I have a 450G router serving as PPPOE concentrator and Userman
I have noticed that most operations in userman often result in 100% CPU utilisation
Hence, whenever I am working on userman users will not be able to dial-in PPPOE
This is so frustrating as users always complains that they cannot login.
Right now I am confused.
I am thinking of removing the userman service from that router and placed in an x86 sytem but if I have to do that, I will rather try RadiusManager.

Couple Questions.
What version of ROS?
How many Users?
What Level?

I had a similar issue and I did eventually offload my User Manager to an x86 box just for User manger/hotspot radius. I also had this problem when I upgraded to 5.7. Instead of installing the individual packages I upgraded to the 5.7 (with all packages) in one npk file. That for some reason fixed the CPU issue. Also, I know there is a limit on how many sessions can be active at once on user manage unless you are using ROS level 6. Level 5 will not authenticate anymore than 50 and level 4 will only allow 20, etc. This could be part of your problem.

Our current system is working great.
x86 system with Usermanager/payment gateway running on it and several RBs running as hotspots. Customers can sign themselves up for time and create their own usernames/passwords and away they go.
I have heard people do similar things with freeradius, but I decided to go this direction. We also manage our PPPOE DSL customers with user manager.

What version of ROS? = 5.6
How many Users? over 2000 registered users in UsermaN with an average of 200 active pppoe clients
What Level? = 5
Active PPPOE limit for level 5 is 500 not 50.

Couple Questions.
What version of ROS?
How many Users?
What Level?

I had a similar issue and I did eventually offload my User Manager to an x86 box just for User manger/hotspot radius. I also had this problem when I upgraded to 5.7. Instead of installing the individual packages I upgraded to the 5.7 (with all packages) in one npk file. That for some reason fixed the CPU issue. Also, I know there is a limit on how many sessions can be active at once on user manage unless you are using ROS level 6. Level 5 will not authenticate anymore than 50 and level 4 will only allow 20, etc. This could be part of your problem.

Our current system is working great.
x86 system with Usermanager/payment gateway running on it and several RBs running as hotspots. Customers can sign themselves up for time and create their own usernames/passwords and away they go.
I have heard people do similar things with freeradius, but I decided to go this direction. We also manage our PPPOE DSL customers with user manager.

PC is only solution for User manager service
also fast hard disk because after restart waiting is long