Hi AndreiHurmuz
I worked with F5 support on the issue. The comment from them was;
Yes, a some CPU usage increase after upgrading to a later major software release is expected due to additional features in the new software version. However, this should not affect production traffic. If it does, we have to review the configuration and adjust things until we get this under control.
So some CPU rise is expected. We needed to look at cleaning up our config. Some standouts aside from the LDAP monitors mentioned by answ161 is halfopen monitors. We had a lot of them and they put load on CPU. Also if you have a lot of pool members that are down, the system is constantly waiting for responses from those members.
Cheers