VkExternalMemoryAcquireUnmodifiedEXT(3)

# VkExternalMemoryAcquireUnmodifiedEXT(3) Manual Page

## Name

VkExternalMemoryAcquireUnmodifiedEXT - Structure specifying that external memory has remained unmodified since releasing ownership

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## C Specification

An acquire operation may have a performance penalty when acquiring ownership of a subresource range from one of the special queue families reserved for external memory ownership transfers described above. The application can reduce the performance penalty in some cases by adding a VkExternalMemoryAcquireUnmodifiedEXT structure to the `pNext` chain of the acquire operation's memory barrier structure.

The `VkExternalMemoryAcquireUnmodifiedEXT` structure is defined as:

    // Provided by VK_EXT_external_memory_acquire_unmodified
    typedef struct VkExternalMemoryAcquireUnmodifiedEXT {
        VkStructureType    sType;
        const void*        pNext;
        VkBool32           acquireUnmodifiedMemory;
    } VkExternalMemoryAcquireUnmodifiedEXT;

## Members

- `sType` is a VkStructureType value identifying this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `acquireUnmodifiedMemory` specifies, if `VK_TRUE`, that no range of VkDeviceMemory bound to the resource of the memory barrier’s subresource range was modified at any time since the resource’s most recent release of ownership to the queue family specified by the memory barrier’s `srcQueueFamilyIndex`. If `VK_FALSE`, it specifies nothing.

## Description

If the application releases ownership of the subresource range to one of the special queue families reserved for external memory ownership transfers with a memory barrier structure, and later re-acquires ownership from the same queue family with a memory barrier structure, and if no range of VkDeviceMemory bound to the resource was modified at any time between the release operation and the acquire operation, then the application should add a VkExternalMemoryAcquireUnmodifiedEXT structure to the `pNext` chain of the acquire operation's memory barrier structure because this may reduce the performance penalty.

This struct is ignored if `acquireUnmodifiedMemory` is `VK_FALSE`. In particular, `VK_FALSE` does not specify that memory was modified.

This struct is ignored if the memory barrier’s `srcQueueFamilyIndex` is not a special queue family reserved for external memory ownership transfers.

| Note The method by which the application determines whether memory was modified between the release operation and acquire operation is outside the scope of Vulkan. For any Vulkan operation that accesses a resource, the application must not assume the implementation accesses the resource’s memory as read-only, even for apparently read-only operations such as transfer commands and shader reads. The validity of VkExternalMemoryAcquireUnmodifiedEXT::`acquireUnmodifiedMemory` is independent of memory ranges outside the ranges of VkDeviceMemory bound to the resource. In particular, it is independent of any implementation-private memory associated with the resource.

Valid Usage

- VUID-VkExternalMemoryAcquireUnmodifiedEXT-acquireUnmodifiedMemory-08922
  If `acquireUnmodifiedMemory` is `VK_TRUE`, and the memory barrier’s `srcQueueFamilyIndex` is a special queue family reserved for external memory ownership transfers (as described in https://registry.khronos.org/vulkan/specs/1.3-extensions/html/vkspec.html#synchronization-queue-transfers), then each range of VkDeviceMemory bound to the resource must have remained unmodified during all time since the resource’s most recent release of ownership to the queue family.

Valid Usage (Implicit)

- VUID-VkExternalMemoryAcquireUnmodifiedEXT-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_EXTERNAL_MEMORY_ACQUIRE_UNMODIFIED_EXT`

## See Also

VK_EXT_external_memory_acquire_unmodified, VkBool32, VkStructureType

## Document Notes

For more information, see the Vulkan Specification

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

## Copyright

Copyright 2014-2023 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0