Deprecation of AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED

[Marek Olšák]

Do you have any concern if we also stop using the CPU_ACCESS flag on radeon?

Thanks,
Marek

On Thu, Jun 29, 2017 at 4:51 PM, Christian König
<deathsimple at vodafone.de> wrote:
> 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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>
>
>