Safe Haskell | Safe-Inferred |
---|---|
Language | Haskell2010 |
Name
VK_KHR_timeline_semaphore - device extension
VK_KHR_timeline_semaphore
- Name String
VK_KHR_timeline_semaphore
- Extension Type
- Device extension
- Registered Extension Number
- 208
- Revision
- 2
- Ratification Status
- Ratified
- Extension and Version Dependencies
- VK_KHR_get_physical_device_properties2
- Deprecation State
- Promoted to Vulkan 1.2
- Contact
Other Extension Metadata
- Last Modified Date
- 2019-06-12
- IP Status
- No known IP claims.
- Interactions and External Dependencies
- This extension interacts with
VK_KHR_external_semaphore_capabilities
- This extension interacts with
VK_KHR_external_semaphore
- This extension interacts with
VK_KHR_external_semaphore_win32
- Promoted to Vulkan 1.2 Core
- This extension interacts with
- Contributors
- Jeff Bolz, NVIDIA
- Yuriy O’Donnell, Epic Games
- Faith Ekstrand, Intel
- Jesse Hall, Google
- James Jones, NVIDIA
- Jeff Juliano, NVIDIA
- Daniel Rakos, AMD
- Ray Smith, Arm
Description
This extension introduces a new type of semaphore that has an integer payload identifying a point in a timeline. Such timeline semaphores support the following operations:
- Host query - A host operation that allows querying the payload of the timeline semaphore.
- Host wait - A host operation that allows a blocking wait for a timeline semaphore to reach a specified value.
- Host signal - A host operation that allows advancing the timeline semaphore to a specified value.
- Device wait - A device operation that allows waiting for a timeline semaphore to reach a specified value.
- Device signal - A device operation that allows advancing the timeline semaphore to a specified value.
Promotion to Vulkan 1.2
All functionality in this extension is included in core Vulkan 1.2, with the KHR suffix omitted. The original type, enum and command names are still available as aliases of the core functionality.
New Commands
New Structures
SemaphoreWaitInfoKHR
Extending
PhysicalDeviceFeatures2
,DeviceCreateInfo
:Extending
PhysicalDeviceProperties2
:Extending
SemaphoreCreateInfo
,PhysicalDeviceExternalSemaphoreInfo
:Extending
SubmitInfo
,BindSparseInfo
:
New Enums
New Bitmasks
New Enum Constants
KHR_TIMELINE_SEMAPHORE_SPEC_VERSION
Extending
SemaphoreType
:Extending
SemaphoreWaitFlagBits
:Extending
StructureType
:
Issues
1) Do we need a new object type for this?
RESOLVED: No, we just introduce a new type of semaphore object, as
VK_KHR_external_semaphore_win32
already uses semaphores as the
destination for importing D3D12 fence objects, which are semantically
close/identical to the proposed synchronization primitive.
2) What type of payload the new synchronization primitive has?
RESOLVED: A 64-bit unsigned integer that can only be set to strictly increasing values by signal operations and is not changed by wait operations.
3) Does the new synchronization primitive have the same signal-before-wait requirement as the existing semaphores do?
RESOLVED: No. Timeline semaphores support signaling and waiting entirely asynchronously. It is the responsibility of the client to avoid deadlock.
4) Does the new synchronization primitive allow resetting its payload?
RESOLVED: No, allowing the payload value to “go backwards” is problematic. Applications looking for reset behavior should create a new instance of the synchronization primitive instead.
5) How do we enable host waits on the synchronization primitive?
RESOLVED: Both a non-blocking query of the current payload value of the synchronization primitive, and a blocking wait operation are provided.
6) How do we enable device waits and signals on the synchronization primitive?
RESOLVED: Similar to VK_KHR_external_semaphore_win32
, this
extension introduces a new structure that can be chained to
SubmitInfo
to specify the values signaled
semaphores should be set to, and the values waited semaphores need to
reach.
7) Can the new synchronization primitive be used to synchronize presentation and swapchain image acquisition operations?
RESOLVED: Some implementations may have problems with supporting that directly, thus it is not allowed in this extension.
8) Do we want to support external sharing of the new synchronization primitive type?
RESOLVED: Yes. Timeline semaphore specific external sharing
capabilities can be queried using
getPhysicalDeviceExternalSemaphoreProperties
by chaining the new SemaphoreTypeCreateInfoKHR
structure to its
pExternalSemaphoreInfo
structure. This allows having a different set
of external semaphore handle types supported for timeline semaphores vs.
binary semaphores.
9) Do we need to add a host signal operation for the new synchronization primitive type?
RESOLVED: Yes. This helps in situations where one host thread submits a workload but another host thread has the information on when the workload is ready to be executed.
10) How should the new synchronization primitive interact with the
ordering requirements of the original Semaphore
?
RESOLVED: Prior to calling any command which may cause a wait operation on a binary semaphore, the client must ensure that the semaphore signal operation that has been submitted for execution and any semaphore signal operations on which it depends (if any) must have also been submitted for execution.
11) Should we have separate feature bits for different sub-features of timeline semaphores?
RESOLVED: No. The only feature which cannot be supported universally
is timeline semaphore import/export. For import/export, the client is
already required to query available external handle types via
getPhysicalDeviceExternalSemaphoreProperties
and provide the semaphore type by adding a SemaphoreTypeCreateInfoKHR
structure to the pNext
chain of
PhysicalDeviceExternalSemaphoreInfo
so no new feature bit is required.
Version History
Revision 1, 2018-05-10 (Faith Ekstrand)
- Initial version
Revision 2, 2019-06-12 (Faith Ekstrand)
- Added an initialValue parameter to timeline semaphore creation
See Also
PhysicalDeviceTimelineSemaphoreFeaturesKHR
,
PhysicalDeviceTimelineSemaphorePropertiesKHR
,
SemaphoreSignalInfoKHR
, SemaphoreTypeCreateInfoKHR
,
SemaphoreTypeKHR
, SemaphoreWaitFlagBitsKHR
, SemaphoreWaitFlagsKHR
,
SemaphoreWaitInfoKHR
, TimelineSemaphoreSubmitInfoKHR
,
getSemaphoreCounterValueKHR
, signalSemaphoreKHR
, waitSemaphoresKHR
Document Notes
For more information, see the Vulkan Specification
This page is a generated document. Fixes and changes should be made to the generator scripts, not directly.
Documentation
pattern SEMAPHORE_TYPE_BINARY_KHR :: SemaphoreType Source #
pattern SEMAPHORE_TYPE_TIMELINE_KHR :: SemaphoreType Source #
pattern SEMAPHORE_WAIT_ANY_BIT_KHR :: SemaphoreWaitFlagBits Source #
getSemaphoreCounterValueKHR :: MonadIO io => Device -> Semaphore -> io ("value" ::: Word64) Source #
waitSemaphoresKHR :: MonadIO io => Device -> SemaphoreWaitInfo -> ("timeout" ::: Word64) -> io Result Source #
signalSemaphoreKHR :: MonadIO io => Device -> SemaphoreSignalInfo -> io () Source #
type SemaphoreTypeKHR = SemaphoreType Source #
type PhysicalDeviceTimelineSemaphorePropertiesKHR = PhysicalDeviceTimelineSemaphoreProperties Source #
type KHR_TIMELINE_SEMAPHORE_SPEC_VERSION = 2 Source #
pattern KHR_TIMELINE_SEMAPHORE_SPEC_VERSION :: forall a. Integral a => a Source #
type KHR_TIMELINE_SEMAPHORE_EXTENSION_NAME = "VK_KHR_timeline_semaphore" Source #
pattern KHR_TIMELINE_SEMAPHORE_EXTENSION_NAME :: forall a. (Eq a, IsString a) => a Source #