message: nydusctl: print rafs read op latency distribution
  It helps to analyze rafs performance
diff: @@ -284,6 +284,31 @@ impl CommandFsStats {
  if raw {
  println!("{}", metrics);
  } else {
  + let periods = vec![
  + "<1ms", "~20ms", "~50ms", "~100ms", "~500ms", "~1s", "~2s", "2s~",
  + ];
  + let latency_dist = m["read_latency_dist"].as_array().unwrap();
  + println!(
  + r#"
  +{:<16}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}{:<8}"#,
  + "Read Latency:",
  + periods[0],
  + periods[1],
  + periods[2],
  + periods[3],
  + periods[4],
  + periods[5],
  + periods[6],
  + periods[7],
  + );
  +
  + print!("{:<16}", "Reads Count:");
  + for d in latency_dist {
  + print!("{:<8}", d.as_u64().unwrap());
  + }
  +
  + println!();
  +
  print!(
  r#"
  FOP Counters:
  