Re: Vsync causes stuttering in various games regardless of uncapped performance [Solved]

[flavonol <plant.chemical@protonmail.com>]

Anssi Saari's recommendation led me to learn a number of interesting things about vertical sync and framerate that I would like to share. I also found solutions that seem to be working well so far in Rise of the Tomb Raider and Team Fortress 2.

One of the things that I found out was that mesa has a built-in way to prevent tearing. It effectively uses the MAILBOX present mode (see https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VkPresentModeKHR.html) for applications that would otherwise produce tearing (see https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8197). This leads to what was, to me, the suprising result of disabling in-game Vsync: the reported frame rate may exceed my display's maximum refresh rate, but tearing is not observed. Stuttering is reduced compared to when I had in-game vertical sync enabled.

I also learned that while the code to enable variable refresh rate in GNOME exists, it has yet to be merged (see https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1154). Therefore, for the time being, I won't be relying on that to keep my gameplay experience smooth.

While it's nice to have tear-free gameplay thanks to MAILBOX present mode, I would still like to have the other benefit of enabling in-game vertical sync, which is the framerate cap. Limiting framerate can reduce power consumption and coil whine. Thankfully, I can use MangoHud to acheive this. As a nice bonus, it can also display & record frametimes. I have been unsuccessful so far at using MangoHud with Team Fortress 2, but libstrangle (see https://gitlab.com/torkel104/libstrangle) did work for applying a framerate cap.

MangoHud & libstrangle can even force MAILBOX present mode, so even if the default behavior of mesa changes, I should be covered, at least for Vulkan games. Curiously, the forced MAILBOX present mode seems to apply to Team Fortress 2 despite it being an OpenGL game, but that's a question for another thread.

TL;DR: Mesa doesn't (currently) allow tearing to happen under Wayland, so one can simply disable in-game vertical sync and optionally cap the framerate with a tool like MangoHud. Framerate limits higher than the display's max refresh rate work best for me.