michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim:set ts=2 sw=2 sts=2 et cindent: */
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
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef nsMemoryPressure_h__
michael@0: #define nsMemoryPressure_h__
michael@0: 
michael@0: #include "nscore.h"
michael@0: 
michael@0: enum MemoryPressureState {
michael@0:   /*
michael@0:    * No memory pressure.
michael@0:    */
michael@0:   MemPressure_None = 0,
michael@0: 
michael@0:   /*
michael@0:    * New memory pressure deteced.
michael@0:    *
michael@0:    * On a new memory pressure, we stop everything to start cleaning
michael@0:    * aggresively the memory used, in order to free as much memory as
michael@0:    * possible.
michael@0:    */
michael@0:   MemPressure_New,
michael@0: 
michael@0:   /*
michael@0:    * Repeated memory pressure.
michael@0:    *
michael@0:    * A repeated memory pressure implies to clean softly recent allocations.
michael@0:    * It is supposed to happen after a new memory pressure which already
michael@0:    * cleaned aggressivley.  So there is no need to damage the reactivity of
michael@0:    * Gecko by stopping the world again.
michael@0:    *
michael@0:    * In case of conflict with an new memory pressue, the new memory pressure
michael@0:    * takes precedence over an ongoing memory pressure.  The reason being
michael@0:    * that if no events are processed between 2 notifications (new followed
michael@0:    * by ongoing, or ongoing followed by a new) we want to be as aggresive as
michael@0:    * possible on the clean-up of the memory.  After all, we are trying to
michael@0:    * keep Gecko alive as long as possible.
michael@0:    */
michael@0:   MemPressure_Ongoing
michael@0: };
michael@0: 
michael@0: /**
michael@0:  * Return and erase the latest state of the memory pressure event set by any of
michael@0:  * the corresponding dispatch function.
michael@0:  */
michael@0: MemoryPressureState
michael@0: NS_GetPendingMemoryPressure();
michael@0: 
michael@0: /**
michael@0:  * This function causes the main thread to fire a memory pressure event
michael@0:  * before processing the next event, but if there are no events pending in
michael@0:  * the main thread's event queue, the memory pressure event would not be
michael@0:  * dispatched until one is enqueued. It is infallible and does not allocate
michael@0:  * any memory.
michael@0:  *
michael@0:  * You may call this function from any thread.
michael@0:  */
michael@0: void
michael@0: NS_DispatchEventualMemoryPressure(MemoryPressureState state);
michael@0: 
michael@0: /**
michael@0:  * This function causes the main thread to fire a memory pressure event
michael@0:  * before processing the next event. We wake up the main thread by adding a
michael@0:  * dummy event to its event loop, so, unlike with
michael@0:  * NS_DispatchEventualMemoryPressure, this memory-pressure event is always
michael@0:  * fired relatively quickly, even if the event loop is otherwise empty.
michael@0:  *
michael@0:  * You may call this function from any thread.
michael@0:  */
michael@0: nsresult
michael@0: NS_DispatchMemoryPressure(MemoryPressureState state);
michael@0: 
michael@0: #endif // nsMemoryPressure_h__