linux hugepage 设置

本次操作是完成 centos 6.x 7.x hugepage的设置

oracle 11g 在 linux 下强烈建议启用hugepage，否则如果进程过多的话会导致linux 的 pagetable 过大，物理内存不够用，产生页交换，进而影响oracle的性能。

启用hugepage

在 /etc/security/limits.conf 添加如下行

# vi  /etc/security/limits.conf

oracle           soft    memlock    unlimited
oracle           hard    memlock    unlimited

注意，这里设置的值均以kb为单位的(具体数字依据主机的内存大小)！
设置用户内存配置，有个计算规则是：
实际物理内存 > 锁定内存 >= HugePages_Total*Hugepagesize
这个dba要简单比较下

在/etc/sysctl.conf 添加如下行

# vi /etc/sysctl.conf

vm.nr_hugepages=17000

运行oracle 的 hugepages_set.sh 脚本，给出建议值(必须在oracle启动状态下)
或者手动计算nr_hugepages的公式:
nr_hugepages>=sga(mb)/Hugepagesize(mb)

os 刷新数据

# sync
# echo 3 > /proc/sys/vm/drop_cache

禁用透明 hugepage

临时修改

# echo "never" > /sys/kernel/mm/transparent_hugepage/enabled;
echo "never" > /sys/kernel/mm/transparent_hugepage/defrag;

永久修改(centos 6.x)

# ls -l /etc/grub.conf 
lrwxrwxrwx. 1 root root 22 Jan 11 15:16 /etc/grub.conf -> ../boot/grub/grub.conf
# ls -l /boot/grub/grub.conf 
-rw-------. 1 root root 827 Jan 31 11:01 /boot/grub/grub.conf

 # vi /etc/grub.conf
 transparent_hugepage=never
  

永久修改(centos 7.x)

# vi /etc/default/grub
transparent_hugepage=never

# grub2-mkconfig -o /boot/grub2/grub.cfg 

或者

# vi /etc/rc.local 

if test -f /sys/kernel/mm/transparent_hugepage/enabled; then
   echo "never" > /sys/kernel/mm/transparent_hugepage/enabled
fi
if test -f /sys/kernel/mm/transparent_hugepage/defrag; then
   echo "never" > /sys/kernel/mm/transparent_hugepage/defrag
fi

下面是mos的内容
开始
To disable Transparent HugePages boot time either one of the following 2 methods may be used:

Add the following to the kernel boot line in /etc/grub.conf (a symlink to /boot/grub/grub.conf) and reboot the server (this is the preferred method):

transparent_hugepage=never
Once modified the line will read similar to the following example:

title Oracle Linux Server (2.6.32-300.25.1.el6uek.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-300.25.1.el6uek.x86_64 ro root=LABEL=/ transparent_hugepage=never
initrd /initramfs-2.6.32-300.25.1.el6uek.x86_64.img

OR

Add the following lines in /etc/rc.local and reboot the server (this still can be done on Redhat 7 although rc.local is being deprecated):

if test -f /sys/kernel/mm/transparent_hugepage/enabled; then
echo never > /sys/kernel/mm/transparent_hugepage/enabled
fi
if test -f /sys/kernel/mm/transparent_hugepage/defrag; then
echo never > /sys/kernel/mm/transparent_hugepage/defrag
fi
Please change the file path for RHEL kernel to /sys/kernel/mm/redhat_transparent_hugepage/ accordingly.

结束
grep AnonHugePages /proc/meminfo

确认启用hugepage

# reboot
# cat /proc/meminfo |grep -i huge

参考:
https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt

https://www.oracle.com/technetwork/cn/articles/servers-storage-dev/hugepages-2099009-zhs.html

ALERT: Disable Transparent HugePages on SLES11, RHEL6, RHEL7, OL6, OL7, and UEK2 and above (文档 ID 1557478.1)

Oracle Linux: Shell Script to Calculate Values Recommended Linux HugePages / HugeTLB Configuration (文档 ID 401749.1)