QThread is slow on macOS. What is the reason?

Question

Qt

Code example:

int main(int argc, char *argv[])
{
  QApplication a(argc, argv);

  Worker *worker = new Worker();
  QThread *thread = new QThread;
  worker->moveToThread(thread);
  QObject::connect(thread, SIGNAL(started()), observer, SLOT(doWork()));
  QObject::connect(worker, SIGNAL(finished()), thread, SLOT(quit()));
  QObject::connect(worker, SIGNAL(finished()), worker,
                   SLOT(deleteLater()));
  QObject::connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
  thread->start(QThread::HighestPriority);

  return a.exec();
}

void Worker::doWork() {
  while (!is_stop) {
    qDebug() << count;
    count++;
    thread()->msleep(1000);
  }

  emit finished();
}

For the first 20-30 seconds, doWork() works fine, outputting every second, then the output slows down and happens every 5-10 seconds, like macOS lowers the process priority or something. What could be the reason? I tried to run as root, increase the priority of the thread, it does not help. On Linux, this code works fine.

Answer 1

Try using a timer with QEventLoop instead of msleep.
It's better to include QThread::finished() rather than worker in deleteLater().
Yes, and a.exec(); by itself will not wait for those deletion signals, you must also thread->wait() after a.exec() and then return 0;