[Intel-gfx] [PATCH] drm/i915: Implement wait-time accounting for i915

[Eric Anholt]

On Sun, 2009-06-21 at 14:49 -0400, Ben Gamari wrote: 
> Implement a mechanism for tracking CPU waits. This will hopefully aid in
> identifying GPU stalls. Likely wait-points are surrounded with a pair
> of I915_BEGIN_WAIT/I915_END_WAIT macros which time the enclosed region,
> crediting the wait to a given wait source. Thanks to ickle for the
> guidance in creating this patch.

So, I'm definitely interested, but I'd like a little more info: Has this
patch been very useful in fixing up lockstepping with the GPU?

It seems like if I was trying to do this (And I've had to debug this
stuff before, where I built a userland implementation of approximately
the same thing), I'd want to know the call stack all the way up into
userland to figure out who was at fault.  So I was thinking that we
might want to be using ftrace or something for capturing forced-wait
information, that could get us stack traces rather than just "waited on
a domain transition for somebody."

-- 
Eric Anholt
eric at anholt.net                         eric.anholt at intel.com


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