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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
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