[pull] amdgpu/kfd, radeon, ttm drm-next-5.5

Koenig, Christian Christian.Koenig at amd.com
Thu Oct 10 14:37:34 UTC 2019

Am 10.10.19 um 16:34 schrieb Alex Deucher:
> AOn Thu, Oct 10, 2019 at 5:54 AM Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
>> On Thu, Oct 10, 2019 at 6:17 AM Alex Deucher <alexdeucher at gmail.com> wrote:
>>> [SNIP]
>>> Christian K├Ânig (22):
>>>        drm/amdgpu: use moving fence instead of exclusive for VM updates
>>>        drm/amdgpu: reserve at least 4MB of VRAM for page tables v2
>>>        drm/amdgpu: remove amdgpu_cs_try_evict
>> Patch no handy for a direct reply, so asking here (but this is totally
>> unrelated to the pull):
>> Do you have other stuff than scanout and pagetables that need to be in
>> vram? I was kinda assume this is needed for big vram-only objects to
>> fit, making space by throwing stuff out that could also be put into
>> system memory. But sounds like it was only for making pagetables fit.
> Yes, basically making page tables fit.  If you push a bunch of stuff
> to system ram, your page table requirements go up too.  See the
> discussion here:
> https://www.spinics.net/lists/amd-gfx/msg38640.html

Yeah, typical chicken and egg problem.

When you evict things to system memory because you don't have enough 
VRAM you need more VRAM for page tables so you need to evict even more 
things to system memory....

Additional to that we have a few other cases where we really need VRAM 
for correct operation (firmware, old MM engines etc...), but nothing 
major like page tables.


> Alex
>> -Daniel

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