[XLibre and Xorg] Xrandr calls to X server cause stutters.

[itz-me-zappex]

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Describe your issue

Running xrandr command causes stutters, probably when it asks X server for an information. Same happens with Redshift, it seems it makes calls to randr, and that causes stuttering every 5 seconds when it adjusts gamma ramps on background. I should note that Redshift does not cause such great stutters as xrandr, but still does.

Steps to reproduce

1. Run any application (e.g. glxgears, vkcube, game etc.) with mangohud or somehow else to see frametime graph.
2. Open terminal and run xrandr (xrandr -q) or xrandr -v. Both make calls to X server.
3. Run any other command in terminal, e.g. touch test and rm test, to make sure this is not caused by terminal emulator.

What did you expect?

I guess X server should not lock everything when handle randr calls and stutters should not happen.

Additional Information

Compiled against cb5f2cd (latest commit currently) + this.

Distro: Artix Linux
DE/WM: BSPWM
Compositor: Picom (can reproduce with it disabled)
GPU: noVideo GTX 1050Ti, 580.126.18 (proprietary, not open kernel modules one)
X: XLibre

UPD: Reproduced the same on following (laptop):
Distro: Arch Linux
DE/WM: Cinnamon + Muffin
Compositor: Built into Muffin
GPU: UHD 600 (i915, modesetting in xorg.conf)
X: X.org

Video:
https://github.com/user-attachments/assets/69830b4e-435d-47e7-be84-874616546d4f

Please look at commands I run and frametime graph, there is stutter when xrandr obtains info about server-side version or when it gets monitor list, resolutions, refresh rates etc.

Extra fields

• I have checked the existing issues
• I have read the Contributing Guidelines
• I'd like to work on this issue

[chankongus]

Can confirm the same happens on my end too...

Slightly offtopic [Click me!]

...but I'm not exactly convinced this is caused JUST by xrandr but, alas more like it's the ways WMs/DEs interact with X11.

Anyway, I observed similar stuff as you've reported and more - moving/resizing and overall interacting with windows causes either mild or severe stutter and/or GPU Spikes. It's even worse when you try to run compositor on top.

The ways similar stutter (+ worse) happen for reference:

• Run eglgears_x11, vkcube and glxgears (or idk vkcube 3 times, but it's better to run 3 different APIs imo) at once in the same workspace and then:
  • Switching focus between the different windows... or different workspaces [will cause minor stutter (on all HW)]
  • Poping them in and out of the floating mode [will cause minor stutter (on all HW)]
  • Moving one of them [will cause SEVERE stutter + 90% GPU usage spike (on Nvidia*)]
  • Resizing one of them [will cause SEVERE stutter + 90% GPU usage spike (on Nvidia*)]
    *Couldn't reproduce on other HW

You might ask:

Alright, but why does this matter, this doesn't seem like it's at all related to the issue...

Until you notice that BSPWM/i3wm uses libxcb - if this was just xrandr/libXrandr/libX11, then this stuttering wouldn't happen on newer and supposedly threadsafe libxcb!

Sorry for this offtopic tangent, but as I said I'm not so sure this is JUST xrandr's fault. More like it's further down the libX11/libxcb line, either it's Xorg/Xlibre itself or worse, the GPU driver doing something funky...