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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
#include "nsMemoryPressure.h"
#include "mozilla/Assertions.h"
#include "mozilla/Atomics.h"
#include "mozilla/Services.h"
#include "nsThreadUtils.h"
#include "nsIObserverService.h"
using namespace mozilla;
const char* const kTopicMemoryPressure = "memory-pressure";
const char* const kTopicMemoryPressureStop = "memory-pressure-stop";
const char16_t* const kSubTopicLowMemoryNew = u"low-memory";
const char16_t* const kSubTopicLowMemoryOngoing = u"low-memory-ongoing";
// This is accessed from any thread through NS_NotifyOfEventualMemoryPressure
static Atomic<MemoryPressureState, Relaxed> sMemoryPressurePending(
MemoryPressureState::NoPressure);
void NS_NotifyOfEventualMemoryPressure(MemoryPressureState aState) {
MOZ_ASSERT(aState != MemoryPressureState::None);
/*
* A new memory pressure event erases an ongoing (or stop of) memory pressure,
* but an existing "new" memory pressure event takes precedence over a new
* "ongoing" or "stop" memory pressure event.
*/
switch (aState) {
case MemoryPressureState::None:
case MemoryPressureState::LowMemory:
sMemoryPressurePending = aState;
break;
case MemoryPressureState::NoPressure:
sMemoryPressurePending.compareExchange(MemoryPressureState::None, aState);
break;
}
}
nsresult NS_NotifyOfMemoryPressure(MemoryPressureState aState) {
NS_NotifyOfEventualMemoryPressure(aState);
nsCOMPtr<nsIRunnable> event =
new Runnable("NS_DispatchEventualMemoryPressure");
return NS_DispatchToMainThread(event);
}
void NS_DispatchMemoryPressure() {
MOZ_ASSERT(NS_IsMainThread());
static MemoryPressureState sMemoryPressureStatus =
MemoryPressureState::NoPressure;
MemoryPressureState mpPending =
sMemoryPressurePending.exchange(MemoryPressureState::None);
if (mpPending == MemoryPressureState::None) {
return;
}
nsCOMPtr<nsIObserverService> os = services::GetObserverService();
if (!os) {
NS_WARNING("Can't get observer service!");
return;
}
switch (mpPending) {
case MemoryPressureState::None:
MOZ_ASSERT_UNREACHABLE("Already handled this case above.");
break;
case MemoryPressureState::LowMemory:
switch (sMemoryPressureStatus) {
case MemoryPressureState::None:
MOZ_ASSERT_UNREACHABLE("The internal status should never be None.");
break;
case MemoryPressureState::NoPressure:
sMemoryPressureStatus = MemoryPressureState::LowMemory;
os->NotifyObservers(nullptr, kTopicMemoryPressure,
kSubTopicLowMemoryNew);
break;
case MemoryPressureState::LowMemory:
os->NotifyObservers(nullptr, kTopicMemoryPressure,
kSubTopicLowMemoryOngoing);
break;
}
break;
case MemoryPressureState::NoPressure:
switch (sMemoryPressureStatus) {
case MemoryPressureState::None:
MOZ_ASSERT_UNREACHABLE("The internal status should never be None.");
break;
case MemoryPressureState::NoPressure:
// Already no pressure. Do nothing.
break;
case MemoryPressureState::LowMemory:
sMemoryPressureStatus = MemoryPressureState::NoPressure;
os->NotifyObservers(nullptr, kTopicMemoryPressureStop, nullptr);
break;
}
break;
}
}