C Specification

Additional information about the pool is passed in an instance of the VkDescriptorPoolCreateInfo structure:

typedef struct VkDescriptorPoolCreateInfo {
    VkStructureType                sType;
    const void*                    pNext;
    VkDescriptorPoolCreateFlags    flags;
    uint32_t                       maxSets;
    uint32_t                       poolSizeCount;
    const VkDescriptorPoolSize*    pPoolSizes;
} VkDescriptorPoolCreateInfo;

Members

  • sType is the type of this structure.

  • pNext is NULL or a pointer to an extension-specific structure.

  • flags specifies certain supported operations on the pool. Bits which can be set include:

    typedef enum VkDescriptorPoolCreateFlagBits {
        VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT = 0x00000001,
    } VkDescriptorPoolCreateFlagBits;

    If flags includes VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT, then descriptor sets can return their individual allocations to the pool, i.e. all of vkAllocateDescriptorSets, vkFreeDescriptorSets, and vkResetDescriptorPool are allowed. Otherwise, descriptor sets allocated from the pool must not be individually freed back to the pool, i.e. only vkAllocateDescriptorSets and vkResetDescriptorPool are allowed.

  • maxSets is the maximum number of descriptor sets that can be allocated from the pool.

  • poolSizeCount is the number of elements in pPoolSizes.

  • pPoolSizes is a pointer to an array of VkDescriptorPoolSize structures, each containing a descriptor type and number of descriptors of that type to be allocated in the pool.

Description

If multiple VkDescriptorPoolSize structures appear in the pPoolSizes array then the pool will be created with enough storage for the total number of descriptors of each type.

Fragmentation of a descriptor pool is possible and may lead to descriptor set allocation failures. A failure due to fragmentation is defined as failing a descriptor set allocation despite the sum of all outstanding descriptor set allocations from the pool plus the requested allocation requiring no more than the total number of descriptors requested at pool creation. Implementations provide certain guarantees of when fragmentation must not cause allocation failure, as described below.

If a descriptor pool has not had any descriptor sets freed since it was created or most recently reset then fragmentation must not cause an allocation failure (note that this is always the case for a pool created without the VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT bit set). Additionally, if all sets allocated from the pool since it was created or most recently reset use the same number of descriptors (of each type) and the requested allocation also uses that same number of descriptors (of each type), then fragmentation must not cause an allocation failure.

If an allocation failure occurs due to fragmentation, an application can create an additional descriptor pool to perform further descriptor set allocations.

Valid Usage
  • maxSets must be greater than 0

Valid Usage (Implicit)
  • sType must be VK_STRUCTURE_TYPE_DESCRIPTOR_POOL_CREATE_INFO

  • pNext must be NULL

  • flags must be a valid combination of VkDescriptorPoolCreateFlagBits values

  • pPoolSizes must be a pointer to an array of poolSizeCount valid VkDescriptorPoolSize structures

  • poolSizeCount must be greater than 0

See Also

Document Notes

For more information, see the Vulkan Specification at URL

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification,not directly.

Copyright (c) 2014-2016 Khronos Group. This work is licensed under a Creative Commons Attribution 4.0 International License.