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aio_init.3: New page documenting aio_init(3)
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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.\" Copyright (c) 2010 by Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.TH AIO_INIT 3 2010-10-06 "Linux" "Linux Programmer's Manual"
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.SH NAME
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aio_init \- POSIX asynchronous I/O initialization
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.SH SYNOPSIS
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.nf
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.B #define _GNU_SOURCE
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.B "#include <aio.h>"
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.BI "void aio_init(const struct aioinit *" init );
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.fi
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.sp
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Link with \fI\-lrt\fP.
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.SH DESCRIPTION
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The GNU-specific
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.BR aio_init (3)
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function allows the caller to provide tuning hints to the
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glibc POSIX AIO implementation.
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Use of this function is optional, but to be effective,
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it must be called before employing any other functions in the POSIX AIO API.
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The tuning information is provided in the buffer pointed to by the argument
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.IR init .
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This buffer is a structure of the following form:
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.PP
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.in +4n
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.nf
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struct aioinit {
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int aio_threads; /* Maximum number of threads */
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int aio_num; /* Number of expected simultaneous
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requests */
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int aio_locks; /* Not used */
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int aio_usedba; /* Not used */
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int aio_debug; /* Not used */
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int aio_numusers; /* Not used */
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int aio_idle_time; /* Number of seconds before idle thread
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terminates (since glibc 2.2) */
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int aio_reserved;
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};
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.fi
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.in
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.PP
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The following fields are used in the
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.I aioinit
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structure:
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.TP 15
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.I aio_threads
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This field specifies the maximum number of worker threads that
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may be used by the implementation.
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If the number of outstanding I/O operations exceeds this limit,
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then excess operations will be queued until a worker thread becomes free.
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If this field is specified with a value less than 1, the value 1 is used.
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The default value is 20.
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.TP
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.I aio_num
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This field should specify the maximum number of simultaneous I/O requests
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that the caller expects to enqueue.
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If a value less than 32 is specified for this field,
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it is rounded up to 32.
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.\" FIXME But, if aio_num > 32, the behavior looks strange. See
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.\" http://sourceware.org/bugzilla/show_bug.cgi?id=12083
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The default value is 64.
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.TP
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.I aio_idle_time
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This field specifies the amount of time in seconds that a
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worker thread should wait for further requests before terminating,
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after having completed a previous request.
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The default value is 1.
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.SH VERSIONS
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The
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.BR aio_init ()
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function is available since glibc 2.1.
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.SH CONFORMING TO
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This function is a GNU extension.
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.SH SEE ALSO
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.BR aio (7)
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