On Mon, Jun 26, 2017 at 06:44:30PM +0900, Michel Dänzer wrote: > On 24/06/17 02:39 AM, John Brooks wrote: > > The BO move throttling code is designed to allow VRAM to fill quickly if it > > is relatively empty. However, this does not take into account situations > > where the visible VRAM is smaller than total VRAM, and total VRAM may not > > be close to full but the visible VRAM segment is under pressure. In such > > situations, visible VRAM would experience unrestricted swapping and > > performance would drop. > > > > Add a separate counter specifically for moves involving visible VRAM, and > > check it before moving BOs there. > > > > Fixes: 95844d20ae02 (drm/amdgpu: throttle buffer migrations at CS using a fixed MBps limit (v2)) > > Signed-off-by: John Brooks <john at fastquake.com> > > Something like this patch is definitely needed, good catch. > > However, as is one issue is that it incurs CPU overhead even when all of > VRAM is CPU visible. Can that be avoided somehow? > I guess that depends which part of it you consider to be expensive. bytes_moved_vis_threshold isn't used unless visible VRAM is smaller than total VRAM, so any work/instructions that go into computing it could be skipped in that case (at the cost of checking that visible_vram_size < real_vram_size) Would that help? John > > -- > Earthling Michel Dänzer | http://www.amd.com > Libre software enthusiast | Mesa and X developer
