Vulkan Memory Allocator
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Quick start

Project setup

Vulkan Memory Allocator comes in form of a "stb-style" single header file. You don't need to build it as a separate library project. You can add this file directly to your project and submit it to code repository next to your other source files.

"Single header" doesn't mean that everything is contained in C/C++ declarations, like it tends to be in case of inline functions or C++ templates. It means that implementation is bundled with interface in a single file and needs to be extracted using preprocessor macro. If you don't do it properly, you will get linker errors.

To do it properly:

  1. Include "vk_mem_alloc.h" file in each CPP file where you want to use the library. This includes declarations of all members of the library.
  2. In exactly one CPP file define following macro before this include. It enables also internal definitions.
#include "vk_mem_alloc.h"

It may be a good idea to create dedicated CPP file just for this purpose.

This library includes header <vulkan/vulkan.h>, which in turn includes <windows.h> on Windows. If you need some specific macros defined before including these headers (like WIN32_LEAN_AND_MEAN or WINVER for Windows, VK_USE_PLATFORM_WIN32_KHR for Vulkan), you must define them before every #include of this library.

This library is written in C++, but has C-compatible interface. Thus you can include and use vk_mem_alloc.h in C or C++ code, but full implementation with VMA_IMPLEMENTATION macro must be compiled as C++, NOT as C. Some features of C++14 are used. STL containers, RTTI, or C++ exceptions are not used.


At program startup:

  1. Initialize Vulkan to have VkPhysicalDevice, VkDevice and VkInstance object.
  2. Fill VmaAllocatorCreateInfo structure and create VmaAllocator object by calling vmaCreateAllocator().

Only members physicalDevice, device, instance are required. However, you should inform the library which Vulkan version do you use by setting VmaAllocatorCreateInfo::vulkanApiVersion and which extensions did you enable by setting VmaAllocatorCreateInfo::flags (like VMA_ALLOCATOR_CREATE_BUFFER_DEVICE_ADDRESS_BIT for VK_KHR_buffer_device_address). Otherwise, VMA would use only features of Vulkan 1.0 core with no extensions.

Selecting Vulkan version

VMA supports Vulkan version down to 1.0, for backward compatibility. If you want to use higher version, you need to inform the library about it. This is a two-step process.

Step 1: Compile time. By default, VMA compiles with code supporting the highest Vulkan version found in the included <vulkan/vulkan.h> that is also supported by the library. If this is OK, you don't need to do anything. However, if you want to compile VMA as if only some lower Vulkan version was available, define macro VMA_VULKAN_VERSION before every #include "vk_mem_alloc.h". It should have decimal numeric value in form of ABBBCCC, where A = major, BBB = minor, CCC = patch Vulkan version. For example, to compile against Vulkan 1.2:

#define VMA_VULKAN_VERSION 1002000 // Vulkan 1.2
#include "vk_mem_alloc.h"

Step 2: Runtime. Even when compiled with higher Vulkan version available, VMA can use only features of a lower version, which is configurable during creation of the VmaAllocator object. By default, only Vulkan 1.0 is used. To initialize the allocator with support for higher Vulkan version, you need to set member VmaAllocatorCreateInfo::vulkanApiVersion to an appropriate value, e.g. using constants like VK_API_VERSION_1_2. See code sample below.

Importing Vulkan functions

You may need to configure importing Vulkan functions. There are 3 ways to do this:

  1. If you link with Vulkan static library (e.g. "vulkan-1.lib" on Windows):
    • You don't need to do anything.
    • VMA will use these, as macro VMA_STATIC_VULKAN_FUNCTIONS is defined to 1 by default.
  2. If you want VMA to fetch pointers to Vulkan functions dynamically using vkGetInstanceProcAddr, vkGetDeviceProcAddr (this is the option presented in the example below):
  3. If you fetch pointers to all Vulkan functions in a custom way, e.g. using some loader like Volk:
    • Pass these pointers via structure VmaVulkanFunctions.

Example for case 2:

#include "vk_mem_alloc.h"
VmaVulkanFunctions vulkanFunctions = {};
vulkanFunctions.vkGetInstanceProcAddr = &vkGetInstanceProcAddr;
vulkanFunctions.vkGetDeviceProcAddr = &vkGetDeviceProcAddr;
VmaAllocatorCreateInfo allocatorCreateInfo = {};
allocatorCreateInfo.vulkanApiVersion = VK_API_VERSION_1_2;
allocatorCreateInfo.physicalDevice = physicalDevice;
allocatorCreateInfo.device = device;
allocatorCreateInfo.instance = instance;
allocatorCreateInfo.pVulkanFunctions = &vulkanFunctions;
VmaAllocator allocator;
vmaCreateAllocator(&allocatorCreateInfo, &allocator);
VkResult vmaCreateAllocator(const VmaAllocatorCreateInfo *pCreateInfo, VmaAllocator *pAllocator)
Creates VmaAllocator object.
Description of a Allocator to be created.
Definition: vk_mem_alloc.h:998
VkPhysicalDevice physicalDevice
Vulkan physical device.
Definition: vk_mem_alloc.h:1003
const VmaVulkanFunctions * pVulkanFunctions
Pointers to Vulkan functions. Can be null.
Definition: vk_mem_alloc.h:1046
VkInstance instance
Handle to Vulkan instance object.
Definition: vk_mem_alloc.h:1051
VkDevice device
Vulkan device.
Definition: vk_mem_alloc.h:1006
uint32_t vulkanApiVersion
Optional. The highest version of Vulkan that the application is designed to use.
Definition: vk_mem_alloc.h:1060
Represents main object of this library initialized.

Resource allocation

When you want to create a buffer or image:

  1. Fill VkBufferCreateInfo / VkImageCreateInfo structure.
  2. Fill VmaAllocationCreateInfo structure.
  3. Call vmaCreateBuffer() / vmaCreateImage() to get VkBuffer/VkImage with memory already allocated and bound to it, plus VmaAllocation objects that represents its underlying memory.
VkBufferCreateInfo bufferInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };
bufferInfo.size = 65536;
VmaAllocationCreateInfo allocInfo = {};
VkBuffer buffer;
VmaAllocation allocation;
vmaCreateBuffer(allocator, &bufferInfo, &allocInfo, &buffer, &allocation, nullptr);
VkResult vmaCreateBuffer(VmaAllocator allocator, const VkBufferCreateInfo *pBufferCreateInfo, const VmaAllocationCreateInfo *pAllocationCreateInfo, VkBuffer *pBuffer, VmaAllocation *pAllocation, VmaAllocationInfo *pAllocationInfo)
Creates a new VkBuffer, allocates and binds memory for it.
Definition: vk_mem_alloc.h:489
Parameters of new VmaAllocation.
Definition: vk_mem_alloc.h:1219
VmaMemoryUsage usage
Intended usage of memory.
Definition: vk_mem_alloc.h:1227
Represents single memory allocation.

Don't forget to destroy your objects when no longer needed:

vmaDestroyBuffer(allocator, buffer, allocation);
void vmaDestroyBuffer(VmaAllocator allocator, VkBuffer buffer, VmaAllocation allocation)
Destroys Vulkan buffer and frees allocated memory.
void vmaDestroyAllocator(VmaAllocator allocator)
Destroys allocator object.