[Bf-cycles] still memory problem with cuLaunch on GTX780Ti 3GB with empty scene

Sergey Sharybin sergey.vfx at gmail.com
Wed Sep 16 12:09:14 CEST 2015

Answering where the memory is mainly coming from -- it's coming from
stack memory, which is then being multiplied by the number of threads
of your GPU. It includes both ShaderData structures mentioned above,
but it also includes all those stack variables coming from the
function calls.

Some simplier approaches like feature-aware compilation (like we do
with OpenCL kernels for AMD) with latest CUDA could give some benefits
here, but the only real solution is to finish the split kernel patch
which AMD started a while ago. It shouldn't be THAT hard but some
aspects are to be reconsidered before jumping into there.

On Wed, Sep 16, 2015 at 8:06 AM, Matthew Heimlich
<matt.heimlich at gmail.com> wrote:
> Nope, same thing happens here on Win 7, Lukas.
> On Sep 15, 2015 7:05 PM, "Lukas Stockner" <lukas.stockner at freenet.de> wrote:
>> I noticed on Mint 17.1 that if you ran out of GPU memory before,
>> subsequent renders will sometimes also fail, even if they usually work (like
>> an empty scene). After rebooting or restarting the X server, the same scene
>> works again.
>> I suppose that this is a problem with the memory handling in the
>> proprietary Linux kernel, which would mean it's outside of Cycles'
>> influence.
>> On Di., Sep. 15, 2015 at 2:56 nachm., Thomas Dinges <blender at dingto.org>
>> wrote:
>> This is pretty much a known issue, since day 1 of the experimental kernel.
>> We added the experimental kernel for features such as SSS, which are the
>> cause of the memory peak (or rather SSS enabled as part of our mega kernel).
>> The only real solution here will be the CUDA split kernel. That split
>> might still happen later this year, it's on our todo list.
>> Until then, as Brecht said, use it at your own risk.
>> Am 15.09.2015 um 19:54 schrieb Piotr Arlukowicz:
>> Thank you Brecht, I understand this and that's OK with memory, but...
>> still 1.5GB is not enough even for empty scene... ? Come on! :)
>> I was so desperate that I started to look which GTX should I buy. Surely
>> 980Ti with 6GiB is a great graphics card, but WILL it work?
>> Few months ago Cycles worked in experimental mode just very well and as I
>> don't require it to be bulletproof, this memory lag just kicks me out :(
>> Sorry for sharing personal mood on the list. I hope somebody can advice what
>> to do. Because I don't know if 6GB will be enough, and then there is also
>> Titan with 12GB...
>> regards
>> pio
>> Piotr
>> Arlukowicz, BFCT
>> YT: /user/piotao?feature=guide
>> FB: /polskikursblendera TW: /piotao
>> Blender Network: https://www.blendernetwork.org/piotr-arlukowicz
>> Polski Kurs Blendera: http://polskikursblendera.pl
>> 2015-09-15 18:08 GMT+02:00 Brecht Van Lommel <brechtvanlommel at pandora.be>:
>>> Experimental mode uses significantly more memory. I don't know if this
>>> is more than expected at the moment, but it wouldn't surprise me.
>>> This memory usage is one of the main reasons it's called experimental
>>> mode, if all the features there worked well they would not be called
>>> experimental. I know a lot of users enable this but it's really at
>>> your own risk.
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With best regards, Sergey Sharybin

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