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98 lines
6.2 KiB
Markdown
98 lines
6.2 KiB
Markdown
# Vulkan Memory Allocator
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Easy to integrate Vulkan memory allocation library.
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**Documentation:** See [Vulkan Memory Allocator](https://gpuopen-librariesandsdks.github.io/VulkanMemoryAllocator/html/) (generated from Doxygen-style comments in [src/vk_mem_alloc.h](src/vk_mem_alloc.h))
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**License:** MIT. See [LICENSE.txt](LICENSE.txt)
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**Changelog:** See [CHANGELOG.md](CHANGELOG.md)
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**Product page:** [Vulkan Memory Allocator on GPUOpen](https://gpuopen.com/gaming-product/vulkan-memory-allocator/)
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**Build status:**
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- Windows: [](https://ci.appveyor.com/project/adam-sawicki-amd/vulkanmemoryallocator/branch/master)
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- Linux: [](https://travis-ci.org/GPUOpen-LibrariesAndSDKs/VulkanMemoryAllocator)
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# Problem
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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:
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- It requires a lot of boilerplate code, just like everything else in Vulkan, because it is a low-level and high-performance API.
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- There is additional level of indirection: `VkDeviceMemory` is allocated separately from creating `VkBuffer`/`VkImage` and they must be bound together. The binding cannot be changed later - resource must be recreated.
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- Driver must be queried for supported memory heaps and memory types. Different IHVs provide different types of it.
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- It is recommended practice to allocate bigger chunks of memory and assign parts of them to particular resources.
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# Features
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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:
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1. Functions that help to choose correct and optimal memory type based on intended usage of the memory.
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- Required or preferred traits of the memory are expressed using higher-level description comparing to Vulkan flags.
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2. Functions that allocate memory blocks, reserve and return parts of them (`VkDeviceMemory` + offset + size) to the user.
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- 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.
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3. Functions that can create an image/buffer, allocate memory for it and bind them together - all in one call.
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Additional features:
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- Thread-safety: Library is designed to be used by multithreaded code.
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- Configuration: Fill optional members of CreateInfo structure to provide custom CPU memory allocator and other parameters.
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- 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.
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- Support memory mapping, reference-counted internally. Support for for persistently mapped memory: Just allocate with appropriate flag and you get access to mapped pointer.
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- Custom memory pools: Create a pool with desired parameters (e.g. fixed or limited maximum size) and allocate memory out of it.
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- Support for VK_KHR_dedicated_allocation extension: Enable it and it will be used automatically by the library.
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- Defragmentation: Call one function and let the library move data around to free some memory blocks and make your allocations better compacted.
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- 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.
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- 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.
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- Debug annotations: Associate string with name or opaque pointer to your own data with every allocation.
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- JSON dump: Obtain a string in JSON format with detailed map of internal state, including list of allocations and gaps between them.
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# Prequisites
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- Self-contained C++ library in single header file. No external dependencies other than standard C and C++ library and of course Vulkan.
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- Public interface in C, in same convention as Vulkan API. Implementation in C++.
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- Interface documented using Doxygen-style comments.
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- Platform-independent, but developed and tested on Windows using Visual Studio.
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- Error handling implemented by returning `VkResult` error codes - same way as in Vulkan.
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# Example
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Basic usage of this library is very simple. Advanced features are optional. After you created global `VmaAllocator` object, a complete code needed to create a buffer may look like this:
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```cpp
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VkBufferCreateInfo bufferInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };
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bufferInfo.size = 65536;
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bufferInfo.usage = VK_BUFFER_USAGE_VERTEX_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT;
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VmaAllocationCreateInfo allocInfo = {};
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allocInfo.usage = VMA_MEMORY_USAGE_GPU_ONLY;
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VkBuffer buffer;
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VmaAllocation allocation;
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vmaCreateBuffer(allocator, &bufferInfo, &allocInfo, &buffer, &allocation, nullptr);
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```
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With this one function call:
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1. `VkBuffer` is created.
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2. `VkDeviceMemory` block is allocated if needed.
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3. An unused region of the memory block is bound to this buffer.
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`VmaAllocation` is an object that represents memory assigned to this buffer. It can be queried for parameters useful e.g. if you want to map the memory on host.
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# Read more
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See **[Documentation](https://gpuopen-librariesandsdks.github.io/VulkanMemoryAllocator/html/)**.
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# Software using this library
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- **[Anvil](https://github.com/GPUOpen-LibrariesAndSDKs/Anvil)** - cross-platform framework for Vulkan
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- **[vkDOOM3](https://github.com/DustinHLand/vkDOOM3)** - Vulkan port of GPL DOOM 3 BFG Edition
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# See also
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- **[Awesome Vulkan](https://github.com/vinjn/awesome-vulkan)** - a curated list of awesome Vulkan libraries, debuggers and resources.
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- **[PyVMA](https://github.com/realitix/pyvma)** - Python wrapper for this library. Author: Jean-S<>bastien B. (@realitix). License: Apache 2.0.
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- **[vulkan-malloc](https://github.com/dylanede/vulkan-malloc)** - Vulkan memory allocation library for Rust. Based on version 1 of this library. Author: Dylan Ede (@dylanede). License: MIT / Apache 2.0.
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