[ViewVC] Diff of: cvs/IO-AIO/AIO.pm

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.55 by root, Sun Oct 22 00:49:29 2006 UTC vs.
Revision 1.75 by root, Tue Oct 24 20:10:26 2006 UTC

…		…
15		15
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	16	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	17	$_[0] > 0 or die "read error: $!";
18	};	18	};
19		19
20	use IO::AIO 2; # version has aio objects	20	# version 2+ has request and group objects
		21	use IO::AIO 2;
21		22
		23	aioreq_pri 4; # give next request a very high priority
22	my $req = aio_unlink "/tmp/file", sub { };	24	my $req = aio_unlink "/tmp/file", sub { };
23	$req->cancel; # cancel request if still in queue	25	$req->cancel; # cancel request if still in queue
24		26
25	# AnyEvent	27	my $grp = aio_group sub { print "all stats done\n" };
		28	add $grp aio_stat "..." for ...;
		29
		30	# AnyEvent integration
26	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
27	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });	32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
28		33
29	# Event	34	# Event integration
30	Event->io (fd => IO::AIO::poll_fileno,	35	Event->io (fd => IO::AIO::poll_fileno,
31	poll => 'r',	36	poll => 'r',
32	cb => \&IO::AIO::poll_cb);	37	cb => \&IO::AIO::poll_cb);
33		38
34	# Glib/Gtk2	39	# Glib/Gtk2 integration
35	add_watch Glib::IO IO::AIO::poll_fileno,	40	add_watch Glib::IO IO::AIO::poll_fileno,
36	in => sub { IO::AIO::poll_cb; 1 };	41	in => sub { IO::AIO::poll_cb; 1 };
37		42
38	# Tk	43	# Tk integration
39	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
40	readable => \&IO::AIO::poll_cb);	45	readable => \&IO::AIO::poll_cb);
41		46
42	# Danga::Socket	47	# Danga::Socket integration
43	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
44	\&IO::AIO::poll_cb);	49	\&IO::AIO::poll_cb);
45		50
46
47	=head1 DESCRIPTION	51	=head1 DESCRIPTION
48		52
49	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
50	operating system supports.	54	operating system supports.
51		55
52	Currently, a number of threads are started that execute your read/writes	56	In this version, a number of threads are started that execute your
53	and signal their completion. You don't need thread support in your libc or	57	requests and signal their completion. You don't need thread support
54	perl, and the threads created by this module will not be visible to the	58	in perl, and the threads created by this module will not be visible
55	pthreads library. In the future, this module might make use of the native	59	to perl. In the future, this module might make use of the native aio
56	aio functions available on many operating systems. However, they are often	60	functions available on many operating systems. However, they are often
57	not well-supported (Linux doesn't allow them on normal files currently,	61	not well-supported or restricted (Linux doesn't allow them on normal
58	for example), and they would only support aio_read and aio_write, so the	62	files currently, for example), and they would only support aio_read and
59	remaining functionality would have to be implemented using threads anyway.	63	aio_write, so the remaining functionality would have to be implemented
		64	using threads anyway.
60		65
61	Although the module will work with in the presence of other threads, it is	66	Although the module will work with in the presence of other (Perl-)
62	currently not reentrant, so use appropriate locking yourself, always call	67	threads, it is currently not reentrant in any way, so use appropriate
63	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	68	locking yourself, always call C<poll_cb> from within the same thread, or
64	C<aio_> functions) recursively.	69	never call C<poll_cb> (or other C<aio_> functions) recursively.
		70
		71	=head1 REQUEST ANATOMY AND LIFETIME
		72
		73	Every C<aio_*> function creates a request. which is a C data structure not
		74	directly visible to Perl.
		75
		76	If called in non-void context, every request function returns a Perl
		77	object representing the request. In void context, nothing is returned,
		78	which saves a bit of memory.
		79
		80	The perl object is a fairly standard ref-to-hash object. The hash contents
		81	are not used by IO::AIO so you are free to store anything you like in it.
		82
		83	During their existance, aio requests travel through the following states,
		84	in order:
		85
		86	=over 4
		87
		88	=item ready
		89
		90	Immediately after a request is created it is put into the ready state,
		91	waiting for a thread to execute it.
		92
		93	=item execute
		94
		95	A thread has accepted the request for processing and is currently
		96	executing it (e.g. blocking in read).
		97
		98	=item pending
		99
		100	The request has been executed and is waiting for result processing.
		101
		102	While request submission and execution is fully asynchronous, result
		103	processing 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
		108	The request results are processed synchronously by C<poll_cb>.
		109
		110	The C<poll_cb> function will process all outstanding aio requests by
		111	calling their callbacks, freeing memory associated with them and managing
		112	any groups they are contained in.
		113
		114	=item done
		115
		116	Request 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
		118	aio request is severed and calling its methods will either do nothing or
		119	result in a runtime error).
65		120
66	=cut	121	=cut
67		122
68	package IO::AIO;	123	package IO::AIO;
69		124
…		…
73	use base 'Exporter';	128	use base 'Exporter';
74		129
75	BEGIN {	130	BEGIN {
76	our $VERSION = '2.0';	131	our $VERSION = '2.0';
77		132
78	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
79	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
80	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
81	aio_group);	136	aio_group aio_nop);
82	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 max_outstanding nreqs);
83		140
84	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
85		142
86	require XSLoader;	143	require XSLoader;
87	XSLoader::load ("IO::AIO", $VERSION);	144	XSLoader::load ("IO::AIO", $VERSION);
…		…
118	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	175	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
119	use something else.	176	use something else.
120		177
121	=over 4	178	=over 4
122		179
		180	=item aioreq_pri $pri
		181
		182	Sets the priority for the next aio request. The default priority
		183	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,
		184	respectively. Requests with higher priority will be serviced first.
		185
		186	The priority will be reset to C<0> after each call to one of the C<aio_>
		187	functions.
		188
		189	Example: open a file with low priority, then read something from it with
		190	higher priority so the read request is serviced before other low priority
		191	open 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
		205	Similar to C<aioreq_pri>, but subtracts the given value from the current
		206	priority, so effects are cumulative.
		207
123	=item aio_open $pathname, $flags, $mode, $callback->($fh)	208	=item aio_open $pathname, $flags, $mode, $callback->($fh)
124		209
125	Asynchronously open or create a file and call the callback with a newly	210	Asynchronously open or create a file and call the callback with a newly
126	created filehandle for the file.	211	created filehandle for the file.
127		212
…		…
198	=cut	283	=cut
199		284
200	sub aio_move($$$) {	285	sub aio_move($$$) {
201	my ($src, $dst, $cb) = @_;	286	my ($src, $dst, $cb) = @_;
202		287
203	my $grp = aio_group;	288	my $grp = aio_group $cb;
204		289
205	add $grp aio_rename $src, $dst, sub {	290	add $grp aio_rename $src, $dst, sub {
206	if ($_[0] && $! == EXDEV) {	291	if ($_[0] && $! == EXDEV) {
207	add $grp aio_open $src, O_RDONLY, 0, sub {	292	add $grp aio_open $src, O_RDONLY, 0, sub {
208	if (my $src_fh = $_[0]) {	293	if (my $src_fh = $_[0]) {
…		…
218	chmod $stat[2] & 07777, $dst_fh;	303	chmod $stat[2] & 07777, $dst_fh;
219	chown $stat[4], $stat[5], $dst_fh;	304	chown $stat[4], $stat[5], $dst_fh;
220	close $dst_fh;	305	close $dst_fh;
221		306
222	add $grp aio_unlink $src, sub {	307	add $grp aio_unlink $src, sub {
223	$cb->($_[0]);	308	$grp->result ($_[0]);
224	};	309	};
225	} else {	310	} else {
226	my $errno = $!;	311	my $errno = $!;
227	add $grp aio_unlink $dst, sub {	312	add $grp aio_unlink $dst, sub {
228	$! = $errno;	313	$! = $errno;
229	$cb->(-1);	314	$grp->result (-1);
230	};	315	};
231	}	316	}
232	};	317	};
233	} else {	318	} else {
234	$cb->(-1);	319	$grp->result (-1);
235	}	320	}
236	},	321	},
237		322
238	} else {	323	} else {
239	$cb->(-1);	324	$grp->result (-1);
240	}	325	}
241	};	326	};
242	} else {	327	} else {
243	$cb->($_[0]);	328	$grp->result ($_[0]);
244	}	329	}
245	};	330	};
246		331
247	$grp	332	$grp
248	}	333	}
…		…
345	Scans a directory (similar to C<aio_readdir>) but additionally tries to	430	Scans a directory (similar to C<aio_readdir>) but additionally tries to
346	separate the entries of directory C<$path> into two sets of names, ones	431	separate the entries of directory C<$path> into two sets of names, ones
347	you can recurse into (directories or links to them), and ones you cannot	432	you can recurse into (directories or links to them), and ones you cannot
348	recurse into (everything else).	433	recurse into (everything else).
349		434
350	C<aio_scandir> is a composite request that consists of many sub	435	C<aio_scandir> is a composite request that creates of many sub requests_
351	requests. C<$maxreq> specifies the maximum number of outstanding aio	436	C<$maxreq> specifies the maximum number of outstanding aio requests that
352	requests that this function generates. If it is C<< <= 0 >>, then a	437	this function generates. If it is C<< <= 0 >>, then a suitable default
353	suitable default will be chosen (currently 8).	438	will be chosen (currently 6).
354		439
355	On error, the callback is called without arguments, otherwise it receives	440	On error, the callback is called without arguments, otherwise it receives
356	two array-refs with path-relative entry names.	441	two array-refs with path-relative entry names.
357		442
358	Example:	443	Example:
…		…
395	=cut	480	=cut
396		481
397	sub aio_scandir($$$) {	482	sub aio_scandir($$$) {
398	my ($path, $maxreq, $cb) = @_;	483	my ($path, $maxreq, $cb) = @_;
399		484
400	my $grp = aio_group;	485	my $grp = aio_group $cb;
401		486
402	$maxreq = 8 if $maxreq <= 0;	487	$maxreq = 6 if $maxreq <= 0;
403		488
404	# stat once	489	# stat once
405	add $grp aio_stat $path, sub {	490	add $grp aio_stat $path, sub {
406	return $cb->() if $_[0];	491	return $grp->result () if $_[0];
407	my $now = time;	492	my $now = time;
408	my $hash1 = join ":", (stat _)[0,1,3,7,9];	493	my $hash1 = join ":", (stat _)[0,1,3,7,9];
409		494
410	# read the directory entries	495	# read the directory entries
411	add $grp aio_readdir $path, sub {	496	add $grp aio_readdir $path, sub {
412	my $entries = shift	497	my $entries = shift
413	or return $cb->();	498	or return $grp->result ();
414		499
415	# stat the dir another time	500	# stat the dir another time
416	add $grp aio_stat $path, sub {	501	add $grp aio_stat $path, sub {
417	my $hash2 = join ":", (stat _)[0,1,3,7,9];	502	my $hash2 = join ":", (stat _)[0,1,3,7,9];
418		503
…		…
423	$ndirs = -1;	508	$ndirs = -1;
424	} else {	509	} else {
425	# if nlink == 2, we are finished	510	# if nlink == 2, we are finished
426	# on non-posix-fs's, we rely on nlink < 2	511	# on non-posix-fs's, we rely on nlink < 2
427	$ndirs = (stat _)[3] - 2	512	$ndirs = (stat _)[3] - 2
428	or return $cb->([], $entries);	513	or return $grp->result ([], $entries);
429	}	514	}
430		515
431	# sort into likely dirs and likely nondirs	516	# sort into likely dirs and likely nondirs
432	# dirs == files without ".", short entries first	517	# dirs == files without ".", short entries first
433	$entries = [map $_->[0],	518	$entries = [map $_->[0],
…		…
435	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	520	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
436	@$entries];	521	@$entries];
437		522
438	my (@dirs, @nondirs);	523	my (@dirs, @nondirs);
439		524
440	my ($statcb, $schedcb);	525	my $statgrp = add $grp aio_group sub {
441	my $nreq = 0;	526	$grp->result (\@dirs, \@nondirs);
		527	};
442		528
443	$schedcb = sub {	529	limit $statgrp $maxreq;
444	if (@$entries) {	530	feed $statgrp sub {
445	if ($nreq < $maxreq) {	531	return unless @$entries;
446	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	}
447	$nreq++;	550	}
448	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
449	}	551	}
450	} elsif (!$nreq) {
451	# finished
452	undef $statcb;
453	undef $schedcb;
454	$cb->(\@dirs, \@nondirs) if $cb;
455	undef $cb;
456	}	552	};
457	};	553	};
458	$statcb = sub {
459	my ($status, $entry) = @_;
460
461	if ($status < 0) {
462	$nreq--;
463	push @nondirs, $entry;
464	&$schedcb;
465	} else {
466	# need to check for real directory
467	add $grp aio_lstat "$path/$entry", sub {
468	$nreq--;
469
470	if (-d _) {
471	push @dirs, $entry;
472
473	if (!--$ndirs) {
474	push @nondirs, @$entries;
475	$entries = [];
476	}
477	} else {
478	push @nondirs, $entry;
479	}
480
481	&$schedcb;
482	}
483	}
484	};
485
486	&$schedcb while @$entries && $nreq < $maxreq;
487	};	554	};
488	};	555	};
489	};	556	};
490		557
491	$grp	558	$grp
…		…
502	callback with the fdatasync result code.	569	callback with the fdatasync result code.
503		570
504	If this call isn't available because your OS lacks it or it couldn't be	571	If this call isn't available because your OS lacks it or it couldn't be
505	detected, it will be emulated by calling C<fsync> instead.	572	detected, it will be emulated by calling C<fsync> instead.
506		573
507	=item aio_group $callback->()	574	=item aio_group $callback->(...)
508
509	[EXPERIMENTAL]
510		575
511	This is a very special aio request: Instead of doing something, it is a	576	This is a very special aio request: Instead of doing something, it is a
512	container for other aio requests, which is useful if you want to bundle	577	container for other aio requests, which is useful if you want to bundle
513	many requests into a single, composite, request.	578	many requests into a single, composite, request with a definite callback
		579	and the ability to cancel the whole request with its subrequests.
514		580
515	Returns an object of class L<IO::AIO::GRP>. See its documentation below	581	Returns an object of class L<IO::AIO::GRP>. See its documentation below
516	for more info.	582	for more info.
517		583
518	Example:	584	Example:
…		…
524	add $grp	590	add $grp
525	(aio_stat ...),	591	(aio_stat ...),
526	(aio_stat ...),	592	(aio_stat ...),
527	...;	593	...;
528		594
		595	=item aio_nop $callback->()
		596
		597	This is a special request - it does nothing in itself and is only used for
		598	side effects, such as when you want to add a dummy request to a group so
		599	that finishing the requests in the group depends on executing the given
		600	code.
		601
		602	While this request does nothing, it still goes through the execution
		603	phase and still requires a worker thread. Thus, the callback will not
		604	be executed immediately but only after other requests in the queue have
		605	entered their execution phase. This can be used to measure request
		606	latency.
		607
529	=item aio_sleep $fractional_seconds, $callback->() NOT EXPORTED	608	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
530		609
531	Mainly used for debugging and benchmarking, this aio request puts one of	610	Mainly used for debugging and benchmarking, this aio request puts one of
532	the request workers to sleep for the given time.	611	the request workers to sleep for the given time.
533		612
		613	While it is theoretically handy to have simple I/O scheduling requests
		614	like sleep and file handle readable/writable, the overhead this creates is
		615	immense (it blocks a thread for a long time) so do not use this function
		616	except to put your application under artificial I/O pressure.
		617
534	=back	618	=back
535		619
536	=head2 IO::AIO::REQ CLASS	620	=head2 IO::AIO::REQ CLASS
537		621
538	All non-aggregate C<aio_*> functions return an object of this class when	622	All non-aggregate C<aio_*> functions return an object of this class when
539	called in non-void context.	623	called in non-void context.
540		624
541	A request always moves through the following five states in its lifetime,
542	in order: B<ready> (request has been created, but has not been executed
543	yet), B<execute> (request is currently being executed), B<pending>
544	(request has been executed but callback has not been called yet),
545	B<result> (results are being processed synchronously, includes calling the
546	callback) and B<done> (request has reached the end of its lifetime and
547	holds no resources anymore).
548
549	=over 4	625	=over 4
550		626
551	=item $req->cancel	627	=item cancel $req
552		628
553	Cancels the request, if possible. Has the effect of skipping execution	629	Cancels the request, if possible. Has the effect of skipping execution
554	when entering the B<execute> state and skipping calling the callback when	630	when entering the B<execute> state and skipping calling the callback when
555	entering the the B<result> state, but will leave the request otherwise	631	entering the the B<result> state, but will leave the request otherwise
556	untouched. That means that requests that currently execute will not be	632	untouched. That means that requests that currently execute will not be
557	stopped and resources held by the request will not be freed prematurely.	633	stopped and resources held by the request will not be freed prematurely.
558		634
		635	=item cb $req $callback->(...)
		636
		637	Replace (or simply set) the callback registered to the request.
		638
559	=back	639	=back
560		640
561	=head2 IO::AIO::GRP CLASS	641	=head2 IO::AIO::GRP CLASS
562		642
563	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to	643	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
…		…
577	You add requests by calling the C<add> method with one or more	657	You add requests by calling the C<add> method with one or more
578	C<IO::AIO::REQ> objects:	658	C<IO::AIO::REQ> objects:
579		659
580	$grp->add (aio_unlink "...");	660	$grp->add (aio_unlink "...");
581		661
582	add $grp aio_stat "...", sub { ... };	662	add $grp aio_stat "...", sub {
		663	$_[0] or return $grp->result ("error");
		664
		665	# add another request dynamically, if first succeeded
		666	add $grp aio_open "...", sub {
		667	$grp->result ("ok");
		668	};
		669	};
583		670
584	This makes it very easy to create composite requests (see the source of	671	This makes it very easy to create composite requests (see the source of
585	C<aio_move> for an application) that work and feel like simple requests.	672	C<aio_move> for an application) that work and feel like simple requests.
586		673
		674	=over 4
		675
587	The IO::AIO::GRP objects will be cleaned up during calls to	676	=item * The IO::AIO::GRP objects will be cleaned up during calls to
588	C<IO::AIO::poll_cb>, just like any other request.	677	C<IO::AIO::poll_cb>, just like any other request.
589		678
590	They can be canceled like any other request. Canceling will cancel not	679	=item * They can be canceled like any other request. Canceling will cancel not
591	just the request itself, but also all requests it contains.	680	only the request itself, but also all requests it contains.
592		681
593	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.
		683
		684	=item * You must not add requests to a group from within the group callback (or
		685	any later time).
		686
		687	=item * This does not harmonise well with C<max_outstanding>, so best do
		688	not combine C<aio_group> with it. Groups and feeders are recommended for
		689	this kind of concurrency-limiting.
		690
		691	=back
594		692
595	Their lifetime, simplified, looks like this: when they are empty, they	693	Their lifetime, simplified, looks like this: when they are empty, they
596	will finish very quickly. If they contain only requests that are in the	694	will finish very quickly. If they contain only requests that are in the
597	C<done> state, they will also finish. Otherwise they will continue to	695	C<done> state, they will also finish. Otherwise they will continue to
598	exist.	696	exist.
599		697
		698	That means after creating a group you have some time to add requests. And
		699	in the callbacks of those requests, you can add further requests to the
		700	group. And only when all those requests have finished will the the group
		701	itself finish.
		702
600	=over 4	703	=over 4
601		704
		705	=item add $grp ...
		706
602	=item $grp->add (...)	707	=item $grp->add (...)
603		708
604	=item add $grp ...	709	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		710	be added, including other groups, as long as you do not create circular
		711	dependencies.
605		712
606	Add one or more	713	Returns all its arguments.
607	Cancels the request, if possible. Has the effect of skipping execution	714
608	when entering the B<execute> state and skipping calling the callback when	715	=item $grp->cancel_subs
609	entering the the B<result> state, but will leave the request otherwise	716
610	untouched. That means that requests that currently execute will not be	717	Cancel all subrequests and clears any feeder, but not the group request
611	stopped and resources held by the request will not be freed prematurely.	718	itself. Useful when you queued a lot of events but got a result early.
		719
		720	=item $grp->result (...)
		721
		722	Set the result value(s) that will be passed to the group callback when all
		723	subrequests have finished. By default, no argument will be passed.
		724
		725	=item feed $grp $callback->($grp)
		726
		727	Sets a feeder/generator on this group: every group can have an attached
		728	generator that generates requests if idle. The idea behind this is that,
		729	although you could just queue as many requests as you want in a group,
		730	this might starve other requests for a potentially long time. For
		731	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		732	requests, delaying any later requests for a long time.
		733
		734	To avoid this, and allow incremental generation of requests, you can
		735	instead a group and set a feeder on it that generates those requests. The
		736	feed callback will be called whenever there are few enough (see C<limit>,
		737	below) requests active in the group itself and is expected to queue more
		738	requests.
		739
		740	The feed callback can queue as many requests as it likes (i.e. C<add> does
		741	not impose any limits).
		742
		743	If the feed does not queue more requests when called, it will be
		744	automatically removed from the group.
		745
		746	If the feed limit is C<0>, it will be set to C<2> automatically.
		747
		748	Example:
		749
		750	# stat all files in @files, but only ever use four aio requests concurrently:
		751
		752	my $grp = aio_group sub { print "finished\n" };
		753	limit $grp 4;
		754	feed $grp sub {
		755	my $file = pop @files
		756	or return;
		757
		758	add $grp aio_stat $file, sub { ... };
		759	};
		760
		761	=item limit $grp $num
		762
		763	Sets the feeder limit for the group: The feeder will be called whenever
		764	the group contains less than this many requests.
		765
		766	Setting the limit to C<0> will pause the feeding process.
612		767
613	=back	768	=back
614		769
615	=head2 SUPPORT FUNCTIONS	770	=head2 SUPPORT FUNCTIONS
616		771
…		…
674	IO::AIO::poll_wait, IO::AIO::poll_cb	829	IO::AIO::poll_wait, IO::AIO::poll_cb
675	if IO::AIO::nreqs;	830	if IO::AIO::nreqs;
676		831
677	=item IO::AIO::min_parallel $nthreads	832	=item IO::AIO::min_parallel $nthreads
678		833
679	Set the minimum number of AIO threads to C<$nthreads>. The current default	834	Set the minimum number of AIO threads to C<$nthreads>. The current
680	is C<4>, which means four asynchronous operations can be done at one time	835	default is C<8>, which means eight asynchronous operations can execute
681	(the number of outstanding operations, however, is unlimited).	836	concurrently at any one time (the number of outstanding requests,
		837	however, is unlimited).
682		838
683	IO::AIO starts threads only on demand, when an AIO request is queued and	839	IO::AIO starts threads only on demand, when an AIO request is queued and
684	no free thread exists.	840	no free thread exists.
685		841
686	It is recommended to keep the number of threads low, as some Linux	842	It is recommended to keep the number of threads relatively low, as some
687	kernel versions will scale negatively with the number of threads (higher	843	Linux kernel versions will scale negatively with the number of threads
688	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	844	(higher parallelity => MUCH higher latency). With current Linux 2.6
689	threads should be fine.	845	versions, 4-32 threads should be fine.
690		846
691	Under most circumstances you don't need to call this function, as the	847	Under most circumstances you don't need to call this function, as the
692	module selects a default that is suitable for low to moderate load.	848	module selects a default that is suitable for low to moderate load.
693		849
694	=item IO::AIO::max_parallel $nthreads	850	=item IO::AIO::max_parallel $nthreads
…		…
705		861
706	Under normal circumstances you don't need to call this function.	862	Under normal circumstances you don't need to call this function.
707		863
708	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	864	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
709		865
		866	[DEPRECATED]
		867
710	Sets the maximum number of outstanding requests to C<$nreqs>. If you	868	Sets the maximum number of outstanding requests to C<$nreqs>. If you
711	try to queue up more than this number of requests, the caller will block until	869	try to queue up more than this number of requests, the caller will block until
712	some requests have been handled.	870	some requests have been handled.
713		871
714	The default is very large, so normally there is no practical limit. If you	872	The default is very large, so normally there is no practical limit. If you
715	queue up many requests in a loop it often improves speed if you set	873	queue up many requests in a loop it often improves speed if you set
716	this to a relatively low number, such as C<100>.	874	this to a relatively low number, such as C<100>.
		875
		876	This function does not work well together with C<aio_group>'s, and their
		877	feeder interface is better suited to limiting concurrency, so do not use
		878	this function.
717		879
718	Under normal circumstances you don't need to call this function.	880	Under normal circumstances you don't need to call this function.
719		881
720	=back	882	=back
721		883
…		…
735	or return undef;	897	or return undef;
736		898
737	*$sym	899	*$sym
738	}	900	}
739		901
740	min_parallel 4;	902	min_parallel 8;
741		903
742	END {	904	END {
743	max_parallel 0;	905	max_parallel 0;
744	}	906	}
745		907
…		…
750	This module should do "the right thing" when the process using it forks:	912	This module should do "the right thing" when the process using it forks:
751		913
752	Before the fork, IO::AIO enters a quiescent state where no requests	914	Before the fork, IO::AIO enters a quiescent state where no requests
753	can be added in other threads and no results will be processed. After	915	can be added in other threads and no results will be processed. After
754	the fork the parent simply leaves the quiescent state and continues	916	the fork the parent simply leaves the quiescent state and continues
755	request/result processing, while the child clears the request/result	917	request/result processing, while the child frees the request/result queue
756	queue (so the requests started before the fork will only be handled in	918	(so that the requests started before the fork will only be handled in the
757	the parent). Threads will be started on demand until the limit ste in the	919	parent). Threads will be started on demand until the limit set in the
758	parent process has been reached again.	920	parent process has been reached again.
759		921
760	In short: the parent will, after a short pause, continue as if fork had	922	In short: the parent will, after a short pause, continue as if fork had
761	not been called, while the child will act as if IO::AIO has not been used	923	not been called, while the child will act as if IO::AIO has not been used
762	yet.	924	yet.
763		925
		926	=head2 MEMORY USAGE
		927
		928	Per-request usage:
		929
		930	Each aio request uses - depending on your architecture - around 100-200
		931	bytes of memory. In addition, stat requests need a stat buffer (possibly
		932	a few hundred bytes), readdir requires a result buffer and so on. Perl
		933	scalars and other data passed into aio requests will also be locked and
		934	will consume memory till the request has entered the done state.
		935
		936	This is now awfully much, so queuing lots of requests is not usually a
		937	problem.
		938
		939	Per-thread usage:
		940
		941	In the execution phase, some aio requests require more memory for
		942	temporary buffers, and each thread requires a stack and other data
		943	structures (usually around 16k-128k, depending on the OS).
		944
		945	=head1 KNOWN BUGS
		946
		947	Known bugs will be fixed in the next release.
		948
764	=head1 SEE ALSO	949	=head1 SEE ALSO
765		950
766	L<Coro>, L<Linux::AIO> (obsolete).	951	L<Coro::AIO>.
767		952
768	=head1 AUTHOR	953	=head1 AUTHOR
769		954
770	Marc Lehmann <schmorp@schmorp.de>	955	Marc Lehmann <schmorp@schmorp.de>
771	http://home.schmorp.de/	956	http://home.schmorp.de/

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Revision 1.55 by root, Sun Oct 22 00:49:29 2006 UTC vs.
Revision 1.75 by root, Tue Oct 24 20:10:26 2006 UTC