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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.2 by root, Sun Jul 10 18:16:49 2005 UTC vs.
Revision 1.83 by root, Fri Oct 27 20:11:58 2006 UTC

…		…
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
		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	# 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
		35	Event->io (fd => IO::AIO::poll_fileno,
		36	poll => 'r',
		37	cb => \&IO::AIO::poll_cb);
		38
		39	# Glib/Gtk2 integration
		40	add_watch Glib::IO IO::AIO::poll_fileno,
		41	in => sub { IO::AIO::poll_cb; 1 };
		42
		43	# Tk integration
		44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		45	readable => \&IO::AIO::poll_cb);
		46
		47	# Danga::Socket integration
		48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		49	\&IO::AIO::poll_cb);
8		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
11	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
12	operating system supports.	54	operating system supports.
13		55
14	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
15	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
16	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
17	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
18	aio functions available on many operating systems. However, they are often	60	functions available on many operating systems. However, they are often
19	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
20	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
21	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.
22		65
23	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-)
24	currently not reentrant, so use appropriate locking yourself.	67	threads, it is currently not reentrant in any way, so use appropriate
		68	locking yourself, always call C<poll_cb> from within the same thread, or
		69	never call C<poll_cb> (or other C<aio_> functions) recursively.
25		70
26	=head2 API NOTES	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).
		120
		121	=cut
		122
		123	package IO::AIO;
		124
		125	no warnings;
		126	use strict 'vars';
		127
		128	use base 'Exporter';
		129
		130	BEGIN {
		131	our $VERSION = '2.0';
		132
		133	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
		134	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
		135	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		136	aio_copy aio_group aio_nop aio_mknod);
		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 nready npending);
		140
		141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
		142
		143	require XSLoader;
		144	XSLoader::load ("IO::AIO", $VERSION);
		145	}
		146
		147	=head1 FUNCTIONS
		148
		149	=head2 AIO FUNCTIONS
27		150
28	All the C<aio_*> calls are more or less thin wrappers around the syscall	151	All the C<aio_*> calls are more or less thin wrappers around the syscall
29	with the same name (sans C<aio_>). The arguments are similar or identical,	152	with the same name (sans C<aio_>). The arguments are similar or identical,
30	and they all accept an additional C<$callback> argument which must be	153	and they all accept an additional (and optional) C<$callback> argument
31	a code reference. This code reference will get called with the syscall	154	which must be a code reference. This code reference will get called with
32	return code (e.g. most syscalls return C<-1> on error, unlike perl, which	155	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
33	usually delivers "false") as it's sole argument when the given syscall has	156	perl, which usually delivers "false") as it's sole argument when the given
34	been executed asynchronously.	157	syscall has been executed asynchronously.
35		158
36	All functions that expect a filehandle will also accept a file descriptor.	159	All functions expecting a filehandle keep a copy of the filehandle
		160	internally until the request has finished.
37		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
38	The filenames you pass to these routines I<must> be absolute. The reason	165	The pathnames you pass to these routines I<must> be absolute and
39	is that at the time the request is being executed, the current working	166	encoded in byte form. The reason for the former is that at the time the
40	directory could have changed. Alternatively, you can make sure that you	167	request is being executed, the current working directory could have
		168	changed. Alternatively, you can make sure that you never change the
41	never change the current working directory.	169	current working directory.
		170
		171	To encode pathnames to byte form, either make sure you either: a)
		172	always pass in filenames you got from outside (command line, readdir
		173	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		174	your pathnames to the locale (or other) encoding in effect in the user
		175	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		176	use something else.
42		177
43	=over 4	178	=over 4
44		179
45	=cut	180	=item $prev_pri = aioreq_pri [$pri]
46		181
47	package IO::AIO;	182	Returns the priority value that would be used for the next request and, if
		183	C<$pri> is given, sets the priority for the next aio request.
48		184
49	use base 'Exporter';	185	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		186	and C<4>, respectively. Requests with higher priority will be serviced
		187	first.
50		188
51	use Fcntl ();	189	The priority will be reset to C<0> after each call to one of the C<aio_*>
		190	functions.
52		191
53	BEGIN {	192	Example: open a file with low priority, then read something from it with
54	$VERSION = 0.1;	193	higher priority so the read request is serviced before other low priority
		194	open requests (potentially spamming the cache):
55		195
56	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	196	aioreq_pri -3;
57	aio_fsync aio_fdatasync aio_readahead);	197	aio_open ..., sub {
58	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs);	198	return unless $_[0];
59		199
60	require XSLoader;	200	aioreq_pri -2;
61	XSLoader::load IO::AIO, $VERSION;	201	aio_read $_[0], ..., sub {
62	}	202	...
		203	};
		204	};
63		205
64	=item IO::AIO::min_parallel $nthreads	206	=item aioreq_nice $pri_adjust
65		207
66	Set the minimum number of AIO threads to C<$nthreads>. The default is	208	Similar to C<aioreq_pri>, but subtracts the given value from the current
67	C<1>, which means a single asynchronous operation can be done at one time	209	priority, so effects are cumulative.
68	(the number of outstanding operations, however, is unlimited).
69		210
70	It is recommended to keep the number of threads low, as some linux
71	kernel versions will scale negatively with the number of threads (higher
72	parallelity => MUCH higher latency).
73
74	Under normal circumstances you don't need to call this function, as this
75	module automatically starts a single async thread.
76
77	=item IO::AIO::max_parallel $nthreads
78
79	Sets the maximum number of AIO threads to C<$nthreads>. If more than
80	the specified number of threads are currently running, kill them. This
81	function blocks until the limit is reached.
82
83	This module automatically runs C<max_parallel 0> at program end, to ensure
84	that all threads are killed and that there are no outstanding requests.
85
86	Under normal circumstances you don't need to call this function.
87
88	=item $fileno = IO::AIO::poll_fileno
89
90	Return the I<request result pipe filehandle>. This filehandle must be
91	polled for reading by some mechanism outside this module (e.g. Event
92	or select, see below). If the pipe becomes readable you have to call
93	C<poll_cb> to check the results.
94
95	See C<poll_cb> for an example.
96
97	=item IO::AIO::poll_cb
98
99	Process all outstanding events on the result pipe. You have to call this
100	regularly. Returns the number of events processed. Returns immediately
101	when no events are outstanding.
102
103	You can use Event to multiplex, e.g.:
104
105	Event->io (fd => IO::AIO::poll_fileno,
106	poll => 'r', async => 1,
107	cb => \&IO::AIO::poll_cb);
108
109	=item IO::AIO::poll_wait
110
111	Wait till the result filehandle becomes ready for reading (simply does a
112	select on the filehandle. This is useful if you want to synchronously wait
113	for some requests to finish).
114
115	See C<nreqs> for an example.
116
117	=item IO::AIO::nreqs
118
119	Returns the number of requests currently outstanding.
120
121	Example: wait till there are no outstanding requests anymore:
122
123	IO::AIO::poll_wait, IO::AIO::poll_cb
124	while IO::AIO::nreqs;
125
126	=item aio_open $pathname, $flags, $mode, $callback	211	=item aio_open $pathname, $flags, $mode, $callback->($fh)
127		212
128	Asynchronously open or create a file and call the callback with a newly	213	Asynchronously open or create a file and call the callback with a newly
129	created filehandle for the file.	214	created filehandle for the file.
130		215
131	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	216	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
132	for an explanation.	217	for an explanation.
133		218
134	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	219	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
135	list. They are the same as used in C<sysopen>.	220	list. They are the same as used by C<sysopen>.
		221
		222	Likewise, C<$mode> specifies the mode of the newly created file, if it
		223	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		224	except that it is mandatory (i.e. use C<0> if you don't create new files,
		225	and C<0666> or C<0777> if you do).
136		226
137	Example:	227	Example:
138		228
139	aio_open "/etc/passwd", O_RDONLY, 0, sub {	229	aio_open "/etc/passwd", O_RDONLY, 0, sub {
140	if ($_[0]) {	230	if ($_[0]) {
…		…
143	} else {	233	} else {
144	die "open failed: $!\n";	234	die "open failed: $!\n";
145	}	235	}
146	};	236	};
147		237
148	=item aio_close $fh, $callback	238	=item aio_close $fh, $callback->($status)
149		239
150	Asynchronously close a file and call the callback with the result	240	Asynchronously close a file and call the callback with the result
151	code. I<WARNING:> although accepted, you should not pass in a perl	241	code. I<WARNING:> although accepted, you should not pass in a perl
152	filehandle here, as perl will likely close the file descriptor itself when	242	filehandle here, as perl will likely close the file descriptor another
153	the filehandle is destroyed. Normally, you can safely call perls C<close>	243	time when the filehandle is destroyed. Normally, you can safely call perls
154	or just let filehandles go out of scope.	244	C<close> or just let filehandles go out of scope.
155		245
		246	This is supposed to be a bug in the API, so that might change. It's
		247	therefore best to avoid this function.
		248
156	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	249	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
157		250
158	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	251	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159		252
160	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	253	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
161	into the scalar given by C<data> and offset C<dataoffset> and calls the	254	into the scalar given by C<data> and offset C<dataoffset> and calls the
162	callback without the actual number of bytes read (or -1 on error, just	255	callback without the actual number of bytes read (or -1 on error, just
163	like the syscall).	256	like the syscall).
164		257
		258	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		259	is outstanding. Modifying it can result in segfaults or WW3 (if the
		260	necessary/optional hardware is installed).
		261
165	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	262	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
166	offset C<0> within the scalar:	263	offset C<0> within the scalar:
167		264
168	aio_read $fh, 7, 15, $buffer, 0, sub {	265	aio_read $fh, 7, 15, $buffer, 0, sub {
169	$_[0] >= 0 or die "read error: $!";	266	$_[0] > 0 or die "read error: $!";
170	print "read <$buffer>\n";	267	print "read $_[0] bytes: <$buffer>\n";
171	};	268	};
172		269
		270	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		271
		272	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		273	reading at byte offset C<$in_offset>, and starts writing at the current
		274	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		275	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		276	other.
		277
		278	This call tries to make use of a native C<sendfile> syscall to provide
		279	zero-copy operation. For this to work, C<$out_fh> should refer to a
		280	socket, and C<$in_fh> should refer to mmap'able file.
		281
		282	If the native sendfile call fails or is not implemented, it will be
		283	emulated, so you can call C<aio_sendfile> on any type of filehandle
		284	regardless of the limitations of the operating system.
		285
		286	Please note, however, that C<aio_sendfile> can read more bytes from
		287	C<$in_fh> than are written, and there is no way to find out how many
		288	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		289	provides the number of bytes written to C<$out_fh>. Only if the result
		290	value equals C<$length> one can assume that C<$length> bytes have been
		291	read.
		292
173	=item aio_readahead $fh,$offset,$length, $callback	293	=item aio_readahead $fh,$offset,$length, $callback->($retval)
174		294
175	Asynchronously reads the specified byte range into the page cache, using
176	the C<readahead> syscall. If that syscall doesn't exist the status will be
177	C<-1> and C<$!> is set to ENOSYS.
178
179	readahead() populates the page cache with data from a file so that	295	C<aio_readahead> populates the page cache with data from a file so that
180	subsequent reads from that file will not block on disk I/O. The C<$offset>	296	subsequent reads from that file will not block on disk I/O. The C<$offset>
181	argument specifies the starting point from which data is to be read and	297	argument specifies the starting point from which data is to be read and
182	C<$length> specifies the number of bytes to be read. I/O is performed in	298	C<$length> specifies the number of bytes to be read. I/O is performed in
183	whole pages, so that offset is effectively rounded down to a page boundary	299	whole pages, so that offset is effectively rounded down to a page boundary
184	and bytes are read up to the next page boundary greater than or equal to	300	and bytes are read up to the next page boundary greater than or equal to
185	(off-set+length). aio_readahead() does not read beyond the end of the	301	(off-set+length). C<aio_readahead> does not read beyond the end of the
186	file. The current file offset of the file is left unchanged.	302	file. The current file offset of the file is left unchanged.
187		303
		304	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		305	emulated by simply reading the data, which would have a similar effect.
		306
188	=item aio_stat $fh_or_path, $callback	307	=item aio_stat $fh_or_path, $callback->($status)
189		308
190	=item aio_lstat $fh, $callback	309	=item aio_lstat $fh, $callback->($status)
191		310
192	Works like perl's C<stat> or C<lstat> in void context. The callback will	311	Works like perl's C<stat> or C<lstat> in void context. The callback will
193	be called after the stat and the results will be available using C<stat _>	312	be called after the stat and the results will be available using C<stat _>
194	or C<-s _> etc...	313	or C<-s _> etc...
195		314
…		…
205	aio_stat "/etc/passwd", sub {	324	aio_stat "/etc/passwd", sub {
206	$_[0] and die "stat failed: $!";	325	$_[0] and die "stat failed: $!";
207	print "size is ", -s _, "\n";	326	print "size is ", -s _, "\n";
208	};	327	};
209		328
210	=item aio_unlink $pathname, $callback	329	=item aio_unlink $pathname, $callback->($status)
211		330
212	Asynchronously unlink (delete) a file and call the callback with the	331	Asynchronously unlink (delete) a file and call the callback with the
213	result code.	332	result code.
214		333
		334	=item aio_mknod $path, $mode, $dev, $callback->($status)
		335
		336	Asynchronously create a device node (or fifo). See mknod(2).
		337
		338	The only portable (POSIX) way of calling this function is:
		339
		340	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		341
		342	=item aio_link $srcpath, $dstpath, $callback->($status)
		343
		344	Asynchronously create a new link to the existing object at C<$srcpath> at
		345	the path C<$dstpath> and call the callback with the result code.
		346
		347	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		348
		349	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		350	the path C<$dstpath> and call the callback with the result code.
		351
		352	=item aio_rename $srcpath, $dstpath, $callback->($status)
		353
		354	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		355	rename(2) and call the callback with the result code.
		356
		357	=item aio_rmdir $pathname, $callback->($status)
		358
		359	Asynchronously rmdir (delete) a directory and call the callback with the
		360	result code.
		361
		362	=item aio_readdir $pathname, $callback->($entries)
		363
		364	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		365	directory (i.e. opendir + readdir + closedir). The entries will not be
		366	sorted, and will B<NOT> include the C<.> and C<..> entries.
		367
		368	The callback a single argument which is either C<undef> or an array-ref
		369	with the filenames.
		370
		371	=item aio_copy $srcpath, $dstpath, $callback->($status)
		372
		373	Try to copy the I<file> (directories not supported as either source or
		374	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		375	the C<0> (error) or C<-1> ok.
		376
		377	This is a composite request that it creates the destination file with
		378	mode 0200 and copies the contents of the source file into it using
		379	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		380	uid/gid, in that order.
		381
		382	If an error occurs, the partial destination file will be unlinked, if
		383	possible, except when setting atime, mtime, access mode and uid/gid, where
		384	errors are being ignored.
		385
		386	=cut
		387
		388	sub aio_copy($$;$) {
		389	my ($src, $dst, $cb) = @_;
		390
		391	my $pri = aioreq_pri;
		392	my $grp = aio_group $cb;
		393
		394	aioreq_pri $pri;
		395	add $grp aio_open $src, O_RDONLY, 0, sub {
		396	if (my $src_fh = $_[0]) {
		397	my @stat = stat $src_fh;
		398
		399	aioreq_pri $pri;
		400	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		401	if (my $dst_fh = $_[0]) {
		402	aioreq_pri $pri;
		403	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		404	if ($_[0] == $stat[7]) {
		405	$grp->result (0);
		406	close $src_fh;
		407
		408	# those should not normally block. should. should.
		409	utime $stat[8], $stat[9], $dst;
		410	chmod $stat[2] & 07777, $dst_fh;
		411	chown $stat[4], $stat[5], $dst_fh;
		412	close $dst_fh;
		413	} else {
		414	$grp->result (-1);
		415	close $src_fh;
		416	close $dst_fh;
		417
		418	aioreq $pri;
		419	add $grp aio_unlink $dst;
		420	}
		421	};
		422	} else {
		423	$grp->result (-1);
		424	}
		425	},
		426
		427	} else {
		428	$grp->result (-1);
		429	}
		430	};
		431
		432	$grp
		433	}
		434
		435	=item aio_move $srcpath, $dstpath, $callback->($status)
		436
		437	Try to move the I<file> (directories not supported as either source or
		438	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		439	the C<0> (error) or C<-1> ok.
		440
		441	This is a composite request that tries to rename(2) the file first. If
		442	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		443	that is successful, unlinking the C<$srcpath>.
		444
		445	=cut
		446
		447	sub aio_move($$;$) {
		448	my ($src, $dst, $cb) = @_;
		449
		450	my $pri = aioreq_pri;
		451	my $grp = aio_group $cb;
		452
		453	aioreq_pri $pri;
		454	add $grp aio_rename $src, $dst, sub {
		455	if ($_[0] && $! == EXDEV) {
		456	aioreq_pri $pri;
		457	add $grp aio_copy $src, $dst, sub {
		458	$grp->result ($_[0]);
		459
		460	if (!$_[0]) {
		461	aioreq_pri $pri;
		462	add $grp aio_unlink $src;
		463	}
		464	};
		465	} else {
		466	$grp->result ($_[0]);
		467	}
		468	};
		469
		470	$grp
		471	}
		472
		473	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		474
		475	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		476	efficiently separate the entries of directory C<$path> into two sets of
		477	names, directories you can recurse into (directories), and ones you cannot
		478	recurse into (everything else, including symlinks to directories).
		479
		480	C<aio_scandir> is a composite request that creates of many sub requests_
		481	C<$maxreq> specifies the maximum number of outstanding aio requests that
		482	this function generates. If it is C<< <= 0 >>, then a suitable default
		483	will be chosen (currently 4).
		484
		485	On error, the callback is called without arguments, otherwise it receives
		486	two array-refs with path-relative entry names.
		487
		488	Example:
		489
		490	aio_scandir $dir, 0, sub {
		491	my ($dirs, $nondirs) = @_;
		492	print "real directories: @$dirs\n";
		493	print "everything else: @$nondirs\n";
		494	};
		495
		496	Implementation notes.
		497
		498	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		499
		500	After reading the directory, the modification time, size etc. of the
		501	directory before and after the readdir is checked, and if they match (and
		502	isn't the current time), the link count will be used to decide how many
		503	entries are directories (if >= 2). Otherwise, no knowledge of the number
		504	of subdirectories will be assumed.
		505
		506	Then entries will be sorted into likely directories (everything without
		507	a non-initial dot currently) and likely non-directories (everything
		508	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		509	likely directories first. If that succeeds, it assumes that the entry
		510	is a directory or a symlink to directory (which will be checked
		511	seperately). This is often faster than stat'ing the entry itself because
		512	filesystems might detect the type of the entry without reading the inode
		513	data (e.g. ext2fs filetype feature).
		514
		515	If the known number of directories (link count - 2) has been reached, the
		516	rest of the entries is assumed to be non-directories.
		517
		518	This only works with certainty on POSIX (= UNIX) filesystems, which
		519	fortunately are the vast majority of filesystems around.
		520
		521	It will also likely work on non-POSIX filesystems with reduced efficiency
		522	as those tend to return 0 or 1 as link counts, which disables the
		523	directory counting heuristic.
		524
		525	=cut
		526
		527	sub aio_scandir($$$) {
		528	my ($path, $maxreq, $cb) = @_;
		529
		530	my $pri = aioreq_pri;
		531
		532	my $grp = aio_group $cb;
		533
		534	$maxreq = 4 if $maxreq <= 0;
		535
		536	# stat once
		537	aioreq_pri $pri;
		538	add $grp aio_stat $path, sub {
		539	return $grp->result () if $_[0];
		540	my $now = time;
		541	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		542
		543	# read the directory entries
		544	aioreq_pri $pri;
		545	add $grp aio_readdir $path, sub {
		546	my $entries = shift
		547	or return $grp->result ();
		548
		549	# stat the dir another time
		550	aioreq_pri $pri;
		551	add $grp aio_stat $path, sub {
		552	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		553
		554	my $ndirs;
		555
		556	# take the slow route if anything looks fishy
		557	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		558	$ndirs = -1;
		559	} else {
		560	# if nlink == 2, we are finished
		561	# on non-posix-fs's, we rely on nlink < 2
		562	$ndirs = (stat _)[3] - 2
		563	or return $grp->result ([], $entries);
		564	}
		565
		566	# sort into likely dirs and likely nondirs
		567	# dirs == files without ".", short entries first
		568	$entries = [map $_->[0],
		569	sort { $b->[1] cmp $a->[1] }
		570	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		571	@$entries];
		572
		573	my (@dirs, @nondirs);
		574
		575	my $statgrp = add $grp aio_group sub {
		576	$grp->result (\@dirs, \@nondirs);
		577	};
		578
		579	limit $statgrp $maxreq;
		580	feed $statgrp sub {
		581	return unless @$entries;
		582	my $entry = pop @$entries;
		583
		584	aioreq_pri $pri;
		585	add $statgrp aio_stat "$path/$entry/.", sub {
		586	if ($_[0] < 0) {
		587	push @nondirs, $entry;
		588	} else {
		589	# need to check for real directory
		590	aioreq_pri $pri;
		591	add $statgrp aio_lstat "$path/$entry", sub {
		592	if (-d _) {
		593	push @dirs, $entry;
		594
		595	unless (--$ndirs) {
		596	push @nondirs, @$entries;
		597	feed $statgrp;
		598	}
		599	} else {
		600	push @nondirs, $entry;
		601	}
		602	}
		603	}
		604	};
		605	};
		606	};
		607	};
		608	};
		609
		610	$grp
		611	}
		612
215	=item aio_fsync $fh, $callback	613	=item aio_fsync $fh, $callback->($status)
216		614
217	Asynchronously call fsync on the given filehandle and call the callback	615	Asynchronously call fsync on the given filehandle and call the callback
218	with the fsync result code.	616	with the fsync result code.
219		617
220	=item aio_fdatasync $fh, $callback	618	=item aio_fdatasync $fh, $callback->($status)
221		619
222	Asynchronously call fdatasync on the given filehandle and call the	620	Asynchronously call fdatasync on the given filehandle and call the
223	callback with the fdatasync result code.	621	callback with the fdatasync result code.
		622
		623	If this call isn't available because your OS lacks it or it couldn't be
		624	detected, it will be emulated by calling C<fsync> instead.
		625
		626	=item aio_group $callback->(...)
		627
		628	This is a very special aio request: Instead of doing something, it is a
		629	container for other aio requests, which is useful if you want to bundle
		630	many requests into a single, composite, request with a definite callback
		631	and the ability to cancel the whole request with its subrequests.
		632
		633	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		634	for more info.
		635
		636	Example:
		637
		638	my $grp = aio_group sub {
		639	print "all stats done\n";
		640	};
		641
		642	add $grp
		643	(aio_stat ...),
		644	(aio_stat ...),
		645	...;
		646
		647	=item aio_nop $callback->()
		648
		649	This is a special request - it does nothing in itself and is only used for
		650	side effects, such as when you want to add a dummy request to a group so
		651	that finishing the requests in the group depends on executing the given
		652	code.
		653
		654	While this request does nothing, it still goes through the execution
		655	phase and still requires a worker thread. Thus, the callback will not
		656	be executed immediately but only after other requests in the queue have
		657	entered their execution phase. This can be used to measure request
		658	latency.
		659
		660	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		661
		662	Mainly used for debugging and benchmarking, this aio request puts one of
		663	the request workers to sleep for the given time.
		664
		665	While it is theoretically handy to have simple I/O scheduling requests
		666	like sleep and file handle readable/writable, the overhead this creates is
		667	immense (it blocks a thread for a long time) so do not use this function
		668	except to put your application under artificial I/O pressure.
		669
		670	=back
		671
		672	=head2 IO::AIO::REQ CLASS
		673
		674	All non-aggregate C<aio_*> functions return an object of this class when
		675	called in non-void context.
		676
		677	=over 4
		678
		679	=item cancel $req
		680
		681	Cancels the request, if possible. Has the effect of skipping execution
		682	when entering the B<execute> state and skipping calling the callback when
		683	entering the the B<result> state, but will leave the request otherwise
		684	untouched. That means that requests that currently execute will not be
		685	stopped and resources held by the request will not be freed prematurely.
		686
		687	=item cb $req $callback->(...)
		688
		689	Replace (or simply set) the callback registered to the request.
		690
		691	=back
		692
		693	=head2 IO::AIO::GRP CLASS
		694
		695	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		696	objects of this class, too.
		697
		698	A IO::AIO::GRP object is a special request that can contain multiple other
		699	aio requests.
		700
		701	You create one by calling the C<aio_group> constructing function with a
		702	callback that will be called when all contained requests have entered the
		703	C<done> state:
		704
		705	my $grp = aio_group sub {
		706	print "all requests are done\n";
		707	};
		708
		709	You add requests by calling the C<add> method with one or more
		710	C<IO::AIO::REQ> objects:
		711
		712	$grp->add (aio_unlink "...");
		713
		714	add $grp aio_stat "...", sub {
		715	$_[0] or return $grp->result ("error");
		716
		717	# add another request dynamically, if first succeeded
		718	add $grp aio_open "...", sub {
		719	$grp->result ("ok");
		720	};
		721	};
		722
		723	This makes it very easy to create composite requests (see the source of
		724	C<aio_move> for an application) that work and feel like simple requests.
		725
		726	=over 4
		727
		728	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		729	C<IO::AIO::poll_cb>, just like any other request.
		730
		731	=item * They can be canceled like any other request. Canceling will cancel not
		732	only the request itself, but also all requests it contains.
		733
		734	=item * They can also can also be added to other IO::AIO::GRP objects.
		735
		736	=item * You must not add requests to a group from within the group callback (or
		737	any later time).
		738
		739	=back
		740
		741	Their lifetime, simplified, looks like this: when they are empty, they
		742	will finish very quickly. If they contain only requests that are in the
		743	C<done> state, they will also finish. Otherwise they will continue to
		744	exist.
		745
		746	That means after creating a group you have some time to add requests. And
		747	in the callbacks of those requests, you can add further requests to the
		748	group. And only when all those requests have finished will the the group
		749	itself finish.
		750
		751	=over 4
		752
		753	=item add $grp ...
		754
		755	=item $grp->add (...)
		756
		757	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		758	be added, including other groups, as long as you do not create circular
		759	dependencies.
		760
		761	Returns all its arguments.
		762
		763	=item $grp->cancel_subs
		764
		765	Cancel all subrequests and clears any feeder, but not the group request
		766	itself. Useful when you queued a lot of events but got a result early.
		767
		768	=item $grp->result (...)
		769
		770	Set the result value(s) that will be passed to the group callback when all
		771	subrequests have finished and set thre groups errno to the current value
		772	of errno (just like calling C<errno> without an error number). By default,
		773	no argument will be passed and errno is zero.
		774
		775	=item $grp->errno ([$errno])
		776
		777	Sets the group errno value to C<$errno>, or the current value of errno
		778	when the argument is missing.
		779
		780	Every aio request has an associated errno value that is restored when
		781	the callback is invoked. This method lets you change this value from its
		782	default (0).
		783
		784	Calling C<result> will also set errno, so make sure you either set C<$!>
		785	before the call to C<result>, or call c<errno> after it.
		786
		787	=item feed $grp $callback->($grp)
		788
		789	Sets a feeder/generator on this group: every group can have an attached
		790	generator that generates requests if idle. The idea behind this is that,
		791	although you could just queue as many requests as you want in a group,
		792	this might starve other requests for a potentially long time. For
		793	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		794	requests, delaying any later requests for a long time.
		795
		796	To avoid this, and allow incremental generation of requests, you can
		797	instead a group and set a feeder on it that generates those requests. The
		798	feed callback will be called whenever there are few enough (see C<limit>,
		799	below) requests active in the group itself and is expected to queue more
		800	requests.
		801
		802	The feed callback can queue as many requests as it likes (i.e. C<add> does
		803	not impose any limits).
		804
		805	If the feed does not queue more requests when called, it will be
		806	automatically removed from the group.
		807
		808	If the feed limit is C<0>, it will be set to C<2> automatically.
		809
		810	Example:
		811
		812	# stat all files in @files, but only ever use four aio requests concurrently:
		813
		814	my $grp = aio_group sub { print "finished\n" };
		815	limit $grp 4;
		816	feed $grp sub {
		817	my $file = pop @files
		818	or return;
		819
		820	add $grp aio_stat $file, sub { ... };
		821	};
		822
		823	=item limit $grp $num
		824
		825	Sets the feeder limit for the group: The feeder will be called whenever
		826	the group contains less than this many requests.
		827
		828	Setting the limit to C<0> will pause the feeding process.
		829
		830	=back
		831
		832	=head2 SUPPORT FUNCTIONS
		833
		834	=over 4
		835
		836	=item $fileno = IO::AIO::poll_fileno
		837
		838	Return the I<request result pipe file descriptor>. This filehandle must be
		839	polled for reading by some mechanism outside this module (e.g. Event or
		840	select, see below or the SYNOPSIS). If the pipe becomes readable you have
		841	to call C<poll_cb> to check the results.
		842
		843	See C<poll_cb> for an example.
		844
		845	=item IO::AIO::poll_cb
		846
		847	Process all outstanding events on the result pipe. You have to call this
		848	regularly. Returns the number of events processed. Returns immediately
		849	when no events are outstanding.
		850
		851	If not all requests were processed for whatever reason, the filehandle
		852	will still be ready when C<poll_cb> returns.
		853
		854	Example: Install an Event watcher that automatically calls
		855	IO::AIO::poll_cb with high priority:
		856
		857	Event->io (fd => IO::AIO::poll_fileno,
		858	poll => 'r', async => 1,
		859	cb => \&IO::AIO::poll_cb);
		860
		861	=item IO::AIO::poll_some $max_requests
		862
		863	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests
		864	at a time.
		865
		866	Useful if you want to ensure some level of interactiveness when perl is
		867	not fast enough to process all requests in time.
		868
		869	Example: Install an Event watcher that automatically calls
		870	IO::AIO::poll_some with low priority, to ensure that other parts of the
		871	program get the CPU sometimes even under high AIO load.
		872
		873	Event->io (fd => IO::AIO::poll_fileno,
		874	poll => 'r', nice => 1,
		875	cb => sub { IO::AIO::poll_some 256 });
		876
		877	=item IO::AIO::poll_wait
		878
		879	Wait till the result filehandle becomes ready for reading (simply does a
		880	C<select> on the filehandle. This is useful if you want to synchronously wait
		881	for some requests to finish).
		882
		883	See C<nreqs> for an example.
		884
		885	=item IO::AIO::nreqs
		886
		887	Returns the number of requests currently in the ready, execute or pending
		888	states (i.e. for which their callback has not been invoked yet).
		889
		890	Example: wait till there are no outstanding requests anymore:
		891
		892	IO::AIO::poll_wait, IO::AIO::poll_cb
		893	while IO::AIO::nreqs;
		894
		895	=item IO::AIO::nready
		896
		897	Returns the number of requests currently in the ready state (not yet
		898	executed).
		899
		900	=item IO::AIO::npending
		901
		902	Returns the number of requests currently in the pending state (executed,
		903	but not yet processed by poll_cb).
		904
		905	=item IO::AIO::flush
		906
		907	Wait till all outstanding AIO requests have been handled.
		908
		909	Strictly equivalent to:
		910
		911	IO::AIO::poll_wait, IO::AIO::poll_cb
		912	while IO::AIO::nreqs;
		913
		914	=item IO::AIO::poll
		915
		916	Waits until some requests have been handled.
		917
		918	Strictly equivalent to:
		919
		920	IO::AIO::poll_wait, IO::AIO::poll_cb
		921	if IO::AIO::nreqs;
		922
		923	=item IO::AIO::min_parallel $nthreads
		924
		925	Set the minimum number of AIO threads to C<$nthreads>. The current
		926	default is C<8>, which means eight asynchronous operations can execute
		927	concurrently at any one time (the number of outstanding requests,
		928	however, is unlimited).
		929
		930	IO::AIO starts threads only on demand, when an AIO request is queued and
		931	no free thread exists.
		932
		933	It is recommended to keep the number of threads relatively low, as some
		934	Linux kernel versions will scale negatively with the number of threads
		935	(higher parallelity => MUCH higher latency). With current Linux 2.6
		936	versions, 4-32 threads should be fine.
		937
		938	Under most circumstances you don't need to call this function, as the
		939	module selects a default that is suitable for low to moderate load.
		940
		941	=item IO::AIO::max_parallel $nthreads
		942
		943	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		944	specified number of threads are currently running, this function kills
		945	them. This function blocks until the limit is reached.
		946
		947	While C<$nthreads> are zero, aio requests get queued but not executed
		948	until the number of threads has been increased again.
		949
		950	This module automatically runs C<max_parallel 0> at program end, to ensure
		951	that all threads are killed and that there are no outstanding requests.
		952
		953	Under normal circumstances you don't need to call this function.
		954
		955	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		956
		957	This is a very bad function to use in interactive programs because it
		958	blocks, and a bad way to reduce concurrency because it is inexact: Better
		959	use an C<aio_group> together with a feed callback.
		960
		961	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		962	to queue up more than this number of requests, the next call to the
		963	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		964	function will block until the limit is no longer exceeded.
		965
		966	The default value is very large, so there is no practical limit on the
		967	number of outstanding requests.
		968
		969	You can still queue as many requests as you want. Therefore,
		970	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		971	as a stop gap to shield against fatal memory overflow (with large values).
		972
		973	=back
224		974
225	=cut	975	=cut
226		976
227	# support function to convert a fd into a perl filehandle	977	# support function to convert a fd into a perl filehandle
228	sub _fd2fh {	978	sub _fd2fh {
229	return undef if $_[0] < 0;	979	return undef if $_[0] < 0;
230		980
231	# try to be perl5.6-compatible	981	# try to generate nice filehandles
232	local *AIO_FH;	982	my $sym = "IO::AIO::fd#$_[0]";
233	open AIO_FH, "+<&=$_[0]"	983	local *$sym;
		984
		985	open *$sym, "+<&=$_[0]" # usually works under any unix
		986	or open *$sym, "<&=$_[0]" # cygwin needs this
		987	or open *$sym, ">&=$_[0]" # or this
234	or return undef;	988	or return undef;
235		989
236	*AIO_FH	990	*$sym
237	}	991	}
238		992
239	min_parallel 4;	993	min_parallel 8;
240		994
241	END {	995	END {
242	max_parallel 0;	996	flush;
243	}	997	};
244		998
245	1;	999	1;
246		1000
247	=back	1001	=head2 FORK BEHAVIOUR
248		1002
		1003	This module should do "the right thing" when the process using it forks:
		1004
		1005	Before the fork, IO::AIO enters a quiescent state where no requests
		1006	can be added in other threads and no results will be processed. After
		1007	the fork the parent simply leaves the quiescent state and continues
		1008	request/result processing, while the child frees the request/result queue
		1009	(so that the requests started before the fork will only be handled in the
		1010	parent). Threads will be started on demand until the limit set in the
		1011	parent process has been reached again.
		1012
		1013	In short: the parent will, after a short pause, continue as if fork had
		1014	not been called, while the child will act as if IO::AIO has not been used
		1015	yet.
		1016
		1017	=head2 MEMORY USAGE
		1018
		1019	Per-request usage:
		1020
		1021	Each aio request uses - depending on your architecture - around 100-200
		1022	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1023	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1024	scalars and other data passed into aio requests will also be locked and
		1025	will consume memory till the request has entered the done state.
		1026
		1027	This is now awfully much, so queuing lots of requests is not usually a
		1028	problem.
		1029
		1030	Per-thread usage:
		1031
		1032	In the execution phase, some aio requests require more memory for
		1033	temporary buffers, and each thread requires a stack and other data
		1034	structures (usually around 16k-128k, depending on the OS).
		1035
249	=head1 BUGS	1036	=head1 KNOWN BUGS
250		1037
251	- could be optimized to use more semaphores instead of filehandles.	1038	Known bugs will be fixed in the next release.
252		1039
253	=head1 SEE ALSO	1040	=head1 SEE ALSO
254		1041
255	L<Coro>, L<Linux::AIO>.	1042	L<Coro::AIO>.
256		1043
257	=head1 AUTHOR	1044	=head1 AUTHOR
258		1045
259	Marc Lehmann <schmorp@schmorp.de>	1046	Marc Lehmann <schmorp@schmorp.de>
260	http://home.schmorp.de/	1047	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.2 by root, Sun Jul 10 18:16:49 2005 UTC vs. Revision 1.83 by root, Fri Oct 27 20:11:58 2006 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.2 by root, Sun Jul 10 18:16:49 2005 UTC vs.
Revision 1.83 by root, Fri Oct 27 20:11:58 2006 UTC