Catastrophic GPU performance in Cycles

Since 2.63 GPU rendering with Cycles has been getting worse all the time. Now hitting the record low.

I have a very simple scene. 3 torus’s and two planes with a simple diffuse materials and a lamp.

Here are the results (viewport rendering):

2.65a passes 10
GPU 29:10s
CPU 14:77s

2.63 passes 10
GPU 08:88s
CPU 12:57s
With GPU Blender goes unresponsive during render.

Is this only me or have others experienced this kind of slowdown? And is there anything to do it?

I have a GTX470 dedicated only for Blender. I have tried bot up- and downgrade drivers. But nothing changes. I also have tried to google a lot for any idea why this happens but nothing useful so far.

The way tiles work changed in recent builds. The setting no longer sets number of tiles, but rather the size of the tiles in pixels. Try 512x512 in the tiles settings, and if your scene can fit the whole image buffer into vRAM try setting tiles to the same values as your render dimensions.

Render times will be slightly slower since MB code was added to trunk, but not like you’re experiencing. Something else is going on.

If using GPU rendering, use larger tiles in Cycles - you’ll get better render times.
When using CPU, use lower sizes for more tiles rendering at once.