| .TH aio_init 3 2002-09-12 "Linux 2.4" Linux AIO" |
| .SH NAME |
| aio_init \- How to optimize the AIO implementation |
| .SH SYNOPSYS |
| .nf |
| .B #include <errno.h> |
| .sp |
| .br |
| .B #include <aio.h> |
| .sp |
| .br |
| .BI "void aio_init (const struct aioinit *init)" |
| .fi |
| .SH DESCRIPTION |
| |
| The POSIX standard does not specify how the AIO functions are |
| implemented. They could be system calls, but it is also possible to |
| emulate them at userlevel. |
| |
| At the point of this writing, the available implementation is a userlevel |
| implementation which uses threads for handling the enqueued requests. |
| While this implementation requires making some decisions about |
| limitations, hard limitations are something which is best avoided |
| in the GNU C library. Therefore, the GNU C library provides a means |
| for tuning the AIO implementation according to the individual use. |
| |
| .BI "struct aioinit" |
| .PP |
| This data type is used to pass the configuration or tunable parameters |
| to the implementation. The program has to initialize the members of |
| this struct and pass it to the implementation using the |
| .IR aio_init |
| function. |
| .TP |
| .B "int aio_threads" |
| This member specifies the maximal number of threads which may be used |
| at any one time. |
| .TP |
| .B "int aio_num" |
| This number provides an estimate on the maximal number of simultaneously |
| enqueued requests. |
| .TP |
| .B "int aio_locks" |
| Unused. |
| .TP |
| .B "int aio_usedba" |
| Unused. |
| .TP |
| .B "int aio_debug" |
| Unused. |
| .TP |
| .B "int aio_numusers" |
| Unused. |
| .TP |
| .B "int aio_reserved[2]" |
| Unused. |
| .PP |
| This function must be called before any other AIO function. Calling it |
| is completely voluntary, as it is only meant to help the AIO |
| implementation perform better. |
| |
| Before calling the |
| .IR aio_init |
| , function the members of a variable of |
| type |
| .IR "struct aioinit" |
| must be initialized. Then a reference to |
| this variable is passed as the parameter to |
| .IR aio_init |
| which itself |
| may or may not pay attention to the hints. |
| |
| It is a extension which follows a proposal from the SGI implementation in |
| .IR Irix 6 |
| . It is not covered by POSIX.1b or Unix98. |
| .SH "RETURN VALUES" |
| The function has no return value. |
| .SH ERRORS |
| The function has no error cases defined. |
| .SH "SEE ALSO" |
| .BR aio(3), |
| .BR aio_cancel(3), |
| .BR aio_cancel64(3), |
| .BR aio_error(3), |
| .BR aio_error64(3), |
| .BR aio_fsync(3), |
| .BR aio_fsync64(3), |
| .BR aio_read(3), |
| .BR aio_read64(3), |
| .BR aio_return(3), |
| .BR aio_return64(3), |
| .BR aio_suspend(3), |
| .BR aio_suspend64(3), |
| .BR aio_write(3), |
| .BR aio_write64(3), |
| .BR errno(3), |
