Yes, exactly. And if I remember correctly Mesa used to always set GTT as
fallback on APUs, correct?
The problem seems to be that this fallback isn't set for displayable BOs.
So what needs to be done is to just enable this fallback for displayable
BOs as well if the kernel can handle it.
Christian.
Am 20.03.2018 um 00:01 schrieb Marek Olšák:
In theory, Mesa doesn't have to do anything. It can continue setting
VRAM and if the kernel has to put a display buffer into GTT, it
doesn't matter (for Mesa). Whether the VRAM placement is really used
is largely determined by BO priorities.
The way I understand scather/gather is that it only allows the GTT
placement. It doesn't force the GTT placement. Mesa also doesn't force
the GTT placement.
Marek
On Mon, Mar 19, 2018 at 5:12 PM, Alex Deucher <[email protected]
<mailto:[email protected]>> wrote:
On Mon, Mar 19, 2018 at 4:29 PM, Li, Samuel <[email protected]
<mailto:[email protected]>> wrote:
>>to my earlier point, there may be cases where it is advantageous
to put
>> display buffers in vram even if s/g display is supported
>
> Agreed. That is also why the patch has the options to let user
select where
> to put display buffers.
>
> As whether to put the option in Mesa or kernel, it seems the
difference is
> not much. Also, since amdgpufb can request even without mesa,
kernel might
> be a better choice. In addition, putting in the kernel can save
client’s
> duplicate work(mesa, ogl, vulkan, 2d, kernel…)
Why do we even expose different memory pools to the UMDs in the first
place ;) Each pool has performance characteristics that may be
relevant for a particular work load. Only the UMDs really know the
finer points of those workloads. In general, you don't want the kernel
dictating policy if you can avoid it. The kernel exposes
functionality and userspace sets the policy. With the location set in
userspace, each app/user can have whatever policy makes sense for
their use case all at the same time without needing to tweak their
kernel for every use case.
Alex
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