[Intel-gfx] intel_gpu_top profiles

[Eric Anholt]

On Fri, 2009-10-30 at 21:54 +0000, Daniel J Blueman wrote:
> On Fri, Oct 30, 2009 at 6:25 PM, Eric Anholt <eric at anholt.net> wrote:
> > On Fri, 2009-10-30 at 12:29 +0000, Peter Clifton wrote:
> >> Hi guys..
> >>
> >> intel_gpu_top seemed like it has been a well kept secret.. I discovered
> >> it today, and took some profiles of the circuit board layout package I'm
> >> working on.
> >>
> >> Can anyone suggest whether there appears to be "room for improvement"? I
> >> couldn't spot any obvious bottle-neck. I'm surprised that the pixel
> >> shader is seeing any use, (even without compiz), as I'm just using
> >> boring fixed-function stuff with no texturing, no lighting, nothing
> >> fancy..
> >
> > I'd been meaning to type this up for a while, and your mail convinced me
> > to do so.  Here's a new wiki page:
> >
> > http://dri.freedesktop.org/wiki/IntelPerformanceTuning
> >
> > Does this help?  Are there parts that are unclear and confusing?
> >
> >> Screen-captures of the profiles available here:
> >>
> >> http://www2.eng.cam.ac.uk/~pcjc2/geda/intel_gpu_top_profiles/
> >> http://www2.eng.cam.ac.uk/~pcjc2/geda/intel_gpu_top_profiles/intel_gpu_load_displaylist_no_compiz_PCB.png
> >> http://www2.eng.cam.ac.uk/~pcjc2/geda/intel_gpu_top_profiles/intel_gpu_top_displaylist_compiz_PCB.png
> >> http://www2.eng.cam.ac.uk/~pcjc2/geda/intel_gpu_top_profiles/intel_gpu_top_no_displaylist_compiz_PCB.png
> >> http://www2.eng.cam.ac.uk/~pcjc2/geda/intel_gpu_top_profiles/intel_gpu_top_no_displaylist_no_compiz_PCB.png
> >
> > OK, so this shows that the GPU is almost entirely idle, time to pull out
> > perf and see what's going wrong.
> 
> Would any missing write barriers (ie wmb on x86) cause this behaviour,
> eg if GPU commands are written to memory-mapped I/O pages with
> write-combining page flags?

wmb doesn't actually solve that problem for PCI MMIO regions, you need
readback from the device.  And yes, we do that.

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


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