Re: problem with opengl (glxgears) running on cygwin ....

[Jon TURNEY <jon.turney@dronecode.org.uk>]

On 20/03/2014 08:41, Linda Walsh wrote:
> When I try to run glxgears locally, it displays the initial gears,
> but now they are just frozen.  It doesn't work remotely, either,
> which was what I tried initially.  It *used* to work -- remotely
> at 20-30 frames/second (as measured by fraps).
> 
> Interestingly enough, I get a glx window, -- fraps will display
> 30 (the right number for my screen refresh rate), in the right corner
> of the glxgears window... but the gears don't move.
> 
> Same effect happens when I try remotely.  Window comes up with gears
> displayed, but no motion.  Fraps also shows 30 FPS.

Thanks for pointing out this issue.

I think that currently glxgears doesn't work very well with the combination of
indirect rendering and vsync-limited buffer swapping, so you are getting 30
fps, but they aren't useful frames.

Since [1], glxgears turns at a constant 70 degrees per second.

glxSwapBuffers does not block when used with indirect rendering, which means
that lots of frames can be rendered almost instantly, with no apparent
rotation, since the elapsed time between frames is very small.

glxgears is a very basic test that GLX is functioning, and definitely not a
benchmark.  Real GLX clients should have a better mechanism for ensuring their
animation rate doesn't outrun the vsync frequency.

If you have any problems with real GLX clients, I would be interested to hear
them.

[1]
http://cgit.freedesktop.org/mesa/demos/commit/src/xdemos/glxgears.c?id=0b19fb0a5c6299baf28e26625e39773846f815b2

> When I try remote display, the above is pretty much the same except
> I get an error on the client system that it can't load the 3d swrast.so
> driver on the other end.

There is some problem with loading the swrast_dri.so renderer on the remote
system, so it is falling back to indirect rendering.

What is the OS of the remote system?

> But it sees pretty much the same capabilities -- FWIW, there is next to zilch
> network traffic happening when I try this.. I mean while it is happening.
> 
> Before and after ~ 200-400KB/s (xosview), during, all my X windows become
> very slow and no longer refresh steadily. Network throughput registers a drop
> to 1-80KB/s.  Despite that -- xwin pegs a cpu @100% and stays that way
> until I exit glxgears.

I think this is because glxgears will send frames as fast as it can, and can
saturate the X server.

-- 
Jon TURNEY
Volunteer Cygwin/X X Server maintainer

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