Merge pull request #2086 from billhollings/VK_EXT_headless_surface

Add support for extension VK_EXT_headless_surface.

Common/MVKOSExtensions.h

@@ -24,6 +24,9 @@
 #include <limits>
 
 
+#pragma mark -
+#pragma mark Operating System versions
+
 typedef float MVKOSVersion;
 
 /*** Constant indicating unsupported functionality in an OS. */
@@ -66,20 +69,31 @@ static inline bool mvkOSVersionIsAtLeast(MVKOSVersion macOSMinVer,
 #endif
 }
 
+
+#pragma mark -
+#pragma mark Timestamps
+
 /**
- * Returns a monotonic timestamp value for use in Vulkan and performance timestamping.
+ * Returns a monotonic tick value for use in Vulkan and performance timestamping.
  *
- * The returned value corresponds to the number of CPU "ticks" since the app was initialized.
- *
- * Calling this value twice, subtracting the first value from the second, and then multiplying
- * the result by the value returned by mvkGetTimestampPeriod() will provide an indication of the
- * number of nanoseconds between the two calls. The convenience function mvkGetElapsedMilliseconds()
- * can be used to perform this calculation.
+ * The returned value corresponds to the number of CPU ticks since an arbitrary 
+ * point in the past, and does not increment while the system is asleep.
  */
 uint64_t mvkGetTimestamp();
 
-/** Returns the number of nanoseconds between each increment of the value returned by mvkGetTimestamp(). */
-double mvkGetTimestampPeriod();
+/** 
+ * Returns the number of runtime nanoseconds since an arbitrary point in the past,
+ * excluding any time spent while the system is asleep.
+ *
+ * This value corresponds to the timestamps returned by Metal presentation timings.
+ */
+uint64_t mvkGetRuntimeNanoseconds();
+
+/**
+ * Returns the number of nanoseconds since an arbitrary point in the past,
+ * including any time spent while the system is asleep.
+ */
+uint64_t mvkGetContinuousNanoseconds();
 
 /**
  * Returns the number of nanoseconds elapsed between startTimestamp and endTimestamp,
@@ -97,12 +111,6 @@ uint64_t mvkGetElapsedNanoseconds(uint64_t startTimestamp = 0, uint64_t endTimes
  */
 double mvkGetElapsedMilliseconds(uint64_t startTimestamp = 0, uint64_t endTimestamp = 0);
 
-/** Returns the current absolute time in nanoseconds. */
-uint64_t mvkGetAbsoluteTime();
-
-/** Ensures the block is executed on the main thread. */
-void mvkDispatchToMainAndWait(dispatch_block_t block);
-
 
 #pragma mark -
 #pragma mark Process environment
@@ -141,8 +149,12 @@ uint64_t mvkGetUsedMemorySize();
 /** Returns the size of a page of host memory on this platform. */
 uint64_t mvkGetHostMemoryPageSize();
 
+
 #pragma mark -
 #pragma mark Threading
 
 /** Returns the amount of avaliable CPU cores. */
 uint32_t mvkGetAvaliableCPUCores();
+
+/** Ensures the block is executed on the main thread. */
+void mvkDispatchToMainAndWait(dispatch_block_t block);

Common/MVKOSExtensions.mm

@@ -29,6 +29,10 @@
 
 using namespace std;
 
+
+#pragma mark -
+#pragma mark Operating System versions
+
 MVKOSVersion mvkOSVersion() {
 	static MVKOSVersion _mvkOSVersion = 0;
 	if ( !_mvkOSVersion ) {
@@ -38,43 +42,35 @@ MVKOSVersion mvkOSVersion() {
 	return _mvkOSVersion;
 }
 
-static uint64_t _mvkTimestampBase;
-static double _mvkTimestampPeriod;
+
+#pragma mark -
+#pragma mark Timestamps
+
 static mach_timebase_info_data_t _mvkMachTimebase;
 
-uint64_t mvkGetTimestamp() { return mach_absolute_time() - _mvkTimestampBase; }
+uint64_t mvkGetTimestamp() { return mach_absolute_time(); }
+
+uint64_t mvkGetRuntimeNanoseconds() { return mach_absolute_time() * _mvkMachTimebase.numer / _mvkMachTimebase.denom; }
 
-double mvkGetTimestampPeriod() { return _mvkTimestampPeriod; }
+uint64_t mvkGetContinuousNanoseconds() { return mach_continuous_time() * _mvkMachTimebase.numer / _mvkMachTimebase.denom; }
 
 uint64_t mvkGetElapsedNanoseconds(uint64_t startTimestamp, uint64_t endTimestamp) {
 	if (endTimestamp == 0) { endTimestamp = mvkGetTimestamp(); }
-	return (endTimestamp - startTimestamp) * _mvkTimestampPeriod;
+	return (endTimestamp - startTimestamp) * _mvkMachTimebase.numer / _mvkMachTimebase.denom;
 }
 
 double mvkGetElapsedMilliseconds(uint64_t startTimestamp, uint64_t endTimestamp) {
 	return mvkGetElapsedNanoseconds(startTimestamp, endTimestamp) / 1e6;
 }
 
-uint64_t mvkGetAbsoluteTime() { return mach_continuous_time() * _mvkMachTimebase.numer / _mvkMachTimebase.denom; }
-
-// Initialize timestamping capabilities on app startup.
-//Called automatically when the framework is loaded and initialized.
+// Initialize timestamp capabilities on app startup.
+// Called automatically when the framework is loaded and initialized.
 static bool _mvkTimestampsInitialized = false;
 __attribute__((constructor)) static void MVKInitTimestamps() {
 	if (_mvkTimestampsInitialized ) { return; }
 	_mvkTimestampsInitialized = true;
 
-	_mvkTimestampBase = mach_absolute_time();
 	mach_timebase_info(&_mvkMachTimebase);
-	_mvkTimestampPeriod = (double)_mvkMachTimebase.numer / (double)_mvkMachTimebase.denom;
-}
-
-void mvkDispatchToMainAndWait(dispatch_block_t block) {
-	if (NSThread.isMainThread) {
-		block();
-	} else {
-		dispatch_sync(dispatch_get_main_queue(), block);
-	}
 }
 
 
@@ -145,10 +141,19 @@ uint64_t mvkGetUsedMemorySize() {
 
 uint64_t mvkGetHostMemoryPageSize() { return sysconf(_SC_PAGESIZE); }
 
+
 #pragma mark -
 #pragma mark Threading
 
 /** Returns the amount of avaliable CPU cores. */
 uint32_t mvkGetAvaliableCPUCores() {
     return (uint32_t)[[NSProcessInfo processInfo] activeProcessorCount];
 }
+
+void mvkDispatchToMainAndWait(dispatch_block_t block) {
+	if (NSThread.isMainThread) {
+		block();
+	} else {
+		dispatch_sync(dispatch_get_main_queue(), block);
+	}
+}

Docs/MoltenVK_Runtime_UserGuide.md

@@ -380,6 +380,9 @@ In addition to core *Vulkan* functionality, **MoltenVK**  also supports the foll
 - `VK_EXT_external_memory_host`
 - `VK_EXT_fragment_shader_interlock`
   - *Requires Metal 2.0 and Raster Order Groups.*
+- `VK_EXT_hdr_metadata`
+  - *macOS only.*
+- `VK_EXT_headless_surface`
 - `VK_EXT_host_query_reset`
 - `VK_EXT_image_robustness`
 - `VK_EXT_inline_uniform_block`

Docs/Whats_New.md

@@ -20,11 +20,13 @@ Released TBD
 
 - Add support for extensions:
 	- `VK_EXT_extended_dynamic_state3` *(Metal does not support `VK_POLYGON_MODE_POINT`)*
+	- `VK_EXT_headless_surface`
 - Fix regression that broke `VK_POLYGON_MODE_LINE`.
 - Fix regression in marking rendering state dirty after `vkCmdClearAttachments()`.
 - Reduce disk space consumed after running `fetchDependencies` script by removing intermediate file caches.
 - Fix rare deadlock during launch via `dlopen()`.
 - Fix initial value of `VkPhysicalDeviceLimits::timestampPeriod` on non-Apple Silicon GPUs.
+- Fix swapchain and surface bugs when windowing system is accessed from off the main thread.
 - Update to latest SPIRV-Cross:
   - MSL: Fix regression error in argument buffer runtime arrays.
   - MSL: Work around broken cube texture gradients on Apple Silicon.

MoltenVK/MoltenVK.xcodeproj/project.pbxproj

@@ -117,7 +117,7 @@
 		2FEA0AAF24902F9F00EEF3AD /* MVKLayers.mm in Sources */ = {isa = PBXBuildFile; fileRef = A94FB7A11C7DFB4800632CA3 /* MVKLayers.mm */; };
 		2FEA0AB024902F9F00EEF3AD /* MVKFramebuffer.mm in Sources */ = {isa = PBXBuildFile; fileRef = A94FB7881C7DFB4800632CA3 /* MVKFramebuffer.mm */; };
 		2FEA0AB124902F9F00EEF3AD /* MVKMTLBufferAllocation.mm in Sources */ = {isa = PBXBuildFile; fileRef = A9C96DCF1DDC20C20053187F /* MVKMTLBufferAllocation.mm */; };
-		2FEA0AB224902F9F00EEF3AD /* CAMetalLayer+MoltenVK.m in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.m */; };
+		2FEA0AB224902F9F00EEF3AD /* CAMetalLayer+MoltenVK.mm in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.mm */; };
 		2FEA0AB324902F9F00EEF3AD /* MVKCmdDispatch.mm in Sources */ = {isa = PBXBuildFile; fileRef = A9096E5D1F81E16300DFBEA6 /* MVKCmdDispatch.mm */; };
 		2FEA0AB424902F9F00EEF3AD /* MVKCmdDebug.mm in Sources */ = {isa = PBXBuildFile; fileRef = A99C90ED229455B300A061DA /* MVKCmdDebug.mm */; };
 		45003E73214AD4E500E989CB /* MVKExtensions.def in Headers */ = {isa = PBXBuildFile; fileRef = 45003E6F214AD4C900E989CB /* MVKExtensions.def */; };
@@ -360,8 +360,8 @@
 		A9E53DE62100B197002781DD /* NSString+MoltenVK.mm in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DD42100B197002781DD /* NSString+MoltenVK.mm */; };
 		A9E53DE72100B197002781DD /* MTLTextureDescriptor+MoltenVK.m in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DD52100B197002781DD /* MTLTextureDescriptor+MoltenVK.m */; };
 		A9E53DE82100B197002781DD /* MTLTextureDescriptor+MoltenVK.m in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DD52100B197002781DD /* MTLTextureDescriptor+MoltenVK.m */; };
-		A9E53DE92100B197002781DD /* CAMetalLayer+MoltenVK.m in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.m */; };
-		A9E53DEA2100B197002781DD /* CAMetalLayer+MoltenVK.m in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.m */; };
+		A9E53DE92100B197002781DD /* CAMetalLayer+MoltenVK.mm in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.mm */; };
+		A9E53DEA2100B197002781DD /* CAMetalLayer+MoltenVK.mm in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.mm */; };
 		A9E53DF32100B302002781DD /* MTLRenderPassDescriptor+MoltenVK.h in Headers */ = {isa = PBXBuildFile; fileRef = A9E53DEE2100B302002781DD /* MTLRenderPassDescriptor+MoltenVK.h */; };
 		A9E53DF42100B302002781DD /* MTLRenderPassDescriptor+MoltenVK.h in Headers */ = {isa = PBXBuildFile; fileRef = A9E53DEE2100B302002781DD /* MTLRenderPassDescriptor+MoltenVK.h */; };
 		A9E53DF52100B302002781DD /* MTLRenderPassDescriptor+MoltenVK.m in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DF22100B302002781DD /* MTLRenderPassDescriptor+MoltenVK.m */; };
@@ -495,7 +495,7 @@
 		DCFD7F572A45BC6E007BBBF7 /* MVKFramebuffer.mm in Sources */ = {isa = PBXBuildFile; fileRef = A94FB7881C7DFB4800632CA3 /* MVKFramebuffer.mm */; };
 		DCFD7F582A45BC6E007BBBF7 /* MTLRenderPassStencilAttachmentDescriptor+MoltenVK.m in Sources */ = {isa = PBXBuildFile; fileRef = 453638302508A4C6000EFFD3 /* MTLRenderPassStencilAttachmentDescriptor+MoltenVK.m */; };
 		DCFD7F592A45BC6E007BBBF7 /* MVKMTLBufferAllocation.mm in Sources */ = {isa = PBXBuildFile; fileRef = A9C96DCF1DDC20C20053187F /* MVKMTLBufferAllocation.mm */; };
-		DCFD7F5A2A45BC6E007BBBF7 /* CAMetalLayer+MoltenVK.m in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.m */; };
+		DCFD7F5A2A45BC6E007BBBF7 /* CAMetalLayer+MoltenVK.mm in Sources */ = {isa = PBXBuildFile; fileRef = A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.mm */; };
 		DCFD7F5B2A45BC6E007BBBF7 /* MVKCmdDispatch.mm in Sources */ = {isa = PBXBuildFile; fileRef = A9096E5D1F81E16300DFBEA6 /* MVKCmdDispatch.mm */; };
 		DCFD7F5C2A45BC6E007BBBF7 /* MVKCmdDebug.mm in Sources */ = {isa = PBXBuildFile; fileRef = A99C90ED229455B300A061DA /* MVKCmdDebug.mm */; };
 /* End PBXBuildFile section */
@@ -691,7 +691,7 @@
 		A9E53DD32100B197002781DD /* MTLSamplerDescriptor+MoltenVK.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "MTLSamplerDescriptor+MoltenVK.h"; sourceTree = "<group>"; };
 		A9E53DD42100B197002781DD /* NSString+MoltenVK.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = "NSString+MoltenVK.mm"; sourceTree = "<group>"; };
 		A9E53DD52100B197002781DD /* MTLTextureDescriptor+MoltenVK.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "MTLTextureDescriptor+MoltenVK.m"; sourceTree = "<group>"; };
-		A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "CAMetalLayer+MoltenVK.m"; sourceTree = "<group>"; };
+		A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = "CAMetalLayer+MoltenVK.mm"; sourceTree = "<group>"; };
 		A9E53DEE2100B302002781DD /* MTLRenderPassDescriptor+MoltenVK.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "MTLRenderPassDescriptor+MoltenVK.h"; sourceTree = "<group>"; };
 		A9E53DF22100B302002781DD /* MTLRenderPassDescriptor+MoltenVK.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "MTLRenderPassDescriptor+MoltenVK.m"; sourceTree = "<group>"; };
 		A9E53DFA21064F84002781DD /* MTLRenderPipelineDescriptor+MoltenVK.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "MTLRenderPipelineDescriptor+MoltenVK.m"; sourceTree = "<group>"; };
@@ -889,7 +889,7 @@
 			isa = PBXGroup;
 			children = (
 				A9E53DD12100B197002781DD /* CAMetalLayer+MoltenVK.h */,
-				A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.m */,
+				A9E53DD62100B197002781DD /* CAMetalLayer+MoltenVK.mm */,
 				453638312508A4C7000EFFD3 /* MTLRenderPassDepthAttachmentDescriptor+MoltenVK.h */,
 				4536382F2508A4C6000EFFD3 /* MTLRenderPassDepthAttachmentDescriptor+MoltenVK.m */,
 				A9E53DEE2100B302002781DD /* MTLRenderPassDescriptor+MoltenVK.h */,
@@ -1703,7 +1703,7 @@
 				2FEA0AAF24902F9F00EEF3AD /* MVKLayers.mm in Sources */,
 				2FEA0AB024902F9F00EEF3AD /* MVKFramebuffer.mm in Sources */,
 				2FEA0AB124902F9F00EEF3AD /* MVKMTLBufferAllocation.mm in Sources */,
-				2FEA0AB224902F9F00EEF3AD /* CAMetalLayer+MoltenVK.m in Sources */,
+				2FEA0AB224902F9F00EEF3AD /* CAMetalLayer+MoltenVK.mm in Sources */,
 				2FEA0AB324902F9F00EEF3AD /* MVKCmdDispatch.mm in Sources */,
 				2FEA0AB424902F9F00EEF3AD /* MVKCmdDebug.mm in Sources */,
 			);
@@ -1763,7 +1763,7 @@
 				A94FB7EE1C7DFB4800632CA3 /* MVKFramebuffer.mm in Sources */,
 				453638382508A4C7000EFFD3 /* MTLRenderPassStencilAttachmentDescriptor+MoltenVK.m in Sources */,
 				A9C96DD21DDC20C20053187F /* MVKMTLBufferAllocation.mm in Sources */,
-				A9E53DE92100B197002781DD /* CAMetalLayer+MoltenVK.m in Sources */,
+				A9E53DE92100B197002781DD /* CAMetalLayer+MoltenVK.mm in Sources */,
 				A9096E5E1F81E16300DFBEA6 /* MVKCmdDispatch.mm in Sources */,
 				A99C90F0229455B300A061DA /* MVKCmdDebug.mm in Sources */,
 			);
@@ -1823,7 +1823,7 @@
 				A94FB7EF1C7DFB4800632CA3 /* MVKFramebuffer.mm in Sources */,
 				4536383A2508A4C7000EFFD3 /* MTLRenderPassStencilAttachmentDescriptor+MoltenVK.m in Sources */,
 				A9C96DD31DDC20C20053187F /* MVKMTLBufferAllocation.mm in Sources */,
-				A9E53DEA2100B197002781DD /* CAMetalLayer+MoltenVK.m in Sources */,
+				A9E53DEA2100B197002781DD /* CAMetalLayer+MoltenVK.mm in Sources */,
 				A9096E5F1F81E16300DFBEA6 /* MVKCmdDispatch.mm in Sources */,
 				A99C90F1229455B300A061DA /* MVKCmdDebug.mm in Sources */,
 			);
@@ -1883,7 +1883,7 @@
 				DCFD7F572A45BC6E007BBBF7 /* MVKFramebuffer.mm in Sources */,
 				DCFD7F582A45BC6E007BBBF7 /* MTLRenderPassStencilAttachmentDescriptor+MoltenVK.m in Sources */,
 				DCFD7F592A45BC6E007BBBF7 /* MVKMTLBufferAllocation.mm in Sources */,
-				DCFD7F5A2A45BC6E007BBBF7 /* CAMetalLayer+MoltenVK.m in Sources */,
+				DCFD7F5A2A45BC6E007BBBF7 /* CAMetalLayer+MoltenVK.mm in Sources */,
 				DCFD7F5B2A45BC6E007BBBF7 /* MVKCmdDispatch.mm in Sources */,
 				DCFD7F5C2A45BC6E007BBBF7 /* MVKCmdDebug.mm in Sources */,
 			);

MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm

@@ -1202,8 +1202,8 @@
     isHeadless = getMTLDevice().isHeadless;
 #endif
 
-	// If this device is headless or the surface does not have a CAMetalLayer, it is not supported.
-    *pSupported = !(isHeadless || (surface->getCAMetalLayer() == nil));
+	// If this device is headless, the surface must be headless.
+	*pSupported = isHeadless ? surface->isHeadless() : wasConfigurationSuccessful();
 	return *pSupported ? VK_SUCCESS : surface->getConfigurationResult();
 }
 
@@ -1262,13 +1262,12 @@
 
 	// The CAlayer underlying the surface must be a CAMetalLayer.
 	MVKSurface* surface = (MVKSurface*)pSurfaceInfo->surface;
-	CAMetalLayer* mtlLayer = surface->getCAMetalLayer();
-	if ( !mtlLayer ) { return surface->getConfigurationResult(); }
+	if ( !surface->wasConfigurationSuccessful() ) { return surface->getConfigurationResult(); }
 
 	VkSurfaceCapabilitiesKHR& surfCaps = pSurfaceCapabilities->surfaceCapabilities;
 	surfCaps.minImageCount = _metalFeatures.minSwapchainImageCount;
 	surfCaps.maxImageCount = _metalFeatures.maxSwapchainImageCount;
-	surfCaps.currentExtent = mvkGetNaturalExtent(mtlLayer);
+	surfCaps.currentExtent = surface->getNaturalExtent();
 	surfCaps.minImageExtent = { 1, 1 };
 	surfCaps.maxImageExtent = { _properties.limits.maxImageDimension2D, _properties.limits.maxImageDimension2D };
 	surfCaps.maxImageArrayLayers = 1;
@@ -1347,9 +1346,7 @@
 											  uint32_t* pCount,
 											  VkSurfaceFormatKHR* pSurfaceFormats) {
 
-	// The layer underlying the surface view must be a CAMetalLayer.
-	CAMetalLayer* mtlLayer = surface->getCAMetalLayer();
-	if ( !mtlLayer ) { return surface->getConfigurationResult(); }
+	if ( !surface->wasConfigurationSuccessful() ) { return surface->getConfigurationResult(); }
 
 #define addSurfFmt(MTL_FMT) \
 	do { \
@@ -1472,9 +1469,7 @@
 												   uint32_t* pCount,
 												   VkPresentModeKHR* pPresentModes) {
 
-	// The layer underlying the surface view must be a CAMetalLayer.
-	CAMetalLayer* mtlLayer = surface->getCAMetalLayer();
-	if ( !mtlLayer ) { return surface->getConfigurationResult(); }
+	if ( !surface->wasConfigurationSuccessful() ) { return surface->getConfigurationResult(); }
 
 #define ADD_VK_PRESENT_MODE(VK_PM)																	\
 	do {																							\
@@ -1502,9 +1497,7 @@
 												 uint32_t* pRectCount,
 												 VkRect2D* pRects) {
 
-	// The layer underlying the surface view must be a CAMetalLayer.
-	CAMetalLayer* mtlLayer = surface->getCAMetalLayer();
-	if ( !mtlLayer ) { return surface->getConfigurationResult(); }
+	if ( !surface->wasConfigurationSuccessful() ) { return surface->getConfigurationResult(); }
 
 	if ( !pRects ) {
 		*pRectCount = 1;
@@ -1516,7 +1509,7 @@
 	*pRectCount = 1;
 
 	pRects[0].offset = { 0, 0 };
-	pRects[0].extent = mvkGetNaturalExtent(mtlLayer);
+	pRects[0].extent = surface->getNaturalExtent();
 
 	return VK_SUCCESS;
 }
@@ -3672,14 +3665,14 @@ static uint32_t mvkGetEntryProperty(io_registry_entry_t entry, CFStringRef prope
 	MTLTimestamp cpuStamp, gpuStamp;
 	uint64_t cpuStart, cpuEnd;
 
-	cpuStart = mvkGetAbsoluteTime();
+	cpuStart = mvkGetContinuousNanoseconds();
 	[getMTLDevice() sampleTimestamps: &cpuStamp gpuTimestamp: &gpuStamp];
 	// Sample again to calculate the maximum deviation. Note that the
 	// -[MTLDevice sampleTimestamps:gpuTimestamp:] method guarantees that CPU
 	// timestamps are in nanoseconds. We don't want to call the method again,
 	// because that could result in an expensive syscall to query the GPU time-
 	// stamp.
-	cpuEnd = mvkGetAbsoluteTime();
+	cpuEnd = mvkGetContinuousNanoseconds();
 	for (uint32_t tsIdx = 0; tsIdx < timestampCount; ++tsIdx) {
 		switch (pTimestampInfos[tsIdx].timeDomain) {
 			case VK_TIME_DOMAIN_DEVICE_EXT: