Comment by Retr0id
1 year ago
Something that frustrates me a little is that my system (apple silicon) has unified memory, which in theory should negate the need to shuffle data between CPU and GPU. But, iiuc, the GPU programming APIs at my disposal all require me to pretend the memory is not unified - which makes sense because they want to be portable across different hardware configurations. But it would make my life a lot easier if I could just target the hardware I have, and ignore compatibility concerns.
You can. There are API extensions for persistently mapping memory, and it's up to you to ensure that you never write to a buffer at the same time the GPU is reading from it.
At least for Vulkan/DirectX12. Metal is often weird, I don't know what's available there.
Unified memory doesn't mean unified address space. It frustrates me when no one understands unified memory.
If you fix the pages tables (partial tutorial online) you can have continuous unified address space on Apple Silicon.
Let’s be honest, saying “just fix the page tables” is like telling someone they can fly if they “just rewrite gravity.”
Yes, on Apple Silicon, the hardware supports shared physical memory, and with enough “convincing”, you can rig up a contiguous virtual address space for both the CPU and GPU. Apple’s unified memory architecture makes that possible, but Apple’s APIs and memory managers don’t expose this easily or safely for a reason. You’re messing with MMU-level mappings on a tightly integrated system that treats memory as a first-class citizen of the security model.
I can tell you never programmed on an Amiga.
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