michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim: set sw=2 ts=8 et ft=cpp : */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
michael@0:  * You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef mozilla_ProcessPriorityManager_h_
michael@0: #define mozilla_ProcessPriorityManager_h_
michael@0: 
michael@0: #include "mozilla/HalTypes.h"
michael@0: 
michael@0: namespace mozilla {
michael@0: namespace dom {
michael@0: class ContentParent;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * This class sets the priority of subprocesses in response to explicit
michael@0:  * requests and events in the system.
michael@0:  *
michael@0:  * A process's priority changes e.g. when it goes into the background via
michael@0:  * mozbrowser's setVisible(false).  Process priority affects CPU scheduling and
michael@0:  * also which processes get killed when we run out of memory.
michael@0:  *
michael@0:  * After you call Initialize(), the only thing you probably have to do is call
michael@0:  * SetProcessPriority on processes immediately after creating them in order to
michael@0:  * set their initial priority.  The ProcessPriorityManager takes care of the
michael@0:  * rest.
michael@0:  */
michael@0: class ProcessPriorityManager MOZ_FINAL
michael@0: {
michael@0: public:
michael@0:   /**
michael@0:    * Initialize the ProcessPriorityManager machinery, causing the
michael@0:    * ProcessPriorityManager to actively manage the priorities of all
michael@0:    * subprocesses.  You should call this before creating any subprocesses.
michael@0:    *
michael@0:    * You should also call this function even if you're in a child process,
michael@0:    * since it will initialize ProcessPriorityManagerChild.
michael@0:    */
michael@0:   static void Init();
michael@0: 
michael@0:   /**
michael@0:    * Set the process priority of a given ContentParent's process.
michael@0:    *
michael@0:    * Note that because this method takes a ContentParent*, you can only set the
michael@0:    * priority of your subprocesses.  In fact, because we don't support nested
michael@0:    * content processes (bug 761935), you can only call this method from the
michael@0:    * main process.
michael@0:    *
michael@0:    * It probably only makes sense to call this function immediately after a
michael@0:    * process is created.  At this point, the process priority manager doesn't
michael@0:    * have enough context about the processs to know what its priority should
michael@0:    * be.
michael@0:    *
michael@0:    * Eventually whatever priority you set here can and probably will be
michael@0:    * overwritten by the process priority manager.
michael@0:    */
michael@0:   static void SetProcessPriority(dom::ContentParent* aContentParent,
michael@0:                                  hal::ProcessPriority aPriority);
michael@0: 
michael@0:   /**
michael@0:    * Returns true iff this process's priority is FOREGROUND*.
michael@0:    *
michael@0:    * Note that because process priorities are set in the main process, it's
michael@0:    * possible for this method to return a stale value.  So be careful about
michael@0:    * what you use this for.
michael@0:    */
michael@0:   static bool CurrentProcessIsForeground();
michael@0: 
michael@0:   /**
michael@0:    * Returns true if one or more processes with FOREGROUND_HIGH priority are
michael@0:    * present, false otherwise.
michael@0:    */
michael@0:   static bool AnyProcessHasHighPriority();
michael@0: 
michael@0:   /**
michael@0:    * Used to remove a ContentParent from background LRU pool when
michael@0:    * it is destroyed or its priority changed from BACKGROUND to others.
michael@0:    */
michael@0:   static void RemoveFromBackgroundLRUPool(dom::ContentParent* aContentParent);
michael@0: 
michael@0:   /**
michael@0:    * Used to add a ContentParent into background LRU pool when
michael@0:    * its priority changed to BACKGROUND from others.
michael@0:    */
michael@0:   static void AddIntoBackgroundLRUPool(dom::ContentParent* aContentParent);
michael@0: 
michael@0: private:
michael@0:   ProcessPriorityManager();
michael@0:   DISALLOW_EVIL_CONSTRUCTORS(ProcessPriorityManager);
michael@0: };
michael@0: 
michael@0: } // namespace mozilla
michael@0: 
michael@0: #endif