Linux配置hugepage
對於內存較大的Oracle數據庫server，配置HugePage是非常有必要的，以下是配置Huge的步驟：
我的環境：
OS：CentOS release 6.4 (Final)
Oracle：11.2.0.4 RAC
1. 設置memlock
編輯/etc/security/limits.conf
添加：
* Soft memlock 稍小於RAM值
* hard memlock 稍小於RAM值
Memlock值大於sga沒關系的，所以我們能夠設置這個值在我們想要的SGA size和物理內存size之間，這個值得單位是kb
[[email protected] ~]# grep -i memtot /proc/meminfo
MemTotal: 132250576 kB
我們物理內存大小126G，因此我能夠設置memlock為100G。
在2個節點設置：
[[email protected] ~]# tail -2 /etc/security/limits.conf
* soft memlock 104857600
* hard memlock 104857600
設置完成後，以Oracle用戶登錄驗證：
node2-> ulimit -l
104857600
2.
禁用AMM特性須要將memory_max_target, memory_max_target2個參數重置，而不不過設置為0。最好的辦法是創建一個pfile,在pfile中將這2個參數刪除，再依據這個pfile創建spfile.
主要內存參數設置為：
node1->
node1-> grep target /tmp/init.ora
*.pga_aggregate_target=1572864000
*.sga_target=64424509440
SQL> create spfile from pfile=‘/tmp/init.ora‘;
File created.
SQL> startup force
ORA-27102: out of memory
Linux-x86_64 Error: 28: No space left on device
Additional information: -134217728
Additional information: 1
SQL>
出現這個報錯是由於shmall設置的太小。
Shmall表示共享內存的總大小，單位為pagesize的大小。
依據我的配置，最大能支持8G的SGA：
node1-> getconf PAGE_SIZE
4096
node1-> cat /proc/sys/kernel/shmall
2097152
改動shmall並又一次啟動數據庫。改動的方法非常easy。編輯/etc/sysctl.conf：
kernel.shmall= 16252928
就可以。
改動完成kernel.shmall，此時能夠重新啟動數據庫。
SQL> startup nomount pfile=‘/tmp/init.ora‘;
ORACLE instance started.
Total System Global Area 6.4137E+10 bytes
Fixed Size 2269072 bytes
Variable Size 6979321968 bytes
Database Buffers 5.7043E+10 bytes
Redo Buffers 112762880 bytes
SQL>
SQL>
DB啟動後又一次創建spfile：
SQL> create spfile=‘+OCR/sszgdb/spfilesszgdb.ora‘ from pfile=‘/tmp/init.ora‘;
File created.
SQL>
3. 依據Oracle的腳本計算hugepage大小（計算時要確保Oracle已經啟動）。也可自己計算：
Press Enter to proceed...
Recommended setting: vm.nr_hugepages = 30739
node1->
4. 依據腳本的計算值在2個節點編輯/etc/sysctl.conf
增加vm.nr_hugepages = 30739
[[email protected] ~]# grep -i huge /proc/meminfo
AnonHugePages: 602112 kB
HugePages_Total: 30739
HugePages_Free: 30739
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB停止數據庫實例
5. 重新啟動server，一般重新啟動server之後DB也自己主動啟動了。
server和DB重新啟動後能夠通過下面命令驗證大頁的使用情況：
grep -i Hugepages /proc/meminfo
此時查看Oracle的alert日誌，也能夠發現：
Starting ORACLE instance (normal)
************************ Large Pages Information *******************
Per process system memlock (soft) limit = UNLIMITED
Total Shared Global Region in Large Pages = 58 GB (96%)
Large Pages used by this instance: 29761 (58 GB)
Large Pages unused system wide = 24 (48 MB)
Large Pages configured system wide = 30739 (60 GB)
Large Page size = 2048 KB
RECOMMENDATION:
Total System Global Area size is 60 GB. For optimal performance,
prior to the next instance restart:
1. Increase the number of unused large pages by
at least 936 (page size 2048 KB, total size 1872 MB) system wide to
get 100% of the System Global Area allocated with large pages
能夠發現sga並沒有所有放在大頁裏，這樣可能對性能帶來負面影響。Oracle建議我們再添加936個大頁，可見Oracle的大頁腳本計算並不準確，我們須要添加大頁數量，並設置參數Use_large_pages=only。該參數確保Oracle的共享內存所有使用大頁。
再重新啟動DB，此時alert日誌：
************************ Large Pages Information *******************
Parameter use_large_pages = ONLY
Per process system memlock (soft) limit = 100 GB
Total Shared Global Region in Large Pages = 60 GB (100%)
Large Pages used by this instance: 30721 (60 GB)
Large Pages unused system wide = 0 (0 KB)
Large Pages configured system wide = 31675 (62 GB)
Large Page size = 2048 KB
能夠發現sga所有使用了大頁了。
另需確保環境變量DISABLE_HUGETLBFS unset，該變量會禁用Oracle使用Hugepage
附：計算HugePage大小的腳本：
#!/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
Linux配置hugepage