HeapReference<mirror::Object>* object, void* arg)
static mirror::Object* MarkedForwardingAddressCallback(mirror::Object* object, void* arg)
// Marks or unmarks a large object based on whether or not set is true. If set is true, then we
// mark, otherwise we unmark.
bool MarkLargeObject(const mirror::Object* obj)
// Expand mark stack to 2x its current size.
void ResizeMarkStack(size_t new_size);
// Returns true if we should sweep the space.
virtual bool ShouldSweepSpace(space::ContinuousSpace* space) const;
// Push an object onto the mark stack.
void MarkStackPush(mirror::Object* obj);
void UpdateAndMarkModUnion()
// Recursively blackens objects on the mark stack.
void ProcessMarkStack()
EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_, Locks::heap_bitmap_lock_);
inline mirror::Object* GetForwardingAddressInFromSpace(mirror::Object* obj) const
// Revoke all the thread-local buffers.
void RevokeAllThreadLocalBuffers();
// Current space, we check this space first to avoid searching for the appropriate space for an
// object.
accounting::ObjectStack* mark_stack_;
// Immune region, every object inside the immune region is assumed to be marked.
ImmuneRegion immune_region_;
// If true, the large object space is immune.
bool is_large_object_space_immune_;
// Destination and source spaces (can be any type of ContinuousMemMapAllocSpace which either has
// a live bitmap or doesn't).
space::ContinuousMemMapAllocSpace* to_space_;
// Cached live bitmap as an optimization.
accounting::ContinuousSpaceBitmap* to_space_live_bitmap_;
space::ContinuousMemMapAllocSpace* from_space_;
// Cached mark bitmap as an optimization.
accounting::HeapBitmap* mark_bitmap_;
Thread* self_;
// When true, the generational mode (promotion and the bump pointer
// space only collection) is enabled. TODO: move these to a new file
// as a new garbage collector?
const bool generational_;
// Used for the generational mode. the end/top of the bump
// pointer space at the end of the last collection.
byte* last_gc_to_space_end_;
// Used for the generational mode. During a collection, keeps track
// of how many bytes of objects have been copied so far from the
// bump pointer space to the non-moving space.
uint64_t bytes_promoted_;
// Used for the generational mode. Keeps track of how many bytes of
// objects have been copied so far from the bump pointer space to
// the non-moving space, since the last whole heap collection.
uint64_t bytes_promoted_since_last_whole_heap_collection_;
// Used for the generational mode. Keeps track of how many bytes of
// large objects were allocated at the last whole heap collection.
uint64_t large_object_bytes_allocated_at_last_whole_heap_collection_;
// Used for generational mode. When true, we only collect the from_space_.
bool collect_from_space_only_;
// The space which we are promoting into, only used for GSS.
space::ContinuousMemMapAllocSpace* promo_dest_space_;
// The space which we copy to if the to_space_ is full.
space::ContinuousMemMapAllocSpace* fallback_space_;
// How many objects and bytes we moved, used so that we don't need to Get the size of the
// to_space_ when calculating how many objects and bytes we freed.
size_t bytes_moved_;
size_t objects_moved_;
// How many bytes we avoided dirtying.
size_t saved_bytes_;
// The name of the collector.
std::string collector_name_;
// Used for the generational mode. The default interval of the whole
// heap collection. If N, the whole heap collection occurs every N
// collections.
static constexpr int kDefaultWholeHeapCollectionInterval = 5;
// Whether or not we swap the semi spaces in the heap during the marking phase.
bool swap_semi_spaces_;
friend class BitmapSetSlowPathVisitor;
} // namespace collector
} // namespace gc
} // namespace art