I want to get the top cpu(us+sy),

If I remember correctly, the top command gives you information about the management plane processes, from which tmm is generally the largest consumer. If you want to dig into CPU utilization within tmm, and particularly within each tmm/cpu, then from the command line:

tmsh show sys cpu

which translates to the following iControlREST syntax:

curl -sk -u 'admin:admin' -H "Content-Type: application/json" -X GET https://x.x.x.x/mgmt/tm/sys/cpu

You'll need to do some additional parsing to get the User and System values that you're looking for, but the information is all there.