C Specification

To retrieve status and results for a set of queries, call:

// Provided by VK_VERSION_1_0
VkResult vkGetQueryPoolResults(
    VkDevice                                    device,
    VkQueryPool                                 queryPool,
    uint32_t                                    firstQuery,
    uint32_t                                    queryCount,
    size_t                                      dataSize,
    void*                                       pData,
    VkDeviceSize                                stride,
    VkQueryResultFlags                          flags);

Parameters

  • device is the logical device that owns the query pool.

  • queryPool is the query pool managing the queries containing the desired results.

  • firstQuery is the initial query index.

  • queryCount is the number of queries to read.

  • dataSize is the size in bytes of the buffer pointed to by pData.

  • pData is a pointer to a user-allocated buffer where the results will be written

  • stride is the stride in bytes between results for individual queries within pData.

  • flags is a bitmask of VkQueryResultFlagBits specifying how and when results are returned.

Description

The range of queries read is defined by [firstQuery, firstQuery + queryCount - 1]. For pipeline statistics queries, each query index in the pool contains one integer value for each bit that is enabled in VkQueryPoolCreateInfo::pipelineStatistics when the pool is created.

If no bits are set in flags, and all requested queries are in the available state, results are written as an array of 32-bit unsigned integer values. The behavior when not all queries are available, is described below.

If VK_QUERY_RESULT_64_BIT is not set and the result overflows a 32-bit value, the value may either wrap or saturate. Similarly, if VK_QUERY_RESULT_64_BIT is set and the result overflows a 64-bit value, the value may either wrap or saturate.

If VK_QUERY_RESULT_WAIT_BIT is set, Vulkan will wait for each query to be in the available state before retrieving the numerical results for that query. In this case, vkGetQueryPoolResults is guaranteed to succeed and return VK_SUCCESS if the queries become available in a finite time (i.e. if they have been issued and not reset). If queries will never finish (e.g. due to being reset but not issued), then vkGetQueryPoolResults may not return in finite time.

If VK_QUERY_RESULT_WAIT_BIT and VK_QUERY_RESULT_PARTIAL_BIT are both not set then no result values are written to pData for queries that are in the unavailable state at the time of the call, and vkGetQueryPoolResults returns VK_NOT_READY. However, availability state is still written to pData for those queries if VK_QUERY_RESULT_WITH_AVAILABILITY_BIT is set. Similarly, the status is still written to pData for those queries if VK_QUERY_RESULT_WITH_STATUS_BIT_KHR is set.

If VK_QUERY_RESULT_WAIT_BIT is not set, vkGetQueryPoolResults may return VK_NOT_READY if there are queries in the unavailable state.

Note

Applications must take care to ensure that use of the VK_QUERY_RESULT_WAIT_BIT bit has the desired effect.

For example, if a query has been used previously and a command buffer records the commands vkCmdResetQueryPool, vkCmdBeginQuery, and vkCmdEndQuery for that query, then the query will remain in the available state until vkResetQueryPool is called or the vkCmdResetQueryPool command executes on a queue. Applications can use fences or events to ensure that a query has already been reset before checking for its results or availability status. Otherwise, a stale value could be returned from a previous use of the query.

The above also applies when VK_QUERY_RESULT_WAIT_BIT is used in combination with VK_QUERY_RESULT_WITH_AVAILABILITY_BIT. In this case, the returned availability status may reflect the result of a previous use of the query unless vkResetQueryPool is called or the vkCmdResetQueryPool command has been executed since the last use of the query.

A similar situation can arise with the VK_QUERY_RESULT_WITH_STATUS_BIT_KHR flag.
Note

Applications can double-buffer query pool usage, with a pool per frame, and reset queries at the end of the frame in which they are read.

If VK_QUERY_RESULT_PARTIAL_BIT is set, VK_QUERY_RESULT_WAIT_BIT is not set, and the query’s status is unavailable, an intermediate result value between zero and the final result value is written to pData for that query.

If VK_QUERY_RESULT_WITH_AVAILABILITY_BIT is set, the final integer value written for each query is non-zero if the query’s status was available or zero if the status was unavailable. When VK_QUERY_RESULT_WITH_AVAILABILITY_BIT is used, implementations must guarantee that if they return a non-zero availability value then the numerical results must be valid, assuming the results are not reset by a subsequent command.

Note

Satisfying this guarantee may require careful ordering by the application, e.g. to read the availability status before reading the results.

If VK_QUERY_RESULT_WITH_STATUS_BIT_KHR is set, the final integer value written for each query indicates whether the result is available or not, and whether an error occurred. A value of zero indicates that the results are not yet available. Positive values indicate that the operations within the query completed successfully, and the query results are valid. Negative values indicate that the operations within the query completed unsuccessfully.

Specific result codes are defined by the VkQueryResultStatusKHR enumeration.

Valid Usage

  • VUID-vkGetQueryPoolResults-firstQuery-00813
    firstQuery must be less than the number of queries in queryPool

  • VUID-vkGetQueryPoolResults-flags-02828
    If VK_QUERY_RESULT_64_BIT is not set in flags and the queryType used to create queryPool was not VK_QUERY_TYPE_PERFORMANCE_QUERY_KHR, then pData and stride must be multiples of 4

  • VUID-vkGetQueryPoolResults-flags-00815
    If VK_QUERY_RESULT_64_BIT is set in flags then pData and stride must be multiples of 8

  • VUID-vkGetQueryPoolResults-queryType-03229
    If the queryType used to create queryPool was VK_QUERY_TYPE_PERFORMANCE_QUERY_KHR, then pData and stride must be multiples of the size of VkPerformanceCounterResultKHR

  • VUID-vkGetQueryPoolResults-queryType-04519
    If the queryType used to create queryPool was VK_QUERY_TYPE_PERFORMANCE_QUERY_KHR, then stride must be large enough to contain VkQueryPoolPerformanceCreateInfoKHR::counterIndexCount used to create queryPool times the size of VkPerformanceCounterResultKHR

  • VUID-vkGetQueryPoolResults-firstQuery-00816
    The sum of firstQuery and queryCount must be less than or equal to the number of queries in queryPool

  • VUID-vkGetQueryPoolResults-dataSize-00817
    dataSize must be large enough to contain the result of each query, as described here

  • VUID-vkGetQueryPoolResults-queryType-00818
    If the queryType used to create queryPool was VK_QUERY_TYPE_TIMESTAMP, flags must not contain VK_QUERY_RESULT_PARTIAL_BIT

  • VUID-vkGetQueryPoolResults-queryType-03230
    If the queryType used to create queryPool was VK_QUERY_TYPE_PERFORMANCE_QUERY_KHR, flags must not contain VK_QUERY_RESULT_WITH_AVAILABILITY_BIT, VK_QUERY_RESULT_PARTIAL_BIT or VK_QUERY_RESULT_64_BIT

  • VUID-vkGetQueryPoolResults-queryType-03231
    If the queryType used to create queryPool was VK_QUERY_TYPE_PERFORMANCE_QUERY_KHR, the queryPool must have been recorded once for each pass as retrieved via a call to vkGetPhysicalDeviceQueueFamilyPerformanceQueryPassesKHR

  • VUID-vkGetQueryPoolResults-queryType-04810
    If the queryType used to create queryPool was VK_QUERY_TYPE_RESULT_STATUS_ONLY_KHR, flags must include VK_QUERY_RESULT_WITH_STATUS_BIT_KHR

  • VUID-vkGetQueryPoolResults-flags-04811
    If flags includes VK_QUERY_RESULT_WITH_STATUS_BIT_KHR, it must not include VK_QUERY_RESULT_WITH_AVAILABILITY_BIT

Valid Usage (Implicit)

  • VUID-vkGetQueryPoolResults-device-parameter
    device must be a valid VkDevice handle

  • VUID-vkGetQueryPoolResults-queryPool-parameter
    queryPool must be a valid VkQueryPool handle

  • VUID-vkGetQueryPoolResults-pData-parameter
    pData must be a valid pointer to an array of dataSize bytes

  • VUID-vkGetQueryPoolResults-flags-parameter
    flags must be a valid combination of VkQueryResultFlagBits values

  • VUID-vkGetQueryPoolResults-dataSize-arraylength
    dataSize must be greater than 0

  • VUID-vkGetQueryPoolResults-queryPool-parent
    queryPool must have been created, allocated, or retrieved from device

Return Codes
On success, this command returns

  • VK_SUCCESS

  • VK_NOT_READY

On failure, this command returns

  • VK_ERROR_OUT_OF_HOST_MEMORY

  • VK_ERROR_OUT_OF_DEVICE_MEMORY

  • VK_ERROR_DEVICE_LOST

See Also

VK_VERSION_1_0, VkDevice, VkDeviceSize, VkQueryPool, VkQueryResultFlags

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 2014-2022 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0