Post-Install Database Tasks - Oracle Exadata Recipes: A Problem-Solution Approach - page 593

■ Note oracle aMM and HugePages are incompatible. please refer to Mos note 361323.1 for details.

4. Determine your HugePages kernel parameter setting, vm.nr_hugepages, to the

appropriate value for your environment. The appropriate value can be determined by
running hugepages_settings.sh, which you can download from MOS note 40179.1. Ensure
you have all of your databases up when running this command to provide the most
accurate setting:

[root@cm01dbm01 ~]# ./hugepages_settings.sh

This script is provided by Doc ID 401749.1 from My Oracle Support
( http://support.oracle.com ) where it is intended to compute values for
the recommended HugePages/HugeTLB configuration for the current shared
memory segments. Before proceeding with the execution please make sure
that:
* Oracle Database instance(s) are up and running
* Oracle Database 11g Automatic Memory Management (AMM) is not setup
(See Doc ID 749851.1)
* The shared memory segments can be listed by command:
# ipcs -m

Press Enter to proceed...

Recommended setting: vm.nr_hugepages = 25226
[root@cm01dbm01 ~]#

5. For the case in the preceding example, the script is recommending a value of 25226 for our

vm.nr_hugepages kernel parameter. Check your current setting on each compute node by
running the sysctl command:

[root@cm01dbm01 ~]# sysctl -a|grep huge
vm.hugetlb_shm_group = 0
vm.nr_hugepages = 16388
[root@cm01dbm01 ~]#

As you can see from this output, on this Exadata Compute Node we had at some point configured a
smaller HugePages setting than what is currently recommended.

6. Once you've confirmed the value for vm.nr_hugepages , change your kernel parameter

accordingly. We recommend editing /etc/sysctl.conf and running sysctl -p to
maintain consistency across reboots:

[root@cm01dbm01 ~]# grep nr_hugepages /etc/sysctl.conf
# bug 8268393 remove vm.nr_hugepages = 2048
vm.nr_hugepages = 25226
[root@cm01dbm01 ~]# sysctl -p
<< output omitted >>
vm.nr_hugepages = 25226
<< output omitted >>
[root@cm01dbm01 ~]# sysctl -a|grep huge