On 05/02/2013 06:34 PM, Lauri Kasanen wrote:
On Thu, 02 May 2013 00:45:13 +0400
Vadim Girlin <vadimgir...@gmail.com> wrote:
On 05/01/2013 11:36 PM, Lauri Kasanen wrote:
Now that it built, I could test your optimizations in my own apps.
These are on current master 8eef6ad, on a RV710 (HD 4350 pci-e).
In one of my private apps, using R600_DEBUG=sb caused regressions: FPS
went from 28 to 7, the SSAO shader gave visual distortions/flicker, and
the cpu was constantly pegged.
Here's the output from R600_DEBUG=sb,sbstat in case it helps:
http://bayfiles.net/file/Pmkh/PUj0Ru/vadim.gz
It seems as if it's constantly handling new shaders? My app certainly
issues no new shaders, they are all linked when the app starts.
r600g may rebuild shaders at runtime because some GL features are
implemented in shader code, so if your app changes some specific GL
states (e.g. two-sided rendering mode), then r600g has to build and
switch between different shader variants.
It mainly uses the stencil buffer, the clear color is changed in
various passes, some occlusion queries with color masks, but nothing
exotic. New uniforms are of course sent each frame.
On the other hand there is caching of shader variants in r600g
implemented specially to prevent repetitive rebuilding of shaders, looks
like it doesn't work in your case for some reason. Optimizations take
more time than rebuilding with default backend, that explains
performance regression.
Could you provide some test app that reproduces these issues?
It's quite time-taking to cut it down, and apitraces of it in full are
several gigs (far too much to upload with my connection). I'll see if I
can get just the SSAO isolated, with minimal textures, to get a smaller
trace.
I'm almost sure that the same issue that you have with glxgears affects
your app too, so you might want to wait until we resolve the problem
with gears, possibly this will solve other rendering issues as well.
Please also send me the dump with "R600_DEBUG=sb,ps,vs", maybe I'll be
able to spot anything wrong there.
http://bayfiles.net/file/PmY5/xgIdlZ/foo.gz
Let me know what you need to debug this.
- Lauri
PS: I'm not sure if this should be public or not, I think you're the
only one working on it?
Yes, I doubt that anyone else will work on it, on the other hand I think
reporting this on the list might help other users who will possibly hit
similar issues. Also at least in this case it looks rather like a
problem in r600g, so I'm cc'ing mesa-dev, r600-sb just made this issue
more noticeable because shader rebuilding with optimization requires
more time.
Using standard r600g, the cpu usage is less than 25% of one core, so
nothing was showing it was constantly rebuilding shaders. Is there some
way I could've found it was doing that, and if so, why?
You could run the app with R600_DEBUG=ps,vs (without "sb") - it will
also print the dump of every built shader. r600-sb doesn't affect the
logic of shader rebuilding, it just processes the shaders when asked by
r600g, so I think you'll see the same - a lot of built shaders. You
could even try this with older mesa (before r600-sb was merged) to be sure.
As for the cause of rebuilding, I don't see any changes in the shaders
in your dump that might be explained by state changes, it's exactly the
same shaders rebuilt more than once, so far I don't know why. You might
want to look into r600_shader_select function with debugger to see
what's going wrong, it computes the key for required shader variant
using r600_shader_selector_key, then looks at the list of variants to
find already built shader with the same key, and builds a new one only
if it can't find existing shader. Looks like something fails there.
By the way, I won't be very surprised if some old gcc release simply
fails at handling bitfields which are used to store both the keys of
shader variants in r600g and bytecode data in r600-sb (the same data
that ends up being broken in your glxgears dump), IIRC there were
bitfields-related bugs.
Vadim
- Lauri
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/mesa-dev
