[Vk] GenerateMipMaps slow

[krauthaufen]

I have a Demo rendering things to a texture, then generating mipMaps via IRuntime.GenerateMipMaps and using the mipmapped texture in a fullscreen pass.

In OpenGl the postprocessing time is about 3ms but in vulkan it's somwhere around 60ms

[hyazinthh]

Are you sure this is due to GenerateMipMaps? I ran some simple Vulkan tests only benchmarking that call:

• 1920x1080: 2.73ms
• 3840x2160: 7.3ms

Not super fast, but not close to your numbers. In Vulkan all those public API calls are CPU synced, maybe that's your bottleneck?

[krauthaufen]

I'll check that again, maybe my sampling shader was slow for some reason...

Badically i did two things:

1. GenerateMipMap
2. Render a FullScreenQuad with a rather expensive FragmentShader

But I didn't expect my shader to be so much slower