Optimize VM handling a bit more

[Zhang, Jerry (Junwei)]

Apart from Felix comments,

Looks good for me, patch 2 ~ 8 are
Reviewed-by: Junwei Zhang <Jerry.Zhang at amd.com>

Patch 9 ~ 11 are
Acked-by: Junwei Zhang <Jerry.Zhang at amd.com>


On 09/10/2018 02:03 AM, Christian König wrote:
> Hi everyone,
>
> Especially on Vega and Raven VM handling is rather inefficient while creating PTEs because we originally only supported 2 level page tables and implemented 4 level page tables on top of that.
>
> This patch set reworks quite a bit of that handling and adds proper iterator and tree walking functions which are then used to update PTEs more efficiently.
>
> A totally constructed test case which tried to map 2GB of VRAM on an unaligned address is reduced from 45ms down to ~20ms on my test system.
>
> As a very positive side effect this also adds support for 1GB giant VRAM pages additional to the existing 2MB huge pages on Vega/Raven and also enables all additional power of two values (2MB-2GB) for the L1.
>
> This could be beneficial for applications which allocate very huge amounts of memory because it reduces the overhead of page table walks by 50% (huge pages where 25%).
>
> Please comment and/or review,
> Christian.
>
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