https://access.redhat.com/solutions/143043

SOLUTION 已验证 - 已更新 2014年三月20日21:12 - 

环境

• Red Hat Enterprise Linux
• Asynchronous IO

问题

• Is there any system wide setting to enable async IO

决议

• No, there is no option to enable async IO system wide. It has to be done from the application side and application must be capable of using async IO.

• For instance Oracle can use both async and direct IO by setting the mount option filesystemio_options=setall and filesystemio_options=asynch to enable only async IO.

根源

• The AIO model is very different from the traditional UNIX model. It can't be used system wide unless application is aware on how to use this.

诊断步骤

• The following files can be used to monitor the use of async IO in the system:
  • /proc/sys/fs/aio-nr tells the number of active AIO transactions.
  • /proc/sys/fs/aio-max-nr tells the total number of concurrent IO AIO transactions that can take place system wide.

转载者注：
/proc/sys/fs/aio-nr 是看当前the number of active AIO transactions.

/proc/sys/fs/aio-max-nr是在 system wide层面，concurrent IO AIO transactions 发生过的最大数量。