[Mesa-dev] [PATCH] st/nine: Disable NV path, it's broken right now.

[Marek Olšák]

On Fri, Aug 21, 2015 at 9:59 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> On Fri, Aug 21, 2015 at 3:54 PM, Axel Davy <axel.davy at ens.fr> wrote:
>> This patch is the result of several discussions on our irc channels.
>>
>> I amended the commit message to:
>>
>> st/nine: Always use user constant buffers
>>
>> We had several reports of users hitting bugs
>> with the other path to upload constants,
>> and switching to the user constant buffer
>> path solves the bugs.
>>
>> User constant buffers are expected to be slower
>> for Nvidia cards, so ideally this patch should be
>> reverted when the path is fixed.
>
> Just for the record:
>
> User constant buffers will never be fast on NVIDIA hardware. They will
> always be at best what you can do in the st, but often worse since you
> have more info about what changed in the st that is not passed down to
> the driver.

FWIW, I wouldn't mind having partial updates of user constant buffers.
This can be accomplished by passing a (huge) bitmask to drivers saying
which vec4s need to be re-uploaded. A bitmask consisting of 10
uint32_t elements should be enough for everybody.

Marek