[Mesa-dev] [PATCH 0/5] Memory info extensions

[Marek Olšák]

On Wed, Feb 3, 2016 at 11:01 AM, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> On 02.02.2016 14:44, Marek Olšák wrote:
>>
>> Hi,
>>
>> The motivation behind this is to allow games that use proprietary
>> extensions to query the amount of VRAM to be able to query it with Mesa too.
>> Such games are unlikely to use GLX_MESA_query_renderer in the foreseeable
>> feature.
>>
>> Unreal Engine 3 does use one of these. Despite that, it doesn't help. UE3
>> is unable to use advanced graphics and increase its GPU memory pool size
>> even with these extensions.
>>
>> Anyway, I'd like to merge this.
>>
>> I don't plan to add a piglit, but I have a patch which adds support for
>> both extensions to glxinfo.
>
>
> Out of curiosity, which one of these does UE3 use?
>
> The ATI extension part looks fine to me. I hope we don't run into problems
> where we end up reporting more aggressive availability than other drivers
> and then tempt applications into a behavior that triggers buffer swapping,
> but it seems like an acceptable risk.
>
> The NV extension reports eviction counts, and I wonder if we might do more
> harm than good with an implementation that always reports 0 and misleads
> applications into thinking all is fine when they're really swapping buffers
> like hell.

The ATI extension can't return the total memory size, so the NV
extension is better in this regard.

I guess we can return a non-zero eviction size/count based on the
num-bytes-moved kernel query.

Marek