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Revision 1.3 by root, Sun Jul 10 20:07:11 2005 UTC vs.
Revision 1.20 by root, Tue Jul 12 11:29:40 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: $!";
18 };
19
20 # Event
21 Event->io (fd => IO::AIO::poll_fileno,
22 poll => 'r',
23 cb => \&IO::AIO::poll_cb);
24
25 # Glib/Gtk2
26 add_watch Glib::IO IO::AIO::poll_fileno,
27 in => sub { IO::AIO::poll_cb, 1 };
28
29 # Tk
30 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31 readable => \&IO::AIO::poll_cb);
32
33 # Danga::Socket
34 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35 \&IO::AIO::poll_cb);
36
8 37
9=head1 DESCRIPTION 38=head1 DESCRIPTION
10 39
11This module implements asynchronous I/O using whatever means your 40This module implements asynchronous I/O using whatever means your
12operating system supports. 41operating system supports.
… …
21remaining functionality would have to be implemented using threads anyway. 50remaining functionality would have to be implemented using threads anyway.
22 51
23Although the module will work with in the presence of other threads, it is 52Although the module will work with in the presence of other threads, it is
24currently not reentrant, so use appropriate locking yourself. 53currently not reentrant, so use appropriate locking yourself.
25 54
26=head2 API NOTES
27
28All the C<aio_*> calls are more or less thin wrappers around the syscall
29with the same name (sans C<aio_>). The arguments are similar or identical,
30and they all accept an additional C<$callback> argument which must be
31a code reference. This code reference will get called with the syscall
32return code (e.g. most syscalls return C<-1> on error, unlike perl, which
33usually delivers "false") as it's sole argument when the given syscall has
34been executed asynchronously.
35
36All functions that expect a filehandle will also accept a file descriptor.
37
38The filenames you pass to these routines I<must> be absolute. The reason
39is that at the time the request is being executed, the current working
40directory could have changed. Alternatively, you can make sure that you
41never change the current working directory.
42
43=over 4
44
45=cut 55=cut
46 56
47package IO::AIO; 57package IO::AIO;
48 58
49use base 'Exporter'; 59use base 'Exporter';
50 60
51use Fcntl (); 61use Fcntl ();
52 62
53BEGIN { 63BEGIN {
54 $VERSION = 0.2; 64 $VERSION = 0.5;
55 65
56 @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink 66 @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink
57 aio_fsync aio_fdatasync aio_readahead); 67 aio_fsync aio_fdatasync aio_readahead);
58 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs); 68 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
59 69
60 require XSLoader; 70 require XSLoader;
61 XSLoader::load IO::AIO, $VERSION; 71 XSLoader::load IO::AIO, $VERSION;
62} 72}
63 73
64=item IO::AIO::min_parallel $nthreads 74=head1 FUNCTIONS
65 75
66Set the minimum number of AIO threads to C<$nthreads>. The default is 76=head2 AIO FUNCTIONS
67C<1>, which means a single asynchronous operation can be done at one time
68(the number of outstanding operations, however, is unlimited).
69 77
70It is recommended to keep the number of threads low, as some linux 78All the C<aio_*> calls are more or less thin wrappers around the syscall
71kernel versions will scale negatively with the number of threads (higher 79with the same name (sans C<aio_>). The arguments are similar or identical,
72parallelity => MUCH higher latency). 80and they all accept an additional (and optional) C<$callback> argument
81which must be a code reference. This code reference will get called with
82the syscall return code (e.g. most syscalls return C<-1> on error, unlike
83perl, which usually delivers "false") as it's sole argument when the given
84syscall has been executed asynchronously.
73 85
74Under normal circumstances you don't need to call this function, as this 86All functions that expect a filehandle will also accept a file descriptor.
75module automatically starts a single async thread.
76 87
77=item IO::AIO::max_parallel $nthreads 88The filenames you pass to these routines I<must> be absolute. The reason
89for this is that at the time the request is being executed, the current
90working directory could have changed. Alternatively, you can make sure
91that you never change the current working directory.
78 92
79Sets the maximum number of AIO threads to C<$nthreads>. If more than 93=over 4
80the specified number of threads are currently running, kill them. This
81function blocks until the limit is reached.
82
83This module automatically runs C<max_parallel 0> at program end, to ensure
84that all threads are killed and that there are no outstanding requests.
85
86Under normal circumstances you don't need to call this function.
87
88=item $fileno = IO::AIO::poll_fileno
89
90Return the I<request result pipe filehandle>. This filehandle must be
91polled for reading by some mechanism outside this module (e.g. Event
92or select, see below). If the pipe becomes readable you have to call
93C<poll_cb> to check the results.
94
95See C<poll_cb> for an example.
96
97=item IO::AIO::poll_cb
98
99Process all outstanding events on the result pipe. You have to call this
100regularly. Returns the number of events processed. Returns immediately
101when no events are outstanding.
102
103You can use Event to multiplex, e.g.:
104
105 Event->io (fd => IO::AIO::poll_fileno,
106 poll => 'r', async => 1,
107 cb => \&IO::AIO::poll_cb);
108
109=item IO::AIO::poll_wait
110
111Wait till the result filehandle becomes ready for reading (simply does a
112select on the filehandle. This is useful if you want to synchronously wait
113for some requests to finish).
114
115See C<nreqs> for an example.
116
117=item IO::AIO::nreqs
118
119Returns the number of requests currently outstanding.
120
121Example: wait till there are no outstanding requests anymore:
122
123 IO::AIO::poll_wait, IO::AIO::poll_cb
124 while IO::AIO::nreqs;
125 94
126=item aio_open $pathname, $flags, $mode, $callback 95=item aio_open $pathname, $flags, $mode, $callback
127 96
128Asynchronously open or create a file and call the callback with a newly 97Asynchronously open or create a file and call the callback with a newly
129created filehandle for the file. 98created filehandle for the file.
130 99
131The pathname passed to C<aio_open> must be absolute. See API NOTES, above, 100The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
132for an explanation. 101for an explanation.
133 102
134The C<$mode> argument is a bitmask. See the C<Fcntl> module for a 103The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
135list. They are the same as used in C<sysopen>. 104list. They are the same as used by C<sysopen>.
105
106Likewise, C<$mode> specifies the mode of the newly created file, if it
107didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
108except that it is mandatory (i.e. use C<0> if you don't create new files,
109and C<0666> or C<0777> if you do).
136 110
137Example: 111Example:
138 112
139 aio_open "/etc/passwd", O_RDONLY, 0, sub { 113 aio_open "/etc/passwd", O_RDONLY, 0, sub {
140 if ($_[0]) { 114 if ($_[0]) {
… …
147 121
148=item aio_close $fh, $callback 122=item aio_close $fh, $callback
149 123
150Asynchronously close a file and call the callback with the result 124Asynchronously close a file and call the callback with the result
151code. I<WARNING:> although accepted, you should not pass in a perl 125code. I<WARNING:> although accepted, you should not pass in a perl
152filehandle here, as perl will likely close the file descriptor itself when 126filehandle here, as perl will likely close the file descriptor another
153the filehandle is destroyed. Normally, you can safely call perls C<close> 127time when the filehandle is destroyed. Normally, you can safely call perls
154or just let filehandles go out of scope. 128C<close> or just let filehandles go out of scope.
129
130This is supposed to be a bug in the API, so that might change. It's
131therefore best to avoid this function.
155 132
156=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback 133=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback
157 134
158=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback 135=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback
159 136
160Reads or writes C<length> bytes from the specified C<fh> and C<offset> 137Reads or writes C<length> bytes from the specified C<fh> and C<offset>
161into the scalar given by C<data> and offset C<dataoffset> and calls the 138into the scalar given by C<data> and offset C<dataoffset> and calls the
162callback without the actual number of bytes read (or -1 on error, just 139callback without the actual number of bytes read (or -1 on error, just
163like the syscall). 140like the syscall).
164 141
165Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at 142Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
166offset C<0> within the scalar: 143offset C<0> within the scalar:
167 144
168 aio_read $fh, 7, 15, $buffer, 0, sub { 145 aio_read $fh, 7, 15, $buffer, 0, sub {
169 $_[0] >= 0 or die "read error: $!"; 146 $_[0] > 0 or die "read error: $!";
170 print "read <$buffer>\n"; 147 print "read $_[0] bytes: <$buffer>\n";
171 }; 148 };
172 149
173=item aio_readahead $fh,$offset,$length, $callback 150=item aio_readahead $fh,$offset,$length, $callback
174 151
175Asynchronously reads the specified byte range into the page cache, using 152Asynchronously reads the specified byte range into the page cache, using
176the C<readahead> syscall. If that syscall doesn't exist the status will be 153the C<readahead> syscall. If that syscall doesn't exist (likely if your OS
177C<-1> and C<$!> is set to ENOSYS. 154isn't Linux) the status will be C<-1> and C<$!> is set to C<ENOSYS>.
178 155
179readahead() populates the page cache with data from a file so that 156C<aio_readahead> populates the page cache with data from a file so that
180subsequent reads from that file will not block on disk I/O. The C<$offset> 157subsequent reads from that file will not block on disk I/O. The C<$offset>
181argument specifies the starting point from which data is to be read and 158argument specifies the starting point from which data is to be read and
182C<$length> specifies the number of bytes to be read. I/O is performed in 159C<$length> specifies the number of bytes to be read. I/O is performed in
183whole pages, so that offset is effectively rounded down to a page boundary 160whole pages, so that offset is effectively rounded down to a page boundary
184and bytes are read up to the next page boundary greater than or equal to 161and bytes are read up to the next page boundary greater than or equal to
185(off-set+length). aio_readahead() does not read beyond the end of the 162(off-set+length). C<aio_readahead> does not read beyond the end of the
186file. The current file offset of the file is left unchanged. 163file. The current file offset of the file is left unchanged.
187 164
188=item aio_stat $fh_or_path, $callback 165=item aio_stat $fh_or_path, $callback
189 166
190=item aio_lstat $fh, $callback 167=item aio_lstat $fh, $callback
… …
218with the fsync result code. 195with the fsync result code.
219 196
220=item aio_fdatasync $fh, $callback 197=item aio_fdatasync $fh, $callback
221 198
222Asynchronously call fdatasync on the given filehandle and call the 199Asynchronously call fdatasync on the given filehandle and call the
223callback with the fdatasync result code. 200callback with the fdatasync result code. Might set C<$!> to C<ENOSYS> if
201C<fdatasync> is not available.
202
203=back
204
205=head2 SUPPORT FUNCTIONS
206
207=over 4
208
209=item $fileno = IO::AIO::poll_fileno
210
211Return the I<request result pipe file descriptor>. This filehandle must be
212polled for reading by some mechanism outside this module (e.g. Event or
213select, see below or the SYNOPSIS). If the pipe becomes readable you have
214to call C<poll_cb> to check the results.
215
216See C<poll_cb> for an example.
217
218=item IO::AIO::poll_cb
219
220Process all outstanding events on the result pipe. You have to call this
221regularly. Returns the number of events processed. Returns immediately
222when no events are outstanding.
223
224Example: Install an Event watcher that automatically calls
225IO::AIO::poll_cb with high priority:
226
227 Event->io (fd => IO::AIO::poll_fileno,
228 poll => 'r', async => 1,
229 cb => \&IO::AIO::poll_cb);
230
231=item IO::AIO::poll_wait
232
233Wait till the result filehandle becomes ready for reading (simply does a
234C<select> on the filehandle. This is useful if you want to synchronously wait
235for some requests to finish).
236
237See C<nreqs> for an example.
238
239=item IO::AIO::nreqs
240
241Returns the number of requests currently outstanding (i.e. for which their
242callback has not been invoked yet).
243
244Example: wait till there are no outstanding requests anymore:
245
246 IO::AIO::poll_wait, IO::AIO::poll_cb
247 while IO::AIO::nreqs;
248
249=item IO::AIO::flush
250
251Wait till all outstanding AIO requests have been handled.
252
253Strictly equivalent to:
254
255 IO::AIO::poll_wait, IO::AIO::poll_cb
256 while IO::AIO::nreqs;
257
258=item IO::AIO::poll
259
260Waits until some requests have been handled.
261
262Strictly equivalent to:
263
264 IO::AIO::poll_wait, IO::AIO::poll_cb
265 if IO::AIO::nreqs;
266
267=item IO::AIO::min_parallel $nthreads
268
269Set the minimum number of AIO threads to C<$nthreads>. The default is
270C<1>, which means a single asynchronous operation can be done at one time
271(the number of outstanding operations, however, is unlimited).
272
273It is recommended to keep the number of threads low, as some Linux
274kernel versions will scale negatively with the number of threads (higher
275parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
276threads should be fine.
277
278Under normal circumstances you don't need to call this function, as this
279module automatically starts some threads (the exact number might change,
280and is currently 4).
281
282=item IO::AIO::max_parallel $nthreads
283
284Sets the maximum number of AIO threads to C<$nthreads>. If more than
285the specified number of threads are currently running, kill them. This
286function blocks until the limit is reached.
287
288This module automatically runs C<max_parallel 0> at program end, to ensure
289that all threads are killed and that there are no outstanding requests.
290
291Under normal circumstances you don't need to call this function.
292
293=item $oldnreqs = IO::AIO::max_outstanding $nreqs
294
295Sets the maximum number of outstanding requests to C<$nreqs>. If you
296try to queue up more than this number of requests, the caller will block until
297some requests have been handled.
298
299The default is very large, so normally there is no practical limit. If you
300queue up many requests in a loop it it often improves speed if you set
301this to a relatively low number, such as C<100>.
302
303Under normal circumstances you don't need to call this function.
304
305=back
224 306
225=cut 307=cut
226 308
227# support function to convert a fd into a perl filehandle 309# support function to convert a fd into a perl filehandle
228sub _fd2fh { 310sub _fd2fh {
… …
242 max_parallel 0; 324 max_parallel 0;
243} 325}
244 326
2451; 3271;
246 328
247=back
248
249=head1 BUGS
250
251 - could be optimized to use more semaphores instead of filehandles.
252
253=head1 SEE ALSO 329=head1 SEE ALSO
254 330
255L<Coro>, L<Linux::AIO>. 331L<Coro>, L<Linux::AIO>.
256 332
257=head1 AUTHOR 333=head1 AUTHOR

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