To add a little detail, turning on OSL (on the new system) made my rendes about 10% slower.
Sincerely, Karim Hosein Top Rock Photography 754.999.1652 On Mon, 11 Jan 2021 at 16:08, Top Rock Photography < [email protected]> wrote: > My old setup: > AMD Phenom II X6 1055T at 2400 MHz, 32 GiB DDR3 RAM at 1200 MHz, (1600MHz > when SPD works), nVidia GTX 760. Nothing overclocked. GPU render was about > 3× faster than CPU (with or without Open Shading Language, which did not > always work). Nothing over clocked. The GPU is a PCIe 3.0, but the MB is a > PCIe 2.0. > > New setup: > AMD Ryzen 7 3800X, 32 GiB DDR4 RAM at 3200 MHz (with SPD, normally 2400), > same GPU, but now in a PCIe 4.0 MB. Nothing overclocked. (Yes, I replaced > my ten year old MB and CPU, thus had to also get new RAM). > > All else equal. —OS on SATA III SSD, data on 4× HDD RAID5, SATA III, OS > (Ubuntu 20.04 LTS) et al. No surprise, CPU render is now faster than GPU > render. In fact, it is about 3× faster. What I found surprising is that > GPU+CPU render is slower than plain old CPU, and plain old CPU is faster > than CPU with OSL. > > I thought that a car being pushed by four strong guys will go slower than > a car being pushed by four strong guys and one weakling, thus, adding the > slower GPU would still speed up the render. Apparently not. I also recall > on my old system, that GPU+CPU was also slower than just plain GPU. In > other words, the slower guy slows down the faster guy, either way. > > I do not think it was supposed to work that way. > > Second, I thought that OSL accelerated surface/volume scattering when > doing physics-based rendering, (my normal MO). I cannot ever remember > actually timing it on the old system, but I do remember getting the > perception of it taking longer whenever OSL crashed Blender. Very > non-scientific. > > Does using OSL slow us down as a trade-off for better render. or does it > accelerate the system?. Should GPU+CPU be faster than just one or the other? > > Old system was Blender 2.90.1, compiled from source. New system is Blender > 2.91.0, also compiled from source. (I also re-compiled some of the > dependencies after the upgrade to ensure any new available compile options > are used to optimize for the new platform). > > Sincerely, > > Karim Hosein > Top Rock Photography > 754.999.1652 > > ____________________________________________________________________________ darktable user mailing list to unsubscribe send a mail to [email protected]
