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Revision 1.50 by root, Sat Jun 24 16:27:02 2006 UTC vs.
Revision 1.73 by root, Tue Oct 24 16:35:04 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 # AnyEvent 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
21 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; 31 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
22 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb }); 32 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
23 33
24 # Event 34 # Event integration
25 Event->io (fd => IO::AIO::poll_fileno, 35 Event->io (fd => IO::AIO::poll_fileno,
26 poll => 'r', 36 poll => 'r',
27 cb => \&IO::AIO::poll_cb); 37 cb => \&IO::AIO::poll_cb);
28 38
29 # Glib/Gtk2 39 # Glib/Gtk2 integration
30 add_watch Glib::IO IO::AIO::poll_fileno, 40 add_watch Glib::IO IO::AIO::poll_fileno,
31 in => sub { IO::AIO::poll_cb; 1 }; 41 in => sub { IO::AIO::poll_cb; 1 };
32 42
33 # Tk 43 # Tk integration
34 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", 44 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
35 readable => \&IO::AIO::poll_cb); 45 readable => \&IO::AIO::poll_cb);
36 46
37 # Danga::Socket 47 # Danga::Socket integration
38 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 48 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
39 \&IO::AIO::poll_cb); 49 \&IO::AIO::poll_cb);
40 50
41
42=head1 DESCRIPTION 51=head1 DESCRIPTION
43 52
44This module implements asynchronous I/O using whatever means your 53This module implements asynchronous I/O using whatever means your
45operating system supports. 54operating system supports.
46 55
47Currently, a number of threads are started that execute your read/writes 56In this version, a number of threads are started that execute your
48and signal their completion. You don't need thread support in your libc or 57requests and signal their completion. You don't need thread support
49perl, and the threads created by this module will not be visible to the 58in perl, and the threads created by this module will not be visible
50pthreads library. In the future, this module might make use of the native 59to perl. In the future, this module might make use of the native aio
51aio functions available on many operating systems. However, they are often 60functions available on many operating systems. However, they are often
52not well-supported (Linux doesn't allow them on normal files currently, 61not well-supported or restricted (Linux doesn't allow them on normal
53for example), and they would only support aio_read and aio_write, so the 62files currently, for example), and they would only support aio_read and
54remaining functionality would have to be implemented using threads anyway. 63aio_write, so the remaining functionality would have to be implemented
64using threads anyway.
55 65
56Although the module will work with in the presence of other threads, it is 66Although the module will work with in the presence of other (Perl-)
57currently not reentrant, so use appropriate locking yourself, always call 67threads, it is currently not reentrant in any way, so use appropriate
58C<poll_cb> from within the same thread, or never call C<poll_cb> (or other 68locking yourself, always call C<poll_cb> from within the same thread, or
59C<aio_> functions) recursively. 69never call C<poll_cb> (or other C<aio_> functions) recursively.
70
71=head1 REQUEST ANATOMY AND LIFETIME
72
73Every C<aio_*> function creates a request. which is a C data structure not
74directly visible to Perl.
75
76If called in non-void context, every request function returns a Perl
77object representing the request. In void context, nothing is returned,
78which saves a bit of memory.
79
80The perl object is a fairly standard ref-to-hash object. The hash contents
81are not used by IO::AIO so you are free to store anything you like in it.
82
83During their existance, aio requests travel through the following states,
84in order:
85
86=over 4
87
88=item ready
89
90Immediately after a request is created it is put into the ready state,
91waiting for a thread to execute it.
92
93=item execute
94
95A thread has accepted the request for processing and is currently
96executing it (e.g. blocking in read).
97
98=item pending
99
100The request has been executed and is waiting for result processing.
101
102While request submission and execution is fully asynchronous, result
103processing is not and relies on the perl interpreter calling C<poll_cb>
104(or another function with the same effect).
105
106=item result
107
108The request results are processed synchronously by C<poll_cb>.
109
110The C<poll_cb> function will process all outstanding aio requests by
111calling their callbacks, freeing memory associated with them and managing
112any groups they are contained in.
113
114=item done
115
116Request has reached the end of its lifetime and holds no resources anymore
117(except possibly for the Perl object, but its connection to the actual
118aio request is severed and calling its methods will either do nothing or
119result in a runtime error).
60 120
61=cut 121=cut
62 122
63package IO::AIO; 123package IO::AIO;
64 124
65no warnings; 125no warnings;
126use strict 'vars';
66 127
67use base 'Exporter'; 128use base 'Exporter';
68 129
69use Fcntl ();
70
71BEGIN { 130BEGIN {
72 $VERSION = '1.8'; 131 our $VERSION = '2.0';
73 132
74 @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat 133 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
75 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink 134 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
76 aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move); 135 aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
77 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel 136 aio_group aio_nop);
78 max_outstanding nreqs); 137 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
138 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
139 min_parallel max_parallel max_outstanding nreqs);
140
141 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
79 142
80 require XSLoader; 143 require XSLoader;
81 XSLoader::load IO::AIO, $VERSION; 144 XSLoader::load ("IO::AIO", $VERSION);
82} 145}
83 146
84=head1 FUNCTIONS 147=head1 FUNCTIONS
85 148
86=head2 AIO FUNCTIONS 149=head2 AIO FUNCTIONS
94syscall has been executed asynchronously. 157syscall has been executed asynchronously.
95 158
96All functions expecting a filehandle keep a copy of the filehandle 159All functions expecting a filehandle keep a copy of the filehandle
97internally until the request has finished. 160internally until the request has finished.
98 161
162All requests return objects of type L<IO::AIO::REQ> that allow further
163manipulation of those requests while they are in-flight.
164
99The pathnames you pass to these routines I<must> be absolute and 165The pathnames you pass to these routines I<must> be absolute and
100encoded in byte form. The reason for the former is that at the time the 166encoded in byte form. The reason for the former is that at the time the
101request is being executed, the current working directory could have 167request is being executed, the current working directory could have
102changed. Alternatively, you can make sure that you never change the 168changed. Alternatively, you can make sure that you never change the
103current working directory. 169current working directory.
108your pathnames to the locale (or other) encoding in effect in the user 174your pathnames to the locale (or other) encoding in effect in the user
109environment, d) use Glib::filename_from_unicode on unicode filenames or e) 175environment, d) use Glib::filename_from_unicode on unicode filenames or e)
110use something else. 176use something else.
111 177
112=over 4 178=over 4
179
180=item aioreq_pri $pri
181
182Sets the priority for the next aio request. The default priority
183is C<0>, the minimum and maximum priorities are C<-4> and C<4>,
184respectively. Requests with higher priority will be serviced first.
185
186The priority will be reset to C<0> after each call to one of the C<aio_>
187functions.
188
189Example: open a file with low priority, then read something from it with
190higher priority so the read request is serviced before other low priority
191open requests (potentially spamming the cache):
192
193 aioreq_pri -3;
194 aio_open ..., sub {
195 return unless $_[0];
196
197 aioreq_pri -2;
198 aio_read $_[0], ..., sub {
199 ...
200 };
201 };
202
203=item aioreq_nice $pri_adjust
204
205Similar to C<aioreq_pri>, but subtracts the given value from the current
206priority, so effects are cumulative.
113 207
114=item aio_open $pathname, $flags, $mode, $callback->($fh) 208=item aio_open $pathname, $flags, $mode, $callback->($fh)
115 209
116Asynchronously open or create a file and call the callback with a newly 210Asynchronously open or create a file and call the callback with a newly
117created filehandle for the file. 211created filehandle for the file.
170 print "read $_[0] bytes: <$buffer>\n"; 264 print "read $_[0] bytes: <$buffer>\n";
171 }; 265 };
172 266
173=item aio_move $srcpath, $dstpath, $callback->($status) 267=item aio_move $srcpath, $dstpath, $callback->($status)
174 268
175[EXPERIMENTAL]
176
177Try to move the I<file> (directories not supported as either source or destination) 269Try to move the I<file> (directories not supported as either source or
178from C<$srcpath> to C<$dstpath> and call the callback with the C<0> (error) or C<-1> ok. 270destination) from C<$srcpath> to C<$dstpath> and call the callback with
271the C<0> (error) or C<-1> ok.
179 272
180This is a composite request that tries to rename(2) the file first. If 273This is a composite request that tries to rename(2) the file first. If
181rename files with C<EXDEV>, it creates the destination file with mode 0200 274rename files with C<EXDEV>, it creates the destination file with mode 0200
182and copies the contents of the source file into it using C<aio_sendfile>, 275and copies the contents of the source file into it using C<aio_sendfile>,
183followed by restoring atime, mtime, access mode and uid/gid, in that 276followed by restoring atime, mtime, access mode and uid/gid, in that
190=cut 283=cut
191 284
192sub aio_move($$$) { 285sub aio_move($$$) {
193 my ($src, $dst, $cb) = @_; 286 my ($src, $dst, $cb) = @_;
194 287
288 my $grp = aio_group $cb;
289
195 aio_rename $src, $dst, sub { 290 add $grp aio_rename $src, $dst, sub {
196 if ($_[0] && $! == Errno::EXDEV) { 291 if ($_[0] && $! == EXDEV) {
197 aio_open $src, O_RDONLY, 0, sub { 292 add $grp aio_open $src, O_RDONLY, 0, sub {
198 if (my $src_fh = $_[0]) { 293 if (my $src_fh = $_[0]) {
199 my @stat = stat $src_fh; 294 my @stat = stat $src_fh;
200 295
201 aio_open $dst, O_WRONLY, 0200, sub { 296 add $grp aio_open $dst, O_WRONLY, 0200, sub {
202 if (my $dst_fh = $_[0]) { 297 if (my $dst_fh = $_[0]) {
203 aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub { 298 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
204 close $src_fh; 299 close $src_fh;
205 300
206 if ($_[0] == $stat[7]) { 301 if ($_[0] == $stat[7]) {
207 utime $stat[8], $stat[9], $dst; 302 utime $stat[8], $stat[9], $dst;
208 chmod $stat[2] & 07777, $dst_fh; 303 chmod $stat[2] & 07777, $dst_fh;
209 chown $stat[4], $stat[5], $dst_fh; 304 chown $stat[4], $stat[5], $dst_fh;
210 close $dst_fh; 305 close $dst_fh;
211 306
212 aio_unlink $src, sub { 307 add $grp aio_unlink $src, sub {
213 $cb->($_[0]); 308 $grp->result ($_[0]);
214 }; 309 };
215 } else { 310 } else {
216 my $errno = $!; 311 my $errno = $!;
217 aio_unlink $dst, sub { 312 add $grp aio_unlink $dst, sub {
218 $! = $errno; 313 $! = $errno;
219 $cb->(-1); 314 $grp->result (-1);
220 }; 315 };
221 } 316 }
222 }; 317 };
223 } else { 318 } else {
224 $cb->(-1); 319 $grp->result (-1);
225 } 320 }
226 }, 321 },
227 322
228 } else { 323 } else {
229 $cb->(-1); 324 $grp->result (-1);
230 } 325 }
231 }; 326 };
232 } else { 327 } else {
233 $cb->($_[0]); 328 $grp->result ($_[0]);
234 } 329 }
235 }; 330 };
331
332 $grp
236} 333}
237 334
238=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 335=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
239 336
240Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts 337Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
328The callback a single argument which is either C<undef> or an array-ref 425The callback a single argument which is either C<undef> or an array-ref
329with the filenames. 426with the filenames.
330 427
331=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 428=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
332 429
333Scans a directory (similar to C<aio_readdir>) and tries to separate the 430Scans a directory (similar to C<aio_readdir>) but additionally tries to
334entries of directory C<$path> into two sets of names, ones you can recurse 431separate the entries of directory C<$path> into two sets of names, ones
335into (directories), and ones you cannot recurse into (everything else). 432you can recurse into (directories or links to them), and ones you cannot
433recurse into (everything else).
336 434
337C<aio_scandir> is a composite request that consists of many 435C<aio_scandir> is a composite request that creates of many sub requests_
338aio-primitives. C<$maxreq> specifies the maximum number of outstanding 436C<$maxreq> specifies the maximum number of outstanding aio requests that
339aio requests that this function generates. If it is C<< <= 0 >>, then a 437this function generates. If it is C<< <= 0 >>, then a suitable default
340suitable default will be chosen (currently 8). 438will be chosen (currently 6).
341 439
342On error, the callback is called without arguments, otherwise it receives 440On error, the callback is called without arguments, otherwise it receives
343two array-refs with path-relative entry names. 441two array-refs with path-relative entry names.
344 442
345Example: 443Example:
353Implementation notes. 451Implementation notes.
354 452
355The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can. 453The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
356 454
357After reading the directory, the modification time, size etc. of the 455After reading the directory, the modification time, size etc. of the
358directory before and after the readdir is checked, and if they match, the 456directory before and after the readdir is checked, and if they match (and
359link count will be used to decide how many entries are directories (if 457isn't the current time), the link count will be used to decide how many
360>= 2). Otherwise, no knowledge of the number of subdirectories will be 458entries are directories (if >= 2). Otherwise, no knowledge of the number
361assumed. 459of subdirectories will be assumed.
362 460
363Then entires will be sorted into likely directories (everything without a 461Then entries will be sorted into likely directories (everything without
364non-initial dot) and likely non-directories (everything else). Then every 462a non-initial dot currently) and likely non-directories (everything
365entry + C</.> will be C<stat>'ed, likely directories first. This is often 463else). Then every entry plus an appended C</.> will be C<stat>'ed,
464likely directories first. If that succeeds, it assumes that the entry
465is a directory or a symlink to directory (which will be checked
466seperately). This is often faster than stat'ing the entry itself because
366faster because filesystems might detect the type of the entry without 467filesystems might detect the type of the entry without reading the inode
367reading the inode data (e.g. ext2fs filetype feature). If that succeeds, 468data (e.g. ext2fs filetype feature).
368it assumes that the entry is a directory or a symlink to directory (which
369will be checked seperately).
370 469
371If the known number of directories has been reached, the rest of the 470If the known number of directories (link count - 2) has been reached, the
372entries is assumed to be non-directories. 471rest of the entries is assumed to be non-directories.
472
473This only works with certainty on POSIX (= UNIX) filesystems, which
474fortunately are the vast majority of filesystems around.
475
476It will also likely work on non-POSIX filesystems with reduced efficiency
477as those tend to return 0 or 1 as link counts, which disables the
478directory counting heuristic.
373 479
374=cut 480=cut
375 481
376sub aio_scandir($$$) { 482sub aio_scandir($$$) {
377 my ($path, $maxreq, $cb) = @_; 483 my ($path, $maxreq, $cb) = @_;
378 484
485 my $grp = aio_group $cb;
486
379 $maxreq = 8 if $maxreq <= 0; 487 $maxreq = 6 if $maxreq <= 0;
380 488
381 # stat once 489 # stat once
382 aio_stat $path, sub { 490 add $grp aio_stat $path, sub {
383 return $cb->() if $_[0]; 491 return $grp->result () if $_[0];
492 my $now = time;
384 my $hash1 = join ":", (stat _)[0,1,3,7,9]; 493 my $hash1 = join ":", (stat _)[0,1,3,7,9];
385 494
386 # read the directory entries 495 # read the directory entries
387 aio_readdir $path, sub { 496 add $grp aio_readdir $path, sub {
388 my $entries = shift 497 my $entries = shift
389 or return $cb->(); 498 or return $grp->result ();
390 499
391 # stat the dir another time 500 # stat the dir another time
392 aio_stat $path, sub { 501 add $grp aio_stat $path, sub {
393 my $hash2 = join ":", (stat _)[0,1,3,7,9]; 502 my $hash2 = join ":", (stat _)[0,1,3,7,9];
394 503
395 my $ndirs; 504 my $ndirs;
396 505
397 # take the slow route if anything looks fishy 506 # take the slow route if anything looks fishy
398 if ($hash1 ne $hash2) { 507 if ($hash1 ne $hash2 or (stat _)[9] == $now) {
399 $ndirs = -1; 508 $ndirs = -1;
400 } else { 509 } else {
401 # if nlink == 2, we are finished 510 # if nlink == 2, we are finished
402 # on non-posix-fs's, we rely on nlink < 2 511 # on non-posix-fs's, we rely on nlink < 2
403 $ndirs = (stat _)[3] - 2 512 $ndirs = (stat _)[3] - 2
404 or return $cb->([], $entries); 513 or return $grp->result ([], $entries);
405 } 514 }
406 515
407 # sort into likely dirs and likely nondirs 516 # sort into likely dirs and likely nondirs
408 # dirs == files without ".", short entries first 517 # dirs == files without ".", short entries first
409 $entries = [map $_->[0], 518 $entries = [map $_->[0],
414 my (@dirs, @nondirs); 523 my (@dirs, @nondirs);
415 524
416 my ($statcb, $schedcb); 525 my ($statcb, $schedcb);
417 my $nreq = 0; 526 my $nreq = 0;
418 527
528 my $statgrp = add $grp aio_group;
529
419 $schedcb = sub { 530 $schedcb = sub {
420 if (@$entries) { 531 if (@$entries) {
421 if ($nreq < $maxreq) { 532 if ($nreq < $maxreq) {
422 my $ent = pop @$entries; 533 my $ent = pop @$entries;
423 $nreq++; 534 $nreq++;
424 aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) }; 535 add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
425 } 536 }
426 } elsif (!$nreq) { 537 } elsif (!$nreq) {
427 # finished 538 # finished
539 $statgrp->cancel;
428 undef $statcb; 540 undef $statcb;
429 undef $schedcb; 541 undef $schedcb;
430 $cb->(\@dirs, \@nondirs) if $cb; 542 $grp->result (\@dirs, \@nondirs);
431 undef $cb;
432 } 543 }
433 }; 544 };
434 $statcb = sub { 545 $statcb = sub {
435 my ($status, $entry) = @_; 546 my ($status, $entry) = @_;
436 547
438 $nreq--; 549 $nreq--;
439 push @nondirs, $entry; 550 push @nondirs, $entry;
440 &$schedcb; 551 &$schedcb;
441 } else { 552 } else {
442 # need to check for real directory 553 # need to check for real directory
443 aio_lstat "$path/$entry", sub { 554 add $grp aio_lstat "$path/$entry", sub {
444 $nreq--; 555 $nreq--;
445 556
446 if (-d _) { 557 if (-d _) {
447 push @dirs, $entry; 558 push @dirs, $entry;
448 559
461 572
462 &$schedcb while @$entries && $nreq < $maxreq; 573 &$schedcb while @$entries && $nreq < $maxreq;
463 }; 574 };
464 }; 575 };
465 }; 576 };
577
578 $grp
466} 579}
467 580
468=item aio_fsync $fh, $callback->($status) 581=item aio_fsync $fh, $callback->($status)
469 582
470Asynchronously call fsync on the given filehandle and call the callback 583Asynchronously call fsync on the given filehandle and call the callback
475Asynchronously call fdatasync on the given filehandle and call the 588Asynchronously call fdatasync on the given filehandle and call the
476callback with the fdatasync result code. 589callback with the fdatasync result code.
477 590
478If this call isn't available because your OS lacks it or it couldn't be 591If this call isn't available because your OS lacks it or it couldn't be
479detected, it will be emulated by calling C<fsync> instead. 592detected, it will be emulated by calling C<fsync> instead.
593
594=item aio_group $callback->(...)
595
596[EXPERIMENTAL]
597
598This is a very special aio request: Instead of doing something, it is a
599container for other aio requests, which is useful if you want to bundle
600many requests into a single, composite, request with a definite callback
601and the ability to cancel the whole request with its subrequests.
602
603Returns an object of class L<IO::AIO::GRP>. See its documentation below
604for more info.
605
606Example:
607
608 my $grp = aio_group sub {
609 print "all stats done\n";
610 };
611
612 add $grp
613 (aio_stat ...),
614 (aio_stat ...),
615 ...;
616
617=item aio_nop $callback->()
618
619This is a special request - it does nothing in itself and is only used for
620side effects, such as when you want to add a dummy request to a group so
621that finishing the requests in the group depends on executing the given
622code.
623
624While this request does nothing, it still goes through the execution
625phase and still requires a worker thread. Thus, the callback will not
626be executed immediately but only after other requests in the queue have
627entered their execution phase. This can be used to measure request
628latency.
629
630=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
631
632Mainly used for debugging and benchmarking, this aio request puts one of
633the request workers to sleep for the given time.
634
635While it is theoretically handy to have simple I/O scheduling requests
636like sleep and file handle readable/writable, the overhead this creates is
637immense (it blocks a thread for a long time) so do not use this function
638except to put your application under artificial I/O pressure.
639
640=back
641
642=head2 IO::AIO::REQ CLASS
643
644All non-aggregate C<aio_*> functions return an object of this class when
645called in non-void context.
646
647=over 4
648
649=item cancel $req
650
651Cancels the request, if possible. Has the effect of skipping execution
652when entering the B<execute> state and skipping calling the callback when
653entering the the B<result> state, but will leave the request otherwise
654untouched. That means that requests that currently execute will not be
655stopped and resources held by the request will not be freed prematurely.
656
657=item cb $req $callback->(...)
658
659Replace (or simply set) the callback registered to the request.
660
661=back
662
663=head2 IO::AIO::GRP CLASS
664
665This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
666objects of this class, too.
667
668A IO::AIO::GRP object is a special request that can contain multiple other
669aio requests.
670
671You create one by calling the C<aio_group> constructing function with a
672callback that will be called when all contained requests have entered the
673C<done> state:
674
675 my $grp = aio_group sub {
676 print "all requests are done\n";
677 };
678
679You add requests by calling the C<add> method with one or more
680C<IO::AIO::REQ> objects:
681
682 $grp->add (aio_unlink "...");
683
684 add $grp aio_stat "...", sub {
685 $_[0] or return $grp->result ("error");
686
687 # add another request dynamically, if first succeeded
688 add $grp aio_open "...", sub {
689 $grp->result ("ok");
690 };
691 };
692
693This makes it very easy to create composite requests (see the source of
694C<aio_move> for an application) that work and feel like simple requests.
695
696=over 4
697
698=item * The IO::AIO::GRP objects will be cleaned up during calls to
699C<IO::AIO::poll_cb>, just like any other request.
700
701=item * They can be canceled like any other request. Canceling will cancel not
702only the request itself, but also all requests it contains.
703
704=item * They can also can also be added to other IO::AIO::GRP objects.
705
706=item * You must not add requests to a group from within the group callback (or
707any later time).
708
709=item * This does not harmonise well with C<max_outstanding>, so best do
710not combine C<aio_group> with it. Groups and feeders are recommended for
711this kind of concurrency-limiting.
712
713=back
714
715Their lifetime, simplified, looks like this: when they are empty, they
716will finish very quickly. If they contain only requests that are in the
717C<done> state, they will also finish. Otherwise they will continue to
718exist.
719
720That means after creating a group you have some time to add requests. And
721in the callbacks of those requests, you can add further requests to the
722group. And only when all those requests have finished will the the group
723itself finish.
724
725=over 4
726
727=item add $grp ...
728
729=item $grp->add (...)
730
731Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
732be added, including other groups, as long as you do not create circular
733dependencies.
734
735Returns all its arguments.
736
737=item $grp->result (...)
738
739Set the result value(s) that will be passed to the group callback when all
740subrequests have finished. By default, no argument will be passed.
741
742=item feed $grp $callback->($grp)
743
744[VERY EXPERIMENTAL]
745
746Sets a feeder/generator on this group: every group can have an attached
747generator that generates requests if idle. The idea behind this is that,
748although you could just queue as many requests as you want in a group,
749this might starve other requests for a potentially long time. For
750example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
751requests, delaying any later requests for a long time.
752
753To avoid this, and allow incremental generation of requests, you can
754instead a group and set a feeder on it that generates those requests. The
755feed callback will be called whenever there are few enough (see C<limit>,
756below) requests active in the group itself and is expected to queue more
757requests.
758
759The feed callback can queue as many requests as it likes (i.e. C<add> does
760not impose any limits).
761
762If the feed does not queue more requests when called, it will be
763automatically removed from the group.
764
765If the feed limit is C<0>, it will be set to C<2> automatically.
766
767Example:
768
769 # stat all files in @files, but only ever use four aio requests concurrently:
770
771 my $grp = aio_group sub { print "finished\n" };
772 limit $grp 4;
773 feed $grp sub {
774 my $file = pop @files
775 or return;
776
777 add $grp aio_stat $file, sub { ... };
778 };
779
780=item limit $grp $num
781
782Sets the feeder limit for the group: The feeder will be called whenever
783the group contains less than this many requests.
784
785Setting the limit to C<0> will pause the feeding process.
480 786
481=back 787=back
482 788
483=head2 SUPPORT FUNCTIONS 789=head2 SUPPORT FUNCTIONS
484 790
542 IO::AIO::poll_wait, IO::AIO::poll_cb 848 IO::AIO::poll_wait, IO::AIO::poll_cb
543 if IO::AIO::nreqs; 849 if IO::AIO::nreqs;
544 850
545=item IO::AIO::min_parallel $nthreads 851=item IO::AIO::min_parallel $nthreads
546 852
547Set the minimum number of AIO threads to C<$nthreads>. The current default 853Set the minimum number of AIO threads to C<$nthreads>. The current
548is C<4>, which means four asynchronous operations can be done at one time 854default is C<8>, which means eight asynchronous operations can execute
549(the number of outstanding operations, however, is unlimited). 855concurrently at any one time (the number of outstanding requests,
856however, is unlimited).
550 857
551IO::AIO starts threads only on demand, when an AIO request is queued and 858IO::AIO starts threads only on demand, when an AIO request is queued and
552no free thread exists. 859no free thread exists.
553 860
554It is recommended to keep the number of threads low, as some Linux 861It is recommended to keep the number of threads relatively low, as some
555kernel versions will scale negatively with the number of threads (higher 862Linux kernel versions will scale negatively with the number of threads
556parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 863(higher parallelity => MUCH higher latency). With current Linux 2.6
557threads should be fine. 864versions, 4-32 threads should be fine.
558 865
559Under most circumstances you don't need to call this function, as the 866Under most circumstances you don't need to call this function, as the
560module selects a default that is suitable for low to moderate load. 867module selects a default that is suitable for low to moderate load.
561 868
562=item IO::AIO::max_parallel $nthreads 869=item IO::AIO::max_parallel $nthreads
573 880
574Under normal circumstances you don't need to call this function. 881Under normal circumstances you don't need to call this function.
575 882
576=item $oldnreqs = IO::AIO::max_outstanding $nreqs 883=item $oldnreqs = IO::AIO::max_outstanding $nreqs
577 884
885[DEPRECATED]
886
578Sets the maximum number of outstanding requests to C<$nreqs>. If you 887Sets the maximum number of outstanding requests to C<$nreqs>. If you
579try to queue up more than this number of requests, the caller will block until 888try to queue up more than this number of requests, the caller will block until
580some requests have been handled. 889some requests have been handled.
581 890
582The default is very large, so normally there is no practical limit. If you 891The default is very large, so normally there is no practical limit. If you
583queue up many requests in a loop it often improves speed if you set 892queue up many requests in a loop it often improves speed if you set
584this to a relatively low number, such as C<100>. 893this to a relatively low number, such as C<100>.
894
895This function does not work well together with C<aio_group>'s, and their
896feeder interface is better suited to limiting concurrency, so do not use
897this function.
585 898
586Under normal circumstances you don't need to call this function. 899Under normal circumstances you don't need to call this function.
587 900
588=back 901=back
589 902
603 or return undef; 916 or return undef;
604 917
605 *$sym 918 *$sym
606} 919}
607 920
608min_parallel 4; 921min_parallel 8;
609 922
610END { 923END {
611 max_parallel 0; 924 max_parallel 0;
612} 925}
613 926
6141; 9271;
615 928
616=head2 FORK BEHAVIOUR 929=head2 FORK BEHAVIOUR
617 930
931This module should do "the right thing" when the process using it forks:
932
618Before the fork, IO::AIO enters a quiescent state where no requests 933Before the fork, IO::AIO enters a quiescent state where no requests
619can be added in other threads and no results will be processed. After 934can be added in other threads and no results will be processed. After
620the fork the parent simply leaves the quiescent state and continues 935the fork the parent simply leaves the quiescent state and continues
621request/result processing, while the child clears the request/result 936request/result processing, while the child frees the request/result queue
622queue (so the requests started before the fork will only be handled in 937(so that the requests started before the fork will only be handled in the
623the parent). Threats will be started on demand until the limit ste in the 938parent). Threads will be started on demand until the limit set in the
624parent process has been reached again. 939parent process has been reached again.
625 940
941In short: the parent will, after a short pause, continue as if fork had
942not been called, while the child will act as if IO::AIO has not been used
943yet.
944
945=head2 MEMORY USAGE
946
947Per-request usage:
948
949Each aio request uses - depending on your architecture - around 100-200
950bytes of memory. In addition, stat requests need a stat buffer (possibly
951a few hundred bytes), readdir requires a result buffer and so on. Perl
952scalars and other data passed into aio requests will also be locked and
953will consume memory till the request has entered the done state.
954
955This is now awfully much, so queuing lots of requests is not usually a
956problem.
957
958Per-thread usage:
959
960In the execution phase, some aio requests require more memory for
961temporary buffers, and each thread requires a stack and other data
962structures (usually around 16k-128k, depending on the OS).
963
964=head1 KNOWN BUGS
965
966Known bugs will be fixed in the next release.
967
626=head1 SEE ALSO 968=head1 SEE ALSO
627 969
628L<Coro>, L<Linux::AIO>. 970L<Coro::AIO>.
629 971
630=head1 AUTHOR 972=head1 AUTHOR
631 973
632 Marc Lehmann <schmorp@schmorp.de> 974 Marc Lehmann <schmorp@schmorp.de>
633 http://home.schmorp.de/ 975 http://home.schmorp.de/

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