Function bench_trace_overhead 

pub(crate) fn bench_trace_overhead(
    program: &Arc<Program>,
    sources: &Arc<SourceMap>,
    row: &Row<'_>,
    iterations: u32,
) -> TraceOverheadReport

Times one row untraced and then traced, back to back.

This one stays blocked whatever --sample-order says, and deliberately: what it reports is the ratio of two series of the same work, so the two have to be taken as close together as they can be. Spreading them apart would put the machine’s drift between the numerator and the denominator, which is the mistake the flag exists to avoid making everywhere else.