Vulkan Memory Allocator: VK_KHR_dedicated_allocation

Vulkan Memory Allocator

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VK_KHR_dedicated_allocation

VK_KHR_dedicated_allocation is a Vulkan extension which can be used to improve performance on some GPUs. It augments Vulkan API with possibility to query driver whether it prefers particular buffer or image to have its own, dedicated allocation (separate `VkDeviceMemory` block) for better efficiency - to be able to do some internal optimizations. The extension is supported by this library. It will be used automatically when enabled.

It has been promoted to core Vulkan 1.1, so if you use eligible Vulkan version and inform VMA about it by setting VmaAllocatorCreateInfo::vulkanApiVersion, you are all set.

Otherwise, if you want to use it as an extension:

1 . When creating Vulkan device, check if following 2 device extensions are supported (call `vkEnumerateDeviceExtensionProperties()`). If yes, enable them (fill `VkDeviceCreateInfo::ppEnabledExtensionNames`).

- VK_KHR_get_memory_requirements2
- VK_KHR_dedicated_allocation

If you enabled these extensions:

2 . Use VMA_ALLOCATOR_CREATE_KHR_DEDICATED_ALLOCATION_BIT flag when creating your VmaAllocator to inform the library that you enabled required extensions and you want the library to use them.

allocatorInfo.flags |= VMA_ALLOCATOR_CREATE_KHR_DEDICATED_ALLOCATION_BIT;
vmaCreateAllocator(&allocatorInfo, &allocator);
vmaCreateAllocator
VkResult vmaCreateAllocator(const VmaAllocatorCreateInfo *pCreateInfo, VmaAllocator *pAllocator)
Creates VmaAllocator object.
VMA_ALLOCATOR_CREATE_KHR_DEDICATED_ALLOCATION_BIT
@ VMA_ALLOCATOR_CREATE_KHR_DEDICATED_ALLOCATION_BIT
Enables usage of VK_KHR_dedicated_allocation extension.
Definition vk_mem_alloc.h:380

That is all. The extension will be automatically used whenever you create a buffer using vmaCreateBuffer() or image using vmaCreateImage().

When using the extension together with Vulkan Validation Layer, you will receive warnings like this:

vkBindBufferMemory(): Binding memory to buffer 0x33 but vkGetBufferMemoryRequirements() has not been called on that buffer.

It is OK, you should just ignore it. It happens because you use function `vkGetBufferMemoryRequirements2KHR()` instead of standard `vkGetBufferMemoryRequirements()`, while the validation layer seems to be unaware of it.

To learn more about this extension, see:

- VK_KHR_dedicated_allocation in Vulkan specification
- VK_KHR_dedicated_allocation unofficial manual