Revert of Replace reduce-memory mode in idle notification with delayed clean-up GC.

src/heap/memory-reducer.h

-// Copyright 2015 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_memory_reducer_H
-#define V8_HEAP_memory_reducer_H
-
-#include "include/v8-platform.h"
-#include "src/base/macros.h"
-
-namespace v8 {
-namespace internal {
-
-class Heap;
-
-
-// The goal of the MemoryReducer class is to detect transition of the mutator
-// from high allocation phase to low allocation phase and to collect potential
-// garbage created in the high allocation phase.
-//
-// The class implements an automaton with the following states and transitions.
-//
-// States:
-// - DONE
-// - WAIT <started_gcs> <next_gc_start_ms>
-// - RUN <started_gcs>
-// The <started_gcs> is an integer in range from 0..kMaxNumberOfGCs that stores
-// the number of GCs initiated by the MemoryReducer since it left the DONE
-// state.
-// The <next_gc_start_ms> is a double that stores the earliest time the next GC
-// can be initiated by the MemoryReducer.
-// The DONE state means that the MemoryReducer is not active.
-// The WAIT state means that the MemoryReducer is waiting for mutator allocation
-// rate to drop. The check for the allocation rate happens in the timer task
-// callback.
-// The RUN state means that the MemoryReducer started incremental marking and is
-// waiting for it to finish. Incremental marking steps are performed as usual
-// in the idle notification and in the mutator.
-//
-// Transitions:
-// DONE -> WAIT 0 (now_ms + long_delay_ms) happens:
-//     - on context disposal,
-//     - at the end of mark-compact GC initiated by the mutator.
-// This signals that there is potential garbage to be collected.
-//
-// WAIT n x -> WAIT n (now_ms + long_delay_ms) happens:
-//     - on mark-compact GC initiated by the mutator,
-//     - in the timer callback if the mutator allocation rate is high or
-//       incremental GC is in progress.
-//
-// WAIT n x -> RUN (n+1) happens:
-//     - in the timer callback if the mutator allocation rate is low
-//       and now_ms >= x and there is no incremental GC in progress.
-// The MemoryReducer starts incremental marking on this transition.
-//
-// RUN n -> DONE happens:
-//     - at end of the incremental GC initiated by the MemoryReducer if
-//       (n > 1 and there is no more garbage to be collected) or
-//       n == kMaxNumberOfGCs.
-// RUN n -> WAIT n (now_ms + short_delay_ms) happens:
-//     - at end of the incremental GC initiated by the MemoryReducer if
-//       (n == 1 or there is more garbage to be collected) and
-//       n < kMaxNumberOfGCs.
-//
-// now_ms is the current time, long_delay_ms and short_delay_ms are constants.
-class MemoryReducer {
- public:
-  enum Action { kDone, kWait, kRun };
-
-  struct State {
-    State(Action action, int started_gcs, double next_gc_start_ms)
-        : action(action),
-          started_gcs(started_gcs),
-          next_gc_start_ms(next_gc_start_ms) {}
-    Action action;
-    int started_gcs;
-    double next_gc_start_ms;
-  };
-
-  enum EventType {
-    kTimer,
-    kMarkCompact,
-    kContextDisposed,
-  };
-
-  struct Event {
-    EventType type;
-    double time_ms;
-    bool low_allocation_rate;
-    bool next_gc_likely_to_collect_more;
-    bool can_start_incremental_gc;
-  };
-
-  explicit MemoryReducer(Heap* heap) : heap_(heap), state_(kDone, 0, 0.0) {}
-  // Callbacks.
-  void NotifyTimer(const Event& event);
-  void NotifyMarkCompact(const Event& event);
-  void NotifyScavenge(const Event& event);
-  void NotifyContextDisposed(const Event& event);
-  // The step function that computes the next state from the current state and
-  // the incoming event.
-  static State Step(const State& state, const Event& event);
-  // Posts a timer task that will call NotifyTimer after the given delay.
-  void ScheduleTimer(double delay_ms);
-
-  static const int kLongDelayMs;
-  static const int kShortDelayMs;
-  static const int kMaxNumberOfGCs;
-
-  Heap* heap() { return heap_; }
-
- private:
-  class TimerTask : public v8::Task {
-   public:
-    explicit TimerTask(MemoryReducer* memory_reducer)
-        : memory_reducer_(memory_reducer) {}
-    virtual ~TimerTask() {}
-
-   private:
-    // v8::Task overrides.
-    void Run() override;
-    MemoryReducer* memory_reducer_;
-    DISALLOW_COPY_AND_ASSIGN(TimerTask);
-  };
-
-  Heap* heap_;
-  State state_;
-
-  DISALLOW_COPY_AND_ASSIGN(MemoryReducer);
-};
-
-}  // namespace internal
-}  // namespace v8
-
-#endif  // V8_HEAP_memory_reducer_H