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Revision 1.38 by root, Sun Aug 28 10:51:33 2005 UTC vs.
Revision 1.92 by root, Wed Nov 8 01:57:42 2006 UTC

15 15
16 aio_read $fh, 30000, 1024, $buffer, 0, sub { 16 aio_read $fh, 30000, 1024, $buffer, 0, sub {
17 $_[0] > 0 or die "read error: $!"; 17 $_[0] > 0 or die "read error: $!";
18 }; 18 };
19 19
20 # Event 20 # version 2+ has request and group objects
21 use IO::AIO 2;
22
23 aioreq_pri 4; # give next request a very high priority
24 my $req = aio_unlink "/tmp/file", sub { };
25 $req->cancel; # cancel request if still in queue
26
27 my $grp = aio_group sub { print "all stats done\n" };
28 add $grp aio_stat "..." for ...;
29
30 # AnyEvent integration
31 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
32 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
33
34 # Event integration
21 Event->io (fd => IO::AIO::poll_fileno, 35 Event->io (fd => IO::AIO::poll_fileno,
22 poll => 'r', 36 poll => 'r',
23 cb => \&IO::AIO::poll_cb); 37 cb => \&IO::AIO::poll_cb);
24 38
25 # Glib/Gtk2 39 # Glib/Gtk2 integration
26 add_watch Glib::IO IO::AIO::poll_fileno, 40 add_watch Glib::IO IO::AIO::poll_fileno,
27 in => sub { IO::AIO::poll_cb; 1 }; 41 in => sub { IO::AIO::poll_cb; 1 };
28 42
29 # Tk 43 # Tk integration
30 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", 44 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31 readable => \&IO::AIO::poll_cb); 45 readable => \&IO::AIO::poll_cb);
32 46
33 # Danga::Socket 47 # Danga::Socket integration
34 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 48 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35 \&IO::AIO::poll_cb); 49 \&IO::AIO::poll_cb);
36 50
37
38=head1 DESCRIPTION 51=head1 DESCRIPTION
39 52
40This module implements asynchronous I/O using whatever means your 53This module implements asynchronous I/O using whatever means your
41operating system supports. 54operating system supports.
42 55
56Asynchronous means that operations that can normally block your program
57(e.g. reading from disk) will be done asynchronously: the operation
58will still block, but you can do something else in the meantime. This
59is extremely useful for programs that need to stay interactive even
60when doing heavy I/O (GUI programs, high performance network servers
61etc.), but can also be used to easily do operations in parallel that are
62normally done sequentially, e.g. stat'ing many files, which is much faster
63on a RAID volume or over NFS when you do a number of stat operations
64concurrently.
65
66While most of this works on all types of file descriptors (for example
67sockets), using these functions on file descriptors that support
68nonblocking operation (again, sockets, pipes etc.) is very inefficient or
69might not work (aio_read fails on sockets/pipes/fifos). Use an event loop
70for that (such as the L<Event|Event> module): IO::AIO will naturally fit
71into such an event loop itself.
72
43Currently, a number of threads are started that execute your read/writes 73In this version, a number of threads are started that execute your
44and signal their completion. You don't need thread support in your libc or 74requests and signal their completion. You don't need thread support
45perl, and the threads created by this module will not be visible to the 75in perl, and the threads created by this module will not be visible
46pthreads library. In the future, this module might make use of the native 76to perl. In the future, this module might make use of the native aio
47aio functions available on many operating systems. However, they are often 77functions available on many operating systems. However, they are often
48not well-supported (Linux doesn't allow them on normal files currently, 78not well-supported or restricted (GNU/Linux doesn't allow them on normal
49for example), and they would only support aio_read and aio_write, so the 79files currently, for example), and they would only support aio_read and
50remaining functionality would have to be implemented using threads anyway. 80aio_write, so the remaining functionality would have to be implemented
81using threads anyway.
51 82
52Although the module will work with in the presence of other threads, it is 83Although the module will work with in the presence of other (Perl-)
53currently not reentrant, so use appropriate locking yourself, always call 84threads, it is currently not reentrant in any way, so use appropriate
54C<poll_cb> from within the same thread, or never call C<poll_cb> (or other 85locking yourself, always call C<poll_cb> from within the same thread, or
55C<aio_> functions) recursively. 86never call C<poll_cb> (or other C<aio_> functions) recursively.
87
88=head2 EXAMPLE
89
90This is a simple example that uses the Event module and loads
91F</etc/passwd> asynchronously:
92
93 use Fcntl;
94 use Event;
95 use IO::AIO;
96
97 # register the IO::AIO callback with Event
98 Event->io (fd => IO::AIO::poll_fileno,
99 poll => 'r',
100 cb => \&IO::AIO::poll_cb);
101
102 # queue the request to open /etc/passwd
103 aio_open "/etc/passwd", O_RDONLY, 0, sub {
104 my $fh = $_[0]
105 or die "error while opening: $!";
106
107 # stat'ing filehandles is generally non-blocking
108 my $size = -s $fh;
109
110 # queue a request to read the file
111 my $contents;
112 aio_read $fh, 0, $size, $contents, 0, sub {
113 $_[0] == $size
114 or die "short read: $!";
115
116 close $fh;
117
118 # file contents now in $contents
119 print $contents;
120
121 # exit event loop and program
122 Event::unloop;
123 };
124 };
125
126 # possibly queue up other requests, or open GUI windows,
127 # check for sockets etc. etc.
128
129 # process events as long as there are some:
130 Event::loop;
131
132=head1 REQUEST ANATOMY AND LIFETIME
133
134Every C<aio_*> function creates a request. which is a C data structure not
135directly visible to Perl.
136
137If called in non-void context, every request function returns a Perl
138object representing the request. In void context, nothing is returned,
139which saves a bit of memory.
140
141The perl object is a fairly standard ref-to-hash object. The hash contents
142are not used by IO::AIO so you are free to store anything you like in it.
143
144During their existance, aio requests travel through the following states,
145in order:
146
147=over 4
148
149=item ready
150
151Immediately after a request is created it is put into the ready state,
152waiting for a thread to execute it.
153
154=item execute
155
156A thread has accepted the request for processing and is currently
157executing it (e.g. blocking in read).
158
159=item pending
160
161The request has been executed and is waiting for result processing.
162
163While request submission and execution is fully asynchronous, result
164processing is not and relies on the perl interpreter calling C<poll_cb>
165(or another function with the same effect).
166
167=item result
168
169The request results are processed synchronously by C<poll_cb>.
170
171The C<poll_cb> function will process all outstanding aio requests by
172calling their callbacks, freeing memory associated with them and managing
173any groups they are contained in.
174
175=item done
176
177Request has reached the end of its lifetime and holds no resources anymore
178(except possibly for the Perl object, but its connection to the actual
179aio request is severed and calling its methods will either do nothing or
180result in a runtime error).
181
182=back
56 183
57=cut 184=cut
58 185
59package IO::AIO; 186package IO::AIO;
60 187
61no warnings; 188no warnings;
189use strict 'vars';
62 190
63use base 'Exporter'; 191use base 'Exporter';
64 192
65use Fcntl ();
66
67BEGIN { 193BEGIN {
68 $VERSION = 1.6; 194 our $VERSION = '2.2';
69 195
70 @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close stat 196 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71 aio_aio_lstat aio_unlink aio_rmdir aio_readdir aio_symlink 197 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72 aio_fsync aio_fdatasync aio_readahead); 198 aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
73 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel 199 aio_move aio_copy aio_group aio_nop aio_mknod);
74 max_outstanding nreqs); 200 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
201 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
202 min_parallel max_parallel max_idle
203 nreqs nready npending nthreads
204 max_poll_time max_poll_reqs);
205
206 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
75 207
76 require XSLoader; 208 require XSLoader;
77 XSLoader::load IO::AIO, $VERSION; 209 XSLoader::load ("IO::AIO", $VERSION);
78} 210}
79 211
80=head1 FUNCTIONS 212=head1 FUNCTIONS
81 213
82=head2 AIO FUNCTIONS 214=head2 AIO REQUEST FUNCTIONS
83 215
84All the C<aio_*> calls are more or less thin wrappers around the syscall 216All the C<aio_*> calls are more or less thin wrappers around the syscall
85with the same name (sans C<aio_>). The arguments are similar or identical, 217with the same name (sans C<aio_>). The arguments are similar or identical,
86and they all accept an additional (and optional) C<$callback> argument 218and they all accept an additional (and optional) C<$callback> argument
87which must be a code reference. This code reference will get called with 219which must be a code reference. This code reference will get called with
90syscall has been executed asynchronously. 222syscall has been executed asynchronously.
91 223
92All functions expecting a filehandle keep a copy of the filehandle 224All functions expecting a filehandle keep a copy of the filehandle
93internally until the request has finished. 225internally until the request has finished.
94 226
227All functions return request objects of type L<IO::AIO::REQ> that allow
228further manipulation of those requests while they are in-flight.
229
95The pathnames you pass to these routines I<must> be absolute and 230The pathnames you pass to these routines I<must> be absolute and
96encoded in byte form. The reason for the former is that at the time the 231encoded as octets. The reason for the former is that at the time the
97request is being executed, the current working directory could have 232request is being executed, the current working directory could have
98changed. Alternatively, you can make sure that you never change the 233changed. Alternatively, you can make sure that you never change the
99current working directory. 234current working directory anywhere in the program and then use relative
235paths.
100 236
101To encode pathnames to byte form, either make sure you either: a) 237To encode pathnames as octets, either make sure you either: a) always pass
102always pass in filenames you got from outside (command line, readdir 238in filenames you got from outside (command line, readdir etc.) without
103etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode 239tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
104your pathnames to the locale (or other) encoding in effect in the user 240your pathnames to the locale (or other) encoding in effect in the user
105environment, d) use Glib::filename_from_unicode on unicode filenames or e) 241environment, d) use Glib::filename_from_unicode on unicode filenames or e)
106use something else. 242use something else to ensure your scalar has the correct contents.
243
244This works, btw. independent of the internal UTF-8 bit, which IO::AIO
245handles correctly wether it is set or not.
107 246
108=over 4 247=over 4
109 248
249=item $prev_pri = aioreq_pri [$pri]
250
251Returns the priority value that would be used for the next request and, if
252C<$pri> is given, sets the priority for the next aio request.
253
254The default priority is C<0>, the minimum and maximum priorities are C<-4>
255and C<4>, respectively. Requests with higher priority will be serviced
256first.
257
258The priority will be reset to C<0> after each call to one of the C<aio_*>
259functions.
260
261Example: open a file with low priority, then read something from it with
262higher priority so the read request is serviced before other low priority
263open requests (potentially spamming the cache):
264
265 aioreq_pri -3;
266 aio_open ..., sub {
267 return unless $_[0];
268
269 aioreq_pri -2;
270 aio_read $_[0], ..., sub {
271 ...
272 };
273 };
274
275=item aioreq_nice $pri_adjust
276
277Similar to C<aioreq_pri>, but subtracts the given value from the current
278priority, so the effect is cumulative.
279
110=item aio_open $pathname, $flags, $mode, $callback 280=item aio_open $pathname, $flags, $mode, $callback->($fh)
111 281
112Asynchronously open or create a file and call the callback with a newly 282Asynchronously open or create a file and call the callback with a newly
113created filehandle for the file. 283created filehandle for the file.
114 284
115The pathname passed to C<aio_open> must be absolute. See API NOTES, above, 285The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
132 } else { 302 } else {
133 die "open failed: $!\n"; 303 die "open failed: $!\n";
134 } 304 }
135 }; 305 };
136 306
137=item aio_close $fh, $callback 307=item aio_close $fh, $callback->($status)
138 308
139Asynchronously close a file and call the callback with the result 309Asynchronously close a file and call the callback with the result
140code. I<WARNING:> although accepted, you should not pass in a perl 310code. I<WARNING:> although accepted, you should not pass in a perl
141filehandle here, as perl will likely close the file descriptor another 311filehandle here, as perl will likely close the file descriptor another
142time when the filehandle is destroyed. Normally, you can safely call perls 312time when the filehandle is destroyed. Normally, you can safely call perls
143C<close> or just let filehandles go out of scope. 313C<close> or just let filehandles go out of scope.
144 314
145This is supposed to be a bug in the API, so that might change. It's 315This is supposed to be a bug in the API, so that might change. It's
146therefore best to avoid this function. 316therefore best to avoid this function.
147 317
148=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback 318=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149 319
150=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback 320=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
151 321
152Reads or writes C<length> bytes from the specified C<fh> and C<offset> 322Reads or writes C<length> bytes from the specified C<fh> and C<offset>
153into the scalar given by C<data> and offset C<dataoffset> and calls the 323into the scalar given by C<data> and offset C<dataoffset> and calls the
154callback without the actual number of bytes read (or -1 on error, just 324callback without the actual number of bytes read (or -1 on error, just
155like the syscall). 325like the syscall).
164 aio_read $fh, 7, 15, $buffer, 0, sub { 334 aio_read $fh, 7, 15, $buffer, 0, sub {
165 $_[0] > 0 or die "read error: $!"; 335 $_[0] > 0 or die "read error: $!";
166 print "read $_[0] bytes: <$buffer>\n"; 336 print "read $_[0] bytes: <$buffer>\n";
167 }; 337 };
168 338
169=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback 339=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
170 340
171Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts 341Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
172reading at byte offset C<$in_offset>, and starts writing at the current 342reading at byte offset C<$in_offset>, and starts writing at the current
173file offset of C<$out_fh>. Because of that, it is not safe to issue more 343file offset of C<$out_fh>. Because of that, it is not safe to issue more
174than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each 344than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
187bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only 357bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
188provides the number of bytes written to C<$out_fh>. Only if the result 358provides the number of bytes written to C<$out_fh>. Only if the result
189value equals C<$length> one can assume that C<$length> bytes have been 359value equals C<$length> one can assume that C<$length> bytes have been
190read. 360read.
191 361
192=item aio_readahead $fh,$offset,$length, $callback 362=item aio_readahead $fh,$offset,$length, $callback->($retval)
193 363
194C<aio_readahead> populates the page cache with data from a file so that 364C<aio_readahead> populates the page cache with data from a file so that
195subsequent reads from that file will not block on disk I/O. The C<$offset> 365subsequent reads from that file will not block on disk I/O. The C<$offset>
196argument specifies the starting point from which data is to be read and 366argument specifies the starting point from which data is to be read and
197C<$length> specifies the number of bytes to be read. I/O is performed in 367C<$length> specifies the number of bytes to be read. I/O is performed in
201file. The current file offset of the file is left unchanged. 371file. The current file offset of the file is left unchanged.
202 372
203If that syscall doesn't exist (likely if your OS isn't Linux) it will be 373If that syscall doesn't exist (likely if your OS isn't Linux) it will be
204emulated by simply reading the data, which would have a similar effect. 374emulated by simply reading the data, which would have a similar effect.
205 375
206=item aio_stat $fh_or_path, $callback 376=item aio_stat $fh_or_path, $callback->($status)
207 377
208=item aio_lstat $fh, $callback 378=item aio_lstat $fh, $callback->($status)
209 379
210Works like perl's C<stat> or C<lstat> in void context. The callback will 380Works like perl's C<stat> or C<lstat> in void context. The callback will
211be called after the stat and the results will be available using C<stat _> 381be called after the stat and the results will be available using C<stat _>
212or C<-s _> etc... 382or C<-s _> etc...
213 383
223 aio_stat "/etc/passwd", sub { 393 aio_stat "/etc/passwd", sub {
224 $_[0] and die "stat failed: $!"; 394 $_[0] and die "stat failed: $!";
225 print "size is ", -s _, "\n"; 395 print "size is ", -s _, "\n";
226 }; 396 };
227 397
228=item aio_unlink $pathname, $callback 398=item aio_unlink $pathname, $callback->($status)
229 399
230Asynchronously unlink (delete) a file and call the callback with the 400Asynchronously unlink (delete) a file and call the callback with the
231result code. 401result code.
232 402
403=item aio_mknod $path, $mode, $dev, $callback->($status)
404
405[EXPERIMENTAL]
406
407Asynchronously create a device node (or fifo). See mknod(2).
408
409The only (POSIX-) portable way of calling this function is:
410
411 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
412
413=item aio_link $srcpath, $dstpath, $callback->($status)
414
415Asynchronously create a new link to the existing object at C<$srcpath> at
416the path C<$dstpath> and call the callback with the result code.
417
418=item aio_symlink $srcpath, $dstpath, $callback->($status)
419
420Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
421the path C<$dstpath> and call the callback with the result code.
422
423=item aio_readlink $path, $callback->($link)
424
425Asynchronously read the symlink specified by C<$path> and pass it to
426the callback. If an error occurs, nothing or undef gets passed to the
427callback.
428
429=item aio_rename $srcpath, $dstpath, $callback->($status)
430
431Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
432rename(2) and call the callback with the result code.
433
233=item aio_rmdir $pathname, $callback 434=item aio_rmdir $pathname, $callback->($status)
234 435
235Asynchronously rmdir (delete) a directory and call the callback with the 436Asynchronously rmdir (delete) a directory and call the callback with the
236result code. 437result code.
237 438
238=item aio_readdir $pathname $callback 439=item aio_readdir $pathname, $callback->($entries)
239 440
240Unlike the POSIX call of the same name, C<aio_readdir> reads an entire 441Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
241directory (i.e. opendir + readdir + closedir). The entries will not be 442directory (i.e. opendir + readdir + closedir). The entries will not be
242sorted, and will B<NOT> include the C<.> and C<..> entries. 443sorted, and will B<NOT> include the C<.> and C<..> entries.
243 444
244The callback a single argument which is either C<undef> or an array-ref 445The callback a single argument which is either C<undef> or an array-ref
245with the filenames. 446with the filenames.
246 447
448=item aio_copy $srcpath, $dstpath, $callback->($status)
449
450Try to copy the I<file> (directories not supported as either source or
451destination) from C<$srcpath> to C<$dstpath> and call the callback with
452the C<0> (error) or C<-1> ok.
453
454This is a composite request that it creates the destination file with
455mode 0200 and copies the contents of the source file into it using
456C<aio_sendfile>, followed by restoring atime, mtime, access mode and
457uid/gid, in that order.
458
459If an error occurs, the partial destination file will be unlinked, if
460possible, except when setting atime, mtime, access mode and uid/gid, where
461errors are being ignored.
462
463=cut
464
465sub aio_copy($$;$) {
466 my ($src, $dst, $cb) = @_;
467
468 my $pri = aioreq_pri;
469 my $grp = aio_group $cb;
470
471 aioreq_pri $pri;
472 add $grp aio_open $src, O_RDONLY, 0, sub {
473 if (my $src_fh = $_[0]) {
474 my @stat = stat $src_fh;
475
476 aioreq_pri $pri;
477 add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
478 if (my $dst_fh = $_[0]) {
479 aioreq_pri $pri;
480 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
481 if ($_[0] == $stat[7]) {
482 $grp->result (0);
483 close $src_fh;
484
485 # those should not normally block. should. should.
486 utime $stat[8], $stat[9], $dst;
487 chmod $stat[2] & 07777, $dst_fh;
488 chown $stat[4], $stat[5], $dst_fh;
489 close $dst_fh;
490 } else {
491 $grp->result (-1);
492 close $src_fh;
493 close $dst_fh;
494
495 aioreq $pri;
496 add $grp aio_unlink $dst;
497 }
498 };
499 } else {
500 $grp->result (-1);
501 }
502 },
503
504 } else {
505 $grp->result (-1);
506 }
507 };
508
509 $grp
510}
511
512=item aio_move $srcpath, $dstpath, $callback->($status)
513
514Try to move the I<file> (directories not supported as either source or
515destination) from C<$srcpath> to C<$dstpath> and call the callback with
516the C<0> (error) or C<-1> ok.
517
518This is a composite request that tries to rename(2) the file first. If
519rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
520that is successful, unlinking the C<$srcpath>.
521
522=cut
523
524sub aio_move($$;$) {
525 my ($src, $dst, $cb) = @_;
526
527 my $pri = aioreq_pri;
528 my $grp = aio_group $cb;
529
530 aioreq_pri $pri;
531 add $grp aio_rename $src, $dst, sub {
532 if ($_[0] && $! == EXDEV) {
533 aioreq_pri $pri;
534 add $grp aio_copy $src, $dst, sub {
535 $grp->result ($_[0]);
536
537 if (!$_[0]) {
538 aioreq_pri $pri;
539 add $grp aio_unlink $src;
540 }
541 };
542 } else {
543 $grp->result ($_[0]);
544 }
545 };
546
547 $grp
548}
549
550=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
551
552Scans a directory (similar to C<aio_readdir>) but additionally tries to
553efficiently separate the entries of directory C<$path> into two sets of
554names, directories you can recurse into (directories), and ones you cannot
555recurse into (everything else, including symlinks to directories).
556
557C<aio_scandir> is a composite request that creates of many sub requests_
558C<$maxreq> specifies the maximum number of outstanding aio requests that
559this function generates. If it is C<< <= 0 >>, then a suitable default
560will be chosen (currently 4).
561
562On error, the callback is called without arguments, otherwise it receives
563two array-refs with path-relative entry names.
564
565Example:
566
567 aio_scandir $dir, 0, sub {
568 my ($dirs, $nondirs) = @_;
569 print "real directories: @$dirs\n";
570 print "everything else: @$nondirs\n";
571 };
572
573Implementation notes.
574
575The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
576
577After reading the directory, the modification time, size etc. of the
578directory before and after the readdir is checked, and if they match (and
579isn't the current time), the link count will be used to decide how many
580entries are directories (if >= 2). Otherwise, no knowledge of the number
581of subdirectories will be assumed.
582
583Then entries will be sorted into likely directories (everything without
584a non-initial dot currently) and likely non-directories (everything
585else). Then every entry plus an appended C</.> will be C<stat>'ed,
586likely directories first. If that succeeds, it assumes that the entry
587is a directory or a symlink to directory (which will be checked
588seperately). This is often faster than stat'ing the entry itself because
589filesystems might detect the type of the entry without reading the inode
590data (e.g. ext2fs filetype feature).
591
592If the known number of directories (link count - 2) has been reached, the
593rest of the entries is assumed to be non-directories.
594
595This only works with certainty on POSIX (= UNIX) filesystems, which
596fortunately are the vast majority of filesystems around.
597
598It will also likely work on non-POSIX filesystems with reduced efficiency
599as those tend to return 0 or 1 as link counts, which disables the
600directory counting heuristic.
601
602=cut
603
604sub aio_scandir($$$) {
605 my ($path, $maxreq, $cb) = @_;
606
607 my $pri = aioreq_pri;
608
609 my $grp = aio_group $cb;
610
611 $maxreq = 4 if $maxreq <= 0;
612
613 # stat once
614 aioreq_pri $pri;
615 add $grp aio_stat $path, sub {
616 return $grp->result () if $_[0];
617 my $now = time;
618 my $hash1 = join ":", (stat _)[0,1,3,7,9];
619
620 # read the directory entries
621 aioreq_pri $pri;
622 add $grp aio_readdir $path, sub {
623 my $entries = shift
624 or return $grp->result ();
625
626 # stat the dir another time
627 aioreq_pri $pri;
628 add $grp aio_stat $path, sub {
629 my $hash2 = join ":", (stat _)[0,1,3,7,9];
630
631 my $ndirs;
632
633 # take the slow route if anything looks fishy
634 if ($hash1 ne $hash2 or (stat _)[9] == $now) {
635 $ndirs = -1;
636 } else {
637 # if nlink == 2, we are finished
638 # on non-posix-fs's, we rely on nlink < 2
639 $ndirs = (stat _)[3] - 2
640 or return $grp->result ([], $entries);
641 }
642
643 # sort into likely dirs and likely nondirs
644 # dirs == files without ".", short entries first
645 $entries = [map $_->[0],
646 sort { $b->[1] cmp $a->[1] }
647 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
648 @$entries];
649
650 my (@dirs, @nondirs);
651
652 my $statgrp = add $grp aio_group sub {
653 $grp->result (\@dirs, \@nondirs);
654 };
655
656 limit $statgrp $maxreq;
657 feed $statgrp sub {
658 return unless @$entries;
659 my $entry = pop @$entries;
660
661 aioreq_pri $pri;
662 add $statgrp aio_stat "$path/$entry/.", sub {
663 if ($_[0] < 0) {
664 push @nondirs, $entry;
665 } else {
666 # need to check for real directory
667 aioreq_pri $pri;
668 add $statgrp aio_lstat "$path/$entry", sub {
669 if (-d _) {
670 push @dirs, $entry;
671
672 unless (--$ndirs) {
673 push @nondirs, @$entries;
674 feed $statgrp;
675 }
676 } else {
677 push @nondirs, $entry;
678 }
679 }
680 }
681 };
682 };
683 };
684 };
685 };
686
687 $grp
688}
689
247=item aio_fsync $fh, $callback 690=item aio_fsync $fh, $callback->($status)
248 691
249Asynchronously call fsync on the given filehandle and call the callback 692Asynchronously call fsync on the given filehandle and call the callback
250with the fsync result code. 693with the fsync result code.
251 694
252=item aio_fdatasync $fh, $callback 695=item aio_fdatasync $fh, $callback->($status)
253 696
254Asynchronously call fdatasync on the given filehandle and call the 697Asynchronously call fdatasync on the given filehandle and call the
255callback with the fdatasync result code. 698callback with the fdatasync result code.
256 699
257If this call isn't available because your OS lacks it or it couldn't be 700If this call isn't available because your OS lacks it or it couldn't be
258detected, it will be emulated by calling C<fsync> instead. 701detected, it will be emulated by calling C<fsync> instead.
259 702
703=item aio_group $callback->(...)
704
705This is a very special aio request: Instead of doing something, it is a
706container for other aio requests, which is useful if you want to bundle
707many requests into a single, composite, request with a definite callback
708and the ability to cancel the whole request with its subrequests.
709
710Returns an object of class L<IO::AIO::GRP>. See its documentation below
711for more info.
712
713Example:
714
715 my $grp = aio_group sub {
716 print "all stats done\n";
717 };
718
719 add $grp
720 (aio_stat ...),
721 (aio_stat ...),
722 ...;
723
724=item aio_nop $callback->()
725
726This is a special request - it does nothing in itself and is only used for
727side effects, such as when you want to add a dummy request to a group so
728that finishing the requests in the group depends on executing the given
729code.
730
731While this request does nothing, it still goes through the execution
732phase and still requires a worker thread. Thus, the callback will not
733be executed immediately but only after other requests in the queue have
734entered their execution phase. This can be used to measure request
735latency.
736
737=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
738
739Mainly used for debugging and benchmarking, this aio request puts one of
740the request workers to sleep for the given time.
741
742While it is theoretically handy to have simple I/O scheduling requests
743like sleep and file handle readable/writable, the overhead this creates is
744immense (it blocks a thread for a long time) so do not use this function
745except to put your application under artificial I/O pressure.
746
260=back 747=back
261 748
749=head2 IO::AIO::REQ CLASS
750
751All non-aggregate C<aio_*> functions return an object of this class when
752called in non-void context.
753
754=over 4
755
756=item cancel $req
757
758Cancels the request, if possible. Has the effect of skipping execution
759when entering the B<execute> state and skipping calling the callback when
760entering the the B<result> state, but will leave the request otherwise
761untouched. That means that requests that currently execute will not be
762stopped and resources held by the request will not be freed prematurely.
763
764=item cb $req $callback->(...)
765
766Replace (or simply set) the callback registered to the request.
767
768=back
769
770=head2 IO::AIO::GRP CLASS
771
772This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
773objects of this class, too.
774
775A IO::AIO::GRP object is a special request that can contain multiple other
776aio requests.
777
778You create one by calling the C<aio_group> constructing function with a
779callback that will be called when all contained requests have entered the
780C<done> state:
781
782 my $grp = aio_group sub {
783 print "all requests are done\n";
784 };
785
786You add requests by calling the C<add> method with one or more
787C<IO::AIO::REQ> objects:
788
789 $grp->add (aio_unlink "...");
790
791 add $grp aio_stat "...", sub {
792 $_[0] or return $grp->result ("error");
793
794 # add another request dynamically, if first succeeded
795 add $grp aio_open "...", sub {
796 $grp->result ("ok");
797 };
798 };
799
800This makes it very easy to create composite requests (see the source of
801C<aio_move> for an application) that work and feel like simple requests.
802
803=over 4
804
805=item * The IO::AIO::GRP objects will be cleaned up during calls to
806C<IO::AIO::poll_cb>, just like any other request.
807
808=item * They can be canceled like any other request. Canceling will cancel not
809only the request itself, but also all requests it contains.
810
811=item * They can also can also be added to other IO::AIO::GRP objects.
812
813=item * You must not add requests to a group from within the group callback (or
814any later time).
815
816=back
817
818Their lifetime, simplified, looks like this: when they are empty, they
819will finish very quickly. If they contain only requests that are in the
820C<done> state, they will also finish. Otherwise they will continue to
821exist.
822
823That means after creating a group you have some time to add requests. And
824in the callbacks of those requests, you can add further requests to the
825group. And only when all those requests have finished will the the group
826itself finish.
827
828=over 4
829
830=item add $grp ...
831
832=item $grp->add (...)
833
834Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
835be added, including other groups, as long as you do not create circular
836dependencies.
837
838Returns all its arguments.
839
840=item $grp->cancel_subs
841
842Cancel all subrequests and clears any feeder, but not the group request
843itself. Useful when you queued a lot of events but got a result early.
844
845=item $grp->result (...)
846
847Set the result value(s) that will be passed to the group callback when all
848subrequests have finished and set thre groups errno to the current value
849of errno (just like calling C<errno> without an error number). By default,
850no argument will be passed and errno is zero.
851
852=item $grp->errno ([$errno])
853
854Sets the group errno value to C<$errno>, or the current value of errno
855when the argument is missing.
856
857Every aio request has an associated errno value that is restored when
858the callback is invoked. This method lets you change this value from its
859default (0).
860
861Calling C<result> will also set errno, so make sure you either set C<$!>
862before the call to C<result>, or call c<errno> after it.
863
864=item feed $grp $callback->($grp)
865
866Sets a feeder/generator on this group: every group can have an attached
867generator that generates requests if idle. The idea behind this is that,
868although you could just queue as many requests as you want in a group,
869this might starve other requests for a potentially long time. For
870example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
871requests, delaying any later requests for a long time.
872
873To avoid this, and allow incremental generation of requests, you can
874instead a group and set a feeder on it that generates those requests. The
875feed callback will be called whenever there are few enough (see C<limit>,
876below) requests active in the group itself and is expected to queue more
877requests.
878
879The feed callback can queue as many requests as it likes (i.e. C<add> does
880not impose any limits).
881
882If the feed does not queue more requests when called, it will be
883automatically removed from the group.
884
885If the feed limit is C<0>, it will be set to C<2> automatically.
886
887Example:
888
889 # stat all files in @files, but only ever use four aio requests concurrently:
890
891 my $grp = aio_group sub { print "finished\n" };
892 limit $grp 4;
893 feed $grp sub {
894 my $file = pop @files
895 or return;
896
897 add $grp aio_stat $file, sub { ... };
898 };
899
900=item limit $grp $num
901
902Sets the feeder limit for the group: The feeder will be called whenever
903the group contains less than this many requests.
904
905Setting the limit to C<0> will pause the feeding process.
906
907=back
908
262=head2 SUPPORT FUNCTIONS 909=head2 SUPPORT FUNCTIONS
910
911=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
263 912
264=over 4 913=over 4
265 914
266=item $fileno = IO::AIO::poll_fileno 915=item $fileno = IO::AIO::poll_fileno
267 916
272 921
273See C<poll_cb> for an example. 922See C<poll_cb> for an example.
274 923
275=item IO::AIO::poll_cb 924=item IO::AIO::poll_cb
276 925
277Process all outstanding events on the result pipe. You have to call this 926Process some outstanding events on the result pipe. You have to call this
278regularly. Returns the number of events processed. Returns immediately 927regularly. Returns the number of events processed. Returns immediately
279when no events are outstanding. 928when no events are outstanding. The amount of events processed depends on
929the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
930
931If not all requests were processed for whatever reason, the filehandle
932will still be ready when C<poll_cb> returns.
280 933
281Example: Install an Event watcher that automatically calls 934Example: Install an Event watcher that automatically calls
282IO::AIO::poll_cb with high priority: 935IO::AIO::poll_cb with high priority:
283 936
284 Event->io (fd => IO::AIO::poll_fileno, 937 Event->io (fd => IO::AIO::poll_fileno,
285 poll => 'r', async => 1, 938 poll => 'r', async => 1,
286 cb => \&IO::AIO::poll_cb); 939 cb => \&IO::AIO::poll_cb);
287 940
941=item IO::AIO::max_poll_reqs $nreqs
942
943=item IO::AIO::max_poll_time $seconds
944
945These set the maximum number of requests (default C<0>, meaning infinity)
946that are being processed by C<IO::AIO::poll_cb> in one call, respectively
947the maximum amount of time (default C<0>, meaning infinity) spent in
948C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
949of time C<poll_cb> is allowed to use).
950
951Setting C<max_poll_time> to a non-zero value creates an overhead of one
952syscall per request processed, which is not normally a problem unless your
953callbacks are really really fast or your OS is really really slow (I am
954not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
955
956Setting these is useful if you want to ensure some level of
957interactiveness when perl is not fast enough to process all requests in
958time.
959
960For interactive programs, values such as C<0.01> to C<0.1> should be fine.
961
962Example: Install an Event watcher that automatically calls
963IO::AIO::poll_cb with low priority, to ensure that other parts of the
964program get the CPU sometimes even under high AIO load.
965
966 # try not to spend much more than 0.1s in poll_cb
967 IO::AIO::max_poll_time 0.1;
968
969 # use a low priority so other tasks have priority
970 Event->io (fd => IO::AIO::poll_fileno,
971 poll => 'r', nice => 1,
972 cb => &IO::AIO::poll_cb);
973
288=item IO::AIO::poll_wait 974=item IO::AIO::poll_wait
289 975
290Wait till the result filehandle becomes ready for reading (simply does a 976If there are any outstanding requests, wait till the result filehandle
291C<select> on the filehandle. This is useful if you want to synchronously wait 977becomes ready for reading (simply does a C<select> on the filehandle. This
292for some requests to finish). 978is useful if you want to synchronously wait for some requests to finish).
293 979
294See C<nreqs> for an example. 980See C<nreqs> for an example.
295 981
982=item IO::AIO::poll
983
984Waits until some requests have been handled.
985
986Returns the number of requests processed, but is otherwise strictly
987equivalent to:
988
989 IO::AIO::poll_wait, IO::AIO::poll_cb
990 if IO::AIO::nreqs;
991
296=item IO::AIO::nreqs 992=item IO::AIO::flush
297 993
298Returns the number of requests currently outstanding (i.e. for which their 994Wait till all outstanding AIO requests have been handled.
299callback has not been invoked yet).
300 995
301Example: wait till there are no outstanding requests anymore: 996Strictly equivalent to:
302 997
303 IO::AIO::poll_wait, IO::AIO::poll_cb 998 IO::AIO::poll_wait, IO::AIO::poll_cb
304 while IO::AIO::nreqs; 999 while IO::AIO::nreqs;
305 1000
306=item IO::AIO::flush 1001=head3 CONTROLLING THE NUMBER OF THREADS
307
308Wait till all outstanding AIO requests have been handled.
309
310Strictly equivalent to:
311
312 IO::AIO::poll_wait, IO::AIO::poll_cb
313 while IO::AIO::nreqs;
314
315=item IO::AIO::poll
316
317Waits until some requests have been handled.
318
319Strictly equivalent to:
320
321 IO::AIO::poll_wait, IO::AIO::poll_cb
322 if IO::AIO::nreqs;
323 1002
324=item IO::AIO::min_parallel $nthreads 1003=item IO::AIO::min_parallel $nthreads
325 1004
326Set the minimum number of AIO threads to C<$nthreads>. The current default 1005Set the minimum number of AIO threads to C<$nthreads>. The current
327is C<4>, which means four asynchronous operations can be done at one time 1006default is C<8>, which means eight asynchronous operations can execute
328(the number of outstanding operations, however, is unlimited). 1007concurrently at any one time (the number of outstanding requests,
1008however, is unlimited).
329 1009
330IO::AIO starts threads only on demand, when an AIO request is queued and 1010IO::AIO starts threads only on demand, when an AIO request is queued and
331no free thread exists. 1011no free thread exists. Please note that queueing up a hundred requests can
1012create demand for a hundred threads, even if it turns out that everything
1013is in the cache and could have been processed faster by a single thread.
332 1014
333It is recommended to keep the number of threads low, as some Linux 1015It is recommended to keep the number of threads relatively low, as some
334kernel versions will scale negatively with the number of threads (higher 1016Linux kernel versions will scale negatively with the number of threads
335parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 1017(higher parallelity => MUCH higher latency). With current Linux 2.6
336threads should be fine. 1018versions, 4-32 threads should be fine.
337 1019
338Under most circumstances you don't need to call this function, as the 1020Under most circumstances you don't need to call this function, as the
339module selects a default that is suitable for low to moderate load. 1021module selects a default that is suitable for low to moderate load.
340 1022
341=item IO::AIO::max_parallel $nthreads 1023=item IO::AIO::max_parallel $nthreads
350This module automatically runs C<max_parallel 0> at program end, to ensure 1032This module automatically runs C<max_parallel 0> at program end, to ensure
351that all threads are killed and that there are no outstanding requests. 1033that all threads are killed and that there are no outstanding requests.
352 1034
353Under normal circumstances you don't need to call this function. 1035Under normal circumstances you don't need to call this function.
354 1036
1037=item IO::AIO::max_idle $nthreads
1038
1039Limit the number of threads (default: 4) that are allowed to idle (i.e.,
1040threads that did not get a request to process within 10 seconds). That
1041means if a thread becomes idle while C<$nthreads> other threads are also
1042idle, it will free its resources and exit.
1043
1044This is useful when you allow a large number of threads (e.g. 100 or 1000)
1045to allow for extremely high load situations, but want to free resources
1046under normal circumstances (1000 threads can easily consume 30MB of RAM).
1047
1048The default is probably ok in most situations, especially if thread
1049creation is fast. If thread creation is very slow on your system you might
1050want to use larger values.
1051
355=item $oldnreqs = IO::AIO::max_outstanding $nreqs 1052=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
1053
1054This is a very bad function to use in interactive programs because it
1055blocks, and a bad way to reduce concurrency because it is inexact: Better
1056use an C<aio_group> together with a feed callback.
356 1057
357Sets the maximum number of outstanding requests to C<$nreqs>. If you 1058Sets the maximum number of outstanding requests to C<$nreqs>. If you
358try to queue up more than this number of requests, the caller will block until 1059to queue up more than this number of requests, the next call to the
359some requests have been handled. 1060C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1061function will block until the limit is no longer exceeded.
360 1062
361The default is very large, so normally there is no practical limit. If you 1063The default value is very large, so there is no practical limit on the
362queue up many requests in a loop it often improves speed if you set 1064number of outstanding requests.
363this to a relatively low number, such as C<100>.
364 1065
365Under normal circumstances you don't need to call this function. 1066You can still queue as many requests as you want. Therefore,
1067C<max_oustsanding> is mainly useful in simple scripts (with low values) or
1068as a stop gap to shield against fatal memory overflow (with large values).
1069
1070=head3 STATISTICAL INFORMATION
1071
1072=item IO::AIO::nreqs
1073
1074Returns the number of requests currently in the ready, execute or pending
1075states (i.e. for which their callback has not been invoked yet).
1076
1077Example: wait till there are no outstanding requests anymore:
1078
1079 IO::AIO::poll_wait, IO::AIO::poll_cb
1080 while IO::AIO::nreqs;
1081
1082=item IO::AIO::nready
1083
1084Returns the number of requests currently in the ready state (not yet
1085executed).
1086
1087=item IO::AIO::npending
1088
1089Returns the number of requests currently in the pending state (executed,
1090but not yet processed by poll_cb).
366 1091
367=back 1092=back
368 1093
369=cut 1094=cut
370 1095
382 or return undef; 1107 or return undef;
383 1108
384 *$sym 1109 *$sym
385} 1110}
386 1111
387min_parallel 4; 1112min_parallel 8;
388 1113
389END { 1114END {
390 max_parallel 0; 1115 min_parallel 1;
391} 1116 flush;
1117};
392 1118
3931; 11191;
394 1120
395=head2 FORK BEHAVIOUR 1121=head2 FORK BEHAVIOUR
1122
1123This module should do "the right thing" when the process using it forks:
396 1124
397Before the fork, IO::AIO enters a quiescent state where no requests 1125Before the fork, IO::AIO enters a quiescent state where no requests
398can be added in other threads and no results will be processed. After 1126can be added in other threads and no results will be processed. After
399the fork the parent simply leaves the quiescent state and continues 1127the fork the parent simply leaves the quiescent state and continues
400request/result processing, while the child clears the request/result 1128request/result processing, while the child frees the request/result queue
401queue (so the requests started before the fork will only be handled in 1129(so that the requests started before the fork will only be handled in the
402the parent). Threats will be started on demand until the limit ste in the 1130parent). Threads will be started on demand until the limit set in the
403parent process has been reached again. 1131parent process has been reached again.
404 1132
1133In short: the parent will, after a short pause, continue as if fork had
1134not been called, while the child will act as if IO::AIO has not been used
1135yet.
1136
1137=head2 MEMORY USAGE
1138
1139Per-request usage:
1140
1141Each aio request uses - depending on your architecture - around 100-200
1142bytes of memory. In addition, stat requests need a stat buffer (possibly
1143a few hundred bytes), readdir requires a result buffer and so on. Perl
1144scalars and other data passed into aio requests will also be locked and
1145will consume memory till the request has entered the done state.
1146
1147This is now awfully much, so queuing lots of requests is not usually a
1148problem.
1149
1150Per-thread usage:
1151
1152In the execution phase, some aio requests require more memory for
1153temporary buffers, and each thread requires a stack and other data
1154structures (usually around 16k-128k, depending on the OS).
1155
1156=head1 KNOWN BUGS
1157
1158Known bugs will be fixed in the next release.
1159
405=head1 SEE ALSO 1160=head1 SEE ALSO
406 1161
407L<Coro>, L<Linux::AIO>. 1162L<Coro::AIO>.
408 1163
409=head1 AUTHOR 1164=head1 AUTHOR
410 1165
411 Marc Lehmann <schmorp@schmorp.de> 1166 Marc Lehmann <schmorp@schmorp.de>
412 http://home.schmorp.de/ 1167 http://home.schmorp.de/

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