Revert of [heap] Concurrent store buffer processing.

src/heap/store-buffer.cc

Index: src/heap/store-buffer.cc
diff --git a/src/heap/store-buffer.cc b/src/heap/store-buffer.cc
index ffd5d96c5c663ce9f98fdc723352da07d209679c..a982eb3c40280f96d883c870161363f1a2656ae9 100644
--- a/src/heap/store-buffer.cc
+++ b/src/heap/store-buffer.cc
@@ -16,135 +16,62 @@
 namespace internal {
 
 StoreBuffer::StoreBuffer(Heap* heap)
-    : heap_(heap), top_(nullptr), current_(0), virtual_memory_(nullptr) {
-  for (int i = 0; i < kStoreBuffers; i++) {
-    start_[i] = nullptr;
-    limit_[i] = nullptr;
-    lazy_top_[i] = nullptr;
-  }
-  task_running_ = false;
-}
+    : heap_(heap),
+      top_(nullptr),
+      start_(nullptr),
+      limit_(nullptr),
+      virtual_memory_(nullptr) {}
 
 void StoreBuffer::SetUp() {
   // Allocate 3x the buffer size, so that we can start the new store buffer
   // aligned to 2x the size.  This lets us use a bit test to detect the end of
   // the area.
-  virtual_memory_ = new base::VirtualMemory(kStoreBufferSize * 3);
+  virtual_memory_ = new base::VirtualMemory(kStoreBufferSize * 2);
   uintptr_t start_as_int =
       reinterpret_cast<uintptr_t>(virtual_memory_->address());
-  start_[0] =
-      reinterpret_cast<Address*>(RoundUp(start_as_int, kStoreBufferSize));
-  limit_[0] = start_[0] + (kStoreBufferSize / kPointerSize);
-  start_[1] = limit_[0];
-  limit_[1] = start_[1] + (kStoreBufferSize / kPointerSize);
+  start_ = reinterpret_cast<Address*>(RoundUp(start_as_int, kStoreBufferSize));
+  limit_ = start_ + (kStoreBufferSize / kPointerSize);
 
+  DCHECK(reinterpret_cast<Address>(start_) >= virtual_memory_->address());
+  DCHECK(reinterpret_cast<Address>(limit_) >= virtual_memory_->address());
   Address* vm_limit = reinterpret_cast<Address*>(
       reinterpret_cast<char*>(virtual_memory_->address()) +
       virtual_memory_->size());
+  DCHECK(start_ <= vm_limit);
+  DCHECK(limit_ <= vm_limit);
+  USE(vm_limit);
+  DCHECK((reinterpret_cast<uintptr_t>(limit_) & kStoreBufferMask) == 0);
 
-  USE(vm_limit);
-  for (int i = 0; i < kStoreBuffers; i++) {
-    DCHECK(reinterpret_cast<Address>(start_[i]) >= virtual_memory_->address());
-    DCHECK(reinterpret_cast<Address>(limit_[i]) >= virtual_memory_->address());
-    DCHECK(start_[i] <= vm_limit);
-    DCHECK(limit_[i] <= vm_limit);
-    DCHECK((reinterpret_cast<uintptr_t>(limit_[i]) & kStoreBufferMask) == 0);
-  }
-
-  if (!virtual_memory_->Commit(reinterpret_cast<Address>(start_[0]),
-                               kStoreBufferSize * kStoreBuffers,
+  if (!virtual_memory_->Commit(reinterpret_cast<Address>(start_),
+                               kStoreBufferSize,
                                false)) {  // Not executable.
     V8::FatalProcessOutOfMemory("StoreBuffer::SetUp");
   }
-  current_ = 0;
-  top_ = start_[current_];
+  top_ = start_;
 }
 
 
 void StoreBuffer::TearDown() {
   delete virtual_memory_;
-  top_ = nullptr;
-  for (int i = 0; i < kStoreBuffers; i++) {
-    start_[i] = nullptr;
-    limit_[i] = nullptr;
-    lazy_top_[i] = nullptr;
-  }
+  top_ = start_ = limit_ = nullptr;
 }
 
 
 void StoreBuffer::StoreBufferOverflow(Isolate* isolate) {
-  isolate->heap()->store_buffer()->FlipStoreBuffers();
+  isolate->heap()->store_buffer()->MoveEntriesToRememberedSet();
   isolate->counters()->store_buffer_overflows()->Increment();
 }
 
-void StoreBuffer::FlipStoreBuffers() {
-  base::LockGuard<base::Mutex> guard(&mutex_);
-  int other = (current_ + 1) % kStoreBuffers;
-  MoveEntriesToRememberedSet(other);
-  lazy_top_[current_] = top_;
-  current_ = other;
-  top_ = start_[current_];
-
-  if (!task_running_) {
-    task_running_ = true;
-    Task* task = new Task(heap_->isolate(), this);
-    V8::GetCurrentPlatform()->CallOnBackgroundThread(
-        task, v8::Platform::kShortRunningTask);
-  }
-}
-
-void StoreBuffer::MoveEntriesToRememberedSet(int index) {
-  if (!lazy_top_[index]) return;
-  DCHECK_GE(index, 0);
-  DCHECK_LT(index, kStoreBuffers);
-  for (Address* current = start_[index]; current < lazy_top_[index];
-       current++) {
+void StoreBuffer::MoveEntriesToRememberedSet() {
+  if (top_ == start_) return;
+  DCHECK(top_ <= limit_);
+  for (Address* current = start_; current < top_; current++) {
     DCHECK(!heap_->code_space()->Contains(*current));
     Address addr = *current;
     Page* page = Page::FromAnyPointerAddress(heap_, addr);
-    if (IsDeletionAddress(addr)) {
-      current++;
-      Address end = *current;
-      DCHECK(!IsDeletionAddress(end));
-      addr = UnmarkDeletionAddress(addr);
-      if (end) {
-        RememberedSet<OLD_TO_NEW>::RemoveRange(page, addr, end,
-                                               SlotSet::PREFREE_EMPTY_BUCKETS);
-      } else {
-        RememberedSet<OLD_TO_NEW>::Remove(page, addr);
-      }
-    } else {
-      DCHECK(!IsDeletionAddress(addr));
-      RememberedSet<OLD_TO_NEW>::Insert(page, addr);
-    }
+    RememberedSet<OLD_TO_NEW>::Insert(page, addr);
   }
-  lazy_top_[index] = nullptr;
-}
-
-void StoreBuffer::MoveAllEntriesToRememberedSet() {
-  base::LockGuard<base::Mutex> guard(&mutex_);
-  int other = (current_ + 1) % kStoreBuffers;
-  MoveEntriesToRememberedSet(other);
-  lazy_top_[current_] = top_;
-  MoveEntriesToRememberedSet(current_);
-  top_ = start_[current_];
-}
-
-void StoreBuffer::ConcurrentlyProcessStoreBuffer() {
-  base::LockGuard<base::Mutex> guard(&mutex_);
-  int other = (current_ + 1) % kStoreBuffers;
-  MoveEntriesToRememberedSet(other);
-  task_running_ = false;
-}
-
-void StoreBuffer::DeleteEntry(Address start, Address end) {
-  if (top_ + sizeof(Address) * 2 > limit_[current_]) {
-    StoreBufferOverflow(heap_->isolate());
-  }
-  *top_ = MarkDeletionAddress(start);
-  top_++;
-  *top_ = end;
-  top_++;
+  top_ = start_;
 }
 
 }  // namespace internal