Why the execution of the 'iotop' command reports 'CONFIG_TASK_DELAY_ACCT' is not enabled in the kernel?

# iotop -p <invalid-pid>

# ps aux | grep 100000
root      6333  0.0  0.0 103260   844 pts/0    S+   15:03   0:00 grep 100000

# iotop -p 100000
Total DISK READ: 0.00 B/s | Total DISK WRITE: 0.00 B/s
  TID  PRIO  USER     DISK READ  DISK WRITE  SWAPIN     IO>    COMMAND                                                                                                                        

CONFIG_TASK_DELAY_ACCT not enabled in kernel, cannot determine SWAPIN and IO %

# ps -p 2 
  PID TTY          TIME CMD
    2 ?        00:00:00 kthreadd

# iotop -p 2
Total DISK READ: 0.00 B/s | Total DISK WRITE: 0.00 B/s
  TID  PRIO  USER     DISK READ  DISK WRITE  SWAPIN     IO>    COMMAND                                                                                                                        
    2 be/4 root        0.00 B/s    0.00 B/s  ?unavailable?  [kthreadd]

CONFIG_TASK_DELAY_ACCT not enabled in kernel, cannot determine SWAPIN and IO %