linux+ 大页内存的设置
linux 大页
1、为什么要设置大页
HugePages is crucial for faster Oracle database performance on Linux if you have a large RAM and SGA. If your combined database SGAs is large (like more than 8GB, can even be important for smaller), you will need HugePages configured. Note that the size of the SGA matters.
默认linux的页面大小是2k，设置大页后是2m，那么要少取512次
2、配置大页内存
(1)
/etc/security/limits.conf
soft memlock 60397977
hard memlock 60397977
hard memlock 60397977
这个过程中使用memlock标记，用于设置每个用户允许的最大内存使用情况。这个取值可以设置为数据库服务器物理内存大小。
# sysctl -w kernel.shmmax=53687091200
应该大于sga的大小，用于设置单个共享内存段的大小
(2)
su - oracle
$ ulimit -l
60397977
60397977
(3) 如果数据库的版本是11g，或者以后的版本，那么需要关闭amm，设置memory_target=0 或者 memory_max_size=0
否则 就会
ORA-00845: MEMORY_TARGET not supported on this system
大页内存的设置不适合于amm管理内存，因为amm管理的内存包括sga+pga，在内内存管理，而大页的设置，是需要大于sga的，如果使用amm自动管理，那么大页的大小不好控制
如果要使用大页 来管理内存，那么需要使用asmm来管理内存，设置 memory_target=0 或者 memory_max_size=0s
(4)确保所有的数据库实例都在运行，包括asm实例
hugepages_settings.sh
#!/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
#
# 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 = $NUM_PG" ;;
esac
# End
'2.4') HUGETLB_POOL=`echo "$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" ;;
esac
# End
$ ./hugepages_settings.sh
...
Recommended setting: vm.nr_hugepages = 1496
...
Recommended setting: vm.nr_hugepages = 1496
hugepage目前只能用于共享内存段等少量内存类型，如果手工设置公式大概是vm.nr_hugepages =sga*1024/2+200，就是要sga要大一小，nr_hugepages并不包括pga的大小
（5）
/etc/sysctl.conf
vm.nr_hugepages = 1496
（6）重启数据库和服务器
SQL> startup nomount
（7）检查
# ipcs
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x00000000 4980742 oracle 640 2097152 14
0x00000000 5013511 oracle 600 51539607552 14
0x4d06d874 5046280 oracle 640 114688 14
key shmid owner perms bytes nattch status
0x00000000 4980742 oracle 640 2097152 14
0x00000000 5013511 oracle 600 51539607552 14
0x4d06d874 5046280 oracle 640 114688 14
# grep 4980742 /proc/24048/maps # grep by shmid
40000000000-40000200000 rw-s 00000000 00:07 4980742 /SYSV00000000 (deleted)
40000000000-40000200000 rw-s 00000000 00:07 4980742 /SYSV00000000 (deleted)
# grep HugePages /proc/meminfo
HugePages_Total: 1496
HugePages_Free: 485
HugePages_Rsvd: 446
HugePages_Surp: 0
HugePages_Total: 1496
HugePages_Free: 485
HugePages_Rsvd: 446
HugePages_Surp: 0
HugePages_Free 必须小于
HugePages_Total，必须要有一些
，
HugePages_Rsvd
这是给预留用的
Troubleshooting
Some of the common problems and how to troubleshoot them are listed in the following table:
| Symptom | Possible Cause | Troubleshooting Action |
|---|---|---|
| System is running out of memory or swapping | Not enough HugePages to cover the SGA(s) and therefore the area reserved for HugePages are wasted where SGAs are allocated through regular pages. | Review your HugePages configuration to make sure that all SGA(s) are covered. |
| Databases fail to start | memlock limits are not set properly | Make sure the settings in limits.conf apply to database owner account. |
| One of the database fail to start while another is up | The SGA of the specific database could not find available HugePages and remaining RAM is not enough. | Make sure that the RAM and HugePages are enough to cover all your database SGAs |
| Cluster Ready Services (CRS) fail to start | HugePages configured too large (maybe larger than installed RAM) | Make sure the total SGA is less than the installed RAM and re-calculate HugePages. |
| HugePages_Total = HugePages_Free | HugePages are not used at all. No database instances are up or using AMM. | Disable AMM and make sure that the database instances are up. See Doc ID 1373255.1 |
| Database started successfully and the performance is slow | The SGA of the specific database could not find available HugePages and therefore the SGA is handled by regular pages, which leads to slow performance | Make sure that the HugePages are many enough to cover all your database SGAs |