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Revision 1.6 by root, Mon Jul 11 03:29:39 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 in => sub { IO::AIO::poll_cb, 1 };
26
27 # Tk
28 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
29 readable => \&IO::AIO::poll_cb);
30
31 # Danga::Socket
32 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
33 \&IO::AIO::poll_cb);
6 34
7DESCRIPTION 35DESCRIPTION
8 This module implements asynchronous I/O using whatever means your 36 This module implements asynchronous I/O using whatever means your
9 operating system supports. 37 operating system supports.
10 38
… …
19 using threads anyway. 47 using threads anyway.
20 48
21 Although the module will work with in the presence of other threads, it 49 Although the module will work with in the presence of other threads, it
22 is currently not reentrant, so use appropriate locking yourself. 50 is currently not reentrant, so use appropriate locking yourself.
23 51
24 API NOTES 52FUNCTIONS
53 AIO FUNCTIONS
25 All the "aio_*" calls are more or less thin wrappers around the syscall 54 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 55 with the same name (sans "aio_"). The arguments are similar or
27 identical, and they all accept an additional $callback argument which 56 identical, and they all accept an additional (and optional) $callback
28 must be a code reference. This code reference will get called with the 57 argument which must be a code reference. This code reference will get
29 syscall return code (e.g. most syscalls return -1 on error, unlike perl, 58 called with the syscall return code (e.g. most syscalls return -1 on
30 which usually delivers "false") as it's sole argument when the given 59 error, unlike perl, which usually delivers "false") as it's sole
31 syscall has been executed asynchronously. 60 argument when the given syscall has been executed asynchronously.
32 61
33 All functions that expect a filehandle will also accept a file 62 All functions that expect a filehandle will also accept a file
34 descriptor. 63 descriptor.
35 64
36 The filenames you pass to these routines *must* be absolute. The reason 65 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 66 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 67 directory could have changed. Alternatively, you can make sure that you
39 never change the current working directory. 68 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 69
98 aio_open $pathname, $flags, $mode, $callback 70 aio_open $pathname, $flags, $mode, $callback
99 Asynchronously open or create a file and call the callback with a 71 Asynchronously open or create a file and call the callback with a
100 newly created filehandle for the file. 72 newly created filehandle for the file.
101 73
… …
128 Reads or writes "length" bytes from the specified "fh" and "offset" 100 Reads or writes "length" bytes from the specified "fh" and "offset"
129 into the scalar given by "data" and offset "dataoffset" and calls 101 into the scalar given by "data" and offset "dataoffset" and calls
130 the callback without the actual number of bytes read (or -1 on 102 the callback without the actual number of bytes read (or -1 on
131 error, just like the syscall). 103 error, just like the syscall).
132 104
133 Example: Read 15 bytes at offset 7 into scalar $buffer, strating at 105 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
134 offset 0 within the scalar: 106 offset 0 within the scalar:
135 107
136 aio_read $fh, 7, 15, $buffer, 0, sub { 108 aio_read $fh, 7, 15, $buffer, 0, sub {
137 $_[0] >= 0 or die "read error: $!"; 109 $_[0] > 0 or die "read error: $!";
138 print "read <$buffer>\n"; 110 print "read $_[0] bytes: <$buffer>\n";
139 }; 111 };
140 112
141 aio_readahead $fh,$offset,$length, $callback 113 aio_readahead $fh,$offset,$length, $callback
142 Asynchronously reads the specified byte range into the page cache, 114 Asynchronously reads the specified byte range into the page cache,
143 using the "readahead" syscall. If that syscall doesn't exist the 115 using the "readahead" syscall. If that syscall doesn't exist (likely
144 status will be -1 and $! is set to ENOSYS. 116 if your OS isn't Linux) the status will be -1 and $! is set to
117 ENOSYS.
145 118
146 readahead() populates the page cache with data from a file so that 119 readahead() populates the page cache with data from a file so that
147 subsequent reads from that file will not block on disk I/O. The 120 subsequent reads from that file will not block on disk I/O. The
148 $offset argument specifies the starting point from which data is to 121 $offset argument specifies the starting point from which data is to
149 be read and $length specifies the number of bytes to be read. I/O is 122 be read and $length specifies the number of bytes to be read. I/O is
… …
184 157
185 aio_fdatasync $fh, $callback 158 aio_fdatasync $fh, $callback
186 Asynchronously call fdatasync on the given filehandle and call the 159 Asynchronously call fdatasync on the given filehandle and call the
187 callback with the fdatasync result code. 160 callback with the fdatasync result code.
188 161
189BUGS 162 SUPPORT FUNCTIONS
190 - could be optimized to use more semaphores instead of filehandles. 163 $fileno = IO::AIO::poll_fileno
164 Return the *request result pipe filehandle*. This filehandle must be
165 polled for reading by some mechanism outside this module (e.g. Event
166 or select, see below). If the pipe becomes readable you have to call
167 "poll_cb" to check the results.
168
169 See "poll_cb" for an example.
170
171 IO::AIO::poll_cb
172 Process all outstanding events on the result pipe. You have to call
173 this regularly. Returns the number of events processed. Returns
174 immediately when no events are outstanding.
175
176 You can use Event to multiplex, e.g.:
177
178 Event->io (fd => IO::AIO::poll_fileno,
179 poll => 'r', async => 1,
180 cb => \&IO::AIO::poll_cb);
181
182 IO::AIO::poll_wait
183 Wait till the result filehandle becomes ready for reading (simply
184 does a select on the filehandle. This is useful if you want to
185 synchronously wait for some requests to finish).
186
187 See "nreqs" for an example.
188
189 IO::AIO::nreqs
190 Returns the number of requests currently outstanding.
191
192 Example: wait till there are no outstanding requests anymore:
193
194 IO::AIO::poll_wait, IO::AIO::poll_cb
195 while IO::AIO::nreqs;
196
197 IO::AIO::flush
198 Wait till all outstanding AIO requests have been handled.
199
200 Strictly equivalent to:
201
202 IO::AIO::poll_wait, IO::AIO::poll_cb
203 while IO::AIO::nreqs;
204
205 IO::AIO::poll
206 Waits until some requests have been handled.
207
208 Strictly equivalent to:
209
210 IO::AIO::poll_wait, IO::AIO::poll_cb
211 if IO::AIO::nreqs;
212
213 IO::AIO::min_parallel $nthreads
214 Set the minimum number of AIO threads to $nthreads. The default is
215 1, which means a single asynchronous operation can be done at one
216 time (the number of outstanding operations, however, is unlimited).
217
218 It is recommended to keep the number of threads low, as some Linux
219 kernel versions will scale negatively with the number of threads
220 (higher parallelity => MUCH higher latency). With current Linux 2.6
221 versions, 4-32 threads should be fine.
222
223 Under normal circumstances you don't need to call this function, as
224 this module automatically starts some threads (the exact number
225 might change, and is currently 4).
226
227 IO::AIO::max_parallel $nthreads
228 Sets the maximum number of AIO threads to $nthreads. If more than
229 the specified number of threads are currently running, kill them.
230 This function blocks until the limit is reached.
231
232 This module automatically runs "max_parallel 0" at program end, to
233 ensure that all threads are killed and that there are no outstanding
234 requests.
235
236 Under normal circumstances you don't need to call this function.
237
238 $oldnreqs = IO::AIO::max_outstanding $nreqs
239 Sets the maximum number of outstanding requests to $nreqs. If you
240 try to queue up more than this number of requests, the caller will
241 block until some requests have been handled.
242
243 The default is very large, so normally there is no practical limit.
244 If you queue up many requests in a loop it it often improves speed
245 if you set this to a relatively low number, such as 100.
246
247 Under normal circumstances you don't need to call this function.
191 248
192SEE ALSO 249SEE ALSO
193 Coro, Linux::AIO. 250 Coro, Linux::AIO.
194 251
195AUTHOR 252AUTHOR

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