[Bug 105316] vsync in Vulkan applications doesn't work correctly with both radv and amdvlk

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Fri Mar 2 13:02:04 UTC 2018


--- Comment #4 from tempel.julian at gmail.com ---
Thanks for still responding, despite of the closed ticket.

I can assure you that with OpenGL/RadeonSI in an Xorg session, application's
own vsync really does work correctly without the help of a compositor, even in
windowed mode.

Let's take Firefox as an example:
With "layers.acceleration.force-enabled" in about:config, you can enable OpenGL
rendering of Firefox. With this, e.g. scrolling or the website
www.vsynctester.com is _absolutely_ free of tearing, it's perfectly
synchronized to the display's refreshrate.
I checked this with several desktop environments which allow to disable their
Xorg compositor, such as KDE Plasma or XFCE. It definitely does work without
the help of a compositor.

Would it be an option to suggest that amdvlk/radv explicitly make use of page
flipping instead?

Because using the compositor to deal with vsync is quite unfortunate, it costs
a bit of performance and adds additional input latency by having an own
additional frame buffer queue.
Furthermore, the only compositor which can be configured in detail regarding
unredirecting single applications would be Compton. E.g. Gnome Mutter does
always unredirect in fullscreen, so there would be no way of getting proper
vsync in fullscreen in a Gnome Xorg session.

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