Kernel timers are inaccurate some times

문제

• We notice that there's an important and varying delay (eg. up to 4 minutes) between the expiration of the linux kernel net.ipv4.tcp_keepalive_time timer (3600 secs) and the actual sending of the tcp_keepalive (ack) packets, leading to unwanted aging of idle sessions by our firewall.
  • The higher the net.ipv4.tcp_keepalive_time value the longer the delay.
• Other kernel timers not just network timers like delayed work timers and possibly storage are also affected.