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. To enable it:

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 . Query device for pointers to following 2 extension functions, using vkGetDeviceProcAddr(). Pass them in structure VmaVulkanFunctions while creating your VmaAllocator.

vkGetBufferMemoryRequirements2KHR
vkGetImageMemoryRequirements2KHR

Other members of this structure can be null as long as you leave VMA_STATIC_VULKAN_FUNCTIONS defined to 1, which is the default.

VmaVulkanFunctions vulkanFunctions = {};
vulkanFunctions.vkGetBufferMemoryRequirements2KHR =
    (PFN_vkGetBufferMemoryRequirements2KHR)vkGetDeviceProcAddr(device, "vkGetBufferMemoryRequirements2KHR");
vulkanFunctions.vkGetImageMemoryRequirements2KHR =
    (PFN_vkGetImageMemoryRequirements2KHR)vkGetDeviceProcAddr(device, "vkGetImageMemoryRequirements2KHR");
    
VmaAllocatorCreateInfo allocatorInfo = {};
allocatorInfo.pVulkanFunctions = &vulkanFunctions;
// Fill other members of allocatorInfo...

3 . 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);

That's 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: