зеркало из https://github.com/mozilla/gecko-dev.git
78 строки
3.2 KiB
C
78 строки
3.2 KiB
C
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef nsMemoryPressure_h__
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#define nsMemoryPressure_h__
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#include "nscore.h"
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/*
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* These pre-defined strings are the topic to pass to the observer
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* service to declare the memory-pressure or lift the memory-pressure.
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*
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* 1. Notify kTopicMemoryPressure with kSubTopicLowMemoryNew
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* New memory pressure deteced
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* On a new memory pressure, we stop everything to start cleaning
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* aggresively the memory used, in order to free as much memory as
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* possible.
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*
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* 2. Notify kTopicMemoryPressure with kSubTopicLowMemoryOngoing
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* Repeated memory pressure.
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* A repeated memory pressure implies to clean softly recent allocations.
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* It is supposed to happen after a new memory pressure which already
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* cleaned aggressivley. So there is no need to damage the reactivity of
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* Gecko by stopping the world again.
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*
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* In case of conflict with an new memory pressue, the new memory pressure
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* takes precedence over an ongoing memory pressure. The reason being
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* that if no events are processed between 2 notifications (new followed
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* by ongoing, or ongoing followed by a new) we want to be as aggresive as
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* possible on the clean-up of the memory. After all, we are trying to
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* keep Gecko alive as long as possible.
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*
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* 3. Notify kTopicMemoryPressureStop with nullptr
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* Memory pressure stopped.
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* We're no longer under acute memory pressure, so we might want to have a
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* chance of (cautiously) re-enabling some things we previously turned off.
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* As above, an already enqueued new memory pressure event takes precedence.
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* The priority ordering between concurrent attempts to queue both stopped
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* and ongoing memory pressure is currently not defined.
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*/
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extern const char* const kTopicMemoryPressure;
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extern const char* const kTopicMemoryPressureStop;
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extern const char16_t* const kSubTopicLowMemoryNew;
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extern const char16_t* const kSubTopicLowMemoryOngoing;
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enum class MemoryPressureState : uint32_t {
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None, // For internal use. Don't use this value.
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LowMemory,
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NoPressure,
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};
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/**
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* This function causes the main thread to fire a memory pressure event
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* before processing the next event, but if there are no events pending in
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* the main thread's event queue, the memory pressure event would not be
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* dispatched until one is enqueued. It is infallible and does not allocate
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* any memory.
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*
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* You may call this function from any thread.
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*/
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void NS_NotifyOfEventualMemoryPressure(MemoryPressureState aState);
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/**
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* This function causes the main thread to fire a memory pressure event
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* before processing the next event. We wake up the main thread by adding a
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* dummy event to its event loop, so, unlike with
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* NS_NotifyOfEventualMemoryPressure, this memory-pressure event is always
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* fired relatively quickly, even if the event loop is otherwise empty.
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*
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* You may call this function from any thread.
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*/
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nsresult NS_NotifyOfMemoryPressure(MemoryPressureState aState);
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#endif // nsMemoryPressure_h__
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