[Galanwe]

It does reach nanosecond only in the sense that its sampling profiler can report nanosecond resolution. I've tried the event profiler for microsecond sensitive projets though, and it blows up the timings and latency even at low event frequency.

[vardump]

I think it’s mostly due to Tracy’s poor timing calibration code. TSC is good accuracy and latency wise.

[Galanwe]

The problem is not the timestamping, it's the queue used to push profiling events which is not fast enough

[vardump]

That queue is about as fast as it gets, <10 ns. Timestamp is taken before queueing.

Again, due to bad calibration code the measured timestamps have quite a bit jitter.

Edit: TSC might not be synchronized in multi-socket systems. (Multiple physical CPU sockets). That can generate a large error.