Re: [tipc-discussion] Gacks on, callbacks suppressed messages

[Tung Q. N. <tun...@de...>]

>   When pushing TIPC a bit hard on some of our servers, I've recently had three of them issue clusters of "Gacks on" messages, with two
>of them also issuing "callbacks suppressed" messages. These had kernels from 5.10 to 6.2, so it doesn't seem like an issue with a
>particular kernel. Here is a sample dmesg fragment:
>
>[Wed May 17 17:36:15 2023] __tipc_build_gap_ack_blks: 5 callbacks suppressed
>[Wed May 17 17:36:15 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4d75f5:eno1: 64, ql: 291!
>[Wed May 17 17:36:15 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4d75f5:eno1: 64, ql: 307!
>[Wed May 17 17:36:15 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4d75f5:eno1: 64, ql: 227!
>[Wed May 17 17:36:15 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4d75f5:eno1: 64, ql: 243!
>[Wed May 17 17:36:15 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4d75f5:eno1: 64, ql: 259!
>[Wed May 17 17:36:16 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4d75f5:eno1: 64, ql: 355!
>[Wed May 17 17:36:16 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4d75f5:eno1: 64, ql: 259!
>[Wed May 17 17:36:18 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4db43e:eno1: 64, ql: 323!
>[Wed May 17 17:36:18 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4d75f5:eno1: 64, ql: 515!
>[Wed May 17 17:36:18 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4d75f5:eno1: 64, ql: 531!
>[Wed May 17 17:36:21 2023] __tipc_build_gap_ack_blks: 121 callbacks suppressed
>[Wed May 17 17:36:21 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4db43e:eno1: 64, ql: 147!
>[Wed May 17 17:36:21 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4db43e:eno1: 64, ql: 163!
>[Wed May 17 17:36:21 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4db43e:eno1: 64, ql: 179!
>[Wed May 17 17:36:21 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4d75f5:eno1: 64, ql: 355!
>[Wed May 17 17:36:21 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4db43e:eno1: 64, ql: 195!
>[Wed May 17 17:36:21 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4db43e:eno1: 64, ql: 195!
>[Wed May 17 17:36:21 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4db43e:eno1: 64, ql: 211!
>[Wed May 17 17:36:21 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4d75f5:eno1: 64, ql: 403!
>[Wed May 17 17:36:21 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4db43e:eno1: 64, ql: 227!
>[Wed May 17 17:36:21 2023] tipc: Gacks on 1866da4d3dd9:eth0-1866da4db43e:eno1: 64, ql: 243!
>
>Does this point to a need for tuning, or some bug?
No need for tuning, It is not a bug.
It indicates that your servers were under high load (a lot of message disorders or message losses).
The servers have used the maximum number of Selective ACK blocks (64) to deal with this situation and
everything was handled well.