After finally migrating some RB3011 boxes from v6 to v7 (7.6), CPU usage got crazy high with absolutely no change on configuration whatsoever.
Graphs from Zabbix shows my previous CPU usage and usage now (on the right), after the update that happened last night, so I have a single day running v7.
I do have hotspot enabled, so enabling fasttrack is complicated as it completly screws up hotspot accounting (it's documented that will happen with fasttrack), so I prefer to keep it disabled. Previously, with v6, that wasn't a problem at all. In fact, today (monday) is the day we have the least users on the network, and yet CPU usage just got MUCH higher with v7. WAN traffic had no significant change to explain that.
While I know the RB3011 is not a SUPER powerful box, graphs are clear to show it was absolutely more than enough to serve this specific network with RouterOS v6. With v7, CPU usage is crazy high with no config change or network behavior (higher traffic, user count, etc) to explain that.
Some graphs from Zabbix ...
.
Hotspot Authenticated Users - actually today is the day we have the least users on this network
.
WAN traffic - no significant change to explain the CPU usage getting so high