On 28/03/17 05:29 PM, Christian König wrote: > Am 28.03.2017 um 08:00 schrieb Michel Dänzer: >> On 28/03/17 12:50 PM, zhoucm1 wrote: >>> On 2017å¹´03æ??28æ?¥ 10:40, Michel Dänzer wrote: >>>> On 27/03/17 04:53 PM, Zhou, David(ChunMing) wrote: >>>>> For APU special case, can we prevent eviction happening between VRAM >>>>> <----> GTT? >>>> We can, if we can close the performance gap between VRAM and GTT. We >>>> measured around 30% gap a while ago, though right now I'm only >>>> measuring >>>> ~5%, but the test system has slower RAM now (still dual channel >>>> though). >>> My impression VRAM and GTT have no much difference for APU case, if I'm >>> wrong, pls correct me. >> The Mesa patch below makes radeonsi use mostly GTT instead of mostly >> VRAM, and slows down Unigine Valley by about 5% on my desktop Kaveri. >> You can try it for yourself. > > Additional to that you still need the stolen VRAM on APUs for page > tables and DCE. > > So we need to keep the eviction from VRAM to GTT enabled, but what we > don't do is swapping them back in because Marek added the GTT flags on > APUs as extra domain to look into. As long as there's a performance gap between VRAM and GTT, this means that performance of long-running apps (e.g. Xorg or the compositor) will degrade over time, or after e.g. a suspend-resume cycle. OTOH, if we can close the gap, we can stop trying to put most BOs in VRAM in the first place with APUs. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer
