Did you find some sort of answer to this?

I could not find how to measure the performance for MetricKit signpost anywhere. A WWDC19 video suggested to look up documentation on it, but it doesn't exist. Thankfully, in Instruments, I found that the subcategory for the OSLog signpost created by MXMetricManager.makeLogHandle(category:) is com.apple.metrickit.log. Therefore, in order to measure the performance of your block, you do something like the following: measure(metrics: [XCTOSSignpostMetric(subsystem: "com.apple.metrickit.log",                                   category: "My category",                                       name: "My name")]) { ... }