fn initially_uncached(c: &mut Criterion) {
    let mut group = c.benchmark_group("initially_uncached");
    group.plot_config(PlotConfiguration::default().summary_scale(AxisScale::Logarithmic));

    for num_bytes in [1 << 12, 1 << 20, 1 << 25] {
        group.throughput(Throughput::Bytes(num_bytes));
        add_benches(&mut group, num_bytes, true);
    }
}
Use direct I/O to create the file to be copied so it's not cached initially
cpz/benches/copy_methods.rs