Cpu utilization per module in database

Hello, I want to calculate the cpu consumption per module in my database. The basic aim is whether we can add more users or not.

I am using the following query:

set linesize 200

set pagesize 120

col module for a60

SELECT   mymodule "Module", SUM (cpu_time) "CPU Time", SUM (wait_time) "Wait

Time",

         SUM (cpu_time) + SUM (wait_time) "Total Time"

    FROM (SELECT a.module mymodule,

(CASE (session_state)

WHEN 'ON CPU'

THEN wait_time / 100

END

) cpu_time,

(CASE (session_state)

WHEN 'WAITING'

THEN time_waited / 100

END

) wait_time

FROM dba_hist_active_sess_history a, dba_hist_snapshot b

WHERE --b.end_interval_time > sysdate-1