1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/xpcom/threads/nsMemoryPressure.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,76 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim:set ts=2 sw=2 sts=2 et cindent: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +#ifndef nsMemoryPressure_h__
1.11 +#define nsMemoryPressure_h__
1.12 +
1.13 +#include "nscore.h"
1.14 +
1.15 +enum MemoryPressureState {
1.16 + /*
1.17 + * No memory pressure.
1.18 + */
1.19 + MemPressure_None = 0,
1.20 +
1.21 + /*
1.22 + * New memory pressure deteced.
1.23 + *
1.24 + * On a new memory pressure, we stop everything to start cleaning
1.25 + * aggresively the memory used, in order to free as much memory as
1.26 + * possible.
1.27 + */
1.28 + MemPressure_New,
1.29 +
1.30 + /*
1.31 + * Repeated memory pressure.
1.32 + *
1.33 + * A repeated memory pressure implies to clean softly recent allocations.
1.34 + * It is supposed to happen after a new memory pressure which already
1.35 + * cleaned aggressivley. So there is no need to damage the reactivity of
1.36 + * Gecko by stopping the world again.
1.37 + *
1.38 + * In case of conflict with an new memory pressue, the new memory pressure
1.39 + * takes precedence over an ongoing memory pressure. The reason being
1.40 + * that if no events are processed between 2 notifications (new followed
1.41 + * by ongoing, or ongoing followed by a new) we want to be as aggresive as
1.42 + * possible on the clean-up of the memory. After all, we are trying to
1.43 + * keep Gecko alive as long as possible.
1.44 + */
1.45 + MemPressure_Ongoing
1.46 +};
1.47 +
1.48 +/**
1.49 + * Return and erase the latest state of the memory pressure event set by any of
1.50 + * the corresponding dispatch function.
1.51 + */
1.52 +MemoryPressureState
1.53 +NS_GetPendingMemoryPressure();
1.54 +
1.55 +/**
1.56 + * This function causes the main thread to fire a memory pressure event
1.57 + * before processing the next event, but if there are no events pending in
1.58 + * the main thread's event queue, the memory pressure event would not be
1.59 + * dispatched until one is enqueued. It is infallible and does not allocate
1.60 + * any memory.
1.61 + *
1.62 + * You may call this function from any thread.
1.63 + */
1.64 +void
1.65 +NS_DispatchEventualMemoryPressure(MemoryPressureState state);
1.66 +
1.67 +/**
1.68 + * This function causes the main thread to fire a memory pressure event
1.69 + * before processing the next event. We wake up the main thread by adding a
1.70 + * dummy event to its event loop, so, unlike with
1.71 + * NS_DispatchEventualMemoryPressure, this memory-pressure event is always
1.72 + * fired relatively quickly, even if the event loop is otherwise empty.
1.73 + *
1.74 + * You may call this function from any thread.
1.75 + */
1.76 +nsresult
1.77 +NS_DispatchMemoryPressure(MemoryPressureState state);
1.78 +
1.79 +#endif // nsMemoryPressure_h__
