注意：大页只对SGA组件起作用，对PGA、UGA无效。如果启用大页，无需设置pre_page_sga，lock_sga（因为使用hugePage管理的内存不能被Swap）。如果使用了HugePage，11g/12c新特性AMM(Automatic Memory Management)就不能使用了，但是ASMM(Automatic Shared Memory Management)可以继续使用。
如何在Windows上启用大页
A.找到下面的选项
10g:HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_OraDb10g_home1
11g:HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_OraDb11g_home1
ORA_LPENABLE=1 对所有实例启用大页
ORA_<ORACLE_SID>_LPENABLE=1 只对特定的实例启用大页
Starting ORACLE instance (normal)
Large page enabled : 1
Large page size : 2097152
Large page request size : 33554432
如何在Linux上启用大页
1.Edit the memlock setting in the /etc/security/limits.conf file. The memlock setting is specified in KB and set slightly lesser than the installed RAM. For example, if you have 64GB RAM installed, add the following entries to increase the max locked memory limit:
* soft memlock 60397977
* hard memlock 60397977
2.Login as the oracle user again and run the ulimit -l command to verify the new memlock setting:
$ ulimit -l
60397977
3.Run the following command to display the value of Hugepagesize variable:
$ grep Hugepagesize /proc/meminfo
4.Complete the following procedure to create a script that computes recommended values for hugepages configuration for the current shared memory segments:
a.Create a text file named hugepages_settings.sh
b.Add the following content in the file:
#!/bin/bash
#
# hugepages_settings.sh
#
# Linux bash script to compute values for the
# recommended HugePages/HugeTLB configuration
#
# Note: This script does calculation for all shared memory
# segments available when the script is run, no matter it
# is an Oracle RDBMS shared memory segment or not.
# Check for the kernel version
KERN=`uname -r | awk -F. '{ printf("%d.%d\n",$1,$2); }'`
# Find out the HugePage size
HPG_SZ=`grep Hugepagesize /proc/meminfo | awk {'print $2'}`
# Start from 1 pages to be on the safe side and guarantee 1 free HugePage
NUM_PG=1
# Cumulative number of pages required to handle the running shared memory segments
for SEG_BYTES in `ipcs -m | awk {'print $5'} | grep "[0-9][0-9]*"`
do
MIN_PG=`echo "$SEG_BYTES/($HPG_SZ*1024)" | bc -q`
if [ $MIN_PG -gt 0 ]; then
NUM_PG=`echo "$NUM_PG+$MIN_PG+1" | bc -q`
fi
done
# Finish with results
case $KERN in
'2.4') HUGETLB_POOL=`echo "$NUM_PG*$HPG_SZ/1024" | bc -q`;
echo "Recommended setting: vm.hugetlb_pool = $HUGETLB_POOL" ;;
'2.6') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
*) echo "Unrecognized kernel version $KERN. Exiting." ;;
esac
# End
c.Run the following command to change the permission of the file:
$ chmod +x hugepages_settings.sh
5.Run the hugepages_settings.sh script to compute the values for hugepages configuration:
$ ./hugepages_settings.sh
6.Set the following kernel parameter:
# sysctl -w vm.nr_hugepages=value_displayed_in_step_5
7.To make the value of the parameter available for every time you restart the computer, edit the /etc/sysctl.conf file and add the following entry:
vm.nr_hugepages=value_displayed_in_step_5
8.Restart the server.
$ grep Huge /proc/meminfo
Reference
http://docs.oracle.com/cd/E11882_01/win.112/e10845/tuning.htm#NTQRF090
http://docs.oracle.com/cd/E11882_01/server.112/e10839/appi_vlm.htm#UNXAR396
