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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.29 by root, Wed Aug 17 04:47:02 2005 UTC vs.
Revision 1.62 by root, Sun Oct 22 21:13:47 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
37		49
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.
…		…
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 = 1.2;	79	our $VERSION = '2.0';
69		80
70	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	81	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71	aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead);	82	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
		83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		84	aio_group);
72	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
		86
		87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
73		88
74	require XSLoader;	89	require XSLoader;
75	XSLoader::load IO::AIO, $VERSION;	90	XSLoader::load ("IO::AIO", $VERSION);
76	}	91	}
77		92
78	=head1 FUNCTIONS	93	=head1 FUNCTIONS
79		94
80	=head2 AIO FUNCTIONS	95	=head2 AIO FUNCTIONS
…		…
88	syscall has been executed asynchronously.	103	syscall has been executed asynchronously.
89		104
90	All functions expecting a filehandle keep a copy of the filehandle	105	All functions expecting a filehandle keep a copy of the filehandle
91	internally until the request has finished.	106	internally until the request has finished.
92		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
93	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
94	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
95	request is being executed, the current working directory could have	113	request is being executed, the current working directory could have
96	changed. Alternatively, you can make sure that you never change the	114	changed. Alternatively, you can make sure that you never change the
97	current working directory.	115	current working directory.
…		…
103	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)
104	use something else.	122	use something else.
105		123
106	=over 4	124	=over 4
107		125
108	=item aio_open $pathname, $flags, $mode, $callback	126	=item aio_open $pathname, $flags, $mode, $callback->($fh)
109		127
110	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
111	created filehandle for the file.	129	created filehandle for the file.
112		130
113	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,
…		…
130	} else {	148	} else {
131	die "open failed: $!\n";	149	die "open failed: $!\n";
132	}	150	}
133	};	151	};
134		152
135	=item aio_close $fh, $callback	153	=item aio_close $fh, $callback->($status)
136		154
137	Asynchronously close a file and call the callback with the result	155	Asynchronously close a file and call the callback with the result
138	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
139	filehandle here, as perl will likely close the file descriptor another	157	filehandle here, as perl will likely close the file descriptor another
140	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
141	C<close> or just let filehandles go out of scope.	159	C<close> or just let filehandles go out of scope.
142		160
143	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
144	therefore best to avoid this function.	162	therefore best to avoid this function.
145		163
146	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
147		165
148	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149		167
150	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>
151	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
152	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
153	like the syscall).	171	like the syscall).
154		172
		173	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		174	is outstanding. Modifying it can result in segfaults or WW3 (if the
		175	necessary/optional hardware is installed).
		176
155	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
156	offset C<0> within the scalar:	178	offset C<0> within the scalar:
157		179
158	aio_read $fh, 7, 15, $buffer, 0, sub {	180	aio_read $fh, 7, 15, $buffer, 0, sub {
159	$_[0] > 0 or die "read error: $!";	181	$_[0] > 0 or die "read error: $!";
160	print "read $_[0] bytes: <$buffer>\n";	182	print "read $_[0] bytes: <$buffer>\n";
161	};	183	};
162		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
		255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		256
		257	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		258	reading at byte offset C<$in_offset>, and starts writing at the current
		259	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		260	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		261	other.
		262
		263	This call tries to make use of a native C<sendfile> syscall to provide
		264	zero-copy operation. For this to work, C<$out_fh> should refer to a
		265	socket, and C<$in_fh> should refer to mmap'able file.
		266
		267	If the native sendfile call fails or is not implemented, it will be
		268	emulated, so you can call C<aio_sendfile> on any type of filehandle
		269	regardless of the limitations of the operating system.
		270
		271	Please note, however, that C<aio_sendfile> can read more bytes from
		272	C<$in_fh> than are written, and there is no way to find out how many
		273	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		274	provides the number of bytes written to C<$out_fh>. Only if the result
		275	value equals C<$length> one can assume that C<$length> bytes have been
		276	read.
		277
163	=item aio_readahead $fh,$offset,$length, $callback	278	=item aio_readahead $fh,$offset,$length, $callback->($retval)
164		279
165	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
166	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>
167	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
168	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
…		…
172	file. The current file offset of the file is left unchanged.	287	file. The current file offset of the file is left unchanged.
173		288
174	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
175	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.
176		291
177	=item aio_stat $fh_or_path, $callback	292	=item aio_stat $fh_or_path, $callback->($status)
178		293
179	=item aio_lstat $fh, $callback	294	=item aio_lstat $fh, $callback->($status)
180		295
181	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
182	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 _>
183	or C<-s _> etc...	298	or C<-s _> etc...
184		299
…		…
194	aio_stat "/etc/passwd", sub {	309	aio_stat "/etc/passwd", sub {
195	$_[0] and die "stat failed: $!";	310	$_[0] and die "stat failed: $!";
196	print "size is ", -s _, "\n";	311	print "size is ", -s _, "\n";
197	};	312	};
198		313
199	=item aio_unlink $pathname, $callback	314	=item aio_unlink $pathname, $callback->($status)
200		315
201	Asynchronously unlink (delete) a file and call the callback with the	316	Asynchronously unlink (delete) a file and call the callback with the
202	result code.	317	result code.
203		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
204	=item aio_rmdir $pathname, $callback	334	=item aio_rmdir $pathname, $callback->($status)
205		335
206	Asynchronously rmdir (delete) a directory and call the callback with the	336	Asynchronously rmdir (delete) a directory and call the callback with the
207	result code.	337	result code.
208		338
		339	=item aio_readdir $pathname, $callback->($entries)
		340
		341	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		342	directory (i.e. opendir + readdir + closedir). The entries will not be
		343	sorted, and will B<NOT> include the C<.> and C<..> entries.
		344
		345	The callback a single argument which is either C<undef> or an array-ref
		346	with the filenames.
		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
209	=item aio_fsync $fh, $callback	503	=item aio_fsync $fh, $callback->($status)
210		504
211	Asynchronously call fsync on the given filehandle and call the callback	505	Asynchronously call fsync on the given filehandle and call the callback
212	with the fsync result code.	506	with the fsync result code.
213		507
214	=item aio_fdatasync $fh, $callback	508	=item aio_fdatasync $fh, $callback->($status)
215		509
216	Asynchronously call fdatasync on the given filehandle and call the	510	Asynchronously call fdatasync on the given filehandle and call the
217	callback with the fdatasync result code.	511	callback with the fdatasync result code.
218		512
219	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
220	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 IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		539
		540	Mainly used for debugging and benchmarking, this aio request puts one of
		541	the request workers to sleep for the given time.
		542
		543	While it is theoretically handy to have simple I/O scheduling requests
		544	like sleep and file handle readable/writable, the overhead this creates
		545	is immense, so do not use this function except to put your application
		546	under artificial I/O pressure.
		547
		548	=back
		549
		550	=head2 IO::AIO::REQ CLASS
		551
		552	All non-aggregate C<aio_*> functions return an object of this class when
		553	called in non-void context.
		554
		555	A request always moves through the following five states in its lifetime,
		556	in order: B<ready> (request has been created, but has not been executed
		557	yet), B<execute> (request is currently being executed), B<pending>
		558	(request has been executed but callback has not been called yet),
		559	B<result> (results are being processed synchronously, includes calling the
		560	callback) and B<done> (request has reached the end of its lifetime and
		561	holds no resources anymore).
		562
		563	=over 4
		564
		565	=item $req->cancel
		566
		567	Cancels the request, if possible. Has the effect of skipping execution
		568	when entering the B<execute> state and skipping calling the callback when
		569	entering the the B<result> state, but will leave the request otherwise
		570	untouched. That means that requests that currently execute will not be
		571	stopped and resources held by the request will not be freed prematurely.
		572
		573	=back
		574
		575	=head2 IO::AIO::GRP CLASS
		576
		577	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		578	objects of this class, too.
		579
		580	A IO::AIO::GRP object is a special request that can contain multiple other
		581	aio requests.
		582
		583	You create one by calling the C<aio_group> constructing function with a
		584	callback that will be called when all contained requests have entered the
		585	C<done> state:
		586
		587	my $grp = aio_group sub {
		588	print "all requests are done\n";
		589	};
		590
		591	You add requests by calling the C<add> method with one or more
		592	C<IO::AIO::REQ> objects:
		593
		594	$grp->add (aio_unlink "...");
		595
		596	add $grp aio_stat "...", sub {
		597	$_[0] or return $grp->result ("error");
		598
		599	# add another request dynamically, if first succeeded
		600	add $grp aio_open "...", sub {
		601	$grp->result ("ok");
		602	};
		603	};
		604
		605	This makes it very easy to create composite requests (see the source of
		606	C<aio_move> for an application) that work and feel like simple requests.
		607
		608	=over 4
		609
		610	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		611	C<IO::AIO::poll_cb>, just like any other request.
		612
		613	=item * They can be canceled like any other request. Canceling will cancel not
		614	only the request itself, but also all requests it contains.
		615
		616	=item * They can also can also be added to other IO::AIO::GRP objects.
		617
		618	=item * You must not add requests to a group from within the group callback (or
		619	any later time).
		620
		621	=item * This does not harmonise well with C<max_outstanding>, so best do
		622	not combine C<aio_group> with it. Groups and feeders are recommended for
		623	this kind of concurrency-limiting.
		624
		625	=back
		626
		627	Their lifetime, simplified, looks like this: when they are empty, they
		628	will finish very quickly. If they contain only requests that are in the
		629	C<done> state, they will also finish. Otherwise they will continue to
		630	exist.
		631
		632	That means after creating a group you have some time to add requests. And
		633	in the callbacks of those requests, you can add further requests to the
		634	group. And only when all those requests have finished will the the group
		635	itself finish.
		636
		637	=over 4
		638
		639	=item $grp->add (...)
		640
		641	=item add $grp ...
		642
		643	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		644	be added, including other groups, as long as you do not create circular
		645	dependencies.
		646
		647	Returns all its arguments.
		648
		649	=item $grp->result (...)
		650
		651	Set the result value(s) that will be passed to the group callback when all
		652	subrequests have finished. By default, no argument will be passed.
		653
		654	=item $grp->set_feeder ($callback->($grp))
		655
		656	[VERY EXPERIMENTAL]
		657
		658	Sets a feeder/generator on this group: every group can have an attached
		659	generator that generates requests if idle. The idea behind this is that,
		660	although you could just queue as many requests as you want in a group,
		661	this might starve other requests for a potentially long time. For
		662	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		663	requests, delaying any later requests for a long time.
		664
		665	To avoid this, and allow incremental generation of requests, you can
		666	instead a group and set a feeder on it that generates those requests. The
		667	feeder will be called whenever there are few enough (see C<feeder_limit>,
		668	below) requests active in the group itself and is expected to queue more
		669	requests.
		670
		671	The feeder can queue as many requests as it likes (i.e. C<add> does not
		672	impose any limits).
		673
		674	If the feeder does not queue more requests when called, it will be
		675	automatically removed from the group.
		676
		677	If the feeder limit is C<0>, it will be set to C<2> automatically.
		678
		679	Example:
		680
		681	# stat all files in @files, but only ever use four aio requests concurrently:
		682
		683	my $grp = aio_group sub { print "finished\n" };
		684	$grp->feeder_limit (4);
		685	$grp->set_feeder (sub {
		686	my $file = pop @files
		687	or return;
		688
		689	add $grp aio_stat $file, sub { ... };
		690	});
		691
		692	=item $grp->feeder_limit ($num)
		693
		694	Sets the feeder limit for the group: The feeder will be called whenever
		695	the group contains less than this many requests.
		696
		697	Setting the limit to C<0> will pause the feeding process.
221		698
222	=back	699	=back
223		700
224	=head2 SUPPORT FUNCTIONS	701	=head2 SUPPORT FUNCTIONS
225		702
…		…
283	IO::AIO::poll_wait, IO::AIO::poll_cb	760	IO::AIO::poll_wait, IO::AIO::poll_cb
284	if IO::AIO::nreqs;	761	if IO::AIO::nreqs;
285		762
286	=item IO::AIO::min_parallel $nthreads	763	=item IO::AIO::min_parallel $nthreads
287		764
288	Set the minimum number of AIO threads to C<$nthreads>. The default is	765	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	766	default is C<8>, which means eight asynchronous operations can execute
290	(the number of outstanding operations, however, is unlimited).	767	concurrently at any one time (the number of outstanding requests,
		768	however, is unlimited).
291		769
		770	IO::AIO starts threads only on demand, when an AIO request is queued and
		771	no free thread exists.
		772
292	It is recommended to keep the number of threads low, as some Linux	773	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	774	Linux kernel versions will scale negatively with the number of threads
294	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	775	(higher parallelity => MUCH higher latency). With current Linux 2.6
295	threads should be fine.	776	versions, 4-32 threads should be fine.
296		777
297	Under normal circumstances you don't need to call this function, as this	778	Under most circumstances you don't need to call this function, as the
298	module automatically starts some threads (the exact number might change,	779	module selects a default that is suitable for low to moderate load.
299	and is currently 4).
300		780
301	=item IO::AIO::max_parallel $nthreads	781	=item IO::AIO::max_parallel $nthreads
302		782
303	Sets the maximum number of AIO threads to C<$nthreads>. If more than	783	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
304	the specified number of threads are currently running, kill them. This	784	specified number of threads are currently running, this function kills
305	function blocks until the limit is reached.	785	them. This function blocks until the limit is reached.
		786
		787	While C<$nthreads> are zero, aio requests get queued but not executed
		788	until the number of threads has been increased again.
306		789
307	This module automatically runs C<max_parallel 0> at program end, to ensure	790	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.	791	that all threads are killed and that there are no outstanding requests.
309		792
310	Under normal circumstances you don't need to call this function.	793	Under normal circumstances you don't need to call this function.
311		794
312	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	795	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		796
		797	[DEPRECATED]
313		798
314	Sets the maximum number of outstanding requests to C<$nreqs>. If you	799	Sets the maximum number of outstanding requests to C<$nreqs>. If you
315	try to queue up more than this number of requests, the caller will block until	800	try to queue up more than this number of requests, the caller will block until
316	some requests have been handled.	801	some requests have been handled.
317		802
318	The default is very large, so normally there is no practical limit. If you	803	The default is very large, so normally there is no practical limit. If you
319	queue up many requests in a loop it it often improves speed if you set	804	queue up many requests in a loop it often improves speed if you set
320	this to a relatively low number, such as C<100>.	805	this to a relatively low number, such as C<100>.
		806
		807	This function does not work well together with C<aio_group>'s, and their
		808	feeder interface is better suited to limiting concurrency, so do not use
		809	this function.
321		810
322	Under normal circumstances you don't need to call this function.	811	Under normal circumstances you don't need to call this function.
323		812
324	=back	813	=back
325		814
…		…
339	or return undef;	828	or return undef;
340		829
341	*$sym	830	*$sym
342	}	831	}
343		832
344	min_parallel 4;	833	min_parallel 8;
345		834
346	END {	835	END {
347	max_parallel 0;	836	max_parallel 0;
348	}	837	}
349		838
350	1;	839	1;
351		840
352	=head2 FORK BEHAVIOUR	841	=head2 FORK BEHAVIOUR
353		842
354	Before the fork IO::AIO first handles all outstanding requests - if other	843	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	844
356	enters a quiescent state where no requests can be added in other threads	845	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	846	can be added in other threads and no results will be processed. After
358	the quiescent state and continues request processing, while the child will	847	the fork the parent simply leaves the quiescent state and continues
359	free the request and result queue and start the same number of threads as	848	request/result processing, while the child clears the request/result
360	were in use by the parent.	849	queue (so the requests started before the fork will only be handled in
		850	the parent). Threads will be started on demand until the limit ste in the
		851	parent process has been reached again.
		852
		853	In short: the parent will, after a short pause, continue as if fork had
		854	not been called, while the child will act as if IO::AIO has not been used
		855	yet.
		856
		857	=head2 MEMORY USAGE
		858
		859	Each aio request uses - depending on your architecture - around 128 bytes
		860	of memory. In addition, stat requests need a stat buffer (possibly a few
		861	hundred bytes). Perl scalars and other data passed into aio requests will
		862	also be locked.
		863
		864	This is now awfully much, so queuing lots of requests is not usually a
		865	problem.
		866
		867	Each thread needs a stack area which is usually around 16k, sometimes much
		868	larger, depending on the OS.
361		869
362	=head1 SEE ALSO	870	=head1 SEE ALSO
363		871
364	L<Coro>, L<Linux::AIO>.	872	L<Coro>, L<Linux::AIO> (obsolete).
365		873
366	=head1 AUTHOR	874	=head1 AUTHOR
367		875
368	Marc Lehmann <schmorp@schmorp.de>	876	Marc Lehmann <schmorp@schmorp.de>
369	http://home.schmorp.de/	877	http://home.schmorp.de/

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Revision 1.62 by root, Sun Oct 22 21:13:47 2006 UTC