Is there any command available to enable O_DIRECT on a extX filesystem ?

https://access.redhat.com/solutions/696903

 SOLUTION UNVERIFIED - 已更新 2015年二月8日10:36 - 

English 

环境

• Red Hat Enterprise Linux (ALL)

问题

• Is there any command available to enable O_DIRECT on a ext4 filesystem ?
• How to enable O_DIRECT on any file system, so that data is directly written to disk without using the cache?

决议

• O_DIRECT is neither a filesystem feature nor there is a command to enable the same.
• O_DIRECT is a status flag passed to fcntl(2) by an application while opening a file or creating a file.

根源

• O_DIRECT is not a file system wide option and is a status flag which is passed by the application while opening/creating a file.

From man open(2)

Raw

O_DIRECT (Since Linux 2.4.10)
Try to minimize cache effects of the I/O to and from this file.  In general this will degrade performance, but it is useful 
in special situations, such as when applications do their own caching.  File I/O is done directly to/from user space 
buffers. The I/O is synchronous, that is, at the completion of a read(2) or write(2), data is  guaranteed  to have been 
transferred.