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// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_HEAP_LOCAL_ALLOCATOR_H_
#define V8_HEAP_LOCAL_ALLOCATOR_H_
#include "src/globals.h"
#include "src/heap/heap.h"
#include "src/heap/spaces.h"
namespace v8 {
namespace internal {
// Allocator encapsulating thread-local allocation. Assumes that all other
// allocations also go through LocalAllocator.
class LocalAllocator {
public:
static const int kLabSize = 32 * KB;
static const int kMaxLabObjectSize = 8 * KB;
explicit LocalAllocator(Heap* heap)
: heap_(heap),
new_space_(heap->new_space()),
compaction_spaces_(heap),
new_space_lab_(LocalAllocationBuffer::InvalidBuffer()),
lab_allocation_will_fail_(false) {}
// Needs to be called from the main thread to finalize this LocalAllocator.
void Finalize() {
heap_->old_space()->MergeCompactionSpace(compaction_spaces_.Get(OLD_SPACE));
heap_->code_space()->MergeCompactionSpace(
compaction_spaces_.Get(CODE_SPACE));
// Give back remaining LAB space if this LocalAllocator's new space LAB
// sits right next to new space allocation top.
const AllocationInfo info = new_space_lab_.Close();
const Address top = new_space_->top();
if (info.limit() != nullptr && info.limit() == top) {
DCHECK_NOT_NULL(info.top());
*new_space_->allocation_top_address() = info.top();
}
}
AllocationResult Allocate(AllocationSpace space, int object_size,
AllocationAlignment alignment) {
switch (space) {
case NEW_SPACE:
return AllocateInNewSpace(object_size, alignment);
case OLD_SPACE:
return compaction_spaces_.Get(OLD_SPACE)->AllocateRaw(object_size,
alignment);
case CODE_SPACE:
return compaction_spaces_.Get(CODE_SPACE)
->AllocateRaw(object_size, alignment);
default:
UNREACHABLE();
break;
}
}
void FreeLast(AllocationSpace space, HeapObject* object, int object_size) {
switch (space) {
case NEW_SPACE:
FreeLastInNewSpace(object, object_size);
return;
case OLD_SPACE:
FreeLastInOldSpace(object, object_size);
return;
default:
// Only new and old space supported.
UNREACHABLE();
break;
}
}
private:
AllocationResult AllocateInNewSpace(int object_size,
AllocationAlignment alignment) {
if (object_size > kMaxLabObjectSize) {
return new_space_->AllocateRawSynchronized(object_size, alignment);
}
return AllocateInLAB(object_size, alignment);
}
inline bool NewLocalAllocationBuffer() {
if (lab_allocation_will_fail_) return false;
LocalAllocationBuffer saved_lab_ = new_space_lab_;
AllocationResult result =
new_space_->AllocateRawSynchronized(kLabSize, kWordAligned);
new_space_lab_ = LocalAllocationBuffer::FromResult(heap_, result, kLabSize);
if (new_space_lab_.IsValid()) {
new_space_lab_.TryMerge(&saved_lab_);
return true;
}
new_space_lab_ = saved_lab_;
lab_allocation_will_fail_ = true;
return false;
}
AllocationResult AllocateInLAB(int object_size,
AllocationAlignment alignment) {
AllocationResult allocation;
if (!new_space_lab_.IsValid() && !NewLocalAllocationBuffer()) {
return AllocationResult::Retry(OLD_SPACE);
}
allocation = new_space_lab_.AllocateRawAligned(object_size, alignment);
if (allocation.IsRetry()) {
if (!NewLocalAllocationBuffer()) {
return AllocationResult::Retry(OLD_SPACE);
} else {
allocation = new_space_lab_.AllocateRawAligned(object_size, alignment);
CHECK(!allocation.IsRetry());
}
}
return allocation;
}
void FreeLastInNewSpace(HeapObject* object, int object_size) {
if (!new_space_lab_.TryFreeLast(object, object_size)) {
// We couldn't free the last object so we have to write a proper filler.
heap_->CreateFillerObjectAt(object->address(), object_size,
ClearRecordedSlots::kNo);
}
}
void FreeLastInOldSpace(HeapObject* object, int object_size) {
if (!compaction_spaces_.Get(OLD_SPACE)->TryFreeLast(object, object_size)) {
// We couldn't free the last object so we have to write a proper filler.
heap_->CreateFillerObjectAt(object->address(), object_size,
ClearRecordedSlots::kNo);
}
}
Heap* const heap_;
NewSpace* const new_space_;
CompactionSpaceCollection compaction_spaces_;
LocalAllocationBuffer new_space_lab_;
bool lab_allocation_will_fail_;
};
} // namespace internal
} // namespace v8
#endif // V8_HEAP_LOCAL_ALLOCATOR_H_
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