“aren't truly using a fully shared memory pool” I think with AMD iGPUs I have here (GCN 5.1 and RDNA3 generations) it’s actually unified, at least on Windows 10. The difference between the reserved portion and the rest of the memory is cosmetic.
From Vulkan API POV, the reserved portion has device local and multi instance heap flags, the main heap doesn’t. However, the memory type is identical across all heaps, all of them have device local, host visible and host coherent property flags. And I can confirm VMA library from Vulkan SDK successfully allocates way more device visible memory than the size of that reserved portion.
From Vulkan API POV, the reserved portion has device local and multi instance heap flags, the main heap doesn’t. However, the memory type is identical across all heaps, all of them have device local, host visible and host coherent property flags. And I can confirm VMA library from Vulkan SDK successfully allocates way more device visible memory than the size of that reserved portion.