Too many Xeon cores to register?

[bkirch]

We have an interesting problem. We just got new workstations with 2x Xeon 18 core CPUs, giving us 36 total cores and 72 available threads. I was salivating in anticipation of firing up V-Ray for the first time on this new rig and witnessing 72 render buckets working simultaneously! But as it were, it rendered with only one of the CPUs with 36 total threads. The other CPU was not being utilized at all. Kinda funny/sad that we have so much render power but can only utilize half of it.

I am paraphrasing here from a co-worker's findings, but after some quick research he found that there is an issue recognizing more than 64 threads on Windows. If more than 64 threads are present only one CPU will register. We're not sure if this is a limitation of Windows of itself? Or a limitation of Maya? Or V-Ray / MR? All of the above?

Thoughts?

Full specs below:
HP Z840
Windows 10 Pro
Intel Xeon CPU E5-2699 v3 @ 2.3GHz (2 procs, 18 cores each)
128 GB RAM
Nvidia Quadro M6000
Maya 2015/2016*
V-Ray 3.4


Thanks,
-Brian

[glorybound]

I had the same problem, however, the forum helped me through it. It's a variable thing. Maybe, search to find the thread when I was working through it.

[glorybound]

Here is the thread

http://forums.chaosgroup.com/showthr...=cores+threads

[Morbid Angel]

you need to have a very recent vray for maya build. Then in your maya.env you need to input this:

VRAY_USE_THREAD_AFFINITY=1

[bkirch]

Thanks very much guys, were going to try this out next week.

[vlado]

This variable will only work for V-Ray standalone right now. One of the guys already implemented it when rendering inside Maya and it will go into the nightly builds maybe next week.

Best regards,
Vlado

[Morbid Angel]

This variable will only work for V-Ray standalone right now. One of the guys already implemented it when rendering inside Maya and it will go into the nightly builds maybe next week.

Best regards,
Vlado

You see what I mean when I said "very recent build"

(I'm a time traveler)

[bkirch]

Thanks for the update, Vlado. If it's not implemented yet, that's fine, but here is something interesting, I just tried this variable adjustment with Maya 2016 VR 3.30.01 and I got 72 render buckets in the frame buffer, but the second cpu was still showing as idle. How is that possible?

[vlado]

Like I said, it's not quite implemented for rendering inside Maya.

Best regards,
Vlado

[bkirch]

Good news, the latest nightly build fixed the issue (3.45.01) and was working in Maya 2016.5 (we didn't see anything about it in the nightly release notes though). There were 72 buckets rendering and all cpu nodes were active during render. One warning, however, was this:

// Warning: V-Ray : Performance loss: number of rendering threads (72) is greater than number of light cache passes (64); some threads will be idle.

Is this a limitation of the light cache engine or there another setting that will address this?

Thanks!
-Brian

[vlado]

For the moment it's a limitation; will fix it.

Best regards,
Vlado