Vulkan Memory Allocator
Allocation names and user data

Allocation user data

You can annotate allocations with your own information, e.g. for debugging purposes. To do that, fill VmaAllocationCreateInfo::pUserData field when creating an allocation. It is an opaque void* pointer. You can use it e.g. as a pointer, some handle, index, key, ordinal number or any other value that would associate the allocation with your custom metadata.

VkBufferCreateInfo bufferInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };
// Fill bufferInfo...
MyBufferMetadata* pMetadata = CreateBufferMetadata();
VmaAllocationCreateInfo allocCreateInfo = {};
allocCreateInfo.usage = VMA_MEMORY_USAGE_GPU_ONLY;
allocCreateInfo.pUserData = pMetadata;
VkBuffer buffer;
VmaAllocation allocation;
vmaCreateBuffer(allocator, &bufferInfo, &allocCreateInfo, &buffer, &allocation, nullptr);
Definition: vk_mem_alloc.h:1014
void * pUserData
Custom general-purpose pointer that will be stored in VmaAllocation, can be read as VmaAllocationInfo...
Definition: vk_mem_alloc.h:1053
VmaMemoryUsage usage
Intended usage of memory.
Definition: vk_mem_alloc.h:1022
Represents single memory allocation.
@ VMA_MEMORY_USAGE_GPU_ONLY
Definition: vk_mem_alloc.h:434
VkResult vmaCreateBuffer(VmaAllocator allocator, const VkBufferCreateInfo *pBufferCreateInfo, const VmaAllocationCreateInfo *pAllocationCreateInfo, VkBuffer *pBuffer, VmaAllocation *pAllocation, VmaAllocationInfo *pAllocationInfo)

The pointer may be later retrieved as VmaAllocationInfo::pUserData:

vmaGetAllocationInfo(allocator, allocation, &allocInfo);
MyBufferMetadata* pMetadata = (MyBufferMetadata*)allocInfo.pUserData;
Parameters of VmaAllocation objects, that can be retrieved using function vmaGetAllocationInfo().
Definition: vk_mem_alloc.h:1142
void * pUserData
Custom general-purpose pointer that was passed as VmaAllocationCreateInfo::pUserData or set using vma...
Definition: vk_mem_alloc.h:1189
void vmaGetAllocationInfo(VmaAllocator allocator, VmaAllocation allocation, VmaAllocationInfo *pAllocationInfo)
Returns current information about specified allocation.

It can also be changed using function vmaSetAllocationUserData().

Values of (non-zero) allocations' pUserData are printed in JSON report created by vmaBuildStatsString(), in hexadecimal form.

Allocation names

There is alternative mode available where pUserData pointer is used to point to a null-terminated string, giving a name to the allocation. To use this mode, set VMA_ALLOCATION_CREATE_USER_DATA_COPY_STRING_BIT flag in VmaAllocationCreateInfo::flags. Then pUserData passed as VmaAllocationCreateInfo::pUserData or argument to vmaSetAllocationUserData() must be either null or pointer to a null-terminated string. The library creates internal copy of the string, so the pointer you pass doesn't need to be valid for whole lifetime of the allocation. You can free it after the call.

VkImageCreateInfo imageInfo = { VK_STRUCTURE_TYPE_IMAGE_CREATE_INFO };
// Fill imageInfo...
std::string imageName = "Texture: ";
imageName += fileName;
VmaAllocationCreateInfo allocCreateInfo = {};
allocCreateInfo.usage = VMA_MEMORY_USAGE_GPU_ONLY;
allocCreateInfo.pUserData = imageName.c_str();
VkImage image;
VmaAllocation allocation;
vmaCreateImage(allocator, &imageInfo, &allocCreateInfo, &image, &allocation, nullptr);
VmaAllocationCreateFlags flags
Use VmaAllocationCreateFlagBits enum.
Definition: vk_mem_alloc.h:1016
VkResult vmaCreateImage(VmaAllocator allocator, const VkImageCreateInfo *pImageCreateInfo, const VmaAllocationCreateInfo *pAllocationCreateInfo, VkImage *pImage, VmaAllocation *pAllocation, VmaAllocationInfo *pAllocationInfo)
Function similar to vmaCreateBuffer().
@ VMA_ALLOCATION_CREATE_USER_DATA_COPY_STRING_BIT
Definition: vk_mem_alloc.h:518

The value of pUserData pointer of the allocation will be different than the one you passed when setting allocation's name - pointing to a buffer managed internally that holds copy of the string.

vmaGetAllocationInfo(allocator, allocation, &allocInfo);
const char* imageName = (const char*)allocInfo.pUserData;
printf("Image name: %s\n", imageName);

That string is also printed in JSON report created by vmaBuildStatsString().

Note
Passing string name to VMA allocation doesn't automatically set it to the Vulkan buffer or image created with it. You must do it manually using an extension like VK_EXT_debug_utils, which is independent of this library.