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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.1 by root, Sun Jul 10 17:07:44 2005 UTC vs.
Revision 1.54 by root, Sun Oct 22 00:19:05 2006 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
		9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		10	my ($fh) = @_;
		11	...
		12	};
		13
		14	aio_unlink "/tmp/file", sub { };
		15
		16	aio_read $fh, 30000, 1024, $buffer, 0, sub {
		17	$_[0] > 0 or die "read error: $!";
		18	};
		19
		20	use IO::AIO 2; # version has aio objects
		21
		22	my $req = aio_unlink "/tmp/file", sub { };
		23	$req->cancel; # cancel request if still in queue
		24
		25	# AnyEvent
		26	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		27	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		28
		29	# Event
		30	Event->io (fd => IO::AIO::poll_fileno,
		31	poll => 'r',
		32	cb => \&IO::AIO::poll_cb);
		33
		34	# Glib/Gtk2
		35	add_watch Glib::IO IO::AIO::poll_fileno,
		36	in => sub { IO::AIO::poll_cb; 1 };
		37
		38	# Tk
		39	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		40	readable => \&IO::AIO::poll_cb);
		41
		42	# Danga::Socket
		43	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		44	\&IO::AIO::poll_cb);
		45
		46
9	=head1 DESCRIPTION	47	=head1 DESCRIPTION
10		48
11	This module implements asynchronous I/O using whatever means your	49	This module implements asynchronous I/O using whatever means your
12	operating system supports. Currently, it falls back to Linux::AIO if that	50	operating system supports.
13	module is available, or uses pthreads to emulato aio functionality.
14		51
15	Currently, in this module a number of threads are started that execute	52	Currently, a number of threads are started that execute your read/writes
16	your read/writes and signal their completion. You don't need thread	53	and signal their completion. You don't need thread support in your libc or
17	support in your libc or perl, and the threads created by this module will	54	perl, and the threads created by this module will not be visible to the
18	not be visible to the pthreads library.	55	pthreads library. In the future, this module might make use of the native
		56	aio functions available on many operating systems. However, they are often
		57	not well-supported (Linux doesn't allow them on normal files currently,
		58	for example), and they would only support aio_read and aio_write, so the
		59	remaining functionality would have to be implemented using threads anyway.
19		60
20	Although the module will work with in the presence of other threads, it is	61	Although the module will work with in the presence of other threads, it is
21	not reentrant, so use appropriate locking yourself.	62	currently not reentrant, so use appropriate locking yourself, always call
		63	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other
		64	C<aio_> functions) recursively.
22		65
23	=head2 API NOTES	66	=cut
		67
		68	package IO::AIO;
		69
		70	no warnings;
		71	use strict 'vars';
		72
		73	use base 'Exporter';
		74
		75	BEGIN {
		76	our $VERSION = '1.99';
		77
		78	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
		79	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
		80	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		81	aio_group);
		82	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
		83
		84	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
		85
		86	require XSLoader;
		87	XSLoader::load ("IO::AIO", $VERSION);
		88	}
		89
		90	=head1 FUNCTIONS
		91
		92	=head2 AIO FUNCTIONS
24		93
25	All the C<aio_*> calls are more or less thin wrappers around the syscall	94	All the C<aio_*> calls are more or less thin wrappers around the syscall
26	with the same name (sans C<aio_>). The arguments are similar or identical,	95	with the same name (sans C<aio_>). The arguments are similar or identical,
27	and they all accept an additional C<$callback> argument which must be	96	and they all accept an additional (and optional) C<$callback> argument
28	a code reference. This code reference will get called with the syscall	97	which must be a code reference. This code reference will get called with
29	return code (e.g. most syscalls return C<-1> on error, unlike perl, which	98	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
30	usually delivers "false") as it's sole argument when the given syscall has	99	perl, which usually delivers "false") as it's sole argument when the given
31	been executed asynchronously.	100	syscall has been executed asynchronously.
32		101
33	All functions that expect a filehandle will also accept a file descriptor.	102	All functions expecting a filehandle keep a copy of the filehandle
		103	internally until the request has finished.
34		104
		105	All non-composite requests (requests that are not broken down into
		106	multiple requests) return objects of type L<IO::AIO::REQ> that allow
		107	further manipulation of running requests.
		108
35	The filenames you pass to these routines I<must> be absolute. The reason	109	The pathnames you pass to these routines I<must> be absolute and
36	is that at the time the request is being executed, the current working	110	encoded in byte form. The reason for the former is that at the time the
37	directory could have changed. Alternatively, you can make sure that you	111	request is being executed, the current working directory could have
		112	changed. Alternatively, you can make sure that you never change the
38	never change the current working directory.	113	current working directory.
		114
		115	To encode pathnames to byte form, either make sure you either: a)
		116	always pass in filenames you got from outside (command line, readdir
		117	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		118	your pathnames to the locale (or other) encoding in effect in the user
		119	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		120	use something else.
39		121
40	=over 4	122	=over 4
41		123
42	=cut
43
44	package IO::AIO;
45
46	use base 'Exporter';
47
48	BEGIN {
49	$VERSION = 0.1;
50
51	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink
52	aio_fsync aio_fdatasync aio_readahead);
53	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs);
54
55	require XSLoader;
56	XSLoader::load IO::AIO, $VERSION;
57	}
58
59	=item IO::AIO::min_parallel $nthreads
60
61	Set the minimum number of AIO threads to C<$nthreads>. The default is
62	C<1>, which means a single asynchronous operation can be done at one time
63	(the number of outstanding operations, however, is unlimited).
64
65	It is recommended to keep the number of threads low, as some linux
66	kernel versions will scale negatively with the number of threads (higher
67	parallelity => MUCH higher latency).
68
69	Under normal circumstances you don't need to call this function, as this
70	module automatically starts a single async thread.
71
72	=item IO::AIO::max_parallel $nthreads
73
74	Sets the maximum number of AIO threads to C<$nthreads>. If more than
75	the specified number of threads are currently running, kill them. This
76	function blocks until the limit is reached.
77
78	This module automatically runs C<max_parallel 0> at program end, to ensure
79	that all threads are killed and that there are no outstanding requests.
80
81	Under normal circumstances you don't need to call this function.
82
83	=item $fileno = IO::AIO::poll_fileno
84
85	Return the I<request result pipe filehandle>. This filehandle must be
86	polled for reading by some mechanism outside this module (e.g. Event
87	or select, see below). If the pipe becomes readable you have to call
88	C<poll_cb> to check the results.
89
90	See C<poll_cb> for an example.
91
92	=item IO::AIO::poll_cb
93
94	Process all outstanding events on the result pipe. You have to call this
95	regularly. Returns the number of events processed. Returns immediately
96	when no events are outstanding.
97
98	You can use Event to multiplex, e.g.:
99
100	Event->io (fd => IO::AIO::poll_fileno,
101	poll => 'r', async => 1,
102	cb => \&IO::AIO::poll_cb);
103
104	=item IO::AIO::poll_wait
105
106	Wait till the result filehandle becomes ready for reading (simply does a
107	select on the filehandle. This is useful if you want to synchronously wait
108	for some requests to finish).
109
110	See C<nreqs> for an example.
111
112	=item IO::AIO::nreqs
113
114	Returns the number of requests currently outstanding.
115
116	Example: wait till there are no outstanding requests anymore:
117
118	IO::AIO::poll_wait, IO::AIO::poll_cb
119	while IO::AIO::nreqs;
120
121	=item aio_open $pathname, $flags, $mode, $callback	124	=item aio_open $pathname, $flags, $mode, $callback->($fh)
122		125
123	Asynchronously open or create a file and call the callback with the	126	Asynchronously open or create a file and call the callback with a newly
124	filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this	127	created filehandle for the file.
125	might change in the future).
126		128
127	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	129	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
128	for an explanation.	130	for an explanation.
129		131
130	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	132	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
131	list. They are the same as used in C<sysopen>.	133	list. They are the same as used by C<sysopen>.
		134
		135	Likewise, C<$mode> specifies the mode of the newly created file, if it
		136	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		137	except that it is mandatory (i.e. use C<0> if you don't create new files,
		138	and C<0666> or C<0777> if you do).
132		139
133	Example:	140	Example:
134		141
135	aio_open "/etc/passwd", O_RDONLY, 0, sub {	142	aio_open "/etc/passwd", O_RDONLY, 0, sub {
136	if ($_[0] >= 0) {	143	if ($_[0]) {
137	open my $fh, "<&$_[0]"; # create a copy for perl
138	aio_close $_[0], sub { }; # close the aio handle
139	print "open successful, fh is $fh\n";	144	print "open successful, fh is $_[0]\n";
140	...	145	...
141	} else {	146	} else {
142	die "open failed: $!\n";	147	die "open failed: $!\n";
143	}	148	}
144	};	149	};
145		150
146	=item aio_close $fh, $callback	151	=item aio_close $fh, $callback->($status)
147		152
148	Asynchronously close a file and call the callback with the result code.	153	Asynchronously close a file and call the callback with the result
		154	code. I<WARNING:> although accepted, you should not pass in a perl
		155	filehandle here, as perl will likely close the file descriptor another
		156	time when the filehandle is destroyed. Normally, you can safely call perls
		157	C<close> or just let filehandles go out of scope.
149		158
		159	This is supposed to be a bug in the API, so that might change. It's
		160	therefore best to avoid this function.
		161
150	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	162	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
151		163
152	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	164	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
153		165
154	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	166	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
155	into the scalar given by C<data> and offset C<dataoffset> and calls the	167	into the scalar given by C<data> and offset C<dataoffset> and calls the
156	callback without the actual number of bytes read (or -1 on error, just	168	callback without the actual number of bytes read (or -1 on error, just
157	like the syscall).	169	like the syscall).
158		170
		171	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		172	is outstanding. Modifying it can result in segfaults or WW3 (if the
		173	necessary/optional hardware is installed).
		174
159	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	175	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
160	offset C<0> within the scalar:	176	offset C<0> within the scalar:
161		177
162	aio_read $fh, 7, 15, $buffer, 0, sub {	178	aio_read $fh, 7, 15, $buffer, 0, sub {
163	$_[0] >= 0 or die "read error: $!";	179	$_[0] > 0 or die "read error: $!";
164	print "read <$buffer>\n";	180	print "read $_[0] bytes: <$buffer>\n";
165	};	181	};
166		182
		183	=item aio_move $srcpath, $dstpath, $callback->($status)
		184
		185	Try to move the I<file> (directories not supported as either source or
		186	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		187	the C<0> (error) or C<-1> ok.
		188
		189	This is a composite request that tries to rename(2) the file first. If
		190	rename files with C<EXDEV>, it creates the destination file with mode 0200
		191	and copies the contents of the source file into it using C<aio_sendfile>,
		192	followed by restoring atime, mtime, access mode and uid/gid, in that
		193	order, and unlinking the C<$srcpath>.
		194
		195	If an error occurs, the partial destination file will be unlinked, if
		196	possible, except when setting atime, mtime, access mode and uid/gid, where
		197	errors are being ignored.
		198
		199	=cut
		200
		201	sub aio_move($$$) {
		202	my ($src, $dst, $cb) = @_;
		203
		204	aio_rename $src, $dst, sub {
		205	if ($_[0] && $! == EXDEV) {
		206	aio_open $src, O_RDONLY, 0, sub {
		207	if (my $src_fh = $_[0]) {
		208	my @stat = stat $src_fh;
		209
		210	aio_open $dst, O_WRONLY, 0200, sub {
		211	if (my $dst_fh = $_[0]) {
		212	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		213	close $src_fh;
		214
		215	if ($_[0] == $stat[7]) {
		216	utime $stat[8], $stat[9], $dst;
		217	chmod $stat[2] & 07777, $dst_fh;
		218	chown $stat[4], $stat[5], $dst_fh;
		219	close $dst_fh;
		220
		221	aio_unlink $src, sub {
		222	$cb->($_[0]);
		223	};
		224	} else {
		225	my $errno = $!;
		226	aio_unlink $dst, sub {
		227	$! = $errno;
		228	$cb->(-1);
		229	};
		230	}
		231	};
		232	} else {
		233	$cb->(-1);
		234	}
		235	},
		236
		237	} else {
		238	$cb->(-1);
		239	}
		240	};
		241	} else {
		242	$cb->($_[0]);
		243	}
		244	};
		245	}
		246
		247	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		248
		249	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		250	reading at byte offset C<$in_offset>, and starts writing at the current
		251	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		252	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		253	other.
		254
		255	This call tries to make use of a native C<sendfile> syscall to provide
		256	zero-copy operation. For this to work, C<$out_fh> should refer to a
		257	socket, and C<$in_fh> should refer to mmap'able file.
		258
		259	If the native sendfile call fails or is not implemented, it will be
		260	emulated, so you can call C<aio_sendfile> on any type of filehandle
		261	regardless of the limitations of the operating system.
		262
		263	Please note, however, that C<aio_sendfile> can read more bytes from
		264	C<$in_fh> than are written, and there is no way to find out how many
		265	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		266	provides the number of bytes written to C<$out_fh>. Only if the result
		267	value equals C<$length> one can assume that C<$length> bytes have been
		268	read.
		269
167	=item aio_readahead $fh,$offset,$length, $callback	270	=item aio_readahead $fh,$offset,$length, $callback->($retval)
168		271
169	Asynchronously reads the specified byte range into the page cache, using
170	the C<readahead> syscall. If that syscall doesn't exist the status will be
171	C<-1> and C<$!> is set to ENOSYS.
172
173	readahead() populates the page cache with data from a file so that	272	C<aio_readahead> populates the page cache with data from a file so that
174	subsequent reads from that file will not block on disk I/O. The C<$offset>	273	subsequent reads from that file will not block on disk I/O. The C<$offset>
175	argument specifies the starting point from which data is to be read and	274	argument specifies the starting point from which data is to be read and
176	C<$length> specifies the number of bytes to be read. I/O is performed in	275	C<$length> specifies the number of bytes to be read. I/O is performed in
177	whole pages, so that offset is effectively rounded down to a page boundary	276	whole pages, so that offset is effectively rounded down to a page boundary
178	and bytes are read up to the next page boundary greater than or equal to	277	and bytes are read up to the next page boundary greater than or equal to
179	(off-set+length). aio_readahead() does not read beyond the end of the	278	(off-set+length). C<aio_readahead> does not read beyond the end of the
180	file. The current file offset of the file is left unchanged.	279	file. The current file offset of the file is left unchanged.
181		280
		281	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		282	emulated by simply reading the data, which would have a similar effect.
		283
182	=item aio_stat $fh_or_path, $callback	284	=item aio_stat $fh_or_path, $callback->($status)
183		285
184	=item aio_lstat $fh, $callback	286	=item aio_lstat $fh, $callback->($status)
185		287
186	Works like perl's C<stat> or C<lstat> in void context. The callback will	288	Works like perl's C<stat> or C<lstat> in void context. The callback will
187	be called after the stat and the results will be available using C<stat _>	289	be called after the stat and the results will be available using C<stat _>
188	or C<-s _> etc...	290	or C<-s _> etc...
189		291
…		…
199	aio_stat "/etc/passwd", sub {	301	aio_stat "/etc/passwd", sub {
200	$_[0] and die "stat failed: $!";	302	$_[0] and die "stat failed: $!";
201	print "size is ", -s _, "\n";	303	print "size is ", -s _, "\n";
202	};	304	};
203		305
204	=item aio_unlink $pathname, $callback	306	=item aio_unlink $pathname, $callback->($status)
205		307
206	Asynchronously unlink (delete) a file and call the callback with the	308	Asynchronously unlink (delete) a file and call the callback with the
207	result code.	309	result code.
208		310
		311	=item aio_link $srcpath, $dstpath, $callback->($status)
		312
		313	Asynchronously create a new link to the existing object at C<$srcpath> at
		314	the path C<$dstpath> and call the callback with the result code.
		315
		316	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		317
		318	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		319	the path C<$dstpath> and call the callback with the result code.
		320
		321	=item aio_rename $srcpath, $dstpath, $callback->($status)
		322
		323	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		324	rename(2) and call the callback with the result code.
		325
		326	=item aio_rmdir $pathname, $callback->($status)
		327
		328	Asynchronously rmdir (delete) a directory and call the callback with the
		329	result code.
		330
		331	=item aio_readdir $pathname, $callback->($entries)
		332
		333	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		334	directory (i.e. opendir + readdir + closedir). The entries will not be
		335	sorted, and will B<NOT> include the C<.> and C<..> entries.
		336
		337	The callback a single argument which is either C<undef> or an array-ref
		338	with the filenames.
		339
		340	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		341
		342	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		343	separate the entries of directory C<$path> into two sets of names, ones
		344	you can recurse into (directories or links to them), and ones you cannot
		345	recurse into (everything else).
		346
		347	C<aio_scandir> is a composite request that consists of many sub
		348	requests. C<$maxreq> specifies the maximum number of outstanding aio
		349	requests that this function generates. If it is C<< <= 0 >>, then a
		350	suitable default will be chosen (currently 8).
		351
		352	On error, the callback is called without arguments, otherwise it receives
		353	two array-refs with path-relative entry names.
		354
		355	Example:
		356
		357	aio_scandir $dir, 0, sub {
		358	my ($dirs, $nondirs) = @_;
		359	print "real directories: @$dirs\n";
		360	print "everything else: @$nondirs\n";
		361	};
		362
		363	Implementation notes.
		364
		365	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		366
		367	After reading the directory, the modification time, size etc. of the
		368	directory before and after the readdir is checked, and if they match (and
		369	isn't the current time), the link count will be used to decide how many
		370	entries are directories (if >= 2). Otherwise, no knowledge of the number
		371	of subdirectories will be assumed.
		372
		373	Then entries will be sorted into likely directories (everything without
		374	a non-initial dot currently) and likely non-directories (everything
		375	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		376	likely directories first. If that succeeds, it assumes that the entry
		377	is a directory or a symlink to directory (which will be checked
		378	seperately). This is often faster than stat'ing the entry itself because
		379	filesystems might detect the type of the entry without reading the inode
		380	data (e.g. ext2fs filetype feature).
		381
		382	If the known number of directories (link count - 2) has been reached, the
		383	rest of the entries is assumed to be non-directories.
		384
		385	This only works with certainty on POSIX (= UNIX) filesystems, which
		386	fortunately are the vast majority of filesystems around.
		387
		388	It will also likely work on non-POSIX filesystems with reduced efficiency
		389	as those tend to return 0 or 1 as link counts, which disables the
		390	directory counting heuristic.
		391
		392	=cut
		393
		394	sub aio_scandir($$$) {
		395	my ($path, $maxreq, $cb) = @_;
		396
		397	$maxreq = 8 if $maxreq <= 0;
		398
		399	# stat once
		400	aio_stat $path, sub {
		401	return $cb->() if $_[0];
		402	my $now = time;
		403	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		404
		405	# read the directory entries
		406	aio_readdir $path, sub {
		407	my $entries = shift
		408	or return $cb->();
		409
		410	# stat the dir another time
		411	aio_stat $path, sub {
		412	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		413
		414	my $ndirs;
		415
		416	# take the slow route if anything looks fishy
		417	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		418	$ndirs = -1;
		419	} else {
		420	# if nlink == 2, we are finished
		421	# on non-posix-fs's, we rely on nlink < 2
		422	$ndirs = (stat _)[3] - 2
		423	or return $cb->([], $entries);
		424	}
		425
		426	# sort into likely dirs and likely nondirs
		427	# dirs == files without ".", short entries first
		428	$entries = [map $_->[0],
		429	sort { $b->[1] cmp $a->[1] }
		430	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		431	@$entries];
		432
		433	my (@dirs, @nondirs);
		434
		435	my ($statcb, $schedcb);
		436	my $nreq = 0;
		437
		438	$schedcb = sub {
		439	if (@$entries) {
		440	if ($nreq < $maxreq) {
		441	my $ent = pop @$entries;
		442	$nreq++;
		443	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		444	}
		445	} elsif (!$nreq) {
		446	# finished
		447	undef $statcb;
		448	undef $schedcb;
		449	$cb->(\@dirs, \@nondirs) if $cb;
		450	undef $cb;
		451	}
		452	};
		453	$statcb = sub {
		454	my ($status, $entry) = @_;
		455
		456	if ($status < 0) {
		457	$nreq--;
		458	push @nondirs, $entry;
		459	&$schedcb;
		460	} else {
		461	# need to check for real directory
		462	aio_lstat "$path/$entry", sub {
		463	$nreq--;
		464
		465	if (-d _) {
		466	push @dirs, $entry;
		467
		468	if (!--$ndirs) {
		469	push @nondirs, @$entries;
		470	$entries = [];
		471	}
		472	} else {
		473	push @nondirs, $entry;
		474	}
		475
		476	&$schedcb;
		477	}
		478	}
		479	};
		480
		481	&$schedcb while @$entries && $nreq < $maxreq;
		482	};
		483	};
		484	};
		485	}
		486
209	=item aio_fsync $fh, $callback	487	=item aio_fsync $fh, $callback->($status)
210		488
211	Asynchronously call fsync on the given filehandle and call the callback	489	Asynchronously call fsync on the given filehandle and call the callback
212	with the fsync result code.	490	with the fsync result code.
213		491
214	=item aio_fdatasync $fh, $callback	492	=item aio_fdatasync $fh, $callback->($status)
215		493
216	Asynchronously call fdatasync on the given filehandle and call the	494	Asynchronously call fdatasync on the given filehandle and call the
217	callback with the fdatasync result code.	495	callback with the fdatasync result code.
218		496
		497	If this call isn't available because your OS lacks it or it couldn't be
		498	detected, it will be emulated by calling C<fsync> instead.
		499
		500	=item aio_group $callback->()
		501
		502	=item aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		503
		504	Mainly used for debugging and benchmarking, this aio request puts one of
		505	the request workers to sleep for the given time.
		506
		507	=back
		508
		509	=head2 IO::AIO::REQ CLASS
		510
		511	All non-aggregate C<aio_*> functions return an object of this class when
		512	called in non-void context.
		513
		514	A request always moves through the following five states in its lifetime,
		515	in order: B<ready> (request has been created, but has not been executed
		516	yet), B<execute> (request is currently being executed), B<pending>
		517	(request has been executed but callback has not been called yet),
		518	B<result> (results are being processed synchronously, includes calling the
		519	callback) and B<done> (request has reached the end of its lifetime and
		520	holds no resources anymore).
		521
		522	=over 4
		523
		524	=item $req->cancel
		525
		526	Cancels the request, if possible. Has the effect of skipping execution
		527	when entering the B<execute> state and skipping calling the callback when
		528	entering the the B<result> state, but will leave the request otherwise
		529	untouched. That means that requests that currently execute will not be
		530	stopped and resources held by the request will not be freed prematurely.
		531
		532	=back
		533
		534	=head2 SUPPORT FUNCTIONS
		535
		536	=over 4
		537
		538	=item $fileno = IO::AIO::poll_fileno
		539
		540	Return the I<request result pipe file descriptor>. This filehandle must be
		541	polled for reading by some mechanism outside this module (e.g. Event or
		542	select, see below or the SYNOPSIS). If the pipe becomes readable you have
		543	to call C<poll_cb> to check the results.
		544
		545	See C<poll_cb> for an example.
		546
		547	=item IO::AIO::poll_cb
		548
		549	Process all outstanding events on the result pipe. You have to call this
		550	regularly. Returns the number of events processed. Returns immediately
		551	when no events are outstanding.
		552
		553	Example: Install an Event watcher that automatically calls
		554	IO::AIO::poll_cb with high priority:
		555
		556	Event->io (fd => IO::AIO::poll_fileno,
		557	poll => 'r', async => 1,
		558	cb => \&IO::AIO::poll_cb);
		559
		560	=item IO::AIO::poll_wait
		561
		562	Wait till the result filehandle becomes ready for reading (simply does a
		563	C<select> on the filehandle. This is useful if you want to synchronously wait
		564	for some requests to finish).
		565
		566	See C<nreqs> for an example.
		567
		568	=item IO::AIO::nreqs
		569
		570	Returns the number of requests currently outstanding (i.e. for which their
		571	callback has not been invoked yet).
		572
		573	Example: wait till there are no outstanding requests anymore:
		574
		575	IO::AIO::poll_wait, IO::AIO::poll_cb
		576	while IO::AIO::nreqs;
		577
		578	=item IO::AIO::flush
		579
		580	Wait till all outstanding AIO requests have been handled.
		581
		582	Strictly equivalent to:
		583
		584	IO::AIO::poll_wait, IO::AIO::poll_cb
		585	while IO::AIO::nreqs;
		586
		587	=item IO::AIO::poll
		588
		589	Waits until some requests have been handled.
		590
		591	Strictly equivalent to:
		592
		593	IO::AIO::poll_wait, IO::AIO::poll_cb
		594	if IO::AIO::nreqs;
		595
		596	=item IO::AIO::min_parallel $nthreads
		597
		598	Set the minimum number of AIO threads to C<$nthreads>. The current default
		599	is C<4>, which means four asynchronous operations can be done at one time
		600	(the number of outstanding operations, however, is unlimited).
		601
		602	IO::AIO starts threads only on demand, when an AIO request is queued and
		603	no free thread exists.
		604
		605	It is recommended to keep the number of threads low, as some Linux
		606	kernel versions will scale negatively with the number of threads (higher
		607	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
		608	threads should be fine.
		609
		610	Under most circumstances you don't need to call this function, as the
		611	module selects a default that is suitable for low to moderate load.
		612
		613	=item IO::AIO::max_parallel $nthreads
		614
		615	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		616	specified number of threads are currently running, this function kills
		617	them. This function blocks until the limit is reached.
		618
		619	While C<$nthreads> are zero, aio requests get queued but not executed
		620	until the number of threads has been increased again.
		621
		622	This module automatically runs C<max_parallel 0> at program end, to ensure
		623	that all threads are killed and that there are no outstanding requests.
		624
		625	Under normal circumstances you don't need to call this function.
		626
		627	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		628
		629	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		630	try to queue up more than this number of requests, the caller will block until
		631	some requests have been handled.
		632
		633	The default is very large, so normally there is no practical limit. If you
		634	queue up many requests in a loop it often improves speed if you set
		635	this to a relatively low number, such as C<100>.
		636
		637	Under normal circumstances you don't need to call this function.
		638
		639	=back
		640
219	=cut	641	=cut
		642
		643	# support function to convert a fd into a perl filehandle
		644	sub _fd2fh {
		645	return undef if $_[0] < 0;
		646
		647	# try to generate nice filehandles
		648	my $sym = "IO::AIO::fd#$_[0]";
		649	local *$sym;
		650
		651	open *$sym, "+<&=$_[0]" # usually works under any unix
		652	or open *$sym, "<&=$_[0]" # cygwin needs this
		653	or open *$sym, ">&=$_[0]" # or this
		654	or return undef;
		655
		656	*$sym
		657	}
220		658
221	min_parallel 4;	659	min_parallel 4;
222		660
223	END {	661	END {
224	max_parallel 0;	662	max_parallel 0;
225	}	663	}
226		664
227	1;	665	1;
228		666
229	=back	667	=head2 FORK BEHAVIOUR
230		668
231	=head1 BUGS	669	This module should do "the right thing" when the process using it forks:
232		670
233	- aio_open gives a fd, but all other functions expect a perl filehandle.	671	Before the fork, IO::AIO enters a quiescent state where no requests
		672	can be added in other threads and no results will be processed. After
		673	the fork the parent simply leaves the quiescent state and continues
		674	request/result processing, while the child clears the request/result
		675	queue (so the requests started before the fork will only be handled in
		676	the parent). Threads will be started on demand until the limit ste in the
		677	parent process has been reached again.
		678
		679	In short: the parent will, after a short pause, continue as if fork had
		680	not been called, while the child will act as if IO::AIO has not been used
		681	yet.
234		682
235	=head1 SEE ALSO	683	=head1 SEE ALSO
236		684
237	L<Coro>, L<Linux::AIO>.	685	L<Coro>, L<Linux::AIO> (obsolete).
238		686
239	=head1 AUTHOR	687	=head1 AUTHOR
240		688
241	Marc Lehmann <schmorp@schmorp.de>	689	Marc Lehmann <schmorp@schmorp.de>
242	http://home.schmorp.de/	690	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.1 by root, Sun Jul 10 17:07:44 2005 UTC vs. Revision 1.54 by root, Sun Oct 22 00:19:05 2006 UTC

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Comparing IO-AIO/AIO.pm (file contents):
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Revision 1.54 by root, Sun Oct 22 00:19:05 2006 UTC