I recently noticed that some of our pyqtgraph plots were a lot slower than I expected it turns out that plot performs very bad for me with a pen size larger than 1.

In https://github.com/pyqtgraph/pyqtgraph/blob/develop/examples/PlotSpeedTest.py
I can sustain around 300 fps with the default setting. However changing the pen as in
doing curve = p.plot(pen=pg.mkPen(width=1.01)) the performance drops to 2/3 fps
with a width=1 or less everything is fine.

Python 3.6
PyQt 5.9 installed from pip similar for 5.6 from Anaconda
PyQtGraph 0.10 and latest master
both windows as osx