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edoreshef
04-23-2014, 12:45 PM
Dear Gurus,

I'm facing an annoying problem (or is really?) that every call to glDispatchCompute ALLWAYS comes with an annoying overhead of about 0.2ms.
Just make it clear: Even executing a “glDispatchCompute(0,0,0)” call on an EMPTY shader cost 0.2ms.

Questions:
Does this make sense?
Is it NVIDIA only issue?
Is there a way around this?


*Note1: The 0.2ms is measured using “glBeginQuery(GL_TIME_ELAPSED,...)“
*Note2: Platform is GTX-560, Windows 7, Latest NVIDIA drivers.

Thanks guys!

inutard
05-12-2014, 04:55 AM
I am also having this issue. I get the exact same delay ~0.2ms when measuring with glBeginQuery(GL_TIME_ELAPSED, ...).

For reference, I am on Windows 7 with GTX-470 on the latest drivers.

Could someone shed some light on this?

EDIT: I have just tried the same thing on a GTX-780 and the delay disappeared. I guess the delay was something only present in 560 and below?