R331 10x slower, crashes, and no debug output. How do you debug this?


I see 10x slowdown in simple DOF shader after updating driver from 320.49 to 331.82.
Customers with various Nvidia GPUs report even worse slowdown (from hundreds to 1fps) and crashes with the most recent driver. Quality settings in control panel have no effect on poor fps.

So the first thing I try is check debug output via glDebugMessageCallbackARB, but the callback is never called. What did happen, is debug output disabled in R331?

What do you use for debugging?

I tried to simplify the shader, but it’s just fixed length for cycle with some texture lookups. It performs well with for cycle length reduced to 1 or 2, but it’s 4x slower if length is 3 and so on, R331 brings unexpectedly sharp drop in performance with more texture lookups.


Funny thing is the shader runs at full speed with Nsight enabled, it’s 10x slower only when not debugging.