xfwm4 increased CPU usage on Intel graphics when monitor is in standby/suspend/off mode
On two different laptops with Intel graphics running Arch Linux with XFCE, when the monitor is put in standby/suspend/off mode (by XFCE Power Manager, or by xscreensaver, or manually with
xset -d :0.0 dpms force <standby/suspend/off>), xfwm4 CPU usage - as reported by "top" over ssh while nothing is drawing anything particular on the screen - increases from ~0% to ~4%. This happens only when xfwm4's compositor is on, if I turn it off it doesn't happen; it also doesn't happen with fluxbox, nor with XFCE on my desktop pc with Nvidia graphics. It happens with Xorg modesetting driver and Intel driver.