On Mon, Jun 26, 2017 at 11:27 AM, Michel Dänzer <michel at daenzer.net> wrote: > On 25/06/17 03:00 AM, Christian König wrote: >> Am 23.06.2017 um 19:39 schrieb John Brooks: >>> When the AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED flag is given by >>> userspace, >>> it should only be treated as a hint to initially place a BO somewhere CPU >>> accessible, rather than having a permanent effect on BO placement. >> >> And that is a clear NAK from my side. >> >> CPU_ACCESS_REQUIRED is a permanent limitation to where the buffer should >> be placed. > > It really can't be more than a hint. The userspace driver cannot > reliably know ahead of time whether a BO will be accessed by the CPU at > all, let alone how often. A BO which incorrectly has this flag set > creates artificial pressure on CPU visible VRAM. I also think the flag is only a hint and shouldn't be taken too seriously. Only AMDGPU_GEM_CREATE_NO_CPU_ACCESS has a strict behavior. Marek
