Dual GPU not usable in 3D Viewport preview and processive finale rendering #44273

New Issue

claas eicke · 2015-04-05T01:43:08+02:00

claas eicke commented

2015-04-05 01:43:08 +02:00

System Information
MacPro OS X 10.10.2
2 x MSI GTX 970

Blender Version
2.74

Short description of error
Selected dual GTX 970 CUDA rendering only works when doing a normal finale rendering, each GPU working on a tile.
In finale rendering progressive and in 3D viewport rendering there is no speed gain at all.
Actually the 3D viewport rendering is then a tick slower.

As far as I know you should be able to render with two GPUs even in 3D viewport preview.

**System Information** MacPro OS X 10.10.2 2 x MSI GTX 970 **Blender Version** 2.74 **Short description of error** Selected dual GTX 970 CUDA rendering only works when doing a normal finale rendering, each GPU working on a tile. In finale rendering progressive and in 3D viewport rendering there is no speed gain at all. Actually the 3D viewport rendering is then a tick slower. As far as I know you should be able to render with two GPUs even in 3D viewport preview.

claas eicke commented

2015-04-05 01:43:08 +02:00

Changed status to: 'Open'

claas eicke commented

2015-04-05 01:43:08 +02:00

Added subscriber: @ClaasKuhnen

Sergey Sharybin commented

2015-04-05 14:29:38 +02:00

Added subscriber: @Sergey

Sergey Sharybin commented

2015-04-05 14:29:38 +02:00

Non-progressive final render does dynamic scheduling of tiles to compute devices, but progressive and viewport rendering slices image horizontally into equal parts and each device does tile work inside those slices. This is needed to guarantee tile is getting rendered by the same exact device for each sample. So if your scene is not equally complex on all slices using multiple GPUs indeed will not show much benefits.

But i'm not sure it's indeed the case for you because there's no files attached which shows the issue (which is actually requested in the bug report submission ;)

So not saying there's no bugs here, but you might just be hitting a known TODO and for further investigation we need to have demo file.

Non-progressive final render does dynamic scheduling of tiles to compute devices, but progressive and viewport rendering slices image horizontally into equal parts and each device does tile work inside those slices. This is needed to guarantee tile is getting rendered by the same exact device for each sample. So if your scene is not equally complex on all slices using multiple GPUs indeed will not show much benefits. But i'm not sure it's indeed the case for you because there's no files attached which shows the issue (which is actually requested in the bug report submission ;) So not saying there's no bugs here, but you might just be hitting a known TODO and for further investigation we need to have demo file.

claas eicke commented

2015-04-05 16:14:15 +02:00

Let me supply you with a demo file. I asumed that with a scene that renders slow on a GTX 970 with two at least in preview mode it would render somewhat faster.

Aaron Carlisle commented

2015-04-11 20:30:11 +02:00

Added subscriber: @Blendify

Aaron Carlisle commented

2015-04-11 20:30:11 +02:00

Any news on the demo file this report will be closed tomorrow unless we get a file we could test this with

claas eicke commented

2015-04-13 23:04:04 +02:00

Ok so I did some more testing. I get very odd results.

3D view port is slower with 2 GPUs sometimes, sometimes a tick faster.
I attached a blend file here{F161675}

And the same I also noticed sometimes happening with the progressive render mode for finale image.

Tile rendering most time with 2 gpus is faster.

Ok so I did some more testing. I get very odd results. 3D view port is slower with 2 GPUs sometimes, sometimes a tick faster. I attached a blend file here{[F161675](https://archive.blender.org/developer/F161675/Beachstone_Children.blend.zip)} And the same I also noticed sometimes happening with the progressive render mode for finale image. Tile rendering most time with 2 gpus is faster.

Sergey Sharybin commented

2015-05-12 15:04:12 +02:00

@ClaasKuhnen, one more question: do you have SLI enabled?

claas eicke commented

2015-05-13 06:39:30 +02:00

no - no sli. I was under the assumption that it does not work with SLI.

Sergey Sharybin commented

2015-05-13 09:53:38 +02:00

SLI has negative impact on Cycles performance, that's why was asking. But also so far the slowdown can not be reproduced.

Sergey Sharybin commented

2015-05-25 21:23:19 +02:00

Asked some developers and users in the #blendercoders IRC room and we can not confirm the issue so far, which means it's not really possible to solve it. Moving to unconfirmed projects hoping someone in there will be more lucky.

The issue reported can't be reproduced so far, and has been moved to the BF Blender: Unconfirmed project.
If 2 other people aren't able to redo the bug after 2 weeks, it will be closed.

We appreciate the effort that goes into making bug reports, but to be able to fix bugs we have to be able to redo them.
If there is anything you can provide to help others to reproduce the problem, be sure to include it.

Asked some developers and users in the #blendercoders IRC room and we can not confirm the issue so far, which means it's not really possible to solve it. Moving to unconfirmed projects hoping someone in there will be more lucky. ---- The issue reported can't be reproduced so far, and has been moved to the *BF Blender: Unconfirmed* project. If 2 other people aren't able to redo the bug after 2 weeks, it will be closed. We appreciate the effort that goes into making bug reports, but to be able to fix bugs we have to be able to redo them. If there is anything you can provide to help others to reproduce the problem, be sure to include it.

Carlo Andreacchio commented

2015-05-26 02:55:54 +02:00

Added subscriber: @candreacchio