[Mesa-dev] Gallium optimization: add the user pointer into pipe_vertex_buffer and pipe_index_buffer

[Alex Deucher]

On Mon, Apr 16, 2012 at 8:09 AM, Marek Olšák <maraeo at gmail.com> wrote:
> Hi,
>
> does lack of feedback mean that this idea is still off the table
> despite the performance increase, or that nobody is opposed to it
> anymore?
>
> In other words, may I start adapting the other drivers and send patches?

Seems ok to me FWIW.

Alex

>
> Thanks,
> Marek
>
> On Thu, Apr 12, 2012 at 8:08 PM, Marek Olšák <maraeo at gmail.com> wrote:
>> Hi,
>>
>> In parallel with my other work, I have been looking for ways to
>> decrease our draw-call overhead and tried adding the user buffer
>> pointer into pipe_vertex_buffer and pipe_index_buffer, which led to a
>> removal of a lot of code from st_draw.c. With that change, I have
>> tested r300g with torcs and ipers and got surprising results.
>>
>> Pros:
>> - 9% performance increase in torcs (open source game)
>> - 6% performance increase in ipers (from Mesa demos)
>> - Besides that, a little over 110 lines of code was removed from st_draw.c.
>>
>> Cons:
>> - The user buffer contents are fully mutable between draw calls,
>> however drivers should be ready for that now.
>>
>> I know this was brought up long ago and it was NAK'd, but you know,
>> it's really hard to resist this framerate-increasing "cleanup". I
>> guess many people would agree.
>>
>> Here's the proof-of-concept implementation (2 commits):
>> http://cgit.freedesktop.org/~mareko/mesa/commit/?h=gallium-user-ptr-in-states&id=21cf1414df5e24942fe4f0fdab008c9b3bc63802
>> http://cgit.freedesktop.org/~mareko/mesa/commit/?h=gallium-user-ptr-in-states&id=a582f05b56b89e8c2e1345b6c2b6eb9663919eba
>>
>> Here are the exact benchmark results:
>>
>> Torcs before:
>> libGL: FPS = 22.3
>> libGL: FPS = 21.6
>> libGL: FPS = 20.5
>> libGL: FPS = 20.4
>>
>> Torcs after:
>> libGL: FPS = 24.4
>> libGL: FPS = 23.7
>> libGL: FPS = 22.2
>> libGL: FPS = 22.0
>>
>> Ipers before:
>> Frame rate: 30.212976
>> Frame rate: 30.183079
>> Frame rate: 30.183079
>> Frame rate: 30.257936
>>
>> Ipers after:
>> Frame rate: 31.761785
>> Frame rate: 32.000000
>> Frame rate: 32.082922
>> Frame rate: 32.146389
>>
>> Comments welcome.
>>
>> Thanks,
>> Marek
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