ALERT: Disable Transparent HugePages on SLES11, RHEL6, OEL6 and UEK2 Kernels

随着去ioe的潮流越来越汹涌，随着内存越来越便宜，使用Liunx大内存跑核心业务的系统越来越多。因为大内存，多会话，使得配置HugePages也成了必然的选择，在以前的文章中介绍过怎么去配置HugePages(Liunx系统中Oracle使用HugePages配置)以及因为没有配置Hugepage导致的故障(因未配置Hugepage会话数添增悲剧案例).但是随着Linux 6(RedHat 6, OEL 6, SLES 11 and UEK2 kernels等）的广泛应用,他们所在HugePages方面所具有的新特性(Transparent HugePages)很多人可能还没有注意到,Oracle强烈建议无论是rac还是单实例都关闭该特性.
检查是否启用Transparent HugePages方法

To check if the Transparent HugePages are enabled in your server execute the following:

Default/Enabled setting is  [always]:

# cat /sys/kernel/mm/transparent_hugepage/enabled
[always] never

 Disabled setting is [never]:

# cat /sys/kernel/mm/transparent_hugepage/enabled
always [never]
If "enabled" is NOT set to "[never]", the Transparent HugePages are being used.

You can also issue:

# grep AnonHugePages /proc/meminfo
If the output contains a line like "AnonHugepages: xxxx kB", with a value > 0kB the kernel is using Transparent HugePages.

禁用Transparent HugePages方法

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

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:

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

具体见文档:ALERT Disable Transparent HugePages on SLES11 RHEL6 OEL6 and UEK2 Kernels(Doc ID 1557478.1)