Function latency_kernel 

pub fn latency_kernel(
    l: Latency,
    ticks: b64,
    begin: bool,
    end: bool,
    abandon: bool,
) -> Latency

Opens or closes a latency measurement.

• begin: a request handshake happened while in_flight (before it) was zero.
• end: an answer’s last handshake happened while in_flight (before it) was one.
• abandon: a second request arrived while one was measured.