On Tue, Dec 15, 2015 at 12:30:54PM +0000, Chris Wilson wrote: > On Tue, Dec 15, 2015 at 02:01:24PM +0200, Ville Syrjälä wrote: > > On Tue, Dec 15, 2015 at 01:29:59PM +0200, Ville Syrjälä wrote: > > > On Tue, Dec 15, 2015 at 11:16:52AM +0000, Chris Wilson wrote: > > > > On Tue, Dec 15, 2015 at 12:57:15PM +0200, Ville Syrjälä wrote: > > > > > On Tue, Dec 15, 2015 at 09:57:22AM +0000, Chris Wilson wrote: > > > > > > On Tue, Dec 15, 2015 at 11:41:44AM +0200, Ville Syrjälä wrote: > > > > > > > On Mon, Dec 14, 2015 at 08:54:35PM +0000, Chris Wilson wrote: > > > > > > > > On Mon, Dec 14, 2015 at 08:49:38PM +0000, Chris Wilson wrote: > > > > > > > > > On Mon, Dec 14, 2015 at 10:15:53PM +0200, ville.syrjala@xxxxxxxxxxxxxxx wrote: > > > > > > > > > > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > > > > > > > > > > > > > > > > > > > Several factors conspire against us when trying to execute > > > > > > > > > > the tiled small-bo tests: > > > > > > > > > > - pre-gen4 require power of two fences, with natural alignment > > > > > > > > > > - the entire gtt may be mappable > > > > > > > > > > - we put a guard page at the end of gtt > > > > > > > > > > > > > > > > > > > > What all that means is that when we try to use a tiled object half > > > > > > > > > > the size of the mappable area, we can only fit it in the first half > > > > > > > > > > of the gtt. That leads to a SIGBUS when we try to fault in the > > > > > > > > > > object when there's already something (eg. fbdev) occupying the > > > > > > > > > > first half of gtt. > > > > > > > > > > > > > > > > > > > > So in order to make the tests run on old machines, let's further > > > > > > > > > > halve the object size when things look too tight. > > > > > > > > > > > > > > > > > > That defeats the point of the test. The idea is to have the two objects > > > > > > > > > that just don't fit, but only just. > > > > > > > > > > > > > > > > i.e. the test is meant to show that the kernel heuristics for using > > > > > > > > partial vma do not prevent the page-fault-of-doom. > > > > > > > > > > > > > > So just skip then? > > > > > > > > > > > > The kernel has a bug that partial vma was supposed to address. > > > > > > > > > > I'm not sure partial vma has any benefit in this case. Sure, you could > > > > > them mmap the thing but unless we teach the GPU to also use partial > > > > > mappings it won't do any good since we just can't fit the thing into > > > > > the gtt. > > > > > > > > For gen2, not being able to fit into mappable is an issue for the GPU as > > > > well, sure. But for userspace being oblivious and *always* being able to > > > > use mmaping of a bo, it is a big deal. (Being oblivious helps with > > > > robustness in the stack, X/display-server-de-jour should not die just > > > > because of a resource conflict - now X should catch the fault and handle > > > > it, give or take bugs, avoiding that error path entirely is even better.) > > > > > > Yeah, I suppose it would be nice not to SIGBUS even if userspace is > > > trying something a bit crazy. It would just get an error later from > > > execbuf when trying to use the bo with the GPU. So I guess the right > > > fix would be to fall back to partial vma if we fail to bind the full > > > vma. > > > > Hmm, actaully no. This was about tiled objects, and we don't do > > tiled+partial at all currently. Would need to teach the code to do that > > first. > > It's is one and the same fix ;) (Ok, same patchset!) Yeah the problem is that partial views are stuck half-implemented, and seem to not move forward. I'd just skip on gen2/3 tbh. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
