On the web server processor usage is not released even though users have been disconnected

Hello

I have a web server with the following characteristics:

System Config SPARC T5-2
Machine Architecture sun4v sparc
Clock Frequency (MHz) 3600
Memory Size (MB) 8192
Local Disk Space (GB) 1026.7
Total CPU Sockets 1
Total CPU Cores 2
Total CPU Cores Enabled 2
Total CPU Threads 16
Count 1 CPU Board

Web logic 12 c,
tool EnterpriseOne HTML Server release 9.1.4.3-2014_12_02 02-17

Currently an average of 180 concurrent users and processor usage reaches approximately 75% are connected. At night when only 2 users are connected using processor remains the same, processor usage even though only 2 users are connected is not released. The next day with the number of concurrent users the user response is too slow to correct this problem is to restart the web instance JDE and everything returns to normal,