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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_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