rc.local重启后不执行

使用ecs centos6.5
装redis后提示
WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled.
于是我在
/etc/rc.local中添加了如下一句
echo never > /sys/kernel/mm/transparent_hugepage/enabled
可是重启后任然无效，需要手动执行一次
怎么回事呢？