Linux-AIO/AIO.pm

=head1 NAME

Linux::AIO - linux-specific aio implemented using clone

=head1 SYNOPSIS

 use Linux::AIO;

=head1 DESCRIPTION

This module implements asynchronous i/o using the means available to linux
- clone. It does not hook into the POSIX aio_* functions because linux
does not yet support these in the kernel (and even if, it would only allow
aio_read and write, not open and stat).

Instead, in this module a number of (non-posix) threads are started that
execute your read/writes and signal their completion. You don't need
thread support in your libc or perl, and the threads created by this
module will not be visible to the pthreads library.

NOTICE: the threads created by this module will automatically be killed
when the thread calling min_parallel exits. Make sure you only ever call
min_parallel from the same thread that loaded this module.

Although the module will work with threads, it is not reentrant, so use
appropriate locking yourself.

=over 4

=cut

package Linux::AIO;

use base 'Exporter';

BEGIN {
   $VERSION = 1.6;

   @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink);
   @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs);

   require XSLoader;
   XSLoader::load Linux::AIO, $VERSION;
}

=item Linux::AIO::min_parallel $nthreads

Set the minimum number of AIO threads to C<$nthreads>. The default is
C<1>, which means a single asynchronous operation can be done at one time
(the number of outstanding operations, however, is unlimited).

It is recommended to keep the number of threads low, as some linux
kernel versions will scale negatively with the number of threads (higher
parallelity => MUCH higher latency).

=item Linux::AIO::max_parallel $nthreads

Sets the maximum number of AIO threads to C<$nthreads>. If more than
the specified number of threads are currently running, kill them. This
function blocks until the limit is reached.

This module automatically runs C<max_parallel 0> at program end, to ensure
that all threads are killed and that there are no outstanding requests.

=item $fileno = Linux::AIO::poll_fileno

Return the I<request result pipe filehandle>. This filehandle must be
polled for reading by some mechanism outside this module (e.g. Event
or select, see below). If the pipe becomes readable you have to call
C<poll_cb> to check the results.

=item Linux::AIO::poll_cb

Process all outstanding events on the result pipe. You have to call this
regularly. Returns the number of events processed. Returns immediately
when no events are outstanding.

You can use Event to multiplex, e.g.:

   Event->io (fd => Linux::AIO::poll_fileno,
              poll => 'r', async => 1,
              cb => \&Linux::AIO::poll_cb );

=item Linux::AIO::poll_wait

Wait till the result filehandle becomes ready for reading (simply does a
select on the filehandle. This is useful if you want to synchronously wait
for some requests to finish).

=item Linux::AIO::nreqs

Returns the number of requests currently outstanding.

=item aio_open  $pathname, $flags, $mode, $callback

Asynchronously open or create a file and call the callback with the
filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this
might change in the future).

=item aio_close $fh, $callback

Asynchronously close a file and call the callback with the result code.

=item aio_read  $fh,$offset,$length, $data,$dataoffset,$callback

=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback

Reads or writes C<length> bytes from the specified C<fh> and C<offset>
into the scalar given by C<data> and offset C<dataoffset> and calls the
callback without the actual number of bytes read (or C<undef> on error).

=item aio_stat  $fh_or_path, $callback

=item aio_lstat $fh, $callback

Works like perl's C<stat> or C<lstat> in void context. The callback will
be called after the stat and the results will be available using C<stat _>
or C<-s _> etc...

Currently, the stats are always 64-bit-stats, i.e. instead of returning an
error when stat'ing a large file, the results will be silently truncated
unless perl itself is compiled with large file support.

=item aio_unlink  $pathname, $callback

Asynchronously unlink a file.

=cut

min_parallel 1;

END {
   max_parallel 0;
}

1;

=back

=head1 BUGS

This module has been extensively tested in a large and very busy webserver
for many years now.

   - aio_open gives a fd, but all other functions expect a perl filehandle.

=head1 SEE ALSO

L<Coro>.

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

Revision:	1.26
Committed:	Thu Jul 7 23:17:23 2005 UTC (18 years, 10 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_6
Changes since 1.25:	+1 -1 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3			Linux::AIO - linux-specific aio implemented using clone
4
5			=head1 SYNOPSIS
6
7			use Linux::AIO;
8
9			=head1 DESCRIPTION
10
11	root	1.14	This module implements asynchronous i/o using the means available to linux
12			- clone. It does not hook into the POSIX aio_* functions because linux
13			does not yet support these in the kernel (and even if, it would only allow
14			aio_read and write, not open and stat).
15
16			Instead, in this module a number of (non-posix) threads are started that
17			execute your read/writes and signal their completion. You don't need
18			thread support in your libc or perl, and the threads created by this
19			module will not be visible to the pthreads library.
20	root	1.3
21	root	1.17	NOTICE: the threads created by this module will automatically be killed
22			when the thread calling min_parallel exits. Make sure you only ever call
23			min_parallel from the same thread that loaded this module.
24
25	root	1.16	Although the module will work with threads, it is not reentrant, so use
26			appropriate locking yourself.
27
28	root	1.1	=over 4
29
30			=cut
31
32			package Linux::AIO;
33
34	root	1.2	use base 'Exporter';
35
36	root	1.1	BEGIN {
37	root	1.26	$VERSION = 1.6;
38	root	1.1
39	root	1.17	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink);
40	root	1.2	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs);
41
42	root	1.1	require XSLoader;
43			XSLoader::load Linux::AIO, $VERSION;
44			}
45
46	root	1.14	=item Linux::AIO::min_parallel $nthreads
47	root	1.1
48	root	1.16	Set the minimum number of AIO threads to C<$nthreads>. The default is
49			C<1>, which means a single asynchronous operation can be done at one time
50			(the number of outstanding operations, however, is unlimited).
51	root	1.1
52	root	1.24	It is recommended to keep the number of threads low, as some linux
53	root	1.14	kernel versions will scale negatively with the number of threads (higher
54			parallelity => MUCH higher latency).
55
56	root	1.24	=item Linux::AIO::max_parallel $nthreads
57
58			Sets the maximum number of AIO threads to C<$nthreads>. If more than
59			the specified number of threads are currently running, kill them. This
60			function blocks until the limit is reached.
61
62			This module automatically runs C<max_parallel 0> at program end, to ensure
63			that all threads are killed and that there are no outstanding requests.
64
65	root	1.2	=item $fileno = Linux::AIO::poll_fileno
66
67	root	1.14	Return the I<request result pipe filehandle>. This filehandle must be
68			polled for reading by some mechanism outside this module (e.g. Event
69			or select, see below). If the pipe becomes readable you have to call
70			C<poll_cb> to check the results.
71	root	1.2
72			=item Linux::AIO::poll_cb
73
74			Process all outstanding events on the result pipe. You have to call this
75	root	1.14	regularly. Returns the number of events processed. Returns immediately
76			when no events are outstanding.
77	root	1.2
78	root	1.3	You can use Event to multiplex, e.g.:
79
80	root	1.14	Event->io (fd => Linux::AIO::poll_fileno,
81			poll => 'r', async => 1,
82			cb => \&Linux::AIO::poll_cb );
83	root	1.3
84	root	1.24	=item Linux::AIO::poll_wait
85
86			Wait till the result filehandle becomes ready for reading (simply does a
87			select on the filehandle. This is useful if you want to synchronously wait
88			for some requests to finish).
89
90	root	1.2	=item Linux::AIO::nreqs
91
92			Returns the number of requests currently outstanding.
93	root	1.4
94	root	1.14	=item aio_open $pathname, $flags, $mode, $callback
95	root	1.10
96			Asynchronously open or create a file and call the callback with the
97	root	1.14	filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this
98			might change in the future).
99	root	1.10
100	root	1.14	=item aio_close $fh, $callback
101	root	1.10
102			Asynchronously close a file and call the callback with the result code.
103
104	root	1.14	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback
105	root	1.9
106	root	1.14	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback
107	root	1.4
108			Reads or writes C<length> bytes from the specified C<fh> and C<offset>
109			into the scalar given by C<data> and offset C<dataoffset> and calls the
110	root	1.14	callback without the actual number of bytes read (or C<undef> on error).
111	root	1.4
112	root	1.14	=item aio_stat $fh_or_path, $callback
113	root	1.4
114	root	1.14	=item aio_lstat $fh, $callback
115	root	1.5
116	root	1.14	Works like perl's C<stat> or C<lstat> in void context. The callback will
117			be called after the stat and the results will be available using C<stat _>
118			or C<-s _> etc...
119	root	1.5
120	root	1.10	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
121			error when stat'ing a large file, the results will be silently truncated
122			unless perl itself is compiled with large file support.
123	root	1.17
124			=item aio_unlink $pathname, $callback
125
126	root	1.18	Asynchronously unlink a file.
127	root	1.2
128	root	1.1	=cut
129	root	1.16
130			min_parallel 1;
131	root	1.2
132			END {
133			max_parallel 0;
134			}
135	root	1.1
136			1;
137
138			=back
139
140			=head1 BUGS
141
142	root	1.14	This module has been extensively tested in a large and very busy webserver
143			for many years now.
144	root	1.1
145	root	1.14	- aio_open gives a fd, but all other functions expect a perl filehandle.
146	root	1.6
147	root	1.1	=head1 SEE ALSO
148
149			L<Coro>.
150
151			=head1 AUTHOR
152
153	root	1.22	Marc Lehmann <schmorp@schmorp.de>
154	root	1.20	http://home.schmorp.de/
155	root	1.1
156			=cut
157