import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

dom/ipc/ProcessPriorityManager.h

@@ -0,0 +1,84 @@
+/* -*- 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_ProcessPriorityManager_h_
+#define mozilla_ProcessPriorityManager_h_
+
+#include "mozilla/HalTypes.h"
+
+namespace mozilla {
+namespace dom {
+class ContentParent;
+} // namespace dom
+
+/**
+ * This class sets the priority of subprocesses in response to explicit
+ * requests and events in the system.
+ *
+ * A process's priority changes e.g. when it goes into the background via
+ * mozbrowser's setVisible(false).  Process priority affects CPU scheduling and
+ * also which processes get killed when we run out of memory.
+ *
+ * After you call Initialize(), the only thing you probably have to do is call
+ * SetProcessPriority on processes immediately after creating them in order to
+ * set their initial priority.  The ProcessPriorityManager takes care of the
+ * rest.
+ */
+class ProcessPriorityManager final
+{
+public:
+  /**
+   * Initialize the ProcessPriorityManager machinery, causing the
+   * ProcessPriorityManager to actively manage the priorities of all
+   * subprocesses.  You should call this before creating any subprocesses.
+   *
+   * You should also call this function even if you're in a child process,
+   * since it will initialize ProcessPriorityManagerChild.
+   */
+  static void Init();
+
+  /**
+   * Set the process priority of a given ContentParent's process.
+   *
+   * Note that because this method takes a ContentParent*, you can only set the
+   * priority of your subprocesses.  In fact, because we don't support nested
+   * content processes (bug 761935), you can only call this method from the
+   * main process.
+   *
+   * It probably only makes sense to call this function immediately after a
+   * process is created.  At this point, the process priority manager doesn't
+   * have enough context about the processs to know what its priority should
+   * be.
+   *
+   * Eventually whatever priority you set here can and probably will be
+   * overwritten by the process priority manager.
+   */
+  static void SetProcessPriority(dom::ContentParent* aContentParent,
+                                 hal::ProcessPriority aPriority);
+
+  /**
+   * Returns true iff this process's priority is FOREGROUND*.
+   *
+   * Note that because process priorities are set in the main process, it's
+   * possible for this method to return a stale value.  So be careful about
+   * what you use this for.
+   */
+  static bool CurrentProcessIsForeground();
+
+  /**
+   * Returns true if one or more processes with FOREGROUND_HIGH priority are
+   * present, false otherwise.
+   */
+  static bool AnyProcessHasHighPriority();
+
+private:
+  ProcessPriorityManager();
+  DISALLOW_EVIL_CONSTRUCTORS(ProcessPriorityManager);
+};
+
+} // namespace mozilla
+
+#endif