[heap] Simplify heuristics for incremental step size.

src/heap/incremental-marking.h

 // Copyright 2012 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_INCREMENTAL_MARKING_H_
 #define V8_HEAP_INCREMENTAL_MARKING_H_
 
 #include "src/cancelable-task.h"
 #include "src/execution.h"
 #include "src/heap/heap.h"
@@ skipping 105 matching lines @@
                                    StepActions step_actions);
 
   // It's hard to know how much work the incremental marker should do to make
   // progress in the face of the mutator creating new work for it.  We start
   // of at a moderate rate of work and gradually increase the speed of the
   // incremental marker until it completes.
   // Do some marking every time this much memory has been allocated or that many
   // heavy (color-checking) write barriers have been invoked.
   static const intptr_t kAllocatedThreshold = 65536;
   static const intptr_t kWriteBarriersInvokedThreshold = 32768;
-  // Start off by marking this many times more memory than has been allocated.
-  static const intptr_t kInitialMarkingSpeed = 1;
-  // But if we are promoting a lot of data we need to mark faster to keep up
-  // with the data that is entering the old space through promotion.
-  static const intptr_t kFastMarking = 3;
-  // After this many steps we increase the marking/allocating factor.
-  static const intptr_t kMarkingSpeedAccellerationInterval = 1024;
-  // This is how much we increase the marking/allocating factor by.
-  static const intptr_t kMarkingSpeedAccelleration = 2;
-  static const intptr_t kMaxMarkingSpeed = 1000;
+  // Cap the write barrier counter to avoid overflows.
+  static const intptr_t kMaxWriteBarrierCounter = 1 << 20;
+  // These constants are arbitrary and chosen based on benchmarks.
+  static const intptr_t kBytesToMarkPerAllocatedByte = 3;
+  static const intptr_t kBytesToMarkPerWriteBarrier = 10;
+  static const intptr_t kMinIncrementalStepDurationInMs = 1;
 
   // This is the upper bound for how many times we allow finalization of
   // incremental marking to be postponed.
   static const size_t kMaxIdleMarkingDelayCounter = 3;
 
   void FinalizeSweeping();
 
   void OldSpaceStep(intptr_t allocated);
 
   intptr_t Step(intptr_t allocated, CompletionAction action,
@@ skipping 34 matching lines @@
   }
 
   inline void SetNewSpacePageFlags(Page* chunk) {
     SetNewSpacePageFlags(chunk, IsMarking());
   }
 
   bool IsCompacting() { return IsMarking() && is_compacting_; }
 
   void ActivateGeneratedStub(Code* stub);
 
-  void NotifyOfHighPromotionRate();
-
   void NotifyIncompleteScanOfObject(int unscanned_bytes) {
     unscanned_bytes_of_large_object_ = unscanned_bytes;
   }
 
   void ClearIdleMarkingDelayCounter();
 
   bool IsIdleMarkingDelayCounterLimitReached();
 
   static void MarkGrey(Heap* heap, HeapObject* object);
 
@@ skipping 46 matching lines @@
       incremental_marking_.Step(bytes_allocated,
                                 IncrementalMarking::GC_VIA_STACK_GUARD);
     }
 
    private:
     IncrementalMarking& incremental_marking_;
   };
 
   int64_t SpaceLeftInOldSpace();
 
-  void SpeedUp();
-
   void ResetStepCounters();
 
   void StartMarking();
 
   void StartBlackAllocation();
   void FinishBlackAllocation();
 
   void MarkRoots();
   void MarkObjectGroups();
   void ProcessWeakCells();
@@ skipping 24 matching lines @@
 
   void IncrementIdleMarkingDelayCounter();
 
   Heap* heap_;
 
   Observer observer_;
 
   State state_;
   bool is_compacting_;
 
-  int steps_count_;
-  int64_t old_generation_space_available_at_start_of_incremental_;
-  int64_t old_generation_space_used_at_start_of_incremental_;
-  int64_t bytes_rescanned_;
   bool should_hurry_;
-  int marking_speed_;
-  intptr_t bytes_scanned_;
   intptr_t allocated_;
   intptr_t write_barriers_invoked_since_last_step_;
   size_t idle_marking_delay_counter_;
 
   int unscanned_bytes_of_large_object_;
 
   bool was_activated_;
 
   bool black_allocation_;
 
   bool finalize_marking_completed_;
 
   int incremental_marking_finalization_rounds_;
 
   GCRequestType request_type_;
 
   IncrementalMarkingJob incremental_marking_job_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(IncrementalMarking);
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_INCREMENTAL_MARKING_H_