AuroraMiddleware/v8
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Remove lazy sweeping of new space and corresponding complicated pointer updating logic.

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We can do that now since we have the invariant that the store buffer always has valid slots after marking.

BUG=

Review URL: https://codereview.chromium.org/991853002

Cr-Commit-Position: refs/heads/master@{#27105}
This commit is contained in:
hpayer 2015-03-10 06:42:15 -07:00 committed by Commit bot
parent 0fd9bf8f14
commit 02ce445394
4 changed files with 25 additions and 68 deletions
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25
src/heap/mark-compact.cc
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@ -3008,19 +3008,15 @@ void PointersUpdatingVisitor::CheckLayoutDescriptorAndDie(Heap* heap,
static void UpdatePointer(HeapObject** address, HeapObject* object) {
Address new_addr = Memory::Address_at(object->address());
// The new space sweep will overwrite the map word of dead objects
// with NULL. In this case we do not need to transfer this entry to
// the store buffer which we are rebuilding.
// We perform the pointer update with a no barrier compare-and-swap. The
// compare and swap may fail in the case where the pointer update tries to
// update garbage memory which was concurrently accessed by the sweeper.
if (new_addr != NULL) {
base::NoBarrier_CompareAndSwap(
reinterpret_cast<base::AtomicWord*>(address),
reinterpret_cast<base::AtomicWord>(object),
reinterpret_cast<base::AtomicWord>(HeapObject::FromAddress(new_addr)));
MapWord map_word = object->map_word();
// The store buffer can still contain stale pointers in dead large objects.
// Ignore these pointers here.
DCHECK(map_word.IsForwardingAddress() ||
object->GetHeap()->lo_space()->FindPage(
reinterpret_cast<Address>(address)) != NULL);
if (map_word.IsForwardingAddress()) {
// Update the corresponding slot.
*address = map_word.ToForwardingAddress();
}
}
@ -3652,8 +3648,7 @@ void MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
GCTracer::Scope::MC_UPDATE_OLD_TO_NEW_POINTERS);
StoreBufferRebuildScope scope(heap_, heap_->store_buffer(),
&Heap::ScavengeStoreBufferCallback);
heap_->store_buffer()->IteratePointersToNewSpaceAndClearMaps(
&UpdatePointer);
heap_->store_buffer()->IteratePointersToNewSpace(&UpdatePointer);
}
{

8
src/heap/store-buffer-inl.h
View File

@ -49,14 +49,6 @@ void StoreBuffer::EnterDirectlyIntoStoreBuffer(Address addr) {
}
}
}
void StoreBuffer::ClearDeadObject(HeapObject* object) {
Address& map_field = Memory::Address_at(object->address());
if (heap_->map_space()->Contains(map_field)) {
map_field = NULL;
}
}
}
} // namespace v8::internal

40
src/heap/store-buffer.cc
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@ -379,8 +379,7 @@ void StoreBuffer::GCEpilogue() {
void StoreBuffer::ProcessOldToNewSlot(Address slot_address,
ObjectSlotCallback slot_callback,
bool clear_maps) {
ObjectSlotCallback slot_callback) {
Object** slot = reinterpret_cast<Object**>(slot_address);
Object* object = reinterpret_cast<Object*>(
base::NoBarrier_Load(reinterpret_cast<base::AtomicWord*>(slot)));
@ -390,9 +389,6 @@ void StoreBuffer::ProcessOldToNewSlot(Address slot_address,
if (heap_->InFromSpace(object)) {
HeapObject* heap_object = reinterpret_cast<HeapObject*>(object);
DCHECK(heap_object->IsHeapObject());
// The new space object was not promoted if it still contains a map
// pointer. Clear the map field now lazily (during full GC).
if (clear_maps) ClearDeadObject(heap_object);
slot_callback(reinterpret_cast<HeapObject**>(slot), heap_object);
object = reinterpret_cast<Object*>(
base::NoBarrier_Load(reinterpret_cast<base::AtomicWord*>(slot)));
@ -408,17 +404,16 @@ void StoreBuffer::ProcessOldToNewSlot(Address slot_address,
void StoreBuffer::FindPointersToNewSpaceInRegion(
Address start, Address end, ObjectSlotCallback slot_callback,
bool clear_maps) {
Address start, Address end, ObjectSlotCallback slot_callback) {
for (Address slot_address = start; slot_address < end;
slot_address += kPointerSize) {
ProcessOldToNewSlot(slot_address, slot_callback, clear_maps);
ProcessOldToNewSlot(slot_address, slot_callback);
}
}
void StoreBuffer::IteratePointersInStoreBuffer(ObjectSlotCallback slot_callback,
bool clear_maps) {
void StoreBuffer::IteratePointersInStoreBuffer(
ObjectSlotCallback slot_callback) {
Address* limit = old_top_;
old_top_ = old_start_;
{
@ -427,7 +422,7 @@ void StoreBuffer::IteratePointersInStoreBuffer(ObjectSlotCallback slot_callback,
#ifdef DEBUG
Address* saved_top = old_top_;
#endif
ProcessOldToNewSlot(*current, slot_callback, clear_maps);
ProcessOldToNewSlot(*current, slot_callback);
DCHECK(old_top_ == saved_top + 1 || old_top_ == saved_top);
}
}
@ -478,18 +473,6 @@ void StoreBuffer::VerifyValidStoreBufferEntries() {
void StoreBuffer::IteratePointersToNewSpace(ObjectSlotCallback slot_callback) {
IteratePointersToNewSpace(slot_callback, false);
}
void StoreBuffer::IteratePointersToNewSpaceAndClearMaps(
ObjectSlotCallback slot_callback) {
IteratePointersToNewSpace(slot_callback, true);
}
void StoreBuffer::IteratePointersToNewSpace(ObjectSlotCallback slot_callback,
bool clear_maps) {
// We do not sort or remove duplicated entries from the store buffer because
// we expect that callback will rebuild the store buffer thus removing
// all duplicates and pointers to old space.
@ -498,7 +481,7 @@ void StoreBuffer::IteratePointersToNewSpace(ObjectSlotCallback slot_callback,
// TODO(gc): we want to skip slots on evacuation candidates
// but we can't simply figure that out from slot address
// because slot can belong to a large object.
IteratePointersInStoreBuffer(slot_callback, clear_maps);
IteratePointersInStoreBuffer(slot_callback);
// We are done scanning all the pointers that were in the store buffer, but
// there may be some pages marked scan_on_scavenge that have pointers to new
@ -527,7 +510,7 @@ void StoreBuffer::IteratePointersToNewSpace(ObjectSlotCallback slot_callback,
DCHECK(array->IsFixedArray());
Address start = array->address();
Address end = start + array->Size();
FindPointersToNewSpaceInRegion(start, end, slot_callback, clear_maps);
FindPointersToNewSpaceInRegion(start, end, slot_callback);
} else {
Page* page = reinterpret_cast<Page*>(chunk);
PagedSpace* owner = reinterpret_cast<PagedSpace*>(page->owner());
@ -542,7 +525,7 @@ void StoreBuffer::IteratePointersToNewSpace(ObjectSlotCallback slot_callback,
FindPointersToNewSpaceInRegion(
heap_object->address() + Map::kPointerFieldsBeginOffset,
heap_object->address() + Map::kPointerFieldsEndOffset,
slot_callback, clear_maps);
slot_callback);
}
}
} else {
@ -577,8 +560,7 @@ void StoreBuffer::IteratePointersToNewSpace(ObjectSlotCallback slot_callback,
&end_of_region_offset)) {
FindPointersToNewSpaceInRegion(
obj_address + offset,
obj_address + end_of_region_offset, slot_callback,
clear_maps);
obj_address + end_of_region_offset, slot_callback);
}
offset = end_of_region_offset;
}
@ -588,7 +570,7 @@ void StoreBuffer::IteratePointersToNewSpace(ObjectSlotCallback slot_callback,
Address end_address = obj_address + end_offset;
// Object has only tagged fields.
FindPointersToNewSpaceInRegion(start_address, end_address,
slot_callback, clear_maps);
slot_callback);
#if V8_DOUBLE_FIELDS_UNBOXING
}
#endif

20
src/heap/store-buffer.h
View File

@ -20,8 +20,7 @@ class StoreBuffer;
typedef void (*ObjectSlotCallback)(HeapObject** from, HeapObject* to);
typedef void (StoreBuffer::*RegionCallback)(Address start, Address end,
ObjectSlotCallback slot_callback,
bool clear_maps);
ObjectSlotCallback slot_callback);
// Used to implement the write barrier by collecting addresses of pointers
// between spaces.
@ -60,10 +59,6 @@ class StoreBuffer {
// surviving old-to-new pointers into the store buffer to rebuild it.
void IteratePointersToNewSpace(ObjectSlotCallback callback);
// Same as IteratePointersToNewSpace but additonally clears maps in objects
// referenced from the store buffer that do not contain a forwarding pointer.
void IteratePointersToNewSpaceAndClearMaps(ObjectSlotCallback callback);
static const int kStoreBufferOverflowBit = 1 << (14 + kPointerSizeLog2);
static const int kStoreBufferSize = kStoreBufferOverflowBit;
static const int kStoreBufferLength = kStoreBufferSize / sizeof(Address);
@ -152,17 +147,11 @@ class StoreBuffer {
void Uniq();
void ExemptPopularPages(int prime_sample_step, int threshold);
// Set the map field of the object to NULL if contains a map.
inline void ClearDeadObject(HeapObject* object);
void ProcessOldToNewSlot(Address slot_address,
ObjectSlotCallback slot_callback, bool clear_maps);
void IteratePointersToNewSpace(ObjectSlotCallback callback, bool clear_maps);
ObjectSlotCallback slot_callback);
void FindPointersToNewSpaceInRegion(Address start, Address end,
ObjectSlotCallback slot_callback,
bool clear_maps);
ObjectSlotCallback slot_callback);
// For each region of pointers on a page in use from an old space call
// visit_pointer_region callback.
@ -173,8 +162,7 @@ class StoreBuffer {
RegionCallback region_callback,
ObjectSlotCallback slot_callback);
void IteratePointersInStoreBuffer(ObjectSlotCallback slot_callback,
bool clear_maps);
void IteratePointersInStoreBuffer(ObjectSlotCallback slot_callback);
#ifdef VERIFY_HEAP
void VerifyPointers(LargeObjectSpace* space);