[Intel-gfx] Guidance on speed for various GL operations with Intel HW

Peter Clifton pcjc2 at cam.ac.uk
Thu Feb 19 20:36:34 CET 2009

On Thu, 2009-02-19 at 17:42 +0000, Peter Clifton wrote:


> Is there any model of performance to be expected from the various Intel
> GPU pipelines? Any operations which are known to trigger fallbacks, or
> slower rendering? I'm also using XOR operations in GL to draw the
> crosshair - is there any penalty in that?

I have 10-15% time shown to be under mesa_clear when running our
"benchmark" (refreshing as fast as we can), with no graphics primitives
other than the cursor being shown.

The framerate caps at 15fps for drawing two XOR lines! (And the glClear
of the stencil buffer two or three times for each of 10 layers). (This
was running almost full-screen on a 1920x1200 display.

At most, the CPU time is about 5% consumed by pcb, and perhaps another
5-7% on the Xorg server. Nothing in the CPU domain seen by sysprof seems
to be "owning" the time consumed by the GPU.

This would suggest to me that sysprof isn't the correct tool for
profiling a GPU bound problem. I'm fairly hopeful that 20 clears and a
couple of XOR lines won't be maxing out the GPU's capabilities, so I
guess I need to figure out what is stalling.

Any ideas how to profile the GPU, or identify my bottleneck?
Are there any tools for Intel GPUs similar to "perfhud" which I've seen
advertised for NVidia cards?

Peter Clifton

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

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

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