Hi,

A few months back I have bought a 4k/60HZ monitor that I am using with my laptop (with a FullHD display). It is plugged in via a USB-Hub that connects to the laptop via Thunderbolt/USB 4 port. The problem is that sometimes after a while, usually when watching videos, eg youtube on laptop screen (as a secondary screen) and something else on the primary (4k external monitor), the fans all of a sudden rev up and everything starts lagging massively. This almost always happens when on a long video/conference call. CPU gets also pretty high, however, the CPU temp seems very low (under 50 deg C).

Other hardware connected to the USB hub are:

• ethernet
• speaker

What could be causing this issue? I have tried reinstalling linux. Switching to GNOME from XFCE. None of it helped. This is my laptop specs:

OS: Arch Linux x86_64
Host: 82BH Yoga 7 14ITL5
Kernel: 6.5.8-arch1-1
Uptime: 18 mins
Packages: 760 (pacman)
Shell: bash 5.1.16
Resolution: 1920x1080
DE: GNOME 45.0
WM: Mutter
WM Theme: Adwaita
Theme: Adwaita [GTK2/3]
Icons: Adwaita [GTK2/3]
Terminal: gnome-terminal
CPU: 11th Gen Intel i5-1135G7 (8) @ 4.
GPU: Intel TigerLake-LP GT2 [Iris Xe G
Memory: 2721MiB / 15795MiB

The first thing I would do is make sure all the cooling vents are free of dust or other obstructions. A can of compressed air can be your friend.

Have done that, even took the bottom case out and cleaned the dust, although there wasn't much anyway.

you might want to upgrade your bios. Otherwise you need to check your fan, if you really removed all the dust.

All the dust is cleaned, double checked again, there isn't anything. I noticed today that my fans could be reacting to the WiFi adapter chip, or network usage in general? Both CPU load and temp seem low (temp under 50deg, load not above 30), but network chip went to around 70deg and fans started to spin, which seems weird since the heat sink isn't even connected to the wifi chip in any way

UPDATE: I noticed this only happens when the laptop is plugged into the AC. When on battery, there is no such thing happening. Any help with this is appreciated

Replace the power supply (or charger).

Which brand is your laptop some models (like Asus) are specially problematic,

https://wiki.archlinux.org/title/Fan_speed_control

You can try to change the sensor read using pwmconfig, for example my laptop in one sensor the scale is wrong and returns the C° in thousands.