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4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use IO::AIO; 7 use IO::AIO;
8 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
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. Currently, it falls back to Linux::AIO if that 41operating system supports.
13module is available, or uses pthreads to emulato aio functionality.
14 42
15Currently, in this module a number of threads are started that execute 43Currently, a number of threads are started that execute your read/writes
16your read/writes and signal their completion. You don't need thread 44and signal their completion. You don't need thread support in your libc or
17support in your libc or perl, and the threads created by this module will 45perl, and the threads created by this module will not be visible to the
18not be visible to the pthreads library. 46pthreads library. In the future, this module might make use of the native
47aio functions available on many operating systems. However, they are often
48not well-supported (Linux doesn't allow them on normal files currently,
49for example), and they would only support aio_read and aio_write, so the
50remaining functionality would have to be implemented using threads anyway.
19 51
20Although 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
21not reentrant, so use appropriate locking yourself. 53currently not reentrant, so use appropriate locking yourself.
22
23=head2 API NOTES
24
25All the C<aio_*> calls are more or less thin wrappers around the syscall
26with the same name (sans C<aio_>). The arguments are similar or identical,
27and they all accept an additional C<$callback> argument which must be
28a code reference. This code reference will get called with the syscall
29return code (e.g. most syscalls return C<-1> on error, unlike perl, which
30usually delivers "false") as it's sole argument when the given syscall has
31been executed asynchronously.
32
33All functions that expect a filehandle will also accept a file descriptor.
34
35The filenames you pass to these routines I<must> be absolute. The reason
36is that at the time the request is being executed, the current working
37directory could have changed. Alternatively, you can make sure that you
38never change the current working directory.
39
40=over 4
41 54
42=cut 55=cut
43 56
44package IO::AIO; 57package IO::AIO;
45 58
46use base 'Exporter'; 59use base 'Exporter';
47 60
61use Fcntl ();
62
48BEGIN { 63BEGIN {
49 $VERSION = 0.1; 64 $VERSION = 0.9;
50 65
51 @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
52 aio_fsync aio_fdatasync aio_readahead); 67 aio_fsync aio_fdatasync aio_readahead);
53 @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);
54 69
55 require XSLoader; 70 require XSLoader;
56 XSLoader::load IO::AIO, $VERSION; 71 XSLoader::load IO::AIO, $VERSION;
57} 72}
58 73
59=item IO::AIO::min_parallel $nthreads 74=head1 FUNCTIONS
60 75
61Set the minimum number of AIO threads to C<$nthreads>. The default is 76=head2 AIO FUNCTIONS
62C<1>, which means a single asynchronous operation can be done at one time
63(the number of outstanding operations, however, is unlimited).
64 77
65It 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
66kernel versions will scale negatively with the number of threads (higher 79with the same name (sans C<aio_>). The arguments are similar or identical,
67parallelity => 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.
68 85
69Under normal circumstances you don't need to call this function, as this 86All functions that expect a filehandle will also accept a file descriptor.
70module automatically starts a single async thread.
71 87
72=item IO::AIO::max_parallel $nthreads 88The filenames you pass to these routines I<must> be absolute. The reason
89for this is that at the time the request is being executed, the current
90working directory could have changed. Alternatively, you can make sure
91that you never change the current working directory.
73 92
74Sets the maximum number of AIO threads to C<$nthreads>. If more than 93=over 4
75the specified number of threads are currently running, kill them. This
76function blocks until the limit is reached.
77
78This module automatically runs C<max_parallel 0> at program end, to ensure
79that all threads are killed and that there are no outstanding requests.
80
81Under normal circumstances you don't need to call this function.
82
83=item $fileno = IO::AIO::poll_fileno
84
85Return the I<request result pipe filehandle>. This filehandle must be
86polled for reading by some mechanism outside this module (e.g. Event
87or select, see below). If the pipe becomes readable you have to call
88C<poll_cb> to check the results.
89
90See C<poll_cb> for an example.
91
92=item IO::AIO::poll_cb
93
94Process all outstanding events on the result pipe. You have to call this
95regularly. Returns the number of events processed. Returns immediately
96when no events are outstanding.
97
98You can use Event to multiplex, e.g.:
99
100 Event->io (fd => IO::AIO::poll_fileno,
101 poll => 'r', async => 1,
102 cb => \&IO::AIO::poll_cb);
103
104=item IO::AIO::poll_wait
105
106Wait till the result filehandle becomes ready for reading (simply does a
107select on the filehandle. This is useful if you want to synchronously wait
108for some requests to finish).
109
110See C<nreqs> for an example.
111
112=item IO::AIO::nreqs
113
114Returns the number of requests currently outstanding.
115
116Example: wait till there are no outstanding requests anymore:
117
118 IO::AIO::poll_wait, IO::AIO::poll_cb
119 while IO::AIO::nreqs;
120 94
121=item aio_open $pathname, $flags, $mode, $callback 95=item aio_open $pathname, $flags, $mode, $callback
122 96
123Asynchronously open or create a file and call the callback with the 97Asynchronously open or create a file and call the callback with a newly
124filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this 98created filehandle for the file.
125might change in the future).
126 99
127The pathname passed to C<aio_open> must be absolute. See API NOTES, above, 100The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
128for an explanation. 101for an explanation.
129 102
130The C<$mode> argument is a bitmask. See the C<Fcntl> module for a 103The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
131list. They are the same as used in C<sysopen>. 104list. They are the same as used by C<sysopen>.
105
106Likewise, C<$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).
132 110
133Example: 111Example:
134 112
135 aio_open "/etc/passwd", O_RDONLY, 0, sub { 113 aio_open "/etc/passwd", O_RDONLY, 0, sub {
136 if ($_[0] >= 0) { 114 if ($_[0]) {
137 open my $fh, "<&$_[0]"; # create a copy for perl
138 aio_close $_[0], sub { }; # close the aio handle
139 print "open successful, fh is $fh\n"; 115 print "open successful, fh is $_[0]\n";
140 ... 116 ...
141 } else { 117 } else {
142 die "open failed: $!\n"; 118 die "open failed: $!\n";
143 } 119 }
144 }; 120 };
145 121
146=item aio_close $fh, $callback 122=item aio_close $fh, $callback
147 123
148Asynchronously close a file and call the callback with the result code. 124Asynchronously close a file and call the callback with the result
125code. I<WARNING:> although accepted, you should not pass in a perl
126filehandle here, as perl will likely close the file descriptor another
127time when the filehandle is destroyed. Normally, you can safely call perls
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.
149 132
150=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback 133=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback
151 134
152=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback 135=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback
153 136
154Reads or writes C<length> bytes from the specified C<fh> and C<offset> 137Reads or writes C<length> bytes from the specified C<fh> and C<offset>
155into the scalar given by C<data> and offset C<dataoffset> and calls the 138into the scalar given by C<data> and offset C<dataoffset> and calls the
156callback without the actual number of bytes read (or -1 on error, just 139callback without the actual number of bytes read (or -1 on error, just
157like the syscall). 140like the syscall).
158 141
159Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at 142Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
160offset C<0> within the scalar: 143offset C<0> within the scalar:
161 144
162 aio_read $fh, 7, 15, $buffer, 0, sub { 145 aio_read $fh, 7, 15, $buffer, 0, sub {
163 $_[0] >= 0 or die "read error: $!"; 146 $_[0] > 0 or die "read error: $!";
164 print "read <$buffer>\n"; 147 print "read $_[0] bytes: <$buffer>\n";
165 }; 148 };
166 149
167=item aio_readahead $fh,$offset,$length, $callback 150=item aio_readahead $fh,$offset,$length, $callback
168 151
169Asynchronously reads the specified byte range into the page cache, using 152Asynchronously reads the specified byte range into the page cache, using
170the C<readahead> syscall. If that syscall doesn't exist the status will be 153the C<readahead> syscall. If that syscall doesn't exist (likely if your OS
171C<-1> and C<$!> is set to ENOSYS. 154isn't Linux) the status will be C<-1> and C<$!> is set to C<ENOSYS>.
172 155
173readahead() populates the page cache with data from a file so that 156C<aio_readahead> populates the page cache with data from a file so that
174subsequent reads from that file will not block on disk I/O. The C<$offset> 157subsequent reads from that file will not block on disk I/O. The C<$offset>
175argument specifies the starting point from which data is to be read and 158argument specifies the starting point from which data is to be read and
176C<$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
177whole 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
178and 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
179(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
180file. The current file offset of the file is left unchanged. 163file. The current file offset of the file is left unchanged.
181 164
182=item aio_stat $fh_or_path, $callback 165=item aio_stat $fh_or_path, $callback
183 166
184=item aio_lstat $fh, $callback 167=item aio_lstat $fh, $callback
… …
212with the fsync result code. 195with the fsync result code.
213 196
214=item aio_fdatasync $fh, $callback 197=item aio_fdatasync $fh, $callback
215 198
216Asynchronously call fdatasync on the given filehandle and call the 199Asynchronously call fdatasync on the given filehandle and call the
217callback with the fdatasync result code. 200callback with the fdatasync result code. Might set C<$!> 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
218 306
219=cut 307=cut
308
309# support function to convert a fd into a perl filehandle
310sub _fd2fh {
311 return undef if $_[0] < 0;
312
313 # try to be perl5.6-compatible
314 local *AIO_FH;
315 open AIO_FH, "+<&=$_[0]"
316 or return undef;
317
318 *AIO_FH
319}
220 320
221min_parallel 4; 321min_parallel 4;
222 322
223END { 323END {
224 max_parallel 0; 324 max_parallel 0;
225} 325}
226 326
2271; 3271;
228 328
229=back
230
231=head1 BUGS
232
233 - aio_open gives a fd, but all other functions expect a perl filehandle.
234
235=head1 SEE ALSO 329=head1 SEE ALSO
236 330
237L<Coro>, L<Linux::AIO>. 331L<Coro>, L<Linux::AIO>.
238 332
239=head1 AUTHOR 333=head1 AUTHOR

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