[PATCH] drm/amdgpu: Adjust the VM size based on system memory size v2

[Christian König]

Am 24.08.2018 um 20:59 schrieb Felix Kuehling:
> On 2018-08-24 03:32 AM, Christian König wrote:
>> The roundup to a power of two here is not 100% correct, but I don't
>> think it will hurt us much.
>>
>> For now the patch is Reviewed-by: Christian König
>> <christian.koenig at amd.com>.
> Thanks. Do you mind elaborating on what's not 100% correct here?

Well it's not a power of two what give optimal root PD sizes.

IIRC the optimal configuration for different vm sizes are:
1GB:    4k/4k
2GB:    8k/4k or 4k/8k
4GB:    8k/8k
6GB:    12K/8k
8GB:    16K/8k or 8k/16k
12GB:    12k/16k
....

As you can see 6GB and 12GB are still using all the allocated PD, but 
are not power of two.

> Maybe do the min(..., max_size) after roundup_pow_of_two?

We would need to increase the vm_size based on the PD size after 
figuring out all the parameters.

But the win is probably not worth the effort.

Regards,
Christian.

>
> Regards,
>    Felix