CentOS6/7中禁用Transparent Huge Pages(大页)
RHEL6/CentOS6版本开始引入了Transparent Huge Pages(THP)，从CentOS7版本开始，该特性默认就会启用。尽管THP的本意是为提升内存的性能，不过某些数据库厂商还是建议直接关闭THP(Oracle、MariaDB、MongoDB、Redis等)，否则可能会导致性能出现下降，
查看THP的启用状态：
[root@localhost ~]# cat /sys/kernel/mm/transparent_hugepage/defrag
[always] madvise never
[root@localhost ~]# cat /sys/kernel/mm/transparent_hugepage/enabled
[always] madvise never这个状态就说明都是启用.
禁用THP立即生效：
echo 'never' > /sys/kernel/mm/transparent_hugepage/enabled
echo 'never' > /sys/kernel/mm/transparent_hugepage/defrag写入启动项，下次重启时生效：
chmod +x /etc/rc.d/rc.local
vim /etc/rc.d/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最后重启系统，以后再检查THP应该就是被禁用了
[root@localhost ~]# cat /sys/kernel/mm/transparent_hugepage/enabled
always madvise [never]
[root@localhost ~]# cat /sys/kernel/mm/transparent_hugepage/defrag
always madvise [never]