I can confirm the ksoftirqd/3 cpu load behavior. I have 3 of the same routers on the stable release, strangely enough, I don't see it on the other 2. Both are online much longer than the 3rd one.
root@caretaker3:~# uptime
13:09:25 up 1:38, load average: 1.61, 1.65, 1.67
root@caretaker2:~# uptime
15:55:55 up 14:58, load average: 0.00, 0.00, 0.00
root@caretaker1:~# uptime
13:09:52 up 14:58, load average: 0.06, 0.03, 0.00
All are running:
OpenWrt 21.02.1, r16325-88151b8303
caretaker1 -> main router (WDS master)
caretaker2 -> WDS client
caretaker3 -> recently installed, WIFI cards are disabled , just connected on caretaker2 with LAN cable
Only caretaker1 is connected using WAN interface here.
root@caretaker3:~# cat /proc/interrupts
CPU0 CPU1 CPU2 CPU3
8: 1583542 1583518 1583430 1583485 MIPS GIC Local 1 timer
9: 384848 0 0 0 MIPS GIC 63 IPI call
10: 0 21999 0 0 MIPS GIC 64 IPI call
11: 0 0 684494 0 MIPS GIC 65 IPI call
12: 0 0 0 17403 MIPS GIC 66 IPI call
13: 153206524 0 0 0 MIPS GIC 67 IPI resched
14: 0 160359768 0 0 MIPS GIC 68 IPI resched
15: 0 0 5045583 0 MIPS GIC 69 IPI resched
16: 0 0 0 32542 MIPS GIC 70 IPI resched
17: 0 0 0 0 MIPS GIC 19 1e000600.gpio-bank0, 1e000600.gpio-bank1, 1e000600.gpio-bank2
19: 12 0 0 0 MIPS GIC 33 ttyS0
20: 0 0 0 0 MIPS GIC 29 xhci-hcd:usb1
21: 18710 0 0 0 MIPS GIC 10 1e100000.ethernet
23: 23 0 0 0 MIPS GIC 11 mt7603e
24: 16 0 0 327156842 MIPS GIC 31 mt7615e
26: 0 0 0 0 1e000600.gpio 8 keys
27: 0 0 0 0 1e000600.gpio 10 keys
ERR: 5371
I re-checked and both radio's are disabled on this router.
The router that is doing the most the ERR counter is not rising:
root@caretaker1:~# cat /proc/interrupts
CPU0 CPU1 CPU2 CPU3
8: 13611287 13611013 13610515 13611387 MIPS GIC Local 1 timer
9: 982356 0 0 0 MIPS GIC 63 IPI call
10: 0 43540 0 0 MIPS GIC 64 IPI call
11: 0 0 854987 0 MIPS GIC 65 IPI call
12: 0 0 0 78003 MIPS GIC 66 IPI call
13: 1152587 0 0 0 MIPS GIC 67 IPI resched
14: 0 1176937 0 0 MIPS GIC 68 IPI resched
15: 0 0 933843 0 MIPS GIC 69 IPI resched
16: 0 0 0 579682 MIPS GIC 70 IPI resched
17: 0 0 0 0 MIPS GIC 19 1e000600.gpio-bank0, 1e000600.gpio-bank1, 1e000600.gpio-bank2
19: 12 0 0 0 MIPS GIC 33 ttyS0
20: 0 0 0 0 MIPS GIC 29 xhci-hcd:usb1
21: 180854 0 0 0 MIPS GIC 10 1e100000.ethernet
23: 22 0 0 0 MIPS GIC 11 mt7603e
24: 18 0 0 1731029 MIPS GIC 31 mt7615e
26: 0 0 0 0 1e000600.gpio 8 keys
27: 0 0 0 0 1e000600.gpio 10 keys
ERR: 72