Web lists-archives.com

Output lagging from terminal

From shell running: while true; do date +%s.%N; sleep 1; done

In all cases, the output content is as expected: regular increment of the time displayed, however the time at which the lines are displayed is not regular.

I have an Lenovo X1 Gen 5, with a Thunderbolt dock and DisplayPort monitor connected, using xrandr to extend screen size.

In virtual console (ctrl-alt-F3): the output timing is always regular.
xterm, gnome-terminal, rxvt: the output timing is irregular, no matter which monitor (internal/external) it is running on.

Disconnecting Thunderbolt dock/monitor, causing the X output to become regular. Connecting Thunderbolt dock/monitor, the X output becomes lagged again. I'm not quite sure what's causing it.

$ cat /etc/debian_version

$ uname -a
Linux pdj-x1 4.18.0-2-amd64 #1 SMP Debian 4.18.10-2 (2018-10-07) x86_64 GNU/Linux

Anyone have an idea of why this happens?