Pyrogenesis  trunk
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. It it useful to identify appropriate data structures in your engine given VmaAllocation, e.g. when doing Defragmentation.

VkBufferCreateInfo bufCreateInfo = ...
MyBufferMetadata* pMetadata = CreateBufferMetadata();
VmaAllocationCreateInfo allocCreateInfo = {};
allocCreateInfo.usage = VMA_MEMORY_USAGE_AUTO;
allocCreateInfo.pUserData = pMetadata;
VkBuffer buffer;
VmaAllocation allocation;
vmaCreateBuffer(allocator, &bufCreateInfo, &allocCreateInfo, &buffer, &allocation, nullptr);

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

vmaGetAllocationInfo(allocator, allocation, &allocInfo);
MyBufferMetadata* pMetadata = (MyBufferMetadata*)allocInfo.pUserData;

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

An allocation can also carry a null-terminated string, giving a name to the allocation. To set it, call vmaSetAllocationName(). 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.

std::string imageName = "Texture: ";
imageName += fileName;
vmaSetAllocationName(allocator, allocation, imageName.c_str());

The string can be later retrieved by inspecting VmaAllocationInfo::pName. It is also printed in JSON report created by vmaBuildStatsString().

Setting 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.