On Thursday, June 9, 2016 1:34:15 PM PDT Francisco Jerez wrote: > Kenneth Graunke <kenn...@whitecape.org> writes: > > > We'll use this for compute shader thread counts shortly. > > > > Cc: "12.0" <mesa-sta...@lists.freedesktop.org> > > Signed-off-by: Kenneth Graunke <kenn...@whitecape.org> > > --- > > src/mesa/drivers/dri/i965/intel_screen.c | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > I'm not sure whether I want to commit this or not...there still seem to > > be some issues on Haswell. I think this is right, but maybe there are > > just other bugs. > > > Yeah, I believe the formula below should work for the time being until > the kernel is fixed to support the right get-params on Gen7. I wonder > though what should we do on IVB? AFAIK IVB GT2 had two subslices rather > than one, but if you simply multiply the current max_cs_threads value by > the number of subslices you'll go over the total thread count of the > GPU. The current max_cs_threads value for IVB GT2 seems bogus AFAICT, > it's higher than the thread count per subslice (48?) but lower than the > total thread count (96). I wonder if barriers are broken on IVB right > now for large enough workgroup size.
I think the Configurations[IVB] > Device Attributes[IVB] page has incorrect information about Ivybridge GT2. It claims there are 12 EUs and 8 Threads/EU. However, check the "Configurations Overview" page. It claims that IVB GT2 has 16 total EUs. The simulator also indicates that IVB GT2 has 2 subslices (half slices), 8 EUs per half slice, and 8 Threads/EU. This gives us 8 * 8 = 64, which is the value we use now. Ugh. This wouldn't be the first time the documentation's been wrong in this area. I've come to trust the simulator more.
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