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Revision 1.5 by root, Sun Jul 10 21:04:24 2005 UTC vs.
Revision 1.34 by root, Thu Aug 18 16:32:10 2005 UTC

… …
3IO::AIO - Asynchronous Input/Output 3IO::AIO - Asynchronous Input/Output
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use IO::AIO; 7 use IO::AIO;
8
9 aio_open "/etc/passwd", O_RDONLY, 0, sub {
10 my ($fh) = @_;
11 ...
12 };
13
14 aio_unlink "/tmp/file", sub { };
15
16 aio_read $fh, 30000, 1024, $buffer, 0, sub {
17 $_[0] > 0 or die "read error: $!";
18 };
19
20 # Event
21 Event->io (fd => IO::AIO::poll_fileno,
22 poll => 'r',
23 cb => \&IO::AIO::poll_cb);
24
25 # Glib/Gtk2
26 add_watch Glib::IO IO::AIO::poll_fileno,
27 in => sub { IO::AIO::poll_cb; 1 };
28
29 # Tk
30 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31 readable => \&IO::AIO::poll_cb);
32
33 # Danga::Socket
34 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35 \&IO::AIO::poll_cb);
36
8 37
9=head1 DESCRIPTION 38=head1 DESCRIPTION
10 39
11This module implements asynchronous I/O using whatever means your 40This module implements asynchronous I/O using whatever means your
12operating system supports. 41operating system supports.
… …
19not well-supported (Linux doesn't allow them on normal files currently, 48not well-supported (Linux doesn't allow them on normal files currently,
20for example), and they would only support aio_read and aio_write, so the 49for example), and they would only support aio_read and aio_write, so the
21remaining functionality would have to be implemented using threads anyway. 50remaining functionality would have to be implemented using threads anyway.
22 51
23Although the module will work with in the presence of other threads, it is 52Although the module will work with in the presence of other threads, it is
24currently not reentrant, so use appropriate locking yourself. 53currently not reentrant, so use appropriate locking yourself, always call
54C<poll_cb> from within the same thread, or never call C<poll_cb> (or other
55C<aio_> functions) recursively.
25 56
26=cut 57=cut
27 58
28package IO::AIO; 59package IO::AIO;
29 60
61no warnings;
62
30use base 'Exporter'; 63use base 'Exporter';
31 64
32use Fcntl (); 65use Fcntl ();
33 66
34BEGIN { 67BEGIN {
35 $VERSION = 0.2; 68 $VERSION = 1.5;
36 69
37 @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink 70 @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink
38 aio_fsync aio_fdatasync aio_readahead); 71 aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead);
39 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); 72 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
40 73
41 require XSLoader; 74 require XSLoader;
42 XSLoader::load IO::AIO, $VERSION; 75 XSLoader::load IO::AIO, $VERSION;
43} 76}
… …
46 79
47=head2 AIO FUNCTIONS 80=head2 AIO FUNCTIONS
48 81
49All the C<aio_*> calls are more or less thin wrappers around the syscall 82All the C<aio_*> calls are more or less thin wrappers around the syscall
50with the same name (sans C<aio_>). The arguments are similar or identical, 83with the same name (sans C<aio_>). The arguments are similar or identical,
51and they all accept an additional C<$callback> argument which must be 84and they all accept an additional (and optional) C<$callback> argument
52a code reference. This code reference will get called with the syscall 85which must be a code reference. This code reference will get called with
53return code (e.g. most syscalls return C<-1> on error, unlike perl, which 86the syscall return code (e.g. most syscalls return C<-1> on error, unlike
54usually delivers "false") as it's sole argument when the given syscall has 87perl, which usually delivers "false") as it's sole argument when the given
55been executed asynchronously. 88syscall has been executed asynchronously.
56 89
57All functions that expect a filehandle will also accept a file descriptor. 90All functions expecting a filehandle keep a copy of the filehandle
91internally until the request has finished.
58 92
59The filenames you pass to these routines I<must> be absolute. The reason 93The pathnames you pass to these routines I<must> be absolute and
60is that at the time the request is being executed, the current working 94encoded in byte form. The reason for the former is that at the time the
61directory could have changed. Alternatively, you can make sure that you 95request is being executed, the current working directory could have
96changed. Alternatively, you can make sure that you never change the
62never change the current working directory. 97current working directory.
98
99To encode pathnames to byte form, either make sure you either: a)
100always pass in filenames you got from outside (command line, readdir
101etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
102your pathnames to the locale (or other) encoding in effect in the user
103environment, d) use Glib::filename_from_unicode on unicode filenames or e)
104use something else.
63 105
64=over 4 106=over 4
65 107
66=item aio_open $pathname, $flags, $mode, $callback 108=item aio_open $pathname, $flags, $mode, $callback
67 109
… …
69created filehandle for the file. 111created filehandle for the file.
70 112
71The pathname passed to C<aio_open> must be absolute. See API NOTES, above, 113The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
72for an explanation. 114for an explanation.
73 115
74The C<$mode> argument is a bitmask. See the C<Fcntl> module for a 116The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
75list. They are the same as used in C<sysopen>. 117list. They are the same as used by C<sysopen>.
118
119Likewise, C<$mode> specifies the mode of the newly created file, if it
120didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
121except that it is mandatory (i.e. use C<0> if you don't create new files,
122and C<0666> or C<0777> if you do).
76 123
77Example: 124Example:
78 125
79 aio_open "/etc/passwd", O_RDONLY, 0, sub { 126 aio_open "/etc/passwd", O_RDONLY, 0, sub {
80 if ($_[0]) { 127 if ($_[0]) {
… …
87 134
88=item aio_close $fh, $callback 135=item aio_close $fh, $callback
89 136
90Asynchronously close a file and call the callback with the result 137Asynchronously close a file and call the callback with the result
91code. I<WARNING:> although accepted, you should not pass in a perl 138code. I<WARNING:> although accepted, you should not pass in a perl
92filehandle here, as perl will likely close the file descriptor itself when 139filehandle here, as perl will likely close the file descriptor another
93the filehandle is destroyed. Normally, you can safely call perls C<close> 140time when the filehandle is destroyed. Normally, you can safely call perls
94or just let filehandles go out of scope. 141C<close> or just let filehandles go out of scope.
142
143This is supposed to be a bug in the API, so that might change. It's
144therefore best to avoid this function.
95 145
96=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback 146=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback
97 147
98=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback 148=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback
99 149
100Reads or writes C<length> bytes from the specified C<fh> and C<offset> 150Reads or writes C<length> bytes from the specified C<fh> and C<offset>
101into the scalar given by C<data> and offset C<dataoffset> and calls the 151into the scalar given by C<data> and offset C<dataoffset> and calls the
102callback without the actual number of bytes read (or -1 on error, just 152callback without the actual number of bytes read (or -1 on error, just
103like the syscall). 153like the syscall).
104 154
155The C<$data> scalar I<MUST NOT> be modified in any way while the request
156is outstanding. Modifying it can result in segfaults or WW3 (if the
157necessary/optional hardware is installed).
158
105Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at 159Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
106offset C<0> within the scalar: 160offset C<0> within the scalar:
107 161
108 aio_read $fh, 7, 15, $buffer, 0, sub { 162 aio_read $fh, 7, 15, $buffer, 0, sub {
109 $_[0] >= 0 or die "read error: $!"; 163 $_[0] > 0 or die "read error: $!";
110 print "read <$buffer>\n"; 164 print "read $_[0] bytes: <$buffer>\n";
111 }; 165 };
112 166
113=item aio_readahead $fh,$offset,$length, $callback 167=item aio_readahead $fh,$offset,$length, $callback
114 168
115Asynchronously reads the specified byte range into the page cache, using
116the C<readahead> syscall. If that syscall doesn't exist the status will be
117C<-1> and C<$!> is set to ENOSYS.
118
119readahead() populates the page cache with data from a file so that 169C<aio_readahead> populates the page cache with data from a file so that
120subsequent reads from that file will not block on disk I/O. The C<$offset> 170subsequent reads from that file will not block on disk I/O. The C<$offset>
121argument specifies the starting point from which data is to be read and 171argument specifies the starting point from which data is to be read and
122C<$length> specifies the number of bytes to be read. I/O is performed in 172C<$length> specifies the number of bytes to be read. I/O is performed in
123whole pages, so that offset is effectively rounded down to a page boundary 173whole pages, so that offset is effectively rounded down to a page boundary
124and bytes are read up to the next page boundary greater than or equal to 174and bytes are read up to the next page boundary greater than or equal to
125(off-set+length). aio_readahead() does not read beyond the end of the 175(off-set+length). C<aio_readahead> does not read beyond the end of the
126file. The current file offset of the file is left unchanged. 176file. The current file offset of the file is left unchanged.
177
178If that syscall doesn't exist (likely if your OS isn't Linux) it will be
179emulated by simply reading the data, which would have a similar effect.
127 180
128=item aio_stat $fh_or_path, $callback 181=item aio_stat $fh_or_path, $callback
129 182
130=item aio_lstat $fh, $callback 183=item aio_lstat $fh, $callback
131 184
… …
150=item aio_unlink $pathname, $callback 203=item aio_unlink $pathname, $callback
151 204
152Asynchronously unlink (delete) a file and call the callback with the 205Asynchronously unlink (delete) a file and call the callback with the
153result code. 206result code.
154 207
208=item aio_rmdir $pathname, $callback
209
210Asynchronously rmdir (delete) a directory and call the callback with the
211result code.
212
155=item aio_fsync $fh, $callback 213=item aio_fsync $fh, $callback
156 214
157Asynchronously call fsync on the given filehandle and call the callback 215Asynchronously call fsync on the given filehandle and call the callback
158with the fsync result code. 216with the fsync result code.
159 217
160=item aio_fdatasync $fh, $callback 218=item aio_fdatasync $fh, $callback
161 219
162Asynchronously call fdatasync on the given filehandle and call the 220Asynchronously call fdatasync on the given filehandle and call the
163callback with the fdatasync result code. 221callback with the fdatasync result code.
164 222
223If this call isn't available because your OS lacks it or it couldn't be
224detected, it will be emulated by calling C<fsync> instead.
225
165=back 226=back
166 227
167=head2 SUPPORT FUNCTIONS 228=head2 SUPPORT FUNCTIONS
168 229
169=over 4 230=over 4
170 231
171=item $fileno = IO::AIO::poll_fileno 232=item $fileno = IO::AIO::poll_fileno
172 233
173Return the I<request result pipe filehandle>. This filehandle must be 234Return the I<request result pipe file descriptor>. This filehandle must be
174polled for reading by some mechanism outside this module (e.g. Event 235polled for reading by some mechanism outside this module (e.g. Event or
175or select, see below). If the pipe becomes readable you have to call 236select, see below or the SYNOPSIS). If the pipe becomes readable you have
176C<poll_cb> to check the results. 237to call C<poll_cb> to check the results.
177 238
178See C<poll_cb> for an example. 239See C<poll_cb> for an example.
179 240
180=item IO::AIO::poll_cb 241=item IO::AIO::poll_cb
181 242
182Process all outstanding events on the result pipe. You have to call this 243Process all outstanding events on the result pipe. You have to call this
183regularly. Returns the number of events processed. Returns immediately 244regularly. Returns the number of events processed. Returns immediately
184when no events are outstanding. 245when no events are outstanding.
185 246
186You can use Event to multiplex, e.g.: 247Example: Install an Event watcher that automatically calls
248IO::AIO::poll_cb with high priority:
187 249
188 Event->io (fd => IO::AIO::poll_fileno, 250 Event->io (fd => IO::AIO::poll_fileno,
189 poll => 'r', async => 1, 251 poll => 'r', async => 1,
190 cb => \&IO::AIO::poll_cb); 252 cb => \&IO::AIO::poll_cb);
191 253
192=item IO::AIO::poll_wait 254=item IO::AIO::poll_wait
193 255
194Wait till the result filehandle becomes ready for reading (simply does a 256Wait till the result filehandle becomes ready for reading (simply does a
195select on the filehandle. This is useful if you want to synchronously wait 257C<select> on the filehandle. This is useful if you want to synchronously wait
196for some requests to finish). 258for some requests to finish).
197 259
198See C<nreqs> for an example. 260See C<nreqs> for an example.
199 261
200=item IO::AIO::nreqs 262=item IO::AIO::nreqs
201 263
202Returns the number of requests currently outstanding. 264Returns the number of requests currently outstanding (i.e. for which their
265callback has not been invoked yet).
203 266
204Example: wait till there are no outstanding requests anymore: 267Example: wait till there are no outstanding requests anymore:
205 268
206 IO::AIO::poll_wait, IO::AIO::poll_cb 269 IO::AIO::poll_wait, IO::AIO::poll_cb
207 while IO::AIO::nreqs; 270 while IO::AIO::nreqs;
208 271
272=item IO::AIO::flush
273
274Wait till all outstanding AIO requests have been handled.
275
276Strictly equivalent to:
277
278 IO::AIO::poll_wait, IO::AIO::poll_cb
279 while IO::AIO::nreqs;
280
281=item IO::AIO::poll
282
283Waits until some requests have been handled.
284
285Strictly equivalent to:
286
287 IO::AIO::poll_wait, IO::AIO::poll_cb
288 if IO::AIO::nreqs;
289
209=item IO::AIO::min_parallel $nthreads 290=item IO::AIO::min_parallel $nthreads
210 291
211Set the minimum number of AIO threads to C<$nthreads>. The default is 292Set the minimum number of AIO threads to C<$nthreads>. The current default
212C<1>, which means a single asynchronous operation can be done at one time 293is C<4>, which means four asynchronous operations can be done at one time
213(the number of outstanding operations, however, is unlimited). 294(the number of outstanding operations, however, is unlimited).
295
296IO::AIO starts threads only on demand, when an AIO request is queued and
297no free thread exists.
214 298
215It is recommended to keep the number of threads low, as some Linux 299It is recommended to keep the number of threads low, as some Linux
216kernel versions will scale negatively with the number of threads (higher 300kernel versions will scale negatively with the number of threads (higher
217parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 301parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
218threads should be fine. 302threads should be fine.
219 303
220Under normal circumstances you don't need to call this function, as this 304Under most circumstances you don't need to call this function, as the
221module automatically starts some threads (the exact number might change, 305module selects a default that is suitable for low to moderate load.
222and is currently 4).
223 306
224=item IO::AIO::max_parallel $nthreads 307=item IO::AIO::max_parallel $nthreads
225 308
226Sets the maximum number of AIO threads to C<$nthreads>. If more than 309Sets the maximum number of AIO threads to C<$nthreads>. If more than the
227the specified number of threads are currently running, kill them. This 310specified number of threads are currently running, this function kills
228function blocks until the limit is reached. 311them. This function blocks until the limit is reached.
312
313While C<$nthreads> are zero, aio requests get queued but not executed
314until the number of threads has been increased again.
229 315
230This module automatically runs C<max_parallel 0> at program end, to ensure 316This module automatically runs C<max_parallel 0> at program end, to ensure
231that all threads are killed and that there are no outstanding requests. 317that all threads are killed and that there are no outstanding requests.
232 318
233Under normal circumstances you don't need to call this function. 319Under normal circumstances you don't need to call this function.
… …
237Sets the maximum number of outstanding requests to C<$nreqs>. If you 323Sets the maximum number of outstanding requests to C<$nreqs>. If you
238try to queue up more than this number of requests, the caller will block until 324try to queue up more than this number of requests, the caller will block until
239some requests have been handled. 325some requests have been handled.
240 326
241The default is very large, so normally there is no practical limit. If you 327The default is very large, so normally there is no practical limit. If you
242queue up many requests in a loop it it often improves speed if you set 328queue up many requests in a loop it often improves speed if you set
243this to a relatively low number, such as C<100>. 329this to a relatively low number, such as C<100>.
244 330
245Under normal circumstances you don't need to call this function. 331Under normal circumstances you don't need to call this function.
246 332
247=back 333=back
… …
250 336
251# support function to convert a fd into a perl filehandle 337# support function to convert a fd into a perl filehandle
252sub _fd2fh { 338sub _fd2fh {
253 return undef if $_[0] < 0; 339 return undef if $_[0] < 0;
254 340
255 # try to be perl5.6-compatible 341 # try to generate nice filehandles
256 local *AIO_FH; 342 my $sym = "IO::AIO::fd#$_[0]";
257 open AIO_FH, "+<&=$_[0]" 343 local *$sym;
344
345 open *$sym, "+<&=$_[0]" # usually works under any unix
346 or open *$sym, "<&=$_[0]" # cygwin needs this
347 or open *$sym, ">&=$_[0]" # or this
258 or return undef; 348 or return undef;
259 349
260 *AIO_FH 350 *$sym
261} 351}
262 352
263min_parallel 4; 353min_parallel 4;
264 354
265END { 355END {
266 max_parallel 0; 356 max_parallel 0;
267} 357}
268 358
2691; 3591;
270 360
361=head2 FORK BEHAVIOUR
362
363Before the fork, IO::AIO enters a quiescent state where no requests
364can be added in other threads and no results will be processed. After
365the fork the parent simply leaves the quiescent state and continues
366request/result processing, while the child clears the request/result
367queue (so the requests started before the fork will only be handled in
368the parent). Threats will be started on demand until the limit ste in the
369parent process has been reached again.
370
271=head1 SEE ALSO 371=head1 SEE ALSO
272 372
273L<Coro>, L<Linux::AIO>. 373L<Coro>, L<Linux::AIO>.
274 374
275=head1 AUTHOR 375=head1 AUTHOR

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