VK_KHR_dedicated_allocation

Other Extension Metadata

Last Modified Date

2017-09-05

IP Status

No known IP claims.

Contributors

• Jeff Bolz, NVIDIA
• Faith Ekstrand, Intel

Description

This extension enables resources to be bound to a dedicated allocation, rather than suballocated. For any particular resource, applications can query whether a dedicated allocation is recommended, in which case using a dedicated allocation may improve the performance of access to that resource. Normal device memory allocations must support multiple resources per allocation, memory aliasing and sparse binding, which could interfere with some optimizations. Applications should query the implementation for when a dedicated allocation may be beneficial by adding a VkMemoryDedicatedRequirementsKHR structure to the pNext chain of the VkMemoryRequirements2 structure passed as the pMemoryRequirements parameter of a call to vkGetBufferMemoryRequirements2 or vkGetImageMemoryRequirements2. Certain external handle types and external images or buffers may also depend on dedicated allocations on implementations that associate image or buffer metadata with OS-level memory objects.

This extension adds a two small structures to memory requirements querying and memory allocation: a new structure that flags whether an image/buffer should have a dedicated allocation, and a structure indicating the image or buffer that an allocation will be bound to.

Promotion to Vulkan 1.1

All functionality in this extension is included in core Vulkan 1.1, with the KHR suffix omitted. The original type, enum, and command names are still available as aliases of the core functionality.

New Structures

• Extending VkMemoryAllocateInfo:
  • VkMemoryDedicatedAllocateInfoKHR
• Extending VkMemoryRequirements2:
  • VkMemoryDedicatedRequirementsKHR

New Enum Constants

• VK_KHR_DEDICATED_ALLOCATION_EXTENSION_NAME
• VK_KHR_DEDICATED_ALLOCATION_SPEC_VERSION
• Extending VkStructureType:
  • VK_STRUCTURE_TYPE_MEMORY_DEDICATED_ALLOCATE_INFO_KHR
  • VK_STRUCTURE_TYPE_MEMORY_DEDICATED_REQUIREMENTS_KHR

Examples

    // Create an image with a dedicated allocation based on the
    // implementation's preference

    VkImageCreateInfo imageCreateInfo =
    {
        // Image creation parameters
    };

    VkImage image;
    VkResult result = vkCreateImage(
        device,
        &imageCreateInfo,
        NULL,               // pAllocator
        &image);

    VkMemoryDedicatedRequirementsKHR dedicatedRequirements =
    {
        .sType = VK_STRUCTURE_TYPE_MEMORY_DEDICATED_REQUIREMENTS_KHR,
        .pNext = NULL,
    };

    VkMemoryRequirements2 memoryRequirements =
    {
        .sType = VK_STRUCTURE_TYPE_MEMORY_REQUIREMENTS_2,
        .pNext = &dedicatedRequirements,
    };

    const VkImageMemoryRequirementsInfo2 imageRequirementsInfo =
    {
        .sType = VK_STRUCTURE_TYPE_IMAGE_MEMORY_REQUIREMENTS_INFO_2,
        .pNext = NULL,
        .image = image
    };

    vkGetImageMemoryRequirements2(
        device,
        &imageRequirementsInfo,
        &memoryRequirements);

    if (dedicatedRequirements.prefersDedicatedAllocation) {
        // Allocate memory with VkMemoryDedicatedAllocateInfoKHR::image
        // pointing to the image we are allocating the memory for

        VkMemoryDedicatedAllocateInfoKHR dedicatedInfo =
        {
            .sType = VK_STRUCTURE_TYPE_MEMORY_DEDICATED_ALLOCATE_INFO_KHR,
            .pNext = NULL,
            .image = image,
            .buffer = VK_NULL_HANDLE,
        };

        VkMemoryAllocateInfo memoryAllocateInfo =
        {
            .sType = VK_STRUCTURE_TYPE_MEMORY_ALLOCATE_INFO,
            .pNext = &dedicatedInfo,
            .allocationSize = memoryRequirements.size,
            .memoryTypeIndex = FindMemoryTypeIndex(memoryRequirements.memoryTypeBits),
        };

        VkDeviceMemory memory;
        vkAllocateMemory(
            device,
            &memoryAllocateInfo,
            NULL,               // pAllocator
            &memory);

        // Bind the image to the memory

        vkBindImageMemory(
            device,
            image,
            memory,
            0);
    } else {
        // Take the normal memory sub-allocation path
    }

Version History

• Revision 1, 2017-02-27 (James Jones)
  • Copy content from VK_NV_dedicated_allocation
  • Add some references to external object interactions to the overview.
• Revision 2, 2017-03-27 (Faith Ekstrand)
  • Rework the extension to be query-based
• Revision 3, 2017-07-31 (Faith Ekstrand)
  • Clarify that memory objects allocated with VkMemoryDedicatedAllocateInfoKHR can only have the specified resource bound and no others.