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Questions about multi-seat (lemmy.ca)
submitted 10 months ago by to c/linux@lemmy.ml
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With price of PC components getting more expensive I was thinking of experimenting with a multi-seat type setup on my gaming PC. From what I was reading though, multi-seat requires a dedicated GPU for each seat since the compositor is expected to have an exclusive lock on the card.

Does anyone know if you can do a mult-seat like setup with a single GPU? I have a amd 9070 xt so as far as I know the gpu virtualization thing where you split a single physical GPU into multiple virtual GPUs won't work. I was thinking maybe its possible to have a weak secondary GPU just for display, but I don't know if the second seat would be able to still access the more powerful gaming GPU for rendering.

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[–] 5 points 10 months ago

You are probably looking for something like games on whales https://games-on-whales.github.io/. If you have an extra weak gpu or an integrated one besides your 9070xt, you can use that for the video transcoding and the big gpu for the game rendering

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    [–] 2 points 10 months ago* (last edited 10 months ago) (2 children)

    Just to root out the x-y factor, could you elaborate on your goals and how you wish to use it? I think "multi-seat" is a bit of a fuzzy term at this point and perhaps other solutions than what it's typically referring to is more appropriate for your use-case.

    I haven't set up a single-GPU classic multiseat myself but a cursory reading from Debian wiki and Arch wiki Talk say it should be possible. There is mention of Xephyr, which QubesOS is using to do something similar with their "GUI domain". Maybe looking at that can be useful for you.

    Two other things to consider could be VM with PCI-passthrough of the GPU (this does require a second GPU or an APU/iGPU in order to still have graphics on the host OS), or running secondary X servers with TigerVNC that you can then run fullscreen using vncviewer. The latter scales very well on a single GPU and works great for usual desktop/browser/dev but I'd be curious about gaming performance.

    https://doc.qubes-os.org/en/latest/user/advanced-topics/gui-domain.html

    https://doc.qubes-os.org/en/latest/developer/system/gui.html

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  • [–] [S] 1 point 10 months ago (1 child)

    The idea would be two monitors, keyboard, and mice connected to one PC so two people could play games on the same beefy computer at the same time. To avoid issues with steam detecting another instance running, it would be great if the two users were isolated from each other in some way. Also ideally avoiding the need to purchase a second beefy GPU. So PCI-passthrough is out, as you're giving exclusive access to the GPU in the VM (some GPU support virtualization, but my 9070 xt does not). My understanding is that multi-seat as described here for systemd https://wiki.debian.org/Multi_Seat_Debian_HOWTO should be able to do this as you can have two user logged in at the same time, but this require each seat to have its own dedicated GPU for display. The docs from debian seem to suggest the DRI_PRIME may still work to use the other GPU. I am curious if anyone has tried this before and knows if it works I go around buying a cheap secondary GPU.

    VNC seems like an interesting idea, I wonder what the latency would be like for

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  • [–] 1 point 10 months ago*

    Spitballing:

    Depending on how demanding those games are, perhaps they could still be run in VMs, just without physical GPU at all? Then you can passthrough USB controllers or attach USB devices just for the input and audio.

    I guess you probably want third "management monitor" for this where you run virt-manager.

    I'm guessing a "thin client" setup might not make sense here, but otherwise if you have some laptops around to use as "terminals viewers" that could also work I guess. I guess you would just do Steam Link remote play if this is just for Steam gaming though.

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    • [–] 2 points 10 months ago (2 children)

    The uhh a16 I think is four gpu card intended for remote working that would be a natural fit to this. Except that it has no outputs.

    You can do what you’re asking about in x, but I don’t think in Wayland.

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  • [–] [S] 1 point 10 months ago* (last edited 10 months ago) (1 child)

    How do you do it with x? I would be interested in looking at this.

    I think in theory it could be done in Wayland if a compositor implements multi-seat support. There is a fork of wlroots & labwc in this repo that seems like it's trying to do that https://github.com/garlett/multiseat

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  • [–] 1 point 10 months ago

    Typically this is achieved in x11 with x forwarding. Performance won't be great.

    However: you may want to investigate using a hypervisor and a VM for each seat, and a dedicated GPU for each seat. To share GPU between seats, you will need a GPU and motherboard that support sr-iov, which is hard to find, hard to use, and expensive.

    I built a hyper-converged box like this and I can tell you the GPU isn't the obstacle, it's peripherals. Mice, keyboard, video output, that is what people want to be flexible.

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