Irregular frame rate in fullscreen glxgears on Intel Meteor Lake

[Cyrus Lien]

Frame drops when running glxgears in fullscreen mode.
The issue only appears in Wayland.
Add CLUTTER_PAINT=disable-dynamic-max-render-time fixes it

[Reproduce steps]
  1. run glxgears in fullscreen mode
  2. observe the fps

[glxgears output]
Running synchronized to the vertical refresh. The framerate should be
approximately the same as the monitor refresh rate.
295 frames in 5.0 seconds = 58.949 FPS
183 frames in 5.0 seconds = 36.584 FPS
212 frames in 5.0 seconds = 42.231 FPS
176 frames in 5.0 seconds = 35.022 FPS
166 frames in 5.0 seconds = 33.048 FPS
159 frames in 5.0 seconds = 31.775 FPS
222 frames in 5.0 seconds = 44.363 FPS
197 frames in 5.0 seconds = 39.379 FPS
164 frames in 5.0 seconds = 32.784 FPS

[Related information]
Ubuntu 24.04
Mutter: 46.0-1ubuntu9
GPU model: Intel Corporation Meteor Lake-P [Intel Arc Graphics]
Graphics driver in use: i915

ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: gnome-shell 46.0-0ubuntu5.1
ProcVersionSignature: Ubuntu 6.8.0-35.35-generic 6.8.4
Uname: Linux 6.8.0-35-generic x86_64
ApportVersion: 2.28.1-0ubuntu3
Architecture: amd64
CasperMD5CheckMismatches: ./.disk/casper-uuid-generic ./casper/initrd ./casper/minimal.standard.live.hotfix.squashfs ./casper/minimal.standard.hotfix.squashfs ./casper/minimal.hotfix.squashfs ./boot/grub/grub.cfg
CasperMD5CheckResult: fail
Date: Thu Jun 6 14:56:43 2024
DisplayManager: gdm3
DistributionChannelDescriptor:
 # This is the distribution channel descriptor for Ubuntu 24.04 for Dell
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-noble-hwe-20240528-99
InstallationDate: Installed on 2024-06-06 (0 days ago)
InstallationMedia: Ubuntu OEM 24.04 LTS "Noble Numbat" - Release amd64 (20240528)
RelatedPackageVersions: mutter-common 46.0-1ubuntu9
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)

[Cyrus Lien (cyruslien)]

Confirmed this is an i915 driver issue and commit in v6.9-rc1 fixes it.
c08c364102 drm/i915: Bypass LMEMBAR/GTTMMADR for MTL stolen memory access (https://patchwork.freedesktop.org/patch/576970/)

Thank you all for your help. Let's invalid it.