dom/ipc/ProcessPriorityManager.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_ProcessPriorityManager_h_
   8 #define mozilla_ProcessPriorityManager_h_
   9
  10 #include "mozilla/HalTypes.h"
  11
  12 class nsFrameLoader;
  13
  14 namespace mozilla {
  15 namespace dom {
  16 class BrowserParent;
  17 class CanonicalBrowsingContext;
  18 class ContentParent;
  19 }  // namespace dom
  20
  21 /**
  22  * This class sets the priority of subprocesses in response to explicit
  23  * requests and events in the system.
  24  *
  25  * A process's priority changes e.g. when it goes into the background via
  26  * mozbrowser's setVisible(false).  Process priority affects CPU scheduling and
  27  * also which processes get killed when we run out of memory.
  28  *
  29  * After you call Initialize(), the only thing you probably have to do is call
  30  * SetProcessPriority on processes immediately after creating them in order to
  31  * set their initial priority.  The ProcessPriorityManager takes care of the
  32  * rest.
  33  */
  34 class ProcessPriorityManager final {
  35  public:
  36   /**
  37    * Initialize the ProcessPriorityManager machinery, causing the
  38    * ProcessPriorityManager to actively manage the priorities of all
  39    * subprocesses.  You should call this before creating any subprocesses.
  40    *
  41    * You should also call this function even if you're in a child process,
  42    * since it will initialize ProcessPriorityManagerChild.
  43    */
  44   static void Init();
  45
  46   /**
  47    * Set the process priority of a given ContentParent's process.
  48    *
  49    * Note that because this method takes a ContentParent*, you can only set the
  50    * priority of your subprocesses.  In fact, because we don't support nested
  51    * content processes (bug 761935), you can only call this method from the
  52    * main process.
  53    *
  54    * It probably only makes sense to call this function immediately after a
  55    * process is created.  At this point, the process priority manager doesn't
  56    * have enough context about the processs to know what its priority should
  57    * be.
  58    *
  59    * Eventually whatever priority you set here can and probably will be
  60    * overwritten by the process priority manager.
  61    */
  62   static void SetProcessPriority(dom::ContentParent* aContentParent,
  63                                  hal::ProcessPriority aPriority);
  64
  65   /**
  66    * Returns true iff this process's priority is FOREGROUND*.
  67    *
  68    * Note that because process priorities are set in the main process, it's
  69    * possible for this method to return a stale value.  So be careful about
  70    * what you use this for.
  71    */
  72   static bool CurrentProcessIsForeground();
  73
  74   /**
  75    * Updates the contents of mHighPriorityBrowserParents to keep track of
  76    * the list of TabIds for this process that are high priority.
  77    */
  78   static void BrowserPriorityChanged(dom::CanonicalBrowsingContext* aBC,
  79                                      bool aPriority);
  80   static void BrowserPriorityChanged(dom::BrowserParent* aBrowserParent,
  81                                      bool aPriority);
  82
  83   static void RemoteBrowserFrameShown(nsFrameLoader* aFrameLoader);
  84
  85  private:
  86   ProcessPriorityManager();
  87   ProcessPriorityManager(const ProcessPriorityManager&) = delete;
  88
  89   const ProcessPriorityManager& operator=(const ProcessPriorityManager&) =
  90       delete;
  91 };
  92
  93 }  // namespace mozilla
  94
  95 #endif