[PATCH 2/6] vkd3d: Implement support for persistently mapped HOST_VISIBLE heaps.

[Hans-Kristian Arntzen]

On 9/30/19 9:40 PM, Henri Verbeet wrote:
> On Mon, 30 Sep 2019 at 17:48, Hans-Kristian Arntzen
> <post at arntzen-software.no> wrote:
>> Greatly reduces number of maps for applications which do not do this
>> themselves. Also add a config option to use older map-on-demand
>> behavior, which might be nice for debugging tools.
>>
> I don't want to just say no, but this does seem to go against the
> spirit of an "explicit" API like d3d12 somewhat. My other concern with
> this is that while on 64-bit we typically have plenty of address
> space, things can be a bit more tight on 32-bit. I assume the main
> justification for this patch is performance; do you have some numbers?
FWIW, I tried this on a native D3D12 and Map/Unmap of single resources 
seems to behave in a very similar way to the existing implementation. 
vkMapMemory is actually faster than ID3D12Resource::Map, so probably 
fine to just drop this patch.

Cheers,
Hans-Kristian