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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.30 by root, Wed Aug 17 04:47:38 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	# Event	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
		31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		33
		34	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	35	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	36	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	37	cb => \&IO::AIO::poll_cb);
24		38
25	# Glib/Gtk2	39	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	40	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb; 1 };	41	in => sub { IO::AIO::poll_cb; 1 };
28		42
29	# Tk	43	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	45	readable => \&IO::AIO::poll_cb);
32		46
33	# Danga::Socket	47	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	49	\&IO::AIO::poll_cb);
36		50
37
38	=head1 DESCRIPTION	51	=head1 DESCRIPTION
39		52
40	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
41	operating system supports.	54	operating system supports.
42		55
43	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
44	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
45	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
46	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
47	aio functions available on many operating systems. However, they are often	60	on many operating systems. However, they are often not well-supported
48	not well-supported (Linux doesn't allow them on normal files currently,	61	(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	62	and they would only support aio_read and aio_write, so the remaining
50	remaining functionality would have to be implemented using threads anyway.	63	functionality would have to be implemented using threads anyway.
51		64
52	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,
53	currently not reentrant, so use appropriate locking yourself, always call	66	it is currently not reentrant in any way, so use appropriate locking
54	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
55	C<aio_> functions) recursively.	68	call C<poll_cb> (or other C<aio_> functions) recursively.
56		69
57	=cut	70	=cut
58		71
59	package IO::AIO;	72	package IO::AIO;
60		73
61	no warnings;	74	no warnings;
		75	use strict 'vars';
62		76
63	use base 'Exporter';	77	use base 'Exporter';
64		78
65	use Fcntl ();
66
67	BEGIN {	79	BEGIN {
68	$VERSION = 1.2;	80	our $VERSION = '2.0';
69		81
70	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	82	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71	aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead);	83	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	84	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		85	aio_group aio_nop);
		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';
73		91
74	require XSLoader;	92	require XSLoader;
75	XSLoader::load IO::AIO, $VERSION;	93	XSLoader::load ("IO::AIO", $VERSION);
76	}	94	}
77		95
78	=head1 FUNCTIONS	96	=head1 FUNCTIONS
79		97
80	=head2 AIO FUNCTIONS	98	=head2 AIO FUNCTIONS
…		…
88	syscall has been executed asynchronously.	106	syscall has been executed asynchronously.
89		107
90	All functions expecting a filehandle keep a copy of the filehandle	108	All functions expecting a filehandle keep a copy of the filehandle
91	internally until the request has finished.	109	internally until the request has finished.
92		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
93	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
94	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
95	request is being executed, the current working directory could have	116	request is being executed, the current working directory could have
96	changed. Alternatively, you can make sure that you never change the	117	changed. Alternatively, you can make sure that you never change the
97	current working directory.	118	current working directory.
…		…
103	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)
104	use something else.	125	use something else.
105		126
106	=over 4	127	=over 4
107		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.
		137
108	=item aio_open $pathname, $flags, $mode, $callback	138	=item aio_open $pathname, $flags, $mode, $callback->($fh)
109		139
110	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
111	created filehandle for the file.	141	created filehandle for the file.
112		142
113	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	143	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
130	} else {	160	} else {
131	die "open failed: $!\n";	161	die "open failed: $!\n";
132	}	162	}
133	};	163	};
134		164
135	=item aio_close $fh, $callback	165	=item aio_close $fh, $callback->($status)
136		166
137	Asynchronously close a file and call the callback with the result	167	Asynchronously close a file and call the callback with the result
138	code. I<WARNING:> although accepted, you should not pass in a perl	168	code. I<WARNING:> although accepted, you should not pass in a perl
139	filehandle here, as perl will likely close the file descriptor another	169	filehandle here, as perl will likely close the file descriptor another
140	time when the filehandle is destroyed. Normally, you can safely call perls	170	time when the filehandle is destroyed. Normally, you can safely call perls
141	C<close> or just let filehandles go out of scope.	171	C<close> or just let filehandles go out of scope.
142		172
143	This is supposed to be a bug in the API, so that might change. It's	173	This is supposed to be a bug in the API, so that might change. It's
144	therefore best to avoid this function.	174	therefore best to avoid this function.
145		175
146	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	176	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
147		177
148	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	178	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149		179
150	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	180	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
151	into the scalar given by C<data> and offset C<dataoffset> and calls the	181	into the scalar given by C<data> and offset C<dataoffset> and calls the
152	callback without the actual number of bytes read (or -1 on error, just	182	callback without the actual number of bytes read (or -1 on error, just
153	like the syscall).	183	like the syscall).
154		184
		185	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		186	is outstanding. Modifying it can result in segfaults or WW3 (if the
		187	necessary/optional hardware is installed).
		188
155	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	189	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
156	offset C<0> within the scalar:	190	offset C<0> within the scalar:
157		191
158	aio_read $fh, 7, 15, $buffer, 0, sub {	192	aio_read $fh, 7, 15, $buffer, 0, sub {
159	$_[0] > 0 or die "read error: $!";	193	$_[0] > 0 or die "read error: $!";
160	print "read $_[0] bytes: <$buffer>\n";	194	print "read $_[0] bytes: <$buffer>\n";
161	};	195	};
162		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
		267	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		268
		269	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		270	reading at byte offset C<$in_offset>, and starts writing at the current
		271	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		272	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		273	other.
		274
		275	This call tries to make use of a native C<sendfile> syscall to provide
		276	zero-copy operation. For this to work, C<$out_fh> should refer to a
		277	socket, and C<$in_fh> should refer to mmap'able file.
		278
		279	If the native sendfile call fails or is not implemented, it will be
		280	emulated, so you can call C<aio_sendfile> on any type of filehandle
		281	regardless of the limitations of the operating system.
		282
		283	Please note, however, that C<aio_sendfile> can read more bytes from
		284	C<$in_fh> than are written, and there is no way to find out how many
		285	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		286	provides the number of bytes written to C<$out_fh>. Only if the result
		287	value equals C<$length> one can assume that C<$length> bytes have been
		288	read.
		289
163	=item aio_readahead $fh,$offset,$length, $callback	290	=item aio_readahead $fh,$offset,$length, $callback->($retval)
164		291
165	C<aio_readahead> populates the page cache with data from a file so that	292	C<aio_readahead> populates the page cache with data from a file so that
166	subsequent reads from that file will not block on disk I/O. The C<$offset>	293	subsequent reads from that file will not block on disk I/O. The C<$offset>
167	argument specifies the starting point from which data is to be read and	294	argument specifies the starting point from which data is to be read and
168	C<$length> specifies the number of bytes to be read. I/O is performed in	295	C<$length> specifies the number of bytes to be read. I/O is performed in
…		…
172	file. The current file offset of the file is left unchanged.	299	file. The current file offset of the file is left unchanged.
173		300
174	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	301	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
175	emulated by simply reading the data, which would have a similar effect.	302	emulated by simply reading the data, which would have a similar effect.
176		303
177	=item aio_stat $fh_or_path, $callback	304	=item aio_stat $fh_or_path, $callback->($status)
178		305
179	=item aio_lstat $fh, $callback	306	=item aio_lstat $fh, $callback->($status)
180		307
181	Works like perl's C<stat> or C<lstat> in void context. The callback will	308	Works like perl's C<stat> or C<lstat> in void context. The callback will
182	be called after the stat and the results will be available using C<stat _>	309	be called after the stat and the results will be available using C<stat _>
183	or C<-s _> etc...	310	or C<-s _> etc...
184		311
…		…
194	aio_stat "/etc/passwd", sub {	321	aio_stat "/etc/passwd", sub {
195	$_[0] and die "stat failed: $!";	322	$_[0] and die "stat failed: $!";
196	print "size is ", -s _, "\n";	323	print "size is ", -s _, "\n";
197	};	324	};
198		325
199	=item aio_unlink $pathname, $callback	326	=item aio_unlink $pathname, $callback->($status)
200		327
201	Asynchronously unlink (delete) a file and call the callback with the	328	Asynchronously unlink (delete) a file and call the callback with the
202	result code.	329	result code.
203		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
204	=item aio_rmdir $pathname, $callback	346	=item aio_rmdir $pathname, $callback->($status)
205		347
206	Asynchronously rmdir (delete) a directory and call the callback with the	348	Asynchronously rmdir (delete) a directory and call the callback with the
207	result code.	349	result code.
208		350
		351	=item aio_readdir $pathname, $callback->($entries)
		352
		353	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		354	directory (i.e. opendir + readdir + closedir). The entries will not be
		355	sorted, and will B<NOT> include the C<.> and C<..> entries.
		356
		357	The callback a single argument which is either C<undef> or an array-ref
		358	with the filenames.
		359
		360	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		361
		362	[EXPERIMENTAL due to internal aio_group use]
		363
		364	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		365	separate the entries of directory C<$path> into two sets of names, ones
		366	you can recurse into (directories or links to them), and ones you cannot
		367	recurse into (everything else).
		368
		369	C<aio_scandir> is a composite request that creates of many sub requests_
		370	C<$maxreq> specifies the maximum number of outstanding aio requests that
		371	this function generates. If it is C<< <= 0 >>, then a suitable default
		372	will be chosen (currently 6).
		373
		374	On error, the callback is called without arguments, otherwise it receives
		375	two array-refs with path-relative entry names.
		376
		377	Example:
		378
		379	aio_scandir $dir, 0, sub {
		380	my ($dirs, $nondirs) = @_;
		381	print "real directories: @$dirs\n";
		382	print "everything else: @$nondirs\n";
		383	};
		384
		385	Implementation notes.
		386
		387	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		388
		389	After reading the directory, the modification time, size etc. of the
		390	directory before and after the readdir is checked, and if they match (and
		391	isn't the current time), the link count will be used to decide how many
		392	entries are directories (if >= 2). Otherwise, no knowledge of the number
		393	of subdirectories will be assumed.
		394
		395	Then entries will be sorted into likely directories (everything without
		396	a non-initial dot currently) and likely non-directories (everything
		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
		401	filesystems might detect the type of the entry without reading the inode
		402	data (e.g. ext2fs filetype feature).
		403
		404	If the known number of directories (link count - 2) has been reached, the
		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.
		413
		414	=cut
		415
		416	sub aio_scandir($$$) {
		417	my ($path, $maxreq, $cb) = @_;
		418
		419	my $grp = aio_group $cb;
		420
		421	$maxreq = 6 if $maxreq <= 0;
		422
		423	# stat once
		424	add $grp aio_stat $path, sub {
		425	return $grp->result () if $_[0];
		426	my $now = time;
		427	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		428
		429	# read the directory entries
		430	add $grp aio_readdir $path, sub {
		431	my $entries = shift
		432	or return $grp->result ();
		433
		434	# stat the dir another time
		435	add $grp aio_stat $path, sub {
		436	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		437
		438	my $ndirs;
		439
		440	# take the slow route if anything looks fishy
		441	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		442	$ndirs = -1;
		443	} else {
		444	# if nlink == 2, we are finished
		445	# on non-posix-fs's, we rely on nlink < 2
		446	$ndirs = (stat _)[3] - 2
		447	or return $grp->result ([], $entries);
		448	}
		449
		450	# sort into likely dirs and likely nondirs
		451	# dirs == files without ".", short entries first
		452	$entries = [map $_->[0],
		453	sort { $b->[1] cmp $a->[1] }
		454	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		455	@$entries];
		456
		457	my (@dirs, @nondirs);
		458
		459	my ($statcb, $schedcb);
		460	my $nreq = 0;
		461
		462	my $statgrp = add $grp aio_group;
		463
		464	$schedcb = sub {
		465	if (@$entries) {
		466	if ($nreq < $maxreq) {
		467	my $ent = pop @$entries;
		468	$nreq++;
		469	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		470	}
		471	} elsif (!$nreq) {
		472	# finished
		473	$statgrp->cancel;
		474	undef $statcb;
		475	undef $schedcb;
		476	$grp->result (\@dirs, \@nondirs);
		477	}
		478	};
		479	$statcb = sub {
		480	my ($status, $entry) = @_;
		481
		482	if ($status < 0) {
		483	$nreq--;
		484	push @nondirs, $entry;
		485	&$schedcb;
		486	} else {
		487	# need to check for real directory
		488	add $grp aio_lstat "$path/$entry", sub {
		489	$nreq--;
		490
		491	if (-d _) {
		492	push @dirs, $entry;
		493
		494	if (!--$ndirs) {
		495	push @nondirs, @$entries;
		496	$entries = [];
		497	}
		498	} else {
		499	push @nondirs, $entry;
		500	}
		501
		502	&$schedcb;
		503	}
		504	}
		505	};
		506
		507	&$schedcb while @$entries && $nreq < $maxreq;
		508	};
		509	};
		510	};
		511
		512	$grp
		513	}
		514
209	=item aio_fsync $fh, $callback	515	=item aio_fsync $fh, $callback->($status)
210		516
211	Asynchronously call fsync on the given filehandle and call the callback	517	Asynchronously call fsync on the given filehandle and call the callback
212	with the fsync result code.	518	with the fsync result code.
213		519
214	=item aio_fdatasync $fh, $callback	520	=item aio_fdatasync $fh, $callback->($status)
215		521
216	Asynchronously call fdatasync on the given filehandle and call the	522	Asynchronously call fdatasync on the given filehandle and call the
217	callback with the fdatasync result code.	523	callback with the fdatasync result code.
218		524
219	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
220	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.
221		727
222	=back	728	=back
223		729
224	=head2 SUPPORT FUNCTIONS	730	=head2 SUPPORT FUNCTIONS
225		731
…		…
283	IO::AIO::poll_wait, IO::AIO::poll_cb	789	IO::AIO::poll_wait, IO::AIO::poll_cb
284	if IO::AIO::nreqs;	790	if IO::AIO::nreqs;
285		791
286	=item IO::AIO::min_parallel $nthreads	792	=item IO::AIO::min_parallel $nthreads
287		793
288	Set the minimum number of AIO threads to C<$nthreads>. The default is	794	Set the minimum number of AIO threads to C<$nthreads>. The current
289	C<1>, which means a single asynchronous operation can be done at one time	795	default is C<8>, which means eight asynchronous operations can execute
290	(the number of outstanding operations, however, is unlimited).	796	concurrently at any one time (the number of outstanding requests,
		797	however, is unlimited).
291		798
		799	IO::AIO starts threads only on demand, when an AIO request is queued and
		800	no free thread exists.
		801
292	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
293	kernel versions will scale negatively with the number of threads (higher	803	Linux kernel versions will scale negatively with the number of threads
294	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	804	(higher parallelity => MUCH higher latency). With current Linux 2.6
295	threads should be fine.	805	versions, 4-32 threads should be fine.
296		806
297	Under normal circumstances you don't need to call this function, as this	807	Under most circumstances you don't need to call this function, as the
298	module automatically starts some threads (the exact number might change,	808	module selects a default that is suitable for low to moderate load.
299	and is currently 4).
300		809
301	=item IO::AIO::max_parallel $nthreads	810	=item IO::AIO::max_parallel $nthreads
302		811
303	Sets the maximum number of AIO threads to C<$nthreads>. If more than	812	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
304	the specified number of threads are currently running, kill them. This	813	specified number of threads are currently running, this function kills
305	function blocks until the limit is reached.	814	them. This function blocks until the limit is reached.
		815
		816	While C<$nthreads> are zero, aio requests get queued but not executed
		817	until the number of threads has been increased again.
306		818
307	This module automatically runs C<max_parallel 0> at program end, to ensure	819	This module automatically runs C<max_parallel 0> at program end, to ensure
308	that all threads are killed and that there are no outstanding requests.	820	that all threads are killed and that there are no outstanding requests.
309		821
310	Under normal circumstances you don't need to call this function.	822	Under normal circumstances you don't need to call this function.
311		823
312	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	824	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		825
		826	[DEPRECATED]
313		827
314	Sets the maximum number of outstanding requests to C<$nreqs>. If you	828	Sets the maximum number of outstanding requests to C<$nreqs>. If you
315	try to queue up more than this number of requests, the caller will block until	829	try to queue up more than this number of requests, the caller will block until
316	some requests have been handled.	830	some requests have been handled.
317		831
318	The default is very large, so normally there is no practical limit. If you	832	The default is very large, so normally there is no practical limit. If you
319	queue up many requests in a loop it it often improves speed if you set	833	queue up many requests in a loop it often improves speed if you set
320	this to a relatively low number, such as C<100>.	834	this to a relatively low number, such as C<100>.
		835
		836	This function does not work well together with C<aio_group>'s, and their
		837	feeder interface is better suited to limiting concurrency, so do not use
		838	this function.
321		839
322	Under normal circumstances you don't need to call this function.	840	Under normal circumstances you don't need to call this function.
323		841
324	=back	842	=back
325		843
…		…
339	or return undef;	857	or return undef;
340		858
341	*$sym	859	*$sym
342	}	860	}
343		861
344	min_parallel 4;	862	min_parallel 8;
345		863
346	END {	864	END {
347	max_parallel 0;	865	max_parallel 0;
348	}	866	}
349		867
350	1;	868	1;
351		869
352	=head2 FORK BEHAVIOUR	870	=head2 FORK BEHAVIOUR
353		871
354	Before the fork IO::AIO first handles all outstanding requests - if other	872	This module should do "the right thing" when the process using it forks:
355	threads add requests during this period, this time is prolonged. It then	873
356	enters a quiescent state where no requests can be added in other threads	874	Before the fork, IO::AIO enters a quiescent state where no requests
357	and no results will be processed. After the fork the parent simply leaves	875	can be added in other threads and no results will be processed. After
358	the quiescent state and continues request processing, while the child	876	the fork the parent simply leaves the quiescent state and continues
359	starts the same number of threads as were in use by the parent.	877	request/result processing, while the child clears the request/result
		878	queue (so the requests started before the fork will only be handled in
		879	the parent). Threads will be started on demand until the limit ste in the
		880	parent process has been reached again.
		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.
360		898
361	=head1 SEE ALSO	899	=head1 SEE ALSO
362		900
363	L<Coro>, L<Linux::AIO>.	901	L<Coro::AIO>.
364		902
365	=head1 AUTHOR	903	=head1 AUTHOR
366		904
367	Marc Lehmann <schmorp@schmorp.de>	905	Marc Lehmann <schmorp@schmorp.de>
368	http://home.schmorp.de/	906	http://home.schmorp.de/

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Revision 1.68 by root, Tue Oct 24 03:17:39 2006 UTC