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For Fennec on Android, if we haven't received memory pressure notifications from the OS for a certain amount of time (in the order of ~15 mins), we assume that we're no longer under memory pressure. In order to turn the bfcache back on when that happens, we now want to be able to forward this fact to Gecko as well. Unfortunately, the way memory pressure is tracked using an atomic variable doesn't easily allow to fully extend the existing priority rules between "new" and "ongoing" to include a new "stopping of memory pressure" event. Since we're not using Dispatch*Eventual*MemoryPressure on Android and therefore the queuing priority behaviour isn't actually relevant for us, we just ignore that and only enforce that a pending "new" memory pressure event takes priority over a "stop" event. MozReview-Commit-ID: 90C9KogUyvf --HG-- extra : rebase_source : 4e71a31433557d8d486f941953717a88d5d87e7d
89 lines
3.0 KiB
C
89 lines
3.0 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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enum MemoryPressureState
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{
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/*
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* No memory pressure.
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*/
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MemPressure_None = 0,
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/*
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* New memory pressure deteced.
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*
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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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MemPressure_New,
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/*
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* Repeated memory pressure.
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*
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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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MemPressure_Ongoing,
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/*
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* Memory pressure stopped.
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*
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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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MemPressure_Stopping
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};
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/**
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* Return and erase the latest state of the memory pressure event set by any of
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* the corresponding dispatch function.
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*/
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MemoryPressureState
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NS_GetPendingMemoryPressure();
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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
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NS_DispatchEventualMemoryPressure(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_DispatchEventualMemoryPressure, 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
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NS_DispatchMemoryPressure(MemoryPressureState aState);
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#endif // nsMemoryPressure_h__
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