[Wayland-bugs] [Bug 106736] With Vsync disabled, Weston almost halves *visible* frame update rate, compared to X desktop

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=106736

--- Comment #12 from Eero Tamminen <eero.t.tamminen at intel.com> ---
(In reply to Daniel Stone from comment #8)
> (In reply to Eero Tamminen from comment #7)
> > I wasn't able to reproduce the problem with simple-egl test, e.g. with:
> >   weston-simple-egl -b -o -u 15000
> > 
> > But that doesn't seem to use *SwapBuffers().
> > 
> > I'm not sure whether SwapBuffers() is the only reason why it doesn't trigger
> > the issue.  Maybe the test-case actually need to also fully use GPU, for
> > this issue to be visible.
> 
> It certainly does call eglSwapBuffers:
> https://gitlab.freedesktop.org/wayland/weston/blob/master/clients/simple-egl.
> c#L568

I see. I need to track eglSwapBuffersWithDamageEXT() instead.  Thanks!

(eglSwapBuffers() is called exactly 3 times, and only on startup.)


> > Just increase the window size W & H parameters until reported FPS is
> > somewhere between 70-100 FPS.
> 
> So presumably it's running with eglSwapInterval(0) which doesn't block on
> frame callbacks at all?

All gfx performance benchmarks run (by default) with Vsync disabled.  They
cannot measure performance differences if they're limited by Vsync. :-)


> > -> I assume in that particular case, compositor would also require higher
> > GPU priority than the test.  Setting priorities is fairly new Mesa (and i915
> > kernel module) feature.
> 
> We do use it:
> https://gitlab.freedesktop.org/wayland/weston/commit/
> b678befb6ed055e6c66466505d9195a3cebf8073

Weston logs:
   Failed to obtain a high priority context.

I use latest git version of drm-tip kernel, Mesa, Weston, and weston-launch is
suid root.  What else is needed for context priority setting to succeed?

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