Setting up Hugepages for Oracle

use scripts etc to  calculate the right number of pages - or take an estimated guess.

SHOW SGA will give you the current SGA size you need.

I wanted 8G reserved for DB pages

Usual hugepage size is 2M -  you can see this from one of the entries in  /proc

 grep Hugepagesize /proc/meminfo
Hugepagesize:       2048 kB

OK so for 8G reserved 8g/2M = 4096 

add that number to /etc/sysctl.conf

vm.nr_hugepages = 4096

and reboot 

once the instances come up have a look at the Alert Log 

(this is 12.1.0.2 ) 

*********************************************************************

Thu Nov 26 10:08:41 2015

Dump of system resources acquired for SHARED GLOBAL AREA (SGA)

Thu Nov 26 10:08:41 2015

 Per process system memlock (soft) limit = 128G

Thu Nov 26 10:08:41 2015

 Expected per process system memlock (soft) limit to lock

 SHARED GLOBAL AREA (SGA) into memory: 1922M

Thu Nov 26 10:08:41 2015

 Available system pagesizes:

  4K, 2048K

Thu Nov 26 10:08:41 2015

 Supported system pagesize(s):

Thu Nov 26 10:08:41 2015

  PAGESIZE  AVAILABLE_PAGES  EXPECTED_PAGES  ALLOCATED_PAGES  ERROR(s)

Thu Nov 26 10:08:41 2015

        4K       Configured               3               3        NONE

Thu Nov 26 10:08:41 2015

     2048K             4096             961             961        NONE

Thu Nov 26 10:08:41 2015

**********************************************************************

we can see the SGA being allocated into the hugepages