Public bug reported:
Ubuntu 26.04.1 was upgraded from Ubuntu 24.04. The graphical login
screen is significantly delayed during boot on a hybrid Intel/NVIDIA
system.
Expected behavior
-----------------
GDM should display the graphical login screen shortly after starting, without a
long pause during the first GNOME Shell/Mutter initialization.
Actual behavior
---------------
The problem is reproducible across multiple boots.
The first `/usr/bin/gnome-shell --mode=gdm` process spends approximately
43–47 seconds between:
- GNOME Shell/Mutter starting as a Wayland display server
- creation of Mutter's KMS thread
Once KMS initialization begins, GPU/DRM enumeration is fast
(approximately one second).
By comparison, after login the user's GNOME Shell initializes the
equivalent graphics sequence in approximately 0.25 seconds.
On one observed boot the first GDM greeter eventually timed out and GDM
started a second greeter; the second greeter initialized the graphics
stack almost immediately.
Hardware / graphics configuration
---------------------------------
- Intel Alder Lake-S GT1 UHD 770 (i915)
- NVIDIA RTX A2000 (nvidia)
- NVIDIA driver 580.178.04
- PRIME mode: on-demand
- Intel/i915 is selected by Mutter as the primary GPU
Both i915 and nvidia DRM kernel drivers are initialized well before GDM
starts.
Investigation performed
-----------------------
Systemd/journal timelines from several boots consistently localize the delay to
the first GDM GNOME Shell/Mutter process.
The following have been investigated and do not appear to be the serial
cause of the delay:
- Docker/containerd (starts in parallel with GDM)
- Plymouth (`plymouth-quit-wait` is waiting for the graphical transition)
- Ollama GPU discovery (disabled for a reproduction; the GDM delay persisted)
- DRM/KMS enumeration itself
A partial `strace` of the first `gnome-shell --mode=gdm` process
captured approximately the last 13 seconds before KMS initialization. It
showed active loading/initialization involving EGL/GLVND/NVIDIA/Mesa,
but no single long blocking syscall. The trace attached too late to
capture approximately the first 27 seconds of the unexplained interval.
Correlation with Mutter 50.1 source currently places the unexplained
delay before `meta_kms_new()`, during the first user-space
graphics/backend initialization. This does NOT establish Mutter, NVIDIA,
Mesa or GLVND individually as the root cause.
The first-process-only behavior could be consistent with some form of
graphics stack initialization/warm-up, but no particular cache or
component has been demonstrated responsible.
Reproducibility
---------------
Reproduced on multiple consecutive boots.
Examples of measured Wayland-to-KMS intervals:
- approximately 47.0 seconds
- approximately 42.9 seconds
A subsequent GNOME Shell initialization on the same boot performs the
KMS/GPU initialization almost immediately.
Additional information
----------------------
I have retained detailed boot journals, systemd timelines, two reproductions,
the partial strace, and analysis of the initialization sequence.
Before changing PRIME configuration, GDM configuration, graphics
drivers, or adding further instrumentation, I would appreciate guidance
on the most useful next diagnostic step. In particular, I can capture
the first `gnome-shell --mode=gdm` process from exec if that would be
useful.
No graphics-driver or PRIME workaround has been applied while
reproducing this issue.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: mutter 50.1-0ubuntu2.5
ProcVersionSignature: Ubuntu 7.0.0-38.38-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Sat Oct 24 20:51:11 2026
InstallationDate: Installed on 2022-03-24 (1676 days ago)
InstallationMedia: Ubuntu 20.04.4 LTS "Focal Fossa" - Release amd64 (20220223)
SourcePackage: mutter
UpgradeStatus: Upgraded to resolute on 2026-10-24 (1 days ago)
** Affects: mutter (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2172148
Title:
GDM login screen delayed ~45 seconds before Mutter KMS initialization
on hybrid Intel/NVIDIA system
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