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Revision 1.82 by root, Fri Oct 27 20:10:06 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
… …
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.
… …
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): the only 408Asynchronously create a device node (or fifo). See mknod(2).
337portable value for C<$mode> is C<S_IFIFO> ored with permissions, and C<0> 409
338for C<$dev>. 410The only (POSIX-) portable way of calling this function is:
411
412 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
339 413
340=item aio_link $srcpath, $dstpath, $callback->($status) 414=item aio_link $srcpath, $dstpath, $callback->($status)
341 415
342Asynchronously create a new link to the existing object at C<$srcpath> at 416Asynchronously create a new link to the existing object at C<$srcpath> at
343the path C<$dstpath> and call the callback with the result code. 417the path C<$dstpath> and call the callback with the result code.
344 418
345=item aio_symlink $srcpath, $dstpath, $callback->($status) 419=item aio_symlink $srcpath, $dstpath, $callback->($status)
346 420
347Asynchronously 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
348the 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.
349 429
350=item aio_rename $srcpath, $dstpath, $callback->($status) 430=item aio_rename $srcpath, $dstpath, $callback->($status)
351 431
352Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as 432Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
353rename(2) and call the callback with the result code. 433rename(2) and call the callback with the result code.
… …
382errors are being ignored. 462errors are being ignored.
383 463
384=cut 464=cut
385 465
386sub aio_copy($$;$) { 466sub aio_copy($$;$) {
467 aio_block {
387 my ($src, $dst, $cb) = @_; 468 my ($src, $dst, $cb) = @_;
388 469
389 my $pri = aioreq_pri; 470 my $pri = aioreq_pri;
390 my $grp = aio_group $cb; 471 my $grp = aio_group $cb;
391 472
392 aioreq_pri $pri; 473 aioreq_pri $pri;
393 add $grp aio_open $src, O_RDONLY, 0, sub { 474 add $grp aio_open $src, O_RDONLY, 0, sub {
394 if (my $src_fh = $_[0]) { 475 if (my $src_fh = $_[0]) {
395 my @stat = stat $src_fh; 476 my @stat = stat $src_fh;
396 477
397 aioreq_pri $pri; 478 aioreq_pri $pri;
398 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 {
399 if (my $dst_fh = $_[0]) { 480 if (my $dst_fh = $_[0]) {
400 aioreq_pri $pri; 481 aioreq_pri $pri;
401 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub { 482 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
402 if ($_[0] == $stat[7]) { 483 if ($_[0] == $stat[7]) {
403 $grp->result (0); 484 $grp->result (0);
404 close $src_fh; 485 close $src_fh;
405 486
406 # those should not normally block. should. should. 487 # those should not normally block. should. should.
407 utime $stat[8], $stat[9], $dst; 488 utime $stat[8], $stat[9], $dst;
408 chmod $stat[2] & 07777, $dst_fh; 489 chmod $stat[2] & 07777, $dst_fh;
409 chown $stat[4], $stat[5], $dst_fh; 490 chown $stat[4], $stat[5], $dst_fh;
410 close $dst_fh; 491 close $dst_fh;
411 } else { 492 } else {
412 $grp->result (-1); 493 $grp->result (-1);
413 close $src_fh; 494 close $src_fh;
414 close $dst_fh; 495 close $dst_fh;
415 496
416 aioreq $pri; 497 aioreq $pri;
417 add $grp aio_unlink $dst; 498 add $grp aio_unlink $dst;
499 }
418 } 500 };
501 } else {
502 $grp->result (-1);
419 }; 503 }
420 } else {
421 $grp->result (-1);
422 } 504 },
505
506 } else {
507 $grp->result (-1);
423 }, 508 }
424
425 } else {
426 $grp->result (-1);
427 } 509 };
510
511 $grp
428 }; 512 }
429
430 $grp
431} 513}
432 514
433=item aio_move $srcpath, $dstpath, $callback->($status) 515=item aio_move $srcpath, $dstpath, $callback->($status)
434 516
435Try 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
… …
441that is successful, unlinking the C<$srcpath>. 523that is successful, unlinking the C<$srcpath>.
442 524
443=cut 525=cut
444 526
445sub aio_move($$;$) { 527sub aio_move($$;$) {
528 aio_block {
446 my ($src, $dst, $cb) = @_; 529 my ($src, $dst, $cb) = @_;
447 530
448 my $pri = aioreq_pri; 531 my $pri = aioreq_pri;
449 my $grp = aio_group $cb; 532 my $grp = aio_group $cb;
450 533
451 aioreq_pri $pri; 534 aioreq_pri $pri;
452 add $grp aio_rename $src, $dst, sub { 535 add $grp aio_rename $src, $dst, sub {
453 if ($_[0] && $! == EXDEV) { 536 if ($_[0] && $! == EXDEV) {
454 aioreq_pri $pri; 537 aioreq_pri $pri;
455 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 {
456 $grp->result ($_[0]); 547 $grp->result ($_[0]);
457
458 if (!$_[0]) {
459 aioreq_pri $pri;
460 add $grp aio_unlink $src;
461 }
462 }; 548 }
463 } else {
464 $grp->result ($_[0]);
465 } 549 };
550
551 $grp
466 }; 552 }
467
468 $grp
469} 553}
470 554
471=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 555=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
472 556
473Scans a directory (similar to C<aio_readdir>) but additionally tries to 557Scans a directory (similar to C<aio_readdir>) but additionally tries to
… …
521directory counting heuristic. 605directory counting heuristic.
522 606
523=cut 607=cut
524 608
525sub aio_scandir($$$) { 609sub aio_scandir($$$) {
610 aio_block {
526 my ($path, $maxreq, $cb) = @_; 611 my ($path, $maxreq, $cb) = @_;
527 612
528 my $pri = aioreq_pri; 613 my $pri = aioreq_pri;
529 614
530 my $grp = aio_group $cb; 615 my $grp = aio_group $cb;
531 616
532 $maxreq = 4 if $maxreq <= 0; 617 $maxreq = 4 if $maxreq <= 0;
533 618
534 # stat once 619 # stat once
535 aioreq_pri $pri;
536 add $grp aio_stat $path, sub {
537 return $grp->result () if $_[0];
538 my $now = time;
539 my $hash1 = join ":", (stat _)[0,1,3,7,9];
540
541 # read the directory entries
542 aioreq_pri $pri; 620 aioreq_pri $pri;
543 add $grp aio_readdir $path, sub { 621 add $grp aio_stat $path, sub {
544 my $entries = shift
545 or return $grp->result (); 622 return $grp->result () if $_[0];
623 my $now = time;
624 my $hash1 = join ":", (stat _)[0,1,3,7,9];
546 625
547 # stat the dir another time 626 # read the directory entries
548 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;
549 add $grp aio_stat $path, sub { 634 add $grp aio_stat $path, sub {
550 my $hash2 = join ":", (stat _)[0,1,3,7,9]; 635 my $hash2 = join ":", (stat _)[0,1,3,7,9];
551 636
552 my $ndirs; 637 my $ndirs;
553 638
554 # take the slow route if anything looks fishy 639 # take the slow route if anything looks fishy
555 if ($hash1 ne $hash2 or (stat _)[9] == $now) { 640 if ($hash1 ne $hash2 or (stat _)[9] == $now) {
556 $ndirs = -1; 641 $ndirs = -1;
557 } else { 642 } else {
558 # if nlink == 2, we are finished 643 # if nlink == 2, we are finished
559 # on non-posix-fs's, we rely on nlink < 2 644 # on non-posix-fs's, we rely on nlink < 2
560 $ndirs = (stat _)[3] - 2 645 $ndirs = (stat _)[3] - 2
561 or return $grp->result ([], $entries); 646 or return $grp->result ([], $entries);
562 } 647 }
563 648
564 # sort into likely dirs and likely nondirs 649 # sort into likely dirs and likely nondirs
565 # dirs == files without ".", short entries first 650 # dirs == files without ".", short entries first
566 $entries = [map $_->[0], 651 $entries = [map $_->[0],
567 sort { $b->[1] cmp $a->[1] } 652 sort { $b->[1] cmp $a->[1] }
568 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length], 653 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
569 @$entries]; 654 @$entries];
570 655
571 my (@dirs, @nondirs); 656 my (@dirs, @nondirs);
572 657
573 my $statgrp = add $grp aio_group sub { 658 my $statgrp = add $grp aio_group sub {
574 $grp->result (\@dirs, \@nondirs); 659 $grp->result (\@dirs, \@nondirs);
575 }; 660 };
576 661
577 limit $statgrp $maxreq; 662 limit $statgrp $maxreq;
578 feed $statgrp sub { 663 feed $statgrp sub {
579 return unless @$entries; 664 return unless @$entries;
580 my $entry = pop @$entries; 665 my $entry = pop @$entries;
581 666
582 aioreq_pri $pri; 667 aioreq_pri $pri;
583 add $statgrp aio_stat "$path/$entry/.", sub { 668 add $statgrp aio_stat "$path/$entry/.", sub {
584 if ($_[0] < 0) { 669 if ($_[0] < 0) {
585 push @nondirs, $entry; 670 push @nondirs, $entry;
586 } else { 671 } else {
587 # need to check for real directory 672 # need to check for real directory
588 aioreq_pri $pri; 673 aioreq_pri $pri;
589 add $statgrp aio_lstat "$path/$entry", sub { 674 add $statgrp aio_lstat "$path/$entry", sub {
590 if (-d _) { 675 if (-d _) {
591 push @dirs, $entry; 676 push @dirs, $entry;
592 677
593 unless (--$ndirs) { 678 unless (--$ndirs) {
594 push @nondirs, @$entries; 679 push @nondirs, @$entries;
595 feed $statgrp; 680 feed $statgrp;
681 }
682 } else {
683 push @nondirs, $entry;
596 } 684 }
597 } else {
598 push @nondirs, $entry;
599 } 685 }
600 } 686 }
601 } 687 };
602 }; 688 };
603 }; 689 };
604 }; 690 };
605 }; 691 };
692
693 $grp
606 }; 694 }
607
608 $grp
609} 695}
610 696
611=item aio_fsync $fh, $callback->($status) 697=item aio_fsync $fh, $callback->($status)
612 698
613Asynchronously call fsync on the given filehandle and call the callback 699Asynchronously call fsync on the given filehandle and call the callback
… …
827 913
828=back 914=back
829 915
830=head2 SUPPORT FUNCTIONS 916=head2 SUPPORT FUNCTIONS
831 917
918=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
919
832=over 4 920=over 4
833 921
834=item $fileno = IO::AIO::poll_fileno 922=item $fileno = IO::AIO::poll_fileno
835 923
836Return the I<request result pipe file descriptor>. This filehandle must be 924Return the I<request result pipe file descriptor>. This filehandle must be
… …
840 928
841See C<poll_cb> for an example. 929See C<poll_cb> for an example.
842 930
843=item IO::AIO::poll_cb 931=item IO::AIO::poll_cb
844 932
845Process 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
846regularly. Returns the number of events processed. Returns immediately 934regularly. Returns the number of events processed. Returns immediately
847when 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>.
848 937
849If not all requests were processed for whatever reason, the filehandle 938If not all requests were processed for whatever reason, the filehandle
850will still be ready when C<poll_cb> returns. 939will still be ready when C<poll_cb> returns.
851 940
852Example: Install an Event watcher that automatically calls 941Example: Install an Event watcher that automatically calls
… …
854 943
855 Event->io (fd => IO::AIO::poll_fileno, 944 Event->io (fd => IO::AIO::poll_fileno,
856 poll => 'r', async => 1, 945 poll => 'r', async => 1,
857 cb => \&IO::AIO::poll_cb); 946 cb => \&IO::AIO::poll_cb);
858 947
859=item IO::AIO::poll_some $max_requests 948=item IO::AIO::max_poll_reqs $nreqs
860 949
861Similar to C<poll_cb>, but only processes up to C<$max_requests> requests 950=item IO::AIO::max_poll_time $seconds
862at a time.
863 951
864Useful if you want to ensure some level of interactiveness when perl is 952These set the maximum number of requests (default C<0>, meaning infinity)
865not 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.
866 968
867Example: Install an Event watcher that automatically calls 969Example: Install an Event watcher that automatically calls
868IO::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
869program get the CPU sometimes even under high AIO load. 971program get the CPU sometimes even under high AIO load.
870 972
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
871 Event->io (fd => IO::AIO::poll_fileno, 977 Event->io (fd => IO::AIO::poll_fileno,
872 poll => 'r', nice => 1, 978 poll => 'r', nice => 1,
873 cb => sub { IO::AIO::poll_some 256 }); 979 cb => &IO::AIO::poll_cb);
874 980
875=item IO::AIO::poll_wait 981=item IO::AIO::poll_wait
876 982
983If there are any outstanding requests and none of them in the result
877Wait till the result filehandle becomes ready for reading (simply does a 984phase, wait till the result filehandle becomes ready for reading (simply
878C<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
879for some requests to finish). 986synchronously wait for some requests to finish).
880 987
881See C<nreqs> for an example. 988See C<nreqs> for an example.
882 989
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
883=item IO::AIO::nreqs 999=item IO::AIO::flush
884 1000
885Returns the number of requests currently in the ready, execute or pending 1001Wait till all outstanding AIO requests have been handled.
886states (i.e. for which their callback has not been invoked yet).
887 1002
888Example: wait till there are no outstanding requests anymore: 1003Strictly equivalent to:
889 1004
890 IO::AIO::poll_wait, IO::AIO::poll_cb 1005 IO::AIO::poll_wait, IO::AIO::poll_cb
891 while IO::AIO::nreqs; 1006 while IO::AIO::nreqs;
892 1007
893=item IO::AIO::nready 1008=head3 CONTROLLING THE NUMBER OF THREADS
894
895Returns the number of requests currently in the ready state (not yet
896executed).
897
898=item IO::AIO::npending
899
900Returns the number of requests currently in the pending state (executed,
901but not yet processed by poll_cb).
902
903=item IO::AIO::flush
904
905Wait till all outstanding AIO requests have been handled.
906
907Strictly equivalent to:
908
909 IO::AIO::poll_wait, IO::AIO::poll_cb
910 while IO::AIO::nreqs;
911
912=item IO::AIO::poll
913
914Waits until some requests have been handled.
915
916Strictly equivalent to:
917
918 IO::AIO::poll_wait, IO::AIO::poll_cb
919 if IO::AIO::nreqs;
920 1009
921=item IO::AIO::min_parallel $nthreads 1010=item IO::AIO::min_parallel $nthreads
922 1011
923Set the minimum number of AIO threads to C<$nthreads>. The current 1012Set the minimum number of AIO threads to C<$nthreads>. The current
924default is C<8>, which means eight asynchronous operations can execute 1013default is C<8>, which means eight asynchronous operations can execute
925concurrently at any one time (the number of outstanding requests, 1014concurrently at any one time (the number of outstanding requests,
926however, is unlimited). 1015however, is unlimited).
927 1016
928IO::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
929no 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.
930 1021
931It 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
932Linux kernel versions will scale negatively with the number of threads 1023Linux kernel versions will scale negatively with the number of threads
933(higher parallelity => MUCH higher latency). With current Linux 2.6 1024(higher parallelity => MUCH higher latency). With current Linux 2.6
934versions, 4-32 threads should be fine. 1025versions, 4-32 threads should be fine.
… …
948This 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
949that all threads are killed and that there are no outstanding requests. 1040that all threads are killed and that there are no outstanding requests.
950 1041
951Under normal circumstances you don't need to call this function. 1042Under normal circumstances you don't need to call this function.
952 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
953=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1059=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
954 1060
955This is a very bad function to use in interactive programs because it 1061This is a very bad function to use in interactive programs because it
956blocks, and a bad way to reduce concurrency because it is inexact: Better 1062blocks, and a bad way to reduce concurrency because it is inexact: Better
957use an C<aio_group> together with a feed callback. 1063use an C<aio_group> together with a feed callback.
… …
966 1072
967You can still queue as many requests as you want. Therefore, 1073You can still queue as many requests as you want. Therefore,
968C<max_oustsanding> is mainly useful in simple scripts (with low values) or 1074C<max_oustsanding> is mainly useful in simple scripts (with low values) or
969as a stop gap to shield against fatal memory overflow (with large values). 1075as a stop gap to shield against fatal memory overflow (with large values).
970 1076
1077=head3 STATISTICAL INFORMATION
1078
1079=item IO::AIO::nreqs
1080
1081Returns the number of requests currently in the ready, execute or pending
1082states (i.e. for which their callback has not been invoked yet).
1083
1084Example: wait till there are no outstanding requests anymore:
1085
1086 IO::AIO::poll_wait, IO::AIO::poll_cb
1087 while IO::AIO::nreqs;
1088
1089=item IO::AIO::nready
1090
1091Returns the number of requests currently in the ready state (not yet
1092executed).
1093
1094=item IO::AIO::npending
1095
1096Returns the number of requests currently in the pending state (executed,
1097but not yet processed by poll_cb).
1098
971=back 1099=back
972 1100
973=cut 1101=cut
974 1102
975# support function to convert a fd into a perl filehandle 1103# support function to convert a fd into a perl filehandle
… …
988 *$sym 1116 *$sym
989} 1117}
990 1118
991min_parallel 8; 1119min_parallel 8;
992 1120
993END { 1121END { flush }
994 flush;
995};
996 1122
9971; 11231;
998 1124
999=head2 FORK BEHAVIOUR 1125=head2 FORK BEHAVIOUR
1000 1126

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