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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.42 by root, Mon Dec 26 18:15:23 2005 UTC vs.
Revision 1.68 by root, Tue Oct 24 03:17:39 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	# AnyEvent	20	# version 2+ has request and group objects
		21	use IO::AIO 2;
		22
		23	aioreq_pri 4; # give next request a very high priority
		24	my $req = aio_unlink "/tmp/file", sub { };
		25	$req->cancel; # cancel request if still in queue
		26
		27	my $grp = aio_group sub { print "all stats done\n" };
		28	add $grp aio_stat "..." for ...;
		29
		30	# AnyEvent integration
21	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
22	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 });
23		33
24	# Event	34	# Event integration
25	Event->io (fd => IO::AIO::poll_fileno,	35	Event->io (fd => IO::AIO::poll_fileno,
26	poll => 'r',	36	poll => 'r',
27	cb => \&IO::AIO::poll_cb);	37	cb => \&IO::AIO::poll_cb);
28		38
29	# Glib/Gtk2	39	# Glib/Gtk2 integration
30	add_watch Glib::IO IO::AIO::poll_fileno,	40	add_watch Glib::IO IO::AIO::poll_fileno,
31	in => sub { IO::AIO::poll_cb; 1 };	41	in => sub { IO::AIO::poll_cb; 1 };
32		42
33	# Tk	43	# Tk integration
34	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
35	readable => \&IO::AIO::poll_cb);	45	readable => \&IO::AIO::poll_cb);
36		46
37	# Danga::Socket	47	# Danga::Socket integration
38	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
39	\&IO::AIO::poll_cb);	49	\&IO::AIO::poll_cb);
40		50
41
42	=head1 DESCRIPTION	51	=head1 DESCRIPTION
43		52
44	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
45	operating system supports.	54	operating system supports.
46		55
47	Currently, a number of threads are started that execute your read/writes	56	Currently, a number of threads are started that execute your read/writes
48	and signal their completion. You don't need thread support in your libc or	57	and signal their completion. You don't need thread support in perl, and
49	perl, and the threads created by this module will not be visible to the	58	the threads created by this module will not be visible to perl. In the
50	pthreads library. In the future, this module might make use of the native	59	future, this module might make use of the native aio functions available
51	aio functions available on many operating systems. However, they are often	60	on many operating systems. However, they are often not well-supported
52	not well-supported (Linux doesn't allow them on normal files currently,	61	(Linux doesn't allow them on normal files currently, for example),
53	for example), and they would only support aio_read and aio_write, so the	62	and they would only support aio_read and aio_write, so the remaining
54	remaining functionality would have to be implemented using threads anyway.	63	functionality would have to be implemented using threads anyway.
55		64
56	Although the module will work with in the presence of other threads, it is	65	Although the module will work with in the presence of other threads,
57	currently not reentrant, so use appropriate locking yourself, always call	66	it is currently not reentrant in any way, so use appropriate locking
58	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	67	yourself, always call C<poll_cb> from within the same thread, or never
59	C<aio_> functions) recursively.	68	call C<poll_cb> (or other C<aio_> functions) recursively.
60		69
61	=cut	70	=cut
62		71
63	package IO::AIO;	72	package IO::AIO;
64		73
65	no warnings;	74	no warnings;
		75	use strict 'vars';
66		76
67	use base 'Exporter';	77	use base 'Exporter';
68		78
69	use Fcntl ();
70
71	BEGIN {	79	BEGIN {
72	$VERSION = '1.61';	80	our $VERSION = '2.0';
73		81
74	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	82	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
75	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	83	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
76	aio_fsync aio_fdatasync aio_readahead);	84	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
77	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	85	aio_group aio_nop);
78	max_outstanding nreqs);	86	our @EXPORT = (@AIO_REQ, qw(aioreq_pri));
		87	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		88	min_parallel max_parallel max_outstanding nreqs);
		89
		90	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
79		91
80	require XSLoader;	92	require XSLoader;
81	XSLoader::load IO::AIO, $VERSION;	93	XSLoader::load ("IO::AIO", $VERSION);
82	}	94	}
83		95
84	=head1 FUNCTIONS	96	=head1 FUNCTIONS
85		97
86	=head2 AIO FUNCTIONS	98	=head2 AIO FUNCTIONS
…		…
94	syscall has been executed asynchronously.	106	syscall has been executed asynchronously.
95		107
96	All functions expecting a filehandle keep a copy of the filehandle	108	All functions expecting a filehandle keep a copy of the filehandle
97	internally until the request has finished.	109	internally until the request has finished.
98		110
		111	All requests return objects of type L<IO::AIO::REQ> that allow further
		112	manipulation of those requests while they are in-flight.
		113
99	The pathnames you pass to these routines I<must> be absolute and	114	The pathnames you pass to these routines I<must> be absolute and
100	encoded in byte form. The reason for the former is that at the time the	115	encoded in byte form. The reason for the former is that at the time the
101	request is being executed, the current working directory could have	116	request is being executed, the current working directory could have
102	changed. Alternatively, you can make sure that you never change the	117	changed. Alternatively, you can make sure that you never change the
103	current working directory.	118	current working directory.
…		…
108	your pathnames to the locale (or other) encoding in effect in the user	123	your pathnames to the locale (or other) encoding in effect in the user
109	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	124	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
110	use something else.	125	use something else.
111		126
112	=over 4	127	=over 4
		128
		129	=item aioreq_pri $pri
		130
		131	Sets the priority for the next aio request. The default priority
		132	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,
		133	respectively. Requests with higher priority will be serviced first.
		134
		135	The priority will be reset to C<0> after each call to one of the C<aio_>
		136	functions.
113		137
114	=item aio_open $pathname, $flags, $mode, $callback->($fh)	138	=item aio_open $pathname, $flags, $mode, $callback->($fh)
115		139
116	Asynchronously open or create a file and call the callback with a newly	140	Asynchronously open or create a file and call the callback with a newly
117	created filehandle for the file.	141	created filehandle for the file.
…		…
168	aio_read $fh, 7, 15, $buffer, 0, sub {	192	aio_read $fh, 7, 15, $buffer, 0, sub {
169	$_[0] > 0 or die "read error: $!";	193	$_[0] > 0 or die "read error: $!";
170	print "read $_[0] bytes: <$buffer>\n";	194	print "read $_[0] bytes: <$buffer>\n";
171	};	195	};
172		196
		197	=item aio_move $srcpath, $dstpath, $callback->($status)
		198
		199	[EXPERIMENTAL due to internal aio_group use]
		200
		201	Try to move the I<file> (directories not supported as either source or
		202	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		203	the C<0> (error) or C<-1> ok.
		204
		205	This is a composite request that tries to rename(2) the file first. If
		206	rename files with C<EXDEV>, it creates the destination file with mode 0200
		207	and copies the contents of the source file into it using C<aio_sendfile>,
		208	followed by restoring atime, mtime, access mode and uid/gid, in that
		209	order, and unlinking the C<$srcpath>.
		210
		211	If an error occurs, the partial destination file will be unlinked, if
		212	possible, except when setting atime, mtime, access mode and uid/gid, where
		213	errors are being ignored.
		214
		215	=cut
		216
		217	sub aio_move($$$) {
		218	my ($src, $dst, $cb) = @_;
		219
		220	my $grp = aio_group $cb;
		221
		222	add $grp aio_rename $src, $dst, sub {
		223	if ($_[0] && $! == EXDEV) {
		224	add $grp aio_open $src, O_RDONLY, 0, sub {
		225	if (my $src_fh = $_[0]) {
		226	my @stat = stat $src_fh;
		227
		228	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		229	if (my $dst_fh = $_[0]) {
		230	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		231	close $src_fh;
		232
		233	if ($_[0] == $stat[7]) {
		234	utime $stat[8], $stat[9], $dst;
		235	chmod $stat[2] & 07777, $dst_fh;
		236	chown $stat[4], $stat[5], $dst_fh;
		237	close $dst_fh;
		238
		239	add $grp aio_unlink $src, sub {
		240	$grp->result ($_[0]);
		241	};
		242	} else {
		243	my $errno = $!;
		244	add $grp aio_unlink $dst, sub {
		245	$! = $errno;
		246	$grp->result (-1);
		247	};
		248	}
		249	};
		250	} else {
		251	$grp->result (-1);
		252	}
		253	},
		254
		255	} else {
		256	$grp->result (-1);
		257	}
		258	};
		259	} else {
		260	$grp->result ($_[0]);
		261	}
		262	};
		263
		264	$grp
		265	}
		266
173	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	267	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
174		268
175	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	269	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
176	reading at byte offset C<$in_offset>, and starts writing at the current	270	reading at byte offset C<$in_offset>, and starts writing at the current
177	file offset of C<$out_fh>. Because of that, it is not safe to issue more	271	file offset of C<$out_fh>. Because of that, it is not safe to issue more
…		…
232	=item aio_unlink $pathname, $callback->($status)	326	=item aio_unlink $pathname, $callback->($status)
233		327
234	Asynchronously unlink (delete) a file and call the callback with the	328	Asynchronously unlink (delete) a file and call the callback with the
235	result code.	329	result code.
236		330
		331	=item aio_link $srcpath, $dstpath, $callback->($status)
		332
		333	Asynchronously create a new link to the existing object at C<$srcpath> at
		334	the path C<$dstpath> and call the callback with the result code.
		335
		336	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		337
		338	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		339	the path C<$dstpath> and call the callback with the result code.
		340
		341	=item aio_rename $srcpath, $dstpath, $callback->($status)
		342
		343	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		344	rename(2) and call the callback with the result code.
		345
237	=item aio_rmdir $pathname, $callback->($status)	346	=item aio_rmdir $pathname, $callback->($status)
238		347
239	Asynchronously rmdir (delete) a directory and call the callback with the	348	Asynchronously rmdir (delete) a directory and call the callback with the
240	result code.	349	result code.
241		350
242	=item aio_readdir $pathname $callback->($entries)	351	=item aio_readdir $pathname, $callback->($entries)
243		352
244	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	353	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
245	directory (i.e. opendir + readdir + closedir). The entries will not be	354	directory (i.e. opendir + readdir + closedir). The entries will not be
246	sorted, and will B<NOT> include the C<.> and C<..> entries.	355	sorted, and will B<NOT> include the C<.> and C<..> entries.
247		356
248	The callback a single argument which is either C<undef> or an array-ref	357	The callback a single argument which is either C<undef> or an array-ref
249	with the filenames.	358	with the filenames.
250		359
251	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	360	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
252		361
		362	[EXPERIMENTAL due to internal aio_group use]
		363
253	Scans a directory (similar to C<aio_readdir>) and tries to separate the	364	Scans a directory (similar to C<aio_readdir>) but additionally tries to
254	entries of directory C<$path> into two sets of names, ones you can recurse	365	separate the entries of directory C<$path> into two sets of names, ones
255	into (directories), and ones you cannot recurse into (everything else).	366	you can recurse into (directories or links to them), and ones you cannot
		367	recurse into (everything else).
256		368
257	C<aio_scandir> is a composite request that consists of many	369	C<aio_scandir> is a composite request that creates of many sub requests_
258	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	370	C<$maxreq> specifies the maximum number of outstanding aio requests that
259	aio requests that this function generates. If it is C<< <= 0 >>, then a	371	this function generates. If it is C<< <= 0 >>, then a suitable default
260	suitable default will be chosen (currently 8).	372	will be chosen (currently 6).
261		373
262	On error, the callback is called without arguments, otherwise it receives	374	On error, the callback is called without arguments, otherwise it receives
263	two array-refs with path-relative entry names.	375	two array-refs with path-relative entry names.
264		376
265	Example:	377	Example:
…		…
273	Implementation notes.	385	Implementation notes.
274		386
275	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	387	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
276		388
277	After reading the directory, the modification time, size etc. of the	389	After reading the directory, the modification time, size etc. of the
278	directory before and after the readdir is checked, and if they match, the	390	directory before and after the readdir is checked, and if they match (and
279	link count will be used to decide how many entries are directories (if	391	isn't the current time), the link count will be used to decide how many
280	>= 2). Otherwise, no knowledge of the number of subdirectories will be	392	entries are directories (if >= 2). Otherwise, no knowledge of the number
281	assumed.	393	of subdirectories will be assumed.
282		394
283	Then entires will be sorted into likely directories (everything without a	395	Then entries will be sorted into likely directories (everything without
284	non-initial dot) and likely non-directories (everything else). Then every	396	a non-initial dot currently) and likely non-directories (everything
285	entry + C</.> will be C<stat>'ed, likely directories first. This is often	397	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		398	likely directories first. If that succeeds, it assumes that the entry
		399	is a directory or a symlink to directory (which will be checked
		400	seperately). This is often faster than stat'ing the entry itself because
286	faster because filesystems might detect the type of the entry without	401	filesystems might detect the type of the entry without reading the inode
287	reading the inode data (e.g. ext2s filetype feature). If that succeeds,	402	data (e.g. ext2fs filetype feature).
288	it assumes that the entry is a directory or a symlink to directory (which
289	will be checked seperately).
290		403
291	If the known number of directories has been reached, the rest of the	404	If the known number of directories (link count - 2) has been reached, the
292	entries is assumed to be non-directories.	405	rest of the entries is assumed to be non-directories.
		406
		407	This only works with certainty on POSIX (= UNIX) filesystems, which
		408	fortunately are the vast majority of filesystems around.
		409
		410	It will also likely work on non-POSIX filesystems with reduced efficiency
		411	as those tend to return 0 or 1 as link counts, which disables the
		412	directory counting heuristic.
293		413
294	=cut	414	=cut
295		415
296	sub aio_scandir($$$) {	416	sub aio_scandir($$$) {
297	my ($path, $maxreq, $cb) = @_;	417	my ($path, $maxreq, $cb) = @_;
298		418
		419	my $grp = aio_group $cb;
		420
299	$maxreq = 8 if $maxreq <= 0;	421	$maxreq = 6 if $maxreq <= 0;
300		422
301	# stat once	423	# stat once
302	aio_stat $path, sub {	424	add $grp aio_stat $path, sub {
303	$cb->() if $_[0];	425	return $grp->result () if $_[0];
		426	my $now = time;
304	my $hash1 = join ":", (stat _)[0,1,3,7,9];	427	my $hash1 = join ":", (stat _)[0,1,3,7,9];
305		428
306	# read the directory entries	429	# read the directory entries
307	aio_readdir $path, sub {	430	add $grp aio_readdir $path, sub {
308	my $entries = shift	431	my $entries = shift
309	or return $cb->();	432	or return $grp->result ();
310		433
311	# stat the dir another time	434	# stat the dir another time
312	aio_stat $path, sub {	435	add $grp aio_stat $path, sub {
313	my $hash2 = join ":", (stat _)[0,1,3,7,9];	436	my $hash2 = join ":", (stat _)[0,1,3,7,9];
314		437
315	my $ndirs;	438	my $ndirs;
316		439
317	# take the slow route if anything looks fishy	440	# take the slow route if anything looks fishy
318	if ($hash1 ne $hash2) {	441	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
319	$ndirs = -1;	442	$ndirs = -1;
320	} else {	443	} else {
321	# if nlink == 2, we are finished	444	# if nlink == 2, we are finished
322	# on non-posix-fs's, we rely on nlink < 2	445	# on non-posix-fs's, we rely on nlink < 2
323	$ndirs = (stat _)[3] - 2	446	$ndirs = (stat _)[3] - 2
324	or $cb->([], $entries);	447	or return $grp->result ([], $entries);
325	}	448	}
326		449
327	# sort into likely dirs and likely nondirs	450	# sort into likely dirs and likely nondirs
328	# dirs == files without ".", short entries first	451	# dirs == files without ".", short entries first
329	$entries = [map $_->[0],	452	$entries = [map $_->[0],
…		…
334	my (@dirs, @nondirs);	457	my (@dirs, @nondirs);
335		458
336	my ($statcb, $schedcb);	459	my ($statcb, $schedcb);
337	my $nreq = 0;	460	my $nreq = 0;
338		461
		462	my $statgrp = add $grp aio_group;
		463
339	$schedcb = sub {	464	$schedcb = sub {
340	if (@$entries) {	465	if (@$entries) {
341	if ($nreq < $maxreq) {	466	if ($nreq < $maxreq) {
342	my $ent = pop @$entries;	467	my $ent = pop @$entries;
343	$nreq++;	468	$nreq++;
344	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };	469	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
345	}	470	}
346	} elsif (!$nreq) {	471	} elsif (!$nreq) {
347	# finished	472	# finished
		473	$statgrp->cancel;
348	undef $statcb;	474	undef $statcb;
349	undef $schedcb;	475	undef $schedcb;
350	$cb->(\@dirs, \@nondirs);	476	$grp->result (\@dirs, \@nondirs);
351	undef $cb;
352	}	477	}
353	};	478	};
354	$statcb = sub {	479	$statcb = sub {
355	my ($status, $entry) = @_;	480	my ($status, $entry) = @_;
356		481
…		…
358	$nreq--;	483	$nreq--;
359	push @nondirs, $entry;	484	push @nondirs, $entry;
360	&$schedcb;	485	&$schedcb;
361	} else {	486	} else {
362	# need to check for real directory	487	# need to check for real directory
363	aio_lstat "$path/$entry", sub {	488	add $grp aio_lstat "$path/$entry", sub {
364	$nreq--;	489	$nreq--;
365		490
366	if (-d _) {	491	if (-d _) {
367	push @dirs, $entry;	492	push @dirs, $entry;
368		493
…		…
381		506
382	&$schedcb while @$entries && $nreq < $maxreq;	507	&$schedcb while @$entries && $nreq < $maxreq;
383	};	508	};
384	};	509	};
385	};	510	};
		511
		512	$grp
386	}	513	}
387		514
388	=item aio_fsync $fh, $callback->($status)	515	=item aio_fsync $fh, $callback->($status)
389		516
390	Asynchronously call fsync on the given filehandle and call the callback	517	Asynchronously call fsync on the given filehandle and call the callback
…		…
395	Asynchronously call fdatasync on the given filehandle and call the	522	Asynchronously call fdatasync on the given filehandle and call the
396	callback with the fdatasync result code.	523	callback with the fdatasync result code.
397		524
398	If this call isn't available because your OS lacks it or it couldn't be	525	If this call isn't available because your OS lacks it or it couldn't be
399	detected, it will be emulated by calling C<fsync> instead.	526	detected, it will be emulated by calling C<fsync> instead.
		527
		528	=item aio_group $callback->(...)
		529
		530	[EXPERIMENTAL]
		531
		532	This is a very special aio request: Instead of doing something, it is a
		533	container for other aio requests, which is useful if you want to bundle
		534	many requests into a single, composite, request.
		535
		536	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		537	for more info.
		538
		539	Example:
		540
		541	my $grp = aio_group sub {
		542	print "all stats done\n";
		543	};
		544
		545	add $grp
		546	(aio_stat ...),
		547	(aio_stat ...),
		548	...;
		549
		550	=item aio_nop $callback->()
		551
		552	This is a special request - it does nothing in itself and is only used for
		553	side effects, such as when you want to add a dummy request to a group so
		554	that finishing the requests in the group depends on executing the given
		555	code.
		556
		557	While this request does nothing, it still goes through the execution
		558	phase and still requires a worker thread. Thus, the callback will not
		559	be executed immediately but only after other requests in the queue have
		560	entered their execution phase. This can be used to measure request
		561	latency.
		562
		563	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		564
		565	Mainly used for debugging and benchmarking, this aio request puts one of
		566	the request workers to sleep for the given time.
		567
		568	While it is theoretically handy to have simple I/O scheduling requests
		569	like sleep and file handle readable/writable, the overhead this creates
		570	is immense, so do not use this function except to put your application
		571	under artificial I/O pressure.
		572
		573	=back
		574
		575	=head2 IO::AIO::REQ CLASS
		576
		577	All non-aggregate C<aio_*> functions return an object of this class when
		578	called in non-void context.
		579
		580	A request always moves through the following five states in its lifetime,
		581	in order: B<ready> (request has been created, but has not been executed
		582	yet), B<execute> (request is currently being executed), B<pending>
		583	(request has been executed but callback has not been called yet),
		584	B<result> (results are being processed synchronously, includes calling the
		585	callback) and B<done> (request has reached the end of its lifetime and
		586	holds no resources anymore).
		587
		588	=over 4
		589
		590	=item cancel $req
		591
		592	Cancels the request, if possible. Has the effect of skipping execution
		593	when entering the B<execute> state and skipping calling the callback when
		594	entering the the B<result> state, but will leave the request otherwise
		595	untouched. That means that requests that currently execute will not be
		596	stopped and resources held by the request will not be freed prematurely.
		597
		598	=item cb $req $callback->(...)
		599
		600	Replace (or simply set) the callback registered to the request.
		601
		602	=back
		603
		604	=head2 IO::AIO::GRP CLASS
		605
		606	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		607	objects of this class, too.
		608
		609	A IO::AIO::GRP object is a special request that can contain multiple other
		610	aio requests.
		611
		612	You create one by calling the C<aio_group> constructing function with a
		613	callback that will be called when all contained requests have entered the
		614	C<done> state:
		615
		616	my $grp = aio_group sub {
		617	print "all requests are done\n";
		618	};
		619
		620	You add requests by calling the C<add> method with one or more
		621	C<IO::AIO::REQ> objects:
		622
		623	$grp->add (aio_unlink "...");
		624
		625	add $grp aio_stat "...", sub {
		626	$_[0] or return $grp->result ("error");
		627
		628	# add another request dynamically, if first succeeded
		629	add $grp aio_open "...", sub {
		630	$grp->result ("ok");
		631	};
		632	};
		633
		634	This makes it very easy to create composite requests (see the source of
		635	C<aio_move> for an application) that work and feel like simple requests.
		636
		637	=over 4
		638
		639	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		640	C<IO::AIO::poll_cb>, just like any other request.
		641
		642	=item * They can be canceled like any other request. Canceling will cancel not
		643	only the request itself, but also all requests it contains.
		644
		645	=item * They can also can also be added to other IO::AIO::GRP objects.
		646
		647	=item * You must not add requests to a group from within the group callback (or
		648	any later time).
		649
		650	=item * This does not harmonise well with C<max_outstanding>, so best do
		651	not combine C<aio_group> with it. Groups and feeders are recommended for
		652	this kind of concurrency-limiting.
		653
		654	=back
		655
		656	Their lifetime, simplified, looks like this: when they are empty, they
		657	will finish very quickly. If they contain only requests that are in the
		658	C<done> state, they will also finish. Otherwise they will continue to
		659	exist.
		660
		661	That means after creating a group you have some time to add requests. And
		662	in the callbacks of those requests, you can add further requests to the
		663	group. And only when all those requests have finished will the the group
		664	itself finish.
		665
		666	=over 4
		667
		668	=item add $grp ...
		669
		670	=item $grp->add (...)
		671
		672	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		673	be added, including other groups, as long as you do not create circular
		674	dependencies.
		675
		676	Returns all its arguments.
		677
		678	=item $grp->result (...)
		679
		680	Set the result value(s) that will be passed to the group callback when all
		681	subrequests have finished. By default, no argument will be passed.
		682
		683	=item feed $grp $callback->($grp)
		684
		685	[VERY EXPERIMENTAL]
		686
		687	Sets a feeder/generator on this group: every group can have an attached
		688	generator that generates requests if idle. The idea behind this is that,
		689	although you could just queue as many requests as you want in a group,
		690	this might starve other requests for a potentially long time. For
		691	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		692	requests, delaying any later requests for a long time.
		693
		694	To avoid this, and allow incremental generation of requests, you can
		695	instead a group and set a feeder on it that generates those requests. The
		696	feed callback will be called whenever there are few enough (see C<limit>,
		697	below) requests active in the group itself and is expected to queue more
		698	requests.
		699
		700	The feed callback can queue as many requests as it likes (i.e. C<add> does
		701	not impose any limits).
		702
		703	If the feed does not queue more requests when called, it will be
		704	automatically removed from the group.
		705
		706	If the feed limit is C<0>, it will be set to C<2> automatically.
		707
		708	Example:
		709
		710	# stat all files in @files, but only ever use four aio requests concurrently:
		711
		712	my $grp = aio_group sub { print "finished\n" };
		713	limit $grp 4;
		714	feed $grp sub {
		715	my $file = pop @files
		716	or return;
		717
		718	add $grp aio_stat $file, sub { ... };
		719	};
		720
		721	=item limit $grp $num
		722
		723	Sets the feeder limit for the group: The feeder will be called whenever
		724	the group contains less than this many requests.
		725
		726	Setting the limit to C<0> will pause the feeding process.
400		727
401	=back	728	=back
402		729
403	=head2 SUPPORT FUNCTIONS	730	=head2 SUPPORT FUNCTIONS
404		731
…		…
462	IO::AIO::poll_wait, IO::AIO::poll_cb	789	IO::AIO::poll_wait, IO::AIO::poll_cb
463	if IO::AIO::nreqs;	790	if IO::AIO::nreqs;
464		791
465	=item IO::AIO::min_parallel $nthreads	792	=item IO::AIO::min_parallel $nthreads
466		793
467	Set the minimum number of AIO threads to C<$nthreads>. The current default	794	Set the minimum number of AIO threads to C<$nthreads>. The current
468	is C<4>, which means four asynchronous operations can be done at one time	795	default is C<8>, which means eight asynchronous operations can execute
469	(the number of outstanding operations, however, is unlimited).	796	concurrently at any one time (the number of outstanding requests,
		797	however, is unlimited).
470		798
471	IO::AIO starts threads only on demand, when an AIO request is queued and	799	IO::AIO starts threads only on demand, when an AIO request is queued and
472	no free thread exists.	800	no free thread exists.
473		801
474	It is recommended to keep the number of threads low, as some Linux	802	It is recommended to keep the number of threads relatively low, as some
475	kernel versions will scale negatively with the number of threads (higher	803	Linux kernel versions will scale negatively with the number of threads
476	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	804	(higher parallelity => MUCH higher latency). With current Linux 2.6
477	threads should be fine.	805	versions, 4-32 threads should be fine.
478		806
479	Under most circumstances you don't need to call this function, as the	807	Under most circumstances you don't need to call this function, as the
480	module selects a default that is suitable for low to moderate load.	808	module selects a default that is suitable for low to moderate load.
481		809
482	=item IO::AIO::max_parallel $nthreads	810	=item IO::AIO::max_parallel $nthreads
…		…
493		821
494	Under normal circumstances you don't need to call this function.	822	Under normal circumstances you don't need to call this function.
495		823
496	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	824	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
497		825
		826	[DEPRECATED]
		827
498	Sets the maximum number of outstanding requests to C<$nreqs>. If you	828	Sets the maximum number of outstanding requests to C<$nreqs>. If you
499	try to queue up more than this number of requests, the caller will block until	829	try to queue up more than this number of requests, the caller will block until
500	some requests have been handled.	830	some requests have been handled.
501		831
502	The default is very large, so normally there is no practical limit. If you	832	The default is very large, so normally there is no practical limit. If you
503	queue up many requests in a loop it often improves speed if you set	833	queue up many requests in a loop it often improves speed if you set
504	this to a relatively low number, such as C<100>.	834	this to a relatively low number, such as C<100>.
		835
		836	This function does not work well together with C<aio_group>'s, and their
		837	feeder interface is better suited to limiting concurrency, so do not use
		838	this function.
505		839
506	Under normal circumstances you don't need to call this function.	840	Under normal circumstances you don't need to call this function.
507		841
508	=back	842	=back
509		843
…		…
523	or return undef;	857	or return undef;
524		858
525	*$sym	859	*$sym
526	}	860	}
527		861
528	min_parallel 4;	862	min_parallel 8;
529		863
530	END {	864	END {
531	max_parallel 0;	865	max_parallel 0;
532	}	866	}
533		867
534	1;	868	1;
535		869
536	=head2 FORK BEHAVIOUR	870	=head2 FORK BEHAVIOUR
		871
		872	This module should do "the right thing" when the process using it forks:
537		873
538	Before the fork, IO::AIO enters a quiescent state where no requests	874	Before the fork, IO::AIO enters a quiescent state where no requests
539	can be added in other threads and no results will be processed. After	875	can be added in other threads and no results will be processed. After
540	the fork the parent simply leaves the quiescent state and continues	876	the fork the parent simply leaves the quiescent state and continues
541	request/result processing, while the child clears the request/result	877	request/result processing, while the child clears the request/result
542	queue (so the requests started before the fork will only be handled in	878	queue (so the requests started before the fork will only be handled in
543	the parent). Threats will be started on demand until the limit ste in the	879	the parent). Threads will be started on demand until the limit ste in the
544	parent process has been reached again.	880	parent process has been reached again.
545		881
		882	In short: the parent will, after a short pause, continue as if fork had
		883	not been called, while the child will act as if IO::AIO has not been used
		884	yet.
		885
		886	=head2 MEMORY USAGE
		887
		888	Each aio request uses - depending on your architecture - around 128 bytes
		889	of memory. In addition, stat requests need a stat buffer (possibly a few
		890	hundred bytes). Perl scalars and other data passed into aio requests will
		891	also be locked.
		892
		893	This is now awfully much, so queuing lots of requests is not usually a
		894	problem.
		895
		896	Each thread needs a stack area which is usually around 16k, sometimes much
		897	larger, depending on the OS.
		898
546	=head1 SEE ALSO	899	=head1 SEE ALSO
547		900
548	L<Coro>, L<Linux::AIO>.	901	L<Coro::AIO>.
549		902
550	=head1 AUTHOR	903	=head1 AUTHOR
551		904
552	Marc Lehmann <schmorp@schmorp.de>	905	Marc Lehmann <schmorp@schmorp.de>
553	http://home.schmorp.de/	906	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.42 by root, Mon Dec 26 18:15:23 2005 UTC vs.
Revision 1.68 by root, Tue Oct 24 03:17:39 2006 UTC