liferay performance issue on linux

I have Liferay 6 with Tomcat system setup on two machines:

Machine 1: Windows 2003 Server 2GB RAM, 2Gh CPU Mysql Ver 14.14 Distrib 5.1.49 Liferay 6.0.6 with Tomcat 6

Machine 2: Linux CentOS 5.5 4GB RAM, 2Gh CPU Mysql Ver 14.14 Distrib 5.5.10 Liferay 6.0.6 with Tomcat 6

Both the liferay systems are having identical startup parameters and mysql configurations. The liferay system contains a custom theme and a servlet filter hook checking each URL access.

We have written a Grinder script to test the load of the system starting with 50 concurrent users .

The test script does the following things:

1. Open home page
2. Login with username/password
3. Enter security key (custom portlet)
4. Move to a private community
5. Logout

On Windows system the response time is as expected (nearly 40 seconds mean time for each test in Grinder). However on the Linux system the response time is too high (nearly 4mins) for the same operations.

We tried revising the mysql, tomcat, connection pool and few other parameters but all resulting the same. Also the liferay were tested using mysql of the other machine (machine 1 liferay -> machine 2 mysql)

We are facing the same issue on Linux machines in ou开发者_C百科r test environment and also at our client's end.

This looks like a duplicate question. I suspect your issue is related to memory / jvm configuration and specifically garbage collection. High CPU utilization under small loads tend to point in that direction.

In your Grinder script, have you set each of the steps as a separate transaction? This will allow you to see how much time each step is taking. It might be useful to know if everything is slower across the board, or if it's just one transaction type that's slowing you down.

Also, is there anything in the Tomcat logs on the Linux box you aren't seeing on windows? Unexpected java stack traces, etc?

Finally, are the databases on each machine identical? Do they have the same amount of data? Do they have the same indexes?

edit: Is it one transaction that's taking up all the extra time, or is each transaction slower? When you run 'top' on your linux box, is it the tomcat java process that's eating all your CPU, or some other process?