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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