Redis [BUG]When setback system time back, the fragmentation is going high

Describe the bug

Redis version:6.2.11 with jemalloc When I set system datetime back, i found the fragmentation of redis is keep going high, after the time reached the time i setting time back，the fragmentation of redis will go down immediately. (1)At the beginning: root@78:~# date Thu Sep 21 10:26:36 AM CST 2023

The fragmentation of redis : 65) "fragmentation" 66) "1.158626914024353" 67) "fragmentation.bytes" 68) (integer) 6567864

(2)Setting the date back: root@78:~# date -s "2023-09-21 10:00:00" Thu Sep 21 10:00:00 AM CST 2023

(3)Then the redis fragmentation keeps raising: 65) "fragmentation" 66) "1.9999270439147949" 67) "fragmentation.bytes" 68) (integer) 41421336 (4) When the time of the system reached Thu Sep 21 10:26:36 AM CST 2023, the fragmentation decreased: root@78:~# date Thu Sep 21 10:26:52 AM CST 2023 65) "fragmentation" 66) "1.159626914024353" 67) "fragmentation.bytes" 68) (integer) 6573864

To reproduce

Set system datetime back

Expected behavior

Additional information

Any additional information that is relevant to the problem.