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Revision 1.5 by root, Sun Jul 10 23:45:16 2005 UTC

1NAME 1NAME
2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6
7 aio_open "/etc/passwd", O_RDONLY, 0, sub {
8 my ($fh) = @_;
9 ...
10 };
11
12 aio_unlink "/tmp/file", sub { };
13
14 aio_read $fh, 30000, 1024, $buffer, 0, sub {
15 $_[0] > 0 or die "read error: $!";
16 };
17
18 # Event
19 Event->io (fd => IO::AIO::poll_fileno,
20 poll => 'r',
21 cb => \&IO::AIO::poll_cb);
22
23 # Glib/Gtk2
24 add_watch Glib::IO IO::AIO::poll_fileno,
25 \&IO::AIO::poll_cb;
26
27 # Tk
28 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
29 readable => \&IO::AIO::poll_cb);
6 30
7DESCRIPTION 31DESCRIPTION
8 This module implements asynchronous I/O using whatever means your 32 This module implements asynchronous I/O using whatever means your
9 operating system supports. 33 operating system supports.
10 34
… …
19 using threads anyway. 43 using threads anyway.
20 44
21 Although the module will work with in the presence of other threads, it 45 Although the module will work with in the presence of other threads, it
22 is currently not reentrant, so use appropriate locking yourself. 46 is currently not reentrant, so use appropriate locking yourself.
23 47
24 API NOTES 48FUNCTIONS
49 AIO FUNCTIONS
25 All the "aio_*" calls are more or less thin wrappers around the syscall 50 All the "aio_*" calls are more or less thin wrappers around the syscall
26 with the same name (sans "aio_"). The arguments are similar or 51 with the same name (sans "aio_"). The arguments are similar or
27 identical, and they all accept an additional $callback argument which 52 identical, and they all accept an additional $callback argument which
28 must be a code reference. This code reference will get called with the 53 must be a code reference. This code reference will get called with the
29 syscall return code (e.g. most syscalls return -1 on error, unlike perl, 54 syscall return code (e.g. most syscalls return -1 on error, unlike perl,
… …
35 60
36 The filenames you pass to these routines *must* be absolute. The reason 61 The filenames you pass to these routines *must* be absolute. The reason
37 is that at the time the request is being executed, the current working 62 is that at the time the request is being executed, the current working
38 directory could have changed. Alternatively, you can make sure that you 63 directory could have changed. Alternatively, you can make sure that you
39 never change the current working directory. 64 never change the current working directory.
40
41 IO::AIO::min_parallel $nthreads
42 Set the minimum number of AIO threads to $nthreads. The default is
43 1, which means a single asynchronous operation can be done at one
44 time (the number of outstanding operations, however, is unlimited).
45
46 It is recommended to keep the number of threads low, as some linux
47 kernel versions will scale negatively with the number of threads
48 (higher parallelity => MUCH higher latency).
49
50 Under normal circumstances you don't need to call this function, as
51 this module automatically starts a single async thread.
52
53 IO::AIO::max_parallel $nthreads
54 Sets the maximum number of AIO threads to $nthreads. If more than
55 the specified number of threads are currently running, kill them.
56 This function blocks until the limit is reached.
57
58 This module automatically runs "max_parallel 0" at program end, to
59 ensure that all threads are killed and that there are no outstanding
60 requests.
61
62 Under normal circumstances you don't need to call this function.
63
64 $fileno = IO::AIO::poll_fileno
65 Return the *request result pipe filehandle*. This filehandle must be
66 polled for reading by some mechanism outside this module (e.g. Event
67 or select, see below). If the pipe becomes readable you have to call
68 "poll_cb" to check the results.
69
70 See "poll_cb" for an example.
71
72 IO::AIO::poll_cb
73 Process all outstanding events on the result pipe. You have to call
74 this regularly. Returns the number of events processed. Returns
75 immediately when no events are outstanding.
76
77 You can use Event to multiplex, e.g.:
78
79 Event->io (fd => IO::AIO::poll_fileno,
80 poll => 'r', async => 1,
81 cb => \&IO::AIO::poll_cb);
82
83 IO::AIO::poll_wait
84 Wait till the result filehandle becomes ready for reading (simply
85 does a select on the filehandle. This is useful if you want to
86 synchronously wait for some requests to finish).
87
88 See "nreqs" for an example.
89
90 IO::AIO::nreqs
91 Returns the number of requests currently outstanding.
92
93 Example: wait till there are no outstanding requests anymore:
94
95 IO::AIO::poll_wait, IO::AIO::poll_cb
96 while IO::AIO::nreqs;
97 65
98 aio_open $pathname, $flags, $mode, $callback 66 aio_open $pathname, $flags, $mode, $callback
99 Asynchronously open or create a file and call the callback with a 67 Asynchronously open or create a file and call the callback with a
100 newly created filehandle for the file. 68 newly created filehandle for the file.
101 69
… …
132 100
133 Example: Read 15 bytes at offset 7 into scalar $buffer, strating at 101 Example: Read 15 bytes at offset 7 into scalar $buffer, strating at
134 offset 0 within the scalar: 102 offset 0 within the scalar:
135 103
136 aio_read $fh, 7, 15, $buffer, 0, sub { 104 aio_read $fh, 7, 15, $buffer, 0, sub {
137 $_[0] >= 0 or die "read error: $!"; 105 $_[0] > 0 or die "read error: $!";
138 print "read <$buffer>\n"; 106 print "read $_[0] bytes: <$buffer>\n";
139 }; 107 };
140 108
141 aio_readahead $fh,$offset,$length, $callback 109 aio_readahead $fh,$offset,$length, $callback
142 Asynchronously reads the specified byte range into the page cache, 110 Asynchronously reads the specified byte range into the page cache,
143 using the "readahead" syscall. If that syscall doesn't exist the 111 using the "readahead" syscall. If that syscall doesn't exist the
… …
184 152
185 aio_fdatasync $fh, $callback 153 aio_fdatasync $fh, $callback
186 Asynchronously call fdatasync on the given filehandle and call the 154 Asynchronously call fdatasync on the given filehandle and call the
187 callback with the fdatasync result code. 155 callback with the fdatasync result code.
188 156
189BUGS 157 SUPPORT FUNCTIONS
190 - could be optimized to use more semaphores instead of filehandles. 158 $fileno = IO::AIO::poll_fileno
159 Return the *request result pipe filehandle*. This filehandle must be
160 polled for reading by some mechanism outside this module (e.g. Event
161 or select, see below). If the pipe becomes readable you have to call
162 "poll_cb" to check the results.
163
164 See "poll_cb" for an example.
165
166 IO::AIO::poll_cb
167 Process all outstanding events on the result pipe. You have to call
168 this regularly. Returns the number of events processed. Returns
169 immediately when no events are outstanding.
170
171 You can use Event to multiplex, e.g.:
172
173 Event->io (fd => IO::AIO::poll_fileno,
174 poll => 'r', async => 1,
175 cb => \&IO::AIO::poll_cb);
176
177 IO::AIO::poll_wait
178 Wait till the result filehandle becomes ready for reading (simply
179 does a select on the filehandle. This is useful if you want to
180 synchronously wait for some requests to finish).
181
182 See "nreqs" for an example.
183
184 IO::AIO::nreqs
185 Returns the number of requests currently outstanding.
186
187 Example: wait till there are no outstanding requests anymore:
188
189 IO::AIO::poll_wait, IO::AIO::poll_cb
190 while IO::AIO::nreqs;
191
192 IO::AIO::min_parallel $nthreads
193 Set the minimum number of AIO threads to $nthreads. The default is
194 1, which means a single asynchronous operation can be done at one
195 time (the number of outstanding operations, however, is unlimited).
196
197 It is recommended to keep the number of threads low, as some Linux
198 kernel versions will scale negatively with the number of threads
199 (higher parallelity => MUCH higher latency). With current Linux 2.6
200 versions, 4-32 threads should be fine.
201
202 Under normal circumstances you don't need to call this function, as
203 this module automatically starts some threads (the exact number
204 might change, and is currently 4).
205
206 IO::AIO::max_parallel $nthreads
207 Sets the maximum number of AIO threads to $nthreads. If more than
208 the specified number of threads are currently running, kill them.
209 This function blocks until the limit is reached.
210
211 This module automatically runs "max_parallel 0" at program end, to
212 ensure that all threads are killed and that there are no outstanding
213 requests.
214
215 Under normal circumstances you don't need to call this function.
216
217 $oldnreqs = IO::AIO::max_outstanding $nreqs
218 Sets the maximum number of outstanding requests to $nreqs. If you
219 try to queue up more than this number of requests, the caller will
220 block until some requests have been handled.
221
222 The default is very large, so normally there is no practical limit.
223 If you queue up many requests in a loop it it often improves speed
224 if you set this to a relatively low number, such as 100.
225
226 Under normal circumstances you don't need to call this function.
191 227
192SEE ALSO 228SEE ALSO
193 Coro, Linux::AIO. 229 Coro, Linux::AIO.
194 230
195AUTHOR 231AUTHOR

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