Multiple Importance Sampling in World settings = Cycles GPU render fail

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1

Hi All – I’m seeing strange behavior from Blender recently that hopefully someone can shed some light upon…When I enable Multiple Importance Sampling (MIS) in Blender World settings, Cycles GPU rendering fails.

Issue reproduction steps:

  1. Open Blender 2.70 default scene
  2. Switch to Cycles render engine
  3. Switch from CPU to GPU Compute in Scene Render settings
  4. Press Shift-Z – Render of cube works OK
  5. Switch to World settings and check Multiple Importance Sampling under Settings
  6. Press Shift-Z, render fails with the following Console output:

[SUB]CUDA error: Launch failed incuCtxSynchronize()[/SUB]
[SUB]Refer to the Cycles GPU rendering documentation for possible solutions:[/SUB]
[SUB]http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/GPU_Rendering[/SUB]
[SUB]CUDA error: Launch failed incuMemcpyDtoH((uchar*)mem.data_pointer + offset,(CUdeviceptr)((uchar*)mem.device_pointer + offset), size)[/SUB]
[SUB]CUDA error: Launch failed incuMemFree(cuda_device_ptr(mem.device_pointer))[/SUB]
[SUB]CUDA error: Launch failed incuMemFree(cuda_device_ptr(mem.device_pointer))[/SUB]
[SUB]CUDA error: Launch failed incuMemAlloc(&device_pointer, size)[/SUB]
[SUB]CUDA error: Launch failed incuModuleGetGlobal(&cumem, &cubytes, cuModule, name)[/SUB]
[SUB]CUDA error: Launch failed incuMemcpyHtoD(cumem, (void*)&ptr, cubytes)[/SUB]
[SUB]CUDA error: Launch failed incuMemAlloc(&device_pointer, size)[/SUB]
[SUB]CUDA error: Launch failed incuModuleGetGlobal(&cumem, &cubytes, cuModule, name)[/SUB]
[SUB]CUDA error: Launch failed incuMemcpyHtoD(cumem, (void*)&ptr, cubytes)[/SUB]
[SUB]CUDA error: Launch failed incuMemAlloc(&device_pointer, size)[/SUB]
[SUB]CUDA error: Launch failed incuModuleGetGlobal(&cumem, &cubytes, cuModule, name)[/SUB]
[SUB]CUDA error: Launch failed incuMemcpyHtoD(cumem, (void*)&ptr, cubytes)[/SUB]
[SUB]CUDA error: Launch failed incuMemAlloc(&device_pointer, size)[/SUB]
[SUB]CUDA error: Launch failed incuModuleGetGlobal(&cumem, &cubytes, cuModule, name)[/SUB]
[SUB]CUDA error: Launch failed incuMemcpyHtoD(cumem, (void*)&ptr, cubytes)[/SUB]
[SUB]CUDA error: Launch failed incuMemAlloc(&device_pointer, size)[/SUB]
[SUB]CUDA error: Launch failed incuModuleGetGlobal(&cumem, &cubytes, cuModule, name)[/SUB]
[SUB]CUDA error: Launch failed incuMemcpyHtoD(cumem, (void*)&ptr, cubytes)[/SUB]
[SUB]CUDA error: Launch failed incuModuleGetGlobal(&mem, &bytes, cuModule, name)[/SUB]
[SUB]CUDA error: Launch failed incuMemcpyHtoD(mem, host, size)[/SUB]

If I swap steps 5 and 4 above (perform first render with MIS World setting enabled), GPU render works OK.I’m willing to raise a bug in the tracker but I would like for someone to confirm that this IS a bug so I don’t waste anybody’s time.

My system configuration:
Blender 2.70 64 bit (I’m seeing the same on 2.69)
Windows 8.1 64 bit
NVIDIA GeForce GTX Titan x 3 (SLI is disabled)
NVIDIA Driver 335.23 (latest as of this post)

ANY insight is greatly appreciated.

2

Strange… I get the same error if I enable 3 graphics cards. If I go with 2 GPUs the error is gone… (no error if I go with just one GPU either)

3

cegaton - I’m relieved to hear it’s not just my system. I do not see the issue either if I enable only one graphics card via User Preferences. The issue appears when Blender is configured for multiple GPUs. What is your OS and driver version?

4

I’m on blender 2.7
Linux Mint 16 64bit
driver version 319.32

5

I found that lowering the map resolution form the default 256, makes The Multiple Importance sample work again with all 3 card enabled. The max size I’ve got is 180…

6

If you use GPU-z. how much ram is each card using?

7

I’m seeing the same, map resolution at 180 or lower allows render with 3 cards selected. 181 or higher produces CUDA error.

During CUDA fail using repro steps above GPU-Z reports video card memory used:
GPU1: 1707 MB
GPU2: 0 MB
GPU3: 0 MB

This is entered into the tracker: https://developer.blender.org/T39459

8

cegaton - Running the repro steps above with SLI enabled produced a hard lockup of my system (first I’ve seen). If you’re feeling curious and don’t mind a potential system reset (after saving work), let me know if you see that also. I’d be impressed if the issue could kill Linux Mint.

9

Sorry, I don’t have the connector for SLI, plus only two of my GPUs are the same kind.
As far as I know SLI is not recommended for blender.

10

how much memory is used when the map resolution is at 180

11

GPU-Z video card memory usage after Control-Z render and MIS Map Resolution at 180:

GPU1 “Memory Used”: 1851 MB
GPU2
“Memory Usage (Dedicated)”: 0 MB
“Memory Usage (Dynamic)”: 703
GPU3:
“Memory Usage (Dedicated)”: 0 MB
“Memory Usage (Dynamic)”: 665 MB

I’m not sure why GPU-Z is displaying memory usage differently (e.g. Used vs Usage Dedicated/Dynamic) for that first card.

cegaton - Correct, SLI slows Cycles. I use it for gaming and enabled it only for troubleshooting.

12

For posterity - This bug appears to have been fixed via duplicate bug https://developer.blender.org/T40228
I’ve tested with BuildBot blender-2.71-b49e6d0-win64.zip and I’m no longer seeing the issue. Props to bug fixing Blender devs.