GPU not properly utilized

[Asdow]

Issue

A fairly simple but nontrivial scene doesn't render properly when device is set to GPU. GPU utilization never goes past 1-3 % On CPU the render takes ~1 min 30 s, but with only GPU selected I had to cancel the render at the 14 min 39 s mark with only the starting tile rendered so far.

Steps to Reproduce

See the attached scene. The only steps needed should be to select either CPU or GPU, render and compare the performance.

System Setup (Environment)

Windows 10 Pro Build 19044 Ryzen 3950x Radeon 5700XT, Driver Version: 21.40.11.03-211201a-374383E-RadeonSoftware Blender 3.0 Prorender v3.3.9

Detailed Description

RPR.zip

[ARozghon]

sorry, but in your shared file textures are missing, can you sent file with packed textures. Please, do this steps: File -> External Data -> Pack Recourses and save file. In current state - all works fine

[Asdow]

Ah, apologies! I knew I should've tested the saved file before submitting it. With the textures added, the filesize goes over github's allowed size so hopefully this mediafire link is okay for you

https://www.mediafire.com/file/vzdh1zkr3b3adng/RPR.7z/file

[Asdow]

So I tracked this down to the material texture sizes, though it is still very odd to me. I've prepared a new minimal scene which should be able to replicate the issue. When the sweater's diffuse or normal texture size is 4096 or larger, GPU rendering is abysmally slow compared to CPU. The scene contains several different sized versions of the textures and is currently set to 2048x2048 size, with it, gpu renders the scene ~13s vs 27s for CPU. With larger texture sizes, the GPU rendering time increases exponentially while CPU rendering is affected much less.

https://www.mediafire.com/file/qi1sh9hqhc1l7eh/RPRPython_imported_shaders_simplified.7z/file