Add MemoryCoordinatorImpl

content/browser/memory/memory_coordinator_impl.h

Index: content/browser/memory/memory_coordinator_impl.h
diff --git a/content/browser/memory/memory_coordinator_impl.h b/content/browser/memory/memory_coordinator_impl.h
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+++ b/content/browser/memory/memory_coordinator_impl.h
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+// Copyright 2016 The Chromium 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 CONTENT_BROWSER_MEMORY_MEMORY_COORDINATOR_IMPL_H_
+#define CONTENT_BROWSER_MEMORY_MEMORY_COORDINATOR_IMPL_H_
+
+#include "base/callback.h"
+#include "base/memory/singleton.h"
+#include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
+#include "base/threading/non_thread_safe.h"
+#include "base/time/time.h"
+#include "content/browser/memory/memory_coordinator.h"
+
+namespace content {
+
+class MemoryMonitor;
+class MemoryCoordinatorImplTest;
+struct MemoryCoordinatorSingletonTraits;
+
+// MemoryCoordinatorImpl is an internal implementation of MemoryCoordinator
+// which uses a heuristic to determine a single global memory state.
+// In the current implementation browser process and renderer processes share
+// the global state; the memory coordinator will notify the global state to
+// all background renderers if the state has changed.
+//
+// State calculation:
+// MemoryCoordinatorImpl uses followings to determine the global state:
+// * Compute "number of renderers which can be created until the system will
+//   be in a critical state". Call this N.
+//   (See memory_monitor.h for the definition of "critical")
+// * Covert N to a memory state using some thresholds/hysteresis for each state.
+//   Once a state is changed to a limited state, larger N will be needed to go
+//   back to a relaxed state. (e.g. THROTTLED -> NORMAL)
+// * Once a state is changed, it remains the same for a certain period of time.
+class CONTENT_EXPORT MemoryCoordinatorImpl : public MemoryCoordinator,
+                                             public base::NonThreadSafe {
+ public:
+  MemoryCoordinatorImpl(scoped_refptr<base::SingleThreadTaskRunner> task_runner,
+                        std::unique_ptr<MemoryMonitor> monitor);
+  ~MemoryCoordinatorImpl() override;
+
+  // MemoryCoordinator implementations:
+  void Start() override;
+  void OnChildAdded(int render_process_id) override;
+
+  MemoryMonitor* memory_monitor() { return memory_monitor_.get(); }
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(MemoryCoordinatorImplTest, CalculateNextState);
+  FRIEND_TEST_ALL_PREFIXES(MemoryCoordinatorImplTest, UpdateState);
+
+  friend struct MemoryCoordinatorSingletonTraits;
+
+  using MemoryState = base::MemoryState;
+
+  // Calculates the next global state from the amount of free memory using
+  // a heuristic.
+  MemoryState CalculateNextState();
+
+  // Updates the global state and notifies state changes to clients (lives in
+  // the browser) and child processes (renderers) if necessary.
+  void UpdateState();
+
+  // Notifies a state change to in-process clients.
+  void NotifyStateToClients();
+
+  // Notifies a state change to child processes.
+  void NotifyStateToChildren();
+
+  // Schedules a task to update the global state. The task will be executed
+  // after |delay| has passed.
+  void ScheduleUpdateState(base::TimeDelta delay);
+
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  std::unique_ptr<MemoryMonitor> memory_monitor_;
+  base::Closure update_state_callback_;
+  base::MemoryState current_state_ = MemoryState::NORMAL;
+  base::TimeTicks last_state_change_;
+
+  // Validates parameters defined below.
+  bool ValidateParameters();
+
+  // Parameters to control the heuristic.
+
+  // The median size of a renderer on the current platform. This is used to
+  // convert the amount of free memory to an expected number of new renderers
+  // that could be started before hitting critical memory pressure.
+  int expected_renderer_size_;
+  // When in a NORMAL state and the potential number of new renderers drops
+  // below this level, the coordinator will transition to a THROTTLED state.
+  int new_renderers_until_throttled_;
+  // When in a NORMAL/THROTTLED state and the potential number of new renderers
+  // drops below this level, the coordinator will transition to a SUSPENDED
+  // state.
+  int new_renderers_until_suspended_;
+  // When in a THROTTLED/SUSPENDED state and the potential number of new
+  // renderers rises above this level, the coordinator will transition to a
+  // NORMAL state.
+  int new_renderers_back_to_normal_;
+  // When in a SUSPENDED state and the potential number of new renderers rises
+  // above this level, the coordinator will transition to a SUSPENDED state.
+  int new_renderers_back_to_throttled_;
+  // The memory coordinator stays in the same state at least this duration even
+  // when there are considerable changes in the amount of free memory to prevent
+  // thrashing.
+  base::TimeDelta minimum_transition_period_;
+  // The interval of checking the amount of free memory.
+  base::TimeDelta monitoring_interval_;
+
+  base::WeakPtrFactory<MemoryCoordinatorImpl> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(MemoryCoordinatorImpl);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEMORY_MEMORY_COORDINATOR_IMPL_H_