Move CPU/GPU timestamp correlation to vkGetPhysicalDeviceProperties()

KhronosGroup / MoltenVK

MoltenVK is a Vulkan Portability implementation. It layers a subset of the high-performance, industry-standard Vulkan graphics and compute API over Apple's Metal graphics framework, enabling Vulkan applications to run on macOS, iOS and tvOS.

Apache License 2.0

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It turns out that MTLDevice sampleTimestamps:gpuTimestamp: executes synchronously with other queue activities, and can block GPU execution if it is called frequently.

Move timestamp correlation to the execution of vkGetPhysicalDeviceProperties() so it is called only on demand by the app.

Furthermore, MTLDevice sampleTimestamps:gpuTimestamp: should only be invoked if all of these conditions are met (otherwise the VkPhysicalDeviceLimits::timestampPeriod should be set to 1.0):

CPU is not Apple Silicon (!supportsMTLGPUFamily(Apple1)).
MVKPhysicalDevice::_timestampMTLCounterSet exists.
MVKPhysicalDeviceMetalFeatures::counterSamplingPoints is empty.

KhronosGroup / MoltenVK

Move CPU/GPU timestamp correlation to vkGetPhysicalDeviceProperties() #1983