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Single-GPU Multi-Seat Support With X.Org Under Xephyr

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  • Single-GPU Multi-Seat Support With X.Org Under Xephyr

    Phoronix: Single-GPU Multi-Seat Support With X.Org Under Xephyr

    A patch series that's been baking for a while by La?rcio de Sousa provides Xephyr input hot-plugging and other changes needed to allow for single-GPU multi-seat support...

    http://www.phoronix.com/scan.php?pag...GPU-Multi-Seat

  • #2
    Judging by the email address, the works for the S?o Paulo state government... Nice to see governments supporting FOSS.
    I don't get all this multiseat stuff, though... This was not possible before? Also, what's the advantage over, say, virtual machines?

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    • #3
      Originally posted by asdfblah View Post
      I don't get all this multiseat stuff, though... This was not possible before? Also, what's the advantage over, say, virtual machines?
      Multiseat, when done properly, has a lot of benefits over a VM. The main benefits are:
      * Immensely less disk consumption
      * Immensely less RAM consumption
      * Everything runs at bare-metal
      * Full GPU acceleration for each user
      * No need for virtualization instructions
      * Less maintenance
      * If you have licensed software, you can get away with having only 1 instance installed

      I think KVM has a lot of the same benefits, but most VMs don't.

      The nice thing about multi-seat is you can save a lot of money. It's cheaper to build 1 powerful computer than 2 weaker ones. Then, as long as 1 user isn't active, you can harness that extra processing power for your own needs.

      Unfortunately, xephyr was never really that good. It's slow and doesn't have full hardware acceleration.

      Comment


      • #4
        Originally posted by asdfblah View Post
        ...
        I don't get all this multiseat stuff, though... This was not possible before? Also, what's the advantage over, say, virtual machines?
        This is all about the Desktop/Workplace side of virtualization. This is somewhat orthogonal to e.g. VDI (Virtual Desktop Infrastructure) like Thin Clients, each accessing one of several desktop sessions running somewhere in the datacenter.

        Multiseat means you have one physical machine with multiple monitors, keyboards, mice ... Each seat comprises at least one monitor and keyboard/mouse*.

        Normally, you have one graphics card per seat. Laercios patch enables (more exactly: simplifies the setup) using the multiple outputs of a single graphics card for multiple seats. As you can only run a single X server per GPU (I think for modern linux, the correct term would be KMS device node) single GPU multiseat starts one normal X server, and then in turn starts multiple Xephyr servers, one per seat. The Xephyrs are clients to the normal X server accessing the GPU, but servers to the user session running per seat.

        You can mix and match Terminal Servers, Thin Client Terminals and Multiseat Terminals.


        * You can have multiple monitors per seat. You can have multiple mice/touchpads/touchscreens. Sometimes you dont need a keyboard. Depends on your needs. You get it.

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        • #5
          Originally posted by schmidtbag View Post
          Multiseat, when done properly, has a lot of benefits over a VM. The main benefits are:
          * Immensely less disk consumption
          * Immensely less RAM consumption
          * Everything runs at bare-metal
          * Full GPU acceleration for each user
          * No need for virtualization instructions
          * Less maintenance
          * If you have licensed software, you can get away with having only 1 instance installed

          I think KVM has a lot of the same benefits, but most VMs don't.

          The nice thing about multi-seat is you can save a lot of money. It's cheaper to build 1 powerful computer than 2 weaker ones. Then, as long as 1 user isn't active, you can harness that extra processing power for your own needs.

          Unfortunately, xephyr was never really that good. It's slow and doesn't have full hardware acceleration.
          not if same image to boot
          http://en.wikipedia.org/wiki/Kernel_same-page_merging
          http://www.phoronix.com/scan.php?pag...lization&num=2

          rest is subjective

          others can/do use KVM

          Comment


          • #6
            Originally posted by schmidtbag View Post
            * Full GPU acceleration for each user
            Are you sure it's a case for Xephyr?
            As far as I aware it's doesn't support things like PRIME so you can't use 3D acceleration there.

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            • #7
              Originally posted by gens View Post
              not if same image to boot
              KSM is no silver bullet and it'll increase the need for CPU resources

              Originally posted by gens View Post
              rest is subjective
              All very objective there. Tell me how you're going to run a multi-seat PC with 2+ users on KVM on a cheap dual-core PC with 2GB of RAM, no VT-x instructions. That's what people are doing with multi-seat in developing countries.

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              • #8
                Originally posted by SXX⁣ View Post
                Are you sure it's a case for Xephyr?
                As far as I aware it's doesn't support things like PRIME so you can't use 3D acceleration there.
                I wasn't sure about this either but I'll maybe give it a try. It just so happens that I was thinking about this problem, and Xephyr in particular, just the other day when my daughter wanted to play BIT.TRIP RUNNER on the TV with a gamepad and this was preventing me from doing anything on my main monitor because mouse focus appears to be king, at least under XFCE.

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                • #9
                  Wayland

                  Does Wayland have single-GPU multi-seat support?

                  Comment


                  • #10
                    Originally posted by SXX⁣ View Post
                    Are you sure it's a case for Xephyr?
                    As far as I aware it's doesn't support things like PRIME so you can't use 3D acceleration there.
                    As I said in my post, Xephyr doesn't have full hardware acceleration. Xephyr is really only good as a sandbox for another login - otherwise, it's overall a pretty lacking program. You CAN get 3D rendering to work in xephyr, using things like virtualGL, but it isn't a smooth experience. Besides, the point of xephyr is to be able to run an x session within an x session, which isn't the most practical thing when you want multi-seat.

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