Re: Corruption in glxgears with Compiz

[Peter Clifton <pcjc2@cam.ac.uk>]

On Sat, 2010-10-23 at 18:48 +0100, Chris Wilson wrote:

> We're always eager to improve our code to get the most of our admittedly
> lack-luster GPUs. Even suggests on what tools would be useful or
> improvements we could make to improve profiling/development are most
> welcome.

One thing I was wondering about, was intel_gpu_top. It reports unit
usage based on busy / done registers in the chip. I wondered what would
happen if we polled those registers and graphed them in time... whether
it would show any hints as to which units were waiting on each other,
and where any gaps are.

It would need to be graphical probably, and it would need to be
synchronised in some way to the application / frames being processed, so
all in all, it is rather hard to imagine how it would work with perhaps
unrelated GPU activity going on for other things such as the compositor
and toolkit redrawing.

I sometimes wonder if it is just memory bandwidth constraining things..
perhaps I need to look to the chipset docs and see if there are any
performance diagnostic regs there as well.

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)
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