1 files changed, 78 insertions, 0 deletions
diff --git a/xpcom/base/AvailableMemoryWatcher.h b/xpcom/base/AvailableMemoryWatcher.h
new file mode 100644
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+++ b/xpcom/base/AvailableMemoryWatcher.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_AvailableMemoryWatcher_h
+#define mozilla_AvailableMemoryWatcher_h
+
+#include "mozilla/ipc/CrashReporterHost.h"
+#include "mozilla/UniquePtr.h"
+#include "MemoryPressureLevelMac.h"
+#include "nsCOMPtr.h"
+#include "nsIAvailableMemoryWatcherBase.h"
+#include "nsIObserver.h"
+#include "nsIObserverService.h"
+
+namespace mozilla {
+
+// This class implements a platform-independent part to watch the system's
+// memory situation and invoke the registered callbacks when we detect
+// a low-memory situation or a high-memory situation.
+// The actual logic to monitor the memory status is implemented in a subclass
+// of nsAvailableMemoryWatcherBase per platform.
+class nsAvailableMemoryWatcherBase : public nsIAvailableMemoryWatcherBase,
+                                     public nsIObserver {
+  static StaticRefPtr<nsAvailableMemoryWatcherBase> sSingleton;
+  static const char* const kObserverTopics[];
+
+  TimeStamp mLowMemoryStart;
+
+ protected:
+  // On Windows the publicly available methods (::Observe() and ::Notify()) are
+  // called on the main thread while the ::LowMemoryCallback() method is called
+  // by an external thread. All functions called from those must acquire a lock
+  // on this mutex before accessing the object's fields to prevent races.
+  //
+  // On Linux we might tell polling to start/stop from our polling thread
+  // or from the main thread during ::Observe().
+  Mutex mMutex;
+
+  uint32_t mNumOfTabUnloading MOZ_GUARDED_BY(mMutex);
+  uint32_t mNumOfMemoryPressure MOZ_GUARDED_BY(mMutex);
+
+  nsCOMPtr<nsITabUnloader> mTabUnloader;
+  nsCOMPtr<nsIObserverService> mObserverSvc;
+  // Do not change this value off the main thread.
+  bool mInteracting;
+
+  virtual ~nsAvailableMemoryWatcherBase() = default;
+  virtual nsresult Init();
+  void Shutdown();
+  void UpdateLowMemoryTimeStamp();
+  void RecordTelemetryEventOnHighMemory(const MutexAutoLock&)
+      MOZ_REQUIRES(mMutex);
+
+ public:
+  static already_AddRefed<nsAvailableMemoryWatcherBase> GetSingleton();
+
+  nsAvailableMemoryWatcherBase();
+
+#if defined(XP_DARWIN)
+  virtual void OnMemoryPressureChanged(MacMemoryPressureLevel aNewLevel){};
+  virtual void AddChildAnnotations(
+      const UniquePtr<ipc::CrashReporterHost>& aCrashReporter){};
+#endif
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIAVAILABLEMEMORYWATCHERBASE
+  NS_DECL_NSIOBSERVER
+};
+
+// Method to create a platform-specific object
+already_AddRefed<nsAvailableMemoryWatcherBase> CreateAvailableMemoryWatcher();
+
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_AvailableMemoryWatcher_h