https://bugs.kde.org/show_bug.cgi?id=442386
Bug ID: 442386
Summary: Prefer EGL to GLX for GL support also on X11
Product: kwin
Version: 5.18.7
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: glx
Assignee: kwin-bugs-n...@kde.org
Reporter: k...@bluewin.ch
Target Milestone: ---
Hi to all
Okay, this is more a "feature request" than a bug report. After intensive
testing, especially on older Apple Intel iMac computers, I must say that a
switch to the EGL backend would make absolutely sense. This will improve in
some cases dramatically the entire user experience of the GUI on older
hardware.
I can confirm this for the old Apple iMac 5,1 series were Kubuntu 20.04 LTS has
to be installed via CSM Bios emulation. When the normal GLX backend is used for
compositing, the GUI hangs reproducible after login. This happens always right
after the "notification message" regarding the WiFi status is displayed. When I
start then the terminal via alt + F2 I can see in dmesg the message "kworker
blocked for more than 120 seconds". This "GLX hanging problem" is also present
when a copy action is started from a network share.
However, a switch to the EGL backend fixed the problem. It furthermore also
improves noticeable the overall response of the KDE GUI:
export KWIN_COMPOSE=O2ES
sudo nano /etc/profile.d/kwin.sh
So for me it looks that as for 2021 the EGL implementation is superior to the
GLX one. And this is now true also for the X11 window system!
STEPS TO REPRODUCE
1. Install Kubuntu 20.04 LTS at an iMac 5,1 computer*
2. After the first start-up X is "hanging around" when notifications are
displayed
*Currently an install is only possible via CSM Bios emulation. A native EFI
installation is not supported because of a "32bit EFI vs. 64bit CPU mismatch".
However, there were some changes in later Linux kernel versions (since 5.7)
which added a flag called "LOAD_X64_ON_IA32_ENABLE". This would theoretically
make a mixed-mode EFI installation possible. But so far I know the Kubuntu devs
didn't set that flag on their kernels. As of 2021 only Archlinux seems to have
it enabled.
OBSERVED RESULT
X is under more system-load reproducible hanging (for around 2 minutes) when
GLX is used
X is not hanging when EGL is used, also not under higher system-load
EXPECTED RESULT
X should run fine also with GLX
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 5.11.0-34-generic
KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
GPU Hardware: Radeon X1600 series (Mesa 21.0.3, R300 Gallium3D driver used)
ADDITIONAL INFORMATION
It should be noted that also Gnome is "defaulting" X (since four months) to
EGL:
https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/3540
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