Arch Linux

EinderJam

Member

Registered: 2020-09-06

Posts: 3

Laggy KDE animations and graphic driver confusion

Hi ! I installed Arch and KDE plasma on my Surface Book (dual boot with Windows 10) a few days ago. Due to the particular hardware (detachable screen, touchscreen,etc...), I'm using the linux-surface kernel.

I'm experiencing "laggy" animations (I'm afraid I can't give a more precise definition ) : minimizing, restoring, resizing, moving windows, scrolling konsole and firefox, showing and hiding Application Launcher look laggy.
But it does not happen all the time. Animations are fluid on startup, usually become laggy after some time, then may get fluid again....
Changing compositor rendering backend to XRender or OpenGL3.1 (default is OpenGL2.0) didn't help. I don't know which settings I have to tweak to achieve fluidity.

Note : These lags are more noticeable when the laptop is on battery. If that matters, tlp is installed, configured with default settings.

Then I had a look at the graphic drivers wiki page (The laptop has an I7-6600U CPU -> HD520 iGPU), and this is where the confusion begins :
I installed the mesa package to have 3D acceleration, vulkan-intel for vulkan-support, but did not install xf86-video-intel as it is not recommended for KDE. The kernel should then fallback to modesetting, but this is what lspci gives me :

00:02.0 VGA compatible controller: Intel Corporation Skylake GT2 [HD Graphics 520] (rev 07) (prog-if 00 [VGA controller])
        Subsystem: Microsoft Corporation Device 0014
        Flags: bus master, fast devsel, latency 0, IRQ 136
        Memory at a0000000 (64-bit, non-prefetchable) [size=16M]
        Memory at 90000000 (64-bit, prefetchable) [size=256M]
        I/O ports at 7000 [size=64]
        Expansion ROM at 000c0000 [virtual] [disabled] [size=128K]
        Capabilities: <access denied>
        Kernel driver in use: i915
        Kernel modules: i915 

What is this i915 driver, why is it in use ?

Last edited by EinderJam (2020-09-06 12:59:45)

Lone_Wolf

Member

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 11,911

Re: Laggy KDE animations and graphic driver confusion

The graphics stack on linux is a bit complicated and can be confusing ( [1] tries to explain) .

Kernel modules are linked to hardware and yoru videocard can only be accessed through the i915 kernel module.
modesetting , xf86-video-intel, xf86-video-vesa, xf86-video-fbdev alll use the same kernel module.

Your processor appears to be gen9 and by default uses the mesa IRIS driver.
Check https://wiki.archlinux.org/index.php/In … ver_(i965) and verify if using the older driver helps.

[1]
https://www.reddit.com/r/archlinux/comm … m/djsc8at/ does a good job of explaining

---

Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.

(A works at time B)  && (time C > time B ) ≠  (A works at time C)

EinderJam

Member

Registered: 2020-09-06

Posts: 3

Re: Laggy KDE animations and graphic driver confusion

Thanks the explanation, it was indeed very clear. Using the older driver unfortunately doesn't show any sign of improvement (created a .sh file in /etc/profile.d)

Edit : For testing purposes, I installed the gnome package group, and scrolling is butter-smooth on konsole and firefox. Knowing that GNOME uses Wayland, I tried Plasma with wayland, aaaand I still get lag on animations, and especially on scrolling.
It looks like firefox or the graphic drivers are not the ones to blame...

Last edited by EinderJam (2020-09-08 16:38:07)

EinderJam

Member

Registered: 2020-09-06

Posts: 3

Re: Laggy KDE animations and graphic driver confusion

Small update : Disabling compositing (Alt+Shift+F12) removes the choppiness on firefox scrolling, so I guess there's something wrong with KWin... Which kwin settings should I tweak ?