Fixes to determination of VkPhysicalDeviceLimits::timestampPeriod.

- On Apple GPUs, set timestampPeriod to 1.0.
- On non-Apple GPUs, calculate timestampPeriod each time it is retrieved.
- On older devices that do not support GPU timestamps, use nanosecond
  CPU timestamps to be consistent with timestampPeriod of 1.0.
- Change MVKConfiguration::timestampPeriodLowPassAlpha and environment
  variable MVK_CONFIG_TIMESTAMP_PERIOD_LOWPASS_ALPHA to 1.0, to use
  only latest value by default.
- Add build-time verification that MVKConfigMembers.def
  includes all members of MVKConfiguration (unrelated).

Docs/MoltenVK_Runtime_UserGuide.md

@@ -617,9 +617,9 @@ vailable when you request it, resulting in frame delays and visual stuttering.
 <a name="timestamping"></a>
 ### Timestamping
 
-On non-Apple Silicon devices (older Mac devices), the GPU can switch power and performance 
+On non-Apple GPUs (older Mac devices), the GPU can switch power and performance states as 
-states as required by usage. This affects the GPU timestamps retrievable through the Vulkan 
+required by usage. This affects the GPU timestamps retrievable through the Vulkan API. 
-API. As a result, the value of `VkPhysicalDeviceLimits::timestampPeriod` can vary over time. 
+As a result, the value of `VkPhysicalDeviceLimits::timestampPeriod` can vary over time. 
 Consider calling `vkGetPhysicalDeviceProperties()`, when needed, and retrieve the current
 value of `VkPhysicalDeviceLimits::timestampPeriod`, to help you calibrate recent GPU 
 timestamps queried through the Vulkan API.

Docs/Whats_New.md

@@ -29,7 +29,9 @@ Released TBD
 - Fix MSL code used in `vkCmdBlitImage()` on depth-stencil formats. 
 - Improve behavior of swapchain image presentation stalls caused by Metal regression.
 - Add several additional performance trackers, available via logging, or the `mvk_private_api.h` API.
-- Add configurable lowpass filter for `VkPhysicalDeviceLimits::timestampPeriod`.
+- Add `MVKConfiguration::timestampPeriodLowPassAlpha` and environment variable 
+  `MVK_CONFIG_TIMESTAMP_PERIOD_LOWPASS_ALPHA`, to add a configurable lowpass filter 
+  for varying `VkPhysicalDeviceLimits::timestampPeriod` on non-Apple GPUs.
 - Deprecate `MVK_DEBUG` env var, and add `MVK_CONFIG_DEBUG` env var to replace it. 
 - Update `MVK_CONFIGURATION_API_VERSION` and `MVK_PRIVATE_API_VERSION` to `38`.
 

MoltenVK/MoltenVK/API/mvk_config.h

@@ -955,7 +955,7 @@ typedef struct {
 	 * The initial value or this parameter is set by the
 	 * MVK_CONFIG_TIMESTAMP_PERIOD_LOWPASS_ALPHA
 	 * runtime environment variable or MoltenVK compile-time build setting.
-	 * If neither is set, this parameter is set to 0.05 by default,
+	 * If neither is set, this parameter is set to 1.0 by default,
 	 * indicating that the timestampPeriod will vary relatively slowly,
 	 * with the expectation that the app is querying this value infrequently.
 	 */

MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm

@@ -1601,7 +1601,8 @@ void MVKPhysicalDevice::updateTimestampPeriod() {
 			
 			// Basic lowpass filter TPout = (1 - A)TPout + (A * TPin).
 			// The lower A is, the slower TPout will change over time.
-			float a = mvkConfig().timestampPeriodLowPassAlpha;
+			// First time through, just use the measured value directly.
+			float a = earlierCPUTs ? mvkConfig().timestampPeriodLowPassAlpha : 1.0;
 			_properties.limits.timestampPeriod = ((1.0 - a) * _properties.limits.timestampPeriod) + (a * tsPeriod);
 		}
 	}
@@ -2637,7 +2638,7 @@ void MVKPhysicalDevice::initLimits() {
     _properties.limits.optimalBufferCopyRowPitchAlignment = 1;
 
 	_properties.limits.timestampComputeAndGraphics = VK_TRUE;
-	_properties.limits.timestampPeriod = mvkGetTimestampPeriod();	// Will be 1.0 on Apple Silicon
+	_properties.limits.timestampPeriod = 1.0;	// On non-Apple GPU's, this can vary over time, and is calculated based on actual GPU activity.
 
     _properties.limits.pointSizeRange[0] = 1;
 	switch (_properties.vendorID) {

MoltenVK/MoltenVK/GPUObjects/MVKQueryPool.mm

@@ -381,7 +381,7 @@ void MVKTimestampQueryPool::endQuery(uint32_t query, MVKCommandEncoder* cmdEncod
 // If not using MTLCounterSampleBuffer, update timestamp values, then mark queries as available
 void MVKTimestampQueryPool::finishQueries(MVKArrayRef<const uint32_t> queries) {
 	if ( !_mtlCounterBuffer ) {
-		uint64_t ts = mvkGetTimestamp();
+		uint64_t ts = mvkGetElapsedNanoseconds();
 		for (uint32_t qry : queries) { _timestamps[qry] = ts; }
 	}
 	MVKQueryPool::finishQueries(queries);

MoltenVK/MoltenVK/Utility/MVKConfigMembers.def

@@ -23,16 +23,13 @@
 // To use this file, define the macros:
 //
 //   MVK_CONFIG_MEMBER(member, mbrType, name)
-//   MVK_CONFIG_MEMBER_STRING(member, strObj,  name)
+//   MVK_CONFIG_MEMBER_STRING(member, mbrType,  name)
 //
 // then #include this file inline with your code.
 //
 // The name prameter is the name of the configuration parameter, which is used as the name
 // of the environment variable, and build setting, that sets the config value, and is entered
 // here without the "MVK_CONFIG_" prefix.
-//
-// Since string members are set from char pointers, the text must be copied to a std::string
-// object, which is passed as a parameter to MVK_CONFIG_MEMBER_STRING.
 
 
 #ifndef MVK_CONFIG_MEMBER
@@ -69,7 +66,7 @@ MVK_CONFIG_MEMBER(forceLowPowerGPU,                       VkBool32,
 MVK_CONFIG_MEMBER(semaphoreUseMTLFence,                   VkBool32,                                 ALLOW_METAL_FENCES)  				// Deprecated legacy
 MVK_CONFIG_MEMBER(semaphoreSupportStyle,                  MVKVkSemaphoreSupportStyle,               VK_SEMAPHORE_SUPPORT_STYLE)
 MVK_CONFIG_MEMBER(autoGPUCaptureScope,                    MVKConfigAutoGPUCaptureScope,             AUTO_GPU_CAPTURE_SCOPE)
-MVK_CONFIG_MEMBER_STRING(autoGPUCaptureOutputFilepath,    evGPUCapFileStrObj,                       AUTO_GPU_CAPTURE_OUTPUT_FILE)
+MVK_CONFIG_MEMBER_STRING(autoGPUCaptureOutputFilepath,    char*,                                    AUTO_GPU_CAPTURE_OUTPUT_FILE)
 MVK_CONFIG_MEMBER(texture1DAs2D,                          VkBool32,                                 TEXTURE_1D_AS_2D)
 MVK_CONFIG_MEMBER(preallocateDescriptors,                 VkBool32,                                 PREALLOCATE_DESCRIPTORS)
 MVK_CONFIG_MEMBER(useCommandPooling,                      VkBool32,                                 USE_COMMAND_POOLING)

MoltenVK/MoltenVK/Utility/MVKEnvironment.cpp

@@ -20,8 +20,19 @@
 #include "MVKOSExtensions.h"
 #include "MVKFoundation.h"
 
+// Return the expected size of MVKConfiguration, based on contents of MVKConfigMembers.def.
+static constexpr uint32_t getExpectedMVKConfigurationSize() {
+#define MVK_CONFIG_MEMBER_STRING(member, mbrType, name)  MVK_CONFIG_MEMBER(member, mbrType, name)
+#define MVK_CONFIG_MEMBER(member, mbrType, name)         cfgSize += sizeof(mbrType);
+	uint32_t cfgSize = 0;
+#include "MVKConfigMembers.def"
+	return cfgSize;
+}
+
 static bool _mvkConfigInitialized = false;
 static void mvkInitConfigFromEnvVars() {
+	static_assert(getExpectedMVKConfigurationSize() == sizeof(MVKConfiguration), "MVKConfigMembers.def does not match the members of MVKConfiguration.");
+
 	_mvkConfigInitialized = true;
 
 	MVKConfiguration evCfg;
@@ -32,8 +43,8 @@ static void mvkInitConfigFromEnvVars() {
 #define MVK_CONFIG_MEMBER(member, mbrType, name) \
 	evCfg.member = (mbrType)mvkGetEnvVarNumber(STR(MVK_CONFIG_##name), MVK_CONFIG_##name);
 
-#define MVK_CONFIG_MEMBER_STRING(member, strObj, name) \
+#define MVK_CONFIG_MEMBER_STRING(member, mbrType, name) \
-	evCfg.member = mvkGetEnvVarString(STR(MVK_CONFIG_##name), strObj, MVK_CONFIG_##name);
+	evCfg.member = mvkGetEnvVarString(STR(MVK_CONFIG_##name), evGPUCapFileStrObj, MVK_CONFIG_##name);
 
 #include "MVKConfigMembers.def"
 

MoltenVK/MoltenVK/Utility/MVKEnvironment.h

@@ -323,5 +323,5 @@ void mvkSetConfig(const MVKConfiguration& mvkConfig);
  * This can be set to a float between 0.0 and 1.0.
  */
 #ifndef MVK_CONFIG_TIMESTAMP_PERIOD_LOWPASS_ALPHA
-#  	define MVK_CONFIG_TIMESTAMP_PERIOD_LOWPASS_ALPHA    0.05
+#  	define MVK_CONFIG_TIMESTAMP_PERIOD_LOWPASS_ALPHA    1.0
 #endif