Registered Extension Number

117

Revision

1

Extension and Version Dependencies

Other Extension Metadata

Last Modified Date

2019-10-08

IP Status

No known IP claims.

Contributors
  • Jesse Barker, Unity Technologies

  • Kenneth Benzie, Codeplay

  • Jan-Harald Fredriksen, ARM

  • Jeff Leger, Qualcomm

  • Jesse Hall, Google

  • Tobias Hector, AMD

  • Neil Henning, Codeplay

  • Baldur Karlsson

  • Lionel Landwerlin, Intel

  • Peter Lohrmann, AMD

  • Alon Or-bach, Samsung

  • Daniel Rakos, AMD

  • Niklas Smedberg, Unity Technologies

  • Igor Ostrowski, Intel

Description

The VK_KHR_performance_query extension adds a mechanism to allow querying of performance counters for use in applications and by profiling tools.

Each queue family may expose counters that can be enabled on a queue of that family. We extend VkQueryType to add a new query type for performance queries, and chain a structure on VkQueryPoolCreateInfo to specify the performance queries to enable.

New Object Types

None.

New Enum Constants

  • Extending VkStructureType:

    • VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_PERFORMANCE_QUERY_FEATURES_KHR

    • VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_PERFORMANCE_QUERY_PROPERTIES_KHR

    • VK_STRUCTURE_TYPE_PERFORMANCE_COUNTER_KHR

    • VK_STRUCTURE_TYPE_PERFORMANCE_COUNTER_DESCRIPTION_KHR

    • VK_STRUCTURE_TYPE_QUERY_POOL_PERFORMANCE_CREATE_INFO_KHR

    • VK_STRUCTURE_TYPE_PERFORMANCE_QUERY_SUBMIT_INFO_KHR

    • VK_STRUCTURE_TYPE_ACQUIRE_PROFILING_LOCK_INFO_KHR

  • Extending VkQueryType:

    • VK_QUERY_TYPE_PERFORMANCE_QUERY_KHR

Issues

1) Should this extension include a mechanism to begin a query in command buffer A and end the query in command buffer B?

RESOLVED No - queries are tied to command buffer creation and thus have to be encapsulated within a single command buffer.

2) Should this extension include a mechanism to begin and end queries globally on the queue, not using the existing command buffer commands?

RESOLVED No - for the same reasoning as the resolution of 1).

3) Should this extension expose counters that require multiple passes?

RESOLVED Yes - users should re-submit a command buffer with the same commands in it multiple times, specifying the pass to count as the query parameter in VkPerformanceQuerySubmitInfoKHR.

4) How to handle counters across parallel workloads?

RESOLVED In the spirit of Vulkan, a counter description flag VK_PERFORMANCE_COUNTER_DESCRIPTION_CONCURRENTLY_IMPACTED_KHR denotes that the accuracy of a counter result is affected by parallel workloads.

5) How to handle secondary command buffers?

RESOLVED Secondary command buffers inherit any counter pass index specified in the parent primary command buffer. Note: this is no longer an issue after change from issue 10 resolution

6) What commands does the profiling lock have to be held for?

RESOLVED For any command buffer that is being queried with a performance query pool, the profiling lock must be held while that command buffer is in the recording, executable, or pending state.

7) Should we support vkCmdCopyQueryPoolResults?

RESOLVED Yes.

8) Should we allow performance queries to interact with multiview?

RESOLVED Yes, but the performance queries must be performed once for each pass per view.

9) Should a queryCount > 1 be usable for performance queries?

RESOLVED Yes. Some vendors will have costly performance counter query pool creation, and would rather if a certain set of counters were to be used multiple times that a queryCount > 1 can be used to amortize the instantiation cost.

10) Should we introduce an indirect mechanism to set the counter pass index?

RESOLVED Specify the counter pass index at submit time instead to avoid requiring re-recording of command buffers when multiple counter passes needed.

Examples

The following example shows how to find what performance counters a queue family supports, setup a query pool to record these performance counters, how to add the query pool to the command buffer to record information, and how to get the results from the query pool.

// A previously created physical device
VkPhysicalDevice physicalDevice;

// One of the queue families our device supports
uint32_t queueFamilyIndex;

uint32_t counterCount;

// Get the count of counters supported
vkEnumeratePhysicalDeviceQueueFamilyPerformanceQueryCountersKHR(
  physicalDevice,
  queueFamilyIndex,
  &counterCount,
  NULL,
  NULL);

VkPerformanceCounterKHR* counters =
  malloc(sizeof(VkPerformanceCounterKHR) * counterCount);
VkPerformanceCounterDescriptionKHR* counterDescriptions =
  malloc(sizeof(VkPerformanceCounterDescriptionKHR) * counterCount);

// Get the counters supported
vkEnumeratePhysicalDeviceQueueFamilyPerformanceQueryCountersKHR(
  physicalDevice,
  queueFamilyIndex,
  &counterCount,
  counters,
  counterDescriptions);

// Try to enable the first 8 counters
uint32_t enabledCounters[8];

const uint32_t enabledCounterCount = min(counterCount, 8));

for (uint32_t i = 0; i < enabledCounterCount; i++) {
  enabledCounters[i] = i;
}

// A previously created device that had the performanceCounterQueryPools feature
// set to VK_TRUE
VkDevice device;

VkQueryPoolPerformanceCreateInfoKHR performanceQueryCreateInfo = {
  VK_STRUCTURE_TYPE_QUERY_POOL_PERFORMANCE_CREATE_INFO_KHR,
  NULL,

  // Specify the queue family that this performance query is performed on
  queueFamilyIndex,

  // The number of counters to enable
  enabledCounterCount,

  // The array of indices of counters to enable
  enabledCounters
};


// Get the number of passes our counters will require.
uint32_t numPasses;

vkGetPhysicalDeviceQueueFamilyPerformanceQueryPassesKHR(
  physicalDevice,
  &performanceQueryCreateInfo,
  &numPasses);

VkQueryPoolCreateInfo queryPoolCreateInfo = {
  VK_STRUCTURE_TYPE_QUERY_POOL_CREATE_INFO,
  &performanceQueryCreateInfo,
  0,

  // Using our new query type here
  VK_QUERY_TYPE_PERFORMANCE_QUERY_KHR,

  1,

  0
};

VkQueryPool queryPool;

VkResult result = vkCreateQueryPool(
  device,
  &queryPoolCreateInfo,
  NULL,
  &queryPool);

assert(VK_SUCCESS == result);

// A queue from queueFamilyIndex
VkQueue queue;

// A command buffer we want to record counters on
VkCommandBuffer commandBuffer;

VkCommandBufferBeginInfo commandBufferBeginInfo = {
  VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO,
  NULL,
  0,
  NULL
};

VkAcquireProfilingLockInfoKHR lockInfo = {
  VK_STRUCTURE_TYPE_ACQUIRE_PROFILING_LOCK_INFO_KHR,
  NULL,
  0,
  UINT64_MAX // Wait forever for the lock
};

// Acquire the profiling lock before we record command buffers
// that will use performance queries

result = vkAcquireProfilingLockKHR(device, &lockInfo);

assert(VK_SUCCESS == result);

result = vkBeginCommandBuffer(commandBuffer, &commandBufferBeginInfo);

assert(VK_SUCCESS == result);

vkCmdResetQueryPool(
  commandBuffer,
  queryPool,
  0,
  1);

vkCmdBeginQuery(
  commandBuffer,
  queryPool,
  0,
  0);

// Perform the commands you want to get performance information on
// ...

// Perform a barrier to ensure all previous commands were complete before
// ending the query
vkCmdPipelineBarrier(commandBuffer,
  VK_PIPELINE_STAGE_BOTTOM_OF_PIPE_BIT,
  VK_PIPELINE_STAGE_BOTTOM_OF_PIPE_BIT,
  0,
  0,
  NULL,
  0,
  NULL,
  0,
  NULL);

vkCmdEndQuery(
  commandBuffer,
  queryPool,
  0);

result = vkEndCommandBuffer(commandBuffer);

assert(VK_SUCCESS == result);

for (uint32_t counterPass = 0; counterPass < numPasses; counterPass++) {

  VkPerformanceQuerySubmitInfoKHR performanceQuerySubmitInfo = {
    VK_STRUCTURE_TYPE_PERFORMANCE_QUERY_SUBMIT_INFO_KHR,
    NULL,
    counterPass
  };


  // Submit the command buffer and wait for its completion
  // ...
}

// Release the profiling lock after the command buffer is no longer in the
// pending state.
vkReleaseProfilingLockKHR(device);

result = vkResetCommandBuffer(commandBuffer, 0);

assert(VK_SUCCESS == result);

// Create an array to hold the results of all counters
VkPerformanceCounterResultKHR* recordedCounters = malloc(
  sizeof(VkPerformanceCounterResultKHR) * enabledCounterCount);

result = vkGetQueryPoolResults(
  device,
  queryPool,
  0,
  1,
  sizeof(VkPerformanceCounterResultKHR) * enabledCounterCount,
  recordedCounters,
  sizeof(VkPerformanceCounterResultKHR),
  NULL);

// recordedCounters is filled with our counters, we'll look at one for posterity
switch (counters[0].storage) {
  case VK_PERFORMANCE_COUNTER_STORAGE_INT32:
    // use recordCounters[0].int32 to get at the counter result!
    break;
  case VK_PERFORMANCE_COUNTER_STORAGE_INT64:
    // use recordCounters[0].int64 to get at the counter result!
    break;
  case VK_PERFORMANCE_COUNTER_STORAGE_UINT32:
    // use recordCounters[0].uint32 to get at the counter result!
    break;
  case VK_PERFORMANCE_COUNTER_STORAGE_UINT64:
    // use recordCounters[0].uint64 to get at the counter result!
    break;
  case VK_PERFORMANCE_COUNTER_STORAGE_FLOAT32:
    // use recordCounters[0].float32 to get at the counter result!
    break;
  case VK_PERFORMANCE_COUNTER_STORAGE_FLOAT64:
    // use recordCounters[0].float64 to get at the counter result!
    break;
}

Version History

  • Revision 1, 2019-10-08

See Also

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.

Copyright (c) 2014-2020 Khronos Group. This work is licensed under a Creative Commons Attribution 4.0 International License.