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Revision 1.85 by root, Sat Oct 28 01:40:30 2006 UTC vs.
Revision 1.95 by root, Sun Nov 26 18:28:37 2006 UTC

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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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61etc.), but can also be used to easily do operations in parallel that are 62etc.), but can also be used to easily do operations in parallel that are
62normally done sequentially, e.g. stat'ing many files, which is much faster 63normally done sequentially, e.g. stat'ing many files, which is much faster
63on a RAID volume or over NFS when you do a number of stat operations 64on a RAID volume or over NFS when you do a number of stat operations
64concurrently. 65concurrently.
65 66
66While this works on all types of file descriptors (for example sockets), 67While most of this works on all types of file descriptors (for example
67using these functions on file descriptors that support nonblocking 68sockets), using these functions on file descriptors that support
68operation (again, sockets, pipes etc.) is very inefficient. Use an event 69nonblocking operation (again, sockets, pipes etc.) is very inefficient or
70might not work (aio_read fails on sockets/pipes/fifos). Use an event loop
69loop for that (such as the L<Event|Event> module): IO::AIO will naturally 71for that (such as the L<Event|Event> module): IO::AIO will naturally fit
70fit into such an event loop itself. 72into such an event loop itself.
71 73
72In this version, a number of threads are started that execute your 74In this version, a number of threads are started that execute your
73requests and signal their completion. You don't need thread support 75requests and signal their completion. You don't need thread support
74in 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
75to 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
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82Although the module will work with in the presence of other (Perl-) 84Although the module will work with in the presence of other (Perl-)
83threads, it is currently not reentrant in any way, so use appropriate 85threads, it is currently not reentrant in any way, so use appropriate
84locking 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
85never call C<poll_cb> (or other C<aio_> functions) recursively. 87never call C<poll_cb> (or other C<aio_> functions) recursively.
86 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
87=head1 REQUEST ANATOMY AND LIFETIME 133=head1 REQUEST ANATOMY AND LIFETIME
88 134
89Every 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
90directly visible to Perl. 136directly visible to Perl.
91 137
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132Request 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
133(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
134aio 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
135result in a runtime error). 181result in a runtime error).
136 182
183=back
184
137=cut 185=cut
138 186
139package IO::AIO; 187package IO::AIO;
140 188
141no warnings; 189no warnings;
142use strict 'vars'; 190use strict 'vars';
143 191
144use base 'Exporter'; 192use base 'Exporter';
145 193
146BEGIN { 194BEGIN {
147 our $VERSION = '2.0'; 195 our $VERSION = '2.2';
148 196
149 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
150 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
151 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
152 aio_copy aio_group aio_nop aio_mknod); 200 aio_move aio_copy aio_group aio_nop aio_mknod);
153 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice)); 201 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
154 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush 202 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
155 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);
156 206
157 @IO::AIO::GRP::ISA = 'IO::AIO::REQ'; 207 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
158 208
159 require XSLoader; 209 require XSLoader;
160 XSLoader::load ("IO::AIO", $VERSION); 210 XSLoader::load ("IO::AIO", $VERSION);
161} 211}
162 212
163=head1 FUNCTIONS 213=head1 FUNCTIONS
164 214
165=head2 AIO FUNCTIONS 215=head2 AIO REQUEST FUNCTIONS
166 216
167All the C<aio_*> calls are more or less thin wrappers around the syscall 217All the C<aio_*> calls are more or less thin wrappers around the syscall
168with the same name (sans C<aio_>). The arguments are similar or identical, 218with the same name (sans C<aio_>). The arguments are similar or identical,
169and they all accept an additional (and optional) C<$callback> argument 219and they all accept an additional (and optional) C<$callback> argument
170which 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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173syscall has been executed asynchronously. 223syscall has been executed asynchronously.
174 224
175All functions expecting a filehandle keep a copy of the filehandle 225All functions expecting a filehandle keep a copy of the filehandle
176internally until the request has finished. 226internally until the request has finished.
177 227
178All 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
179manipulation of those requests while they are in-flight. 229further manipulation of those requests while they are in-flight.
180 230
181The pathnames you pass to these routines I<must> be absolute and 231The pathnames you pass to these routines I<must> be absolute and
182encoded 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
183request is being executed, the current working directory could have 233request is being executed, the current working directory could have
184changed. Alternatively, you can make sure that you never change the 234changed. Alternatively, you can make sure that you never change the
185current working directory. 235current working directory anywhere in the program and then use relative
236paths.
186 237
187To encode pathnames to byte form, either make sure you either: a) 238To encode pathnames as octets, either make sure you either: a) always pass
188always pass in filenames you got from outside (command line, readdir 239in filenames you got from outside (command line, readdir etc.) without
189etc.), 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
190your 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
191environment, d) use Glib::filename_from_unicode on unicode filenames or e) 242environment, d) use Glib::filename_from_unicode on unicode filenames or e)
192use 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.
193 247
194=over 4 248=over 4
195 249
196=item $prev_pri = aioreq_pri [$pri] 250=item $prev_pri = aioreq_pri [$pri]
197 251
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220 }; 274 };
221 275
222=item aioreq_nice $pri_adjust 276=item aioreq_nice $pri_adjust
223 277
224Similar 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
225priority, so effects are cumulative. 279priority, so the effect is cumulative.
226 280
227=item aio_open $pathname, $flags, $mode, $callback->($fh) 281=item aio_open $pathname, $flags, $mode, $callback->($fh)
228 282
229Asynchronously 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
230created filehandle for the file. 284created filehandle for the file.
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347Asynchronously unlink (delete) a file and call the callback with the 401Asynchronously unlink (delete) a file and call the callback with the
348result code. 402result code.
349 403
350=item aio_mknod $path, $mode, $dev, $callback->($status) 404=item aio_mknod $path, $mode, $dev, $callback->($status)
351 405
406[EXPERIMENTAL]
407
352Asynchronously create a device node (or fifo). See mknod(2). 408Asynchronously create a device node (or fifo). See mknod(2).
353 409
354The only portable (POSIX) way of calling this function is: 410The only (POSIX-) portable way of calling this function is:
355 411
356 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 412 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
357 413
358=item aio_link $srcpath, $dstpath, $callback->($status) 414=item aio_link $srcpath, $dstpath, $callback->($status)
359 415
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362 418
363=item aio_symlink $srcpath, $dstpath, $callback->($status) 419=item aio_symlink $srcpath, $dstpath, $callback->($status)
364 420
365Asynchronously 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
366the 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.
367 429
368=item aio_rename $srcpath, $dstpath, $callback->($status) 430=item aio_rename $srcpath, $dstpath, $callback->($status)
369 431
370Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as 432Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
371rename(2) and call the callback with the result code. 433rename(2) and call the callback with the result code.
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400errors are being ignored. 462errors are being ignored.
401 463
402=cut 464=cut
403 465
404sub aio_copy($$;$) { 466sub aio_copy($$;$) {
467 aio_block {
405 my ($src, $dst, $cb) = @_; 468 my ($src, $dst, $cb) = @_;
406 469
407 my $pri = aioreq_pri; 470 my $pri = aioreq_pri;
408 my $grp = aio_group $cb; 471 my $grp = aio_group $cb;
409 472
410 aioreq_pri $pri; 473 aioreq_pri $pri;
411 add $grp aio_open $src, O_RDONLY, 0, sub { 474 add $grp aio_open $src, O_RDONLY, 0, sub {
412 if (my $src_fh = $_[0]) { 475 if (my $src_fh = $_[0]) {
413 my @stat = stat $src_fh; 476 my @stat = stat $src_fh;
414 477
415 aioreq_pri $pri; 478 aioreq_pri $pri;
416 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 {
417 if (my $dst_fh = $_[0]) { 480 if (my $dst_fh = $_[0]) {
418 aioreq_pri $pri; 481 aioreq_pri $pri;
419 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub { 482 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
420 if ($_[0] == $stat[7]) { 483 if ($_[0] == $stat[7]) {
421 $grp->result (0); 484 $grp->result (0);
422 close $src_fh; 485 close $src_fh;
423 486
424 # those should not normally block. should. should. 487 # those should not normally block. should. should.
425 utime $stat[8], $stat[9], $dst; 488 utime $stat[8], $stat[9], $dst;
426 chmod $stat[2] & 07777, $dst_fh; 489 chmod $stat[2] & 07777, $dst_fh;
427 chown $stat[4], $stat[5], $dst_fh; 490 chown $stat[4], $stat[5], $dst_fh;
428 close $dst_fh; 491 close $dst_fh;
429 } else { 492 } else {
430 $grp->result (-1); 493 $grp->result (-1);
431 close $src_fh; 494 close $src_fh;
432 close $dst_fh; 495 close $dst_fh;
433 496
434 aioreq $pri; 497 aioreq $pri;
435 add $grp aio_unlink $dst; 498 add $grp aio_unlink $dst;
499 }
436 } 500 };
501 } else {
502 $grp->result (-1);
437 }; 503 }
438 } else {
439 $grp->result (-1);
440 } 504 },
505
506 } else {
507 $grp->result (-1);
441 }, 508 }
442
443 } else {
444 $grp->result (-1);
445 } 509 };
510
511 $grp
446 }; 512 }
447
448 $grp
449} 513}
450 514
451=item aio_move $srcpath, $dstpath, $callback->($status) 515=item aio_move $srcpath, $dstpath, $callback->($status)
452 516
453Try 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
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459that is successful, unlinking the C<$srcpath>. 523that is successful, unlinking the C<$srcpath>.
460 524
461=cut 525=cut
462 526
463sub aio_move($$;$) { 527sub aio_move($$;$) {
528 aio_block {
464 my ($src, $dst, $cb) = @_; 529 my ($src, $dst, $cb) = @_;
465 530
466 my $pri = aioreq_pri; 531 my $pri = aioreq_pri;
467 my $grp = aio_group $cb; 532 my $grp = aio_group $cb;
468 533
469 aioreq_pri $pri; 534 aioreq_pri $pri;
470 add $grp aio_rename $src, $dst, sub { 535 add $grp aio_rename $src, $dst, sub {
471 if ($_[0] && $! == EXDEV) { 536 if ($_[0] && $! == EXDEV) {
472 aioreq_pri $pri; 537 aioreq_pri $pri;
473 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 {
474 $grp->result ($_[0]); 547 $grp->result ($_[0]);
475
476 if (!$_[0]) {
477 aioreq_pri $pri;
478 add $grp aio_unlink $src;
479 }
480 }; 548 }
481 } else {
482 $grp->result ($_[0]);
483 } 549 };
550
551 $grp
484 }; 552 }
485
486 $grp
487} 553}
488 554
489=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 555=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
490 556
491Scans a directory (similar to C<aio_readdir>) but additionally tries to 557Scans a directory (similar to C<aio_readdir>) but additionally tries to
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539directory counting heuristic. 605directory counting heuristic.
540 606
541=cut 607=cut
542 608
543sub aio_scandir($$$) { 609sub aio_scandir($$$) {
610 aio_block {
544 my ($path, $maxreq, $cb) = @_; 611 my ($path, $maxreq, $cb) = @_;
545 612
546 my $pri = aioreq_pri; 613 my $pri = aioreq_pri;
547 614
548 my $grp = aio_group $cb; 615 my $grp = aio_group $cb;
549 616
550 $maxreq = 4 if $maxreq <= 0; 617 $maxreq = 4 if $maxreq <= 0;
551 618
552 # stat once 619 # stat once
553 aioreq_pri $pri;
554 add $grp aio_stat $path, sub {
555 return $grp->result () if $_[0];
556 my $now = time;
557 my $hash1 = join ":", (stat _)[0,1,3,7,9];
558
559 # read the directory entries
560 aioreq_pri $pri; 620 aioreq_pri $pri;
561 add $grp aio_readdir $path, sub { 621 add $grp aio_stat $path, sub {
562 my $entries = shift
563 or return $grp->result (); 622 return $grp->result () if $_[0];
623 my $now = time;
624 my $hash1 = join ":", (stat _)[0,1,3,7,9];
564 625
565 # stat the dir another time 626 # read the directory entries
566 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;
567 add $grp aio_stat $path, sub { 634 add $grp aio_stat $path, sub {
568 my $hash2 = join ":", (stat _)[0,1,3,7,9]; 635 my $hash2 = join ":", (stat _)[0,1,3,7,9];
569 636
570 my $ndirs; 637 my $ndirs;
571 638
572 # take the slow route if anything looks fishy 639 # take the slow route if anything looks fishy
573 if ($hash1 ne $hash2 or (stat _)[9] == $now) { 640 if ($hash1 ne $hash2 or (stat _)[9] == $now) {
574 $ndirs = -1; 641 $ndirs = -1;
575 } else { 642 } else {
576 # if nlink == 2, we are finished 643 # if nlink == 2, we are finished
577 # on non-posix-fs's, we rely on nlink < 2 644 # on non-posix-fs's, we rely on nlink < 2
578 $ndirs = (stat _)[3] - 2 645 $ndirs = (stat _)[3] - 2
579 or return $grp->result ([], $entries); 646 or return $grp->result ([], $entries);
580 } 647 }
581 648
582 # sort into likely dirs and likely nondirs 649 # sort into likely dirs and likely nondirs
583 # dirs == files without ".", short entries first 650 # dirs == files without ".", short entries first
584 $entries = [map $_->[0], 651 $entries = [map $_->[0],
585 sort { $b->[1] cmp $a->[1] } 652 sort { $b->[1] cmp $a->[1] }
586 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length], 653 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
587 @$entries]; 654 @$entries];
588 655
589 my (@dirs, @nondirs); 656 my (@dirs, @nondirs);
590 657
591 my $statgrp = add $grp aio_group sub { 658 my $statgrp = add $grp aio_group sub {
592 $grp->result (\@dirs, \@nondirs); 659 $grp->result (\@dirs, \@nondirs);
593 }; 660 };
594 661
595 limit $statgrp $maxreq; 662 limit $statgrp $maxreq;
596 feed $statgrp sub { 663 feed $statgrp sub {
597 return unless @$entries; 664 return unless @$entries;
598 my $entry = pop @$entries; 665 my $entry = pop @$entries;
599 666
600 aioreq_pri $pri; 667 aioreq_pri $pri;
601 add $statgrp aio_stat "$path/$entry/.", sub { 668 add $statgrp aio_stat "$path/$entry/.", sub {
602 if ($_[0] < 0) { 669 if ($_[0] < 0) {
603 push @nondirs, $entry; 670 push @nondirs, $entry;
604 } else { 671 } else {
605 # need to check for real directory 672 # need to check for real directory
606 aioreq_pri $pri; 673 aioreq_pri $pri;
607 add $statgrp aio_lstat "$path/$entry", sub { 674 add $statgrp aio_lstat "$path/$entry", sub {
608 if (-d _) { 675 if (-d _) {
609 push @dirs, $entry; 676 push @dirs, $entry;
610 677
611 unless (--$ndirs) { 678 unless (--$ndirs) {
612 push @nondirs, @$entries; 679 push @nondirs, @$entries;
613 feed $statgrp; 680 feed $statgrp;
681 }
682 } else {
683 push @nondirs, $entry;
614 } 684 }
615 } else {
616 push @nondirs, $entry;
617 } 685 }
618 } 686 }
619 } 687 };
620 }; 688 };
621 }; 689 };
622 }; 690 };
623 }; 691 };
692
693 $grp
624 }; 694 }
625
626 $grp
627} 695}
628 696
629=item aio_fsync $fh, $callback->($status) 697=item aio_fsync $fh, $callback->($status)
630 698
631Asynchronously call fsync on the given filehandle and call the callback 699Asynchronously call fsync on the given filehandle and call the callback
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845 913
846=back 914=back
847 915
848=head2 SUPPORT FUNCTIONS 916=head2 SUPPORT FUNCTIONS
849 917
918=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
919
850=over 4 920=over 4
851 921
852=item $fileno = IO::AIO::poll_fileno 922=item $fileno = IO::AIO::poll_fileno
853 923
854Return the I<request result pipe file descriptor>. This filehandle must be 924Return the I<request result pipe file descriptor>. This filehandle must be
… …
858 928
859See C<poll_cb> for an example. 929See C<poll_cb> for an example.
860 930
861=item IO::AIO::poll_cb 931=item IO::AIO::poll_cb
862 932
863Process 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
864regularly. Returns the number of events processed. Returns immediately 934regularly. Returns the number of events processed. Returns immediately
865when 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>.
866 937
867If not all requests were processed for whatever reason, the filehandle 938If not all requests were processed for whatever reason, the filehandle
868will still be ready when C<poll_cb> returns. 939will still be ready when C<poll_cb> returns.
869 940
870Example: Install an Event watcher that automatically calls 941Example: Install an Event watcher that automatically calls
… …
872 943
873 Event->io (fd => IO::AIO::poll_fileno, 944 Event->io (fd => IO::AIO::poll_fileno,
874 poll => 'r', async => 1, 945 poll => 'r', async => 1,
875 cb => \&IO::AIO::poll_cb); 946 cb => \&IO::AIO::poll_cb);
876 947
877=item IO::AIO::poll_some $max_requests 948=item IO::AIO::max_poll_reqs $nreqs
878 949
879Similar to C<poll_cb>, but only processes up to C<$max_requests> requests 950=item IO::AIO::max_poll_time $seconds
880at a time.
881 951
882Useful if you want to ensure some level of interactiveness when perl is 952These set the maximum number of requests (default C<0>, meaning infinity)
883not 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.
884 968
885Example: Install an Event watcher that automatically calls 969Example: Install an Event watcher that automatically calls
886IO::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
887program get the CPU sometimes even under high AIO load. 971program get the CPU sometimes even under high AIO load.
888 972
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
889 Event->io (fd => IO::AIO::poll_fileno, 977 Event->io (fd => IO::AIO::poll_fileno,
890 poll => 'r', nice => 1, 978 poll => 'r', nice => 1,
891 cb => sub { IO::AIO::poll_some 256 }); 979 cb => &IO::AIO::poll_cb);
892 980
893=item IO::AIO::poll_wait 981=item IO::AIO::poll_wait
894 982
983If there are any outstanding requests and none of them in the result
895Wait till the result filehandle becomes ready for reading (simply does a 984phase, wait till the result filehandle becomes ready for reading (simply
896C<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
897for some requests to finish). 986synchronously wait for some requests to finish).
898 987
899See C<nreqs> for an example. 988See C<nreqs> for an example.
900 989
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
901=item IO::AIO::nreqs 999=item IO::AIO::flush
902 1000
903Returns the number of requests currently in the ready, execute or pending 1001Wait till all outstanding AIO requests have been handled.
904states (i.e. for which their callback has not been invoked yet).
905 1002
906Example: wait till there are no outstanding requests anymore: 1003Strictly equivalent to:
907 1004
908 IO::AIO::poll_wait, IO::AIO::poll_cb 1005 IO::AIO::poll_wait, IO::AIO::poll_cb
909 while IO::AIO::nreqs; 1006 while IO::AIO::nreqs;
910 1007
911=item IO::AIO::nready 1008=head3 CONTROLLING THE NUMBER OF THREADS
912
913Returns the number of requests currently in the ready state (not yet
914executed).
915
916=item IO::AIO::npending
917
918Returns the number of requests currently in the pending state (executed,
919but not yet processed by poll_cb).
920
921=item IO::AIO::flush
922
923Wait till all outstanding AIO requests have been handled.
924
925Strictly equivalent to:
926
927 IO::AIO::poll_wait, IO::AIO::poll_cb
928 while IO::AIO::nreqs;
929
930=item IO::AIO::poll
931
932Waits until some requests have been handled.
933
934Strictly equivalent to:
935
936 IO::AIO::poll_wait, IO::AIO::poll_cb
937 if IO::AIO::nreqs;
938 1009
939=item IO::AIO::min_parallel $nthreads 1010=item IO::AIO::min_parallel $nthreads
940 1011
941Set the minimum number of AIO threads to C<$nthreads>. The current 1012Set the minimum number of AIO threads to C<$nthreads>. The current
942default is C<8>, which means eight asynchronous operations can execute 1013default is C<8>, which means eight asynchronous operations can execute
943concurrently at any one time (the number of outstanding requests, 1014concurrently at any one time (the number of outstanding requests,
944however, is unlimited). 1015however, is unlimited).
945 1016
946IO::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
947no 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.
948 1021
949It 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
950Linux kernel versions will scale negatively with the number of threads 1023Linux kernel versions will scale negatively with the number of threads
951(higher parallelity => MUCH higher latency). With current Linux 2.6 1024(higher parallelity => MUCH higher latency). With current Linux 2.6
952versions, 4-32 threads should be fine. 1025versions, 4-32 threads should be fine.
… …
966This 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
967that all threads are killed and that there are no outstanding requests. 1040that all threads are killed and that there are no outstanding requests.
968 1041
969Under normal circumstances you don't need to call this function. 1042Under normal circumstances you don't need to call this function.
970 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
971=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1059=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
972 1060
973This is a very bad function to use in interactive programs because it 1061This is a very bad function to use in interactive programs because it
974blocks, and a bad way to reduce concurrency because it is inexact: Better 1062blocks, and a bad way to reduce concurrency because it is inexact: Better
975use an C<aio_group> together with a feed callback. 1063use an C<aio_group> together with a feed callback.
… …
984 1072
985You can still queue as many requests as you want. Therefore, 1073You can still queue as many requests as you want. Therefore,
986C<max_oustsanding> is mainly useful in simple scripts (with low values) or 1074C<max_oustsanding> is mainly useful in simple scripts (with low values) or
987as a stop gap to shield against fatal memory overflow (with large values). 1075as a stop gap to shield against fatal memory overflow (with large values).
988 1076
1077=head3 STATISTICAL INFORMATION
1078
1079=item IO::AIO::nreqs
1080
1081Returns the number of requests currently in the ready, execute or pending
1082states (i.e. for which their callback has not been invoked yet).
1083
1084Example: wait till there are no outstanding requests anymore:
1085
1086 IO::AIO::poll_wait, IO::AIO::poll_cb
1087 while IO::AIO::nreqs;
1088
1089=item IO::AIO::nready
1090
1091Returns the number of requests currently in the ready state (not yet
1092executed).
1093
1094=item IO::AIO::npending
1095
1096Returns the number of requests currently in the pending state (executed,
1097but not yet processed by poll_cb).
1098
989=back 1099=back
990 1100
991=cut 1101=cut
992 1102
993# support function to convert a fd into a perl filehandle 1103# support function to convert a fd into a perl filehandle
… …
1006 *$sym 1116 *$sym
1007} 1117}
1008 1118
1009min_parallel 8; 1119min_parallel 8;
1010 1120
1011END { 1121END { flush }
1012 min_parallel 1;
1013 flush;
1014};
1015 1122
10161; 11231;
1017 1124
1018=head2 FORK BEHAVIOUR 1125=head2 FORK BEHAVIOUR
1019 1126

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