C Specification
To query if using VK_IMAGE_USAGE_HOST_TRANSFER_BIT_EXT
has a negative
impact on device performance when accessing an image, add
VK_IMAGE_USAGE_HOST_TRANSFER_BIT_EXT
to
VkPhysicalDeviceImageFormatInfo2::usage
, and add a
VkHostImageCopyDevicePerformanceQueryEXT
structure to the pNext
chain of a VkImageFormatProperties2 structure passed to
vkGetPhysicalDeviceImageFormatProperties2.
This structure is defined as:
// Provided by VK_EXT_host_image_copy
typedef struct VkHostImageCopyDevicePerformanceQueryEXT {
VkStructureType sType;
void* pNext;
VkBool32 optimalDeviceAccess;
VkBool32 identicalMemoryLayout;
} VkHostImageCopyDevicePerformanceQueryEXT;
Members
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
optimalDeviceAccess
returnsVK_TRUE
if use of host image copy has no adverse effect on device access performance, compared to an image that is created with exact same creation parameters, and bound to the same VkDeviceMemory, except thatVK_IMAGE_USAGE_HOST_TRANSFER_BIT_EXT
is replaced withVK_IMAGE_USAGE_TRANSFER_SRC_BIT
andVK_IMAGE_USAGE_TRANSFER_DST_BIT
. -
identicalMemoryLayout
returnsVK_TRUE
if use of host image copy has no impact on memory layout compared to an image that is created with exact same creation parameters, and bound to the same VkDeviceMemory, except thatVK_IMAGE_USAGE_HOST_TRANSFER_BIT_EXT
is replaced withVK_IMAGE_USAGE_TRANSFER_SRC_BIT
andVK_IMAGE_USAGE_TRANSFER_DST_BIT
.
Description
The implementation may return VK_FALSE
in optimalDeviceAccess
if identicalMemoryLayout
is VK_FALSE
.
If identicalMemoryLayout
is VK_TRUE
, optimalDeviceAccess
must be VK_TRUE
.
The implementation may return VK_TRUE
in optimalDeviceAccess
while identicalMemoryLayout
is VK_FALSE
.
In this situation, any device performance impact should not be measurable.
If VkPhysicalDeviceImageFormatInfo2::format
is a
block-compressed format and vkGetPhysicalDeviceImageFormatProperties2
returns VK_SUCCESS
, the implementation must return VK_TRUE
in
optimalDeviceAccess
.
Note
Applications can make use of |
Note
Layout not being identical yet still considered optimal for device access could happen if the implementation has different memory layout patterns, some of which are easier to access on the host. |
Note
The most practical reason for |
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.