Compacting collector.
The compacting collector is currently similar to semispace. It works by
copying objects back and forth between two bump pointer spaces. There
are types of objects which are "non-movable" due to current runtime
limitations. These are Classes, Methods, and Fields.
Bump pointer spaces are a new type of continuous alloc space which have
no lock in the allocation code path. When you allocate from these it uses
atomic operations to increase an index. Traversing the objects in the bump
pointer space relies on Object::SizeOf matching the allocated size exactly.
Runtime changes:
JNI::GetArrayElements returns copies objects if you attempt to get the
backing data of a movable array. For GetArrayElementsCritical, we return
direct backing storage for any types of arrays, but temporarily disable
the GC until the critical region is completed.
Added a new runtime call called VisitObjects, this is used in place of
the old pattern which was flushing the allocation stack and walking
the bitmaps.
Changed image writer to be compaction safe and use object monitor word
for forwarding addresses.
Added a bunch of added SIRTs to ClassLinker, MethodLinker, etc..
TODO: Enable switching allocators, compacting on background, etc..
Bug: 8981901
Change-Id: I3c886fd322a6eef2b99388d19a765042ec26ab99
diff --git a/compiler/image_writer.h b/compiler/image_writer.h
index 0b408e8..695f59b 100644
--- a/compiler/image_writer.h
+++ b/compiler/image_writer.h
@@ -63,31 +63,11 @@
void RecordImageAllocations() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// We use the lock word to store the offset of the object in the image.
- void AssignImageOffset(mirror::Object* object)
- SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
- DCHECK(object != NULL);
- SetImageOffset(object, image_end_);
- image_end_ += RoundUp(object->SizeOf(), 8); // 64-bit alignment
- DCHECK_LT(image_end_, image_->Size());
- }
-
- void SetImageOffset(mirror::Object* object, size_t offset) {
- DCHECK(object != NULL);
- DCHECK_NE(offset, 0U);
- DCHECK(!IsImageOffsetAssigned(object));
- offsets_.Put(object, offset);
- }
-
- size_t IsImageOffsetAssigned(const mirror::Object* object) const {
- DCHECK(object != NULL);
- return offsets_.find(object) != offsets_.end();
- }
-
- size_t GetImageOffset(const mirror::Object* object) const {
- DCHECK(object != NULL);
- DCHECK(IsImageOffsetAssigned(object));
- return offsets_.find(object)->second;
- }
+ void AssignImageOffset(mirror::Object* object) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+ void SetImageOffset(mirror::Object* object, size_t offset)
+ SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+ bool IsImageOffsetAssigned(const mirror::Object* object) const;
+ size_t GetImageOffset(const mirror::Object* object) const;
mirror::Object* GetImageAddress(const mirror::Object* object) const {
if (object == NULL) {
@@ -147,7 +127,14 @@
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
mirror::ObjectArray<mirror::Object>* CreateImageRoots() const
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
- static void CalculateNewObjectOffsetsCallback(mirror::Object* obj, void* arg)
+ void CalculateObjectOffsets(mirror::Object* obj)
+ SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+
+ void WalkInstanceFields(mirror::Object* obj, mirror::Class* klass)
+ SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+ void WalkFieldsInOrder(mirror::Object* obj)
+ SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+ static void WalkFieldsCallback(mirror::Object* obj, void* arg)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Creates the contiguous image in memory and adjusts pointers.
@@ -180,9 +167,6 @@
const CompilerDriver& compiler_driver_;
- // Map of Object to where it will be at runtime.
- SafeMap<const mirror::Object*, size_t> offsets_;
-
// oat file with code for this image
OatFile* oat_file_;
@@ -195,6 +179,9 @@
// Beginning target image address for the output image.
byte* image_begin_;
+ // Saved hashes (objects are inside of the image so that they don't move).
+ std::vector<std::pair<mirror::Object*, uint32_t> > saved_hashes_;
+
// Beginning target oat address for the pointers from the output image to its oat file.
const byte* oat_data_begin_;
@@ -211,9 +198,6 @@
uint32_t quick_imt_conflict_trampoline_offset_;
uint32_t quick_resolution_trampoline_offset_;
uint32_t quick_to_interpreter_bridge_offset_;
-
- // DexCaches seen while scanning for fixing up CodeAndDirectMethods
- std::set<mirror::DexCache*> dex_caches_;
};
} // namespace art