在Linux 中为oracle配置hugepage的方法

neocai

　　在Linux中配置hugepage可以提高oracle的性能，减少oracle sga的页交换，类似于aix中的largepage。
　　下面演示配置hugepage的方法。
　　系统环境：
　　OS：CentOS6.4 64bit
　　Oracle：10.2.0.5
　　配置过程
　　检查hugepagesize
[oracle@ehrtest ~]$ grep Hugepagesize /proc/meminfo　　Hugepagesize:       2048 kB
　　查看默认hugepage的值
　　nr_hugepages的计算公式:nr_hugepages >= sga(mb)/Hugepagesize(mb)
　　[oracle@ehrtest ~]$ sysctl -a|grep nr_huge
　　vm.nr_hugepages = 0
　　检查hugepage的分配情况
[oracle@ehrtest ~]$ grep HugePages_Total /proc/meminfo　　HugePages_Total:       0
使用oracle 提供的脚本计算出系统最佳值　　[oracle@ehrtest ~]$ sh auto_vm_huge.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 note following:
　　* For ASM instance, it needs to configure ASMM instead of AMM.
　　* The 'pga_aggregate_target' is outside the SGA and
　　you should accommodate this while calculating SGA size.
　　* In case you changes the DB SGA size,
　　as the new SGA will not fit in the previous HugePages configuration,
　　it had better disable the whole HugePages,
　　start the DB with new SGA size and run the script again.
　　And 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 = 482
配置oracle用户的memlock　　需要修改/etc/security/limits.conf文件，加入标记为红色的两行
　　计算公式为：>=HugePages_Total×1024，我这里设置了2倍的值，即：2×50×1024=102400
ora_test@root[/root]> cat /etc/security/limits.conf|grep lock　　# - memlock - max locked-in-memory address space (KB)
　　# - locks - max number of file locks the user can hold
　　oracle soft memlock 102400
　　oracle hard memlock 102400
　　检查memlock情况
　　切换到oracle用户身份，使用ulimit -l命令检查memlock情况
ora_test@root[/root]> su - oracle　　ora_test@oracle[/home/oracle]> ulimit -l
　　102400
　　启动数据库
ora_test@oracle[/home/oracle]> sqlplus / as sysdba　　SQL*Plus: Release 10.2.0.1.0 - Production on Mon Jan 25 09:50:33 2010
　　Copyright (c) 1982, 2005, Oracle. All rights reserved.
　　Connected to an idle instance.
　　idle> startup
　　ORACLE instance started.
　　Total System Global Area 167772160 bytes
　　Fixed Size 1218292 bytes
　　Variable Size 67111180 bytes
　　Database Buffers 92274688 bytes
　　Redo Buffers 7168000 bytes
　　Database mounted.
　　Database opened.
　　idle> exit
　　Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
　　With the Partitioning, OLAP and Data Mining options
　　检查是否已经使用了hugepage
ora_test@oracle[/home/oracle]> grep HugePages_Free /proc/meminfo　　HugePages_Free: 30
　　这里显示剩余的hugepage为30，小于HugePages_Total（50），证明oracle已经使用了hugepage
　　--end--
　　为何oracle一起来，系统就会有swap？
　　db是11g，total memory 是16g ，swap 是8g，分给sga_target=8g,pga_aggregate_target=3g.按理说，这个内存分配也不会导致oracle吞噬过多内存导 致系统发生swap，可现在只要db起来，用vmsta 命令观察就会出现swap， 类似如下。
　　procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
　　r b swpd free buff cache si so  bi  bo in cs us sy id wa st
　　0 0 168524 87336  340 26356 128 3014 178 3054 1305 417 0 1 94 5 0
　　0 3 168524 81336  480 29052 1798  0 3166 8 1243 687 0 0 94 6 0
　　0 0 171024 85292  496 28984 880 1500 1176 1500 1225 612 0 0 89 11 0
　　0 0 171024 85292  496 28960 24  0  24 0 1055 348 0 0 99 0 0
　　0 3 172284 81960  512 34860 372 1158 430 1230 1307 1496 0 2 94 4 0
　　0 1 167072 84424  320 38828 1564 210 1716 230 1545 2796 0 3 85 12 0
　　0 1 167072 84008  340 39152 286  0 362  18 1115 504 0 0 96 4 0
　　0 0 167072 83764  352 39392 34  0  94 6 1069 344 0 0 99 0 0
　　0 0 167072 83764  352 39580 32  0  32 0 1072 347 0 0 100 0 0
　　0 0 167072 82896  352 39568 410  0 410 0 1075 367 0 0 99 1 0
　　我看了alert log,没有其他报错。现在系统非常慢，大伙帮我分析分析。
　　QUOTE:
原帖由 oracle_kai 于 2010-12-7 18:28 发表 http://www.itpub.net/images/common/back.gif　　系统使用的就是hugepage，但问题也就出现在hugepage 参数的设置上面。
　　原先vm.nr_hugepages = 41984
　　cat /proc/memory|grep HugePages_Total
　　HugePages_Total=7925
　　7925*2m 几乎就是整个os内存了。
　　后来修改该参数，参考sga=8g，所以新设vm.nr_hugepages =4096
　　重启机器，oracle起来后memory swap 消失，系统反应也正常。
　　#!/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