Constant DEFAULT_SCRUB_BUDGET 

pub const DEFAULT_SCRUB_BUDGET: usize = _; // 1_048_576usize

Default number of bytes a ScrubCursor hashes per next() slice The scrub slice-size bench sweeps 64 KiB…64 MiB and finds throughput essentially flat (the scan is xxh3/memory-bandwidth-bound, not per-slice-overhead-bound), so the budget is a pacing quantum, not a throughput knob: 1 MiB is ~sub-millisecond per slice — fine-grained enough to pause, cancel or report progress smoothly, with negligible overhead.