On Thu, May 16, 2024 at 8:18 AM Tvrtko Ursulin <tursu...@igalia.com> wrote: > > From: Tvrtko Ursulin <tvrtko.ursu...@igalia.com> > > Reduced re-spin of my previous series after Christian corrected a few > misconceptions that I had. So lets see if what remains makes sense or is still > misguided. > > To summarise, the series address the following two issues: > > * Migration rate limiting does not work, at least not for the common case > where userspace configures VRAM+GTT. It thinks it can stop migration > attempts > by playing with bo->allowed_domains vs bo->preferred domains but, both from > the code, and from empirical experiments, I see that not working at all. > When > both masks are identical fiddling with them achieves nothing. Even when > they > are not identical allowed has a fallback GTT placement which means that > when > over the migration budget ttm_bo_validate with bo->allowed_domains can > cause > migration from GTT to VRAM. > > * Driver thinks it will be re-validating evicted buffers on the next > submission > but it does not for the very common case of VRAM+GTT because it only checks > if current placement is *none* of the preferred placements.
For APUs at least, we should never migrate because GTT and VRAM are both system memory so are effectively equal performance-wise. Maybe this regressed when Christian reworked ttm to better handle migrating buffers back to VRAM after suspend on dGPUs? Alex > > These two patches appear to have a positive result for a memory intensive game > like Assassin's Creed Valhalla. On an APU like Steam Deck the game has a > working > set around 5 GiB, while the VRAM is configured to 1 GiB. Correctly respecting > the migration budget appears to keep buffer blits at bay and improves the > minimum frame rate, ie. makes things smoother. > > From the game's built-in benchmark, average of three runs each: > > FPS > migrated KiB min avg max min-1% min-0.1% > because 20784781 10.00 37.00 89.67 22.00 12.33 > patched 4227688 13.67 37.00 81.33 23.33 15.00 > > Disclaimers that I have is that more runs would be needed to be more confident > about the results. And more games. And APU versus discrete. > > Cc: Christian König <christian.koe...@amd.com> > Cc: Friedrich Vock <friedrich.v...@gmx.de> > > Tvrtko Ursulin (2): > drm/amdgpu: Re-validate evicted buffers > drm/amdgpu: Actually respect buffer migration budget > > drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 112 +++++++++++++++++++------ > drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 21 ++++- > 2 files changed, 103 insertions(+), 30 deletions(-) > > -- > 2.44.0 >
