Multi GPU instructions (#267)

Co-authored-by: WasteOfO2 <pvpsocialonline18@mail.com>
Co-authored-by: Mihai Fufezan <fufexan@protonmail.com>

pages/Configuring/Multi-GPU.md

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+# Table of contents
+
+{{< toc >}}
+
+# General
+
+If your host machine uses multiple GPUs, you may want to primarily use one GPU
+for rendering all the elements for Hyprland including windows, animations, and
+another for hardware acceleration for certain applications, etc.
+
+This setup is very common in the likes of gaming laptops, 
+GPU-passthrough (without VFIO) capable hosts, and if you have multiple GPUs in
+general.
+
+# Detecting GPUs
+
+For this case, the writer is taking the example of their laptop.
+
+Upon running `lspci | grep -E 'VGA|3D'`, One can list all the video devices
+available.
+
+```
+01:00.0 VGA compatible controller: NVIDIA Corporation TU117M [GeForce GTX 1650 Mobile / Max-Q] (rev a1)
+06:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Cezanne [Radeon Vega Series / Radeon Vega Mobile Series] (rev c6)
+```
+Here it is clear that 2 GPUs are available, the dedicated NVIDIA GTX 1650 Mobile
+/ Max-Q and the integrated AMD Cezanne Radeon Vega Series GPU.
+
+Now, run `ls -l /dev/dri/by-path`
+
+```
+ total 0
+lrwxrwxrwx 1 root root  8 Jul 14 15:45 pci-0000:01:00.0-card -> ../card0
+lrwxrwxrwx 1 root root 13 Jul 14 15:45 pci-0000:01:00.0-render -> ../renderD128
+lrwxrwxrwx 1 root root  8 Jul 14 15:45 pci-0000:06:00.0-card -> ../card1
+lrwxrwxrwx 1 root root 13 Jul 14 15:45 pci-0000:06:00.0-render -> ../renderD129
+```
+
+So from the above outputs, we can match the bus IDs and determine that NVIDIA is
+`card0` and AMD is `card1`.
+
+# Telling Hyprland which GPU to use
+
+After determining which "card" belongs to which GPU, we now have to tell
+Hyprland the GPU we want to use primarily.
+
+{{< hint type=info >}}
+
+It is generally a good idea for laptops to use the integrated GPU as the primary
+renderer as this preserves battery life and is practically indistinguishable
+from using the dedicated GPU on modern systems in most cases. Hyprland can be
+run on integrated GPUs just fine. The same principle applies for desktop setups
+with a lower and higher power rating GPUs respectively.
+
+{{< /hint >}}
+
+We can do so by using the `WLR_DRM_DEVICES` variable.
+
+Add the following template to `hyprland.conf`
+
+```ini
+env = WLR_DRM_DEVICES,/dev/dri/cardN
+```
+
+For our case, we want to use `card1` primarily and use it to render stuff. 
+
+```ini
+env = WLR_DRM_DEVICES,/dev/dri/card1:/dev/dri/card0
+```
+
+Here, we tell Hyprland to set priorities. If `card1` isn't available for
+whatever reason, use `card0`. So if the AMD GPU isn't available, use NVIDIA. The
+colon is for setting priorities, essentially.
+
+You should now be able to use an integrated GPU for for lighter GPU loads,
+including Hyprland.