标签：both EXT4 Direct used Does asynchronous file

原文链接：https://access.redhat.com/solutions/322213

https://access.redhat.com/solutions/322213

 SOLUTION UNVERIFIED - 已更新 2014年七月31日02:42 - 

English 

环境

• Red Hat Enterprise Linux 6
• EXT4 Filesystem

问题

• Does EXT4 support asynchronous I/O or direct I/O?
• If EXT4 supports these features, how are they used?

决议

• EXT4 file system supports both the asynchronous I/O and the Direct I/O features.

• By default, asynchronous I/O is enabled.

• If Direct I/O is needed, the application should use the O_DIRECT flag while doing the 'open()' system call.

• If Direct I/O has to be used with an existing EXT4 filesystem, the 'sync' mount option should be used both while mounting manually, and when mounting via the /etc/fstab file for boot time activation.

NOTE: If both Direct I/O (DIO) and the 'sync' options are used, file performance will be decreased because the file system will over-ride the use of the kernel page cache. This increases the I/O calls to the underlying disk, which is hundreds of times slower than accessing data via the primary L1-L2 caches. It is best to understand the consequences/drawbacks of DIO prior to implementing it.

标签：both,EXT4,Direct,used,Does,asynchronous,file
来源： https://blog.csdn.net/msdnchina/article/details/98663071

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