a4035fc68e
Add documentation explaining how to change the primary GPU using a udev rule. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4218>
43 lines
1.5 KiB
Markdown
43 lines
1.5 KiB
Markdown
# Multi-GPU
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## Selecting the primary GPU
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When multiple GPUs are present in the same system, Mutter applies a series of
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rules to select one of them as primary. However, it is possible to manually
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select a different GPU by using a udev rule.
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To illustrate it with an example, I'm going to make the NVIDIA GPU in my system
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to be selected as the primary GPU.
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Start by finding the vendor and device IDs of the target GPU:
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```bash
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$ lspci -nn
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[...]
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24:00.0 VGA compatible controller [0300]: NVIDIA Corporation AD107 [GeForce RTX 4060] [10de:2882] (rev a1)
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```
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In this case, we are looking for the vendor ID (10de) and the product (2882).
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Next, create rule to set the desired GPU as primary. Make sure to replace the
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vendor and device IDs:
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```bash
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$ cat /etc/udev/rules.d/61-mutter-preferred-primary-gpu.rules
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SUBSYSTEM=="drm", ENV{DEVTYPE}=="drm_minor", ENV{DEVNAME}=="/dev/dri/card[0-9]", SUBSYSTEMS=="pci", ATTRS{vendor}=="0x10de", ATTRS{device}=="0x2882", TAG+="mutter-device-preferred-primary"
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```
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Finally, restart and check that the desired GPU was selected:
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```bash
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$ journalctl -b0 /usr/bin/gnome-shell
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[...]
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Device '/dev/dri/card1' prefers shadow buffer
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Added device '/dev/dri/card1' (nouveau) using non-atomic mode setting.
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Device '/dev/dri/card2' prefers shadow buffer
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Added device '/dev/dri/card2' (amdgpu) using atomic mode setting.
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Created gbm renderer for '/dev/dri/card1'
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Created gbm renderer for '/dev/dri/card2'
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GPU /dev/dri/card1 selected primary given udev rule
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```
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