very slow performance of glxgears (68 fps)

Martin Olsson mnemo at
Wed Feb 18 10:12:59 PST 2009

McDonald, Michael-p7438c wrote:
>>> Well whatever we call, it's no longer useful for sanity checking if
>>> it's limited to 60fps  :-)
>> Heh.  This means you can tell we're finally dealing with vertical
>> retrace in a sane way, so others may disagree ;-).
>>                         - Jim
> Dumb question: Do LCD/Plasma/OLED/... Actually have vertical retrace?
> Does the vblank interval approach 0?

The longer decay time (the time it takes to change the color of a pixel)
on LCD's allows for lower vsync rate but as long as the monitor is connected
using a cable the length of the cable, or actually its capacitance will affect
what can be considered a "sane" vsync rate. But I took computing science so
I really have no idea what that means :-)

FWIW, you can choose if you want mesa opengl apps to slow down to draw
only at vsync rate (use /etc/drirc or ~/.drirc) and some apps (like compiz)
even give the the option to configure this in preferences.

Finally, sync_to_vblank or not, if someone wants a better benchmark than
glxgears, then one option is to look into the phoronix test suite:


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