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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.21 by root, Wed Jul 13 00:13:09 2005 UTC vs.
Revision 1.67 by root, Tue Oct 24 02:25:16 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.	65	currently not reentrant, so use appropriate locking yourself, always call
		66	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other
		67	C<aio_> functions) recursively.
54		68
55	=cut	69	=cut
56		70
57	package IO::AIO;	71	package IO::AIO;
58		72
		73	no warnings;
		74	use strict 'vars';
		75
59	use base 'Exporter';	76	use base 'Exporter';
60		77
61	use Fcntl ();
62
63	BEGIN {	78	BEGIN {
64	$VERSION = 0.9;	79	our $VERSION = '2.0';
65		80
66	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	81	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
67	aio_fsync aio_fdatasync aio_readahead);	82	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
68	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		84	aio_group aio_nop);
		85	our @EXPORT = (@AIO_REQ, qw(aioreq_pri));
		86	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		87	min_parallel max_parallel max_outstanding nreqs);
		88
		89	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
69		90
70	require XSLoader;	91	require XSLoader;
71	XSLoader::load IO::AIO, $VERSION;	92	XSLoader::load ("IO::AIO", $VERSION);
72	}	93	}
73		94
74	=head1 FUNCTIONS	95	=head1 FUNCTIONS
75		96
76	=head2 AIO FUNCTIONS	97	=head2 AIO FUNCTIONS
…		…
81	which must be a code reference. This code reference will get called with	102	which must be a code reference. This code reference will get called with
82	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	103	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
83	perl, which usually delivers "false") as it's sole argument when the given	104	perl, which usually delivers "false") as it's sole argument when the given
84	syscall has been executed asynchronously.	105	syscall has been executed asynchronously.
85		106
86	All functions that expect a filehandle will also accept a file descriptor.	107	All functions expecting a filehandle keep a copy of the filehandle
		108	internally until the request has finished.
87		109
		110	All requests return objects of type L<IO::AIO::REQ> that allow further
		111	manipulation of those requests while they are in-flight.
		112
88	The filenames you pass to these routines I<must> be absolute. The reason	113	The pathnames you pass to these routines I<must> be absolute and
89	for this is that at the time the request is being executed, the current	114	encoded in byte form. The reason for the former is that at the time the
90	working directory could have changed. Alternatively, you can make sure	115	request is being executed, the current working directory could have
91	that you never change the current working directory.	116	changed. Alternatively, you can make sure that you never change the
		117	current working directory.
		118
		119	To encode pathnames to byte form, either make sure you either: a)
		120	always pass in filenames you got from outside (command line, readdir
		121	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		122	your pathnames to the locale (or other) encoding in effect in the user
		123	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		124	use something else.
92		125
93	=over 4	126	=over 4
94		127
95	=item aio_open $pathname, $flags, $mode, $callback	128	=item aio_open $pathname, $flags, $mode, $callback->($fh)
96		129
97	Asynchronously open or create a file and call the callback with a newly	130	Asynchronously open or create a file and call the callback with a newly
98	created filehandle for the file.	131	created filehandle for the file.
99		132
100	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	133	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
117	} else {	150	} else {
118	die "open failed: $!\n";	151	die "open failed: $!\n";
119	}	152	}
120	};	153	};
121		154
122	=item aio_close $fh, $callback	155	=item aio_close $fh, $callback->($status)
123		156
124	Asynchronously close a file and call the callback with the result	157	Asynchronously close a file and call the callback with the result
125	code. I<WARNING:> although accepted, you should not pass in a perl	158	code. I<WARNING:> although accepted, you should not pass in a perl
126	filehandle here, as perl will likely close the file descriptor another	159	filehandle here, as perl will likely close the file descriptor another
127	time when the filehandle is destroyed. Normally, you can safely call perls	160	time when the filehandle is destroyed. Normally, you can safely call perls
128	C<close> or just let filehandles go out of scope.	161	C<close> or just let filehandles go out of scope.
129		162
130	This is supposed to be a bug in the API, so that might change. It's	163	This is supposed to be a bug in the API, so that might change. It's
131	therefore best to avoid this function.	164	therefore best to avoid this function.
132		165
133	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	166	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
134		167
135	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	168	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
136		169
137	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	170	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
138	into the scalar given by C<data> and offset C<dataoffset> and calls the	171	into the scalar given by C<data> and offset C<dataoffset> and calls the
139	callback without the actual number of bytes read (or -1 on error, just	172	callback without the actual number of bytes read (or -1 on error, just
140	like the syscall).	173	like the syscall).
141		174
		175	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		176	is outstanding. Modifying it can result in segfaults or WW3 (if the
		177	necessary/optional hardware is installed).
		178
142	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	179	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
143	offset C<0> within the scalar:	180	offset C<0> within the scalar:
144		181
145	aio_read $fh, 7, 15, $buffer, 0, sub {	182	aio_read $fh, 7, 15, $buffer, 0, sub {
146	$_[0] > 0 or die "read error: $!";	183	$_[0] > 0 or die "read error: $!";
147	print "read $_[0] bytes: <$buffer>\n";	184	print "read $_[0] bytes: <$buffer>\n";
148	};	185	};
149		186
		187	=item aio_move $srcpath, $dstpath, $callback->($status)
		188
		189	[EXPERIMENTAL due to internal aio_group use]
		190
		191	Try to move the I<file> (directories not supported as either source or
		192	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		193	the C<0> (error) or C<-1> ok.
		194
		195	This is a composite request that tries to rename(2) the file first. If
		196	rename files with C<EXDEV>, it creates the destination file with mode 0200
		197	and copies the contents of the source file into it using C<aio_sendfile>,
		198	followed by restoring atime, mtime, access mode and uid/gid, in that
		199	order, and unlinking the C<$srcpath>.
		200
		201	If an error occurs, the partial destination file will be unlinked, if
		202	possible, except when setting atime, mtime, access mode and uid/gid, where
		203	errors are being ignored.
		204
		205	=cut
		206
		207	sub aio_move($$$) {
		208	my ($src, $dst, $cb) = @_;
		209
		210	my $grp = aio_group $cb;
		211
		212	add $grp aio_rename $src, $dst, sub {
		213	if ($_[0] && $! == EXDEV) {
		214	add $grp aio_open $src, O_RDONLY, 0, sub {
		215	if (my $src_fh = $_[0]) {
		216	my @stat = stat $src_fh;
		217
		218	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		219	if (my $dst_fh = $_[0]) {
		220	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		221	close $src_fh;
		222
		223	if ($_[0] == $stat[7]) {
		224	utime $stat[8], $stat[9], $dst;
		225	chmod $stat[2] & 07777, $dst_fh;
		226	chown $stat[4], $stat[5], $dst_fh;
		227	close $dst_fh;
		228
		229	add $grp aio_unlink $src, sub {
		230	$grp->result ($_[0]);
		231	};
		232	} else {
		233	my $errno = $!;
		234	add $grp aio_unlink $dst, sub {
		235	$! = $errno;
		236	$grp->result (-1);
		237	};
		238	}
		239	};
		240	} else {
		241	$grp->result (-1);
		242	}
		243	},
		244
		245	} else {
		246	$grp->result (-1);
		247	}
		248	};
		249	} else {
		250	$grp->result ($_[0]);
		251	}
		252	};
		253
		254	$grp
		255	}
		256
		257	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		258
		259	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		260	reading at byte offset C<$in_offset>, and starts writing at the current
		261	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		262	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		263	other.
		264
		265	This call tries to make use of a native C<sendfile> syscall to provide
		266	zero-copy operation. For this to work, C<$out_fh> should refer to a
		267	socket, and C<$in_fh> should refer to mmap'able file.
		268
		269	If the native sendfile call fails or is not implemented, it will be
		270	emulated, so you can call C<aio_sendfile> on any type of filehandle
		271	regardless of the limitations of the operating system.
		272
		273	Please note, however, that C<aio_sendfile> can read more bytes from
		274	C<$in_fh> than are written, and there is no way to find out how many
		275	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		276	provides the number of bytes written to C<$out_fh>. Only if the result
		277	value equals C<$length> one can assume that C<$length> bytes have been
		278	read.
		279
150	=item aio_readahead $fh,$offset,$length, $callback	280	=item aio_readahead $fh,$offset,$length, $callback->($retval)
151
152	Asynchronously reads the specified byte range into the page cache, using
153	the C<readahead> syscall. If that syscall doesn't exist (likely if your OS
154	isn't Linux) the status will be C<-1> and C<$!> is set to C<ENOSYS>.
155		281
156	C<aio_readahead> populates the page cache with data from a file so that	282	C<aio_readahead> populates the page cache with data from a file so that
157	subsequent reads from that file will not block on disk I/O. The C<$offset>	283	subsequent reads from that file will not block on disk I/O. The C<$offset>
158	argument specifies the starting point from which data is to be read and	284	argument specifies the starting point from which data is to be read and
159	C<$length> specifies the number of bytes to be read. I/O is performed in	285	C<$length> specifies the number of bytes to be read. I/O is performed in
160	whole pages, so that offset is effectively rounded down to a page boundary	286	whole pages, so that offset is effectively rounded down to a page boundary
161	and bytes are read up to the next page boundary greater than or equal to	287	and bytes are read up to the next page boundary greater than or equal to
162	(off-set+length). C<aio_readahead> does not read beyond the end of the	288	(off-set+length). C<aio_readahead> does not read beyond the end of the
163	file. The current file offset of the file is left unchanged.	289	file. The current file offset of the file is left unchanged.
164		290
		291	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		292	emulated by simply reading the data, which would have a similar effect.
		293
165	=item aio_stat $fh_or_path, $callback	294	=item aio_stat $fh_or_path, $callback->($status)
166		295
167	=item aio_lstat $fh, $callback	296	=item aio_lstat $fh, $callback->($status)
168		297
169	Works like perl's C<stat> or C<lstat> in void context. The callback will	298	Works like perl's C<stat> or C<lstat> in void context. The callback will
170	be called after the stat and the results will be available using C<stat _>	299	be called after the stat and the results will be available using C<stat _>
171	or C<-s _> etc...	300	or C<-s _> etc...
172		301
…		…
182	aio_stat "/etc/passwd", sub {	311	aio_stat "/etc/passwd", sub {
183	$_[0] and die "stat failed: $!";	312	$_[0] and die "stat failed: $!";
184	print "size is ", -s _, "\n";	313	print "size is ", -s _, "\n";
185	};	314	};
186		315
187	=item aio_unlink $pathname, $callback	316	=item aio_unlink $pathname, $callback->($status)
188		317
189	Asynchronously unlink (delete) a file and call the callback with the	318	Asynchronously unlink (delete) a file and call the callback with the
190	result code.	319	result code.
191		320
		321	=item aio_link $srcpath, $dstpath, $callback->($status)
		322
		323	Asynchronously create a new link to the existing object at C<$srcpath> at
		324	the path C<$dstpath> and call the callback with the result code.
		325
		326	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		327
		328	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		329	the path C<$dstpath> and call the callback with the result code.
		330
		331	=item aio_rename $srcpath, $dstpath, $callback->($status)
		332
		333	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		334	rename(2) and call the callback with the result code.
		335
		336	=item aio_rmdir $pathname, $callback->($status)
		337
		338	Asynchronously rmdir (delete) a directory and call the callback with the
		339	result code.
		340
		341	=item aio_readdir $pathname, $callback->($entries)
		342
		343	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		344	directory (i.e. opendir + readdir + closedir). The entries will not be
		345	sorted, and will B<NOT> include the C<.> and C<..> entries.
		346
		347	The callback a single argument which is either C<undef> or an array-ref
		348	with the filenames.
		349
		350	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		351
		352	[EXPERIMENTAL due to internal aio_group use]
		353
		354	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		355	separate the entries of directory C<$path> into two sets of names, ones
		356	you can recurse into (directories or links to them), and ones you cannot
		357	recurse into (everything else).
		358
		359	C<aio_scandir> is a composite request that creates of many sub requests_
		360	C<$maxreq> specifies the maximum number of outstanding aio requests that
		361	this function generates. If it is C<< <= 0 >>, then a suitable default
		362	will be chosen (currently 6).
		363
		364	On error, the callback is called without arguments, otherwise it receives
		365	two array-refs with path-relative entry names.
		366
		367	Example:
		368
		369	aio_scandir $dir, 0, sub {
		370	my ($dirs, $nondirs) = @_;
		371	print "real directories: @$dirs\n";
		372	print "everything else: @$nondirs\n";
		373	};
		374
		375	Implementation notes.
		376
		377	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		378
		379	After reading the directory, the modification time, size etc. of the
		380	directory before and after the readdir is checked, and if they match (and
		381	isn't the current time), the link count will be used to decide how many
		382	entries are directories (if >= 2). Otherwise, no knowledge of the number
		383	of subdirectories will be assumed.
		384
		385	Then entries will be sorted into likely directories (everything without
		386	a non-initial dot currently) and likely non-directories (everything
		387	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		388	likely directories first. If that succeeds, it assumes that the entry
		389	is a directory or a symlink to directory (which will be checked
		390	seperately). This is often faster than stat'ing the entry itself because
		391	filesystems might detect the type of the entry without reading the inode
		392	data (e.g. ext2fs filetype feature).
		393
		394	If the known number of directories (link count - 2) has been reached, the
		395	rest of the entries is assumed to be non-directories.
		396
		397	This only works with certainty on POSIX (= UNIX) filesystems, which
		398	fortunately are the vast majority of filesystems around.
		399
		400	It will also likely work on non-POSIX filesystems with reduced efficiency
		401	as those tend to return 0 or 1 as link counts, which disables the
		402	directory counting heuristic.
		403
		404	=cut
		405
		406	sub aio_scandir($$$) {
		407	my ($path, $maxreq, $cb) = @_;
		408
		409	my $grp = aio_group $cb;
		410
		411	$maxreq = 6 if $maxreq <= 0;
		412
		413	# stat once
		414	add $grp aio_stat $path, sub {
		415	return $grp->result () if $_[0];
		416	my $now = time;
		417	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		418
		419	# read the directory entries
		420	add $grp aio_readdir $path, sub {
		421	my $entries = shift
		422	or return $grp->result ();
		423
		424	# stat the dir another time
		425	add $grp aio_stat $path, sub {
		426	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		427
		428	my $ndirs;
		429
		430	# take the slow route if anything looks fishy
		431	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		432	$ndirs = -1;
		433	} else {
		434	# if nlink == 2, we are finished
		435	# on non-posix-fs's, we rely on nlink < 2
		436	$ndirs = (stat _)[3] - 2
		437	or return $grp->result ([], $entries);
		438	}
		439
		440	# sort into likely dirs and likely nondirs
		441	# dirs == files without ".", short entries first
		442	$entries = [map $_->[0],
		443	sort { $b->[1] cmp $a->[1] }
		444	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		445	@$entries];
		446
		447	my (@dirs, @nondirs);
		448
		449	my ($statcb, $schedcb);
		450	my $nreq = 0;
		451
		452	my $statgrp = add $grp aio_group;
		453
		454	$schedcb = sub {
		455	if (@$entries) {
		456	if ($nreq < $maxreq) {
		457	my $ent = pop @$entries;
		458	$nreq++;
		459	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		460	}
		461	} elsif (!$nreq) {
		462	# finished
		463	$statgrp->cancel;
		464	undef $statcb;
		465	undef $schedcb;
		466	$grp->result (\@dirs, \@nondirs);
		467	}
		468	};
		469	$statcb = sub {
		470	my ($status, $entry) = @_;
		471
		472	if ($status < 0) {
		473	$nreq--;
		474	push @nondirs, $entry;
		475	&$schedcb;
		476	} else {
		477	# need to check for real directory
		478	add $grp aio_lstat "$path/$entry", sub {
		479	$nreq--;
		480
		481	if (-d _) {
		482	push @dirs, $entry;
		483
		484	if (!--$ndirs) {
		485	push @nondirs, @$entries;
		486	$entries = [];
		487	}
		488	} else {
		489	push @nondirs, $entry;
		490	}
		491
		492	&$schedcb;
		493	}
		494	}
		495	};
		496
		497	&$schedcb while @$entries && $nreq < $maxreq;
		498	};
		499	};
		500	};
		501
		502	$grp
		503	}
		504
192	=item aio_fsync $fh, $callback	505	=item aio_fsync $fh, $callback->($status)
193		506
194	Asynchronously call fsync on the given filehandle and call the callback	507	Asynchronously call fsync on the given filehandle and call the callback
195	with the fsync result code.	508	with the fsync result code.
196		509
197	=item aio_fdatasync $fh, $callback	510	=item aio_fdatasync $fh, $callback->($status)
198		511
199	Asynchronously call fdatasync on the given filehandle and call the	512	Asynchronously call fdatasync on the given filehandle and call the
200	callback with the fdatasync result code. Might set C<$!> to C<ENOSYS> if	513	callback with the fdatasync result code.
201	C<fdatasync> is not available.	514
		515	If this call isn't available because your OS lacks it or it couldn't be
		516	detected, it will be emulated by calling C<fsync> instead.
		517
		518	=item aio_group $callback->(...)
		519
		520	[EXPERIMENTAL]
		521
		522	This is a very special aio request: Instead of doing something, it is a
		523	container for other aio requests, which is useful if you want to bundle
		524	many requests into a single, composite, request.
		525
		526	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		527	for more info.
		528
		529	Example:
		530
		531	my $grp = aio_group sub {
		532	print "all stats done\n";
		533	};
		534
		535	add $grp
		536	(aio_stat ...),
		537	(aio_stat ...),
		538	...;
		539
		540	=item aio_nop $callback->()
		541
		542	This is a special request - it does nothing in itself and is only used for
		543	side effects, such as when you want to add a dummy request to a group so
		544	that finishing the requests in the group depends on executing the given
		545	code.
		546
		547	While this request does nothing, it still goes through the execution
		548	phase and still requires a worker thread. Thus, the callback will not
		549	be executed immediately but only after other requests in the queue have
		550	entered their execution phase. This can be used to measure request
		551	latency.
		552
		553	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		554
		555	Mainly used for debugging and benchmarking, this aio request puts one of
		556	the request workers to sleep for the given time.
		557
		558	While it is theoretically handy to have simple I/O scheduling requests
		559	like sleep and file handle readable/writable, the overhead this creates
		560	is immense, so do not use this function except to put your application
		561	under artificial I/O pressure.
		562
		563	=back
		564
		565	=head2 IO::AIO::REQ CLASS
		566
		567	All non-aggregate C<aio_*> functions return an object of this class when
		568	called in non-void context.
		569
		570	A request always moves through the following five states in its lifetime,
		571	in order: B<ready> (request has been created, but has not been executed
		572	yet), B<execute> (request is currently being executed), B<pending>
		573	(request has been executed but callback has not been called yet),
		574	B<result> (results are being processed synchronously, includes calling the
		575	callback) and B<done> (request has reached the end of its lifetime and
		576	holds no resources anymore).
		577
		578	=over 4
		579
		580	=item cancel $req
		581
		582	Cancels the request, if possible. Has the effect of skipping execution
		583	when entering the B<execute> state and skipping calling the callback when
		584	entering the the B<result> state, but will leave the request otherwise
		585	untouched. That means that requests that currently execute will not be
		586	stopped and resources held by the request will not be freed prematurely.
		587
		588	=item cb $req $callback->(...)
		589
		590	Replace (or simply set) the callback registered to the request.
		591
		592	=back
		593
		594	=head2 IO::AIO::GRP CLASS
		595
		596	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		597	objects of this class, too.
		598
		599	A IO::AIO::GRP object is a special request that can contain multiple other
		600	aio requests.
		601
		602	You create one by calling the C<aio_group> constructing function with a
		603	callback that will be called when all contained requests have entered the
		604	C<done> state:
		605
		606	my $grp = aio_group sub {
		607	print "all requests are done\n";
		608	};
		609
		610	You add requests by calling the C<add> method with one or more
		611	C<IO::AIO::REQ> objects:
		612
		613	$grp->add (aio_unlink "...");
		614
		615	add $grp aio_stat "...", sub {
		616	$_[0] or return $grp->result ("error");
		617
		618	# add another request dynamically, if first succeeded
		619	add $grp aio_open "...", sub {
		620	$grp->result ("ok");
		621	};
		622	};
		623
		624	This makes it very easy to create composite requests (see the source of
		625	C<aio_move> for an application) that work and feel like simple requests.
		626
		627	=over 4
		628
		629	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		630	C<IO::AIO::poll_cb>, just like any other request.
		631
		632	=item * They can be canceled like any other request. Canceling will cancel not
		633	only the request itself, but also all requests it contains.
		634
		635	=item * They can also can also be added to other IO::AIO::GRP objects.
		636
		637	=item * You must not add requests to a group from within the group callback (or
		638	any later time).
		639
		640	=item * This does not harmonise well with C<max_outstanding>, so best do
		641	not combine C<aio_group> with it. Groups and feeders are recommended for
		642	this kind of concurrency-limiting.
		643
		644	=back
		645
		646	Their lifetime, simplified, looks like this: when they are empty, they
		647	will finish very quickly. If they contain only requests that are in the
		648	C<done> state, they will also finish. Otherwise they will continue to
		649	exist.
		650
		651	That means after creating a group you have some time to add requests. And
		652	in the callbacks of those requests, you can add further requests to the
		653	group. And only when all those requests have finished will the the group
		654	itself finish.
		655
		656	=over 4
		657
		658	=item add $grp ...
		659
		660	=item $grp->add (...)
		661
		662	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		663	be added, including other groups, as long as you do not create circular
		664	dependencies.
		665
		666	Returns all its arguments.
		667
		668	=item $grp->result (...)
		669
		670	Set the result value(s) that will be passed to the group callback when all
		671	subrequests have finished. By default, no argument will be passed.
		672
		673	=item feed $grp $callback->($grp)
		674
		675	[VERY EXPERIMENTAL]
		676
		677	Sets a feeder/generator on this group: every group can have an attached
		678	generator that generates requests if idle. The idea behind this is that,
		679	although you could just queue as many requests as you want in a group,
		680	this might starve other requests for a potentially long time. For
		681	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		682	requests, delaying any later requests for a long time.
		683
		684	To avoid this, and allow incremental generation of requests, you can
		685	instead a group and set a feeder on it that generates those requests. The
		686	feed callback will be called whenever there are few enough (see C<feed_limit>,
		687	below) requests active in the group itself and is expected to queue more
		688	requests.
		689
		690	The feed can queue as many requests as it likes (i.e. C<add> does not
		691	impose any limits).
		692
		693	If the feed does not queue more requests when called, it will be
		694	automatically removed from the group.
		695
		696	If the feed limit is C<0>, it will be set to C<2> automatically.
		697
		698	Example:
		699
		700	# stat all files in @files, but only ever use four aio requests concurrently:
		701
		702	my $grp = aio_group sub { print "finished\n" };
		703	feed_limit $grp 4;
		704	feed $grp sub {
		705	my $file = pop @files
		706	or return;
		707
		708	add $grp aio_stat $file, sub { ... };
		709	};
		710
		711	=item feed_limit $grp $num
		712
		713	Sets the feeder limit for the group: The feeder will be called whenever
		714	the group contains less than this many requests.
		715
		716	Setting the limit to C<0> will pause the feeding process.
202		717
203	=back	718	=back
204		719
205	=head2 SUPPORT FUNCTIONS	720	=head2 SUPPORT FUNCTIONS
206		721
…		…
264	IO::AIO::poll_wait, IO::AIO::poll_cb	779	IO::AIO::poll_wait, IO::AIO::poll_cb
265	if IO::AIO::nreqs;	780	if IO::AIO::nreqs;
266		781
267	=item IO::AIO::min_parallel $nthreads	782	=item IO::AIO::min_parallel $nthreads
268		783
269	Set the minimum number of AIO threads to C<$nthreads>. The default is	784	Set the minimum number of AIO threads to C<$nthreads>. The current
270	C<1>, which means a single asynchronous operation can be done at one time	785	default is C<8>, which means eight asynchronous operations can execute
271	(the number of outstanding operations, however, is unlimited).	786	concurrently at any one time (the number of outstanding requests,
		787	however, is unlimited).
272		788
		789	IO::AIO starts threads only on demand, when an AIO request is queued and
		790	no free thread exists.
		791
273	It is recommended to keep the number of threads low, as some Linux	792	It is recommended to keep the number of threads relatively low, as some
274	kernel versions will scale negatively with the number of threads (higher	793	Linux kernel versions will scale negatively with the number of threads
275	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	794	(higher parallelity => MUCH higher latency). With current Linux 2.6
276	threads should be fine.	795	versions, 4-32 threads should be fine.
277		796
278	Under normal circumstances you don't need to call this function, as this	797	Under most circumstances you don't need to call this function, as the
279	module automatically starts some threads (the exact number might change,	798	module selects a default that is suitable for low to moderate load.
280	and is currently 4).
281		799
282	=item IO::AIO::max_parallel $nthreads	800	=item IO::AIO::max_parallel $nthreads
283		801
284	Sets the maximum number of AIO threads to C<$nthreads>. If more than	802	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
285	the specified number of threads are currently running, kill them. This	803	specified number of threads are currently running, this function kills
286	function blocks until the limit is reached.	804	them. This function blocks until the limit is reached.
		805
		806	While C<$nthreads> are zero, aio requests get queued but not executed
		807	until the number of threads has been increased again.
287		808
288	This module automatically runs C<max_parallel 0> at program end, to ensure	809	This module automatically runs C<max_parallel 0> at program end, to ensure
289	that all threads are killed and that there are no outstanding requests.	810	that all threads are killed and that there are no outstanding requests.
290		811
291	Under normal circumstances you don't need to call this function.	812	Under normal circumstances you don't need to call this function.
292		813
293	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	814	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		815
		816	[DEPRECATED]
294		817
295	Sets the maximum number of outstanding requests to C<$nreqs>. If you	818	Sets the maximum number of outstanding requests to C<$nreqs>. If you
296	try to queue up more than this number of requests, the caller will block until	819	try to queue up more than this number of requests, the caller will block until
297	some requests have been handled.	820	some requests have been handled.
298		821
299	The default is very large, so normally there is no practical limit. If you	822	The default is very large, so normally there is no practical limit. If you
300	queue up many requests in a loop it it often improves speed if you set	823	queue up many requests in a loop it often improves speed if you set
301	this to a relatively low number, such as C<100>.	824	this to a relatively low number, such as C<100>.
		825
		826	This function does not work well together with C<aio_group>'s, and their
		827	feeder interface is better suited to limiting concurrency, so do not use
		828	this function.
302		829
303	Under normal circumstances you don't need to call this function.	830	Under normal circumstances you don't need to call this function.
304		831
305	=back	832	=back
306		833
…		…
308		835
309	# support function to convert a fd into a perl filehandle	836	# support function to convert a fd into a perl filehandle
310	sub _fd2fh {	837	sub _fd2fh {
311	return undef if $_[0] < 0;	838	return undef if $_[0] < 0;
312		839
313	# try to be perl5.6-compatible	840	# try to generate nice filehandles
314	local *AIO_FH;	841	my $sym = "IO::AIO::fd#$_[0]";
315	open AIO_FH, "+<&=$_[0]"	842	local *$sym;
		843
		844	open *$sym, "+<&=$_[0]" # usually works under any unix
		845	or open *$sym, "<&=$_[0]" # cygwin needs this
		846	or open *$sym, ">&=$_[0]" # or this
316	or return undef;	847	or return undef;
317		848
318	*AIO_FH	849	*$sym
319	}	850	}
320		851
321	min_parallel 4;	852	min_parallel 8;
322		853
323	END {	854	END {
324	max_parallel 0;	855	max_parallel 0;
325	}	856	}
326		857
327	1;	858	1;
328		859
		860	=head2 FORK BEHAVIOUR
		861
		862	This module should do "the right thing" when the process using it forks:
		863
		864	Before the fork, IO::AIO enters a quiescent state where no requests
		865	can be added in other threads and no results will be processed. After
		866	the fork the parent simply leaves the quiescent state and continues
		867	request/result processing, while the child clears the request/result
		868	queue (so the requests started before the fork will only be handled in
		869	the parent). Threads will be started on demand until the limit ste in the
		870	parent process has been reached again.
		871
		872	In short: the parent will, after a short pause, continue as if fork had
		873	not been called, while the child will act as if IO::AIO has not been used
		874	yet.
		875
		876	=head2 MEMORY USAGE
		877
		878	Each aio request uses - depending on your architecture - around 128 bytes
		879	of memory. In addition, stat requests need a stat buffer (possibly a few
		880	hundred bytes). Perl scalars and other data passed into aio requests will
		881	also be locked.
		882
		883	This is now awfully much, so queuing lots of requests is not usually a
		884	problem.
		885
		886	Each thread needs a stack area which is usually around 16k, sometimes much
		887	larger, depending on the OS.
		888
329	=head1 SEE ALSO	889	=head1 SEE ALSO
330		890
331	L<Coro>, L<Linux::AIO>.	891	L<Coro>, L<Linux::AIO> (obsolete).
332		892
333	=head1 AUTHOR	893	=head1 AUTHOR
334		894
335	Marc Lehmann <schmorp@schmorp.de>	895	Marc Lehmann <schmorp@schmorp.de>
336	http://home.schmorp.de/	896	http://home.schmorp.de/

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Revision 1.67 by root, Tue Oct 24 02:25:16 2006 UTC