Run worker pool at lowest thread priority (#1497)

src/librssguard/CMakeLists.txt

@@ -243,6 +243,8 @@ set(SOURCES
   miscellaneous/templates.h
   miscellaneous/textfactory.cpp
   miscellaneous/textfactory.h
+  miscellaneous/thread.cpp
+  miscellaneous/thread.h
   network-web/adblock/adblockdialog.cpp
   network-web/adblock/adblockdialog.h
   network-web/adblock/adblockicon.cpp

src/librssguard/core/feeddownloader.cpp

@@ -10,14 +10,14 @@
 #include "exceptions/filteringexception.h"
 #include "miscellaneous/application.h"
 #include "miscellaneous/settings.h"
+#include "miscellaneous/thread.h"
 #include "services/abstract/cacheforserviceroot.h"
 #include "services/abstract/feed.h"
 #include "services/abstract/labelsnode.h"
 
 #include <QDebug>
 #include <QJSEngine>
 #include <QString>
-#include <QThread>
 #include <QtConcurrentMap>
 
 FeedDownloader::FeedDownloader()
@@ -47,7 +47,7 @@ void FeedDownloader::synchronizeAccountCaches(const QList<CacheForServiceRoot*>&
 
   for (CacheForServiceRoot* cache : caches) {
     qDebugNN << LOGSEC_FEEDDOWNLOADER << "Synchronizing cache back to server on thread"
-             << QUOTE_W_SPACE_DOT(QThread::currentThreadId());
+             << QUOTE_W_SPACE_DOT(getThreadID());
     cache->saveAllCachedData(false);
 
     if (m_stopCacheSynchronization) {
@@ -77,7 +77,7 @@ void FeedDownloader::updateFeeds(const QList<Feed*>& feeds) {
   }
   else {
     qDebugNN << LOGSEC_FEEDDOWNLOADER << "Starting feed updates from worker in thread"
-             << QUOTE_W_SPACE_DOT(QThread::currentThreadId());
+             << QUOTE_W_SPACE_DOT(getThreadID());
 
     // Job starts now.
     emit updateStarted();
@@ -155,6 +155,9 @@ void FeedDownloader::updateFeeds(const QList<Feed*>& feeds) {
 
     std::function<FeedUpdateResult(const FeedUpdateRequest&)> func =
       [=](const FeedUpdateRequest& fd) -> FeedUpdateResult {
+      #if defined(Q_OS_LINUX)
+      setThreadPriority(Priority::LOWEST);
+      #endif
       return updateThreadedFeed(fd);
     };
 
@@ -220,7 +223,7 @@ void FeedDownloader::updateOneFeed(ServiceRoot* acc,
     acc->itemChanged({feed});
   }
 
-  qlonglong thread_id = qlonglong(QThread::currentThreadId());
+  qlonglong thread_id = getThreadID();
 
   qDebugNN << LOGSEC_FEEDDOWNLOADER << "Downloading new messages for feed ID" << QUOTE_W_SPACE(feed->customId())
            << "URL:" << QUOTE_W_SPACE(feed->source()) << "title:" << QUOTE_W_SPACE(feed->title()) << "in thread "
@@ -435,7 +438,7 @@ void FeedDownloader::updateOneFeed(ServiceRoot* acc,
 
 void FeedDownloader::finalizeUpdate() {
   qDebugNN << LOGSEC_FEEDDOWNLOADER << "Finished feed updates in thread"
-           << QUOTE_W_SPACE_DOT(QThread::currentThreadId());
+           << QUOTE_W_SPACE_DOT(getThreadID());
 
   m_feeds.clear();
 

src/librssguard/database/databasecleaner.cpp

@@ -4,14 +4,14 @@
 
 #include "database/databasequeries.h"
 #include "miscellaneous/application.h"
+#include "miscellaneous/thread.h"
 
 #include <QDebug>
-#include <QThread>
 
 DatabaseCleaner::DatabaseCleaner(QObject* parent) : QObject(parent) {}
 
 void DatabaseCleaner::purgeDatabaseData(CleanerOrders which_data) {
-  qDebugNN << LOGSEC_DB << "Performing database cleanup in thread:" << QUOTE_W_SPACE_DOT(QThread::currentThreadId());
+  qDebugNN << LOGSEC_DB << "Performing database cleanup in thread:" << QUOTE_W_SPACE_DOT(getThreadID());
 
   // Inform everyone about the start of the process.
   emit purgeStarted();

src/librssguard/database/databasedriver.cpp

@@ -5,6 +5,7 @@
 #include "definitions/definitions.h"
 #include "exceptions/applicationexception.h"
 #include "miscellaneous/iofactory.h"
+#include "miscellaneous/thread.h"
 
 #include <QDir>
 #include <QSqlError>
@@ -14,7 +15,7 @@
 DatabaseDriver::DatabaseDriver(QObject* parent) : QObject(parent) {}
 
 QSqlDatabase DatabaseDriver::threadSafeConnection(const QString& connection_name, DesiredStorageType desired_type) {
-  qlonglong thread_id = qlonglong(QThread::currentThreadId());
+  qlonglong thread_id = getThreadID();
   bool is_main_thread = QThread::currentThread() == qApp->thread();
 
   QSqlDatabase database =

src/librssguard/gui/dialogs/formmain.cpp

@@ -27,6 +27,7 @@
 #include "miscellaneous/iconfactory.h"
 #include "miscellaneous/mutex.h"
 #include "miscellaneous/settings.h"
+#include "miscellaneous/thread.h"
 #include "network-web/adblock/adblockicon.h"
 #include "network-web/adblock/adblockmanager.h"
 #include "network-web/webfactory.h"
@@ -38,7 +39,6 @@
 #include <QFileDialog>
 #include <QRect>
 #include <QScopedPointer>
-#include <QThread>
 #include <QTimer>
 #include <QToolButton>
 #include <QWidgetAction>
@@ -54,7 +54,7 @@
 FormMain::FormMain(QWidget* parent, Qt::WindowFlags f)
   : QMainWindow(parent, f), m_ui(new Ui::FormMain), m_trayMenu(nullptr), m_statusBar(nullptr) {
   qDebugNN << LOGSEC_GUI
-           << "Creating main application form in thread:" << QUOTE_W_SPACE_DOT(QThread::currentThreadId());
+           << "Creating main application form in thread:" << QUOTE_W_SPACE_DOT(getThreadID());
   // setAttribute(Qt::WA_WindowPropagation, true);
   m_ui->setupUi(this);
   qApp->setMainForm(this);

src/librssguard/gui/webviewers/qtextbrowser/textbrowserviewer.cpp

@@ -42,7 +42,7 @@ TextBrowserViewer::TextBrowserViewer(QWidget* parent)
   setDocument(m_document.data());
 
   m_resourceDownloader->moveToThread(m_resourceDownloaderThread);
-  m_resourceDownloaderThread->start();
+  m_resourceDownloaderThread->start(QThread::LowPriority);
 
   connect(this, &TextBrowserViewer::reloadDocument, this, [this]() {
     const auto scr = verticalScrollBarPosition();

src/librssguard/miscellaneous/application.cpp

@@ -1157,6 +1157,12 @@ void Application::setupWorkHorsePool() {
     m_workHorsePool->setMaxThreadCount((std::min)(MAX_THREADPOOL_THREADS, 2 * ideal_th_count));
   }
 
+#if QT_VERSION_MAJOR == 6
+  // Avoid competing with interactive processes/threads by running the
+  // worker pool at a very low priority
+  m_workHorsePool->setThreadPriority(QThread::LowestPriority);
+#endif
+
   // NOTE: Do not expire threads so that their IDs are not reused.
   // This fixes cross-thread QSqlDatabase access.
   m_workHorsePool->setExpiryTimeout(-1);

src/librssguard/miscellaneous/feedreader.cpp

@@ -128,7 +128,7 @@ void FeedReader::initializeFeedDownloader() {
     connect(m_feedDownloader, &FeedDownloader::updateStarted, this, &FeedReader::feedUpdatesStarted);
     connect(m_feedDownloader, &FeedDownloader::updateFinished, qApp->feedUpdateLock(), &Mutex::unlock);
 
-    m_feedDownloaderThread->start();
+    m_feedDownloaderThread->start(QThread::LowPriority);
   }
 }
 

src/librssguard/miscellaneous/thread.cpp

@@ -0,0 +1,67 @@
+// For license of this file, see <project-root-folder>/LICENSE.md.
+
+#include "definitions/definitions.h"
+#include "miscellaneous/thread.h"
+
+#include <QThread>
+
+#if defined(Q_OS_LINUX)
+#include <sched.h>
+#include <sys/resource.h>
+#include <unistd.h>
+#endif
+
+// Returns the thread ID of the caller
+qlonglong getThreadID() {
+  #if defined(Q_OS_LINUX)
+  return qlonglong(gettid());
+  #else
+  return qlonglong(QThread::currentThreadId());
+  #endif
+}
+
+#if defined(Q_OS_LINUX)
+// On Linux QThread priorities do nothing with the default scheduler SCHED_OTHER
+// Set the nice value manually in this case until Qt supports nice values
+void setThreadPriority(Priority prio) {
+  int current_policy = sched_getscheduler(0);
+  if (current_policy != -1) {
+    // If the current scheduling policy is neither of these the QThread priority should be working
+    if (current_policy != SCHED_BATCH && current_policy != SCHED_OTHER) {
+      return;
+    }
+
+    // Set the scheduler to SCHED_BATCH if needed, indicating that this process is non-interactive
+    if (current_policy == SCHED_OTHER) {
+      struct sched_param p = {0};
+      if (sched_setscheduler(0, SCHED_BATCH, &p) != 0) {
+        qDebugNN << "Setting the scheduler to SCHED_BATCH for thread"
+                 << QUOTE_W_SPACE(getThreadID())
+                 << "failed with error" << QUOTE_W_SPACE_DOT(errno);
+        // We can still try to set the nice value
+      }
+    }
+
+    errno = 0; // Clear errno since -1 is a legitimate return value
+    int current_priority = getpriority(PRIO_PROCESS, 0);
+    if (errno != 0) {
+      qDebugNN << "Getting the priority for thread"
+               << QUOTE_W_SPACE(getThreadID())
+               << "failed with error" << QUOTE_W_SPACE_DOT(errno);
+    } else {
+      if (current_priority != prio) {
+        setpriority(PRIO_PROCESS, 0, prio);
+        if (errno != 0) {
+          qDebugNN << "Setting the priority for thread"
+                   << QUOTE_W_SPACE(getThreadID())
+                   << "failed with error" << QUOTE_W_SPACE_DOT(errno);
+        }
+      }
+    }
+  } else {
+    qDebugNN << "Getting the priority for thread"
+             << QUOTE_W_SPACE(getThreadID())
+             << "failed with error" << QUOTE_W_SPACE_DOT(errno);
+  }
+}
+#endif

src/librssguard/miscellaneous/thread.h

@@ -0,0 +1,19 @@
+// For license of this file, see <project-root-folder>/LICENSE.md.
+
+#ifndef THREAD_H
+#define THREAD_H
+
+qlonglong getThreadID();
+
+#if defined(Q_OS_LINUX)
+// Values corresponding to nice values
+enum Priority {
+  LOWEST = 19,
+  LOW    = 10,
+  NORMAL = 0
+};
+
+void setThreadPriority(Priority);
+#endif
+
+#endif // THREAD_H

src/librssguard/network-web/adblock/adblockmanager.cpp

@@ -23,7 +23,6 @@
 #include <QJsonDocument>
 #include <QJsonObject>
 #include <QMessageBox>
-#include <QThread>
 #include <QTimer>
 #include <QUrlQuery>