changing evs.keepalive_period to PT1S and letting evs.inactive_check_period go back to default result in better times although still way too long:
mysql> insert into t (id) values (NULL); Query OK, 1 row affected (4.71 sec)
mysql> insert into t (id) values (NULL); Query OK, 1 row affected (8.54 sec)
mysql> insert into t (id) values (NULL); Query OK, 1 row affected (4.50 sec)
For 3 node on each side + garb
changing evs.keepalive_ period to PT1S and letting evs.inactive_ check_period go back to default result in better times although still way too long:
mysql> insert into t (id) values (NULL);
Query OK, 1 row affected (4.71 sec)
mysql> insert into t (id) values (NULL);
Query OK, 1 row affected (8.54 sec)
mysql> insert into t (id) values (NULL);
Query OK, 1 row affected (4.50 sec)
For 3 node on each side + garb