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. In theory it can strike at any time (although userspace has a similar approach to try and not tempt fate). And other than a getparm "bug fixed", there won't be an ABI change for userspace to take note of. I have ~237 patches ahead of my "make partial-vma actually work" fix. :| -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
