alt Hacker News> No you don't, cuMemAlloc(&ptr, size) will just give you device memory, and cuMemAllocHost will give you pinned host memory.
that's exactly what i said. You have to explicitly allocate one or the other type of memory. I.e. you have to think about what you need this memory _for_. It's literally just usage flags with extra steps.
> Why would UMA be necessary for this?
UMA is necessary if you want to be able to "just allocate some memory without caring about usage flags". Which is something you're not doing with CUDA.
> OpenGL handles this trivially,
OpenGL also doesn't allow you to explicitly manage memory. But you were asking for an explicit malloc. So which one do you want, "just make me a texture" or "just give me a chunk of memory"?
> Let me create a texture handle, and give me a function that queries the size that I can feed to malloc. That's it. No heap types, no usage flags.
Sure, that's what VMA gives you (modulo usage flags, which as we had established you can't get rid of). Excerpt from some code:
``` VmaAllocationCreateInfo vma_alloc_info = { .usage = VMA_MEMORY_USAGE_GPU_ONLY, .requiredFlags = VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT};
VkImage img; VmaAllocation allocn; const VkResult create_alloc_vkerr = vmaCreateImage( vma_allocator, &vk_image_info, // <-- populated earlier with format, dimensions, etc. &vma_alloc_info, &img, &allocn, NULL); ```
Since i dont care about reslurce aliasing, that's the extent of "memory management" that i do in my rhi. The last time i had to think about different heap types or how to bind memory was approximately never.
No, it's not usage flags with extra steps, it's less steps. It's explicitly saying you want device memory without any kind of magical guesswork of what your numerous potential combinations of usage flags may end up giving you. Just one simple device malloc.
Likewise, your claim about UMA makes zero sense. Device malloc gets you a pointer or handle to device memory, UMA has zero relation to that. The result can be unified, but there is no need for it to be.
Yeah, OpenGL does not do malloc. I'm flexible, I don't necessarily need malloc. What I want is a trivial way to allocate device memory, and Vulkan and VMA don't do that. OpenGL is also not the best example since it also uses usage flags in some cases, it's just a little less terrible than Vulkan when it comes to texture memory.
I find it fascinating how you're giving a bad VMA example and passing that of as exemplary. Like, why is there gpu-only and device-local. That vma alloc info as a whole is completely pointless because a theoretical vkMalloc should always give me device memory. I'm not going to allocate host memory for my 3d models.