New page local store buffer.

src/heap/store-buffer.h

 // Copyright 2011 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_STORE_BUFFER_H_
 #define V8_STORE_BUFFER_H_
 
 #include "src/allocation.h"
 #include "src/base/logging.h"
 #include "src/base/platform/platform.h"
 #include "src/globals.h"
+#include "src/heap/slot-set.h"
 
 namespace v8 {
 namespace internal {
 
 class Page;
 class PagedSpace;
 class StoreBuffer;
 
 typedef void (*ObjectSlotCallback)(HeapObject** from, HeapObject* to);
 
 // Used to implement the write barrier by collecting addresses of pointers
 // between spaces.
 class StoreBuffer {
  public:
   explicit StoreBuffer(Heap* heap);
-
   static void StoreBufferOverflow(Isolate* isolate);
-
   void SetUp();
   void TearDown();
 
+  static const int kStoreBufferOverflowBit = 1 << (14 + kPointerSizeLog2);
+  static const int kStoreBufferSize = kStoreBufferOverflowBit;
+  static const int kStoreBufferLength = kStoreBufferSize / sizeof(Address);
+
   // This is used to add addresses to the store buffer non-concurrently.
   inline void Mark(Address addr);
 
   // This is used to add addresses to the store buffer when multiple threads
   // may operate on the store buffer.
   inline void MarkSynchronized(Address addr);
 
-  // This is used by the heap traversal to enter the addresses into the store
-  // buffer that should still be in the store buffer after GC.  It enters
-  // addresses directly into the old buffer because the GC starts by wiping the
-  // old buffer and thereafter only visits each cell once so there is no need
-  // to attempt to remove any dupes.  During the first part of a GC we
-  // are using the store buffer to access the old spaces and at the same time
-  // we are rebuilding the store buffer using this function.  There is, however
-  // no issue of overwriting the buffer we are iterating over, because this
-  // stage of the scavenge can only reduce the number of addresses in the store
-  // buffer (some objects are promoted so pointers to them do not need to be in
-  // the store buffer).  The later parts of the GC scan the pages that are
-  // exempt from the store buffer and process the promotion queue.  These steps
-  // can overflow this buffer.  We check for this and on overflow we call the
-  // callback set up with the StoreBufferRebuildScope object.
-  inline void EnterDirectlyIntoStoreBuffer(Address addr);
-
-  // Iterates over all pointers that go from old space to new space.  It will
-  // delete the store buffer as it starts so the callback should reenter
-  // surviving old-to-new pointers into the store buffer to rebuild it.
   void IteratePointersToNewSpace(ObjectSlotCallback callback);
 
-  static const int kStoreBufferOverflowBit = 1 << (14 + kPointerSizeLog2);
-  static const int kStoreBufferSize = kStoreBufferOverflowBit;
-  static const int kStoreBufferLength = kStoreBufferSize / sizeof(Address);
-  static const int kOldStoreBufferLength = kStoreBufferLength * 16;
-  static const int kHashSetLengthLog2 = 12;
-  static const int kHashSetLength = 1 << kHashSetLengthLog2;
-
-  void Compact();
-
-  void GCPrologue();
-  void GCEpilogue();
-
-  Object*** Limit() { return reinterpret_cast<Object***>(old_limit_); }
-  Object*** Start() { return reinterpret_cast<Object***>(old_start_); }
-  Object*** Top() { return reinterpret_cast<Object***>(old_top_); }
-  void SetTop(Object*** top) {
-    DCHECK(top >= Start());
-    DCHECK(top <= Limit());
-    old_top_ = reinterpret_cast<Address*>(top);
-  }
-
-  bool old_buffer_is_sorted() { return old_buffer_is_sorted_; }
-  bool old_buffer_is_filtered() { return old_buffer_is_filtered_; }
-
-  void EnsureSpace(intptr_t space_needed);
   void Verify();
 
-  bool PrepareForIteration();
-
-  void Filter(int flag);
-
   // Eliminates all stale store buffer entries from the store buffer, i.e.,
   // slots that are not part of live objects anymore. This method must be
   // called after marking, when the whole transitive closure is known and
   // must be called before sweeping when mark bits are still intact.
   void ClearInvalidStoreBufferEntries();
   void VerifyValidStoreBufferEntries();
 
  private:
   Heap* heap_;
 
   // The store buffer is divided up into a new buffer that is constantly being

[Michael Lippautz, 2016/01/21 10:07:32]

nit: This comment is now out of date.

[ulan, 2016/01/28 19:07:23]

Done.

   // filled by mutator activity and an old buffer that is filled with the data
   // from the new buffer after compression.
   Address* start_;
   Address* limit_;
 
-  Address* old_start_;
-  Address* old_limit_;
-  Address* old_top_;
-  Address* old_reserved_limit_;
-  base::VirtualMemory* old_virtual_memory_;
-
-  bool old_buffer_is_sorted_;
-  bool old_buffer_is_filtered_;
-  bool during_gc_;
-  // The garbage collector iterates over many pointers to new space that are not
-  // handled by the store buffer.  This flag indicates whether the pointers
-  // found by the callbacks should be added to the store buffer or not.
-  bool store_buffer_rebuilding_enabled_;
-  StoreBufferCallback callback_;
-  bool may_move_store_buffer_entries_;
-
   base::VirtualMemory* virtual_memory_;
 
-  // Two hash sets used for filtering.
-  // If address is in the hash set then it is guaranteed to be in the
-  // old part of the store buffer.
-  uintptr_t* hash_set_1_;
-  uintptr_t* hash_set_2_;
-  bool hash_sets_are_empty_;
-
   // Used for synchronization of concurrent store buffer access.
   base::Mutex mutex_;
 
-  void ClearFilteringHashSets();
+  void InsertEntriesFromBuffer();
 
-  bool SpaceAvailable(intptr_t space_needed);
-  void ExemptPopularPages(int prime_sample_step, int threshold);
+  inline uint32_t SlotAddressToOffset(Address slot_address, SlotSet** slots);
 
-  void ProcessOldToNewSlot(Address slot_address,
-                           ObjectSlotCallback slot_callback);
-
-  void FindPointersToNewSpaceInRegion(Address start, Address end,
-                                      ObjectSlotCallback slot_callback);
-
-  void IteratePointersInStoreBuffer(ObjectSlotCallback slot_callback);
+  template <typename Callback>
+  void Iterate(Callback callback);
 
 #ifdef VERIFY_HEAP
   void VerifyPointers(LargeObjectSpace* space);
 #endif
-
-  friend class DontMoveStoreBufferEntriesScope;
-  friend class FindPointersToNewSpaceVisitor;
-  friend class StoreBufferRebuildScope;
 };
 
 
-class StoreBufferRebuilder {
- public:
-  explicit StoreBufferRebuilder(StoreBuffer* store_buffer)
-      : store_buffer_(store_buffer) {}
-
-  void Callback(MemoryChunk* page, StoreBufferEvent event);
-
- private:
-  StoreBuffer* store_buffer_;
-
-  // We record in this variable how full the store buffer was when we started
-  // iterating over the current page, finding pointers to new space.  If the
-  // store buffer overflows again we can exempt the page from the store buffer
-  // by rewinding to this point instead of having to search the store buffer.
-  Object*** start_of_current_page_;
-  // The current page we are scanning in the store buffer iterator.
-  MemoryChunk* current_page_;
-};
-
-
-class StoreBufferRebuildScope {
- public:
-  explicit StoreBufferRebuildScope(Heap* heap, StoreBuffer* store_buffer,
-                                   StoreBufferCallback callback)
-      : store_buffer_(store_buffer),
-        stored_state_(store_buffer->store_buffer_rebuilding_enabled_),
-        stored_callback_(store_buffer->callback_) {
-    store_buffer_->store_buffer_rebuilding_enabled_ = true;
-    store_buffer_->callback_ = callback;
-    (*callback)(heap, NULL, kStoreBufferStartScanningPagesEvent);
-  }
-
-  ~StoreBufferRebuildScope() {
-    store_buffer_->callback_ = stored_callback_;
-    store_buffer_->store_buffer_rebuilding_enabled_ = stored_state_;
-  }
-
- private:
-  StoreBuffer* store_buffer_;
-  bool stored_state_;
-  StoreBufferCallback stored_callback_;
-};
-
-
-class DontMoveStoreBufferEntriesScope {
- public:
-  explicit DontMoveStoreBufferEntriesScope(StoreBuffer* store_buffer)
-      : store_buffer_(store_buffer),
-        stored_state_(store_buffer->may_move_store_buffer_entries_) {
-    store_buffer_->may_move_store_buffer_entries_ = false;
-  }
-
-  ~DontMoveStoreBufferEntriesScope() {
-    store_buffer_->may_move_store_buffer_entries_ = stored_state_;
-  }
-
- private:
-  StoreBuffer* store_buffer_;
-  bool stored_state_;
-};
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_STORE_BUFFER_H_