Memory allocation and resource (buffer and image) creation in Vulkan is difficult (comparing to older graphics API-s, like D3D11 or OpenGL) for several reasons:
- It requires a lot of boilerplate code, just like everything else in Vulkan, because it is a low-level and high-performance API.
- There is additional level of indirection:
VkDeviceMemoryis allocated separately from creating
VkBuffer/VkImageand they must be bound together. The binding cannot be changed later - resource must be recreated.
- Driver must be queried for supported memory heaps and memory types. Different IHVs provide different types of it.
- It is recommended practice to allocate bigger chunks of memory and assign parts of them to particular resources.
This library can help game developers to manage memory allocations and resource creation by offering some higher-level functions. Features of the library are divided into several layers, low level to high level:
- Functions that help to choose correct and optimal memory type based on intended usage of the memory.
- Required or preferred traits of the memory are expressed using higher-level description comparing to Vulkan flags.
- Functions that allocate memory blocks, reserve and return parts of them (`VkDeviceMemory` + offset + size) to the user.
- Library keeps track of allocated memory blocks, used and unused ranges inside them, finds best matching unused ranges for new allocations, takes all the rules of alignment and buffer/image granularity into consideration.
- Functions that can create an image/buffer, allocate memory for it and bind them together - all in one call.
- Thread-safety: Library is designed to be used by multithreaded code.
- Configuration: Fill optional members of CreateInfo structure to provide custom CPU memory allocator and other parameters.
- Customization: Predefine appropriate macros to provide your own implementation of all external facilities used by the library, from assert, mutex, and atomic, to vector and linked list.
- Support memory mapping, reference-counted internally. Support for persistently mapped memory: Just allocate with appropriate flag and you get access to mapped pointer.
- Custom memory pools: Create a pool with desired parameters (e.g. fixed or limited maximum size) and allocate memory out of it.
- Support for VK_KHR_dedicated_allocation extension: Enable it and it will be used automatically by the library.
- Defragmentation: Call one function and let the library move data around to free some memory blocks and make your allocations better compacted.
- Lost allocations: Allocate memory with appropriate flags and let the library remove allocations that are not used for many frames to make room for new ones.
- Statistics: Obtain detailed statistics about the amount of memory used, unused, number of allocated blocks, number of allocations etc. - globally, per memory heap, and per memory type.
- Debug annotations: Associate string with name or opaque pointer to your own data with every allocation.
- JSON dump: Obtain a string in JSON format with detailed map of internal state, including list of allocations and gaps between them.
Interface Summary Interface Description VmaAllocateDeviceMemoryFunctionIInstances of this interface may be set to the
VmaFreeDeviceMemoryFunctionIInstances of this interface may be set to the
Class Summary Class Description VmaThe Vulkan Memory Allocator. VmaAllocateDeviceMemoryFunctionInstances of this class may be set to the
VmaAllocationCreateInfoMember documentation VmaAllocationCreateInfo.BufferAn array of
VmaAllocationInfoMember documentation VmaAllocationInfo.BufferAn array of
VmaAllocatorCreateInfoDescription of an Allocator to be created. VmaDefragmentationInfoMember documentation VmaDefragmentationInfo.BufferAn array of
VmaDefragmentationStatsStatistics returned by function
VmaDefragmentationStats.BufferAn array of
VmaDeviceMemoryCallbacksSet of callbacks that the library will call for
VmaDeviceMemoryCallbacks.BufferAn array of
VmaFreeDeviceMemoryFunctionInstances of this class may be set to the
VmaPoolCreateInfoMember documentation VmaPoolCreateInfo.BufferAn array of
VmaPoolStatsMember documentation VmaPoolStats.BufferAn array of
VmaStatInfoCalculated statistics of memory usage in entire allocator. VmaStatInfo.BufferAn array of
VmaStatsGeneral statistics from current state of Allocator. VmaStats.BufferAn array of
VmaVulkanFunctionsPointers to some Vulkan functions - a subset used by the library.