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Revision 1.84 by root, Sat Oct 28 00:17:30 2006 UTC vs.
Revision 1.96 by root, Fri Dec 22 04:05:50 2006 UTC

… …
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use IO::AIO; 7 use IO::AIO;
8 8
9 aio_open "/etc/passwd", O_RDONLY, 0, sub { 9 aio_open "/etc/passwd", O_RDONLY, 0, sub {
10 my ($fh) = @_; 10 my $fh = shift
11 or die "/etc/passwd: $!";
11 ... 12 ...
12 }; 13 };
13 14
14 aio_unlink "/tmp/file", sub { }; 15 aio_unlink "/tmp/file", sub { };
15 16
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50 51
51=head1 DESCRIPTION 52=head1 DESCRIPTION
52 53
53This module implements asynchronous I/O using whatever means your 54This module implements asynchronous I/O using whatever means your
54operating system supports. 55operating system supports.
56
57Asynchronous means that operations that can normally block your program
58(e.g. reading from disk) will be done asynchronously: the operation
59will still block, but you can do something else in the meantime. This
60is extremely useful for programs that need to stay interactive even
61when doing heavy I/O (GUI programs, high performance network servers
62etc.), but can also be used to easily do operations in parallel that are
63normally done sequentially, e.g. stat'ing many files, which is much faster
64on a RAID volume or over NFS when you do a number of stat operations
65concurrently.
66
67While most of this works on all types of file descriptors (for example
68sockets), using these functions on file descriptors that support
69nonblocking operation (again, sockets, pipes etc.) is very inefficient or
70might not work (aio_read fails on sockets/pipes/fifos). Use an event loop
71for that (such as the L<Event|Event> module): IO::AIO will naturally fit
72into such an event loop itself.
55 73
56In this version, a number of threads are started that execute your 74In this version, a number of threads are started that execute your
57requests and signal their completion. You don't need thread support 75requests and signal their completion. You don't need thread support
58in perl, and the threads created by this module will not be visible 76in perl, and the threads created by this module will not be visible
59to perl. In the future, this module might make use of the native aio 77to perl. In the future, this module might make use of the native aio
60functions available on many operating systems. However, they are often 78functions available on many operating systems. However, they are often
61not well-supported or restricted (Linux doesn't allow them on normal 79not well-supported or restricted (GNU/Linux doesn't allow them on normal
62files currently, for example), and they would only support aio_read and 80files currently, for example), and they would only support aio_read and
63aio_write, so the remaining functionality would have to be implemented 81aio_write, so the remaining functionality would have to be implemented
64using threads anyway. 82using threads anyway.
65 83
66Although the module will work with in the presence of other (Perl-) 84Although the module will work with in the presence of other (Perl-)
67threads, it is currently not reentrant in any way, so use appropriate 85threads, it is currently not reentrant in any way, so use appropriate
68locking yourself, always call C<poll_cb> from within the same thread, or 86locking yourself, always call C<poll_cb> from within the same thread, or
69never call C<poll_cb> (or other C<aio_> functions) recursively. 87never call C<poll_cb> (or other C<aio_> functions) recursively.
70 88
89=head2 EXAMPLE
90
91This is a simple example that uses the Event module and loads
92F</etc/passwd> asynchronously:
93
94 use Fcntl;
95 use Event;
96 use IO::AIO;
97
98 # register the IO::AIO callback with Event
99 Event->io (fd => IO::AIO::poll_fileno,
100 poll => 'r',
101 cb => \&IO::AIO::poll_cb);
102
103 # queue the request to open /etc/passwd
104 aio_open "/etc/passwd", O_RDONLY, 0, sub {
105 my $fh = shift
106 or die "error while opening: $!";
107
108 # stat'ing filehandles is generally non-blocking
109 my $size = -s $fh;
110
111 # queue a request to read the file
112 my $contents;
113 aio_read $fh, 0, $size, $contents, 0, sub {
114 $_[0] == $size
115 or die "short read: $!";
116
117 close $fh;
118
119 # file contents now in $contents
120 print $contents;
121
122 # exit event loop and program
123 Event::unloop;
124 };
125 };
126
127 # possibly queue up other requests, or open GUI windows,
128 # check for sockets etc. etc.
129
130 # process events as long as there are some:
131 Event::loop;
132
71=head1 REQUEST ANATOMY AND LIFETIME 133=head1 REQUEST ANATOMY AND LIFETIME
72 134
73Every C<aio_*> function creates a request. which is a C data structure not 135Every C<aio_*> function creates a request. which is a C data structure not
74directly visible to Perl. 136directly visible to Perl.
75 137
… …
116Request has reached the end of its lifetime and holds no resources anymore 178Request 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 179(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 180aio request is severed and calling its methods will either do nothing or
119result in a runtime error). 181result in a runtime error).
120 182
183=back
184
121=cut 185=cut
122 186
123package IO::AIO; 187package IO::AIO;
124 188
125no warnings; 189no warnings;
126use strict 'vars'; 190use strict 'vars';
127 191
128use base 'Exporter'; 192use base 'Exporter';
129 193
130BEGIN { 194BEGIN {
131 our $VERSION = '2.0'; 195 our $VERSION = '2.21';
132 196
133 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat 197 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
134 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink 198 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
135 aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move 199 aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
136 aio_copy aio_group aio_nop aio_mknod); 200 aio_move aio_copy aio_group aio_nop aio_mknod);
137 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice)); 201 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
138 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush 202 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
139 min_parallel max_parallel nreqs nready npending); 203 min_parallel max_parallel max_idle
204 nreqs nready npending nthreads
205 max_poll_time max_poll_reqs);
140 206
141 @IO::AIO::GRP::ISA = 'IO::AIO::REQ'; 207 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
142 208
143 require XSLoader; 209 require XSLoader;
144 XSLoader::load ("IO::AIO", $VERSION); 210 XSLoader::load ("IO::AIO", $VERSION);
145} 211}
146 212
147=head1 FUNCTIONS 213=head1 FUNCTIONS
148 214
149=head2 AIO FUNCTIONS 215=head2 AIO REQUEST FUNCTIONS
150 216
151All the C<aio_*> calls are more or less thin wrappers around the syscall 217All the C<aio_*> calls are more or less thin wrappers around the syscall
152with the same name (sans C<aio_>). The arguments are similar or identical, 218with the same name (sans C<aio_>). The arguments are similar or identical,
153and they all accept an additional (and optional) C<$callback> argument 219and they all accept an additional (and optional) C<$callback> argument
154which must be a code reference. This code reference will get called with 220which must be a code reference. This code reference will get called with
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157syscall has been executed asynchronously. 223syscall has been executed asynchronously.
158 224
159All functions expecting a filehandle keep a copy of the filehandle 225All functions expecting a filehandle keep a copy of the filehandle
160internally until the request has finished. 226internally until the request has finished.
161 227
162All requests return objects of type L<IO::AIO::REQ> that allow further 228All functions return request objects of type L<IO::AIO::REQ> that allow
163manipulation of those requests while they are in-flight. 229further manipulation of those requests while they are in-flight.
164 230
165The pathnames you pass to these routines I<must> be absolute and 231The pathnames you pass to these routines I<must> be absolute and
166encoded in byte form. The reason for the former is that at the time the 232encoded as octets. The reason for the former is that at the time the
167request is being executed, the current working directory could have 233request is being executed, the current working directory could have
168changed. Alternatively, you can make sure that you never change the 234changed. Alternatively, you can make sure that you never change the
169current working directory. 235current working directory anywhere in the program and then use relative
236paths.
170 237
171To encode pathnames to byte form, either make sure you either: a) 238To encode pathnames as octets, either make sure you either: a) always pass
172always pass in filenames you got from outside (command line, readdir 239in filenames you got from outside (command line, readdir etc.) without
173etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode 240tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
174your pathnames to the locale (or other) encoding in effect in the user 241your pathnames to the locale (or other) encoding in effect in the user
175environment, d) use Glib::filename_from_unicode on unicode filenames or e) 242environment, d) use Glib::filename_from_unicode on unicode filenames or e)
176use something else. 243use something else to ensure your scalar has the correct contents.
244
245This works, btw. independent of the internal UTF-8 bit, which IO::AIO
246handles correctly wether it is set or not.
177 247
178=over 4 248=over 4
179 249
180=item $prev_pri = aioreq_pri [$pri] 250=item $prev_pri = aioreq_pri [$pri]
181 251
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204 }; 274 };
205 275
206=item aioreq_nice $pri_adjust 276=item aioreq_nice $pri_adjust
207 277
208Similar to C<aioreq_pri>, but subtracts the given value from the current 278Similar to C<aioreq_pri>, but subtracts the given value from the current
209priority, so effects are cumulative. 279priority, so the effect is cumulative.
210 280
211=item aio_open $pathname, $flags, $mode, $callback->($fh) 281=item aio_open $pathname, $flags, $mode, $callback->($fh)
212 282
213Asynchronously open or create a file and call the callback with a newly 283Asynchronously open or create a file and call the callback with a newly
214created filehandle for the file. 284created filehandle for the file.
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331Asynchronously unlink (delete) a file and call the callback with the 401Asynchronously unlink (delete) a file and call the callback with the
332result code. 402result code.
333 403
334=item aio_mknod $path, $mode, $dev, $callback->($status) 404=item aio_mknod $path, $mode, $dev, $callback->($status)
335 405
406[EXPERIMENTAL]
407
336Asynchronously create a device node (or fifo). See mknod(2). 408Asynchronously create a device node (or fifo). See mknod(2).
337 409
338The only portable (POSIX) way of calling this function is: 410The only (POSIX-) portable way of calling this function is:
339 411
340 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 412 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
341 413
342=item aio_link $srcpath, $dstpath, $callback->($status) 414=item aio_link $srcpath, $dstpath, $callback->($status)
343 415
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346 418
347=item aio_symlink $srcpath, $dstpath, $callback->($status) 419=item aio_symlink $srcpath, $dstpath, $callback->($status)
348 420
349Asynchronously create a new symbolic link to the existing object at C<$srcpath> at 421Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
350the path C<$dstpath> and call the callback with the result code. 422the path C<$dstpath> and call the callback with the result code.
423
424=item aio_readlink $path, $callback->($link)
425
426Asynchronously read the symlink specified by C<$path> and pass it to
427the callback. If an error occurs, nothing or undef gets passed to the
428callback.
351 429
352=item aio_rename $srcpath, $dstpath, $callback->($status) 430=item aio_rename $srcpath, $dstpath, $callback->($status)
353 431
354Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as 432Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
355rename(2) and call the callback with the result code. 433rename(2) and call the callback with the result code.
… …
384errors are being ignored. 462errors are being ignored.
385 463
386=cut 464=cut
387 465
388sub aio_copy($$;$) { 466sub aio_copy($$;$) {
467 aio_block {
389 my ($src, $dst, $cb) = @_; 468 my ($src, $dst, $cb) = @_;
390 469
391 my $pri = aioreq_pri; 470 my $pri = aioreq_pri;
392 my $grp = aio_group $cb; 471 my $grp = aio_group $cb;
393 472
394 aioreq_pri $pri; 473 aioreq_pri $pri;
395 add $grp aio_open $src, O_RDONLY, 0, sub { 474 add $grp aio_open $src, O_RDONLY, 0, sub {
396 if (my $src_fh = $_[0]) { 475 if (my $src_fh = $_[0]) {
397 my @stat = stat $src_fh; 476 my @stat = stat $src_fh;
398 477
399 aioreq_pri $pri; 478 aioreq_pri $pri;
400 add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub { 479 add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
401 if (my $dst_fh = $_[0]) { 480 if (my $dst_fh = $_[0]) {
402 aioreq_pri $pri; 481 aioreq_pri $pri;
403 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub { 482 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
404 if ($_[0] == $stat[7]) { 483 if ($_[0] == $stat[7]) {
405 $grp->result (0); 484 $grp->result (0);
406 close $src_fh; 485 close $src_fh;
407 486
408 # those should not normally block. should. should. 487 # those should not normally block. should. should.
409 utime $stat[8], $stat[9], $dst; 488 utime $stat[8], $stat[9], $dst;
410 chmod $stat[2] & 07777, $dst_fh; 489 chmod $stat[2] & 07777, $dst_fh;
411 chown $stat[4], $stat[5], $dst_fh; 490 chown $stat[4], $stat[5], $dst_fh;
412 close $dst_fh; 491 close $dst_fh;
413 } else { 492 } else {
414 $grp->result (-1); 493 $grp->result (-1);
415 close $src_fh; 494 close $src_fh;
416 close $dst_fh; 495 close $dst_fh;
417 496
418 aioreq $pri; 497 aioreq $pri;
419 add $grp aio_unlink $dst; 498 add $grp aio_unlink $dst;
499 }
420 } 500 };
501 } else {
502 $grp->result (-1);
421 }; 503 }
422 } else {
423 $grp->result (-1);
424 } 504 },
505
506 } else {
507 $grp->result (-1);
425 }, 508 }
426
427 } else {
428 $grp->result (-1);
429 } 509 };
510
511 $grp
430 }; 512 }
431
432 $grp
433} 513}
434 514
435=item aio_move $srcpath, $dstpath, $callback->($status) 515=item aio_move $srcpath, $dstpath, $callback->($status)
436 516
437Try to move the I<file> (directories not supported as either source or 517Try to move the I<file> (directories not supported as either source or
… …
443that is successful, unlinking the C<$srcpath>. 523that is successful, unlinking the C<$srcpath>.
444 524
445=cut 525=cut
446 526
447sub aio_move($$;$) { 527sub aio_move($$;$) {
528 aio_block {
448 my ($src, $dst, $cb) = @_; 529 my ($src, $dst, $cb) = @_;
449 530
450 my $pri = aioreq_pri; 531 my $pri = aioreq_pri;
451 my $grp = aio_group $cb; 532 my $grp = aio_group $cb;
452 533
453 aioreq_pri $pri; 534 aioreq_pri $pri;
454 add $grp aio_rename $src, $dst, sub { 535 add $grp aio_rename $src, $dst, sub {
455 if ($_[0] && $! == EXDEV) { 536 if ($_[0] && $! == EXDEV) {
456 aioreq_pri $pri; 537 aioreq_pri $pri;
457 add $grp aio_copy $src, $dst, sub { 538 add $grp aio_copy $src, $dst, sub {
539 $grp->result ($_[0]);
540
541 if (!$_[0]) {
542 aioreq_pri $pri;
543 add $grp aio_unlink $src;
544 }
545 };
546 } else {
458 $grp->result ($_[0]); 547 $grp->result ($_[0]);
459
460 if (!$_[0]) {
461 aioreq_pri $pri;
462 add $grp aio_unlink $src;
463 }
464 }; 548 }
465 } else {
466 $grp->result ($_[0]);
467 } 549 };
550
551 $grp
468 }; 552 }
469
470 $grp
471} 553}
472 554
473=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 555=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
474 556
475Scans a directory (similar to C<aio_readdir>) but additionally tries to 557Scans a directory (similar to C<aio_readdir>) but additionally tries to
… …
523directory counting heuristic. 605directory counting heuristic.
524 606
525=cut 607=cut
526 608
527sub aio_scandir($$$) { 609sub aio_scandir($$$) {
610 aio_block {
528 my ($path, $maxreq, $cb) = @_; 611 my ($path, $maxreq, $cb) = @_;
529 612
530 my $pri = aioreq_pri; 613 my $pri = aioreq_pri;
531 614
532 my $grp = aio_group $cb; 615 my $grp = aio_group $cb;
533 616
534 $maxreq = 4 if $maxreq <= 0; 617 $maxreq = 4 if $maxreq <= 0;
535 618
536 # stat once 619 # stat once
537 aioreq_pri $pri;
538 add $grp aio_stat $path, sub {
539 return $grp->result () if $_[0];
540 my $now = time;
541 my $hash1 = join ":", (stat _)[0,1,3,7,9];
542
543 # read the directory entries
544 aioreq_pri $pri; 620 aioreq_pri $pri;
545 add $grp aio_readdir $path, sub { 621 add $grp aio_stat $path, sub {
546 my $entries = shift
547 or return $grp->result (); 622 return $grp->result () if $_[0];
623 my $now = time;
624 my $hash1 = join ":", (stat _)[0,1,3,7,9];
548 625
549 # stat the dir another time 626 # read the directory entries
550 aioreq_pri $pri; 627 aioreq_pri $pri;
628 add $grp aio_readdir $path, sub {
629 my $entries = shift
630 or return $grp->result ();
631
632 # stat the dir another time
633 aioreq_pri $pri;
551 add $grp aio_stat $path, sub { 634 add $grp aio_stat $path, sub {
552 my $hash2 = join ":", (stat _)[0,1,3,7,9]; 635 my $hash2 = join ":", (stat _)[0,1,3,7,9];
553 636
554 my $ndirs; 637 my $ndirs;
555 638
556 # take the slow route if anything looks fishy 639 # take the slow route if anything looks fishy
557 if ($hash1 ne $hash2 or (stat _)[9] == $now) { 640 if ($hash1 ne $hash2 or (stat _)[9] == $now) {
558 $ndirs = -1; 641 $ndirs = -1;
559 } else { 642 } else {
560 # if nlink == 2, we are finished 643 # if nlink == 2, we are finished
561 # on non-posix-fs's, we rely on nlink < 2 644 # on non-posix-fs's, we rely on nlink < 2
562 $ndirs = (stat _)[3] - 2 645 $ndirs = (stat _)[3] - 2
563 or return $grp->result ([], $entries); 646 or return $grp->result ([], $entries);
564 } 647 }
565 648
566 # sort into likely dirs and likely nondirs 649 # sort into likely dirs and likely nondirs
567 # dirs == files without ".", short entries first 650 # dirs == files without ".", short entries first
568 $entries = [map $_->[0], 651 $entries = [map $_->[0],
569 sort { $b->[1] cmp $a->[1] } 652 sort { $b->[1] cmp $a->[1] }
570 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length], 653 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
571 @$entries]; 654 @$entries];
572 655
573 my (@dirs, @nondirs); 656 my (@dirs, @nondirs);
574 657
575 my $statgrp = add $grp aio_group sub { 658 my $statgrp = add $grp aio_group sub {
576 $grp->result (\@dirs, \@nondirs); 659 $grp->result (\@dirs, \@nondirs);
577 }; 660 };
578 661
579 limit $statgrp $maxreq; 662 limit $statgrp $maxreq;
580 feed $statgrp sub { 663 feed $statgrp sub {
581 return unless @$entries; 664 return unless @$entries;
582 my $entry = pop @$entries; 665 my $entry = pop @$entries;
583 666
584 aioreq_pri $pri; 667 aioreq_pri $pri;
585 add $statgrp aio_stat "$path/$entry/.", sub { 668 add $statgrp aio_stat "$path/$entry/.", sub {
586 if ($_[0] < 0) { 669 if ($_[0] < 0) {
587 push @nondirs, $entry; 670 push @nondirs, $entry;
588 } else { 671 } else {
589 # need to check for real directory 672 # need to check for real directory
590 aioreq_pri $pri; 673 aioreq_pri $pri;
591 add $statgrp aio_lstat "$path/$entry", sub { 674 add $statgrp aio_lstat "$path/$entry", sub {
592 if (-d _) { 675 if (-d _) {
593 push @dirs, $entry; 676 push @dirs, $entry;
594 677
595 unless (--$ndirs) { 678 unless (--$ndirs) {
596 push @nondirs, @$entries; 679 push @nondirs, @$entries;
597 feed $statgrp; 680 feed $statgrp;
681 }
682 } else {
683 push @nondirs, $entry;
598 } 684 }
599 } else {
600 push @nondirs, $entry;
601 } 685 }
602 } 686 }
603 } 687 };
604 }; 688 };
605 }; 689 };
606 }; 690 };
607 }; 691 };
692
693 $grp
608 }; 694 }
609
610 $grp
611} 695}
612 696
613=item aio_fsync $fh, $callback->($status) 697=item aio_fsync $fh, $callback->($status)
614 698
615Asynchronously call fsync on the given filehandle and call the callback 699Asynchronously call fsync on the given filehandle and call the callback
… …
829 913
830=back 914=back
831 915
832=head2 SUPPORT FUNCTIONS 916=head2 SUPPORT FUNCTIONS
833 917
918=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
919
834=over 4 920=over 4
835 921
836=item $fileno = IO::AIO::poll_fileno 922=item $fileno = IO::AIO::poll_fileno
837 923
838Return the I<request result pipe file descriptor>. This filehandle must be 924Return the I<request result pipe file descriptor>. This filehandle must be
… …
842 928
843See C<poll_cb> for an example. 929See C<poll_cb> for an example.
844 930
845=item IO::AIO::poll_cb 931=item IO::AIO::poll_cb
846 932
847Process all outstanding events on the result pipe. You have to call this 933Process some outstanding events on the result pipe. You have to call this
848regularly. Returns the number of events processed. Returns immediately 934regularly. Returns the number of events processed. Returns immediately
849when no events are outstanding. 935when no events are outstanding. The amount of events processed depends on
936the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
850 937
851If not all requests were processed for whatever reason, the filehandle 938If not all requests were processed for whatever reason, the filehandle
852will still be ready when C<poll_cb> returns. 939will still be ready when C<poll_cb> returns.
853 940
854Example: Install an Event watcher that automatically calls 941Example: Install an Event watcher that automatically calls
… …
856 943
857 Event->io (fd => IO::AIO::poll_fileno, 944 Event->io (fd => IO::AIO::poll_fileno,
858 poll => 'r', async => 1, 945 poll => 'r', async => 1,
859 cb => \&IO::AIO::poll_cb); 946 cb => \&IO::AIO::poll_cb);
860 947
861=item IO::AIO::poll_some $max_requests 948=item IO::AIO::max_poll_reqs $nreqs
862 949
863Similar to C<poll_cb>, but only processes up to C<$max_requests> requests 950=item IO::AIO::max_poll_time $seconds
864at a time.
865 951
866Useful if you want to ensure some level of interactiveness when perl is 952These set the maximum number of requests (default C<0>, meaning infinity)
867not fast enough to process all requests in time. 953that are being processed by C<IO::AIO::poll_cb> in one call, respectively
954the maximum amount of time (default C<0>, meaning infinity) spent in
955C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
956of time C<poll_cb> is allowed to use).
957
958Setting C<max_poll_time> to a non-zero value creates an overhead of one
959syscall per request processed, which is not normally a problem unless your
960callbacks are really really fast or your OS is really really slow (I am
961not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
962
963Setting these is useful if you want to ensure some level of
964interactiveness when perl is not fast enough to process all requests in
965time.
966
967For interactive programs, values such as C<0.01> to C<0.1> should be fine.
868 968
869Example: Install an Event watcher that automatically calls 969Example: Install an Event watcher that automatically calls
870IO::AIO::poll_some with low priority, to ensure that other parts of the 970IO::AIO::poll_cb with low priority, to ensure that other parts of the
871program get the CPU sometimes even under high AIO load. 971program get the CPU sometimes even under high AIO load.
872 972
973 # try not to spend much more than 0.1s in poll_cb
974 IO::AIO::max_poll_time 0.1;
975
976 # use a low priority so other tasks have priority
873 Event->io (fd => IO::AIO::poll_fileno, 977 Event->io (fd => IO::AIO::poll_fileno,
874 poll => 'r', nice => 1, 978 poll => 'r', nice => 1,
875 cb => sub { IO::AIO::poll_some 256 }); 979 cb => &IO::AIO::poll_cb);
876 980
877=item IO::AIO::poll_wait 981=item IO::AIO::poll_wait
878 982
983If there are any outstanding requests and none of them in the result
879Wait till the result filehandle becomes ready for reading (simply does a 984phase, wait till the result filehandle becomes ready for reading (simply
880C<select> on the filehandle. This is useful if you want to synchronously wait 985does a C<select> on the filehandle. This is useful if you want to
881for some requests to finish). 986synchronously wait for some requests to finish).
882 987
883See C<nreqs> for an example. 988See C<nreqs> for an example.
884 989
990=item IO::AIO::poll
991
992Waits until some requests have been handled.
993
994Returns the number of requests processed, but is otherwise strictly
995equivalent to:
996
997 IO::AIO::poll_wait, IO::AIO::poll_cb
998
885=item IO::AIO::nreqs 999=item IO::AIO::flush
886 1000
887Returns the number of requests currently in the ready, execute or pending 1001Wait till all outstanding AIO requests have been handled.
888states (i.e. for which their callback has not been invoked yet).
889 1002
890Example: wait till there are no outstanding requests anymore: 1003Strictly equivalent to:
891 1004
892 IO::AIO::poll_wait, IO::AIO::poll_cb 1005 IO::AIO::poll_wait, IO::AIO::poll_cb
893 while IO::AIO::nreqs; 1006 while IO::AIO::nreqs;
894 1007
895=item IO::AIO::nready 1008=head3 CONTROLLING THE NUMBER OF THREADS
896
897Returns the number of requests currently in the ready state (not yet
898executed).
899
900=item IO::AIO::npending
901
902Returns the number of requests currently in the pending state (executed,
903but not yet processed by poll_cb).
904
905=item IO::AIO::flush
906
907Wait till all outstanding AIO requests have been handled.
908
909Strictly equivalent to:
910
911 IO::AIO::poll_wait, IO::AIO::poll_cb
912 while IO::AIO::nreqs;
913
914=item IO::AIO::poll
915
916Waits until some requests have been handled.
917
918Strictly equivalent to:
919
920 IO::AIO::poll_wait, IO::AIO::poll_cb
921 if IO::AIO::nreqs;
922 1009
923=item IO::AIO::min_parallel $nthreads 1010=item IO::AIO::min_parallel $nthreads
924 1011
925Set the minimum number of AIO threads to C<$nthreads>. The current 1012Set the minimum number of AIO threads to C<$nthreads>. The current
926default is C<8>, which means eight asynchronous operations can execute 1013default is C<8>, which means eight asynchronous operations can execute
927concurrently at any one time (the number of outstanding requests, 1014concurrently at any one time (the number of outstanding requests,
928however, is unlimited). 1015however, is unlimited).
929 1016
930IO::AIO starts threads only on demand, when an AIO request is queued and 1017IO::AIO starts threads only on demand, when an AIO request is queued and
931no free thread exists. 1018no free thread exists. Please note that queueing up a hundred requests can
1019create demand for a hundred threads, even if it turns out that everything
1020is in the cache and could have been processed faster by a single thread.
932 1021
933It is recommended to keep the number of threads relatively low, as some 1022It is recommended to keep the number of threads relatively low, as some
934Linux kernel versions will scale negatively with the number of threads 1023Linux kernel versions will scale negatively with the number of threads
935(higher parallelity => MUCH higher latency). With current Linux 2.6 1024(higher parallelity => MUCH higher latency). With current Linux 2.6
936versions, 4-32 threads should be fine. 1025versions, 4-32 threads should be fine.
… …
950This module automatically runs C<max_parallel 0> at program end, to ensure 1039This module automatically runs C<max_parallel 0> at program end, to ensure
951that all threads are killed and that there are no outstanding requests. 1040that all threads are killed and that there are no outstanding requests.
952 1041
953Under normal circumstances you don't need to call this function. 1042Under normal circumstances you don't need to call this function.
954 1043
1044=item IO::AIO::max_idle $nthreads
1045
1046Limit the number of threads (default: 4) that are allowed to idle (i.e.,
1047threads that did not get a request to process within 10 seconds). That
1048means if a thread becomes idle while C<$nthreads> other threads are also
1049idle, it will free its resources and exit.
1050
1051This is useful when you allow a large number of threads (e.g. 100 or 1000)
1052to allow for extremely high load situations, but want to free resources
1053under normal circumstances (1000 threads can easily consume 30MB of RAM).
1054
1055The default is probably ok in most situations, especially if thread
1056creation is fast. If thread creation is very slow on your system you might
1057want to use larger values.
1058
955=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1059=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
956 1060
957This is a very bad function to use in interactive programs because it 1061This is a very bad function to use in interactive programs because it
958blocks, and a bad way to reduce concurrency because it is inexact: Better 1062blocks, and a bad way to reduce concurrency because it is inexact: Better
959use an C<aio_group> together with a feed callback. 1063use an C<aio_group> together with a feed callback.
… …
968 1072
969You can still queue as many requests as you want. Therefore, 1073You can still queue as many requests as you want. Therefore,
970C<max_oustsanding> is mainly useful in simple scripts (with low values) or 1074C<max_oustsanding> is mainly useful in simple scripts (with low values) or
971as a stop gap to shield against fatal memory overflow (with large values). 1075as a stop gap to shield against fatal memory overflow (with large values).
972 1076
1077=head3 STATISTICAL INFORMATION
1078
1079=item IO::AIO::nreqs
1080
1081Returns the number of requests currently in the ready, execute or pending
1082states (i.e. for which their callback has not been invoked yet).
1083
1084Example: wait till there are no outstanding requests anymore:
1085
1086 IO::AIO::poll_wait, IO::AIO::poll_cb
1087 while IO::AIO::nreqs;
1088
1089=item IO::AIO::nready
1090
1091Returns the number of requests currently in the ready state (not yet
1092executed).
1093
1094=item IO::AIO::npending
1095
1096Returns the number of requests currently in the pending state (executed,
1097but not yet processed by poll_cb).
1098
973=back 1099=back
974 1100
975=cut 1101=cut
976 1102
977# support function to convert a fd into a perl filehandle 1103# support function to convert a fd into a perl filehandle
… …
990 *$sym 1116 *$sym
991} 1117}
992 1118
993min_parallel 8; 1119min_parallel 8;
994 1120
995END { 1121END { flush }
996 min_parallel 1;
997 flush;
998};
999 1122
10001; 11231;
1001 1124
1002=head2 FORK BEHAVIOUR 1125=head2 FORK BEHAVIOUR
1003 1126

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