I’m rendering the default cube scene in 2.8 Beta, with tile size 256*256 for GTX 1080Ti+1070.
Samples 10, 1920 * 1080, full.
Render time is 2.65 sec.
In old Blender it was about 1.5 sec.
Why is Cycles slower in the new 2.8 when they say it is actually faster?
You’re going to have to try a real scene that takes more work to render if you want to see a real comparison. A test that runs in a couple seconds is not going to tell you anything interesting.
fishy_cat for example is generally around twice as fast in 2.8.
Interestingly it’s 8% faster using 32x32 GPU tiles in 2.80 than using 128x128 tiles, even before enabling CPU+GPU rendering which speeds it up even more.
It’s not that easy to find good benchmark scenes that are compatible with both 2.79 and the current 2.80 beta and some of the old benchmark scenes are currently broken in 2.80.
Yes, don’t worry about it. I didn’t do any real benchmark, yet, but I actually have the impression that 2.8 is faster. At least it feels that way.
Otherwise, not surprising that there are corner cases where it isn’t true. Most real-world optimizations don’t make things always faster, only for typical use cases, while for exotic ones they may be slower.
I feel the same. In my benchmark Cycles GPU is around 20% slower. You can find my topic here with a screne file: Slower Cycles GPU in Blender 2.8 Beta