环境： OEL 6.5 64bit + Oracle 11.2.0.4 + 32G内存 [11GSGA]

在数据库启动中Alert日志有如下提示信息：

************************ Large Pages Information *******************
Per process system memlock (soft) limit = 64 KB
Total Shared Global Region in Large Pages = 0 KB (0%)
Large Pages used by this instance: 0 (0 KB)
Large Pages unused system wide = 0 (0 KB)
Large Pages configured system wide = 0 (0 KB)
Large Page size = 2048 KB
RECOMMENDATION:
Total System Global Area size is 11 GB. For optimal performance,
prior to the next instance restart:
1. Increase the number of unused large pages by
at least 5761 (page size 2048 KB, total size 11 GB) system wide to
get 100% of the System Global Area allocated with large pages
2. Large pages are automatically locked into physical memory.
Increase the per process memlock (soft) limit to at least 11 GB to lock
100% System Global Area\'s large pages into physical memory
********************************************************************

看来这样大的内存占用势必需要配置HugePages 提高性能。

在MY ORACLE SUPPORT 中 Shell Script to Calculate Values Recommended Linux HugePages / HugeTLB Configuration (Doc ID 401749.1)
提供了计算vm.nr_hugepages的具体脚本。

点击(此处)折叠或打开

#!/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 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...\"
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 $2}\'`
if [ -z \"$HPG_SZ\" ];then
echo \"The hugepages may not be supported in the system where the script is being executed.\"
exit 1
fi
# Initialize the counter
NUM_PG=0
# Cumulative number of pages required to handle the running shared memory segments
for SEG_BYTES in `ipcs -m | cut -c44-300 | awk \'{print $1}\' | grep \"[0-9][0-9]*\"`
do
MIN_PG=`echo \"$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
\'2.2\') echo \"Kernel version $KERN is not supported. Exiting.\" ;;
\'2.4\') HUGETLB_POOL=`echo \"$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\" ;;
\'3.8\') echo \"Recommended setting: vm.nr_hugepages = $NUM_PG\" ;;
esac
# End

根据执行结结果配置 /etc/sysctl.conf 文件，增加vm.nr_hugepages=****；

如果配置到此，仅仅完成了第一步，在数据库启动时依然有如下提示信息：

点击(此处)折叠或打开

************************ Large Pages Information *******************
Per process system memlock (soft) limit = 64 KB
Total Shared Global Region in Large Pages = 0 KB (0%)
Large Pages used by this instance: 0 (0 KB)
Large Pages unused system wide = 5764 (11 GB)
Large Pages configured system wide = 5764 (11 GB)
Large Page size = 2048 KB
RECOMMENDATION:
Total System Global Area size is 11 GB. For optimal performance,
prior to the next instance restart:
1. Large pages are automatically locked into physical memory.
Increase the per process memlock (soft) limit to at least 11 GB to lock
100% System Global Area\'s large pages into physical memory
********************************************************************

根据提示需要将分配的内存Lock 在屋里内存中。

可以参考MY ORACLE SUPPORT 中 HugePages on Oracle Linux 64-bit (Doc ID 361468.1)

配置 /etc/security/limits.conf 文件

点击(此处)折叠或打开

soft memlock ******
hard memlock ******

其中具体数值需要大于SGA大小。
至此配置完成，重新启动后，Alert日志出现以下内容：

点击(此处)折叠或打开

************************ Large Pages Information *******************
Per process system memlock (soft) limit = 12 GB
Total Shared Global Region in Large Pages = 11 GB (100%)
Large Pages used by this instance: 5761 (11 GB)
Large Pages unused system wide = 3 (6144 KB)
Large Pages configured system wide = 5764 (11 GB)
Large Page size = 2048 KB
********************************************************************

下面图片详细解释了HugePages

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linux 关于 HugePages 的配置

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