[Bf-cycles] split kernel and CUDA

[Sergey Sharybin]

hi,

Lukas Stocker was doing experiments with CUDA split kernel. With the
current design of the split it was taking more VRAM actually, AFAIR.
Hopefully he'll read this mail and reply in more details.

Would be cool to have this front moving forward, but i fear we'll have to
step back and reconsider some things about how split kernel works together
with a regular one.

There are interesting results on the stack memory! I can see number of
spill loads go up tho, did you measure if it gives measurable render time
slowdown? And how messy is the patch i wonder :)

On Tue, May 17, 2016 at 8:47 AM, Stefan Werner <swerner at smithmicro.com>
wrote:

> Hi,
>
> Has anyone experimented with building a split kernel for CUDA? It seems to
> me that this could lift some of the limitations on Nvidia hardware, such as
> the high memory requirements on cards with many CUDA cores or the driver
> time out. I just tried out what happens when I take the shared ShaderData
> (KernelGlobals.sd_input) from the split kernel into the CUDA kernel, as
> opposed to creating separate ShaderData structs on the stack, and it looks
> like it has an impact:
>
> before:
> ptxas info    : Compiling entry function 'kernel_cuda_branched_path_trace'
> for 'sm_50'
> ptxas info    : Function properties for kernel_cuda_branched_path_trace
>     68416 bytes stack frame, 1188 bytes spill stores, 3532 bytes spill
> loads
>
> after:
> ptxas info    : Compiling entry function 'kernel_cuda_branched_path_trace'
> for 'sm_50'
> ptxas info    : Function properties for kernel_cuda_branched_path_trace
>     58976 bytes stack frame, 1256 bytes spill stores, 3676 bytes spill
> loads
>
> -Stefan
>
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-- 
With best regards, Sergey Sharybin
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