QOpenGLWidget causes high cpu usage when updating at 60+fps

#include <QtWidgets>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QOpenGLWidget w;
w.resize(800,600);
w.show();
QTimer t(&w);
QObject::connect(&t,&QTimer::timeout,[&]()

);
t.setInterval(10);
t.start();
return a.exec();
}

this widget updates at 100fps and uses 29% of my cpu, 30 times more than the usage at 50fps.
it only happens on Qt::AA_UseDesktopOpenGL, Qt::AA_UseOpenGLES is OK.

I mean call QOpenGLWidget::update() 100 times per second. The refresh rate has been throttled to 60 fps, but there shouldn't be such a high usage.(0.9% at 50 calls per second, but 29% at 100 calls)