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18 }; 18 };
19 19
20 # version 2+ has request and group objects 20 # version 2+ has request and group objects
21 use IO::AIO 2; 21 use IO::AIO 2;
22 22
23 aioreq_pri 4; # give next request a very high priority
23 my $req = aio_unlink "/tmp/file", sub { }; 24 my $req = aio_unlink "/tmp/file", sub { };
24 $req->cancel; # cancel request if still in queue 25 $req->cancel; # cancel request if still in queue
25 26
26 my $grp = aio_group sub { print "all stats done\n" }; 27 my $grp = aio_group sub { print "all stats done\n" };
27 add $grp aio_stat "..." for ...; 28 add $grp aio_stat "..." for ...;
50=head1 DESCRIPTION 51=head1 DESCRIPTION
51 52
52This module implements asynchronous I/O using whatever means your 53This module implements asynchronous I/O using whatever means your
53operating system supports. 54operating system supports.
54 55
55Currently, a number of threads are started that execute your read/writes 56In this version, a number of threads are started that execute your
56and signal their completion. You don't need thread support in perl, and 57requests and signal their completion. You don't need thread support
57the threads created by this module will not be visible to perl. In the 58in perl, and the threads created by this module will not be visible
58future, this module might make use of the native aio functions available 59to perl. In the future, this module might make use of the native aio
59on many operating systems. However, they are often not well-supported 60functions available on many operating systems. However, they are often
60(Linux doesn't allow them on normal files currently, for example), 61not well-supported or restricted (Linux doesn't allow them on normal
61and they would only support aio_read and aio_write, so the remaining 62files currently, for example), and they would only support aio_read and
62functionality would have to be implemented using threads anyway. 63aio_write, so the remaining functionality would have to be implemented
64using threads anyway.
63 65
64Although the module will work with in the presence of other threads, it is 66Although the module will work with in the presence of other (Perl-)
65currently not reentrant, so use appropriate locking yourself, always call 67threads, it is currently not reentrant in any way, so use appropriate
66C<poll_cb> from within the same thread, or never call C<poll_cb> (or other 68locking yourself, always call C<poll_cb> from within the same thread, or
67C<aio_> functions) recursively. 69never call C<poll_cb> (or other C<aio_> functions) recursively.
70
71=head1 REQUEST ANATOMY AND LIFETIME
72
73Every C<aio_*> function creates a request. which is a C data structure not
74directly visible to Perl.
75
76If called in non-void context, every request function returns a Perl
77object representing the request. In void context, nothing is returned,
78which saves a bit of memory.
79
80The perl object is a fairly standard ref-to-hash object. The hash contents
81are not used by IO::AIO so you are free to store anything you like in it.
82
83During their existance, aio requests travel through the following states,
84in order:
85
86=over 4
87
88=item ready
89
90Immediately after a request is created it is put into the ready state,
91waiting for a thread to execute it.
92
93=item execute
94
95A thread has accepted the request for processing and is currently
96executing it (e.g. blocking in read).
97
98=item pending
99
100The request has been executed and is waiting for result processing.
101
102While request submission and execution is fully asynchronous, result
103processing is not and relies on the perl interpreter calling C<poll_cb>
104(or another function with the same effect).
105
106=item result
107
108The request results are processed synchronously by C<poll_cb>.
109
110The C<poll_cb> function will process all outstanding aio requests by
111calling their callbacks, freeing memory associated with them and managing
112any groups they are contained in.
113
114=item done
115
116Request has reached the end of its lifetime and holds no resources anymore
117(except possibly for the Perl object, but its connection to the actual
118aio request is severed and calling its methods will either do nothing or
119result in a runtime error).
68 120
69=cut 121=cut
70 122
71package IO::AIO; 123package IO::AIO;
72 124
76use base 'Exporter'; 128use base 'Exporter';
77 129
78BEGIN { 130BEGIN {
79 our $VERSION = '2.0'; 131 our $VERSION = '2.0';
80 132
81 our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat 133 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
82 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink 134 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
83 aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move 135 aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
84 aio_group aio_nop); 136 aio_group aio_nop);
85 our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); 137 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
138 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
139 min_parallel max_parallel nreqs);
86 140
87 @IO::AIO::GRP::ISA = 'IO::AIO::REQ'; 141 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
88 142
89 require XSLoader; 143 require XSLoader;
90 XSLoader::load ("IO::AIO", $VERSION); 144 XSLoader::load ("IO::AIO", $VERSION);
121environment, d) use Glib::filename_from_unicode on unicode filenames or e) 175environment, d) use Glib::filename_from_unicode on unicode filenames or e)
122use something else. 176use something else.
123 177
124=over 4 178=over 4
125 179
180=item aioreq_pri $pri
181
182Sets the priority for the next aio request. The default priority
183is C<0>, the minimum and maximum priorities are C<-4> and C<4>,
184respectively. Requests with higher priority will be serviced first.
185
186The priority will be reset to C<0> after each call to one of the C<aio_>
187functions.
188
189Example: open a file with low priority, then read something from it with
190higher priority so the read request is serviced before other low priority
191open requests (potentially spamming the cache):
192
193 aioreq_pri -3;
194 aio_open ..., sub {
195 return unless $_[0];
196
197 aioreq_pri -2;
198 aio_read $_[0], ..., sub {
199 ...
200 };
201 };
202
203=item aioreq_nice $pri_adjust
204
205Similar to C<aioreq_pri>, but subtracts the given value from the current
206priority, so effects are cumulative.
207
126=item aio_open $pathname, $flags, $mode, $callback->($fh) 208=item aio_open $pathname, $flags, $mode, $callback->($fh)
127 209
128Asynchronously open or create a file and call the callback with a newly 210Asynchronously open or create a file and call the callback with a newly
129created filehandle for the file. 211created filehandle for the file.
130 212
181 $_[0] > 0 or die "read error: $!"; 263 $_[0] > 0 or die "read error: $!";
182 print "read $_[0] bytes: <$buffer>\n"; 264 print "read $_[0] bytes: <$buffer>\n";
183 }; 265 };
184 266
185=item aio_move $srcpath, $dstpath, $callback->($status) 267=item aio_move $srcpath, $dstpath, $callback->($status)
186
187[EXPERIMENTAL due to internal aio_group use]
188 268
189Try to move the I<file> (directories not supported as either source or 269Try to move the I<file> (directories not supported as either source or
190destination) from C<$srcpath> to C<$dstpath> and call the callback with 270destination) from C<$srcpath> to C<$dstpath> and call the callback with
191the C<0> (error) or C<-1> ok. 271the C<0> (error) or C<-1> ok.
192 272
345The callback a single argument which is either C<undef> or an array-ref 425The callback a single argument which is either C<undef> or an array-ref
346with the filenames. 426with the filenames.
347 427
348=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 428=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
349 429
350[EXPERIMENTAL due to internal aio_group use]
351
352Scans a directory (similar to C<aio_readdir>) but additionally tries to 430Scans a directory (similar to C<aio_readdir>) but additionally tries to
353separate the entries of directory C<$path> into two sets of names, ones 431efficiently separate the entries of directory C<$path> into two sets of
354you can recurse into (directories or links to them), and ones you cannot 432names, directories you can recurse into (directories), and ones you cannot
355recurse into (everything else). 433recurse into (everything else, including symlinks to directories).
356 434
357C<aio_scandir> is a composite request that creates of many sub requests_ 435C<aio_scandir> is a composite request that creates of many sub requests_
358C<$maxreq> specifies the maximum number of outstanding aio requests that 436C<$maxreq> specifies the maximum number of outstanding aio requests that
359this function generates. If it is C<< <= 0 >>, then a suitable default 437this function generates. If it is C<< <= 0 >>, then a suitable default
360will be chosen (currently 6). 438will be chosen (currently 6).
442 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length], 520 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
443 @$entries]; 521 @$entries];
444 522
445 my (@dirs, @nondirs); 523 my (@dirs, @nondirs);
446 524
447 my ($statcb, $schedcb);
448 my $nreq = 0;
449
450 my $statgrp = add $grp aio_group; 525 my $statgrp = add $grp aio_group sub {
526 $grp->result (\@dirs, \@nondirs);
527 };
451 528
452 $schedcb = sub { 529 limit $statgrp $maxreq;
453 if (@$entries) { 530 feed $statgrp sub {
454 if ($nreq < $maxreq) { 531 return unless @$entries;
455 my $ent = pop @$entries; 532 my $entry = pop @$entries;
533
534 add $statgrp aio_stat "$path/$entry/.", sub {
535 if ($_[0] < 0) {
536 push @nondirs, $entry;
537 } else {
538 # need to check for real directory
539 add $statgrp aio_lstat "$path/$entry", sub {
540 if (-d _) {
541 push @dirs, $entry;
542
543 unless (--$ndirs) {
544 push @nondirs, @$entries;
545 feed $statgrp;
546 }
547 } else {
548 push @nondirs, $entry;
549 }
456 $nreq++; 550 }
457 add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
458 } 551 }
459 } elsif (!$nreq) {
460 # finished
461 $statgrp->cancel;
462 undef $statcb;
463 undef $schedcb;
464 $grp->result (\@dirs, \@nondirs);
465 } 552 };
466 }; 553 };
467 $statcb = sub {
468 my ($status, $entry) = @_;
469
470 if ($status < 0) {
471 $nreq--;
472 push @nondirs, $entry;
473 &$schedcb;
474 } else {
475 # need to check for real directory
476 add $grp aio_lstat "$path/$entry", sub {
477 $nreq--;
478
479 if (-d _) {
480 push @dirs, $entry;
481
482 if (!--$ndirs) {
483 push @nondirs, @$entries;
484 $entries = [];
485 }
486 } else {
487 push @nondirs, $entry;
488 }
489
490 &$schedcb;
491 }
492 }
493 };
494
495 &$schedcb while @$entries && $nreq < $maxreq;
496 }; 554 };
497 }; 555 };
498 }; 556 };
499 557
500 $grp 558 $grp
513If this call isn't available because your OS lacks it or it couldn't be 571If this call isn't available because your OS lacks it or it couldn't be
514detected, it will be emulated by calling C<fsync> instead. 572detected, it will be emulated by calling C<fsync> instead.
515 573
516=item aio_group $callback->(...) 574=item aio_group $callback->(...)
517 575
518[EXPERIMENTAL]
519
520This is a very special aio request: Instead of doing something, it is a 576This is a very special aio request: Instead of doing something, it is a
521container for other aio requests, which is useful if you want to bundle 577container for other aio requests, which is useful if you want to bundle
522many requests into a single, composite, request. 578many requests into a single, composite, request with a definite callback
579and the ability to cancel the whole request with its subrequests.
523 580
524Returns an object of class L<IO::AIO::GRP>. See its documentation below 581Returns an object of class L<IO::AIO::GRP>. See its documentation below
525for more info. 582for more info.
526 583
527Example: 584Example:
546phase and still requires a worker thread. Thus, the callback will not 603phase and still requires a worker thread. Thus, the callback will not
547be executed immediately but only after other requests in the queue have 604be executed immediately but only after other requests in the queue have
548entered their execution phase. This can be used to measure request 605entered their execution phase. This can be used to measure request
549latency. 606latency.
550 607
551=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED* 608=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
552 609
553Mainly used for debugging and benchmarking, this aio request puts one of 610Mainly used for debugging and benchmarking, this aio request puts one of
554the request workers to sleep for the given time. 611the request workers to sleep for the given time.
555 612
556While it is theoretically handy to have simple I/O scheduling requests 613While it is theoretically handy to have simple I/O scheduling requests
557like sleep and file handle readable/writable, the overhead this creates 614like sleep and file handle readable/writable, the overhead this creates is
558is immense, so do not use this function except to put your application 615immense (it blocks a thread for a long time) so do not use this function
559under artificial I/O pressure. 616except to put your application under artificial I/O pressure.
560 617
561=back 618=back
562 619
563=head2 IO::AIO::REQ CLASS 620=head2 IO::AIO::REQ CLASS
564 621
565All non-aggregate C<aio_*> functions return an object of this class when 622All non-aggregate C<aio_*> functions return an object of this class when
566called in non-void context. 623called in non-void context.
567
568A request always moves through the following five states in its lifetime,
569in order: B<ready> (request has been created, but has not been executed
570yet), B<execute> (request is currently being executed), B<pending>
571(request has been executed but callback has not been called yet),
572B<result> (results are being processed synchronously, includes calling the
573callback) and B<done> (request has reached the end of its lifetime and
574holds no resources anymore).
575 624
576=over 4 625=over 4
577 626
578=item cancel $req 627=item cancel $req
579 628
633=item * They can also can also be added to other IO::AIO::GRP objects. 682=item * They can also can also be added to other IO::AIO::GRP objects.
634 683
635=item * You must not add requests to a group from within the group callback (or 684=item * You must not add requests to a group from within the group callback (or
636any later time). 685any later time).
637 686
638=item * This does not harmonise well with C<max_outstanding>, so best do
639not combine C<aio_group> with it. Groups and feeders are recommended for
640this kind of concurrency-limiting.
641
642=back 687=back
643 688
644Their lifetime, simplified, looks like this: when they are empty, they 689Their lifetime, simplified, looks like this: when they are empty, they
645will finish very quickly. If they contain only requests that are in the 690will finish very quickly. If they contain only requests that are in the
646C<done> state, they will also finish. Otherwise they will continue to 691C<done> state, they will also finish. Otherwise they will continue to
661be added, including other groups, as long as you do not create circular 706be added, including other groups, as long as you do not create circular
662dependencies. 707dependencies.
663 708
664Returns all its arguments. 709Returns all its arguments.
665 710
711=item $grp->cancel_subs
712
713Cancel all subrequests and clears any feeder, but not the group request
714itself. Useful when you queued a lot of events but got a result early.
715
666=item $grp->result (...) 716=item $grp->result (...)
667 717
668Set the result value(s) that will be passed to the group callback when all 718Set the result value(s) that will be passed to the group callback when all
669subrequests have finished. By default, no argument will be passed. 719subrequests have finished. By default, no argument will be passed.
670 720
671=item feed $grp $callback->($grp) 721=item feed $grp $callback->($grp)
672
673[VERY EXPERIMENTAL]
674 722
675Sets a feeder/generator on this group: every group can have an attached 723Sets a feeder/generator on this group: every group can have an attached
676generator that generates requests if idle. The idea behind this is that, 724generator that generates requests if idle. The idea behind this is that,
677although you could just queue as many requests as you want in a group, 725although you could just queue as many requests as you want in a group,
678this might starve other requests for a potentially long time. For 726this might starve other requests for a potentially long time. For
679example, C<aio_scandir> might generate hundreds of thousands C<aio_stat> 727example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
680requests, delaying any later requests for a long time. 728requests, delaying any later requests for a long time.
681 729
682To avoid this, and allow incremental generation of requests, you can 730To avoid this, and allow incremental generation of requests, you can
683instead a group and set a feeder on it that generates those requests. The 731instead a group and set a feeder on it that generates those requests. The
684feed callback will be called whenever there are few enough (see C<feed_limit>, 732feed callback will be called whenever there are few enough (see C<limit>,
685below) requests active in the group itself and is expected to queue more 733below) requests active in the group itself and is expected to queue more
686requests. 734requests.
687 735
688The feed can queue as many requests as it likes (i.e. C<add> does not 736The feed callback can queue as many requests as it likes (i.e. C<add> does
689impose any limits). 737not impose any limits).
690 738
691If the feed does not queue more requests when called, it will be 739If the feed does not queue more requests when called, it will be
692automatically removed from the group. 740automatically removed from the group.
693 741
694If the feed limit is C<0>, it will be set to C<2> automatically. 742If the feed limit is C<0>, it will be set to C<2> automatically.
696Example: 744Example:
697 745
698 # stat all files in @files, but only ever use four aio requests concurrently: 746 # stat all files in @files, but only ever use four aio requests concurrently:
699 747
700 my $grp = aio_group sub { print "finished\n" }; 748 my $grp = aio_group sub { print "finished\n" };
701 feed_limit $grp 4; 749 limit $grp 4;
702 feed $grp sub { 750 feed $grp sub {
703 my $file = pop @files 751 my $file = pop @files
704 or return; 752 or return;
705 753
706 add $grp aio_stat $file, sub { ... }; 754 add $grp aio_stat $file, sub { ... };
707 }; 755 };
708 756
709=item feed_limit $grp $num 757=item limit $grp $num
710 758
711Sets the feeder limit for the group: The feeder will be called whenever 759Sets the feeder limit for the group: The feeder will be called whenever
712the group contains less than this many requests. 760the group contains less than this many requests.
713 761
714Setting the limit to C<0> will pause the feeding process. 762Setting the limit to C<0> will pause the feeding process.
732 780
733Process all outstanding events on the result pipe. You have to call this 781Process all outstanding events on the result pipe. You have to call this
734regularly. Returns the number of events processed. Returns immediately 782regularly. Returns the number of events processed. Returns immediately
735when no events are outstanding. 783when no events are outstanding.
736 784
785If not all requests were processed for whatever reason, the filehandle
786will still be ready when C<poll_cb> returns.
787
737Example: Install an Event watcher that automatically calls 788Example: Install an Event watcher that automatically calls
738IO::AIO::poll_cb with high priority: 789IO::AIO::poll_cb with high priority:
739 790
740 Event->io (fd => IO::AIO::poll_fileno, 791 Event->io (fd => IO::AIO::poll_fileno,
741 poll => 'r', async => 1, 792 poll => 'r', async => 1,
742 cb => \&IO::AIO::poll_cb); 793 cb => \&IO::AIO::poll_cb);
794
795=item IO::AIO::poll_some $max_requests
796
797Similar to C<poll_cb>, but only processes up to C<$max_requests> requests
798at a time.
799
800Useful if you want to ensure some level of interactiveness when perl is
801not fast enough to process all requests in time.
802
803Example: Install an Event watcher that automatically calls
804IO::AIO::poll_some with low priority, to ensure that other parts of the
805program get the CPU sometimes even under high AIO load.
806
807 Event->io (fd => IO::AIO::poll_fileno,
808 poll => 'r', nice => 1,
809 cb => sub { IO::AIO::poll_some 256 });
743 810
744=item IO::AIO::poll_wait 811=item IO::AIO::poll_wait
745 812
746Wait till the result filehandle becomes ready for reading (simply does a 813Wait till the result filehandle becomes ready for reading (simply does a
747C<select> on the filehandle. This is useful if you want to synchronously wait 814C<select> on the filehandle. This is useful if you want to synchronously wait
807This module automatically runs C<max_parallel 0> at program end, to ensure 874This module automatically runs C<max_parallel 0> at program end, to ensure
808that all threads are killed and that there are no outstanding requests. 875that all threads are killed and that there are no outstanding requests.
809 876
810Under normal circumstances you don't need to call this function. 877Under normal circumstances you don't need to call this function.
811 878
812=item $oldnreqs = IO::AIO::max_outstanding $nreqs 879=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
813 880
814[DEPRECATED] 881This is a very bad function to use in interactive programs because it
882blocks, and a bad way to reduce concurrency because it is inexact: Better
883use an C<aio_group> together with a feed callback.
815 884
816Sets the maximum number of outstanding requests to C<$nreqs>. If you 885Sets the maximum number of outstanding requests to C<$nreqs>. If you
817try to queue up more than this number of requests, the caller will block until 886to queue up more than this number of requests, the next call to the
818some requests have been handled. 887C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
888function will block until the limit is no longer exceeded.
819 889
820The default is very large, so normally there is no practical limit. If you 890The default value is very large, so there is no practical limit on the
821queue up many requests in a loop it often improves speed if you set 891number of outstanding requests.
822this to a relatively low number, such as C<100>.
823 892
824This function does not work well together with C<aio_group>'s, and their 893You can still queue as many requests as you want. Therefore,
825feeder interface is better suited to limiting concurrency, so do not use 894C<max_oustsanding> is mainly useful in simple scripts (with low values) or
826this function. 895as a stop gap to shield against fatal memory overflow (with large values).
827
828Under normal circumstances you don't need to call this function.
829 896
830=back 897=back
831 898
832=cut 899=cut
833 900
860This module should do "the right thing" when the process using it forks: 927This module should do "the right thing" when the process using it forks:
861 928
862Before the fork, IO::AIO enters a quiescent state where no requests 929Before the fork, IO::AIO enters a quiescent state where no requests
863can be added in other threads and no results will be processed. After 930can be added in other threads and no results will be processed. After
864the fork the parent simply leaves the quiescent state and continues 931the fork the parent simply leaves the quiescent state and continues
865request/result processing, while the child clears the request/result 932request/result processing, while the child frees the request/result queue
866queue (so the requests started before the fork will only be handled in 933(so that the requests started before the fork will only be handled in the
867the parent). Threads will be started on demand until the limit ste in the 934parent). Threads will be started on demand until the limit set in the
868parent process has been reached again. 935parent process has been reached again.
869 936
870In short: the parent will, after a short pause, continue as if fork had 937In short: the parent will, after a short pause, continue as if fork had
871not been called, while the child will act as if IO::AIO has not been used 938not been called, while the child will act as if IO::AIO has not been used
872yet. 939yet.
873 940
874=head2 MEMORY USAGE 941=head2 MEMORY USAGE
875 942
943Per-request usage:
944
876Each aio request uses - depending on your architecture - around 128 bytes 945Each aio request uses - depending on your architecture - around 100-200
877of memory. In addition, stat requests need a stat buffer (possibly a few 946bytes of memory. In addition, stat requests need a stat buffer (possibly
878hundred bytes). Perl scalars and other data passed into aio requests will 947a few hundred bytes), readdir requires a result buffer and so on. Perl
879also be locked. 948scalars and other data passed into aio requests will also be locked and
949will consume memory till the request has entered the done state.
880 950
881This is now awfully much, so queuing lots of requests is not usually a 951This is now awfully much, so queuing lots of requests is not usually a
882problem. 952problem.
883 953
884Each thread needs a stack area which is usually around 16k, sometimes much 954Per-thread usage:
885larger, depending on the OS. 955
956In the execution phase, some aio requests require more memory for
957temporary buffers, and each thread requires a stack and other data
958structures (usually around 16k-128k, depending on the OS).
959
960=head1 KNOWN BUGS
961
962Known bugs will be fixed in the next release.
886 963
887=head1 SEE ALSO 964=head1 SEE ALSO
888 965
889L<Coro>, L<Linux::AIO> (obsolete). 966L<Coro::AIO>.
890 967
891=head1 AUTHOR 968=head1 AUTHOR
892 969
893 Marc Lehmann <schmorp@schmorp.de> 970 Marc Lehmann <schmorp@schmorp.de>
894 http://home.schmorp.de/ 971 http://home.schmorp.de/

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