I've tracked down the origin of the 16384 limit. It's a combination of:
* Xorg treating all monitors as a single framebuffer; and
* The modesetting driver getting the maximum dimensions from the kernel via
drmModeResPtr; and
* The Intel kernel graphics driver limiting framebuffer sizes to 16384. This
Intel limitation is unavoidable if you want to use the laptop screen as part of
your desktop.
You can also see it in the log:
modeset(0): Allocate new frame buffer 16384x...
So I have a couple of suggestions for getting around it:
* Use a lower scaling factor or the default of 100%; or
* Remove one monitor from the system
** Changed in: mutter (Ubuntu)
Status: New => Invalid
** Also affects: xorg-server (Ubuntu)
Importance: Undecided
Status: New
** Changed in: xorg-server (Ubuntu)
Status: New => Won't Fix
** Also affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu)
Status: New => Opinion
** Summary changed:
- Triple 4K monitor setup with fractional scaling truncated
+ Xorg Triple 4K monitor setup with fractional scaling truncated at 16384 pixels
** Summary changed:
- Xorg Triple 4K monitor setup with fractional scaling truncated at 16384 pixels
+ Xorg multi-monitor setup truncated at 16384 pixels
** Tags added: multimonitor
** Tags added: hybrid i915 nvidia
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https://bugs.launchpad.net/bugs/2017323
Title:
Xorg multi-monitor setup truncated at 16384 pixels
Status in linux package in Ubuntu:
Opinion
Status in mutter package in Ubuntu:
Invalid
Status in xorg-server package in Ubuntu:
Won't Fix
Bug description:
I have three monitors arranged horizontally left-to-right, with
fractional scaling enabled in Xorg mode (not Wayland):
#1: laptop, 3840x2400 native, scaled at 225%
#2: external monitor 1, 3840x2160 native, scaled at 150% (main display)
#3: external monitor 2, 3840x2160 native, scaled at 150%
In this setup, a little more than half of the rightmost monitor is
truncated black.
I suspect it is caused by oversampled screens (fractional scaling) not
fitting into the maximum framebuffer size of 16384x16384, as evidenced
by the following xrandr(1):
$ xrandr | awk '/^[^ ]/ && $2 != "disconnected"'
Screen 0: minimum 320 x 200, current 16384 x 4320, maximum 16384 x 16384
eDP-1 connected 5112x3195+0+0 (normal left inverted right x axis y axis)
366mm x 229mm
DP-2 connected primary 7680x4320+5112+0 (normal left inverted right x axis y
axis) 597mm x 336mm
DP-3 connected 7680x4320+12792+0 (normal left inverted right x axis y axis)
597mm x 336mm
ProblemType: Bug
DistroRelease: Ubuntu 23.04
Package: xserver-xorg 1:7.7+23ubuntu2
ProcVersionSignature: Ubuntu 6.2.0-20.20-generic 6.2.6
Uname: Linux 6.2.0-20-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia zfs zunicode zavl icp zcommon
znvpair
.proc.driver.nvidia.capabilities.gpu0: Error: path was not a regular file.
.proc.driver.nvidia.capabilities.mig: Error: path was not a regular file.
.proc.driver.nvidia.gpus.0000.01.00.0: Error: path was not a regular file.
.proc.driver.nvidia.registry: Binary: ""
.proc.driver.nvidia.suspend: suspend hibernate resume
.proc.driver.nvidia.suspend_depth: default modeset uvm
.proc.driver.nvidia.version:
NVRM version: NVIDIA UNIX x86_64 Kernel Module 525.105.17 Tue Mar 28
18:02:59 UTC 2023
GCC version:
ApportVersion: 2.26.1-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: unknown
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Fri Apr 21 18:51:29 2023
DistUpgraded: 2023-04-20 13:31:05,017 DEBUG Running PostInstallScript:
'/usr/lib/ubuntu-advantage/upgrade_lts_contract.py'
DistroCodename: lunar
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes, including running git bisection searches
GraphicsCard:
Intel Corporation Alder Lake-P Integrated Graphics Controller [8086:46a6]
(rev 0c) (prog-if 00 [VGA controller])
Subsystem: Dell Alder Lake-P Integrated Graphics Controller [1028:0aff]
NVIDIA Corporation GA106M [GeForce RTX 3060 Mobile / Max-Q] [10de:2520] (rev
a1) (prog-if 00 [VGA controller])
Subsystem: Dell GA106M [GeForce RTX 3060 Mobile / Max-Q] [1028:0aff]
MachineType: Dell Inc. XPS 17 9720
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
XDG_RUNTIME_DIR=<set>
ProcKernelCmdLine: BOOT_IMAGE=/BOOT/ubuntu_bm2y56@/vmlinuz-6.2.0-20-generic
root=ZFS=rpool/ROOT/ubuntu_bm2y56 ro init_on_alloc=0
i915.enable_psr2_sel_fetch=0
SourcePackage: xorg
UpgradeStatus: Upgraded to lunar on 2023-04-20 (1 days ago)
dmi.bios.date: 03/20/2023
dmi.bios.release: 1.15
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.15.1
dmi.board.name: 0W7GHH
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvr1.15.1:bd03/20/2023:br1.15:svnDellInc.:pnXPS179720:pvr:rvnDellInc.:rn0W7GHH:rvrA00:cvnDellInc.:ct10:cvr:sku0AFF:
dmi.product.family: XPS
dmi.product.name: XPS 17 9720
dmi.product.sku: 0AFF
dmi.sys.vendor: Dell Inc.
mtime.conffile..etc.logrotate.d.apport: 2023-01-31T20:57:54.273339
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.114-1
version.libgl1-mesa-dri: libgl1-mesa-dri 23.0.2-1ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx 23.0.2-1ubuntu1
version.nvidia-graphics-drivers: nvidia-graphics-drivers-* N/A
version.xserver-xorg-core: xserver-xorg-core 2:21.1.7-1ubuntu3
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:19.1.0-3
version.xserver-xorg-video-intel: xserver-xorg-video-intel
2:2.99.917+git20210115-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau
1:1.0.17-2build1
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