hugepagesize
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lagepage。
下面演示配置hugepage的方法。
系统环境：
OS：CentOS5 x86
Oracle：10.2.0.1
配置过程
检查hugepagesize
| ora_test@root[/root]> grep Hugepagesize /proc/meminfo Hugepagesize: 4096 kB |
配置分配hugepage的数量
nr_hugepages的计算公式:nr_hugepages>=sga(mb)/Hugepagesize(mb)
| ora_test@root[/root]> echo 50 > /proc/sys/vm/nr_hugepages ora_test@root[/root]> sysctl -w vm.nr_hugepages=50 vm.nr_hugepages = 50 ora_test@root[/root]> echo "vm.nr_hugepages=50" >> /etc/sysctl.conf |
检查hugepage的分配情况
| ora_test@root[/root]> grep HugePages_Total /proc/meminfo HugePages_Total: 6 |
这里显示的值为6，小于我配置的数量50，所以需要重启
| ora_test@root[/root]> reboot Broadcast message from root (pts/1) (Mon Jan 25 09:38:04 2010): The system is going down for reboot NOW! |
重启之后，检查hugepage的分配情况
| ora_test@root[/root]> grep HugePages_Total /proc/meminfo HugePages_Total: 50 |
现在确认hugepage已经分配了50个单位（50×4096kb=200mb）
http://cnhtm.itpub.net/post/39970/496273
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
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.%dn",$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