Llama.cpp-vulkan: What's the best strategy to use iGPU alongside dGPU(s)

...without slowing everything to a halt?

Edit: I realize this might not be clear, but I'm refering to the iGPU within a consumer CPU, eg Ryzen 9950x, rather than Halo.

For example, is there a kind of buffer or operation that could be safely and specifically offloaded to iGPU's RAM? And how?