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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.39 by root, Sun Aug 28 11:05:50 2005 UTC vs.
Revision 1.66 by root, Mon Oct 23 22:54:27 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	# Event	20	# version 2+ has request and group objects
		21	use IO::AIO 2;
		22
		23	my $req = aio_unlink "/tmp/file", sub { };
		24	$req->cancel; # cancel request if still in queue
		25
		26	my $grp = aio_group sub { print "all stats done\n" };
		27	add $grp aio_stat "..." for ...;
		28
		29	# AnyEvent integration
		30	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		31	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		32
		33	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	34	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	35	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	36	cb => \&IO::AIO::poll_cb);
24		37
25	# Glib/Gtk2	38	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	39	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb; 1 };	40	in => sub { IO::AIO::poll_cb; 1 };
28		41
29	# Tk	42	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	43	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	44	readable => \&IO::AIO::poll_cb);
32		45
33	# Danga::Socket	46	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	47	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	48	\&IO::AIO::poll_cb);
36		49
37
38	=head1 DESCRIPTION	50	=head1 DESCRIPTION
39		51
40	This module implements asynchronous I/O using whatever means your	52	This module implements asynchronous I/O using whatever means your
41	operating system supports.	53	operating system supports.
42		54
43	Currently, a number of threads are started that execute your read/writes	55	Currently, a number of threads are started that execute your read/writes
44	and signal their completion. You don't need thread support in your libc or	56	and signal their completion. You don't need thread support in perl, and
45	perl, and the threads created by this module will not be visible to the	57	the threads created by this module will not be visible to perl. In the
46	pthreads library. In the future, this module might make use of the native	58	future, this module might make use of the native aio functions available
47	aio functions available on many operating systems. However, they are often	59	on many operating systems. However, they are often not well-supported
48	not well-supported (Linux doesn't allow them on normal files currently,	60	(Linux doesn't allow them on normal files currently, for example),
49	for example), and they would only support aio_read and aio_write, so the	61	and they would only support aio_read and aio_write, so the remaining
50	remaining functionality would have to be implemented using threads anyway.	62	functionality would have to be implemented using threads anyway.
51		63
52	Although the module will work with in the presence of other threads, it is	64	Although the module will work with in the presence of other threads, it is
53	currently not reentrant, so use appropriate locking yourself, always call	65	currently not reentrant, so use appropriate locking yourself, always call
54	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	66	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other
55	C<aio_> functions) recursively.	67	C<aio_> functions) recursively.
…		…
57	=cut	69	=cut
58		70
59	package IO::AIO;	71	package IO::AIO;
60		72
61	no warnings;	73	no warnings;
		74	use strict 'vars';
62		75
63	use base 'Exporter';	76	use base 'Exporter';
64		77
65	use Fcntl ();
66
67	BEGIN {	78	BEGIN {
68	$VERSION = 1.6;	79	our $VERSION = '2.0';
69		80
70	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	81	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71	aio_lstat aio_unlink aio_rmdir aio_readdir aio_symlink	82	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72	aio_fsync aio_fdatasync aio_readahead);	83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		84	aio_group aio_nop);
73	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
74	max_outstanding nreqs);	86
		87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
75		88
76	require XSLoader;	89	require XSLoader;
77	XSLoader::load IO::AIO, $VERSION;	90	XSLoader::load ("IO::AIO", $VERSION);
78	}	91	}
79		92
80	=head1 FUNCTIONS	93	=head1 FUNCTIONS
81		94
82	=head2 AIO FUNCTIONS	95	=head2 AIO FUNCTIONS
…		…
90	syscall has been executed asynchronously.	103	syscall has been executed asynchronously.
91		104
92	All functions expecting a filehandle keep a copy of the filehandle	105	All functions expecting a filehandle keep a copy of the filehandle
93	internally until the request has finished.	106	internally until the request has finished.
94		107
		108	All requests return objects of type L<IO::AIO::REQ> that allow further
		109	manipulation of those requests while they are in-flight.
		110
95	The pathnames you pass to these routines I<must> be absolute and	111	The pathnames you pass to these routines I<must> be absolute and
96	encoded in byte form. The reason for the former is that at the time the	112	encoded in byte form. The reason for the former is that at the time the
97	request is being executed, the current working directory could have	113	request is being executed, the current working directory could have
98	changed. Alternatively, you can make sure that you never change the	114	changed. Alternatively, you can make sure that you never change the
99	current working directory.	115	current working directory.
…		…
105	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	121	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
106	use something else.	122	use something else.
107		123
108	=over 4	124	=over 4
109		125
110	=item aio_open $pathname, $flags, $mode, $callback	126	=item aio_open $pathname, $flags, $mode, $callback->($fh)
111		127
112	Asynchronously open or create a file and call the callback with a newly	128	Asynchronously open or create a file and call the callback with a newly
113	created filehandle for the file.	129	created filehandle for the file.
114		130
115	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	131	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
132	} else {	148	} else {
133	die "open failed: $!\n";	149	die "open failed: $!\n";
134	}	150	}
135	};	151	};
136		152
137	=item aio_close $fh, $callback	153	=item aio_close $fh, $callback->($status)
138		154
139	Asynchronously close a file and call the callback with the result	155	Asynchronously close a file and call the callback with the result
140	code. I<WARNING:> although accepted, you should not pass in a perl	156	code. I<WARNING:> although accepted, you should not pass in a perl
141	filehandle here, as perl will likely close the file descriptor another	157	filehandle here, as perl will likely close the file descriptor another
142	time when the filehandle is destroyed. Normally, you can safely call perls	158	time when the filehandle is destroyed. Normally, you can safely call perls
143	C<close> or just let filehandles go out of scope.	159	C<close> or just let filehandles go out of scope.
144		160
145	This is supposed to be a bug in the API, so that might change. It's	161	This is supposed to be a bug in the API, so that might change. It's
146	therefore best to avoid this function.	162	therefore best to avoid this function.
147		163
148	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149		165
150	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
151		167
152	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	168	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
153	into the scalar given by C<data> and offset C<dataoffset> and calls the	169	into the scalar given by C<data> and offset C<dataoffset> and calls the
154	callback without the actual number of bytes read (or -1 on error, just	170	callback without the actual number of bytes read (or -1 on error, just
155	like the syscall).	171	like the syscall).
…		…
164	aio_read $fh, 7, 15, $buffer, 0, sub {	180	aio_read $fh, 7, 15, $buffer, 0, sub {
165	$_[0] > 0 or die "read error: $!";	181	$_[0] > 0 or die "read error: $!";
166	print "read $_[0] bytes: <$buffer>\n";	182	print "read $_[0] bytes: <$buffer>\n";
167	};	183	};
168		184
		185	=item aio_move $srcpath, $dstpath, $callback->($status)
		186
		187	[EXPERIMENTAL due to internal aio_group use]
		188
		189	Try to move the I<file> (directories not supported as either source or
		190	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		191	the C<0> (error) or C<-1> ok.
		192
		193	This is a composite request that tries to rename(2) the file first. If
		194	rename files with C<EXDEV>, it creates the destination file with mode 0200
		195	and copies the contents of the source file into it using C<aio_sendfile>,
		196	followed by restoring atime, mtime, access mode and uid/gid, in that
		197	order, and unlinking the C<$srcpath>.
		198
		199	If an error occurs, the partial destination file will be unlinked, if
		200	possible, except when setting atime, mtime, access mode and uid/gid, where
		201	errors are being ignored.
		202
		203	=cut
		204
		205	sub aio_move($$$) {
		206	my ($src, $dst, $cb) = @_;
		207
		208	my $grp = aio_group $cb;
		209
		210	add $grp aio_rename $src, $dst, sub {
		211	if ($_[0] && $! == EXDEV) {
		212	add $grp aio_open $src, O_RDONLY, 0, sub {
		213	if (my $src_fh = $_[0]) {
		214	my @stat = stat $src_fh;
		215
		216	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		217	if (my $dst_fh = $_[0]) {
		218	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		219	close $src_fh;
		220
		221	if ($_[0] == $stat[7]) {
		222	utime $stat[8], $stat[9], $dst;
		223	chmod $stat[2] & 07777, $dst_fh;
		224	chown $stat[4], $stat[5], $dst_fh;
		225	close $dst_fh;
		226
		227	add $grp aio_unlink $src, sub {
		228	$grp->result ($_[0]);
		229	};
		230	} else {
		231	my $errno = $!;
		232	add $grp aio_unlink $dst, sub {
		233	$! = $errno;
		234	$grp->result (-1);
		235	};
		236	}
		237	};
		238	} else {
		239	$grp->result (-1);
		240	}
		241	},
		242
		243	} else {
		244	$grp->result (-1);
		245	}
		246	};
		247	} else {
		248	$grp->result ($_[0]);
		249	}
		250	};
		251
		252	$grp
		253	}
		254
169	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback	255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
170		256
171	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	257	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
172	reading at byte offset C<$in_offset>, and starts writing at the current	258	reading at byte offset C<$in_offset>, and starts writing at the current
173	file offset of C<$out_fh>. Because of that, it is not safe to issue more	259	file offset of C<$out_fh>. Because of that, it is not safe to issue more
174	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	260	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
…		…
187	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	273	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
188	provides the number of bytes written to C<$out_fh>. Only if the result	274	provides the number of bytes written to C<$out_fh>. Only if the result
189	value equals C<$length> one can assume that C<$length> bytes have been	275	value equals C<$length> one can assume that C<$length> bytes have been
190	read.	276	read.
191		277
192	=item aio_readahead $fh,$offset,$length, $callback	278	=item aio_readahead $fh,$offset,$length, $callback->($retval)
193		279
194	C<aio_readahead> populates the page cache with data from a file so that	280	C<aio_readahead> populates the page cache with data from a file so that
195	subsequent reads from that file will not block on disk I/O. The C<$offset>	281	subsequent reads from that file will not block on disk I/O. The C<$offset>
196	argument specifies the starting point from which data is to be read and	282	argument specifies the starting point from which data is to be read and
197	C<$length> specifies the number of bytes to be read. I/O is performed in	283	C<$length> specifies the number of bytes to be read. I/O is performed in
…		…
201	file. The current file offset of the file is left unchanged.	287	file. The current file offset of the file is left unchanged.
202		288
203	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	289	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
204	emulated by simply reading the data, which would have a similar effect.	290	emulated by simply reading the data, which would have a similar effect.
205		291
206	=item aio_stat $fh_or_path, $callback	292	=item aio_stat $fh_or_path, $callback->($status)
207		293
208	=item aio_lstat $fh, $callback	294	=item aio_lstat $fh, $callback->($status)
209		295
210	Works like perl's C<stat> or C<lstat> in void context. The callback will	296	Works like perl's C<stat> or C<lstat> in void context. The callback will
211	be called after the stat and the results will be available using C<stat _>	297	be called after the stat and the results will be available using C<stat _>
212	or C<-s _> etc...	298	or C<-s _> etc...
213		299
…		…
223	aio_stat "/etc/passwd", sub {	309	aio_stat "/etc/passwd", sub {
224	$_[0] and die "stat failed: $!";	310	$_[0] and die "stat failed: $!";
225	print "size is ", -s _, "\n";	311	print "size is ", -s _, "\n";
226	};	312	};
227		313
228	=item aio_unlink $pathname, $callback	314	=item aio_unlink $pathname, $callback->($status)
229		315
230	Asynchronously unlink (delete) a file and call the callback with the	316	Asynchronously unlink (delete) a file and call the callback with the
231	result code.	317	result code.
232		318
		319	=item aio_link $srcpath, $dstpath, $callback->($status)
		320
		321	Asynchronously create a new link to the existing object at C<$srcpath> at
		322	the path C<$dstpath> and call the callback with the result code.
		323
		324	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		325
		326	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		327	the path C<$dstpath> and call the callback with the result code.
		328
		329	=item aio_rename $srcpath, $dstpath, $callback->($status)
		330
		331	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		332	rename(2) and call the callback with the result code.
		333
233	=item aio_rmdir $pathname, $callback	334	=item aio_rmdir $pathname, $callback->($status)
234		335
235	Asynchronously rmdir (delete) a directory and call the callback with the	336	Asynchronously rmdir (delete) a directory and call the callback with the
236	result code.	337	result code.
237		338
238	=item aio_readdir $pathname $callback	339	=item aio_readdir $pathname, $callback->($entries)
239		340
240	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	341	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
241	directory (i.e. opendir + readdir + closedir). The entries will not be	342	directory (i.e. opendir + readdir + closedir). The entries will not be
242	sorted, and will B<NOT> include the C<.> and C<..> entries.	343	sorted, and will B<NOT> include the C<.> and C<..> entries.
243		344
244	The callback a single argument which is either C<undef> or an array-ref	345	The callback a single argument which is either C<undef> or an array-ref
245	with the filenames.	346	with the filenames.
246		347
		348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		349
		350	[EXPERIMENTAL due to internal aio_group use]
		351
		352	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		353	separate the entries of directory C<$path> into two sets of names, ones
		354	you can recurse into (directories or links to them), and ones you cannot
		355	recurse into (everything else).
		356
		357	C<aio_scandir> is a composite request that creates of many sub requests_
		358	C<$maxreq> specifies the maximum number of outstanding aio requests that
		359	this function generates. If it is C<< <= 0 >>, then a suitable default
		360	will be chosen (currently 6).
		361
		362	On error, the callback is called without arguments, otherwise it receives
		363	two array-refs with path-relative entry names.
		364
		365	Example:
		366
		367	aio_scandir $dir, 0, sub {
		368	my ($dirs, $nondirs) = @_;
		369	print "real directories: @$dirs\n";
		370	print "everything else: @$nondirs\n";
		371	};
		372
		373	Implementation notes.
		374
		375	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		376
		377	After reading the directory, the modification time, size etc. of the
		378	directory before and after the readdir is checked, and if they match (and
		379	isn't the current time), the link count will be used to decide how many
		380	entries are directories (if >= 2). Otherwise, no knowledge of the number
		381	of subdirectories will be assumed.
		382
		383	Then entries will be sorted into likely directories (everything without
		384	a non-initial dot currently) and likely non-directories (everything
		385	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		386	likely directories first. If that succeeds, it assumes that the entry
		387	is a directory or a symlink to directory (which will be checked
		388	seperately). This is often faster than stat'ing the entry itself because
		389	filesystems might detect the type of the entry without reading the inode
		390	data (e.g. ext2fs filetype feature).
		391
		392	If the known number of directories (link count - 2) has been reached, the
		393	rest of the entries is assumed to be non-directories.
		394
		395	This only works with certainty on POSIX (= UNIX) filesystems, which
		396	fortunately are the vast majority of filesystems around.
		397
		398	It will also likely work on non-POSIX filesystems with reduced efficiency
		399	as those tend to return 0 or 1 as link counts, which disables the
		400	directory counting heuristic.
		401
		402	=cut
		403
		404	sub aio_scandir($$$) {
		405	my ($path, $maxreq, $cb) = @_;
		406
		407	my $grp = aio_group $cb;
		408
		409	$maxreq = 6 if $maxreq <= 0;
		410
		411	# stat once
		412	add $grp aio_stat $path, sub {
		413	return $grp->result () if $_[0];
		414	my $now = time;
		415	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		416
		417	# read the directory entries
		418	add $grp aio_readdir $path, sub {
		419	my $entries = shift
		420	or return $grp->result ();
		421
		422	# stat the dir another time
		423	add $grp aio_stat $path, sub {
		424	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		425
		426	my $ndirs;
		427
		428	# take the slow route if anything looks fishy
		429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		430	$ndirs = -1;
		431	} else {
		432	# if nlink == 2, we are finished
		433	# on non-posix-fs's, we rely on nlink < 2
		434	$ndirs = (stat _)[3] - 2
		435	or return $grp->result ([], $entries);
		436	}
		437
		438	# sort into likely dirs and likely nondirs
		439	# dirs == files without ".", short entries first
		440	$entries = [map $_->[0],
		441	sort { $b->[1] cmp $a->[1] }
		442	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		443	@$entries];
		444
		445	my (@dirs, @nondirs);
		446
		447	my ($statcb, $schedcb);
		448	my $nreq = 0;
		449
		450	my $statgrp = add $grp aio_group;
		451
		452	$schedcb = sub {
		453	if (@$entries) {
		454	if ($nreq < $maxreq) {
		455	my $ent = pop @$entries;
		456	$nreq++;
		457	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		458	}
		459	} elsif (!$nreq) {
		460	# finished
		461	$statgrp->cancel;
		462	undef $statcb;
		463	undef $schedcb;
		464	$grp->result (\@dirs, \@nondirs);
		465	}
		466	};
		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	};
		497	};
		498	};
		499
		500	$grp
		501	}
		502
247	=item aio_fsync $fh, $callback	503	=item aio_fsync $fh, $callback->($status)
248		504
249	Asynchronously call fsync on the given filehandle and call the callback	505	Asynchronously call fsync on the given filehandle and call the callback
250	with the fsync result code.	506	with the fsync result code.
251		507
252	=item aio_fdatasync $fh, $callback	508	=item aio_fdatasync $fh, $callback->($status)
253		509
254	Asynchronously call fdatasync on the given filehandle and call the	510	Asynchronously call fdatasync on the given filehandle and call the
255	callback with the fdatasync result code.	511	callback with the fdatasync result code.
256		512
257	If this call isn't available because your OS lacks it or it couldn't be	513	If this call isn't available because your OS lacks it or it couldn't be
258	detected, it will be emulated by calling C<fsync> instead.	514	detected, it will be emulated by calling C<fsync> instead.
		515
		516	=item aio_group $callback->(...)
		517
		518	[EXPERIMENTAL]
		519
		520	This is a very special aio request: Instead of doing something, it is a
		521	container for other aio requests, which is useful if you want to bundle
		522	many requests into a single, composite, request.
		523
		524	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		525	for more info.
		526
		527	Example:
		528
		529	my $grp = aio_group sub {
		530	print "all stats done\n";
		531	};
		532
		533	add $grp
		534	(aio_stat ...),
		535	(aio_stat ...),
		536	...;
		537
		538	=item aio_nop $callback->()
		539
		540	This is a special request - it does nothing in itself and is only used for
		541	side effects, such as when you want to add a dummy request to a group so
		542	that finishing the requests in the group depends on executing the given
		543	code.
		544
		545	While this request does nothing, it still goes through the execution
		546	phase and still requires a worker thread. Thus, the callback will not
		547	be executed immediately but only after other requests in the queue have
		548	entered their execution phase. This can be used to measure request
		549	latency.
		550
		551	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		552
		553	Mainly used for debugging and benchmarking, this aio request puts one of
		554	the request workers to sleep for the given time.
		555
		556	While it is theoretically handy to have simple I/O scheduling requests
		557	like sleep and file handle readable/writable, the overhead this creates
		558	is immense, so do not use this function except to put your application
		559	under artificial I/O pressure.
		560
		561	=back
		562
		563	=head2 IO::AIO::REQ CLASS
		564
		565	All non-aggregate C<aio_*> functions return an object of this class when
		566	called in non-void context.
		567
		568	A request always moves through the following five states in its lifetime,
		569	in order: B<ready> (request has been created, but has not been executed
		570	yet), B<execute> (request is currently being executed), B<pending>
		571	(request has been executed but callback has not been called yet),
		572	B<result> (results are being processed synchronously, includes calling the
		573	callback) and B<done> (request has reached the end of its lifetime and
		574	holds no resources anymore).
		575
		576	=over 4
		577
		578	=item cancel $req
		579
		580	Cancels the request, if possible. Has the effect of skipping execution
		581	when entering the B<execute> state and skipping calling the callback when
		582	entering the the B<result> state, but will leave the request otherwise
		583	untouched. That means that requests that currently execute will not be
		584	stopped and resources held by the request will not be freed prematurely.
		585
		586	=item cb $req $callback->(...)
		587
		588	Replace (or simply set) the callback registered to the request.
		589
		590	=back
		591
		592	=head2 IO::AIO::GRP CLASS
		593
		594	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		595	objects of this class, too.
		596
		597	A IO::AIO::GRP object is a special request that can contain multiple other
		598	aio requests.
		599
		600	You create one by calling the C<aio_group> constructing function with a
		601	callback that will be called when all contained requests have entered the
		602	C<done> state:
		603
		604	my $grp = aio_group sub {
		605	print "all requests are done\n";
		606	};
		607
		608	You add requests by calling the C<add> method with one or more
		609	C<IO::AIO::REQ> objects:
		610
		611	$grp->add (aio_unlink "...");
		612
		613	add $grp aio_stat "...", sub {
		614	$_[0] or return $grp->result ("error");
		615
		616	# add another request dynamically, if first succeeded
		617	add $grp aio_open "...", sub {
		618	$grp->result ("ok");
		619	};
		620	};
		621
		622	This makes it very easy to create composite requests (see the source of
		623	C<aio_move> for an application) that work and feel like simple requests.
		624
		625	=over 4
		626
		627	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		628	C<IO::AIO::poll_cb>, just like any other request.
		629
		630	=item * They can be canceled like any other request. Canceling will cancel not
		631	only the request itself, but also all requests it contains.
		632
		633	=item * They can also can also be added to other IO::AIO::GRP objects.
		634
		635	=item * You must not add requests to a group from within the group callback (or
		636	any later time).
		637
		638	=item * This does not harmonise well with C<max_outstanding>, so best do
		639	not combine C<aio_group> with it. Groups and feeders are recommended for
		640	this kind of concurrency-limiting.
		641
		642	=back
		643
		644	Their lifetime, simplified, looks like this: when they are empty, they
		645	will finish very quickly. If they contain only requests that are in the
		646	C<done> state, they will also finish. Otherwise they will continue to
		647	exist.
		648
		649	That means after creating a group you have some time to add requests. And
		650	in the callbacks of those requests, you can add further requests to the
		651	group. And only when all those requests have finished will the the group
		652	itself finish.
		653
		654	=over 4
		655
		656	=item add $grp ...
		657
		658	=item $grp->add (...)
		659
		660	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		661	be added, including other groups, as long as you do not create circular
		662	dependencies.
		663
		664	Returns all its arguments.
		665
		666	=item $grp->result (...)
		667
		668	Set the result value(s) that will be passed to the group callback when all
		669	subrequests have finished. By default, no argument will be passed.
		670
		671	=item feed $grp $callback->($grp)
		672
		673	[VERY EXPERIMENTAL]
		674
		675	Sets a feeder/generator on this group: every group can have an attached
		676	generator that generates requests if idle. The idea behind this is that,
		677	although you could just queue as many requests as you want in a group,
		678	this might starve other requests for a potentially long time. For
		679	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		680	requests, delaying any later requests for a long time.
		681
		682	To avoid this, and allow incremental generation of requests, you can
		683	instead a group and set a feeder on it that generates those requests. The
		684	feed callback will be called whenever there are few enough (see C<feed_limit>,
		685	below) requests active in the group itself and is expected to queue more
		686	requests.
		687
		688	The feed can queue as many requests as it likes (i.e. C<add> does not
		689	impose any limits).
		690
		691	If the feed does not queue more requests when called, it will be
		692	automatically removed from the group.
		693
		694	If the feed limit is C<0>, it will be set to C<2> automatically.
		695
		696	Example:
		697
		698	# stat all files in @files, but only ever use four aio requests concurrently:
		699
		700	my $grp = aio_group sub { print "finished\n" };
		701	feed_limit $grp 4;
		702	feed $grp sub {
		703	my $file = pop @files
		704	or return;
		705
		706	add $grp aio_stat $file, sub { ... };
		707	};
		708
		709	=item feed_limit $grp $num
		710
		711	Sets the feeder limit for the group: The feeder will be called whenever
		712	the group contains less than this many requests.
		713
		714	Setting the limit to C<0> will pause the feeding process.
259		715
260	=back	716	=back
261		717
262	=head2 SUPPORT FUNCTIONS	718	=head2 SUPPORT FUNCTIONS
263		719
…		…
321	IO::AIO::poll_wait, IO::AIO::poll_cb	777	IO::AIO::poll_wait, IO::AIO::poll_cb
322	if IO::AIO::nreqs;	778	if IO::AIO::nreqs;
323		779
324	=item IO::AIO::min_parallel $nthreads	780	=item IO::AIO::min_parallel $nthreads
325		781
326	Set the minimum number of AIO threads to C<$nthreads>. The current default	782	Set the minimum number of AIO threads to C<$nthreads>. The current
327	is C<4>, which means four asynchronous operations can be done at one time	783	default is C<8>, which means eight asynchronous operations can execute
328	(the number of outstanding operations, however, is unlimited).	784	concurrently at any one time (the number of outstanding requests,
		785	however, is unlimited).
329		786
330	IO::AIO starts threads only on demand, when an AIO request is queued and	787	IO::AIO starts threads only on demand, when an AIO request is queued and
331	no free thread exists.	788	no free thread exists.
332		789
333	It is recommended to keep the number of threads low, as some Linux	790	It is recommended to keep the number of threads relatively low, as some
334	kernel versions will scale negatively with the number of threads (higher	791	Linux kernel versions will scale negatively with the number of threads
335	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	792	(higher parallelity => MUCH higher latency). With current Linux 2.6
336	threads should be fine.	793	versions, 4-32 threads should be fine.
337		794
338	Under most circumstances you don't need to call this function, as the	795	Under most circumstances you don't need to call this function, as the
339	module selects a default that is suitable for low to moderate load.	796	module selects a default that is suitable for low to moderate load.
340		797
341	=item IO::AIO::max_parallel $nthreads	798	=item IO::AIO::max_parallel $nthreads
…		…
352		809
353	Under normal circumstances you don't need to call this function.	810	Under normal circumstances you don't need to call this function.
354		811
355	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	812	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
356		813
		814	[DEPRECATED]
		815
357	Sets the maximum number of outstanding requests to C<$nreqs>. If you	816	Sets the maximum number of outstanding requests to C<$nreqs>. If you
358	try to queue up more than this number of requests, the caller will block until	817	try to queue up more than this number of requests, the caller will block until
359	some requests have been handled.	818	some requests have been handled.
360		819
361	The default is very large, so normally there is no practical limit. If you	820	The default is very large, so normally there is no practical limit. If you
362	queue up many requests in a loop it often improves speed if you set	821	queue up many requests in a loop it often improves speed if you set
363	this to a relatively low number, such as C<100>.	822	this to a relatively low number, such as C<100>.
		823
		824	This function does not work well together with C<aio_group>'s, and their
		825	feeder interface is better suited to limiting concurrency, so do not use
		826	this function.
364		827
365	Under normal circumstances you don't need to call this function.	828	Under normal circumstances you don't need to call this function.
366		829
367	=back	830	=back
368		831
…		…
382	or return undef;	845	or return undef;
383		846
384	*$sym	847	*$sym
385	}	848	}
386		849
387	min_parallel 4;	850	min_parallel 8;
388		851
389	END {	852	END {
390	max_parallel 0;	853	max_parallel 0;
391	}	854	}
392		855
393	1;	856	1;
394		857
395	=head2 FORK BEHAVIOUR	858	=head2 FORK BEHAVIOUR
		859
		860	This module should do "the right thing" when the process using it forks:
396		861
397	Before the fork, IO::AIO enters a quiescent state where no requests	862	Before the fork, IO::AIO enters a quiescent state where no requests
398	can be added in other threads and no results will be processed. After	863	can be added in other threads and no results will be processed. After
399	the fork the parent simply leaves the quiescent state and continues	864	the fork the parent simply leaves the quiescent state and continues
400	request/result processing, while the child clears the request/result	865	request/result processing, while the child clears the request/result
401	queue (so the requests started before the fork will only be handled in	866	queue (so the requests started before the fork will only be handled in
402	the parent). Threats will be started on demand until the limit ste in the	867	the parent). Threads will be started on demand until the limit ste in the
403	parent process has been reached again.	868	parent process has been reached again.
404		869
		870	In short: the parent will, after a short pause, continue as if fork had
		871	not been called, while the child will act as if IO::AIO has not been used
		872	yet.
		873
		874	=head2 MEMORY USAGE
		875
		876	Each aio request uses - depending on your architecture - around 128 bytes
		877	of memory. In addition, stat requests need a stat buffer (possibly a few
		878	hundred bytes). Perl scalars and other data passed into aio requests will
		879	also be locked.
		880
		881	This is now awfully much, so queuing lots of requests is not usually a
		882	problem.
		883
		884	Each thread needs a stack area which is usually around 16k, sometimes much
		885	larger, depending on the OS.
		886
405	=head1 SEE ALSO	887	=head1 SEE ALSO
406		888
407	L<Coro>, L<Linux::AIO>.	889	L<Coro>, L<Linux::AIO> (obsolete).
408		890
409	=head1 AUTHOR	891	=head1 AUTHOR
410		892
411	Marc Lehmann <schmorp@schmorp.de>	893	Marc Lehmann <schmorp@schmorp.de>
412	http://home.schmorp.de/	894	http://home.schmorp.de/

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Revision 1.39 by root, Sun Aug 28 11:05:50 2005 UTC vs.
Revision 1.66 by root, Mon Oct 23 22:54:27 2006 UTC