如何使用Hugepage参数

一.系统当前状态
[root@node1 ora11g]# cat /proc/meminfo | grep -i hugepages
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
Hugepagesize: 2048 kB
[root@node1 ora11g]# uname -sr
Linux 2.6.18-238.19.1.el5
cat /proc/meminfo|grep PageT
PageTables: 44748 kB
二.计算nr_hugepages值
#!/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.
#
# This script is provided by Doc ID 401749.1 from My Oracle Support
# http://support.oracle.com

# Welcome text
echo "
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..."

read

# 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}'`

# Initialize the counter
NUM_PG=0

# 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

RES_BYTES=`echo "$NUM_PG * $HPG_SZ * 1024" | bc -q`

# An SGA less than 100MB does not make sense
# Bail out if that is the case
if [ $RES_BYTES -lt 100000000 ]; then
echo "***********"
echo "** ERROR **"
echo "***********"
echo "Sorry! There are not enough total of shared memory segments allocated for
HugePages configuration. HugePages can only be used for shared memory segments
that you can list by command:

# ipcs -m

of a size that can match an Oracle Database SGA. Please make sure that:
* Oracle Database instance is up and running
* Oracle Database 11g Automatic Memory Management (AMM) is not configured"
exit 1
fi

# 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
1.Configuring the Script
Create a text file named hugepages_settings.sh
Copy the contents below in the file
Run
$ chmod +x hugepages_settings.sh
2.Running the Script
Be sure that all applications that are meant to use HugePage / HugeTLB are running at the time the script is to be run.
This includes the Oracle RDBMS instances and ASM instances in addition to other applications.
Be sure that you have /bin and /usr/bin in $PATH
Run
$ ./hugepages_settings.sh
三.修改系统配置
1./etc/sysctl.conf
vm.nr_hugepages = 770

假设分配16G内存给用于hugepage
notes:内存*1024*1024/Hugepagesize
计算公式：16*1024*1024/2048=8192
2./etc/security/limits.conf
oracle soft memlock 102400
oracle hard memlock 102400
单位K
计算公式：>=HugePages_Total*Hugepagesize
四.重启系统检查配置是否生效
[root@node1 ~]# cat /proc/meminfo | grep -i hugepages
HugePages_Total: 770
HugePages_Free: 770
HugePages_Rsvd: 0
Hugepagesize: 2048 kB
五.启动数据库并验证
[oracle@node1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.5.0 - Production on Wed Jan 4 16:06:48 2012

Copyright (c) 1982, 2010, Oracle. All Rights Reserved.

Connected to an idle instance.

SQL> startup
ORACLE instance started.

Total System Global Area 1610612736 bytes
Fixed Size 2096632 bytes
Variable Size 486539784 bytes
Database Buffers 1107296256 bytes
Redo Buffers 14680064 bytes
Database mounted.
Database opened.
SQL> exit

[oracle@node1 ~]$ grep Huge /proc/meminfo
HugePages_Total: 770
HugePages_Free: 591
HugePages_Rsvd: 590
Hugepagesize: 2048 kB
[oracle@node1 ~]$ cat /proc/meminfo|grep PageT
PageTables: 13216 kB
HugePages_Free<>HugePages_Total,PageTables变小
证明HugePages配置成功

六.补充说明
1.在数据库内存服务器内存比较大的时候，可以考虑使用该功能，提高系统性能
2.对于Oracl 11g,如果需要使用此功能，需要关闭AMM功能(需要衡量)

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