[Mesa-dev] Discussion: C++11 std::future in Mesa

[⚛]

On Wed, Jun 1, 2016 at 7:07 PM, Marek Olšák <maraeo at gmail.com> wrote:
> On Wed, Jun 1, 2016 at 6:06 PM, ⚛ <0xe2.0x9a.0x9b at gmail.com> wrote:
>> On Wed, Jun 1, 2016 at 3:53 PM, Marek Olšák <maraeo at gmail.com> wrote:
>>> Because of external factors you can't predict, your driver suddenly
>>> receives a bunch of shaders that take 2000 ms to compile right before
>>> a draw call. Your budget is 16 ms per frame to get 30 fps, but you
>>> can't render the frame if you don't compile those shaders. The problem
>>> is how to fit the compilation that takes 2000 ms and is required
>>> render the frame into 16 ms. Can you see where I'm going?
>>
>> I don't understand why transforming parts of shader compilation into
>> asynchronous code isn't the right way to go. Async parts of
>> compilation can potentially run on other CPU cores, maybe lowering
>> those 2000ms down to 750ms.
>
> No. Shader compilation can only be asynchronous if it's far enough
> from a draw call and the app doesn't query its status. If it's next to
> a draw call, multithreading is useless. Completely useless.
>
> We need to get below 33 ms for all shaders needed to be compiled to
> render a frame. If there are 10 VS and 10 PS, one shader must be
> compiled within 1.65 ms on average. I don't see where your random
> guess meets that goal.

Ok, now I understand where the primary problem is: I am at least
several years ahead of you in this.

I apologize for the confusion. I won't happen again. I am leaving this
mailing list.

Farewell.