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Revision 1.37 by root, Tue Aug 23 12:37:19 2005 UTC vs.
Revision 1.89 by root, Sun Oct 29 11:03:18 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 this works on all types of file descriptors (for example sockets),
67using these functions on file descriptors that support nonblocking
68operation (again, sockets, pipes etc.) is very inefficient. Use an event
69loop for that (such as the L<Event|Event> module): IO::AIO will naturally
70fit into such an event loop itself.
71
43Currently, a number of threads are started that execute your read/writes 72In 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 73requests and signal their completion. You don't need thread support
45perl, and the threads created by this module will not be visible to the 74in 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 75to perl. In the future, this module might make use of the native aio
47aio functions available on many operating systems. However, they are often 76functions available on many operating systems. However, they are often
48not well-supported (Linux doesn't allow them on normal files currently, 77not 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 78files currently, for example), and they would only support aio_read and
50remaining functionality would have to be implemented using threads anyway. 79aio_write, so the remaining functionality would have to be implemented
80using threads anyway.
51 81
52Although the module will work with in the presence of other threads, it is 82Although the module will work with in the presence of other (Perl-)
53currently not reentrant, so use appropriate locking yourself, always call 83threads, 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 84locking yourself, always call C<poll_cb> from within the same thread, or
55C<aio_> functions) recursively. 85never call C<poll_cb> (or other C<aio_> functions) recursively.
86
87=head2 EXAMPLE
88
89This is a simple example that uses the Event module and loads
90F</etc/passwd> asynchronously:
91
92 use Fcntl;
93 use Event;
94 use IO::AIO;
95
96 # register the IO::AIO callback with Event
97 Event->io (fd => IO::AIO::poll_fileno,
98 poll => 'r',
99 cb => \&IO::AIO::poll_cb);
100
101 # queue the request to open /etc/passwd
102 aio_open "/etc/passwd", O_RDONLY, 0, sub {
103 my $fh = $_[0]
104 or die "error while opening: $!";
105
106 # stat'ing filehandles is generally non-blocking
107 my $size = -s $fh;
108
109 # queue a request to read the file
110 my $contents;
111 aio_read $fh, 0, $size, $contents, 0, sub {
112 $_[0] == $size
113 or die "short read: $!";
114
115 close $fh;
116
117 # file contents now in $contents
118 print $contents;
119
120 # exit event loop and program
121 Event::unloop;
122 };
123 };
124
125 # possibly queue up other requests, or open GUI windows,
126 # check for sockets etc. etc.
127
128 # process events as long as there are some:
129 Event::loop;
130
131=head1 REQUEST ANATOMY AND LIFETIME
132
133Every C<aio_*> function creates a request. which is a C data structure not
134directly visible to Perl.
135
136If called in non-void context, every request function returns a Perl
137object representing the request. In void context, nothing is returned,
138which saves a bit of memory.
139
140The perl object is a fairly standard ref-to-hash object. The hash contents
141are not used by IO::AIO so you are free to store anything you like in it.
142
143During their existance, aio requests travel through the following states,
144in order:
145
146=over 4
147
148=item ready
149
150Immediately after a request is created it is put into the ready state,
151waiting for a thread to execute it.
152
153=item execute
154
155A thread has accepted the request for processing and is currently
156executing it (e.g. blocking in read).
157
158=item pending
159
160The request has been executed and is waiting for result processing.
161
162While request submission and execution is fully asynchronous, result
163processing is not and relies on the perl interpreter calling C<poll_cb>
164(or another function with the same effect).
165
166=item result
167
168The request results are processed synchronously by C<poll_cb>.
169
170The C<poll_cb> function will process all outstanding aio requests by
171calling their callbacks, freeing memory associated with them and managing
172any groups they are contained in.
173
174=item done
175
176Request has reached the end of its lifetime and holds no resources anymore
177(except possibly for the Perl object, but its connection to the actual
178aio request is severed and calling its methods will either do nothing or
179result in a runtime error).
180
181=back
56 182
57=cut 183=cut
58 184
59package IO::AIO; 185package IO::AIO;
60 186
61no warnings; 187no warnings;
188use strict 'vars';
62 189
63use base 'Exporter'; 190use base 'Exporter';
64 191
65use Fcntl ();
66
67BEGIN { 192BEGIN {
68 $VERSION = 1.6; 193 our $VERSION = '2.1';
69 194
70 @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink 195 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71 aio_rmdir aio_readdir aio_symlink aio_fsync aio_fdatasync aio_readahead); 196 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); 197 aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
198 aio_copy aio_group aio_nop aio_mknod);
199 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
200 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
201 min_parallel max_parallel max_idle
202 nreqs nready npending nthreads
203 max_poll_time max_poll_reqs);
204
205 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
73 206
74 require XSLoader; 207 require XSLoader;
75 XSLoader::load IO::AIO, $VERSION; 208 XSLoader::load ("IO::AIO", $VERSION);
76} 209}
77 210
78=head1 FUNCTIONS 211=head1 FUNCTIONS
79 212
80=head2 AIO FUNCTIONS 213=head2 AIO REQUEST FUNCTIONS
81 214
82All the C<aio_*> calls are more or less thin wrappers around the syscall 215All the C<aio_*> calls are more or less thin wrappers around the syscall
83with the same name (sans C<aio_>). The arguments are similar or identical, 216with the same name (sans C<aio_>). The arguments are similar or identical,
84and they all accept an additional (and optional) C<$callback> argument 217and they all accept an additional (and optional) C<$callback> argument
85which must be a code reference. This code reference will get called with 218which must be a code reference. This code reference will get called with
88syscall has been executed asynchronously. 221syscall has been executed asynchronously.
89 222
90All functions expecting a filehandle keep a copy of the filehandle 223All functions expecting a filehandle keep a copy of the filehandle
91internally until the request has finished. 224internally until the request has finished.
92 225
226All functions return request objects of type L<IO::AIO::REQ> that allow
227further manipulation of those requests while they are in-flight.
228
93The pathnames you pass to these routines I<must> be absolute and 229The pathnames you pass to these routines I<must> be absolute and
94encoded in byte form. The reason for the former is that at the time the 230encoded as octets. The reason for the former is that at the time the
95request is being executed, the current working directory could have 231request is being executed, the current working directory could have
96changed. Alternatively, you can make sure that you never change the 232changed. Alternatively, you can make sure that you never change the
97current working directory. 233current working directory anywhere in the program and then use relative
234paths.
98 235
99To encode pathnames to byte form, either make sure you either: a) 236To encode pathnames as octets, either make sure you either: a) always pass
100always pass in filenames you got from outside (command line, readdir 237in filenames you got from outside (command line, readdir etc.) without
101etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode 238tinkering, 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 239your pathnames to the locale (or other) encoding in effect in the user
103environment, d) use Glib::filename_from_unicode on unicode filenames or e) 240environment, d) use Glib::filename_from_unicode on unicode filenames or e)
104use something else. 241use something else to ensure your scalar has the correct contents.
242
243This works, btw. independent of the internal UTF-8 bit, which IO::AIO
244handles correctly wether it is set or not.
105 245
106=over 4 246=over 4
107 247
248=item $prev_pri = aioreq_pri [$pri]
249
250Returns the priority value that would be used for the next request and, if
251C<$pri> is given, sets the priority for the next aio request.
252
253The default priority is C<0>, the minimum and maximum priorities are C<-4>
254and C<4>, respectively. Requests with higher priority will be serviced
255first.
256
257The priority will be reset to C<0> after each call to one of the C<aio_*>
258functions.
259
260Example: open a file with low priority, then read something from it with
261higher priority so the read request is serviced before other low priority
262open requests (potentially spamming the cache):
263
264 aioreq_pri -3;
265 aio_open ..., sub {
266 return unless $_[0];
267
268 aioreq_pri -2;
269 aio_read $_[0], ..., sub {
270 ...
271 };
272 };
273
274=item aioreq_nice $pri_adjust
275
276Similar to C<aioreq_pri>, but subtracts the given value from the current
277priority, so the effect is cumulative.
278
108=item aio_open $pathname, $flags, $mode, $callback 279=item aio_open $pathname, $flags, $mode, $callback->($fh)
109 280
110Asynchronously open or create a file and call the callback with a newly 281Asynchronously open or create a file and call the callback with a newly
111created filehandle for the file. 282created filehandle for the file.
112 283
113The pathname passed to C<aio_open> must be absolute. See API NOTES, above, 284The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
130 } else { 301 } else {
131 die "open failed: $!\n"; 302 die "open failed: $!\n";
132 } 303 }
133 }; 304 };
134 305
135=item aio_close $fh, $callback 306=item aio_close $fh, $callback->($status)
136 307
137Asynchronously close a file and call the callback with the result 308Asynchronously close a file and call the callback with the result
138code. I<WARNING:> although accepted, you should not pass in a perl 309code. I<WARNING:> although accepted, you should not pass in a perl
139filehandle here, as perl will likely close the file descriptor another 310filehandle here, as perl will likely close the file descriptor another
140time when the filehandle is destroyed. Normally, you can safely call perls 311time when the filehandle is destroyed. Normally, you can safely call perls
141C<close> or just let filehandles go out of scope. 312C<close> or just let filehandles go out of scope.
142 313
143This is supposed to be a bug in the API, so that might change. It's 314This is supposed to be a bug in the API, so that might change. It's
144therefore best to avoid this function. 315therefore best to avoid this function.
145 316
146=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback 317=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
147 318
148=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback 319=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149 320
150Reads or writes C<length> bytes from the specified C<fh> and C<offset> 321Reads or writes C<length> bytes from the specified C<fh> and C<offset>
151into the scalar given by C<data> and offset C<dataoffset> and calls the 322into the scalar given by C<data> and offset C<dataoffset> and calls the
152callback without the actual number of bytes read (or -1 on error, just 323callback without the actual number of bytes read (or -1 on error, just
153like the syscall). 324like the syscall).
162 aio_read $fh, 7, 15, $buffer, 0, sub { 333 aio_read $fh, 7, 15, $buffer, 0, sub {
163 $_[0] > 0 or die "read error: $!"; 334 $_[0] > 0 or die "read error: $!";
164 print "read $_[0] bytes: <$buffer>\n"; 335 print "read $_[0] bytes: <$buffer>\n";
165 }; 336 };
166 337
167=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback 338=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
168 339
169Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts 340Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
170reading at byte offset C<$in_offset>, and starts writing at the current 341reading at byte offset C<$in_offset>, and starts writing at the current
171file offset of C<$out_fh>. Because of that, it is not safe to issue more 342file offset of C<$out_fh>. Because of that, it is not safe to issue more
172than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each 343than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
185bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only 356bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
186provides the number of bytes written to C<$out_fh>. Only if the result 357provides the number of bytes written to C<$out_fh>. Only if the result
187value equals C<$length> one can assume that C<$length> bytes have been 358value equals C<$length> one can assume that C<$length> bytes have been
188read. 359read.
189 360
190=item aio_readahead $fh,$offset,$length, $callback 361=item aio_readahead $fh,$offset,$length, $callback->($retval)
191 362
192C<aio_readahead> populates the page cache with data from a file so that 363C<aio_readahead> populates the page cache with data from a file so that
193subsequent reads from that file will not block on disk I/O. The C<$offset> 364subsequent reads from that file will not block on disk I/O. The C<$offset>
194argument specifies the starting point from which data is to be read and 365argument specifies the starting point from which data is to be read and
195C<$length> specifies the number of bytes to be read. I/O is performed in 366C<$length> specifies the number of bytes to be read. I/O is performed in
199file. The current file offset of the file is left unchanged. 370file. The current file offset of the file is left unchanged.
200 371
201If that syscall doesn't exist (likely if your OS isn't Linux) it will be 372If that syscall doesn't exist (likely if your OS isn't Linux) it will be
202emulated by simply reading the data, which would have a similar effect. 373emulated by simply reading the data, which would have a similar effect.
203 374
204=item aio_stat $fh_or_path, $callback 375=item aio_stat $fh_or_path, $callback->($status)
205 376
206=item aio_lstat $fh, $callback 377=item aio_lstat $fh, $callback->($status)
207 378
208Works like perl's C<stat> or C<lstat> in void context. The callback will 379Works like perl's C<stat> or C<lstat> in void context. The callback will
209be called after the stat and the results will be available using C<stat _> 380be called after the stat and the results will be available using C<stat _>
210or C<-s _> etc... 381or C<-s _> etc...
211 382
221 aio_stat "/etc/passwd", sub { 392 aio_stat "/etc/passwd", sub {
222 $_[0] and die "stat failed: $!"; 393 $_[0] and die "stat failed: $!";
223 print "size is ", -s _, "\n"; 394 print "size is ", -s _, "\n";
224 }; 395 };
225 396
226=item aio_unlink $pathname, $callback 397=item aio_unlink $pathname, $callback->($status)
227 398
228Asynchronously unlink (delete) a file and call the callback with the 399Asynchronously unlink (delete) a file and call the callback with the
229result code. 400result code.
230 401
402=item aio_mknod $path, $mode, $dev, $callback->($status)
403
404[EXPERIMENTAL]
405
406Asynchronously create a device node (or fifo). See mknod(2).
407
408The only (POSIX-) portable way of calling this function is:
409
410 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
411
412=item aio_link $srcpath, $dstpath, $callback->($status)
413
414Asynchronously create a new link to the existing object at C<$srcpath> at
415the path C<$dstpath> and call the callback with the result code.
416
417=item aio_symlink $srcpath, $dstpath, $callback->($status)
418
419Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
420the path C<$dstpath> and call the callback with the result code.
421
422=item aio_rename $srcpath, $dstpath, $callback->($status)
423
424Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
425rename(2) and call the callback with the result code.
426
231=item aio_rmdir $pathname, $callback 427=item aio_rmdir $pathname, $callback->($status)
232 428
233Asynchronously rmdir (delete) a directory and call the callback with the 429Asynchronously rmdir (delete) a directory and call the callback with the
234result code. 430result code.
235 431
236=item aio_readdir $pathname $callback 432=item aio_readdir $pathname, $callback->($entries)
237 433
238Unlike the POSIX call of the same name, C<aio_readdir> reads an entire 434Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
239directory (i.e. opendir + readdir + closedir). The entries will not be 435directory (i.e. opendir + readdir + closedir). The entries will not be
240sorted, and will B<NOT> include the C<.> and C<..> entries. 436sorted, and will B<NOT> include the C<.> and C<..> entries.
241 437
242The callback a single argument which is either C<undef> or an array-ref 438The callback a single argument which is either C<undef> or an array-ref
243with the filenames. 439with the filenames.
244 440
441=item aio_copy $srcpath, $dstpath, $callback->($status)
442
443Try to copy the I<file> (directories not supported as either source or
444destination) from C<$srcpath> to C<$dstpath> and call the callback with
445the C<0> (error) or C<-1> ok.
446
447This is a composite request that it creates the destination file with
448mode 0200 and copies the contents of the source file into it using
449C<aio_sendfile>, followed by restoring atime, mtime, access mode and
450uid/gid, in that order.
451
452If an error occurs, the partial destination file will be unlinked, if
453possible, except when setting atime, mtime, access mode and uid/gid, where
454errors are being ignored.
455
456=cut
457
458sub aio_copy($$;$) {
459 my ($src, $dst, $cb) = @_;
460
461 my $pri = aioreq_pri;
462 my $grp = aio_group $cb;
463
464 aioreq_pri $pri;
465 add $grp aio_open $src, O_RDONLY, 0, sub {
466 if (my $src_fh = $_[0]) {
467 my @stat = stat $src_fh;
468
469 aioreq_pri $pri;
470 add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
471 if (my $dst_fh = $_[0]) {
472 aioreq_pri $pri;
473 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
474 if ($_[0] == $stat[7]) {
475 $grp->result (0);
476 close $src_fh;
477
478 # those should not normally block. should. should.
479 utime $stat[8], $stat[9], $dst;
480 chmod $stat[2] & 07777, $dst_fh;
481 chown $stat[4], $stat[5], $dst_fh;
482 close $dst_fh;
483 } else {
484 $grp->result (-1);
485 close $src_fh;
486 close $dst_fh;
487
488 aioreq $pri;
489 add $grp aio_unlink $dst;
490 }
491 };
492 } else {
493 $grp->result (-1);
494 }
495 },
496
497 } else {
498 $grp->result (-1);
499 }
500 };
501
502 $grp
503}
504
505=item aio_move $srcpath, $dstpath, $callback->($status)
506
507Try to move the I<file> (directories not supported as either source or
508destination) from C<$srcpath> to C<$dstpath> and call the callback with
509the C<0> (error) or C<-1> ok.
510
511This is a composite request that tries to rename(2) the file first. If
512rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
513that is successful, unlinking the C<$srcpath>.
514
515=cut
516
517sub aio_move($$;$) {
518 my ($src, $dst, $cb) = @_;
519
520 my $pri = aioreq_pri;
521 my $grp = aio_group $cb;
522
523 aioreq_pri $pri;
524 add $grp aio_rename $src, $dst, sub {
525 if ($_[0] && $! == EXDEV) {
526 aioreq_pri $pri;
527 add $grp aio_copy $src, $dst, sub {
528 $grp->result ($_[0]);
529
530 if (!$_[0]) {
531 aioreq_pri $pri;
532 add $grp aio_unlink $src;
533 }
534 };
535 } else {
536 $grp->result ($_[0]);
537 }
538 };
539
540 $grp
541}
542
543=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
544
545Scans a directory (similar to C<aio_readdir>) but additionally tries to
546efficiently separate the entries of directory C<$path> into two sets of
547names, directories you can recurse into (directories), and ones you cannot
548recurse into (everything else, including symlinks to directories).
549
550C<aio_scandir> is a composite request that creates of many sub requests_
551C<$maxreq> specifies the maximum number of outstanding aio requests that
552this function generates. If it is C<< <= 0 >>, then a suitable default
553will be chosen (currently 4).
554
555On error, the callback is called without arguments, otherwise it receives
556two array-refs with path-relative entry names.
557
558Example:
559
560 aio_scandir $dir, 0, sub {
561 my ($dirs, $nondirs) = @_;
562 print "real directories: @$dirs\n";
563 print "everything else: @$nondirs\n";
564 };
565
566Implementation notes.
567
568The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
569
570After reading the directory, the modification time, size etc. of the
571directory before and after the readdir is checked, and if they match (and
572isn't the current time), the link count will be used to decide how many
573entries are directories (if >= 2). Otherwise, no knowledge of the number
574of subdirectories will be assumed.
575
576Then entries will be sorted into likely directories (everything without
577a non-initial dot currently) and likely non-directories (everything
578else). Then every entry plus an appended C</.> will be C<stat>'ed,
579likely directories first. If that succeeds, it assumes that the entry
580is a directory or a symlink to directory (which will be checked
581seperately). This is often faster than stat'ing the entry itself because
582filesystems might detect the type of the entry without reading the inode
583data (e.g. ext2fs filetype feature).
584
585If the known number of directories (link count - 2) has been reached, the
586rest of the entries is assumed to be non-directories.
587
588This only works with certainty on POSIX (= UNIX) filesystems, which
589fortunately are the vast majority of filesystems around.
590
591It will also likely work on non-POSIX filesystems with reduced efficiency
592as those tend to return 0 or 1 as link counts, which disables the
593directory counting heuristic.
594
595=cut
596
597sub aio_scandir($$$) {
598 my ($path, $maxreq, $cb) = @_;
599
600 my $pri = aioreq_pri;
601
602 my $grp = aio_group $cb;
603
604 $maxreq = 4 if $maxreq <= 0;
605
606 # stat once
607 aioreq_pri $pri;
608 add $grp aio_stat $path, sub {
609 return $grp->result () if $_[0];
610 my $now = time;
611 my $hash1 = join ":", (stat _)[0,1,3,7,9];
612
613 # read the directory entries
614 aioreq_pri $pri;
615 add $grp aio_readdir $path, sub {
616 my $entries = shift
617 or return $grp->result ();
618
619 # stat the dir another time
620 aioreq_pri $pri;
621 add $grp aio_stat $path, sub {
622 my $hash2 = join ":", (stat _)[0,1,3,7,9];
623
624 my $ndirs;
625
626 # take the slow route if anything looks fishy
627 if ($hash1 ne $hash2 or (stat _)[9] == $now) {
628 $ndirs = -1;
629 } else {
630 # if nlink == 2, we are finished
631 # on non-posix-fs's, we rely on nlink < 2
632 $ndirs = (stat _)[3] - 2
633 or return $grp->result ([], $entries);
634 }
635
636 # sort into likely dirs and likely nondirs
637 # dirs == files without ".", short entries first
638 $entries = [map $_->[0],
639 sort { $b->[1] cmp $a->[1] }
640 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
641 @$entries];
642
643 my (@dirs, @nondirs);
644
645 my $statgrp = add $grp aio_group sub {
646 $grp->result (\@dirs, \@nondirs);
647 };
648
649 limit $statgrp $maxreq;
650 feed $statgrp sub {
651 return unless @$entries;
652 my $entry = pop @$entries;
653
654 aioreq_pri $pri;
655 add $statgrp aio_stat "$path/$entry/.", sub {
656 if ($_[0] < 0) {
657 push @nondirs, $entry;
658 } else {
659 # need to check for real directory
660 aioreq_pri $pri;
661 add $statgrp aio_lstat "$path/$entry", sub {
662 if (-d _) {
663 push @dirs, $entry;
664
665 unless (--$ndirs) {
666 push @nondirs, @$entries;
667 feed $statgrp;
668 }
669 } else {
670 push @nondirs, $entry;
671 }
672 }
673 }
674 };
675 };
676 };
677 };
678 };
679
680 $grp
681}
682
245=item aio_fsync $fh, $callback 683=item aio_fsync $fh, $callback->($status)
246 684
247Asynchronously call fsync on the given filehandle and call the callback 685Asynchronously call fsync on the given filehandle and call the callback
248with the fsync result code. 686with the fsync result code.
249 687
250=item aio_fdatasync $fh, $callback 688=item aio_fdatasync $fh, $callback->($status)
251 689
252Asynchronously call fdatasync on the given filehandle and call the 690Asynchronously call fdatasync on the given filehandle and call the
253callback with the fdatasync result code. 691callback with the fdatasync result code.
254 692
255If this call isn't available because your OS lacks it or it couldn't be 693If this call isn't available because your OS lacks it or it couldn't be
256detected, it will be emulated by calling C<fsync> instead. 694detected, it will be emulated by calling C<fsync> instead.
257 695
696=item aio_group $callback->(...)
697
698This is a very special aio request: Instead of doing something, it is a
699container for other aio requests, which is useful if you want to bundle
700many requests into a single, composite, request with a definite callback
701and the ability to cancel the whole request with its subrequests.
702
703Returns an object of class L<IO::AIO::GRP>. See its documentation below
704for more info.
705
706Example:
707
708 my $grp = aio_group sub {
709 print "all stats done\n";
710 };
711
712 add $grp
713 (aio_stat ...),
714 (aio_stat ...),
715 ...;
716
717=item aio_nop $callback->()
718
719This is a special request - it does nothing in itself and is only used for
720side effects, such as when you want to add a dummy request to a group so
721that finishing the requests in the group depends on executing the given
722code.
723
724While this request does nothing, it still goes through the execution
725phase and still requires a worker thread. Thus, the callback will not
726be executed immediately but only after other requests in the queue have
727entered their execution phase. This can be used to measure request
728latency.
729
730=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
731
732Mainly used for debugging and benchmarking, this aio request puts one of
733the request workers to sleep for the given time.
734
735While it is theoretically handy to have simple I/O scheduling requests
736like sleep and file handle readable/writable, the overhead this creates is
737immense (it blocks a thread for a long time) so do not use this function
738except to put your application under artificial I/O pressure.
739
258=back 740=back
259 741
742=head2 IO::AIO::REQ CLASS
743
744All non-aggregate C<aio_*> functions return an object of this class when
745called in non-void context.
746
747=over 4
748
749=item cancel $req
750
751Cancels the request, if possible. Has the effect of skipping execution
752when entering the B<execute> state and skipping calling the callback when
753entering the the B<result> state, but will leave the request otherwise
754untouched. That means that requests that currently execute will not be
755stopped and resources held by the request will not be freed prematurely.
756
757=item cb $req $callback->(...)
758
759Replace (or simply set) the callback registered to the request.
760
761=back
762
763=head2 IO::AIO::GRP CLASS
764
765This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
766objects of this class, too.
767
768A IO::AIO::GRP object is a special request that can contain multiple other
769aio requests.
770
771You create one by calling the C<aio_group> constructing function with a
772callback that will be called when all contained requests have entered the
773C<done> state:
774
775 my $grp = aio_group sub {
776 print "all requests are done\n";
777 };
778
779You add requests by calling the C<add> method with one or more
780C<IO::AIO::REQ> objects:
781
782 $grp->add (aio_unlink "...");
783
784 add $grp aio_stat "...", sub {
785 $_[0] or return $grp->result ("error");
786
787 # add another request dynamically, if first succeeded
788 add $grp aio_open "...", sub {
789 $grp->result ("ok");
790 };
791 };
792
793This makes it very easy to create composite requests (see the source of
794C<aio_move> for an application) that work and feel like simple requests.
795
796=over 4
797
798=item * The IO::AIO::GRP objects will be cleaned up during calls to
799C<IO::AIO::poll_cb>, just like any other request.
800
801=item * They can be canceled like any other request. Canceling will cancel not
802only the request itself, but also all requests it contains.
803
804=item * They can also can also be added to other IO::AIO::GRP objects.
805
806=item * You must not add requests to a group from within the group callback (or
807any later time).
808
809=back
810
811Their lifetime, simplified, looks like this: when they are empty, they
812will finish very quickly. If they contain only requests that are in the
813C<done> state, they will also finish. Otherwise they will continue to
814exist.
815
816That means after creating a group you have some time to add requests. And
817in the callbacks of those requests, you can add further requests to the
818group. And only when all those requests have finished will the the group
819itself finish.
820
821=over 4
822
823=item add $grp ...
824
825=item $grp->add (...)
826
827Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
828be added, including other groups, as long as you do not create circular
829dependencies.
830
831Returns all its arguments.
832
833=item $grp->cancel_subs
834
835Cancel all subrequests and clears any feeder, but not the group request
836itself. Useful when you queued a lot of events but got a result early.
837
838=item $grp->result (...)
839
840Set the result value(s) that will be passed to the group callback when all
841subrequests have finished and set thre groups errno to the current value
842of errno (just like calling C<errno> without an error number). By default,
843no argument will be passed and errno is zero.
844
845=item $grp->errno ([$errno])
846
847Sets the group errno value to C<$errno>, or the current value of errno
848when the argument is missing.
849
850Every aio request has an associated errno value that is restored when
851the callback is invoked. This method lets you change this value from its
852default (0).
853
854Calling C<result> will also set errno, so make sure you either set C<$!>
855before the call to C<result>, or call c<errno> after it.
856
857=item feed $grp $callback->($grp)
858
859Sets a feeder/generator on this group: every group can have an attached
860generator that generates requests if idle. The idea behind this is that,
861although you could just queue as many requests as you want in a group,
862this might starve other requests for a potentially long time. For
863example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
864requests, delaying any later requests for a long time.
865
866To avoid this, and allow incremental generation of requests, you can
867instead a group and set a feeder on it that generates those requests. The
868feed callback will be called whenever there are few enough (see C<limit>,
869below) requests active in the group itself and is expected to queue more
870requests.
871
872The feed callback can queue as many requests as it likes (i.e. C<add> does
873not impose any limits).
874
875If the feed does not queue more requests when called, it will be
876automatically removed from the group.
877
878If the feed limit is C<0>, it will be set to C<2> automatically.
879
880Example:
881
882 # stat all files in @files, but only ever use four aio requests concurrently:
883
884 my $grp = aio_group sub { print "finished\n" };
885 limit $grp 4;
886 feed $grp sub {
887 my $file = pop @files
888 or return;
889
890 add $grp aio_stat $file, sub { ... };
891 };
892
893=item limit $grp $num
894
895Sets the feeder limit for the group: The feeder will be called whenever
896the group contains less than this many requests.
897
898Setting the limit to C<0> will pause the feeding process.
899
900=back
901
260=head2 SUPPORT FUNCTIONS 902=head2 SUPPORT FUNCTIONS
903
904=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
261 905
262=over 4 906=over 4
263 907
264=item $fileno = IO::AIO::poll_fileno 908=item $fileno = IO::AIO::poll_fileno
265 909
270 914
271See C<poll_cb> for an example. 915See C<poll_cb> for an example.
272 916
273=item IO::AIO::poll_cb 917=item IO::AIO::poll_cb
274 918
275Process all outstanding events on the result pipe. You have to call this 919Process some outstanding events on the result pipe. You have to call this
276regularly. Returns the number of events processed. Returns immediately 920regularly. Returns the number of events processed. Returns immediately
277when no events are outstanding. 921when no events are outstanding. The amount of events processed depends on
922the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
923
924If not all requests were processed for whatever reason, the filehandle
925will still be ready when C<poll_cb> returns.
278 926
279Example: Install an Event watcher that automatically calls 927Example: Install an Event watcher that automatically calls
280IO::AIO::poll_cb with high priority: 928IO::AIO::poll_cb with high priority:
281 929
282 Event->io (fd => IO::AIO::poll_fileno, 930 Event->io (fd => IO::AIO::poll_fileno,
283 poll => 'r', async => 1, 931 poll => 'r', async => 1,
284 cb => \&IO::AIO::poll_cb); 932 cb => \&IO::AIO::poll_cb);
285 933
934=item IO::AIO::max_poll_reqs $nreqs
935
936=item IO::AIO::max_poll_time $seconds
937
938These set the maximum number of requests (default C<0>, meaning infinity)
939that are being processed by C<IO::AIO::poll_cb> in one call, respectively
940the maximum amount of time (default C<0>, meaning infinity) spent in
941C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
942of time C<poll_cb> is allowed to use).
943
944Setting C<max_poll_time> to a non-zero value creates an overhead of one
945syscall per request processed, which is not normally a problem unless your
946callbacks are really really fast or your OS is really really slow (I am
947not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
948
949Setting these is useful if you want to ensure some level of
950interactiveness when perl is not fast enough to process all requests in
951time.
952
953For interactive programs, values such as C<0.01> to C<0.1> should be fine.
954
955Example: Install an Event watcher that automatically calls
956IO::AIO::poll_cb with low priority, to ensure that other parts of the
957program get the CPU sometimes even under high AIO load.
958
959 # try not to spend much more than 0.1s in poll_cb
960 IO::AIO::max_poll_time 0.1;
961
962 # use a low priority so other tasks have priority
963 Event->io (fd => IO::AIO::poll_fileno,
964 poll => 'r', nice => 1,
965 cb => &IO::AIO::poll_cb);
966
286=item IO::AIO::poll_wait 967=item IO::AIO::poll_wait
287 968
288Wait till the result filehandle becomes ready for reading (simply does a 969Wait till the result filehandle becomes ready for reading (simply does a
289C<select> on the filehandle. This is useful if you want to synchronously wait 970C<select> on the filehandle. This is useful if you want to synchronously
290for some requests to finish). 971wait for some requests to finish).
291 972
292See C<nreqs> for an example. 973See C<nreqs> for an example.
293 974
975=item IO::AIO::poll
976
977Waits until some requests have been handled.
978
979Strictly equivalent to:
980
981 IO::AIO::poll_wait, IO::AIO::poll_cb
982 if IO::AIO::nreqs;
983
294=item IO::AIO::nreqs 984=item IO::AIO::flush
295 985
296Returns the number of requests currently outstanding (i.e. for which their 986Wait till all outstanding AIO requests have been handled.
297callback has not been invoked yet).
298 987
299Example: wait till there are no outstanding requests anymore: 988Strictly equivalent to:
300 989
301 IO::AIO::poll_wait, IO::AIO::poll_cb 990 IO::AIO::poll_wait, IO::AIO::poll_cb
302 while IO::AIO::nreqs; 991 while IO::AIO::nreqs;
303 992
304=item IO::AIO::flush 993=head3 CONTROLLING THE NUMBER OF THREADS
305
306Wait till all outstanding AIO requests have been handled.
307
308Strictly equivalent to:
309
310 IO::AIO::poll_wait, IO::AIO::poll_cb
311 while IO::AIO::nreqs;
312
313=item IO::AIO::poll
314
315Waits until some requests have been handled.
316
317Strictly equivalent to:
318
319 IO::AIO::poll_wait, IO::AIO::poll_cb
320 if IO::AIO::nreqs;
321 994
322=item IO::AIO::min_parallel $nthreads 995=item IO::AIO::min_parallel $nthreads
323 996
324Set the minimum number of AIO threads to C<$nthreads>. The current default 997Set the minimum number of AIO threads to C<$nthreads>. The current
325is C<4>, which means four asynchronous operations can be done at one time 998default is C<8>, which means eight asynchronous operations can execute
326(the number of outstanding operations, however, is unlimited). 999concurrently at any one time (the number of outstanding requests,
1000however, is unlimited).
327 1001
328IO::AIO starts threads only on demand, when an AIO request is queued and 1002IO::AIO starts threads only on demand, when an AIO request is queued and
329no free thread exists. 1003no free thread exists. Please note that queueing up a hundred requests can
1004create demand for a hundred threads, even if it turns out that everything
1005is in the cache and could have been processed faster by a single thread.
330 1006
331It is recommended to keep the number of threads low, as some Linux 1007It is recommended to keep the number of threads relatively low, as some
332kernel versions will scale negatively with the number of threads (higher 1008Linux kernel versions will scale negatively with the number of threads
333parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 1009(higher parallelity => MUCH higher latency). With current Linux 2.6
334threads should be fine. 1010versions, 4-32 threads should be fine.
335 1011
336Under most circumstances you don't need to call this function, as the 1012Under most circumstances you don't need to call this function, as the
337module selects a default that is suitable for low to moderate load. 1013module selects a default that is suitable for low to moderate load.
338 1014
339=item IO::AIO::max_parallel $nthreads 1015=item IO::AIO::max_parallel $nthreads
348This module automatically runs C<max_parallel 0> at program end, to ensure 1024This module automatically runs C<max_parallel 0> at program end, to ensure
349that all threads are killed and that there are no outstanding requests. 1025that all threads are killed and that there are no outstanding requests.
350 1026
351Under normal circumstances you don't need to call this function. 1027Under normal circumstances you don't need to call this function.
352 1028
1029=item IO::AIO::max_idle $nthreads
1030
1031Limit the number of threads (default: 4) that are allowed to idle (i.e.,
1032threads that did not get a request to process within 10 seconds). That
1033means if a thread becomes idle while C<$nthreads> other threads are also
1034idle, it will free its resources and exit.
1035
1036This is useful when you allow a large number of threads (e.g. 100 or 1000)
1037to allow for extremely high load situations, but want to free resources
1038under normal circumstances (1000 threads can easily consume 30MB of RAM).
1039
1040The default is probably ok in most situations, especially if thread
1041creation is fast. If thread creation is very slow on your system you might
1042want to use larger values.
1043
353=item $oldnreqs = IO::AIO::max_outstanding $nreqs 1044=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
1045
1046This is a very bad function to use in interactive programs because it
1047blocks, and a bad way to reduce concurrency because it is inexact: Better
1048use an C<aio_group> together with a feed callback.
354 1049
355Sets the maximum number of outstanding requests to C<$nreqs>. If you 1050Sets the maximum number of outstanding requests to C<$nreqs>. If you
356try to queue up more than this number of requests, the caller will block until 1051to queue up more than this number of requests, the next call to the
357some requests have been handled. 1052C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1053function will block until the limit is no longer exceeded.
358 1054
359The default is very large, so normally there is no practical limit. If you 1055The default value is very large, so there is no practical limit on the
360queue up many requests in a loop it often improves speed if you set 1056number of outstanding requests.
361this to a relatively low number, such as C<100>.
362 1057
363Under normal circumstances you don't need to call this function. 1058You can still queue as many requests as you want. Therefore,
1059C<max_oustsanding> is mainly useful in simple scripts (with low values) or
1060as a stop gap to shield against fatal memory overflow (with large values).
1061
1062=head3 STATISTICAL INFORMATION
1063
1064=item IO::AIO::nreqs
1065
1066Returns the number of requests currently in the ready, execute or pending
1067states (i.e. for which their callback has not been invoked yet).
1068
1069Example: wait till there are no outstanding requests anymore:
1070
1071 IO::AIO::poll_wait, IO::AIO::poll_cb
1072 while IO::AIO::nreqs;
1073
1074=item IO::AIO::nready
1075
1076Returns the number of requests currently in the ready state (not yet
1077executed).
1078
1079=item IO::AIO::npending
1080
1081Returns the number of requests currently in the pending state (executed,
1082but not yet processed by poll_cb).
364 1083
365=back 1084=back
366 1085
367=cut 1086=cut
368 1087
380 or return undef; 1099 or return undef;
381 1100
382 *$sym 1101 *$sym
383} 1102}
384 1103
385min_parallel 4; 1104min_parallel 8;
386 1105
387END { 1106END {
388 max_parallel 0; 1107 min_parallel 1;
389} 1108 flush;
1109};
390 1110
3911; 11111;
392 1112
393=head2 FORK BEHAVIOUR 1113=head2 FORK BEHAVIOUR
1114
1115This module should do "the right thing" when the process using it forks:
394 1116
395Before the fork, IO::AIO enters a quiescent state where no requests 1117Before the fork, IO::AIO enters a quiescent state where no requests
396can be added in other threads and no results will be processed. After 1118can be added in other threads and no results will be processed. After
397the fork the parent simply leaves the quiescent state and continues 1119the fork the parent simply leaves the quiescent state and continues
398request/result processing, while the child clears the request/result 1120request/result processing, while the child frees the request/result queue
399queue (so the requests started before the fork will only be handled in 1121(so that the requests started before the fork will only be handled in the
400the parent). Threats will be started on demand until the limit ste in the 1122parent). Threads will be started on demand until the limit set in the
401parent process has been reached again. 1123parent process has been reached again.
402 1124
1125In short: the parent will, after a short pause, continue as if fork had
1126not been called, while the child will act as if IO::AIO has not been used
1127yet.
1128
1129=head2 MEMORY USAGE
1130
1131Per-request usage:
1132
1133Each aio request uses - depending on your architecture - around 100-200
1134bytes of memory. In addition, stat requests need a stat buffer (possibly
1135a few hundred bytes), readdir requires a result buffer and so on. Perl
1136scalars and other data passed into aio requests will also be locked and
1137will consume memory till the request has entered the done state.
1138
1139This is now awfully much, so queuing lots of requests is not usually a
1140problem.
1141
1142Per-thread usage:
1143
1144In the execution phase, some aio requests require more memory for
1145temporary buffers, and each thread requires a stack and other data
1146structures (usually around 16k-128k, depending on the OS).
1147
1148=head1 KNOWN BUGS
1149
1150Known bugs will be fixed in the next release.
1151
403=head1 SEE ALSO 1152=head1 SEE ALSO
404 1153
405L<Coro>, L<Linux::AIO>. 1154L<Coro::AIO>.
406 1155
407=head1 AUTHOR 1156=head1 AUTHOR
408 1157
409 Marc Lehmann <schmorp@schmorp.de> 1158 Marc Lehmann <schmorp@schmorp.de>
410 http://home.schmorp.de/ 1159 http://home.schmorp.de/

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