vkCmdBeginQuery(3)

Name

vkCmdBeginQuery - Begin a query

C Specification

To begin a query, call:

// Provided by VK_VERSION_1_0
void vkCmdBeginQuery(
    VkCommandBuffer                             commandBuffer,
    VkQueryPool                                 queryPool,
    uint32_t                                    query,
    VkQueryControlFlags                         flags);

Parameters

  • commandBuffer is the command buffer into which this command will be recorded.

  • queryPool is the query pool that will manage the results of the query.

  • query is the query index within the query pool that will contain the results.

  • flags is a bitmask of VkQueryControlFlagBits specifying constraints on the types of queries that can be performed.

Description

If the queryType of the pool is VK_QUERY_TYPE_OCCLUSION and flags contains VK_QUERY_CONTROL_PRECISE_BIT, an implementation must return a result that matches the actual number of samples passed. This is described in more detail in Occlusion Queries.

Calling vkCmdBeginQuery is equivalent to calling vkCmdBeginQueryIndexedEXT with the index parameter set to zero.

After beginning a query, that query is considered active within the command buffer it was called in until that same query is ended. Queries active in a primary command buffer when secondary command buffers are executed are considered active for those secondary command buffers.

Furthermore, if the query is started within a video coding scope, the following command buffer states are initialized for the query type:

  • The active_query_index is set to the value specified by query.

  • The last activatable query index is also set to the value specified by query.

Each video coding operation stores a result to the query corresponding to the current active query index, followed by incrementing the active query index. If the active query index gets incremented past the last activatable query index, issuing any further video coding operations results in undefined behavior.

In practice, this means that currently no more than a single video coding operation must be issued between a begin and end query pair.

This command defines an execution dependency between other query commands that reference the same query.

The first synchronization scope includes all commands which reference the queries in queryPool indicated by query that occur earlier in submission order.

The second synchronization scope includes all commands which reference the queries in queryPool indicated by query that occur later in submission order.

The operation of this command happens after the first scope and happens before the second scope.

If the queryType of the pool is VK_QUERY_TYPE_TIME_ELAPSED_QCOM, this command also defines an execution dependency on commands that were submitted before it, and starting the timer.

The first synchronization scope includes all commands that occur earlier in submission order.

The second synchronization scope includes only the starting of the timer.

Valid Usage
Valid Usage (Implicit)

  • VUID-vkCmdBeginQuery-commandBuffer-parameter
    commandBuffer must be a valid VkCommandBuffer handle

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

  • VUID-vkCmdBeginQuery-flags-parameter
    flags must be a valid combination of VkQueryControlFlagBits values

  • VUID-vkCmdBeginQuery-commandBuffer-recording
    commandBuffer must be in the recording state

  • VUID-vkCmdBeginQuery-commandBuffer-cmdpool
    The VkCommandPool that commandBuffer was allocated from must support VK_QUEUE_COMPUTE_BIT, VK_QUEUE_GRAPHICS_BIT, VK_QUEUE_VIDEO_DECODE_BIT_KHR, or VK_QUEUE_VIDEO_ENCODE_BIT_KHR operations

  • VUID-vkCmdBeginQuery-suspended
    This command must not be called between suspended render pass instances

  • VUID-vkCmdBeginQuery-commonparent
    Both of commandBuffer, and queryPool must have been created, allocated, or retrieved from the same VkDevice

Host Synchronization

  • Host access to commandBuffer must be externally synchronized

  • Host access to the VkCommandPool that commandBuffer was allocated from must be externally synchronized

Command Properties
Command Buffer Levels Render Pass Scope Video Coding Scope Supported Queue Types Command Type

Primary
Secondary

Both

Both

VK_QUEUE_COMPUTE_BIT
VK_QUEUE_GRAPHICS_BIT
VK_QUEUE_VIDEO_DECODE_BIT_KHR
VK_QUEUE_VIDEO_ENCODE_BIT_KHR

Action
State
Conditional Rendering

vkCmdBeginQuery is not affected by conditional rendering

See Also

VK_VERSION_1_0, VkCommandBuffer, VkQueryControlFlags, VkQueryPool, vkCmdBeginQueryIndexedEXT, vkCmdEndQuery, vkCmdEndQueryIndexedEXT

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.