On Wed, Mar 21, 2018 at 2:15 PM, Christian König <christian.koenig at amd.com> wrote: > Am 21.03.2018 um 19:04 schrieb Marek Olšák: > > On Wed, Mar 21, 2018 at 10:07 AM, Christian König < > christian.koenig at amd.com> wrote: > >> Am 21.03.2018 um 14:57 schrieb Marek Olšák: >> >> On Wed, Mar 21, 2018 at 4:13 AM, Christian König < >> ckoenig.leichtzumerken at gmail.com> wrote: >> >>> Am 21.03.2018 um 06:08 schrieb Marek Olšák: >>> >>> On Tue, Mar 20, 2018 at 4:16 PM, Christian König < >>> christian.koenig at amd.com> wrote: >>> >>>> That's what I meant with use up the otherwise unused VRAM. I don't see >>>> any disadvantage of always setting GTT as second domain on APUs. >>>> >>>> My assumption was that we dropped this in userspace for displayable >>>> surfaces, but Marek proved that wrong. >>>> >>>> So what we should do is actually to add GTT as fallback to all BOs on >>>> APUs in Mesa and only make sure that the kernel is capable of handling GTT >>>> with optimal performance (e.g. have user huge pages etc..). >>>> >>> >>> VRAM|GTT is practically as good as GTT. VRAM with BO priorities and >>> eviction throttling is the true "VRAM|GTT". >>> >>> I don't know how else to make use of VRAM intelligently. >>> >>> >>> Well why not set VRAM|GTT as default on APUs? That should still save >>> quite a bunch of moves even with throttling. >>> >> >> I explained why: VRAM|GTT is practically as good as GTT. >> >> >>> >>> I mean there really shouldn't be any advantage to use VRAM any more >>> except that we want to use it up as long as it is available. >>> >> >> Why are you suggesting to use VRAM|GTT then? Let's just only use GTT on >> all APUs. >> >> >> Then we don't use the memory stolen for VRAM. >> >> See we want to get to a point where we have any ~16MB of stolen VRAM on >> APUs and everything else in GTT. >> >> But we still have to support cases where we have 1GB stolen VRAM, and >> wasting those 1GB would suck a bit. >> > > BO priorities and BO move throttling should take care of optimal VRAM > usage regardless of the VRAM size. We can adjust the throttling for small > VRAM, but that's about all we can do. > > > Well at least on APUs move throttling is complete nonsense. VRAM should > expose the same performance as GTT. > > So the only usage we have for VRAM is for special cases like page tables > and to allow to actually use the stolen memory. > > VRAM|GTT doesn't guarantee that VRAM will be used usefully. In fact, it > doesn't guarantee anything about VRAM. > > > Why not? VRAM|GTT means that we should use VRAM as long as it is available > and if it is used up fallback to GTT. > > When BOs are evicted from VRAM they are never moved back into it. As far > as I can see that is exactly what we need on APUs. > I see. You don't want to use VRAM usefully. You just want to fill it up with something (anything) so that it's not unused. Marek -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://lists.freedesktop.org/archives/amd-gfx/attachments/20180321/146d9358/attachment.html>
