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-rw-r--r--xpcom/threads/nsMemoryPressure.cpp104
1 files changed, 104 insertions, 0 deletions
diff --git a/xpcom/threads/nsMemoryPressure.cpp b/xpcom/threads/nsMemoryPressure.cpp
new file mode 100644
index 0000000000..dbd3a92f79
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+++ b/xpcom/threads/nsMemoryPressure.cpp
@@ -0,0 +1,104 @@
+/* -*- 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
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#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;
+ }
+}