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

[Felix Kuehling]

On 2018-08-24 03:09 PM, Christian König wrote:
> 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.
Oh, I see. I guess my mistake was to assume the PT/PD sizes were powers
of two. With my change they will be.

>
>> 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.
Right. Then I'll go ahead and submit it as is.

Thanks,
  Felix


>
> Regards,
> Christian.
>
>>
>> Regards,
>>    Felix
>
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