Only reserialize hosts if a serializable attribute changed

app/backend/computermanager.cpp

@@ -167,6 +167,7 @@ ComputerManager::ComputerManager(QObject *parent)
         settings.setArrayIndex(i);
         NvComputer* computer = new NvComputer(settings);
         m_KnownHosts[computer->uuid] = computer;
+        m_LastSerializedHosts[computer->uuid] = *computer;
     }
     settings.endArray();
 
@@ -250,6 +251,14 @@ void DelayedFlushThread::run() {
 
             // Reset the delayed flush flag to ensure any racing saveHosts() call will set it again
             m_ComputerManager->m_NeedsDelayedFlush = false;
+
+            // Update the last serialized hosts map under the delayed flush mutex
+            m_ComputerManager->m_LastSerializedHosts.clear();
+            for (const NvComputer* computer : m_ComputerManager->m_KnownHosts) {
+                // Copy the current state of the NvComputer to allow us to check later if we need
+                // to serialize it again when attribute updates occur.
+                m_ComputerManager->m_LastSerializedHosts[computer->uuid] = *computer;
+            }
         }
 
         // Perform the flush
@@ -433,6 +442,17 @@ void ComputerManager::handleMdnsServiceResolved(MdnsPendingComputer* computer,
     computer->deleteLater();
 }
 
+void ComputerManager::saveHost(NvComputer *computer)
+{
+    // If no serializable properties changed, don't bother saving hosts
+    QMutexLocker lock(&m_DelayedFlushMutex);
+    if (!m_LastSerializedHosts.value(computer->uuid).isEqualSerialized(*computer)) {
+        // Queue a request for a delayed flush to QSettings outside of the lock
+        lock.unlock();
+        saveHosts();
+    }
+}
+
 void ComputerManager::handleComputerStateChanged(NvComputer* computer)
 {
     emit computerStateChanged(computer);
@@ -442,8 +462,8 @@ void ComputerManager::handleComputerStateChanged(NvComputer* computer)
         emit quitAppCompleted(QVariant());
     }
 
-    // Save updated hosts to QSettings
-    saveHosts();
+    // Save updates to this host
+    saveHost(computer);
 }
 
 QVector<NvComputer*> ComputerManager::getComputers()
@@ -479,7 +499,7 @@ public:
             m_ComputerManager->m_KnownHosts.remove(m_Computer->uuid);
         }
 
-        // Persist the new host list
+        // Persist the new host list with this computer deleted
         m_ComputerManager->saveHosts();
 
         // Delete the polling entry first. This will stop all polling threads too.
@@ -520,9 +540,6 @@ void ComputerManager::renameHost(NvComputer* computer, QString name)
 
 void ComputerManager::clientSideAttributeUpdated(NvComputer* computer)
 {
-    // Persist the change
-    saveHosts();
-
     // Notify the UI of the state change
     handleComputerStateChanged(computer);
 }
@@ -580,7 +597,7 @@ private:
                break;
            case NvPairingManager::PairState::PAIRED:
                // Persist the newly pinned server certificate for this host
-               m_ComputerManager->saveHosts();
+               m_ComputerManager->saveHost(m_Computer);
 
                emit pairingCompleted(m_Computer, nullptr);
                break;

app/backend/computermanager.h

@@ -251,6 +251,8 @@ private slots:
 private:
     void saveHosts();
 
+    void saveHost(NvComputer* computer);
+
     QHostAddress getBestGlobalAddressV6(QVector<QHostAddress>& addresses);
 
     void startPollingComputer(NvComputer* computer);
@@ -259,6 +261,7 @@ private:
     QReadWriteLock m_Lock;
     QMap<QString, NvComputer*> m_KnownHosts;
     QMap<QString, ComputerPollingEntry*> m_PollEntries;
+    QHash<QString, NvComputer> m_LastSerializedHosts; // Protected by m_DelayedFlushMutex
     QSharedPointer<QMdnsEngine::Server> m_MdnsServer;
     QMdnsEngine::Browser* m_MdnsBrowser;
     QVector<MdnsPendingComputer*> m_PendingResolution;

app/backend/nvcomputer.cpp

@@ -94,7 +94,7 @@ void NvComputer::serialize(QSettings& settings, bool serializeApps) const
     settings.setValue(SER_NVIDIASOFTWARE, isNvidiaServerSoftware);
 
     // Avoid deleting an existing applist if we couldn't get one
-    if (!appList.isEmpty()) {
+    if (!appList.isEmpty() && serializeApps) {
         settings.remove(SER_APPLIST);
         settings.beginWriteArray(SER_APPLIST);
         for (int i = 0; i < appList.count(); i++) {
@@ -105,6 +105,21 @@ void NvComputer::serialize(QSettings& settings, bool serializeApps) const
     }
 }
 
+bool NvComputer::isEqualSerialized(const NvComputer &that) const
+{
+    return this->name == that.name &&
+           this->hasCustomName == that.hasCustomName &&
+           this->uuid == that.uuid &&
+           this->macAddress == that.macAddress &&
+           this->localAddress == that.localAddress &&
+           this->remoteAddress == that.remoteAddress &&
+           this->ipv6Address == that.ipv6Address &&
+           this->manualAddress == that.manualAddress &&
+           this->serverCert == that.serverCert &&
+           this->isNvidiaServerSoftware == that.isNvidiaServerSoftware &&
+           this->appList == that.appList;
+}
+
 void NvComputer::sortAppList()
 {
     std::stable_sort(appList.begin(), appList.end(), [](const NvApp& app1, const NvApp& app2) {

app/backend/nvcomputer.h

@@ -8,6 +8,16 @@
 #include <QSettings>
 #include <QRunnable>
 
+class CopySafeReadWriteLock : public QReadWriteLock
+{
+public:
+    CopySafeReadWriteLock() = default;
+
+    // Don't actually copy the QReadWriteLock
+    CopySafeReadWriteLock(const CopySafeReadWriteLock&) {}
+    CopySafeReadWriteLock& operator=(const CopySafeReadWriteLock &) { return *this; }
+};
+
 class NvComputer
 {
     friend class PcMonitorThread;
@@ -22,6 +32,12 @@ private:
     bool pendingQuit;
 
 public:
+    NvComputer() = default;
+
+    NvComputer(const NvComputer& other) = default;
+
+    NvComputer& operator=(const NvComputer &) = default;
+
     explicit NvComputer(NvHTTP& http, QString serverInfo);
 
     explicit NvComputer(QSettings& settings);
@@ -51,6 +67,9 @@ public:
     void
     serialize(QSettings& settings, bool serializeApps) const;
 
+    bool
+    isEqualSerialized(const NvComputer& that) const;
+
     enum PairState
     {
         PS_UNKNOWN,
@@ -91,9 +110,10 @@ public:
     QSslCertificate serverCert;
     QVector<NvApp> appList;
     bool isNvidiaServerSoftware;
+    // Remember to update isEqualSerialized() when adding fields here!
 
     // Synchronization
-    mutable QReadWriteLock lock;
+    mutable CopySafeReadWriteLock lock;
 
 private:
     uint16_t externalPort;