We trace every server request with it, across all stages of the request—approx. 10-12 events/timestamps per request—across multiple processes (think Zipkin). The per-request event streams are independent "trails" per process, and then we merge them together later and compute aggregated metrics using hdr_histogram.

Individual events are typically hundreds to thousands of nanoseconds long, with about 20 nanoseconds of overhead to grab a timestamp using the rdtscp instruction.

Hope that helps!