1. pub fn readahead(fd: libc::c_int, mut offset: u64, end: u64) {
    2.     let mut count;
    3.     offset = round_down_4k(offset);
    4.     loop {
    5.         if offset >= end {
    6.             break;
    7.         }
    8.         // Kernel default 128KB readahead size
    9.         count = std::cmp::min(128 << 10, end - offset);
    10.         unsafe { libc::readahead(fd, offset as i64, count as usize) };
    11.         offset += count;
    12.     }
    13. }