[Bf-cycles] possible new open-cl capable driver?

storm kartochka22 at yandex.ru
Wed Feb 8 05:17:28 CET 2012


I am very interested in anything related Cycles GPU render on my AMD
5670, and latest news that AMD work for even better solution, something
like complete C/C++ compiler that will work on GPU, and same time rumors
that unnamed embedded hardware related group pushing OpenCL AMD
developers for free driver support ( maybe it related only for Fusion
APU and not discrete graphics? I hope no.).

Looking at AMD leaked plans we need to wait 2014 year for real GPU, that
will work as NUMA with all transparent access to paged memory, current
GPU cannot directly access same address space as CPU, and worse, they
are cannot preempt, so if you have only one GPU shared for OS GUI and
OpenCL/etc then you always get laggy sluggish experience, and cannot
efficiently share resources between tasks.

That all make Cycles very depend on fast moving target.

For example month ago AMD share first portion of imtermediate OpenCL
compiler, other people have succes in better LLVM support of other
pipeline parts, maybe someone already have full working test setup, who
know, it was quiet since that, and I hope we will see first working
OpenCL solution in next 2 months. I expect poor performance, maybe tiny
part will execute on GPU and rest on CPU, but main direction is clear.

Nvidia have no support for that at all. nouveau is fully reverse
engineered project, and unfortunately that CUDA/OpenCL GPU instructions
are guessed. It very unstable even for usual 2d work, compared to AMD,
and in turn, writing compilers are very complex task, maybe most hard in
IT, and I very doubt that OpenCL on nouveau will be useable in short
time, and even more, Cycles kernel code is huge compared to typical
tasks targeted by GPU users, and very exotic.

All that mean it is nice challenge to make Cycles work on nvidia GPU
hardware using free driver, but too hard compared to basic typical
kernel like FFT or filter, cryprography, and have no advantage to that,
most common part is LLVM compiler and if it can compile small kernel it
can do it for Cycles as well.

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