Performance Tunning Your Application Server

Instruction to performance tune OS for JBOSS/Tomcat/WebSphere/Oracle AS

First, you need to set the kernel parameter for shared memory to be at least as big as you need for the amount of memory you want to set aside for the JVM to use as large page memory. Personally, I like to just set it to the maximum amount of memory in the server, so I can play with different heap sizes without having to adjust this every time. You set this by putting the following entry into /etc/sysctl.conf:

Set the kernel Parameter for Shared memory in /etc/sysctl.conf to maximum amount of memory in the system so u don’t have to worry about the heap sizes adjustment .


kernel.shmmax = n for 4 GB server use 4294967296

where n is the number of bytes.

Set a virtual memory kernel parameter of how many large memory pages you want


vm.nr_hugepages = n

where n is the number of pages, based on the page size listed in /proc/meminfo for
Hugepagesize: 2048 kB

So, I wanted to set this to 3GB. I set the parameter to 1536, which is (1024*1024*1024*3)/(1024*1024*2). Which is 3GB divided by 2MB, since 2048 KB is 2MB.

Set another virtual memory parameter, to give permission for your process to access the shared memory segment. In /etc/group, created a new group, called hugetablespace let suppose guid is 1501

Put that group id in /etc/sysctl.conf as follows:
vm.hugetlb_shm_group = 1501

This GUID should be attached to the same user as that with which JBOSS is running .

/etc/security/limits.conf as follows:
jboss soft memlock n
jboss hard memlock n

where n is equal to the number of huge pages, set in vm.nr_hugepages, times the page size from /proc/meminfo, , 1536*2048 = 3145728. This concludes the OS setup, and now we can actually configure the JVM.

The JVM parameter for the Sun JVM is -XX:+UseLargePages use the same large pages /proc/meminfo