VK_EXT_pipeline_creation_cache_control
Other Extension Metadata
Last Modified Date
2020-03-23
IP Status
No known IP claims.
Contributors
- Gregory Grebe, AMD
- Tobias Hector, AMD
- Matthaeus Chajdas, AMD
- Mitch Singer, AMD
- Spencer Fricke, Samsung Electronics
- Stuart Smith, Imagination Technologies
- Jeff Bolz, NVIDIA Corporation
- Daniel Koch, NVIDIA Corporation
- Dan Ginsburg, Valve Corporation
- Jeff Leger, QUALCOMM
- Michal Pietrasiuk, Intel
- Jan-Harald Fredriksen, Arm Limited
Description
This extension adds flags to Vk*PipelineCreateInfo
and
VkPipelineCacheCreateInfo structures with the aim of improving the
predictability of pipeline creation cost.
The goal is to provide information about potentially expensive hazards
within the client driver during pipeline creation to the application before
carrying them out rather than after.
Background
Pipeline creation is a costly operation, and the explicit nature of the Vulkan design means that cost is not hidden from the developer. Applications are also expected to schedule, prioritize, and load balance all calls for pipeline creation. It is strongly advised that applications create pipelines sufficiently ahead of their usage. Failure to do so will result in an unresponsive application, intermittent stuttering, or other poor user experiences. Proper usage of pipeline caches and/or derivative pipelines help mitigate this but is not assured to eliminate disruption in all cases. In the event that an ahead-of-time creation is not possible, considerations should be taken to ensure that the current execution context is suitable for the workload of pipeline creation including possible shader compilation.
Applications making API calls to create a pipeline must be prepared for any of the following to occur:
- OS/kernel calls to be made by the ICD
- Internal memory allocation not tracked by the
pAllocator
passed tovkCreate*Pipelines
- Internal thread synchronization or yielding of the current thread’s core
- Extremely long (multi-millisecond+), blocking, compilation times
- Arbitrary call stacks depths and stack memory usage
The job or task based game engines that are being developed to take
advantage of explicit graphics APIs like Vulkan may behave exceptionally
poorly if any of the above scenarios occur.
However, most game engines are already built to stream
in assets
dynamically as the user plays the game.
By adding control by way of VkPipelineCreateFlags, we can require an
ICD to report back a failure in critical execution paths rather than forcing
an unexpected wait.
Applications can prevent unexpected compilation by setting
VK_PIPELINE_CREATE_FAIL_ON_PIPELINE_COMPILE_REQUIRED_BIT_EXT
on
Vk*PipelineCreateInfo
::flags
.
When set, an ICD must not attempt pipeline or shader compilation to create
the pipeline object.
In such a case, if the implementation fails to create a pipeline without
compilation, the implementation must return the result
VK_PIPELINE_COMPILE_REQUIRED_EXT
and return VK_NULL_HANDLE for
the pipeline.
By default vkCreate*Pipelines
calls must attempt to create all
pipelines before returning.
Setting VK_PIPELINE_CREATE_EARLY_RETURN_ON_FAILURE_BIT_EXT
on
Vk*PipelineCreateInfo
::flags
can be used as an escape hatch for
batched pipeline creates.
Hidden locks also add to the unpredictability of the cost of pipeline
creation.
The most common case of locks inside the vkCreate*Pipelines
is
internal synchronization of the VkPipelineCache object.
VK_PIPELINE_CACHE_CREATE_EXTERNALLY_SYNCHRONIZED_BIT_EXT
can be set
when calling vkCreatePipelineCache to state the cache is
externally synchronized.
The hope is that armed with this information application and engine developers can leverage existing asset streaming systems to recover from "just-in-time" pipeline creation stalls.
New Structures
- Extending VkPhysicalDeviceFeatures2, VkDeviceCreateInfo:
New Enums
New Enum Constants
VK_EXT_PIPELINE_CREATION_CACHE_CONTROL_EXTENSION_NAME
VK_EXT_PIPELINE_CREATION_CACHE_CONTROL_SPEC_VERSION
- Extending VkPipelineCacheCreateFlagBits:
VK_PIPELINE_CACHE_CREATE_EXTERNALLY_SYNCHRONIZED_BIT_EXT
- Extending VkPipelineCreateFlagBits:
VK_PIPELINE_CREATE_EARLY_RETURN_ON_FAILURE_BIT_EXT
VK_PIPELINE_CREATE_FAIL_ON_PIPELINE_COMPILE_REQUIRED_BIT_EXT
- Extending VkResult:
VK_ERROR_PIPELINE_COMPILE_REQUIRED_EXT
VK_PIPELINE_COMPILE_REQUIRED_EXT
- Extending VkStructureType:
VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_PIPELINE_CREATION_CACHE_CONTROL_FEATURES_EXT
Promotion to Vulkan 1.3
Functionality in this extension is included in core Vulkan 1.3, with the EXT suffix omitted. The original type, enum and command names are still available as aliases of the core functionality.
Version History
- Revision 1, 2019-11-01 (Gregory Grebe)
- Initial revision
- Revision 2, 2020-02-24 (Gregory Grebe)
- Initial public revision
- Revision 3, 2020-03-23 (Tobias Hector)
- Changed
VK_PIPELINE_COMPILE_REQUIRED_EXT
to a success code, adding an alias for the originalVK_ERROR_PIPELINE_COMPILE_REQUIRED_EXT
. Also updated the xml to include these codes as return values.
- Changed