Deprecation of AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED

[Christian König]

Yeah, I was thinking something similar.

See the intention behind CPU_ACCESS_REQUIRED is to always guarantee that 
CPU access is immediately possible.

If you ask me that is not really useful for the UMD and was never meant 
to be used by Mesa (only the closed source UMD and some kernel internal 
use cases).

I would like to keep the behavior in the kernel driver as it is, but we 
should really stop using this as a hint in Mesa.

Regards,
Christian.

Am 29.06.2017 um 16:41 schrieb Marek Olšák:
> Hi,
>
> Given how our memory manager works and the guesswork that UMDs have to
> do to determine whether to set the flag, I think the flag isn't
> useful.
>
> I'm proposing that CPU_ACCESS_REQUIRED:
> - will be deprecated.
> - It will remain to be accepted by the kernel driver, but it will
> either not have any effect, or it will serve as a hint that might or
> might not be followed.
> - The only flag that UMDs are expected to set with regard to CPU
> access is NO_CPU_ACCESS.
>
> The main motivation is the reduction of "virtual" heaps for UMD buffer
> suballocators and reusable buffer pools. A higher number of heaps
> means that more memory can be wasted by UMDs.
>
> Opinions?
>
> Thanks,
> Marek
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