Amusingly bizarre DWM bug

[JRS]

Okay, this one has me stumped.

Win 11 24H2. Once booted to desktop dwm.exe has higher than normal CPU usage. If I go into Process Lasso I can see it running at 100% of Logical CPU's 0, 2, 4, 6, 16, 18, 20 and 22 (?). If I open Task Manager it drops back down to normal CPU usage (?!). If I open other apps, programs or games with Task Manager open it's fine. As soon as I close Task Manager the problem returns (?!?!). Nvidia driver version is 576.52, PC spec in forum signature.

Anyone else seen anything like this?

 

[andshrew]

Masking CPU usage when Task Manager is open is a classic malware trait. I would check this is a legit dwm.exe (should have Microsoft digital signatures, should be running from ‪C:\Windows\System32\dwm.exe).

Otherwise I'd guess try rolling back GPU driver.

 

[Rroff]

See if the behaviour still happens with Process Explorer running - which should all you to see into the executable and get some idea of what it is doing. I've seen a few instances of weird behaviour with certain motherboard control software, there is also a bug with some MS maintenance tasks on systems with 32GB or more memory which can sometimes never complete and will kick off whenever they think the system is idle but that usually only loads up 1 core (Task Scheduler should show if they are due/active).