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X.Org Server Adds "Fake Screen FPS" Option

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  • X.Org Server Adds "Fake Screen FPS" Option

    Phoronix: X.Org Server Adds "Fake Screen FPS" Option

    The X.Org Server has picked up a new "-fakescreenfps" option to help with VNC and other remote display scenarios...

    https://www.phoronix.com/scan.php?pa...-fakescreenfps

  • #2
    I am assuming this must be quite driver specific? I have not run into it so far with the following configs.
    • x11vnc - Scrape the screen of a real display (so GPU backed. AMD, monitor unplugged)
    • Xvnc - Stripped down X11 server backed with a virtual framebuffer (not accelerated)
    • Xvfb/x11vnc - Virtual framebuffer being scraped (OpenBSD a while back didn't provide a vncserver in packages)

    I am assuming only the first config would be at risk? Or perhaps this is when using something like Xdummy as part of the VNC backend?

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    • #3
      As the author of the second mentioned change, I would clarify the situation. The change initializes GLAMOR in case there is an Xorg configuration file that says so, even if the main device would be using llvmpipe. The configuration needs to use the GPUDevice option for a iGPU or dGPU output via ZaphodHeads and the Device option would reference the USB DisplayLink or some other dumb framebuffer device. In the default case, i.e. with no configuration file and autodetecting everything, DisplayLink and llvmpipe still doesn't allow GLAMOR to be initialized.

      EDIT: Michael only mentioned the last commit of the MR but there's more to the story in case someone is interested:
      https://gitlab.freedesktop.org/xorg/...e_requests/337
      Last edited by zboszor; 05 August 2021, 12:15 AM.

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      • #4
        Another thing that works in xorg and doesn't work in wayland! But hey xorg gets no development! outside the features we get weekly lol

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        • #5
          "Fuser react first an destroys fused device"

          Pre-recorded message: "Everything is under control. Nothing can go wrong (bum) .. can go wrong .. (bum) .. can go wrong .. (bum) .. can go wrong .. (bum) .. can go wrong .. "

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          • #6
            I have two concerns:

            (1) Why would X waste time drawing at all if there is no screen, even if only once per second? Ideally it should dump the whole framebuffer to save resources and re-create it if/when a screen appears.
            (2) Why doesn't VNC count as a screen? Remote framebuffers shouldn't have to go through a "fake screen" hack, they should be treated like any other display.

            I know it's not worth fixing X at this point, but issues like this show how crufty things have become.

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            • #7
              I use xvnc all the time w llvmpipe. I don't see this issue. But I have seen the 1 sec refresh when trying to use virtual GL / turbovnc. Not sure if it's related.

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              • #8
                Originally posted by ezekrb5 View Post
                Another thing that works in xorg and doesn't work in wayland! But hey xorg gets no development! outside the features we get weekly lol
                I'm sorry, what exactly "works in Xorg and doesn't work in Wayland"?

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