Asynchronous I/O

Asynchronous I/O

The Asynchronous Input/Output (I/O) feature contains the following POSIX P1003.4 interface functions:

aio_cancel+: cancel asynchronous read and/or write requests
aio_error: retrieve Asynchronous I/O error status
aio_fsync: asynchronously force I/O completion, and sets errno to ENOSYS
aio_read: begin asynchronous read
aio_return: retrieve return status of Asynchronous I/O operation
aio_suspend+: suspend until Asynchronous I/O Completes
aio_write: begin asynchronous write
lio_listio: issue list of I/O requests

Together they provide a user application with the ability to overlap CPU processing with I/O operations. Additionally, Asynchronous I/O supports the aio_memlock function for high performance database applications.

NOTE: The aio_cancel and aio_suspend functions are supported only in the thread-based implementation of UNIX System V Release 4.2 Multiprocessor (SVR4.2 MP) and UnixWare 2.0. The lio_listio function is supported only for raw slices of hard disks for both SVR4.2 MP, SVR4.2, and UnixWare 2.0.

These routines are more fully described in their respective manual pages.

Notation conventions

The Asynchronous I/O feature supports UNIX System V Release 4.2 (SVR4.2), UNIX System V Release 4.2 Multiprocessor (SVR4.2 MP), and UnixWare 2.0. Functions that can only be used on raw slices of hard disks have been indicated in the following manner:

aio_memlock++

Functions provided for the SVR4.2 MP and UnixWare 2.0 threads-based implementation only have been indicated in the following manner:

aio_cancel+
aio_suspend+