Adding Baseframework of the ResourceManager (all hooks and observers) are being put in place with a…

athena/resource_manager/memory_pressure_notifier.cc

+// Copyright (c) 2014 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.
+
+#include "athena/resource_manager/memory_pressure_notifier.h"
+
+#include "athena/resource_manager/public/resource_manager_delegate.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
+#include "base/timer/timer.h"
+
+
+namespace athena {
+
+////////////////////////////////////////////////////////////////////////////////
+// MemoryPressureNotifierImpl
+//
+// Does the actual work of observing. Ideally we would need to have at least one
+// event driven margin window which can monitor the memory size. However, this
+// functionality does not yet exist and for the time being we poll instead the
+// available memory amount. Note that on the bright side this will also work on
+// a non ChromeOS kernel.
+// Note: Any calls to the resource manager will take some time to show effect.
+class MemoryPressureNotifierImpl

[Jun Mukai, 2014/08/27 01:21:18]

You don't have to introduce pimpl pattern to this file.
We separate Impl and public/ only when the file is exported to other athena
modules.

[Mr4D (OOO till 08-26), 2014/08/27 16:12:12]

Done.  (Did that because of the thread safe release - which isn't required
anymore since my inital IPC code implementation did go away).

+    : public base::RefCountedThreadSafe<MemoryPressureNotifierImpl> {
+ public:
+  explicit MemoryPressureNotifierImpl(MemoryPressureObserver* listener)
+      : listener_(listener),
+        current_pressure_(MemoryPressureObserver::MEMORY_PRESSURE_UNKNOWN) {
+    StartObserving();
+  }
+
+ private:
+  friend class base::RefCountedThreadSafe<MemoryPressureNotifierImpl>;
+
+  virtual ~MemoryPressureNotifierImpl() {
+    StopObserving();
+  }
+
+  // Starts observing the memory fill level.
+  // Calls to StartObserving should always be matched with calls to
+  // StopObserving.
+  void StartObserving();
+
+  // Stop observing the memory fill level.
+  // May be safely called if StartObserving has not been called.
+  void StopObserving();
+
+  // The function which gets periodically be called to check any changes in the
+  // memory pressure.
+  void CheckMemoryPressure();
+
+  // Converts free percent of memory into a memory pressure value.
+  MemoryPressureObserver::MemoryPressure GetMemoryPressureLevelFromFillLevel(
+      int memory_fill_level);
+
+  base::RepeatingTimer<MemoryPressureNotifierImpl> timer_;
+
+  // The listener which needs to be informed about memory pressure.
+  MemoryPressureObserver* listener_;
+
+  // Our current memory pressure.
+  MemoryPressureObserver::MemoryPressure current_pressure_;
+
+  DISALLOW_COPY_AND_ASSIGN(MemoryPressureNotifierImpl);
+};
+
+void MemoryPressureNotifierImpl::StartObserving() {
+  int time_in_ms = listener_->GetDelegate()->MemoryPressureIntervalInMS();
+  timer_.Start(FROM_HERE,
+               base::TimeDelta::FromMilliseconds(time_in_ms),
+               base::Bind(&MemoryPressureNotifierImpl::CheckMemoryPressure,
+                          base::Unretained(this)));
+}
+
+void MemoryPressureNotifierImpl::StopObserving() {
+  // If StartObserving failed, StopObserving will still get called.
+  timer_.Stop();
+}
+
+void MemoryPressureNotifierImpl::CheckMemoryPressure() {
+  MemoryPressureObserver::MemoryPressure pressure =
+      GetMemoryPressureLevelFromFillLevel(
+          listener_->GetDelegate()->GetUsedMemoryInPercent());
+  if (current_pressure_ != pressure ||
+      (pressure != MemoryPressureObserver::MEMORY_PRESSURE_LOW &&
+       pressure != MemoryPressureObserver::MEMORY_PRESSURE_UNKNOWN)) {
+    // If we are anything worse than |MEMORY_PRESSURE_LOW|, we notify the
+    // listener.
+    current_pressure_ = pressure;
+    listener_->OnMemoryPressure(current_pressure_);
+  }
+}
+
+MemoryPressureObserver::MemoryPressure
+MemoryPressureNotifierImpl::GetMemoryPressureLevelFromFillLevel(
+    int memory_fill_level) {
+  if (memory_fill_level == 0)
+    return MemoryPressureObserver::MEMORY_PRESSURE_UNKNOWN;
+  if (memory_fill_level < 50)
+    return MemoryPressureObserver::MEMORY_PRESSURE_LOW;
+  if (memory_fill_level < 75)
+    return MemoryPressureObserver::MEMORY_PRESSURE_MODERATE;
+  if (memory_fill_level < 90)
+    return MemoryPressureObserver::MEMORY_PRESSURE_HIGH;
+  return MemoryPressureObserver::MEMORY_PRESSURE_CRITICAL;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// MemoryPressureNotifier
+
+MemoryPressureNotifier::MemoryPressureNotifier(MemoryPressureObserver* listener)
+    : observer_(new MemoryPressureNotifierImpl(listener)) {
+}
+
+MemoryPressureNotifier::~MemoryPressureNotifier() {}
+
+}  // namespace athena