Vulkan.Extensions.VK_EXT_calibrated_timestamps

Name

VK_EXT_calibrated_timestamps - device extension

VK_EXT_calibrated_timestamps

Name String

VK_EXT_calibrated_timestamps

Extension Type

Device extension

Registered Extension Number

185

Revision

2

Extension and Version Dependencies

• Requires Vulkan 1.0
• Requires VK_KHR_get_physical_device_properties2

Contact

• Daniel Rakos https://github.com/KhronosGroup/Vulkan-Docs/issues/new?title=VK_EXT_calibrated_timestamps:%20&body=@drakos-amd%20

Other Extension Metadata

Last Modified Date

2018-10-04

IP Status

No known IP claims.

Contributors

• Matthaeus G. Chajdas, AMD
• Alan Harrison, AMD
• Derrick Owens, AMD
• Daniel Rakos, AMD
• Jason Ekstrand, Intel
• Keith Packard, Valve

Description

This extension provides an interface to query calibrated timestamps obtained quasi simultaneously from two time domains.

New Commands

• getCalibratedTimestampsEXT

• getPhysicalDeviceCalibrateableTimeDomainsEXT

New Structures

• CalibratedTimestampInfoEXT

New Enums

• TimeDomainEXT

New Enum Constants

• EXT_CALIBRATED_TIMESTAMPS_EXTENSION_NAME

• EXT_CALIBRATED_TIMESTAMPS_SPEC_VERSION

• Extending StructureType:

  • STRUCTURE_TYPE_CALIBRATED_TIMESTAMP_INFO_EXT

Issues

1) Is the device timestamp value returned in the same time domain as the timestamp values written by cmdWriteTimestamp?

RESOLVED: Yes.

2) What time domain is the host timestamp returned in?

RESOLVED: A query is provided to determine the calibrateable time domains. The expected host time domain used on Windows is that of QueryPerformanceCounter, and on Linux that of CLOCK_MONOTONIC.

3) Should we support other time domain combinations than just one host and the device time domain?

RESOLVED: Supporting that would need the application to query the set of supported time domains, while supporting only one host and the device time domain would only need a query for the host time domain type. The proposed API chooses the general approach for the sake of extensibility.

4) Should we use CLOCK_MONOTONIC_RAW instead of CLOCK_MONOTONIC?

RESOLVED: CLOCK_MONOTONIC is usable in a wider set of situations, however, it is subject to NTP adjustments so some use cases may prefer CLOCK_MONOTONIC_RAW. Thus this extension allows both to be exposed.

5) How can the application extrapolate future device timestamp values from the calibrated timestamp value?

RESOLVED: PhysicalDeviceLimits::timestampPeriod makes it possible to calculate future device timestamps as follows:

6) In what queue are timestamp values in time domain TIME_DOMAIN_DEVICE_EXT captured by getCalibratedTimestampsEXT?

RESOLVED: An implementation supporting this extension will have all its VkQueue share the same time domain.

futureTimestamp = calibratedTimestamp + deltaNanoseconds / timestampPeriod

6) Can the host and device timestamp values drift apart over longer periods of time?

RESOLVED: Yes, especially as some time domains by definition allow for that to happen (e.g. CLOCK_MONOTONIC is subject to NTP adjustments). Thus it is recommended that applications re-calibrate from time to time.

7) Should we add a query for reporting the maximum deviation of the timestamp values returned by calibrated timestamp queries?

RESOLVED: A global query seems inappropriate and difficult to enforce. However, it is possible to return the maximum deviation any single calibrated timestamp query can have by sampling one of the time domains twice as follows:

timestampX = timestampX_before = SampleTimeDomain(X)
for each time domain Y != X
    timestampY = SampleTimeDomain(Y)
timestampX_after = SampleTimeDomain(X)
maxDeviation = timestampX_after - timestampX_before

8) Can the maximum deviation reported ever be zero?

RESOLVED: Unless the tick of each clock corresponding to the set of time domains coincides and all clocks can literally be sampled simutaneously, there is not really a possibility for the maximum deviation to be zero, so by convention the maximum deviation is always at least the maximum of the length of the ticks of the set of time domains calibrated and thus can never be zero.

Version History

• Revision 2, 2021-03-16 (Lionel Landwerlin)

  • Specify requirement on device timestamps

• Revision 1, 2018-10-04 (Daniel Rakos)

  • Internal revisions.

See Also

CalibratedTimestampInfoEXT, TimeDomainEXT, getCalibratedTimestampsEXT, getPhysicalDeviceCalibrateableTimeDomainsEXT

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

getPhysicalDeviceCalibrateableTimeDomainsEXT

Arguments

:: forall io. MonadIO io

=> PhysicalDevice

physicalDevice is the physical device from which to query the set of calibrateable time domains.

-> io (Result, "timeDomains" ::: Vector TimeDomainEXT)

vkGetPhysicalDeviceCalibrateableTimeDomainsEXT - Query calibrateable time domains

Description

If pTimeDomains is NULL, then the number of calibrateable time domains supported for the given physicalDevice is returned in pTimeDomainCount. Otherwise, pTimeDomainCount must point to a variable set by the user to the number of elements in the pTimeDomains array, and on return the variable is overwritten with the number of values actually written to pTimeDomains. If the value of pTimeDomainCount is less than the number of calibrateable time domains supported, at most pTimeDomainCount values will be written to pTimeDomains, and INCOMPLETE will be returned instead of SUCCESS, to indicate that not all the available time domains were returned.

Valid Usage (Implicit)

• physicalDevice must be a valid PhysicalDevice handle

• pTimeDomainCount must be a valid pointer to a uint32_t value
• If the value referenced by pTimeDomainCount is not 0, and pTimeDomains is not NULL, pTimeDomains must be a valid pointer to an array of pTimeDomainCount TimeDomainEXT values

Return Codes

Success

• SUCCESS
• INCOMPLETE

Failure

• ERROR_OUT_OF_HOST_MEMORY
• ERROR_OUT_OF_DEVICE_MEMORY

See Also

PhysicalDevice, TimeDomainEXT

getCalibratedTimestampsEXT

Arguments

:: forall io. MonadIO io

=> Device

device is the logical device used to perform the query.

device must be a valid Device handle

-> ("timestampInfos" ::: Vector CalibratedTimestampInfoEXT)

pTimestampInfos is a pointer to an array of timestampCount CalibratedTimestampInfoEXT structures, describing the time domains the calibrated timestamps should be captured from.

pTimestampInfos must be a valid pointer to an array of timestampCount valid CalibratedTimestampInfoEXT structures

-> io ("timestamps" ::: Vector Word64, "maxDeviation" ::: Word64)

vkGetCalibratedTimestampsEXT - Query calibrated timestamps

Description

Note

The maximum deviation may vary between calls to getCalibratedTimestampsEXT even for the same set of time domains due to implementation and platform specific reasons. It is the application’s responsibility to assess whether the returned maximum deviation makes the timestamp values suitable for any particular purpose and can choose to re-issue the timestamp calibration call pursuing a lower devation value.

Calibrated timestamp values can be extrapolated to estimate future coinciding timestamp values, however, depending on the nature of the time domains and other properties of the platform extrapolating values over a sufficiently long period of time may no longer be accurate enough to fit any particular purpose, so applications are expected to re-calibrate the timestamps on a regular basis.

Return Codes

Success

• SUCCESS

Failure

• ERROR_OUT_OF_HOST_MEMORY
• ERROR_OUT_OF_DEVICE_MEMORY

See Also

CalibratedTimestampInfoEXT, Device

data CalibratedTimestampInfoEXT

VkCalibratedTimestampInfoEXT - Structure specifying the input parameters of a calibrated timestamp query

Valid Usage (Implicit)

See Also

StructureType, TimeDomainEXT, getCalibratedTimestampsEXT

Constructors

CalibratedTimestampInfoEXT

Fields

• timeDomain :: TimeDomainEXT

  timeDomain is a TimeDomainEXT value specifying the time domain from which the calibrated timestamp value should be returned.

  timeDomain must be one of the TimeDomainEXT values returned by getPhysicalDeviceCalibrateableTimeDomainsEXT

  timeDomain must be a valid TimeDomainEXT value

Instances

Eq CalibratedTimestampInfoEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

(==) :: CalibratedTimestampInfoEXT -> CalibratedTimestampInfoEXT -> Bool

(/=) :: CalibratedTimestampInfoEXT -> CalibratedTimestampInfoEXT -> Bool

Show CalibratedTimestampInfoEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

showsPrec :: Int -> CalibratedTimestampInfoEXT -> ShowS

show :: CalibratedTimestampInfoEXT -> String

showList :: [CalibratedTimestampInfoEXT] -> ShowS

Storable CalibratedTimestampInfoEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

sizeOf :: CalibratedTimestampInfoEXT -> Int

alignment :: CalibratedTimestampInfoEXT -> Int

peekElemOff :: Ptr CalibratedTimestampInfoEXT -> Int -> IO CalibratedTimestampInfoEXT

pokeElemOff :: Ptr CalibratedTimestampInfoEXT -> Int -> CalibratedTimestampInfoEXT -> IO ()

peekByteOff :: Ptr b -> Int -> IO CalibratedTimestampInfoEXT

pokeByteOff :: Ptr b -> Int -> CalibratedTimestampInfoEXT -> IO ()

peek :: Ptr CalibratedTimestampInfoEXT -> IO CalibratedTimestampInfoEXT

poke :: Ptr CalibratedTimestampInfoEXT -> CalibratedTimestampInfoEXT -> IO ()

FromCStruct CalibratedTimestampInfoEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

peekCStruct :: Ptr CalibratedTimestampInfoEXT -> IO CalibratedTimestampInfoEXT

ToCStruct CalibratedTimestampInfoEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

withCStruct :: CalibratedTimestampInfoEXT -> (Ptr CalibratedTimestampInfoEXT -> IO b) -> IO b

pokeCStruct :: Ptr CalibratedTimestampInfoEXT -> CalibratedTimestampInfoEXT -> IO b -> IO b

withZeroCStruct :: (Ptr CalibratedTimestampInfoEXT -> IO b) -> IO b

pokeZeroCStruct :: Ptr CalibratedTimestampInfoEXT -> IO b -> IO b

cStructSize :: Int

cStructAlignment :: Int

Zero CalibratedTimestampInfoEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

zero :: CalibratedTimestampInfoEXT

newtype TimeDomainEXT

VkTimeDomainEXT - Supported time domains

Description

Note

An implementation supporting VK_EXT_calibrated_timestamps will use the same time domain for all its Queue so that timestamp values reported for TIME_DOMAIN_DEVICE_EXT can be matched to any timestamp captured through cmdWriteTimestamp or cmdWriteTimestamp2KHR .

struct timespec tv;
clock_gettime(CLOCK_MONOTONIC, &tv);
return tv.tv_nsec + tv.tv_sec*1000000000ull;

struct timespec tv;
clock_gettime(CLOCK_MONOTONIC_RAW, &tv);
return tv.tv_nsec + tv.tv_sec*1000000000ull;

LARGE_INTEGER counter;
QueryPerformanceCounter(&counter);
return counter.QuadPart;

See Also

CalibratedTimestampInfoEXT, getPhysicalDeviceCalibrateableTimeDomainsEXT

Constructors

TimeDomainEXT Int32

Bundled Patterns

pattern TIME_DOMAIN_DEVICE_EXT :: TimeDomainEXT

TIME_DOMAIN_DEVICE_EXT specifies the device time domain. Timestamp values in this time domain use the same units and are comparable with device timestamp values captured using cmdWriteTimestamp or cmdWriteTimestamp2KHR and are defined to be incrementing according to the timestampPeriod of the device.

pattern TIME_DOMAIN_CLOCK_MONOTONIC_EXT :: TimeDomainEXT

TIME_DOMAIN_CLOCK_MONOTONIC_EXT specifies the CLOCK_MONOTONIC time domain available on POSIX platforms. Timestamp values in this time domain are in units of nanoseconds and are comparable with platform timestamp values captured using the POSIX clock_gettime API as computed by this example:

pattern TIME_DOMAIN_CLOCK_MONOTONIC_RAW_EXT :: TimeDomainEXT

TIME_DOMAIN_CLOCK_MONOTONIC_RAW_EXT specifies the CLOCK_MONOTONIC_RAW time domain available on POSIX platforms. Timestamp values in this time domain are in units of nanoseconds and are comparable with platform timestamp values captured using the POSIX clock_gettime API as computed by this example:

pattern TIME_DOMAIN_QUERY_PERFORMANCE_COUNTER_EXT :: TimeDomainEXT

TIME_DOMAIN_QUERY_PERFORMANCE_COUNTER_EXT specifies the performance counter (QPC) time domain available on Windows. Timestamp values in this time domain are in the same units as those provided by the Windows QueryPerformanceCounter API and are comparable with platform timestamp values captured using that API as computed by this example:

Instances

Eq TimeDomainEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

(==) :: TimeDomainEXT -> TimeDomainEXT -> Bool

(/=) :: TimeDomainEXT -> TimeDomainEXT -> Bool

Ord TimeDomainEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

compare :: TimeDomainEXT -> TimeDomainEXT -> Ordering

(<) :: TimeDomainEXT -> TimeDomainEXT -> Bool

(<=) :: TimeDomainEXT -> TimeDomainEXT -> Bool

(>) :: TimeDomainEXT -> TimeDomainEXT -> Bool

(>=) :: TimeDomainEXT -> TimeDomainEXT -> Bool

max :: TimeDomainEXT -> TimeDomainEXT -> TimeDomainEXT

min :: TimeDomainEXT -> TimeDomainEXT -> TimeDomainEXT

Read TimeDomainEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

readsPrec :: Int -> ReadS TimeDomainEXT

readList :: ReadS [TimeDomainEXT]

readPrec :: ReadPrec TimeDomainEXT

readListPrec :: ReadPrec [TimeDomainEXT]

Show TimeDomainEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

showsPrec :: Int -> TimeDomainEXT -> ShowS

show :: TimeDomainEXT -> String

showList :: [TimeDomainEXT] -> ShowS

Storable TimeDomainEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

sizeOf :: TimeDomainEXT -> Int

alignment :: TimeDomainEXT -> Int

peekElemOff :: Ptr TimeDomainEXT -> Int -> IO TimeDomainEXT

pokeElemOff :: Ptr TimeDomainEXT -> Int -> TimeDomainEXT -> IO ()

peekByteOff :: Ptr b -> Int -> IO TimeDomainEXT

pokeByteOff :: Ptr b -> Int -> TimeDomainEXT -> IO ()

peek :: Ptr TimeDomainEXT -> IO TimeDomainEXT

poke :: Ptr TimeDomainEXT -> TimeDomainEXT -> IO ()

Zero TimeDomainEXT

Defined in Vulkan.Extensions.VK_EXT_calibrated_timestamps

Methods

zero :: TimeDomainEXT

type EXT_CALIBRATED_TIMESTAMPS_SPEC_VERSION = 2

pattern EXT_CALIBRATED_TIMESTAMPS_SPEC_VERSION :: forall a. Integral a => a

type EXT_CALIBRATED_TIMESTAMPS_EXTENSION_NAME = "VK_EXT_calibrated_timestamps"

pattern EXT_CALIBRATED_TIMESTAMPS_EXTENSION_NAME :: forall a. (Eq a, IsString a) => a