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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.35 by root, Mon Aug 22 23:20:37 2005 UTC vs.
Revision 1.77 by root, Wed Oct 25 17:57:30 2006 UTC

…		…
15		15
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	16	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	17	$_[0] > 0 or die "read error: $!";
18	};	18	};
19		19
20	# Event	20	# version 2+ has request and group objects
		21	use IO::AIO 2;
		22
		23	aioreq_pri 4; # give next request a very high priority
		24	my $req = aio_unlink "/tmp/file", sub { };
		25	$req->cancel; # cancel request if still in queue
		26
		27	my $grp = aio_group sub { print "all stats done\n" };
		28	add $grp aio_stat "..." for ...;
		29
		30	# AnyEvent integration
		31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		33
		34	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	35	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	36	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	37	cb => \&IO::AIO::poll_cb);
24		38
25	# Glib/Gtk2	39	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	40	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb; 1 };	41	in => sub { IO::AIO::poll_cb; 1 };
28		42
29	# Tk	43	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	45	readable => \&IO::AIO::poll_cb);
32		46
33	# Danga::Socket	47	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	49	\&IO::AIO::poll_cb);
36		50
37
38	=head1 DESCRIPTION	51	=head1 DESCRIPTION
39		52
40	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
41	operating system supports.	54	operating system supports.
42		55
43	Currently, a number of threads are started that execute your read/writes	56	In this version, a number of threads are started that execute your
44	and signal their completion. You don't need thread support in your libc or	57	requests and signal their completion. You don't need thread support
45	perl, and the threads created by this module will not be visible to the	58	in perl, and the threads created by this module will not be visible
46	pthreads library. In the future, this module might make use of the native	59	to perl. In the future, this module might make use of the native aio
47	aio functions available on many operating systems. However, they are often	60	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	61	not well-supported or restricted (Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	62	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	63	aio_write, so the remaining functionality would have to be implemented
		64	using threads anyway.
51		65
52	Although the module will work with in the presence of other threads, it is	66	Although the module will work with in the presence of other (Perl-)
53	currently not reentrant, so use appropriate locking yourself, always call	67	threads, it is currently not reentrant in any way, so use appropriate
54	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	68	locking yourself, always call C<poll_cb> from within the same thread, or
55	C<aio_> functions) recursively.	69	never call C<poll_cb> (or other C<aio_> functions) recursively.
		70
		71	=head1 REQUEST ANATOMY AND LIFETIME
		72
		73	Every C<aio_*> function creates a request. which is a C data structure not
		74	directly visible to Perl.
		75
		76	If called in non-void context, every request function returns a Perl
		77	object representing the request. In void context, nothing is returned,
		78	which saves a bit of memory.
		79
		80	The perl object is a fairly standard ref-to-hash object. The hash contents
		81	are not used by IO::AIO so you are free to store anything you like in it.
		82
		83	During their existance, aio requests travel through the following states,
		84	in order:
		85
		86	=over 4
		87
		88	=item ready
		89
		90	Immediately after a request is created it is put into the ready state,
		91	waiting for a thread to execute it.
		92
		93	=item execute
		94
		95	A thread has accepted the request for processing and is currently
		96	executing it (e.g. blocking in read).
		97
		98	=item pending
		99
		100	The request has been executed and is waiting for result processing.
		101
		102	While request submission and execution is fully asynchronous, result
		103	processing is not and relies on the perl interpreter calling C<poll_cb>
		104	(or another function with the same effect).
		105
		106	=item result
		107
		108	The request results are processed synchronously by C<poll_cb>.
		109
		110	The C<poll_cb> function will process all outstanding aio requests by
		111	calling their callbacks, freeing memory associated with them and managing
		112	any groups they are contained in.
		113
		114	=item done
		115
		116	Request has reached the end of its lifetime and holds no resources anymore
		117	(except possibly for the Perl object, but its connection to the actual
		118	aio request is severed and calling its methods will either do nothing or
		119	result in a runtime error).
56		120
57	=cut	121	=cut
58		122
59	package IO::AIO;	123	package IO::AIO;
60		124
61	no warnings;	125	no warnings;
		126	use strict 'vars';
62		127
63	use base 'Exporter';	128	use base 'Exporter';
64		129
65	use Fcntl ();
66
67	BEGIN {	130	BEGIN {
68	$VERSION = 1.5;	131	our $VERSION = '2.0';
69		132
70	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	133	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71	aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead);	134	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	135	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		136	aio_group aio_nop);
		137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		139	min_parallel max_parallel nreqs);
		140
		141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
73		142
74	require XSLoader;	143	require XSLoader;
75	XSLoader::load IO::AIO, $VERSION;	144	XSLoader::load ("IO::AIO", $VERSION);
76	}	145	}
77		146
78	=head1 FUNCTIONS	147	=head1 FUNCTIONS
79		148
80	=head2 AIO FUNCTIONS	149	=head2 AIO FUNCTIONS
…		…
88	syscall has been executed asynchronously.	157	syscall has been executed asynchronously.
89		158
90	All functions expecting a filehandle keep a copy of the filehandle	159	All functions expecting a filehandle keep a copy of the filehandle
91	internally until the request has finished.	160	internally until the request has finished.
92		161
		162	All requests return objects of type L<IO::AIO::REQ> that allow further
		163	manipulation of those requests while they are in-flight.
		164
93	The pathnames you pass to these routines I<must> be absolute and	165	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	166	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	167	request is being executed, the current working directory could have
96	changed. Alternatively, you can make sure that you never change the	168	changed. Alternatively, you can make sure that you never change the
97	current working directory.	169	current working directory.
…		…
103	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	175	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
104	use something else.	176	use something else.
105		177
106	=over 4	178	=over 4
107		179
		180	=item aioreq_pri $pri
		181
		182	Sets the priority for the next aio request. The default priority
		183	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,
		184	respectively. Requests with higher priority will be serviced first.
		185
		186	The priority will be reset to C<0> after each call to one of the C<aio_>
		187	functions.
		188
		189	Example: open a file with low priority, then read something from it with
		190	higher priority so the read request is serviced before other low priority
		191	open requests (potentially spamming the cache):
		192
		193	aioreq_pri -3;
		194	aio_open ..., sub {
		195	return unless $_[0];
		196
		197	aioreq_pri -2;
		198	aio_read $_[0], ..., sub {
		199	...
		200	};
		201	};
		202
		203	=item aioreq_nice $pri_adjust
		204
		205	Similar to C<aioreq_pri>, but subtracts the given value from the current
		206	priority, so effects are cumulative.
		207
108	=item aio_open $pathname, $flags, $mode, $callback	208	=item aio_open $pathname, $flags, $mode, $callback->($fh)
109		209
110	Asynchronously open or create a file and call the callback with a newly	210	Asynchronously open or create a file and call the callback with a newly
111	created filehandle for the file.	211	created filehandle for the file.
112		212
113	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	213	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
130	} else {	230	} else {
131	die "open failed: $!\n";	231	die "open failed: $!\n";
132	}	232	}
133	};	233	};
134		234
135	=item aio_close $fh, $callback	235	=item aio_close $fh, $callback->($status)
136		236
137	Asynchronously close a file and call the callback with the result	237	Asynchronously close a file and call the callback with the result
138	code. I<WARNING:> although accepted, you should not pass in a perl	238	code. I<WARNING:> although accepted, you should not pass in a perl
139	filehandle here, as perl will likely close the file descriptor another	239	filehandle here, as perl will likely close the file descriptor another
140	time when the filehandle is destroyed. Normally, you can safely call perls	240	time when the filehandle is destroyed. Normally, you can safely call perls
141	C<close> or just let filehandles go out of scope.	241	C<close> or just let filehandles go out of scope.
142		242
143	This is supposed to be a bug in the API, so that might change. It's	243	This is supposed to be a bug in the API, so that might change. It's
144	therefore best to avoid this function.	244	therefore best to avoid this function.
145		245
146	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	246	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
147		247
148	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	248	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149		249
150	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	250	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	251	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	252	callback without the actual number of bytes read (or -1 on error, just
153	like the syscall).	253	like the syscall).
…		…
162	aio_read $fh, 7, 15, $buffer, 0, sub {	262	aio_read $fh, 7, 15, $buffer, 0, sub {
163	$_[0] > 0 or die "read error: $!";	263	$_[0] > 0 or die "read error: $!";
164	print "read $_[0] bytes: <$buffer>\n";	264	print "read $_[0] bytes: <$buffer>\n";
165	};	265	};
166		266
		267	=item aio_move $srcpath, $dstpath, $callback->($status)
		268
		269	Try to move the I<file> (directories not supported as either source or
		270	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		271	the C<0> (error) or C<-1> ok.
		272
		273	This is a composite request that tries to rename(2) the file first. If
		274	rename files with C<EXDEV>, it creates the destination file with mode 0200
		275	and copies the contents of the source file into it using C<aio_sendfile>,
		276	followed by restoring atime, mtime, access mode and uid/gid, in that
		277	order, and unlinking the C<$srcpath>.
		278
		279	If an error occurs, the partial destination file will be unlinked, if
		280	possible, except when setting atime, mtime, access mode and uid/gid, where
		281	errors are being ignored.
		282
		283	=cut
		284
		285	sub aio_move($$$) {
		286	my ($src, $dst, $cb) = @_;
		287
		288	my $grp = aio_group $cb;
		289
		290	add $grp aio_rename $src, $dst, sub {
		291	if ($_[0] && $! == EXDEV) {
		292	add $grp aio_open $src, O_RDONLY, 0, sub {
		293	if (my $src_fh = $_[0]) {
		294	my @stat = stat $src_fh;
		295
		296	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		297	if (my $dst_fh = $_[0]) {
		298	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		299	close $src_fh;
		300
		301	if ($_[0] == $stat[7]) {
		302	utime $stat[8], $stat[9], $dst;
		303	chmod $stat[2] & 07777, $dst_fh;
		304	chown $stat[4], $stat[5], $dst_fh;
		305	close $dst_fh;
		306
		307	add $grp aio_unlink $src, sub {
		308	$grp->result ($_[0]);
		309	};
		310	} else {
		311	my $errno = $!;
		312	add $grp aio_unlink $dst, sub {
		313	$! = $errno;
		314	$grp->result (-1);
		315	};
		316	}
		317	};
		318	} else {
		319	$grp->result (-1);
		320	}
		321	},
		322
		323	} else {
		324	$grp->result (-1);
		325	}
		326	};
		327	} else {
		328	$grp->result ($_[0]);
		329	}
		330	};
		331
		332	$grp
		333	}
		334
167	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback	335	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
168		336
169	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	337	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
170	reading at byte offset C<$in_offset>, and starts writing at the current	338	reading at byte offset C<$in_offset>, and starts writing at the current
171	file offset of C<$out_fh>. Because of that, it is not safe to issue more	339	file offset of C<$out_fh>. Because of that, it is not safe to issue more
172	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	340	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
…		…
175	This call tries to make use of a native C<sendfile> syscall to provide	343	This call tries to make use of a native C<sendfile> syscall to provide
176	zero-copy operation. For this to work, C<$out_fh> should refer to a	344	zero-copy operation. For this to work, C<$out_fh> should refer to a
177	socket, and C<$in_fh> should refer to mmap'able file.	345	socket, and C<$in_fh> should refer to mmap'able file.
178		346
179	If the native sendfile call fails or is not implemented, it will be	347	If the native sendfile call fails or is not implemented, it will be
180	emulated, so you can call C<aio_sendfile> on any filehandles regardless of	348	emulated, so you can call C<aio_sendfile> on any type of filehandle
181	the limitations of the OS.	349	regardless of the limitations of the operating system.
182		350
183	Please note, however, that C<aio_sendfile> can read more bytes from	351	Please note, however, that C<aio_sendfile> can read more bytes from
184	C<$in_fh> than are written, and there is no way to find out how many	352	C<$in_fh> than are written, and there is no way to find out how many
185	bytes have been read form C<aio_sendfile> alone, as C<aio_sendfile> only	353	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
186	provides the number of bytes written to C<$out_fh>. Only if the return	354	provides the number of bytes written to C<$out_fh>. Only if the result
187	value (the value provided to the callback) equals C<$length> one can	355	value equals C<$length> one can assume that C<$length> bytes have been
188	assume that C<$length> bytes have been read.	356	read.
189		357
190	=item aio_readahead $fh,$offset,$length, $callback	358	=item aio_readahead $fh,$offset,$length, $callback->($retval)
191		359
192	C<aio_readahead> populates the page cache with data from a file so that	360	C<aio_readahead> populates the page cache with data from a file so that
193	subsequent reads from that file will not block on disk I/O. The C<$offset>	361	subsequent reads from that file will not block on disk I/O. The C<$offset>
194	argument specifies the starting point from which data is to be read and	362	argument specifies the starting point from which data is to be read and
195	C<$length> specifies the number of bytes to be read. I/O is performed in	363	C<$length> specifies the number of bytes to be read. I/O is performed in
…		…
199	file. The current file offset of the file is left unchanged.	367	file. The current file offset of the file is left unchanged.
200		368
201	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	369	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
202	emulated by simply reading the data, which would have a similar effect.	370	emulated by simply reading the data, which would have a similar effect.
203		371
204	=item aio_stat $fh_or_path, $callback	372	=item aio_stat $fh_or_path, $callback->($status)
205		373
206	=item aio_lstat $fh, $callback	374	=item aio_lstat $fh, $callback->($status)
207		375
208	Works like perl's C<stat> or C<lstat> in void context. The callback will	376	Works like perl's C<stat> or C<lstat> in void context. The callback will
209	be called after the stat and the results will be available using C<stat _>	377	be called after the stat and the results will be available using C<stat _>
210	or C<-s _> etc...	378	or C<-s _> etc...
211		379
…		…
221	aio_stat "/etc/passwd", sub {	389	aio_stat "/etc/passwd", sub {
222	$_[0] and die "stat failed: $!";	390	$_[0] and die "stat failed: $!";
223	print "size is ", -s _, "\n";	391	print "size is ", -s _, "\n";
224	};	392	};
225		393
226	=item aio_unlink $pathname, $callback	394	=item aio_unlink $pathname, $callback->($status)
227		395
228	Asynchronously unlink (delete) a file and call the callback with the	396	Asynchronously unlink (delete) a file and call the callback with the
229	result code.	397	result code.
230		398
		399	=item aio_link $srcpath, $dstpath, $callback->($status)
		400
		401	Asynchronously create a new link to the existing object at C<$srcpath> at
		402	the path C<$dstpath> and call the callback with the result code.
		403
		404	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		405
		406	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		407	the path C<$dstpath> and call the callback with the result code.
		408
		409	=item aio_rename $srcpath, $dstpath, $callback->($status)
		410
		411	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		412	rename(2) and call the callback with the result code.
		413
231	=item aio_rmdir $pathname, $callback	414	=item aio_rmdir $pathname, $callback->($status)
232		415
233	Asynchronously rmdir (delete) a directory and call the callback with the	416	Asynchronously rmdir (delete) a directory and call the callback with the
234	result code.	417	result code.
235		418
		419	=item aio_readdir $pathname, $callback->($entries)
		420
		421	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		422	directory (i.e. opendir + readdir + closedir). The entries will not be
		423	sorted, and will B<NOT> include the C<.> and C<..> entries.
		424
		425	The callback a single argument which is either C<undef> or an array-ref
		426	with the filenames.
		427
		428	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		429
		430	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		431	efficiently separate the entries of directory C<$path> into two sets of
		432	names, directories you can recurse into (directories), and ones you cannot
		433	recurse into (everything else, including symlinks to directories).
		434
		435	C<aio_scandir> is a composite request that creates of many sub requests_
		436	C<$maxreq> specifies the maximum number of outstanding aio requests that
		437	this function generates. If it is C<< <= 0 >>, then a suitable default
		438	will be chosen (currently 6).
		439
		440	On error, the callback is called without arguments, otherwise it receives
		441	two array-refs with path-relative entry names.
		442
		443	Example:
		444
		445	aio_scandir $dir, 0, sub {
		446	my ($dirs, $nondirs) = @_;
		447	print "real directories: @$dirs\n";
		448	print "everything else: @$nondirs\n";
		449	};
		450
		451	Implementation notes.
		452
		453	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		454
		455	After reading the directory, the modification time, size etc. of the
		456	directory before and after the readdir is checked, and if they match (and
		457	isn't the current time), the link count will be used to decide how many
		458	entries are directories (if >= 2). Otherwise, no knowledge of the number
		459	of subdirectories will be assumed.
		460
		461	Then entries will be sorted into likely directories (everything without
		462	a non-initial dot currently) and likely non-directories (everything
		463	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		464	likely directories first. If that succeeds, it assumes that the entry
		465	is a directory or a symlink to directory (which will be checked
		466	seperately). This is often faster than stat'ing the entry itself because
		467	filesystems might detect the type of the entry without reading the inode
		468	data (e.g. ext2fs filetype feature).
		469
		470	If the known number of directories (link count - 2) has been reached, the
		471	rest of the entries is assumed to be non-directories.
		472
		473	This only works with certainty on POSIX (= UNIX) filesystems, which
		474	fortunately are the vast majority of filesystems around.
		475
		476	It will also likely work on non-POSIX filesystems with reduced efficiency
		477	as those tend to return 0 or 1 as link counts, which disables the
		478	directory counting heuristic.
		479
		480	=cut
		481
		482	sub aio_scandir($$$) {
		483	my ($path, $maxreq, $cb) = @_;
		484
		485	my $grp = aio_group $cb;
		486
		487	$maxreq = 6 if $maxreq <= 0;
		488
		489	# stat once
		490	add $grp aio_stat $path, sub {
		491	return $grp->result () if $_[0];
		492	my $now = time;
		493	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		494
		495	# read the directory entries
		496	add $grp aio_readdir $path, sub {
		497	my $entries = shift
		498	or return $grp->result ();
		499
		500	# stat the dir another time
		501	add $grp aio_stat $path, sub {
		502	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		503
		504	my $ndirs;
		505
		506	# take the slow route if anything looks fishy
		507	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		508	$ndirs = -1;
		509	} else {
		510	# if nlink == 2, we are finished
		511	# on non-posix-fs's, we rely on nlink < 2
		512	$ndirs = (stat _)[3] - 2
		513	or return $grp->result ([], $entries);
		514	}
		515
		516	# sort into likely dirs and likely nondirs
		517	# dirs == files without ".", short entries first
		518	$entries = [map $_->[0],
		519	sort { $b->[1] cmp $a->[1] }
		520	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		521	@$entries];
		522
		523	my (@dirs, @nondirs);
		524
		525	my $statgrp = add $grp aio_group sub {
		526	$grp->result (\@dirs, \@nondirs);
		527	};
		528
		529	limit $statgrp $maxreq;
		530	feed $statgrp sub {
		531	return unless @$entries;
		532	my $entry = pop @$entries;
		533
		534	add $statgrp aio_stat "$path/$entry/.", sub {
		535	if ($_[0] < 0) {
		536	push @nondirs, $entry;
		537	} else {
		538	# need to check for real directory
		539	add $statgrp aio_lstat "$path/$entry", sub {
		540	if (-d _) {
		541	push @dirs, $entry;
		542
		543	unless (--$ndirs) {
		544	push @nondirs, @$entries;
		545	feed $statgrp;
		546	}
		547	} else {
		548	push @nondirs, $entry;
		549	}
		550	}
		551	}
		552	};
		553	};
		554	};
		555	};
		556	};
		557
		558	$grp
		559	}
		560
236	=item aio_fsync $fh, $callback	561	=item aio_fsync $fh, $callback->($status)
237		562
238	Asynchronously call fsync on the given filehandle and call the callback	563	Asynchronously call fsync on the given filehandle and call the callback
239	with the fsync result code.	564	with the fsync result code.
240		565
241	=item aio_fdatasync $fh, $callback	566	=item aio_fdatasync $fh, $callback->($status)
242		567
243	Asynchronously call fdatasync on the given filehandle and call the	568	Asynchronously call fdatasync on the given filehandle and call the
244	callback with the fdatasync result code.	569	callback with the fdatasync result code.
245		570
246	If this call isn't available because your OS lacks it or it couldn't be	571	If this call isn't available because your OS lacks it or it couldn't be
247	detected, it will be emulated by calling C<fsync> instead.	572	detected, it will be emulated by calling C<fsync> instead.
		573
		574	=item aio_group $callback->(...)
		575
		576	This is a very special aio request: Instead of doing something, it is a
		577	container for other aio requests, which is useful if you want to bundle
		578	many requests into a single, composite, request with a definite callback
		579	and the ability to cancel the whole request with its subrequests.
		580
		581	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		582	for more info.
		583
		584	Example:
		585
		586	my $grp = aio_group sub {
		587	print "all stats done\n";
		588	};
		589
		590	add $grp
		591	(aio_stat ...),
		592	(aio_stat ...),
		593	...;
		594
		595	=item aio_nop $callback->()
		596
		597	This is a special request - it does nothing in itself and is only used for
		598	side effects, such as when you want to add a dummy request to a group so
		599	that finishing the requests in the group depends on executing the given
		600	code.
		601
		602	While this request does nothing, it still goes through the execution
		603	phase and still requires a worker thread. Thus, the callback will not
		604	be executed immediately but only after other requests in the queue have
		605	entered their execution phase. This can be used to measure request
		606	latency.
		607
		608	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		609
		610	Mainly used for debugging and benchmarking, this aio request puts one of
		611	the request workers to sleep for the given time.
		612
		613	While it is theoretically handy to have simple I/O scheduling requests
		614	like sleep and file handle readable/writable, the overhead this creates is
		615	immense (it blocks a thread for a long time) so do not use this function
		616	except to put your application under artificial I/O pressure.
		617
		618	=back
		619
		620	=head2 IO::AIO::REQ CLASS
		621
		622	All non-aggregate C<aio_*> functions return an object of this class when
		623	called in non-void context.
		624
		625	=over 4
		626
		627	=item cancel $req
		628
		629	Cancels the request, if possible. Has the effect of skipping execution
		630	when entering the B<execute> state and skipping calling the callback when
		631	entering the the B<result> state, but will leave the request otherwise
		632	untouched. That means that requests that currently execute will not be
		633	stopped and resources held by the request will not be freed prematurely.
		634
		635	=item cb $req $callback->(...)
		636
		637	Replace (or simply set) the callback registered to the request.
		638
		639	=back
		640
		641	=head2 IO::AIO::GRP CLASS
		642
		643	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		644	objects of this class, too.
		645
		646	A IO::AIO::GRP object is a special request that can contain multiple other
		647	aio requests.
		648
		649	You create one by calling the C<aio_group> constructing function with a
		650	callback that will be called when all contained requests have entered the
		651	C<done> state:
		652
		653	my $grp = aio_group sub {
		654	print "all requests are done\n";
		655	};
		656
		657	You add requests by calling the C<add> method with one or more
		658	C<IO::AIO::REQ> objects:
		659
		660	$grp->add (aio_unlink "...");
		661
		662	add $grp aio_stat "...", sub {
		663	$_[0] or return $grp->result ("error");
		664
		665	# add another request dynamically, if first succeeded
		666	add $grp aio_open "...", sub {
		667	$grp->result ("ok");
		668	};
		669	};
		670
		671	This makes it very easy to create composite requests (see the source of
		672	C<aio_move> for an application) that work and feel like simple requests.
		673
		674	=over 4
		675
		676	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		677	C<IO::AIO::poll_cb>, just like any other request.
		678
		679	=item * They can be canceled like any other request. Canceling will cancel not
		680	only the request itself, but also all requests it contains.
		681
		682	=item * They can also can also be added to other IO::AIO::GRP objects.
		683
		684	=item * You must not add requests to a group from within the group callback (or
		685	any later time).
		686
		687	=back
		688
		689	Their lifetime, simplified, looks like this: when they are empty, they
		690	will finish very quickly. If they contain only requests that are in the
		691	C<done> state, they will also finish. Otherwise they will continue to
		692	exist.
		693
		694	That means after creating a group you have some time to add requests. And
		695	in the callbacks of those requests, you can add further requests to the
		696	group. And only when all those requests have finished will the the group
		697	itself finish.
		698
		699	=over 4
		700
		701	=item add $grp ...
		702
		703	=item $grp->add (...)
		704
		705	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		706	be added, including other groups, as long as you do not create circular
		707	dependencies.
		708
		709	Returns all its arguments.
		710
		711	=item $grp->cancel_subs
		712
		713	Cancel all subrequests and clears any feeder, but not the group request
		714	itself. Useful when you queued a lot of events but got a result early.
		715
		716	=item $grp->result (...)
		717
		718	Set the result value(s) that will be passed to the group callback when all
		719	subrequests have finished. By default, no argument will be passed.
		720
		721	=item feed $grp $callback->($grp)
		722
		723	Sets a feeder/generator on this group: every group can have an attached
		724	generator that generates requests if idle. The idea behind this is that,
		725	although you could just queue as many requests as you want in a group,
		726	this might starve other requests for a potentially long time. For
		727	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		728	requests, delaying any later requests for a long time.
		729
		730	To avoid this, and allow incremental generation of requests, you can
		731	instead a group and set a feeder on it that generates those requests. The
		732	feed callback will be called whenever there are few enough (see C<limit>,
		733	below) requests active in the group itself and is expected to queue more
		734	requests.
		735
		736	The feed callback can queue as many requests as it likes (i.e. C<add> does
		737	not impose any limits).
		738
		739	If the feed does not queue more requests when called, it will be
		740	automatically removed from the group.
		741
		742	If the feed limit is C<0>, it will be set to C<2> automatically.
		743
		744	Example:
		745
		746	# stat all files in @files, but only ever use four aio requests concurrently:
		747
		748	my $grp = aio_group sub { print "finished\n" };
		749	limit $grp 4;
		750	feed $grp sub {
		751	my $file = pop @files
		752	or return;
		753
		754	add $grp aio_stat $file, sub { ... };
		755	};
		756
		757	=item limit $grp $num
		758
		759	Sets the feeder limit for the group: The feeder will be called whenever
		760	the group contains less than this many requests.
		761
		762	Setting the limit to C<0> will pause the feeding process.
248		763
249	=back	764	=back
250		765
251	=head2 SUPPORT FUNCTIONS	766	=head2 SUPPORT FUNCTIONS
252		767
…		…
310	IO::AIO::poll_wait, IO::AIO::poll_cb	825	IO::AIO::poll_wait, IO::AIO::poll_cb
311	if IO::AIO::nreqs;	826	if IO::AIO::nreqs;
312		827
313	=item IO::AIO::min_parallel $nthreads	828	=item IO::AIO::min_parallel $nthreads
314		829
315	Set the minimum number of AIO threads to C<$nthreads>. The current default	830	Set the minimum number of AIO threads to C<$nthreads>. The current
316	is C<4>, which means four asynchronous operations can be done at one time	831	default is C<8>, which means eight asynchronous operations can execute
317	(the number of outstanding operations, however, is unlimited).	832	concurrently at any one time (the number of outstanding requests,
		833	however, is unlimited).
318		834
319	IO::AIO starts threads only on demand, when an AIO request is queued and	835	IO::AIO starts threads only on demand, when an AIO request is queued and
320	no free thread exists.	836	no free thread exists.
321		837
322	It is recommended to keep the number of threads low, as some Linux	838	It is recommended to keep the number of threads relatively low, as some
323	kernel versions will scale negatively with the number of threads (higher	839	Linux kernel versions will scale negatively with the number of threads
324	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	840	(higher parallelity => MUCH higher latency). With current Linux 2.6
325	threads should be fine.	841	versions, 4-32 threads should be fine.
326		842
327	Under most circumstances you don't need to call this function, as the	843	Under most circumstances you don't need to call this function, as the
328	module selects a default that is suitable for low to moderate load.	844	module selects a default that is suitable for low to moderate load.
329		845
330	=item IO::AIO::max_parallel $nthreads	846	=item IO::AIO::max_parallel $nthreads
…		…
341		857
342	Under normal circumstances you don't need to call this function.	858	Under normal circumstances you don't need to call this function.
343		859
344	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	860	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
345		861
		862	[REMOVED]
		863
		864	Pre-2.x versions used max_outstanding for a crude request queue length limit.
		865
		866	In 2.x+ you are advised to use a group and a feeder to limit
		867	concurrency. The max_outstanding feature ran very unstable (endless
		868	recursions causing segfaults, bad interaction with groups etc.) and was
		869	removed.
		870
		871	I am deeply sorry, but I am still on the hunt for a good limiting interface.
		872
		873	Original description was as follows:
		874
346	Sets the maximum number of outstanding requests to C<$nreqs>. If you	875	Sets the maximum number of outstanding requests to C<$nreqs>. If you try
347	try to queue up more than this number of requests, the caller will block until	876	to queue up more than this number of requests, the caller will block until
348	some requests have been handled.	877	some requests have been handled.
349
350	The default is very large, so normally there is no practical limit. If you
351	queue up many requests in a loop it often improves speed if you set
352	this to a relatively low number, such as C<100>.
353
354	Under normal circumstances you don't need to call this function.
355		878
356	=back	879	=back
357		880
358	=cut	881	=cut
359		882
…		…
371	or return undef;	894	or return undef;
372		895
373	*$sym	896	*$sym
374	}	897	}
375		898
376	min_parallel 4;	899	min_parallel 8;
377		900
378	END {	901	END {
379	max_parallel 0;	902	max_parallel 0;
380	}	903	}
381		904
382	1;	905	1;
383		906
384	=head2 FORK BEHAVIOUR	907	=head2 FORK BEHAVIOUR
385		908
		909	This module should do "the right thing" when the process using it forks:
		910
386	Before the fork, IO::AIO enters a quiescent state where no requests	911	Before the fork, IO::AIO enters a quiescent state where no requests
387	can be added in other threads and no results will be processed. After	912	can be added in other threads and no results will be processed. After
388	the fork the parent simply leaves the quiescent state and continues	913	the fork the parent simply leaves the quiescent state and continues
389	request/result processing, while the child clears the request/result	914	request/result processing, while the child frees the request/result queue
390	queue (so the requests started before the fork will only be handled in	915	(so that the requests started before the fork will only be handled in the
391	the parent). Threats will be started on demand until the limit ste in the	916	parent). Threads will be started on demand until the limit set in the
392	parent process has been reached again.	917	parent process has been reached again.
393		918
		919	In short: the parent will, after a short pause, continue as if fork had
		920	not been called, while the child will act as if IO::AIO has not been used
		921	yet.
		922
		923	=head2 MEMORY USAGE
		924
		925	Per-request usage:
		926
		927	Each aio request uses - depending on your architecture - around 100-200
		928	bytes of memory. In addition, stat requests need a stat buffer (possibly
		929	a few hundred bytes), readdir requires a result buffer and so on. Perl
		930	scalars and other data passed into aio requests will also be locked and
		931	will consume memory till the request has entered the done state.
		932
		933	This is now awfully much, so queuing lots of requests is not usually a
		934	problem.
		935
		936	Per-thread usage:
		937
		938	In the execution phase, some aio requests require more memory for
		939	temporary buffers, and each thread requires a stack and other data
		940	structures (usually around 16k-128k, depending on the OS).
		941
		942	=head1 KNOWN BUGS
		943
		944	Known bugs will be fixed in the next release.
		945
394	=head1 SEE ALSO	946	=head1 SEE ALSO
395		947
396	L<Coro>, L<Linux::AIO>.	948	L<Coro::AIO>.
397		949
398	=head1 AUTHOR	950	=head1 AUTHOR
399		951
400	Marc Lehmann <schmorp@schmorp.de>	952	Marc Lehmann <schmorp@schmorp.de>
401	http://home.schmorp.de/	953	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.35 by root, Mon Aug 22 23:20:37 2005 UTC vs.
Revision 1.77 by root, Wed Oct 25 17:57:30 2006 UTC