lazy.reload_config() method leaks CPU

Every call to lazy.reload_config() increases the average CPU usage by Qtile. It is quite a small increase, but it builds up rather quickly if you reload the config often, when testing new settings for example.

By doing a few calls to lazy.reload_config() in succession, you can easily push up average CPU usage from around 1% to 8-10%…the CPU usage stays at that level, even if left for 20 minutes or more…quitting Qtile, and starting it with the same config, results in expected CPU usage of around 1%, even if left for 24 hours or more.

This is on Qtile version 0.20.0 running on ArchLinux (kernel 5.16.8) with xorg-server 21.1.3 and Python 3.10.2

[morne]

@elParaguayo - I just did a test and I can confirm that it fixes the problem.

Great work and many thanks !

[elParaguayo]

OK. I’ve actually got a pretty good idea of what’s causing this. The clue was in you saying you’ve got multiple instances.

Basically, when we reload the config we finalize currently running widgets. We do this by iterating over a dictionary of widgets where the key is the widget name. The name defaults to the widget class name. This means that, if you use multiple instances of a widget class, there’s only going to be one instance of that widget in the map. The rest will therefore not be finalized and their timers will carry on running.

#3010 should therefore solve this issue. I’ll take another look at that PR and see if we can get it in a good form for you to test.

If not, I can knock out a quicker fix for this particular issue.