On Thu, Feb 16, 2012 at 03:52:46PM -0800, Eric Anholt wrote: > On Thu, 16 Feb 2012 18:38:08 +0100, Daniel Vetter <daniel at ffwll.ch> wrote: > > On Thu, Feb 16, 2012 at 08:48:07AM -0800, Eric Anholt wrote: > > > On Thu, 16 Feb 2012 13:11:31 +0100, Daniel Vetter <daniel.vetter at ffwll.ch> wrote: > > > > No longer needed. > > > > > > What this code was for: Before gtt mapping, we were doing software > > > fallbacks in Mesa with pread/write on pages at a time (or worse) of the > > > framebuffer. It would regularly result in hitting the same page again, > > > since I was only caching the last page I'd pulled out, instead of > > > keeping a whole copy of the framebuffer during the fallback. > > > > Urgh, that's not really efficient ;-) I think for s/w fallbacks and > > readbacks we can presume decent damage tracking (like sna does) on the > > userspace sides. > > > > > Since we've been doing gtt mapping for years at this point, I'm happy to > > > see the code die. > > > > > > I'm not sure about the rest of the code. In particular, for the code > > > that's switching between gtt and cpu mappings to handle a read/write, > > > I'm concerned about whether the behavior matches for tiled objects. I > > > haven't reviewed enough to be sure. > > > > Behaviour should match old code if you read/write entire pages (we should > > have decent set of tests for that). If you do non-cacheline-aligned > > reads/writes on tiled objects, we might hit an issue, but they should be > > solveable (I've simply been too lazy to write testcases for this). Not > > cacheline aligned reads/writes on untiled also work, I've created a set of > > tests to exercise issues there (and tested the tests by omitting some of > > the clflushes, i.e. all the clfushes now left _are_ required). > > > > If old mesa depends on sub-page reads/writes to tiled objects I need to > > create the respective tests and double-check the code, otherwise I think > > we're covered. Do you want me to adapt the tests to check correctness for > > sub-page reads/writes to tiled objects? > > In the long long ago, I believe we did per-pixel accesses of tiled > objects through pread/pwrite. Crazy, I know. Ok, I'll create a new tests to check partial, unaligned pwrites/preads on tiled objects. On re-reading the patches the thing I'll likely got wrong is that I don't swizzle the clflushing. But if we need to swizzle a page we go through the slow-path anyway (no point in adding optimized code for something no one cares about perf-wise anymore), so there shouldn't be any issues with adding another branch to fix up the flushing. Won't be fast though, but I guess no one cares ;-) Cheers, Daniel -- Daniel Vetter Mail: daniel at ffwll.ch Mobile: +41 (0)79 365 57 48
