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Unified Diff: src/heap/array-buffer-tracker.h

Issue 2009893003: Revert of "[heap] Fine-grained JSArrayBuffer tracking" (Closed) Base URL: https://chromium.googlesource.com/v8/v8.git@master
Patch Set: Created 4 years, 7 months ago
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Index: src/heap/array-buffer-tracker.h
diff --git a/src/heap/array-buffer-tracker.h b/src/heap/array-buffer-tracker.h
index 351924be66dce71932a2d1c99b48770f4de08e61..6130003d15263fff94d56070d44a4713858ab9da 100644
--- a/src/heap/array-buffer-tracker.h
+++ b/src/heap/array-buffer-tracker.h
@@ -15,112 +15,61 @@
// Forward declarations.
class Heap;
-class Page;
class JSArrayBuffer;
-
-// LocalArrayBufferTracker is tracker for live and dead JSArrayBuffer objects.
-//
-// It consists of two sets, a live, and a not yet discovered set of buffers.
-// Upon registration (in the ArrayBufferTracker) the buffers are added to both
-// sets. When a buffer is encountered as live (or added is live) it is removed
-// from the not yet discovered set. Finally, after each round (sometime during
-// GC) the left over not yet discovered buffers are cleaned up. Upon starting
-// a new round the not yet discovered buffers are initialized from the live set.
-//
-// Caveats:
-// - Between cleaning up the buffers using |Free| we always need a |Reset| and
-// thus another marking phase.
-// - LocalArrayBufferTracker is completely unlocked. Calls need to ensure
-// exclusive access.
-class LocalArrayBufferTracker {
- public:
- typedef std::pair<void*, size_t> Value;
- typedef JSArrayBuffer* Key;
-
- enum LivenessIndicator { kForwardingPointer, kMarkBit };
- enum CallbackResult { kKeepEntry, kKeepAndUpdateEntry, kRemoveEntry };
-
- explicit LocalArrayBufferTracker(Heap* heap) : heap_(heap), started_(false) {}
- ~LocalArrayBufferTracker();
-
- void Add(Key key, const Value& value);
- void AddLive(Key key, const Value& value);
- Value Remove(Key key);
- void MarkLive(Key key);
- bool IsEmpty();
-
- // Resets the tracking set, i.e., not yet discovered buffers are initialized
- // from the remaining live set of buffers.
- void Reset();
-
- // Frees up any dead backing stores of not yet discovered array buffers.
- // Requires that the buffers have been properly marked using MarkLive.
- void FreeDead();
-
- // Scans the whole tracker and decides based on liveness_indicator whether
- // a JSArrayBuffer is still considered live.
- template <LivenessIndicator liveness_indicator>
- inline void ScanAndFreeDead();
-
- bool IsTracked(Key key) { return live_.find(key) != live_.end(); }
-
- private:
- // TODO(mlippautz): Switch to unordered_map once it is supported on all
- // platforms.
- typedef std::map<Key, Value> TrackingMap;
-
- // Processes buffers one by one. The CallbackResult decides whether the buffer
- // will be dropped or not.
- //
- // Callback should be of type:
- // CallbackResult fn(JSArrayBuffer*, JSArrayBuffer**);
- template <typename Callback>
- inline void Process(Callback callback);
-
- Heap* heap_;
-
- // |live_| maps tracked JSArrayBuffers to the internally allocated backing
- // store and length. For each GC round |not_yet_discovered_| is initialized
- // as a copy of |live_|. Upon finding a JSArrayBuffer during GC, the buffer
- // is removed from |not_yet_discovered_|. At the end of a GC, we free up the
- // remaining JSArrayBuffers in |not_yet_discovered_|.
- TrackingMap live_;
- TrackingMap not_yet_discovered_;
-
- bool started_;
-};
class ArrayBufferTracker {
public:
explicit ArrayBufferTracker(Heap* heap) : heap_(heap) {}
~ArrayBufferTracker();
+ inline Heap* heap() { return heap_; }
+
// The following methods are used to track raw C++ pointers to externally
// allocated memory used as backing store in live array buffers.
- // Register/unregister a new JSArrayBuffer |buffer| for tracking.
+ // A new ArrayBuffer was created with |data| as backing store.
void RegisterNew(JSArrayBuffer* buffer);
+
+ // The backing store |data| is no longer owned by V8.
void Unregister(JSArrayBuffer* buffer);
- // Frees all backing store pointers for dead JSArrayBuffers in new space.
- void FreeDeadInNewSpace();
-
- void FreeDead(Page* page);
-
- template <LocalArrayBufferTracker::LivenessIndicator liveness_indicator>
- void ScanAndFreeDeadArrayBuffers(Page* page);
-
- // A live JSArrayBuffer was discovered during marking.
+ // A live ArrayBuffer was discovered during marking/scavenge.
void MarkLive(JSArrayBuffer* buffer);
- // Resets all trackers in old space. Is required to be called from the main
- // thread.
- void ResetTrackersInOldSpace();
+ // Frees all backing store pointers that weren't discovered in the previous
+ // marking or scavenge phase.
+ void FreeDead(bool from_scavenge);
+
+ // Prepare for a new scavenge phase. A new marking phase is implicitly
+ // prepared by finishing the previous one.
+ void PrepareDiscoveryInNewSpace();
+
+ // An ArrayBuffer moved from new space to old space.
+ void Promote(JSArrayBuffer* buffer);
private:
+ base::Mutex mutex_;
Heap* heap_;
+
+ // |live_array_buffers_| maps externally allocated memory used as backing
+ // store for ArrayBuffers to the length of the respective memory blocks.
+ //
+ // At the beginning of mark/compact, |not_yet_discovered_array_buffers_| is
+ // a copy of |live_array_buffers_| and we remove pointers as we discover live
+ // ArrayBuffer objects during marking. At the end of mark/compact, the
+ // remaining memory blocks can be freed.
+ std::map<void*, size_t> live_array_buffers_;
+ std::map<void*, size_t> not_yet_discovered_array_buffers_;
+
+ // To be able to free memory held by ArrayBuffers during scavenge as well, we
+ // have a separate list of allocated memory held by ArrayBuffers in new space.
+ //
+ // Since mark/compact also evacuates the new space, all pointers in the
+ // |live_array_buffers_for_scavenge_| list are also in the
+ // |live_array_buffers_| list.
+ std::map<void*, size_t> live_array_buffers_for_scavenge_;
+ std::map<void*, size_t> not_yet_discovered_array_buffers_for_scavenge_;
};
-
} // namespace internal
} // namespace v8
#endif // V8_HEAP_ARRAY_BUFFER_TRACKER_H_
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