On Tue, Nov 24, 2015 at 11:01:25PM +0000, Chris Wilson wrote: > On Tue, Nov 24, 2015 at 07:06:21PM +0100, Daniel Vetter wrote: > > Just setting obj->dirty only works if you also have the pages. > > Exactly. The CPU access has historically always been page-by-page. The > style here more or less to emulate the CPU mmap. > > > But it's also not awesome that set_to_gtt_domain does this for callers. > > Hmm, do you have an example where we want set-to-gtt(write), but not > actually write through the backing storage? Internal use of set-to-gtt > has never been ideal (e.g. context) but we haven't yet come up with a > better semantic. Just the inconsistency that Dave pointed out is a bit worrisome. At most we can fix this with docs (which atm we have), which gives us a rather low score on API design (still a positive one still it's possible to get right). I agree that I don't have better semantics either. > > For lack of clear solutions I'd go with sprinkling obj->dirty or > > page_set_dirty over callers. Aside: relocate_entry_cpu probably gets away > > because of the unconditional obj->dirty we do later on, and that we redo > > all relocs if a fault happens. Still would be good to fix it, just for > > safety. > > [copy_batch() isn't a bug as the contents are invalidated after use > anyway] Just for consistency adding the obj->dirty after get_pages won't hurt though. > relocate_entry_cpu() is a bug we never caught. Indeed we've papered over > it to mask some over userspace issues, but just adding the set_page_dirty() > as required isn't going to be a big hardship. Yeah. > We have tons of swapthrash tests to check persistency of GPU buffers, > but we never tried to thrash the batches themselves out to swap and then > reuse them. > > I guess that it is because userspace doesn't reuse batches that we never > had report of the issue. Hibernating would be a good exercise of such. Hm it's not just batches but any object with relocs. Could this explain the oddball libva/uxa hang? Stuff like "after playing $game for hours my desktop looked funny", but not for tiling issues. -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
