A while ago I wrote a post about a specific listener coredump issue which could be solved by 1) installing an oracle patch and 2) by implementing hugepages. I have also linked to an article from Pythian Group Oracle expert Riyaj Shamsudeen, who demonstrated problems with memory page management overheads with big SGAs without hugepages.

Today, I want to document the steps necessary to implement hugepages after doing some research:

• Check your /etc/sysctl.conf shmall and shmmax values. I recommend that you set shmmax bigger or
• Check your current total shared memory segment size. Depending on your “bc -l” skills by summing all byte lines from ipcs -m or by executing a script from metalink Note 401749.1 (which does exactly that). Calculate how many hugepages you need by “cat /proc/meminfo” and dividing it by the pagesize of your platform. (Linux IA64 has 256MB pages for example) I recommend to add 1 extra page for safety.
• Say, you need 200 hugepages. Multiply it with the pagesize and enter this value in
  /etc/security/limits.conf: (values in kb)

oracle soft memlock 2097152
oracle hard memlock 2097152

• Set the parameters in /etc/sysctl.conf:

vm.nr_hugepages=200
vm.hugetlb_shm_group=<group id of dba group from /etc/group>
e.g. vm.hugetlb_shm_group=201

I am going to implement hugepages on Linux Itanium for a Real Application Cluster system. I have read posts that there are different issues regarding startup with srvctl or sqlplus and startup by oracle or root. I will investigate and write more soon.