// Copyright (c) 2015-2016 The Khronos Group Inc. // Copyright notice at https://www.khronos.org/registry/speccopyright.html [[queries]] = Queries _Queries_ provide a mechanism to return information about the processing of a sequence of {apiname} commands. Query operations are asynchronous, and as such, their results are not returned immediately. Instead, their results, and their availability status, are stored in a <>. The state of these queries can: be read back on the host, or copied to a buffer object on the device. The supported query types are <>, <>, and <>. [[queries-pools]] == Query Pools Queries are managed using _query pool_ objects. Each query pool is a collection of a specific number of queries of a particular type. To create a query pool, call: include::../protos/vkCreateQueryPool.txt[] * pname:device is the logical device that creates the query pool. * pname:pCreateInfo is a pointer to an instance of the sname:VkQueryPoolCreateInfo structure containing the number and type of queries to be managed by the pool. * pname:pAllocator controls host memory allocation as described in the <> chapter. * pname:pQueryPool is a pointer to a sname:VkQueryPool handle in which the resulting query pool object is returned. include::../validity/protos/vkCreateQueryPool.txt[] The definition of sname:VkQueryPoolCreateInfo is: include::../structs/VkQueryPoolCreateInfo.txt[] The members of sname:VkQueryPoolCreateInfo have the following meanings: * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:flags is reserved for future use. * pname:queryType is the type of queries managed by the pool, and must: be one of the values + include::../enums/VkQueryType.txt[] * pname:queryCount is the number of queries managed by the pool. * pname:pipelineStatistics is a bitmask indicating which counters will be returned in queries on the new pool, as described below in <>. pname:pipelineStatistics is ignored if pname:queryType is not ename:VK_QUERY_TYPE_PIPELINE_STATISTICS. include::../validity/structs/VkQueryPoolCreateInfo.txt[] To destroy a query pool, call: include::../protos/vkDestroyQueryPool.txt[] * pname:device is the logical device that destroys the query pool. * pname:queryPool is the query pool to destroy. * pname:pAllocator controls host memory allocation as described in the <> chapter. include::../validity/protos/vkDestroyQueryPool.txt[] [[queries-operation]] == Query Operation The operation of queries is controlled by the commands flink:vkCmdBeginQuery, flink:vkCmdEndQuery, flink:vkCmdResetQueryPool, flink:vkCmdCopyQueryPoolResults, and flink:vkCmdWriteTimestamp. In order for a sname:VkCommandBuffer to record query management commands, the queue family for which its sname:VkCommandPool was created must: support the appropriate type of operations (graphics, compute) suitable for the query type of a given query pool. Each query in a query pool has a status that is either _unavailable_ or _available_, and also has state to store the numerical results of a query operation of the type requested when the query pool was created. Resetting a query via flink:vkCmdResetQueryPool sets the status to unavailable and makes the numerical results undefined. Performing a query operation with flink:vkCmdBeginQuery and flink:vkCmdEndQuery changes the status to available when the query <>, and updates the numerical results. Both the availability status and numerical results are retrieved by calling either flink:vkGetQueryPoolResults or flink:vkCmdCopyQueryPoolResults. All query commands execute in order and are guaranteed to see the effects of each other's memory accesses, with one significant exception: fname:vkCmdCopyQueryPoolResults may: execute before the results of fname:vkCmdEndQuery are available. However, if ename:VK_QUERY_RESULT_WAIT_BIT is used, then fname:vkCmdCopyQueryPoolResults must: reflect the result of any previously executed queries. Other sequences of commands, such as fname:vkCmdResetQueryPool followed by fname:vkCmdBeginQuery, must: make the effects of the first command visible to the second command. After query pool creation, each query is in an undefined state and must: be reset prior to use. Queries must: also be reset between uses. Using a query that has not been reset will result in undefined behavior. To reset a range of queries in a query pool, call: include::../protos/vkCmdResetQueryPool.txt[] * pname:commandBuffer is the command buffer into which this command will be recorded. * pname:queryPool is the handle of the query pool managing the queries being reset. * pname:firstQuery is the initial query index to reset. * pname:queryCount is the number of queries to reset. When executed on a queue, this command sets the status of query indices latexmath:[$firstQuery,firstQuery+queryCount-1$] to unavailable. include::../validity/protos/vkCmdResetQueryPool.txt[] Once queries are reset and ready for use, query commands can: be issued to a command buffer. Occlusion queries and pipeline statistics queries count events - drawn samples and pipeline stage invocations, respectively - resulting from commands that are recorded between a flink:vkCmdBeginQuery command and a flink:vkCmdEndQuery command within a specified command buffer, effectively scoping a set of drawing and/or compute commands. Timestamp queries write timestamps to a query pool. A query must: begin and end in the same command buffer, although if it is a primary command buffer, and the <> feature is enabled, it can: execute secondary command buffers during the query operation. For a secondary command buffer to be executed while a query is active, it must: set the pname:occlusionQueryEnable, pname:queryFlags, and/or pname:pipelineStatistics members of slink:VkCommandBufferBeginInfo to conservative values, as described in the <> section. A query must: either begin and end inside the same subpass of a render pass instance, or must: both begin and end outside of a render pass instance (i.e. contain entire render pass instances). Begin a query by calling: include::../protos/vkCmdBeginQuery.txt[] * pname:commandBuffer is the command buffer into which this command will be recorded. * pname:queryPool is the query pool that will manage the results of the query. * pname:query is the query index within the query pool that will contain the results. * pname:flags is a bitmask indicating constraints on the types of queries that can: be performed. Valid bits in pname:flags include: + include::../enums/VkQueryControlFlagBits.txt[] If the pname:queryType of the pool is ename:VK_QUERY_TYPE_OCCLUSION and pname:flags contains ename: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 <>. include::../validity/protos/vkCmdBeginQuery.txt[] [[queries-operation-active]] 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. After the set of desired draw or dispatch commands, end a query by calling: include::../protos/vkCmdEndQuery.txt[] * pname:commandBuffer is the command buffer into which this command will be recorded. * pname:queryPool is the query pool that is managing the results of the query. * pname:query is the query index within the query pool where the result is stored. include::../validity/protos/vkCmdEndQuery.txt[] [[queries-operation-finished]] As queries operate asynchronously, ending a query does not immediately set the query's status to available. A query is considered _finished_ when the final results of the query are ready to be retrieved by flink:vkGetQueryPoolResults and flink:vkCmdCopyQueryPoolResults, and this is when the query's status is set to available. Once a query is ended the query must: finish in finite time, unless the state of the query is changed using other commands, e.g. by issuing a reset of the query. [[queries-operation-memorylayout]] An application can: retrieve results either by requesting they be written into application-provided memory, or by requesting they be copied into a sname:VkBuffer. In either case, the layout in memory is defined as follows: * The first query's result is written starting at the first byte requested by the command, and each subsequent query's result begins pname:stride bytes later. * Each query's result is a tightly packed array of unsigned integers, either 32- or 64-bits as requested by the command, storing the numerical results and, if requested, the availability status. * If ename:VK_QUERY_RESULT_WITH_AVAILABILITY_BIT is used, the final element of each query's result is an integer indicating whether the query's result is available, with any non-zero value indicating that it is available. * Occlusion queries write one integer value - the number of samples passed. Pipeline statistics queries write one integer value for each bit that is enabled in the pname:pipelineStatistics when the pool is created, and the statistics values are written in bit order starting from the least significant bit. Timestamps write one integer value. * If more than one query is retrieved and pname:stride is not at least as large as the size of the array of integers corresponding to a single query, the values written to memory are undefined. To retrieve status and results for a set of queries, call: include::../protos/vkGetQueryPoolResults.txt[] * pname:device is the logical device that owns the query pool. * pname:queryPool is the query pool managing the queries containing the desired results. * pname:firstQuery is the initial query index. * pname:queryCount is the number of queries. pname:firstQuery and pname:queryCount together define a range of queries. * pname:dataSize is the size in bytes of the buffer pointed to by pname:pData. * pname:pData is a pointer to a user-allocated buffer where the results will be written * pname:stride is the stride in bytes between results for individual queries within pname:pData. * pname:flags is a bitmask of elink:VkQueryResultFlagBits specifying how and when results are returned. Valid bits in pname:flags include: include::../enums/VkQueryResultFlagBits.txt[] These bits have the following meanings: * ename:VK_QUERY_RESULT_64_BIT indicates the results will be written as an array of 64-bit unsigned integer values. If this bit is not set, the results will be written as an array of 32-bit unsigned integer values. * ename:VK_QUERY_RESULT_WAIT_BIT indicates that {apiname} will wait for each query's status to become available before retrieving its results. * ename:VK_QUERY_RESULT_WITH_AVAILABILITY_BIT indicates that the availability status accompanies the results. * ename:VK_QUERY_RESULT_PARTIAL_BIT indicates that returning partial results is acceptable. If no bits are set in pname: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 <>. If ename: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 ename:VK_QUERY_RESULT_64_BIT is set and the result overflows a 64-bit value, the value may: either wrap or saturate. If ename:VK_QUERY_RESULT_WAIT_BIT is set, {apiname} will wait for each query to be in the available state before retrieving the numerical results for that query. In this case, fname:vkGetQueryPoolResults is guaranteed to succeed and return ename: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 fname:vkGetQueryPoolResults maynot: return in finite time. [[queries-wait-bit-not-set]] If ename:VK_QUERY_RESULT_WAIT_BIT and ename:VK_QUERY_RESULT_PARTIAL_BIT are both not set then no result values are written to pname:pData for queries that are in the unavailable state at the time of the call, and fname:vkGetQueryPoolResults returns ename:VK_NOT_READY. However, availability state is still written to pname:pData for those queries if ename:VK_QUERY_RESULT_WITH_AVAILABILITY_BIT is set. [NOTE] .Note ==== Applications must: take care to ensure that use of the ename: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 fname:vkCmdResetQueryPool, fname:vkCmdBeginQuery, and fname:vkCmdEndQuery for that query, then the query will remain in the available state until the fname:vkCmdResetQueryPool command executes on a queue. Applications can: use fences or events to ensure that an 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 ename:VK_QUERY_RESULT_WAIT_BIT is used in combination with ename: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 the fname:vkCmdResetQueryPool command has been executed since the last use of the query. ==== [NOTE] .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 ename:VK_QUERY_RESULT_PARTIAL_BIT is set, ename: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 pname:pData for that query. ename:VK_QUERY_RESULT_PARTIAL_BIT mustnot: be used if the pool's pname:queryType is ename:VK_QUERY_TYPE_TIMESTAMP. If ename: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 ename: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] .Note ==== Satisfying this guarantee may: require careful ordering by the application, e.g. to read the availability status before reading the results. ==== include::../validity/protos/vkGetQueryPoolResults.txt[] To copy query statuses and numerical results directly to buffer memory, call: include::../protos/vkCmdCopyQueryPoolResults.txt[] * pname:commandBuffer is the command buffer into which this command will be recorded. * pname:queryPool is the query pool managing the queries containing the desired results. * pname:firstQuery is the initial query index. * pname:queryCount is the number of queries. pname:firstQuery and pname:queryCount together define a range of queries. * pname:dstBuffer is a sname:VkBuffer object that will receive the results of the copy command. * pname:dstOffset is an offset into pname:dstBuffer. * pname:stride is the stride in bytes between results for individual queries within pname:dstBuffer. The required size of the backing memory for pname:dstBuffer is determined as described above for flink:vkGetQueryPoolResults. * pname:flags is a bitmask of elink:VkQueryResultFlagBits specifying how and when results are returned. fname:vkCmdCopyQueryPoolResults is guaranteed to see the effect of previous uses of fname:vkCmdResetQueryPool in the same queue, without any additional synchronization. Thus, the results will always reflect the most recent use of the query. pname:flags has the same possible values described above for the pname:flags parameter of flink:vkGetQueryPoolResults, but the different style of execution causes some subtle behavioral differences. Because fname:vkCmdCopyQueryPoolResults executes in order with respect to other query commands, there is less ambiguity about which use of a query is being requested. If no bits are set in pname:flags, results for all requested queries in the available state are written as 32-bit unsigned integer values, and nothing is written for queries in the unavailable state. If ename:VK_QUERY_RESULT_64_BIT is set, the results are written as an array of 64-bit unsigned integer values as described for flink:vkGetQueryPoolResults. If ename:VK_QUERY_RESULT_WAIT_BIT is set, the implementation will wait for each query's status to be in the available state before retrieving the numerical results for that query. This is guaranteed to reflect the most recent use of the query on the same queue, assuming that the query is not being simultaneously used by other queues. If the query does not become available in a finite amount of time (e.g. due to not issuing a query since the last reset), a ename:VK_ERROR_DEVICE_LOST error may: occur. Similarly, if ename:VK_QUERY_RESULT_WITH_AVAILABILITY_BIT is set and ename:VK_QUERY_RESULT_WAIT_BIT is not set, the availability is guaranteed to reflect the most recent use of the query on the same queue, assuming that the query is not being simultaneously used by other queues. As with fname:vkGetQueryPoolResults, implementations must: guarantee that if they return a non-zero availability value, then the numerical results are valid. If ename:VK_QUERY_RESULT_PARTIAL_BIT is set, ename: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 for that query. ename:VK_QUERY_RESULT_PARTIAL_BIT mustnot: be used if the pool's pname:queryType is ename:VK_QUERY_TYPE_TIMESTAMP. fname:vkCmdCopyQueryPoolResults is considered to be a transfer operation, and its writes to buffer memory must: be synchronized using ename:VK_PIPELINE_STAGE_TRANSFER_BIT and ename:VK_ACCESS_TRANSFER_WRITE_BIT before using the results. include::../validity/protos/vkCmdCopyQueryPoolResults.txt[] [[queries-operation-undefined]] Rendering operations such as clears, MSAA resolves, attachment load/store operations, and blits may: or maynot: count towards the results of queries. This behavior is implementation-dependent and may: vary depending on the path used within an implementation. For example, some implementations have several types of clears, some of which may: include vertices and some not. [[queries-occlusion]] == Occlusion Queries Occlusion queries track the number of samples that pass the per-fragment tests for a set of drawing commands. As such, occlusion queries are only available on queue families supporting graphics operations. The application can: then use these results to inform future rendering decisions. An occlusion query is begun and ended by calling fname:vkCmdBeginQuery and fname:vkCmdEndQuery, respectively. When an occlusion query begins, the count of passing samples always starts at zero. For each drawing command, the count is incremented as described in <>. If pname:flags does not contain ename:VK_QUERY_CONTROL_PRECISE_BIT an implementation may: generate any non-zero result value for the query if the count of passing samples is non-zero. [NOTE] .Note ==== Not setting ename:VK_QUERY_CONTROL_PRECISE_BIT mode may: be more efficient on some implementations, and should: be used where it is sufficient to know a boolean result on whether any samples passed the per-fragment tests. In this case, some implementations may: only return zero or one, indifferent to the actual number of samples passing the per-fragment tests. ==== When an occlusion query finishes, the result for that query is marked as available. The application can: then either copy the result to a buffer (via fname:vkCmdCopyQueryPoolResults) or request it be put into host memory (via fname:vkGetQueryPoolResults). [NOTE] .Note ==== If occluding geometry is not drawn first, samples can: pass the depth test, but still not be visible in a final image. ==== [[queries-pipestats]] == Pipeline Statistics Queries Pipeline statistics queries allow the application to sample a specified set of sname:VkPipeline counters. These counters are accumulated by {apiname} for a set of either draw or dispatch commands while a pipeline statistics query is active. As such, pipeline statistics queries are available on queue families supporting either graphics or compute operations. Further, the availability of pipeline statistics queries is indicated by the pname:pipelineStatisticsQuery member of the sname:VkPhysicalDeviceFeatures object (see fname:vkGetPhysicalDeviceFeatures and fname:vkCreateDevice for detecting and requesting this query type on a sname:VkDevice). A pipeline statistics query is begun and ended by calling fname:vkCmdBeginQuery and fname:vkCmdEndQuery, respectively. When a pipeline statistics query begins, all statistics counters are set to zero. While the query is active, the pipeline type determines which set of statistics are available, but these must: be configured on the query pool when it is created. If a statistic counter is issued on a command buffer that does not support the corresponding operation, the value of that counter is undefined after the query has finished. At least one statistic counter relevant to the operations supported on the recording command buffer must: be enabled. pname:pipelineStatisticsQuery is a bitmask indicating different possible pipeline statistics. Valid bits in pname:flags include: include::../enums/VkQueryPipelineStatisticFlagBits.txt[] These bits have the following meanings: * If ename:VK_QUERY_PIPELINE_STATISTIC_INPUT_ASSEMBLY_VERTICES_BIT is set, queries managed by the pool will count the number of vertices processed by the <> stage. Vertices corresponding to incomplete primitives may: or maynot: contribute to the count. * If ename:VK_QUERY_PIPELINE_STATISTIC_INPUT_ASSEMBLY_PRIMITIVES_BIT is set, queries managed by the pool will count the number of primitives processed by the <> stage. If primitive restart is enabled, restarting the primitive topology has no effect on the count. Incomplete primitives may: or maynot: be counted. * If ename:VK_QUERY_PIPELINE_STATISTIC_VERTEX_SHADER_INVOCATIONS_BIT is set, queries managed by the pool will count the number of vertex shader invocations. This counter's value is incremented each time a vertex shader is <>. * If ename:VK_QUERY_PIPELINE_STATISTIC_GEOMETRY_SHADER_INVOCATIONS_BIT is set, queries managed by the pool will count the number of geometry shader invocations. This counter's value is incremented each time a geometry shader is <>. In the case of <>, the geometry shader invocations count is incremented for each separate instanced invocation. * If ename:VK_QUERY_PIPELINE_STATISTIC_GEOMETRY_SHADER_PRIMITIVES_BIT is set, queries managed by the pool will count the number of primitives generated by geometry shader invocations. The counter's value is incremented each time the geometry shader emits a primitive. Restarting primitive topology using the SPIR-V instructions code:OpEndPrimitive or code:OpEndStreamPrimitive has no effect on the geometry shader output primitives count. * If ename:VK_QUERY_PIPELINE_STATISTIC_CLIPPING_INVOCATIONS_BIT is set, queries managed by the pool will count the number of primitives processed by the <> stage of the pipeline. The counter's value is incremented each time a primitive reaches the primitive clipping stage. * If ename:VK_QUERY_PIPELINE_STATISTIC_CLIPPING_PRIMITIVES_BIT is set, queries managed by the pool will count the number of primitives output by the <> stage of the pipeline. The counter's value is incremented each time a primitive passes the primitive clipping stage. The actual number of primitives output by the primitive clipping stage for a particular input primitive is implementation-dependent but must: satisfy the following conditions: ** If at least one vertex of the input primitive lies inside the clipping volume, the counter is incremented by one or more. ** Otherwise, the counter is incremented by zero or more. * If ename:VK_QUERY_PIPELINE_STATISTIC_FRAGMENT_SHADER_INVOCATIONS_BIT is set, queries managed by the pool will count the number of fragment shader invocations. The counter's value is incremented each time the fragment shader is <>. * If ename:VK_QUERY_PIPELINE_STATISTIC_TESSELLATION_CONTROL_SHADER_PATCHES_BIT is set, queries managed by the pool will count the number of patches processed by the tessellation control shader. The counter's value is incremented once for each patch for which a tessellation control shader is <>. * If ename:VK_QUERY_PIPELINE_STATISTIC_TESSELLATION_EVALUATION_SHADER_INVOCATIONS_BIT is set, queries managed by the pool will count the number of invocations of the tessellation evaluation shader. The counter's value is incremented each time the tessellation evaluation shader is <>. * If ename:VK_QUERY_PIPELINE_STATISTIC_COMPUTE_SHADER_INVOCATIONS_BIT is set, queries managed by the pool will count the number of compute shader invocations. The counter's value is incremented every time the compute shader is invoked. Implementations may: skip the execution of certain compute shader invocations or execute additional compute shader invocations for implementation-dependent reasons as long as the results of rendering otherwise remain unchanged. These values are intended to measure relative statistics on one implementation. Various device architectures will count these values differently. Any or all counters may: be affected by the issues described in <>. [NOTE] .Note ==== For example, tile-based rendering devices may: need to replay the scene multiple times, affecting some of the counts. ==== If a pipeline has pname:rasterizerDiscardEnable enabled, implementations may: discard primitives after the final vertex processing stage. As a result, if pname:rasterizerDiscardEnable is enabled, the clipping input and output primitives counters maynot: be incremented. When a pipeline statistics query finishes, the result for that query is marked as available. The application can: copy the result to a buffer (via fname:vkCmdCopyQueryPoolResults), or request it be put into host memory (via fname:vkGetQueryPoolResults). [[queries-timestamps]] == Timestamp Queries _Timestamps_ provide applications with a mechanism for timing the execution of commands. A timestamp is an integer value generated by the sname:VkPhysicalDevice. Unlike other queries, timestamps do not operate over a range, and so do not use flink:vkCmdBeginQuery or flink:vkCmdEndQuery. The mechanism is built around a set of commands that allow the application to tell the sname:VkPhysicalDevice to write timestamp values to a <> and then either read timestamp values on the host (using flink:vkGetQueryPoolResults) or copy timestamp values to a sname:VkBuffer (using flink:vkCmdCopyQueryPoolResults). The application can: then compute differences between timestamps to determine execution time. The number of valid bits in a timestamp value is determined by the sname:VkQueueFamilyProperties::pname:timestampValidBits property of the queue on which the timestamp is written. Timestamps are supported on any queue which reports a non-zero value for pname:timestampValidBits via flink:vkGetPhysicalDeviceQueueFamilyProperties. If the <> limit is ename:VK_TRUE, timestamps are supported by every queue family that supports either graphics or compute operations (see slink:VkQueueFamilyProperties). The number of nanoseconds it takes for a timestamp value to be incremented by 1 can: be obtained from sname:VkPhysicalDeviceLimits::pname:timestampPeriod after a call to fname:vkGetPhysicalDeviceProperties. A timestamp is requested by calling: include::../protos/vkCmdWriteTimestamp.txt[] * pname:commandBuffer is the command buffer into which the command will be recorded. * pname:pipelineStage is one of the elink:VkPipelineStageFlagBits, specifying a stage of the pipeline. * pname:queryPool is the query pool that will manage the timestamp. * pname:query is the query within the query pool that will contain the timestamp. fname:vkCmdWriteTimestamp latches the value of the timer when all previous commands have completed executing as far as the specified pipeline stage, and writes the timestamp value to memory. When the timestamp value is written, the availability status of the query is set to available. [NOTE] .Note ==== If an implementation is unable to detect completion and latch the timer at any specific stage of the pipeline, it may: instead do so at any logically later stage. ==== flink:vkCmdCopyQueryPoolResults can: then be called to copy the timestamp value from the query pool into buffer memory, with ordering and synchronization behavior equivalent to how other queries operate. Timestamp values can: also be retrieved from the query pool using flink:vkGetQueryPoolResults. As with other queries, the query must: be reset using flink:vkCmdResetQueryPool before requesting the timestamp value be written to it. While fname:vkCmdWriteTimestamp can: be called inside or outside of a render pass instance, flink:vkCmdCopyQueryPoolResults must: only be called outside of a render pass instance. include::../validity/protos/vkCmdWriteTimestamp.txt[]