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-rw-r--r--xpcom/base/AvailableMemoryWatcherLinux.cpp290
1 files changed, 290 insertions, 0 deletions
diff --git a/xpcom/base/AvailableMemoryWatcherLinux.cpp b/xpcom/base/AvailableMemoryWatcherLinux.cpp
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+++ b/xpcom/base/AvailableMemoryWatcherLinux.cpp
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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
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "AvailableMemoryWatcher.h"
+#include "AvailableMemoryWatcherUtils.h"
+#include "mozilla/Services.h"
+#include "mozilla/StaticPrefs_browser.h"
+#include "mozilla/Unused.h"
+#include "nsAppRunner.h"
+#include "nsIObserverService.h"
+#include "nsISupports.h"
+#include "nsITimer.h"
+#include "nsIThread.h"
+#include "nsMemoryPressure.h"
+
+namespace mozilla {
+
+// Linux has no native low memory detection. This class creates a timer that
+// polls for low memory and sends a low memory notification if it notices a
+// memory pressure event.
+class nsAvailableMemoryWatcher final : public nsITimerCallback,
+ public nsINamed,
+ public nsAvailableMemoryWatcherBase {
+ public:
+ NS_DECL_ISUPPORTS_INHERITED
+ NS_DECL_NSITIMERCALLBACK
+ NS_DECL_NSIOBSERVER
+ NS_DECL_NSINAMED
+
+ nsresult Init() override;
+ nsAvailableMemoryWatcher();
+
+ void HandleLowMemory();
+ void MaybeHandleHighMemory();
+
+ private:
+ ~nsAvailableMemoryWatcher() = default;
+ void StartPolling(const MutexAutoLock&);
+ void StopPolling(const MutexAutoLock&);
+ void ShutDown();
+ void UpdateCrashAnnotation(const MutexAutoLock&);
+ static bool IsMemoryLow();
+
+ nsCOMPtr<nsITimer> mTimer MOZ_GUARDED_BY(mMutex);
+ nsCOMPtr<nsIThread> mThread MOZ_GUARDED_BY(mMutex);
+
+ bool mPolling MOZ_GUARDED_BY(mMutex);
+ bool mUnderMemoryPressure MOZ_GUARDED_BY(mMutex);
+
+ // We might tell polling to start/stop from our polling thread
+ // or from the main thread during ::Observe().
+ Mutex mMutex;
+
+ // Polling interval to check for low memory. In high memory scenarios,
+ // default to 5000 ms between each check.
+ static const uint32_t kHighMemoryPollingIntervalMS = 5000;
+
+ // Polling interval to check for low memory. Default to 1000 ms between each
+ // check. Use this interval when memory is low,
+ static const uint32_t kLowMemoryPollingIntervalMS = 1000;
+};
+
+// A modern version of linux should keep memory information in the
+// /proc/meminfo path.
+static const char* kMeminfoPath = "/proc/meminfo";
+
+nsAvailableMemoryWatcher::nsAvailableMemoryWatcher()
+ : mPolling(false),
+ mUnderMemoryPressure(false),
+ mMutex("Memory Poller mutex") {}
+
+nsresult nsAvailableMemoryWatcher::Init() {
+ nsresult rv = nsAvailableMemoryWatcherBase::Init();
+ if (NS_FAILED(rv)) {
+ return rv;
+ }
+ MutexAutoLock lock(mMutex);
+ mTimer = NS_NewTimer();
+ nsCOMPtr<nsIThread> thread;
+ // We have to make our own thread here instead of using the background pool,
+ // because some low memory scenarios can cause the background pool to fill.
+ rv = NS_NewNamedThread("MemoryPoller", getter_AddRefs(thread));
+ if (NS_FAILED(rv)) {
+ NS_WARNING("Couldn't make a thread for nsAvailableMemoryWatcher.");
+ // In this scenario we can't poll for low memory, since we can't dispatch
+ // to our memory watcher thread.
+ return rv;
+ }
+ mThread = thread;
+
+ // Set the crash annotation to its initial state.
+ UpdateCrashAnnotation(lock);
+
+ StartPolling(lock);
+
+ return NS_OK;
+}
+
+already_AddRefed<nsAvailableMemoryWatcherBase> CreateAvailableMemoryWatcher() {
+ RefPtr watcher(new nsAvailableMemoryWatcher);
+
+ if (NS_FAILED(watcher->Init())) {
+ return do_AddRef(new nsAvailableMemoryWatcherBase);
+ }
+
+ return watcher.forget();
+}
+
+NS_IMPL_ISUPPORTS_INHERITED(nsAvailableMemoryWatcher,
+ nsAvailableMemoryWatcherBase, nsITimerCallback,
+ nsIObserver, nsINamed);
+
+void nsAvailableMemoryWatcher::StopPolling(const MutexAutoLock&)
+ MOZ_REQUIRES(mMutex) {
+ if (mPolling && mTimer) {
+ // stop dispatching memory checks to the thread.
+ mTimer->Cancel();
+ mPolling = false;
+ }
+}
+
+// Check /proc/meminfo for low memory. Largely C method for reading
+// /proc/meminfo.
+/* static */
+bool nsAvailableMemoryWatcher::IsMemoryLow() {
+ MemoryInfo memInfo{0, 0};
+ bool aResult = false;
+
+ nsresult rv = ReadMemoryFile(kMeminfoPath, memInfo);
+
+ if (NS_FAILED(rv) || memInfo.memAvailable == 0) {
+ // If memAvailable cannot be found, then we are using an older system.
+ // We can't accurately poll on this.
+ return aResult;
+ }
+ unsigned long memoryAsPercentage =
+ (memInfo.memAvailable * 100) / memInfo.memTotal;
+
+ if (memoryAsPercentage <=
+ StaticPrefs::browser_low_commit_space_threshold_percent() ||
+ memInfo.memAvailable <
+ StaticPrefs::browser_low_commit_space_threshold_mb() * 1024) {
+ aResult = true;
+ }
+
+ return aResult;
+}
+
+void nsAvailableMemoryWatcher::ShutDown() {
+ nsCOMPtr<nsIThread> thread;
+ {
+ MutexAutoLock lock(mMutex);
+ if (mTimer) {
+ mTimer->Cancel();
+ mTimer = nullptr;
+ }
+ thread = mThread.forget();
+ }
+ // thread->Shutdown() spins a nested event loop while waiting for the thread
+ // to end. But the thread might execute some previously dispatched event that
+ // wants to lock our mutex, too, before arriving at the shutdown event.
+ if (thread) {
+ thread->Shutdown();
+ }
+}
+
+// We will use this to poll for low memory.
+NS_IMETHODIMP
+nsAvailableMemoryWatcher::Notify(nsITimer* aTimer) {
+ MutexAutoLock lock(mMutex);
+ if (!mThread) {
+ // If we've made it this far and there's no |mThread|,
+ // we might have failed to dispatch it for some reason.
+ MOZ_ASSERT(mThread);
+ return NS_ERROR_FAILURE;
+ }
+ nsresult rv = mThread->Dispatch(
+ NS_NewRunnableFunction("MemoryPoller", [self = RefPtr{this}]() {
+ if (self->IsMemoryLow()) {
+ self->HandleLowMemory();
+ } else {
+ self->MaybeHandleHighMemory();
+ }
+ }));
+
+ if NS_FAILED (rv) {
+ NS_WARNING("Cannot dispatch memory polling event.");
+ }
+ return NS_OK;
+}
+
+void nsAvailableMemoryWatcher::HandleLowMemory() {
+ MutexAutoLock lock(mMutex);
+ if (!mTimer) {
+ // We have been shut down from outside while in flight.
+ return;
+ }
+ if (!mUnderMemoryPressure) {
+ mUnderMemoryPressure = true;
+ UpdateCrashAnnotation(lock);
+ // Poll more frequently under memory pressure.
+ StartPolling(lock);
+ }
+ UpdateLowMemoryTimeStamp();
+ // We handle low memory offthread, but we want to unload
+ // tabs only from the main thread, so we will dispatch this
+ // back to the main thread.
+ NS_DispatchToMainThread(NS_NewRunnableFunction(
+ "nsAvailableMemoryWatcher::OnLowMemory",
+ [self = RefPtr{this}]() { self->mTabUnloader->UnloadTabAsync(); }));
+}
+
+void nsAvailableMemoryWatcher::UpdateCrashAnnotation(const MutexAutoLock&)
+ MOZ_REQUIRES(mMutex) {
+ CrashReporter::AnnotateCrashReport(
+ CrashReporter::Annotation::LinuxUnderMemoryPressure,
+ mUnderMemoryPressure);
+}
+
+// If memory is not low, we may need to dispatch an
+// event for it if we have been under memory pressure.
+// We can also adjust our polling interval.
+void nsAvailableMemoryWatcher::MaybeHandleHighMemory() {
+ MutexAutoLock lock(mMutex);
+ if (!mTimer) {
+ // We have been shut down from outside while in flight.
+ return;
+ }
+ if (mUnderMemoryPressure) {
+ RecordTelemetryEventOnHighMemory();
+ NS_NotifyOfEventualMemoryPressure(MemoryPressureState::NoPressure);
+ mUnderMemoryPressure = false;
+ UpdateCrashAnnotation(lock);
+ }
+ StartPolling(lock);
+}
+
+// When we change the polling interval, we will need to restart the timer
+// on the new interval.
+void nsAvailableMemoryWatcher::StartPolling(const MutexAutoLock& aLock)
+ MOZ_REQUIRES(mMutex) {
+ uint32_t pollingInterval = mUnderMemoryPressure
+ ? kLowMemoryPollingIntervalMS
+ : kHighMemoryPollingIntervalMS;
+ if (!mPolling) {
+ // Restart the timer with the new interval if it has stopped.
+ // For testing, use a small polling interval.
+ if (NS_SUCCEEDED(
+ mTimer->InitWithCallback(this, gIsGtest ? 10 : pollingInterval,
+ nsITimer::TYPE_REPEATING_SLACK))) {
+ mPolling = true;
+ }
+ } else {
+ mTimer->SetDelay(gIsGtest ? 10 : pollingInterval);
+ }
+}
+
+// Observe events for shutting down and starting/stopping the timer.
+NS_IMETHODIMP
+nsAvailableMemoryWatcher::Observe(nsISupports* aSubject, const char* aTopic,
+ const char16_t* aData) {
+ nsresult rv = nsAvailableMemoryWatcherBase::Observe(aSubject, aTopic, aData);
+ if (NS_FAILED(rv)) {
+ return rv;
+ }
+
+ if (strcmp(aTopic, "xpcom-shutdown") == 0) {
+ ShutDown();
+ } else {
+ MutexAutoLock lock(mMutex);
+ if (mTimer) {
+ if (strcmp(aTopic, "user-interaction-active") == 0) {
+ StartPolling(lock);
+ } else if (strcmp(aTopic, "user-interaction-inactive") == 0) {
+ StopPolling(lock);
+ }
+ }
+ }
+
+ return NS_OK;
+}
+
+NS_IMETHODIMP nsAvailableMemoryWatcher::GetName(nsACString& aName) {
+ aName.AssignLiteral("nsAvailableMemoryWatcher");
+ return NS_OK;
+}
+
+} // namespace mozilla