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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.25 by root, Sun Jul 31 21:21:12 2005 UTC vs.
Revision 1.64 by root, Mon Oct 23 00:50:10 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 = 1.1;	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
		82	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
71	aio_fsync aio_fdatasync aio_readahead);	83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		84	aio_group aio_nop);
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 filenames you pass to these routines I<must> be absolute. The reason	111	The pathnames you pass to these routines I<must> be absolute and
94	for this is that at the time the request is being executed, the current	112	encoded in byte form. The reason for the former is that at the time the
95	working directory could have changed. Alternatively, you can make sure	113	request is being executed, the current working directory could have
96	that you never change the current working directory.	114	changed. Alternatively, you can make sure that you never change the
		115	current working directory.
		116
		117	To encode pathnames to byte form, either make sure you either: a)
		118	always pass in filenames you got from outside (command line, readdir
		119	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		120	your pathnames to the locale (or other) encoding in effect in the user
		121	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		122	use something else.
97		123
98	=over 4	124	=over 4
99		125
100	=item aio_open $pathname, $flags, $mode, $callback	126	=item aio_open $pathname, $flags, $mode, $callback->($fh)
101		127
102	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
103	created filehandle for the file.	129	created filehandle for the file.
104		130
105	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,
…		…
122	} else {	148	} else {
123	die "open failed: $!\n";	149	die "open failed: $!\n";
124	}	150	}
125	};	151	};
126		152
127	=item aio_close $fh, $callback	153	=item aio_close $fh, $callback->($status)
128		154
129	Asynchronously close a file and call the callback with the result	155	Asynchronously close a file and call the callback with the result
130	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
131	filehandle here, as perl will likely close the file descriptor another	157	filehandle here, as perl will likely close the file descriptor another
132	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
133	C<close> or just let filehandles go out of scope.	159	C<close> or just let filehandles go out of scope.
134		160
135	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
136	therefore best to avoid this function.	162	therefore best to avoid this function.
137		163
138	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
139		165
140	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
141		167
142	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>
143	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
144	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
145	like the syscall).	171	like the syscall).
146		172
		173	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		174	is outstanding. Modifying it can result in segfaults or WW3 (if the
		175	necessary/optional hardware is installed).
		176
147	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
148	offset C<0> within the scalar:	178	offset C<0> within the scalar:
149		179
150	aio_read $fh, 7, 15, $buffer, 0, sub {	180	aio_read $fh, 7, 15, $buffer, 0, sub {
151	$_[0] > 0 or die "read error: $!";	181	$_[0] > 0 or die "read error: $!";
152	print "read $_[0] bytes: <$buffer>\n";	182	print "read $_[0] bytes: <$buffer>\n";
153	};	183	};
154		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
155	=item aio_readahead $fh,$offset,$length, $callback	278	=item aio_readahead $fh,$offset,$length, $callback->($retval)
156
157	Asynchronously reads the specified byte range into the page cache, using
158	the C<readahead> syscall. If that syscall doesn't exist (likely if your OS
159	isn't Linux) the status will be C<-1> and C<$!> is set to C<ENOSYS>.
160		279
161	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
162	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>
163	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
164	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
165	whole pages, so that offset is effectively rounded down to a page boundary	284	whole pages, so that offset is effectively rounded down to a page boundary
166	and bytes are read up to the next page boundary greater than or equal to	285	and bytes are read up to the next page boundary greater than or equal to
167	(off-set+length). C<aio_readahead> does not read beyond the end of the	286	(off-set+length). C<aio_readahead> does not read beyond the end of the
168	file. The current file offset of the file is left unchanged.	287	file. The current file offset of the file is left unchanged.
169		288
		289	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		290	emulated by simply reading the data, which would have a similar effect.
		291
170	=item aio_stat $fh_or_path, $callback	292	=item aio_stat $fh_or_path, $callback->($status)
171		293
172	=item aio_lstat $fh, $callback	294	=item aio_lstat $fh, $callback->($status)
173		295
174	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
175	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 _>
176	or C<-s _> etc...	298	or C<-s _> etc...
177		299
…		…
187	aio_stat "/etc/passwd", sub {	309	aio_stat "/etc/passwd", sub {
188	$_[0] and die "stat failed: $!";	310	$_[0] and die "stat failed: $!";
189	print "size is ", -s _, "\n";	311	print "size is ", -s _, "\n";
190	};	312	};
191		313
192	=item aio_unlink $pathname, $callback	314	=item aio_unlink $pathname, $callback->($status)
193		315
194	Asynchronously unlink (delete) a file and call the callback with the	316	Asynchronously unlink (delete) a file and call the callback with the
195	result code.	317	result code.
196		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
		334	=item aio_rmdir $pathname, $callback->($status)
		335
		336	Asynchronously rmdir (delete) a directory and call the callback with the
		337	result code.
		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
197	=item aio_fsync $fh, $callback	503	=item aio_fsync $fh, $callback->($status)
198		504
199	Asynchronously call fsync on the given filehandle and call the callback	505	Asynchronously call fsync on the given filehandle and call the callback
200	with the fsync result code.	506	with the fsync result code.
201		507
202	=item aio_fdatasync $fh, $callback	508	=item aio_fdatasync $fh, $callback->($status)
203		509
204	Asynchronously call fdatasync on the given filehandle and call the	510	Asynchronously call fdatasync on the given filehandle and call the
205	callback with the fdatasync result code. Might set C<$!> to C<ENOSYS> if	511	callback with the fdatasync result code.
206	C<fdatasync> is not available.	512
		513	If this call isn't available because your OS lacks it or it couldn't be
		514	detected, it will be emulated by calling C<fsync> instead.
		515
		516	=item aio_group $callback->(...)
		517
		518	[EXPERIMENTAL]
		519
		520	This is a very special aio request: Instead of doing something, it is a
		521	container for other aio requests, which is useful if you want to bundle
		522	many requests into a single, composite, request.
		523
		524	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		525	for more info.
		526
		527	Example:
		528
		529	my $grp = aio_group sub {
		530	print "all stats done\n";
		531	};
		532
		533	add $grp
		534	(aio_stat ...),
		535	(aio_stat ...),
		536	...;
		537
		538	=item aio_nop $callback->()
		539
		540	This is a special request - it does nothing in itself and is only used for
		541	side effects, such as when you want to add a dummy request to a group so
		542	that finishing the requests in the group depends on executing the given
		543	code.
		544
		545	While this request does nothing, it still goes through the execution
		546	phase and still requires a worker thread. Thus, the callback will not
		547	be executed immediately but only after other requests in the queue have
		548	entered their execution phase. This can be used to measure request
		549	latency.
		550
		551	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		552
		553	Mainly used for debugging and benchmarking, this aio request puts one of
		554	the request workers to sleep for the given time.
		555
		556	While it is theoretically handy to have simple I/O scheduling requests
		557	like sleep and file handle readable/writable, the overhead this creates
		558	is immense, so do not use this function except to put your application
		559	under artificial I/O pressure.
		560
		561	=back
		562
		563	=head2 IO::AIO::REQ CLASS
		564
		565	All non-aggregate C<aio_*> functions return an object of this class when
		566	called in non-void context.
		567
		568	A request always moves through the following five states in its lifetime,
		569	in order: B<ready> (request has been created, but has not been executed
		570	yet), B<execute> (request is currently being executed), B<pending>
		571	(request has been executed but callback has not been called yet),
		572	B<result> (results are being processed synchronously, includes calling the
		573	callback) and B<done> (request has reached the end of its lifetime and
		574	holds no resources anymore).
		575
		576	=over 4
		577
		578	=item $req->cancel
		579
		580	Cancels the request, if possible. Has the effect of skipping execution
		581	when entering the B<execute> state and skipping calling the callback when
		582	entering the the B<result> state, but will leave the request otherwise
		583	untouched. That means that requests that currently execute will not be
		584	stopped and resources held by the request will not be freed prematurely.
		585
		586	=back
		587
		588	=head2 IO::AIO::GRP CLASS
		589
		590	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		591	objects of this class, too.
		592
		593	A IO::AIO::GRP object is a special request that can contain multiple other
		594	aio requests.
		595
		596	You create one by calling the C<aio_group> constructing function with a
		597	callback that will be called when all contained requests have entered the
		598	C<done> state:
		599
		600	my $grp = aio_group sub {
		601	print "all requests are done\n";
		602	};
		603
		604	You add requests by calling the C<add> method with one or more
		605	C<IO::AIO::REQ> objects:
		606
		607	$grp->add (aio_unlink "...");
		608
		609	add $grp aio_stat "...", sub {
		610	$_[0] or return $grp->result ("error");
		611
		612	# add another request dynamically, if first succeeded
		613	add $grp aio_open "...", sub {
		614	$grp->result ("ok");
		615	};
		616	};
		617
		618	This makes it very easy to create composite requests (see the source of
		619	C<aio_move> for an application) that work and feel like simple requests.
		620
		621	=over 4
		622
		623	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		624	C<IO::AIO::poll_cb>, just like any other request.
		625
		626	=item * They can be canceled like any other request. Canceling will cancel not
		627	only the request itself, but also all requests it contains.
		628
		629	=item * They can also can also be added to other IO::AIO::GRP objects.
		630
		631	=item * You must not add requests to a group from within the group callback (or
		632	any later time).
		633
		634	=item * This does not harmonise well with C<max_outstanding>, so best do
		635	not combine C<aio_group> with it. Groups and feeders are recommended for
		636	this kind of concurrency-limiting.
		637
		638	=back
		639
		640	Their lifetime, simplified, looks like this: when they are empty, they
		641	will finish very quickly. If they contain only requests that are in the
		642	C<done> state, they will also finish. Otherwise they will continue to
		643	exist.
		644
		645	That means after creating a group you have some time to add requests. And
		646	in the callbacks of those requests, you can add further requests to the
		647	group. And only when all those requests have finished will the the group
		648	itself finish.
		649
		650	=over 4
		651
		652	=item $grp->add (...)
		653
		654	=item add $grp ...
		655
		656	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		657	be added, including other groups, as long as you do not create circular
		658	dependencies.
		659
		660	Returns all its arguments.
		661
		662	=item $grp->result (...)
		663
		664	Set the result value(s) that will be passed to the group callback when all
		665	subrequests have finished. By default, no argument will be passed.
		666
		667	=item $grp->set_feeder ($callback->($grp))
		668
		669	[VERY EXPERIMENTAL]
		670
		671	Sets a feeder/generator on this group: every group can have an attached
		672	generator that generates requests if idle. The idea behind this is that,
		673	although you could just queue as many requests as you want in a group,
		674	this might starve other requests for a potentially long time. For
		675	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		676	requests, delaying any later requests for a long time.
		677
		678	To avoid this, and allow incremental generation of requests, you can
		679	instead a group and set a feeder on it that generates those requests. The
		680	feeder will be called whenever there are few enough (see C<feeder_limit>,
		681	below) requests active in the group itself and is expected to queue more
		682	requests.
		683
		684	The feeder can queue as many requests as it likes (i.e. C<add> does not
		685	impose any limits).
		686
		687	If the feeder does not queue more requests when called, it will be
		688	automatically removed from the group.
		689
		690	If the feeder limit is C<0>, it will be set to C<2> automatically.
		691
		692	Example:
		693
		694	# stat all files in @files, but only ever use four aio requests concurrently:
		695
		696	my $grp = aio_group sub { print "finished\n" };
		697	$grp->feeder_limit (4);
		698	$grp->set_feeder (sub {
		699	my $file = pop @files
		700	or return;
		701
		702	add $grp aio_stat $file, sub { ... };
		703	});
		704
		705	=item $grp->feeder_limit ($num)
		706
		707	Sets the feeder limit for the group: The feeder will be called whenever
		708	the group contains less than this many requests.
		709
		710	Setting the limit to C<0> will pause the feeding process.
207		711
208	=back	712	=back
209		713
210	=head2 SUPPORT FUNCTIONS	714	=head2 SUPPORT FUNCTIONS
211		715
…		…
269	IO::AIO::poll_wait, IO::AIO::poll_cb	773	IO::AIO::poll_wait, IO::AIO::poll_cb
270	if IO::AIO::nreqs;	774	if IO::AIO::nreqs;
271		775
272	=item IO::AIO::min_parallel $nthreads	776	=item IO::AIO::min_parallel $nthreads
273		777
274	Set the minimum number of AIO threads to C<$nthreads>. The default is	778	Set the minimum number of AIO threads to C<$nthreads>. The current
275	C<1>, which means a single asynchronous operation can be done at one time	779	default is C<8>, which means eight asynchronous operations can execute
276	(the number of outstanding operations, however, is unlimited).	780	concurrently at any one time (the number of outstanding requests,
		781	however, is unlimited).
277		782
		783	IO::AIO starts threads only on demand, when an AIO request is queued and
		784	no free thread exists.
		785
278	It is recommended to keep the number of threads low, as some Linux	786	It is recommended to keep the number of threads relatively low, as some
279	kernel versions will scale negatively with the number of threads (higher	787	Linux kernel versions will scale negatively with the number of threads
280	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	788	(higher parallelity => MUCH higher latency). With current Linux 2.6
281	threads should be fine.	789	versions, 4-32 threads should be fine.
282		790
283	Under normal circumstances you don't need to call this function, as this	791	Under most circumstances you don't need to call this function, as the
284	module automatically starts some threads (the exact number might change,	792	module selects a default that is suitable for low to moderate load.
285	and is currently 4).
286		793
287	=item IO::AIO::max_parallel $nthreads	794	=item IO::AIO::max_parallel $nthreads
288		795
289	Sets the maximum number of AIO threads to C<$nthreads>. If more than	796	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
290	the specified number of threads are currently running, kill them. This	797	specified number of threads are currently running, this function kills
291	function blocks until the limit is reached.	798	them. This function blocks until the limit is reached.
		799
		800	While C<$nthreads> are zero, aio requests get queued but not executed
		801	until the number of threads has been increased again.
292		802
293	This module automatically runs C<max_parallel 0> at program end, to ensure	803	This module automatically runs C<max_parallel 0> at program end, to ensure
294	that all threads are killed and that there are no outstanding requests.	804	that all threads are killed and that there are no outstanding requests.
295		805
296	Under normal circumstances you don't need to call this function.	806	Under normal circumstances you don't need to call this function.
297		807
298	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	808	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		809
		810	[DEPRECATED]
299		811
300	Sets the maximum number of outstanding requests to C<$nreqs>. If you	812	Sets the maximum number of outstanding requests to C<$nreqs>. If you
301	try to queue up more than this number of requests, the caller will block until	813	try to queue up more than this number of requests, the caller will block until
302	some requests have been handled.	814	some requests have been handled.
303		815
304	The default is very large, so normally there is no practical limit. If you	816	The default is very large, so normally there is no practical limit. If you
305	queue up many requests in a loop it it often improves speed if you set	817	queue up many requests in a loop it often improves speed if you set
306	this to a relatively low number, such as C<100>.	818	this to a relatively low number, such as C<100>.
		819
		820	This function does not work well together with C<aio_group>'s, and their
		821	feeder interface is better suited to limiting concurrency, so do not use
		822	this function.
307		823
308	Under normal circumstances you don't need to call this function.	824	Under normal circumstances you don't need to call this function.
309		825
310	=back	826	=back
311		827
…		…
317		833
318	# try to generate nice filehandles	834	# try to generate nice filehandles
319	my $sym = "IO::AIO::fd#$_[0]";	835	my $sym = "IO::AIO::fd#$_[0]";
320	local *$sym;	836	local *$sym;
321		837
322	open *$sym, "+<&$_[0]" # usually under any unix	838	open *$sym, "+<&=$_[0]" # usually works under any unix
323	or open *$sym, "<&$_[0]" # cygwin needs this	839	or open *$sym, "<&=$_[0]" # cygwin needs this
324	or open *$sym, ">&$_[0]" # cygwin needs this	840	or open *$sym, ">&=$_[0]" # or this
325	or return undef;	841	or return undef;
326		842
327	*$sym	843	*$sym
328	}	844	}
329		845
330	min_parallel 4;	846	min_parallel 8;
331		847
332	END {	848	END {
333	max_parallel 0;	849	max_parallel 0;
334	}	850	}
335		851
336	1;	852	1;
337		853
		854	=head2 FORK BEHAVIOUR
		855
		856	This module should do "the right thing" when the process using it forks:
		857
		858	Before the fork, IO::AIO enters a quiescent state where no requests
		859	can be added in other threads and no results will be processed. After
		860	the fork the parent simply leaves the quiescent state and continues
		861	request/result processing, while the child clears the request/result
		862	queue (so the requests started before the fork will only be handled in
		863	the parent). Threads will be started on demand until the limit ste in the
		864	parent process has been reached again.
		865
		866	In short: the parent will, after a short pause, continue as if fork had
		867	not been called, while the child will act as if IO::AIO has not been used
		868	yet.
		869
		870	=head2 MEMORY USAGE
		871
		872	Each aio request uses - depending on your architecture - around 128 bytes
		873	of memory. In addition, stat requests need a stat buffer (possibly a few
		874	hundred bytes). Perl scalars and other data passed into aio requests will
		875	also be locked.
		876
		877	This is now awfully much, so queuing lots of requests is not usually a
		878	problem.
		879
		880	Each thread needs a stack area which is usually around 16k, sometimes much
		881	larger, depending on the OS.
		882
338	=head1 SEE ALSO	883	=head1 SEE ALSO
339		884
340	L<Coro>, L<Linux::AIO>.	885	L<Coro>, L<Linux::AIO> (obsolete).
341		886
342	=head1 AUTHOR	887	=head1 AUTHOR
343		888
344	Marc Lehmann <schmorp@schmorp.de>	889	Marc Lehmann <schmorp@schmorp.de>
345	http://home.schmorp.de/	890	http://home.schmorp.de/

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Revision 1.64 by root, Mon Oct 23 00:50:10 2006 UTC