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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.52 by root, Sat Oct 21 23:06:04 2006 UTC vs.
Revision 1.115 by root, Mon Sep 24 18:14:00 2007 UTC

…		…
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 {	9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	use IO::AIO 2; # version has aio objects	21	# version 2+ has request and group objects
		22	use IO::AIO 2;
21		23
		24	aioreq_pri 4; # give next request a very high priority
22	my $req = aio_unlink "/tmp/file", sub { };	25	my $req = aio_unlink "/tmp/file", sub { };
23	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
24		27
25	# AnyEvent	28	my $grp = aio_group sub { print "all stats done\n" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration
26	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
27	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });	33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
28		34
29	# Event	35	# Event integration
30	Event->io (fd => IO::AIO::poll_fileno,	36	Event->io (fd => IO::AIO::poll_fileno,
31	poll => 'r',	37	poll => 'r',
32	cb => \&IO::AIO::poll_cb);	38	cb => \&IO::AIO::poll_cb);
33		39
34	# Glib/Gtk2	40	# Glib/Gtk2 integration
35	add_watch Glib::IO IO::AIO::poll_fileno,	41	add_watch Glib::IO IO::AIO::poll_fileno,
36	in => sub { IO::AIO::poll_cb; 1 };	42	in => sub { IO::AIO::poll_cb; 1 };
37		43
38	# Tk	44	# Tk integration
39	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
40	readable => \&IO::AIO::poll_cb);	46	readable => \&IO::AIO::poll_cb);
41		47
42	# Danga::Socket	48	# Danga::Socket integration
43	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
44	\&IO::AIO::poll_cb);	50	\&IO::AIO::poll_cb);
45		51
46
47	=head1 DESCRIPTION	52	=head1 DESCRIPTION
48		53
49	This module implements asynchronous I/O using whatever means your	54	This module implements asynchronous I/O using whatever means your
50	operating system supports.	55	operating system supports.
51		56
		57	Asynchronous means that operations that can normally block your program
		58	(e.g. reading from disk) will be done asynchronously: the operation
		59	will still block, but you can do something else in the meantime. This
		60	is extremely useful for programs that need to stay interactive even
		61	when doing heavy I/O (GUI programs, high performance network servers
		62	etc.), but can also be used to easily do operations in parallel that are
		63	normally done sequentially, e.g. stat'ing many files, which is much faster
		64	on a RAID volume or over NFS when you do a number of stat operations
		65	concurrently.
		66
		67	While most of this works on all types of file descriptors (for
		68	example sockets), using these functions on file descriptors that
		69	support nonblocking operation (again, sockets, pipes etc.) is very
		70	inefficient. Use an event loop for that (such as the L<Event|Event>
		71	module): IO::AIO will naturally fit into such an event loop itself.
		72
52	Currently, a number of threads are started that execute your read/writes	73	In this version, a number of threads are started that execute your
53	and signal their completion. You don't need thread support in your libc or	74	requests and signal their completion. You don't need thread support
54	perl, and the threads created by this module will not be visible to the	75	in perl, and the threads created by this module will not be visible
55	pthreads library. In the future, this module might make use of the native	76	to perl. In the future, this module might make use of the native aio
56	aio functions available on many operating systems. However, they are often	77	functions available on many operating systems. However, they are often
57	not well-supported (Linux doesn't allow them on normal files currently,	78	not well-supported or restricted (GNU/Linux doesn't allow them on normal
58	for example), and they would only support aio_read and aio_write, so the	79	files currently, for example), and they would only support aio_read and
59	remaining functionality would have to be implemented using threads anyway.	80	aio_write, so the remaining functionality would have to be implemented
		81	using threads anyway.
60		82
61	Although the module will work with in the presence of other threads, it is	83	Although the module will work in the presence of other (Perl-) threads,
62	currently not reentrant, so use appropriate locking yourself, always call	84	it is currently not reentrant in any way, so use appropriate locking
63	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	85	yourself, always call C<poll_cb> from within the same thread, or never
64	C<aio_> functions) recursively.	86	call C<poll_cb> (or other C<aio_> functions) recursively.
		87
		88	=head2 EXAMPLE
		89
		90	This is a simple example that uses the Event module and loads
		91	F</etc/passwd> asynchronously:
		92
		93	use Fcntl;
		94	use Event;
		95	use IO::AIO;
		96
		97	# register the IO::AIO callback with Event
		98	Event->io (fd => IO::AIO::poll_fileno,
		99	poll => 'r',
		100	cb => \&IO::AIO::poll_cb);
		101
		102	# queue the request to open /etc/passwd
		103	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		104	my $fh = shift
		105	or die "error while opening: $!";
		106
		107	# stat'ing filehandles is generally non-blocking
		108	my $size = -s $fh;
		109
		110	# queue a request to read the file
		111	my $contents;
		112	aio_read $fh, 0, $size, $contents, 0, sub {
		113	$_[0] == $size
		114	or die "short read: $!";
		115
		116	close $fh;
		117
		118	# file contents now in $contents
		119	print $contents;
		120
		121	# exit event loop and program
		122	Event::unloop;
		123	};
		124	};
		125
		126	# possibly queue up other requests, or open GUI windows,
		127	# check for sockets etc. etc.
		128
		129	# process events as long as there are some:
		130	Event::loop;
		131
		132	=head1 REQUEST ANATOMY AND LIFETIME
		133
		134	Every C<aio_*> function creates a request. which is a C data structure not
		135	directly visible to Perl.
		136
		137	If called in non-void context, every request function returns a Perl
		138	object representing the request. In void context, nothing is returned,
		139	which saves a bit of memory.
		140
		141	The perl object is a fairly standard ref-to-hash object. The hash contents
		142	are not used by IO::AIO so you are free to store anything you like in it.
		143
		144	During their existance, aio requests travel through the following states,
		145	in order:
		146
		147	=over 4
		148
		149	=item ready
		150
		151	Immediately after a request is created it is put into the ready state,
		152	waiting for a thread to execute it.
		153
		154	=item execute
		155
		156	A thread has accepted the request for processing and is currently
		157	executing it (e.g. blocking in read).
		158
		159	=item pending
		160
		161	The request has been executed and is waiting for result processing.
		162
		163	While request submission and execution is fully asynchronous, result
		164	processing is not and relies on the perl interpreter calling C<poll_cb>
		165	(or another function with the same effect).
		166
		167	=item result
		168
		169	The request results are processed synchronously by C<poll_cb>.
		170
		171	The C<poll_cb> function will process all outstanding aio requests by
		172	calling their callbacks, freeing memory associated with them and managing
		173	any groups they are contained in.
		174
		175	=item done
		176
		177	Request has reached the end of its lifetime and holds no resources anymore
		178	(except possibly for the Perl object, but its connection to the actual
		179	aio request is severed and calling its methods will either do nothing or
		180	result in a runtime error).
		181
		182	=back
65		183
66	=cut	184	=cut
67		185
68	package IO::AIO;	186	package IO::AIO;
69		187
…		…
71	use strict 'vars';	189	use strict 'vars';
72		190
73	use base 'Exporter';	191	use base 'Exporter';
74		192
75	BEGIN {	193	BEGIN {
76	our $VERSION = '1.8';	194	our $VERSION = '2.41';
77		195
78	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	196	our @AIO_REQ = 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	197	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);	198	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
81	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	199	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
		200	aio_chown aio_chmod aio_utime aio_truncate);
		201	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		202	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		203	min_parallel max_parallel max_idle
		204	nreqs nready npending nthreads
		205	max_poll_time max_poll_reqs);
		206
		207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
82		208
83	require XSLoader;	209	require XSLoader;
84	XSLoader::load ("IO::AIO", $VERSION);	210	XSLoader::load ("IO::AIO", $VERSION);
85	}	211	}
86		212
87	=head1 FUNCTIONS	213	=head1 FUNCTIONS
88		214
89	=head2 AIO FUNCTIONS	215	=head2 AIO REQUEST FUNCTIONS
90		216
91	All the C<aio_*> calls are more or less thin wrappers around the syscall	217	All the C<aio_*> calls are more or less thin wrappers around the syscall
92	with the same name (sans C<aio_>). The arguments are similar or identical,	218	with the same name (sans C<aio_>). The arguments are similar or identical,
93	and they all accept an additional (and optional) C<$callback> argument	219	and they all accept an additional (and optional) C<$callback> argument
94	which must be a code reference. This code reference will get called with	220	which must be a code reference. This code reference will get called with
…		…
97	syscall has been executed asynchronously.	223	syscall has been executed asynchronously.
98		224
99	All functions expecting a filehandle keep a copy of the filehandle	225	All functions expecting a filehandle keep a copy of the filehandle
100	internally until the request has finished.	226	internally until the request has finished.
101		227
102	All non-composite requests (requests that are not broken down into
103	multiple requests) return objects of type L<IO::AIO::REQ> that allow	228	All functions return request objects of type L<IO::AIO::REQ> that allow
104	further manipulation of running requests.	229	further manipulation of those requests while they are in-flight.
105		230
106	The pathnames you pass to these routines I<must> be absolute and	231	The pathnames you pass to these routines I<must> be absolute and
107	encoded in byte form. The reason for the former is that at the time the	232	encoded as octets. The reason for the former is that at the time the
108	request is being executed, the current working directory could have	233	request is being executed, the current working directory could have
109	changed. Alternatively, you can make sure that you never change the	234	changed. Alternatively, you can make sure that you never change the
110	current working directory.	235	current working directory anywhere in the program and then use relative
		236	paths.
111		237
112	To encode pathnames to byte form, either make sure you either: a)	238	To encode pathnames as octets, either make sure you either: a) always pass
113	always pass in filenames you got from outside (command line, readdir	239	in filenames you got from outside (command line, readdir etc.) without
114	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	240	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
115	your pathnames to the locale (or other) encoding in effect in the user	241	your pathnames to the locale (or other) encoding in effect in the user
116	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	242	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
117	use something else.	243	use something else to ensure your scalar has the correct contents.
		244
		245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		246	handles correctly wether it is set or not.
118		247
119	=over 4	248	=over 4
		249
		250	=item $prev_pri = aioreq_pri [$pri]
		251
		252	Returns the priority value that would be used for the next request and, if
		253	C<$pri> is given, sets the priority for the next aio request.
		254
		255	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		256	and C<4>, respectively. Requests with higher priority will be serviced
		257	first.
		258
		259	The priority will be reset to C<0> after each call to one of the C<aio_*>
		260	functions.
		261
		262	Example: open a file with low priority, then read something from it with
		263	higher priority so the read request is serviced before other low priority
		264	open requests (potentially spamming the cache):
		265
		266	aioreq_pri -3;
		267	aio_open ..., sub {
		268	return unless $_[0];
		269
		270	aioreq_pri -2;
		271	aio_read $_[0], ..., sub {
		272	...
		273	};
		274	};
		275
		276
		277	=item aioreq_nice $pri_adjust
		278
		279	Similar to C<aioreq_pri>, but subtracts the given value from the current
		280	priority, so the effect is cumulative.
		281
120		282
121	=item aio_open $pathname, $flags, $mode, $callback->($fh)	283	=item aio_open $pathname, $flags, $mode, $callback->($fh)
122		284
123	Asynchronously open or create a file and call the callback with a newly	285	Asynchronously open or create a file and call the callback with a newly
124	created filehandle for the file.	286	created filehandle for the file.
…		…
130	list. They are the same as used by C<sysopen>.	292	list. They are the same as used by C<sysopen>.
131		293
132	Likewise, C<$mode> specifies the mode of the newly created file, if it	294	Likewise, C<$mode> specifies the mode of the newly created file, if it
133	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	295	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
134	except that it is mandatory (i.e. use C<0> if you don't create new files,	296	except that it is mandatory (i.e. use C<0> if you don't create new files,
135	and C<0666> or C<0777> if you do).	297	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		298	by the umask in effect then the request is being executed, so better never
		299	change the umask.
136		300
137	Example:	301	Example:
138		302
139	aio_open "/etc/passwd", O_RDONLY, 0, sub {	303	aio_open "/etc/passwd", O_RDONLY, 0, sub {
140	if ($_[0]) {	304	if ($_[0]) {
…		…
143	} else {	307	} else {
144	die "open failed: $!\n";	308	die "open failed: $!\n";
145	}	309	}
146	};	310	};
147		311
		312
148	=item aio_close $fh, $callback->($status)	313	=item aio_close $fh, $callback->($status)
149		314
150	Asynchronously close a file and call the callback with the result	315	Asynchronously close a file and call the callback with the result
151	code. I<WARNING:> although accepted, you should not pass in a perl	316	code. I<WARNING:> although accepted, you should not pass in a perl
152	filehandle here, as perl will likely close the file descriptor another	317	filehandle here, as perl will likely close the file descriptor another
…		…
154	C<close> or just let filehandles go out of scope.	319	C<close> or just let filehandles go out of scope.
155		320
156	This is supposed to be a bug in the API, so that might change. It's	321	This is supposed to be a bug in the API, so that might change. It's
157	therefore best to avoid this function.	322	therefore best to avoid this function.
158		323
		324
159	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	325	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
160		326
161	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	327	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
162		328
163	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	329	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
164	into the scalar given by C<data> and offset C<dataoffset> and calls the	330	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
165	callback without the actual number of bytes read (or -1 on error, just	331	callback without the actual number of bytes read (or -1 on error, just
166	like the syscall).	332	like the syscall).
167		333
		334	If C<$offset> is undefined, then the current file descriptor offset will
		335	be used (and updated), otherwise the file descriptor offset will not be
		336	changed by these calls.
		337
		338	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		339
		340	If C<$dataoffset> is less than zero, it will be counted from the end of
		341	C<$data>.
		342
168	The C<$data> scalar I<MUST NOT> be modified in any way while the request	343	The C<$data> scalar I<MUST NOT> be modified in any way while the request
169	is outstanding. Modifying it can result in segfaults or WW3 (if the	344	is outstanding. Modifying it can result in segfaults or World War III (if
170	necessary/optional hardware is installed).	345	the necessary/optional hardware is installed).
171		346
172	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	347	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
173	offset C<0> within the scalar:	348	offset C<0> within the scalar:
174		349
175	aio_read $fh, 7, 15, $buffer, 0, sub {	350	aio_read $fh, 7, 15, $buffer, 0, sub {
176	$_[0] > 0 or die "read error: $!";	351	$_[0] > 0 or die "read error: $!";
177	print "read $_[0] bytes: <$buffer>\n";	352	print "read $_[0] bytes: <$buffer>\n";
178	};	353	};
179		354
180	=item aio_move $srcpath, $dstpath, $callback->($status)
181
182	Try to move the I<file> (directories not supported as either source or
183	destination) from C<$srcpath> to C<$dstpath> and call the callback with
184	the C<0> (error) or C<-1> ok.
185
186	This is a composite request that tries to rename(2) the file first. If
187	rename files with C<EXDEV>, it creates the destination file with mode 0200
188	and copies the contents of the source file into it using C<aio_sendfile>,
189	followed by restoring atime, mtime, access mode and uid/gid, in that
190	order, and unlinking the C<$srcpath>.
191
192	If an error occurs, the partial destination file will be unlinked, if
193	possible, except when setting atime, mtime, access mode and uid/gid, where
194	errors are being ignored.
195
196	=cut
197
198	sub aio_move($$$) {
199	my ($src, $dst, $cb) = @_;
200
201	aio_rename $src, $dst, sub {
202	if ($_[0] && $! == EXDEV) {
203	aio_open $src, O_RDONLY, 0, sub {
204	if (my $src_fh = $_[0]) {
205	my @stat = stat $src_fh;
206
207	aio_open $dst, O_WRONLY, 0200, sub {
208	if (my $dst_fh = $_[0]) {
209	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
210	close $src_fh;
211
212	if ($_[0] == $stat[7]) {
213	utime $stat[8], $stat[9], $dst;
214	chmod $stat[2] & 07777, $dst_fh;
215	chown $stat[4], $stat[5], $dst_fh;
216	close $dst_fh;
217
218	aio_unlink $src, sub {
219	$cb->($_[0]);
220	};
221	} else {
222	my $errno = $!;
223	aio_unlink $dst, sub {
224	$! = $errno;
225	$cb->(-1);
226	};
227	}
228	};
229	} else {
230	$cb->(-1);
231	}
232	},
233
234	} else {
235	$cb->(-1);
236	}
237	};
238	} else {
239	$cb->($_[0]);
240	}
241	};
242	}
243		355
244	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	356	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
245		357
246	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	358	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
247	reading at byte offset C<$in_offset>, and starts writing at the current	359	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
261	C<$in_fh> than are written, and there is no way to find out how many	373	C<$in_fh> than are written, and there is no way to find out how many
262	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	374	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
263	provides the number of bytes written to C<$out_fh>. Only if the result	375	provides the number of bytes written to C<$out_fh>. Only if the result
264	value equals C<$length> one can assume that C<$length> bytes have been	376	value equals C<$length> one can assume that C<$length> bytes have been
265	read.	377	read.
		378
266		379
267	=item aio_readahead $fh,$offset,$length, $callback->($retval)	380	=item aio_readahead $fh,$offset,$length, $callback->($retval)
268		381
269	C<aio_readahead> populates the page cache with data from a file so that	382	C<aio_readahead> populates the page cache with data from a file so that
270	subsequent reads from that file will not block on disk I/O. The C<$offset>	383	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
276	file. The current file offset of the file is left unchanged.	389	file. The current file offset of the file is left unchanged.
277		390
278	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	391	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
279	emulated by simply reading the data, which would have a similar effect.	392	emulated by simply reading the data, which would have a similar effect.
280		393
		394
281	=item aio_stat $fh_or_path, $callback->($status)	395	=item aio_stat $fh_or_path, $callback->($status)
282		396
283	=item aio_lstat $fh, $callback->($status)	397	=item aio_lstat $fh, $callback->($status)
284		398
285	Works like perl's C<stat> or C<lstat> in void context. The callback will	399	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
298	aio_stat "/etc/passwd", sub {	412	aio_stat "/etc/passwd", sub {
299	$_[0] and die "stat failed: $!";	413	$_[0] and die "stat failed: $!";
300	print "size is ", -s _, "\n";	414	print "size is ", -s _, "\n";
301	};	415	};
302		416
		417
		418	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		419
		420	Works like perl's C<utime> function (including the special case of $atime
		421	and $mtime being undef). Fractional times are supported if the underlying
		422	syscalls support them.
		423
		424	When called with a pathname, uses utimes(2) if available, otherwise
		425	utime(2). If called on a file descriptor, uses futimes(2) if available,
		426	otherwise returns ENOSYS, so this is not portable.
		427
		428	Examples:
		429
		430	# set atime and mtime to current time (basically touch(1)):
		431	aio_utime "path", undef, undef;
		432	# set atime to current time and mtime to beginning of the epoch:
		433	aio_utime "path", time, undef; # undef==0
		434
		435
		436	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		437
		438	Works like perl's C<chown> function, except that C<undef> for either $uid
		439	or $gid is being interpreted as "do not change" (but -1 can also be used).
		440
		441	Examples:
		442
		443	# same as "chown root path" in the shell:
		444	aio_chown "path", 0, -1;
		445	# same as above:
		446	aio_chown "path", 0, undef;
		447
		448
		449	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		450
		451	Works like truncate(2) or ftruncate(2).
		452
		453
		454	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		455
		456	Works like perl's C<chmod> function.
		457
		458
303	=item aio_unlink $pathname, $callback->($status)	459	=item aio_unlink $pathname, $callback->($status)
304		460
305	Asynchronously unlink (delete) a file and call the callback with the	461	Asynchronously unlink (delete) a file and call the callback with the
306	result code.	462	result code.
307		463
		464
		465	=item aio_mknod $path, $mode, $dev, $callback->($status)
		466
		467	[EXPERIMENTAL]
		468
		469	Asynchronously create a device node (or fifo). See mknod(2).
		470
		471	The only (POSIX-) portable way of calling this function is:
		472
		473	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		474
		475
308	=item aio_link $srcpath, $dstpath, $callback->($status)	476	=item aio_link $srcpath, $dstpath, $callback->($status)
309		477
310	Asynchronously create a new link to the existing object at C<$srcpath> at	478	Asynchronously create a new link to the existing object at C<$srcpath> at
311	the path C<$dstpath> and call the callback with the result code.	479	the path C<$dstpath> and call the callback with the result code.
312		480
		481
313	=item aio_symlink $srcpath, $dstpath, $callback->($status)	482	=item aio_symlink $srcpath, $dstpath, $callback->($status)
314		483
315	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	484	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
316	the path C<$dstpath> and call the callback with the result code.	485	the path C<$dstpath> and call the callback with the result code.
317		486
		487
		488	=item aio_readlink $path, $callback->($link)
		489
		490	Asynchronously read the symlink specified by C<$path> and pass it to
		491	the callback. If an error occurs, nothing or undef gets passed to the
		492	callback.
		493
		494
318	=item aio_rename $srcpath, $dstpath, $callback->($status)	495	=item aio_rename $srcpath, $dstpath, $callback->($status)
319		496
320	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	497	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
321	rename(2) and call the callback with the result code.	498	rename(2) and call the callback with the result code.
322		499
		500
		501	=item aio_mkdir $pathname, $mode, $callback->($status)
		502
		503	Asynchronously mkdir (create) a directory and call the callback with
		504	the result code. C<$mode> will be modified by the umask at the time the
		505	request is executed, so do not change your umask.
		506
		507
323	=item aio_rmdir $pathname, $callback->($status)	508	=item aio_rmdir $pathname, $callback->($status)
324		509
325	Asynchronously rmdir (delete) a directory and call the callback with the	510	Asynchronously rmdir (delete) a directory and call the callback with the
326	result code.	511	result code.
		512
327		513
328	=item aio_readdir $pathname, $callback->($entries)	514	=item aio_readdir $pathname, $callback->($entries)
329		515
330	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	516	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
331	directory (i.e. opendir + readdir + closedir). The entries will not be	517	directory (i.e. opendir + readdir + closedir). The entries will not be
332	sorted, and will B<NOT> include the C<.> and C<..> entries.	518	sorted, and will B<NOT> include the C<.> and C<..> entries.
333		519
334	The callback a single argument which is either C<undef> or an array-ref	520	The callback a single argument which is either C<undef> or an array-ref
335	with the filenames.	521	with the filenames.
336		522
		523
		524	=item aio_load $path, $data, $callback->($status)
		525
		526	This is a composite request that tries to fully load the given file into
		527	memory. Status is the same as with aio_read.
		528
		529	=cut
		530
		531	sub aio_load($$;$) {
		532	aio_block {
		533	my ($path, undef, $cb) = @_;
		534	my $data = \$_[1];
		535
		536	my $pri = aioreq_pri;
		537	my $grp = aio_group $cb;
		538
		539	aioreq_pri $pri;
		540	add $grp aio_open $path, O_RDONLY, 0, sub {
		541	my $fh = shift
		542	or return $grp->result (-1);
		543
		544	aioreq_pri $pri;
		545	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		546	$grp->result ($_[0]);
		547	};
		548	};
		549
		550	$grp
		551	}
		552	}
		553
		554	=item aio_copy $srcpath, $dstpath, $callback->($status)
		555
		556	Try to copy the I<file> (directories not supported as either source or
		557	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		558	the C<0> (error) or C<-1> ok.
		559
		560	This is a composite request that it creates the destination file with
		561	mode 0200 and copies the contents of the source file into it using
		562	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		563	uid/gid, in that order.
		564
		565	If an error occurs, the partial destination file will be unlinked, if
		566	possible, except when setting atime, mtime, access mode and uid/gid, where
		567	errors are being ignored.
		568
		569	=cut
		570
		571	sub aio_copy($$;$) {
		572	aio_block {
		573	my ($src, $dst, $cb) = @_;
		574
		575	my $pri = aioreq_pri;
		576	my $grp = aio_group $cb;
		577
		578	aioreq_pri $pri;
		579	add $grp aio_open $src, O_RDONLY, 0, sub {
		580	if (my $src_fh = $_[0]) {
		581	my @stat = stat $src_fh;
		582
		583	aioreq_pri $pri;
		584	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		585	if (my $dst_fh = $_[0]) {
		586	aioreq_pri $pri;
		587	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		588	if ($_[0] == $stat[7]) {
		589	$grp->result (0);
		590	close $src_fh;
		591
		592	# those should not normally block. should. should.
		593	utime $stat[8], $stat[9], $dst;
		594	chmod $stat[2] & 07777, $dst_fh;
		595	chown $stat[4], $stat[5], $dst_fh;
		596	close $dst_fh;
		597	} else {
		598	$grp->result (-1);
		599	close $src_fh;
		600	close $dst_fh;
		601
		602	aioreq $pri;
		603	add $grp aio_unlink $dst;
		604	}
		605	};
		606	} else {
		607	$grp->result (-1);
		608	}
		609	},
		610
		611	} else {
		612	$grp->result (-1);
		613	}
		614	};
		615
		616	$grp
		617	}
		618	}
		619
		620	=item aio_move $srcpath, $dstpath, $callback->($status)
		621
		622	Try to move the I<file> (directories not supported as either source or
		623	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		624	the C<0> (error) or C<-1> ok.
		625
		626	This is a composite request that tries to rename(2) the file first. If
		627	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		628	that is successful, unlinking the C<$srcpath>.
		629
		630	=cut
		631
		632	sub aio_move($$;$) {
		633	aio_block {
		634	my ($src, $dst, $cb) = @_;
		635
		636	my $pri = aioreq_pri;
		637	my $grp = aio_group $cb;
		638
		639	aioreq_pri $pri;
		640	add $grp aio_rename $src, $dst, sub {
		641	if ($_[0] && $! == EXDEV) {
		642	aioreq_pri $pri;
		643	add $grp aio_copy $src, $dst, sub {
		644	$grp->result ($_[0]);
		645
		646	if (!$_[0]) {
		647	aioreq_pri $pri;
		648	add $grp aio_unlink $src;
		649	}
		650	};
		651	} else {
		652	$grp->result ($_[0]);
		653	}
		654	};
		655
		656	$grp
		657	}
		658	}
		659
337	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	660	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
338		661
339	Scans a directory (similar to C<aio_readdir>) but additionally tries to	662	Scans a directory (similar to C<aio_readdir>) but additionally tries to
340	separate the entries of directory C<$path> into two sets of names, ones	663	efficiently separate the entries of directory C<$path> into two sets of
341	you can recurse into (directories or links to them), and ones you cannot	664	names, directories you can recurse into (directories), and ones you cannot
342	recurse into (everything else).	665	recurse into (everything else, including symlinks to directories).
343		666
344	C<aio_scandir> is a composite request that consists of many sub	667	C<aio_scandir> is a composite request that creates of many sub requests_
345	requests. C<$maxreq> specifies the maximum number of outstanding aio	668	C<$maxreq> specifies the maximum number of outstanding aio requests that
346	requests that this function generates. If it is C<< <= 0 >>, then a	669	this function generates. If it is C<< <= 0 >>, then a suitable default
347	suitable default will be chosen (currently 8).	670	will be chosen (currently 4).
348		671
349	On error, the callback is called without arguments, otherwise it receives	672	On error, the callback is called without arguments, otherwise it receives
350	two array-refs with path-relative entry names.	673	two array-refs with path-relative entry names.
351		674
352	Example:	675	Example:
…		…
386	as those tend to return 0 or 1 as link counts, which disables the	709	as those tend to return 0 or 1 as link counts, which disables the
387	directory counting heuristic.	710	directory counting heuristic.
388		711
389	=cut	712	=cut
390		713
391	sub aio_scandir($$$) {	714	sub aio_scandir($$;$) {
		715	aio_block {
392	my ($path, $maxreq, $cb) = @_;	716	my ($path, $maxreq, $cb) = @_;
393		717
		718	my $pri = aioreq_pri;
		719
		720	my $grp = aio_group $cb;
		721
394	$maxreq = 8 if $maxreq <= 0;	722	$maxreq = 4 if $maxreq <= 0;
395		723
396	# stat once	724	# stat once
		725	aioreq_pri $pri;
397	aio_stat $path, sub {	726	add $grp aio_stat $path, sub {
398	return $cb->() if $_[0];	727	return $grp->result () if $_[0];
399	my $now = time;	728	my $now = time;
400	my $hash1 = join ":", (stat _)[0,1,3,7,9];	729	my $hash1 = join ":", (stat _)[0,1,3,7,9];
401		730
402	# read the directory entries	731	# read the directory entries
		732	aioreq_pri $pri;
403	aio_readdir $path, sub {	733	add $grp aio_readdir $path, sub {
404	my $entries = shift	734	my $entries = shift
405	or return $cb->();	735	or return $grp->result ();
406		736
407	# stat the dir another time	737	# stat the dir another time
		738	aioreq_pri $pri;
408	aio_stat $path, sub {	739	add $grp aio_stat $path, sub {
409	my $hash2 = join ":", (stat _)[0,1,3,7,9];	740	my $hash2 = join ":", (stat _)[0,1,3,7,9];
410		741
411	my $ndirs;	742	my $ndirs;
412		743
413	# take the slow route if anything looks fishy	744	# take the slow route if anything looks fishy
414	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	745	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
415	$ndirs = -1;	746	$ndirs = -1;
416	} else {	747	} else {
417	# if nlink == 2, we are finished	748	# if nlink == 2, we are finished
418	# on non-posix-fs's, we rely on nlink < 2	749	# on non-posix-fs's, we rely on nlink < 2
419	$ndirs = (stat _)[3] - 2	750	$ndirs = (stat _)[3] - 2
420	or return $cb->([], $entries);	751	or return $grp->result ([], $entries);
421	}
422
423	# sort into likely dirs and likely nondirs
424	# dirs == files without ".", short entries first
425	$entries = [map $_->[0],
426	sort { $b->[1] cmp $a->[1] }
427	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
428	@$entries];
429
430	my (@dirs, @nondirs);
431
432	my ($statcb, $schedcb);
433	my $nreq = 0;
434
435	$schedcb = sub {
436	if (@$entries) {
437	if ($nreq < $maxreq) {
438	my $ent = pop @$entries;
439	$nreq++;
440	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
441	}
442	} elsif (!$nreq) {
443	# finished
444	undef $statcb;
445	undef $schedcb;
446	$cb->(\@dirs, \@nondirs) if $cb;
447	undef $cb;
448	}	752	}
		753
		754	# sort into likely dirs and likely nondirs
		755	# dirs == files without ".", short entries first
		756	$entries = [map $_->[0],
		757	sort { $b->[1] cmp $a->[1] }
		758	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		759	@$entries];
		760
		761	my (@dirs, @nondirs);
		762
		763	my $statgrp = add $grp aio_group sub {
		764	$grp->result (\@dirs, \@nondirs);
		765	};
		766
		767	limit $statgrp $maxreq;
		768	feed $statgrp sub {
		769	return unless @$entries;
		770	my $entry = pop @$entries;
		771
		772	aioreq_pri $pri;
		773	add $statgrp aio_stat "$path/$entry/.", sub {
		774	if ($_[0] < 0) {
		775	push @nondirs, $entry;
		776	} else {
		777	# need to check for real directory
		778	aioreq_pri $pri;
		779	add $statgrp aio_lstat "$path/$entry", sub {
		780	if (-d _) {
		781	push @dirs, $entry;
		782
		783	unless (--$ndirs) {
		784	push @nondirs, @$entries;
		785	feed $statgrp;
		786	}
		787	} else {
		788	push @nondirs, $entry;
		789	}
		790	}
		791	}
		792	};
		793	};
449	};	794	};
450	$statcb = sub {
451	my ($status, $entry) = @_;
452
453	if ($status < 0) {
454	$nreq--;
455	push @nondirs, $entry;
456	&$schedcb;
457	} else {
458	# need to check for real directory
459	aio_lstat "$path/$entry", sub {
460	$nreq--;
461
462	if (-d _) {
463	push @dirs, $entry;
464
465	if (!--$ndirs) {
466	push @nondirs, @$entries;
467	$entries = [];
468	}
469	} else {
470	push @nondirs, $entry;
471	}
472
473	&$schedcb;
474	}
475	}
476	};
477
478	&$schedcb while @$entries && $nreq < $maxreq;
479	};	795	};
480	};	796	};
		797
		798	$grp
481	};	799	}
		800	}
		801
		802	=item aio_rmtree $path, $callback->($status)
		803
		804	Delete a directory tree starting (and including) C<$path>, return the
		805	status of the final C<rmdir> only. This is a composite request that
		806	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		807	everything else.
		808
		809	=cut
		810
		811	sub aio_rmtree;
		812	sub aio_rmtree($;$) {
		813	aio_block {
		814	my ($path, $cb) = @_;
		815
		816	my $pri = aioreq_pri;
		817	my $grp = aio_group $cb;
		818
		819	aioreq_pri $pri;
		820	add $grp aio_scandir $path, 0, sub {
		821	my ($dirs, $nondirs) = @_;
		822
		823	my $dirgrp = aio_group sub {
		824	add $grp aio_rmdir $path, sub {
		825	$grp->result ($_[0]);
		826	};
		827	};
		828
		829	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		830	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		831
		832	add $grp $dirgrp;
		833	};
		834
		835	$grp
		836	}
482	}	837	}
483		838
484	=item aio_fsync $fh, $callback->($status)	839	=item aio_fsync $fh, $callback->($status)
485		840
486	Asynchronously call fsync on the given filehandle and call the callback	841	Asynchronously call fsync on the given filehandle and call the callback
…		…
492	callback with the fdatasync result code.	847	callback with the fdatasync result code.
493		848
494	If this call isn't available because your OS lacks it or it couldn't be	849	If this call isn't available because your OS lacks it or it couldn't be
495	detected, it will be emulated by calling C<fsync> instead.	850	detected, it will be emulated by calling C<fsync> instead.
496		851
		852	=item aio_group $callback->(...)
		853
		854	This is a very special aio request: Instead of doing something, it is a
		855	container for other aio requests, which is useful if you want to bundle
		856	many requests into a single, composite, request with a definite callback
		857	and the ability to cancel the whole request with its subrequests.
		858
		859	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		860	for more info.
		861
		862	Example:
		863
		864	my $grp = aio_group sub {
		865	print "all stats done\n";
		866	};
		867
		868	add $grp
		869	(aio_stat ...),
		870	(aio_stat ...),
		871	...;
		872
		873	=item aio_nop $callback->()
		874
		875	This is a special request - it does nothing in itself and is only used for
		876	side effects, such as when you want to add a dummy request to a group so
		877	that finishing the requests in the group depends on executing the given
		878	code.
		879
		880	While this request does nothing, it still goes through the execution
		881	phase and still requires a worker thread. Thus, the callback will not
		882	be executed immediately but only after other requests in the queue have
		883	entered their execution phase. This can be used to measure request
		884	latency.
		885
		886	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		887
		888	Mainly used for debugging and benchmarking, this aio request puts one of
		889	the request workers to sleep for the given time.
		890
		891	While it is theoretically handy to have simple I/O scheduling requests
		892	like sleep and file handle readable/writable, the overhead this creates is
		893	immense (it blocks a thread for a long time) so do not use this function
		894	except to put your application under artificial I/O pressure.
		895
497	=back	896	=back
498		897
499	=head2 IO::AIO::CB CLASS	898	=head2 IO::AIO::REQ CLASS
500		899
501	All non-aggregate C<aio_*> functions return an object of this class when	900	All non-aggregate C<aio_*> functions return an object of this class when
502	called in non-void context.	901	called in non-void context.
503		902
504	A request always moves through the following five states in its lifetime,
505	in order: B<ready> (request has been created, but has not been executed
506	yet), B<execute> (request is currently being executed), B<pending>
507	(request has been executed but callback has not been called yet),
508	B<result> (results are being processed synchronously, includes calling the
509	callback) and B<done> (request has reached the end of its lifetime and
510	holds no resources anymore).
511
512	=over 4	903	=over 4
513		904
514	=item $req->cancel	905	=item cancel $req
515		906
516	Cancels the request, if possible. Has the effect of skipping execution	907	Cancels the request, if possible. Has the effect of skipping execution
517	when entering the B<execute> state and skipping calling the callback when	908	when entering the B<execute> state and skipping calling the callback when
518	entering the the B<result> state, but will leave the request otherwise	909	entering the the B<result> state, but will leave the request otherwise
519	untouched. That means that requests that currently execute will not be	910	untouched. That means that requests that currently execute will not be
520	stopped and resources held by the request will not be freed prematurely.	911	stopped and resources held by the request will not be freed prematurely.
521		912
		913	=item cb $req $callback->(...)
		914
		915	Replace (or simply set) the callback registered to the request.
		916
522	=back	917	=back
523		918
		919	=head2 IO::AIO::GRP CLASS
		920
		921	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		922	objects of this class, too.
		923
		924	A IO::AIO::GRP object is a special request that can contain multiple other
		925	aio requests.
		926
		927	You create one by calling the C<aio_group> constructing function with a
		928	callback that will be called when all contained requests have entered the
		929	C<done> state:
		930
		931	my $grp = aio_group sub {
		932	print "all requests are done\n";
		933	};
		934
		935	You add requests by calling the C<add> method with one or more
		936	C<IO::AIO::REQ> objects:
		937
		938	$grp->add (aio_unlink "...");
		939
		940	add $grp aio_stat "...", sub {
		941	$_[0] or return $grp->result ("error");
		942
		943	# add another request dynamically, if first succeeded
		944	add $grp aio_open "...", sub {
		945	$grp->result ("ok");
		946	};
		947	};
		948
		949	This makes it very easy to create composite requests (see the source of
		950	C<aio_move> for an application) that work and feel like simple requests.
		951
		952	=over 4
		953
		954	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		955	C<IO::AIO::poll_cb>, just like any other request.
		956
		957	=item * They can be canceled like any other request. Canceling will cancel not
		958	only the request itself, but also all requests it contains.
		959
		960	=item * They can also can also be added to other IO::AIO::GRP objects.
		961
		962	=item * You must not add requests to a group from within the group callback (or
		963	any later time).
		964
		965	=back
		966
		967	Their lifetime, simplified, looks like this: when they are empty, they
		968	will finish very quickly. If they contain only requests that are in the
		969	C<done> state, they will also finish. Otherwise they will continue to
		970	exist.
		971
		972	That means after creating a group you have some time to add requests. And
		973	in the callbacks of those requests, you can add further requests to the
		974	group. And only when all those requests have finished will the the group
		975	itself finish.
		976
		977	=over 4
		978
		979	=item add $grp ...
		980
		981	=item $grp->add (...)
		982
		983	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		984	be added, including other groups, as long as you do not create circular
		985	dependencies.
		986
		987	Returns all its arguments.
		988
		989	=item $grp->cancel_subs
		990
		991	Cancel all subrequests and clears any feeder, but not the group request
		992	itself. Useful when you queued a lot of events but got a result early.
		993
		994	=item $grp->result (...)
		995
		996	Set the result value(s) that will be passed to the group callback when all
		997	subrequests have finished and set thre groups errno to the current value
		998	of errno (just like calling C<errno> without an error number). By default,
		999	no argument will be passed and errno is zero.
		1000
		1001	=item $grp->errno ([$errno])
		1002
		1003	Sets the group errno value to C<$errno>, or the current value of errno
		1004	when the argument is missing.
		1005
		1006	Every aio request has an associated errno value that is restored when
		1007	the callback is invoked. This method lets you change this value from its
		1008	default (0).
		1009
		1010	Calling C<result> will also set errno, so make sure you either set C<$!>
		1011	before the call to C<result>, or call c<errno> after it.
		1012
		1013	=item feed $grp $callback->($grp)
		1014
		1015	Sets a feeder/generator on this group: every group can have an attached
		1016	generator that generates requests if idle. The idea behind this is that,
		1017	although you could just queue as many requests as you want in a group,
		1018	this might starve other requests for a potentially long time. For
		1019	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1020	requests, delaying any later requests for a long time.
		1021
		1022	To avoid this, and allow incremental generation of requests, you can
		1023	instead a group and set a feeder on it that generates those requests. The
		1024	feed callback will be called whenever there are few enough (see C<limit>,
		1025	below) requests active in the group itself and is expected to queue more
		1026	requests.
		1027
		1028	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1029	not impose any limits).
		1030
		1031	If the feed does not queue more requests when called, it will be
		1032	automatically removed from the group.
		1033
		1034	If the feed limit is C<0>, it will be set to C<2> automatically.
		1035
		1036	Example:
		1037
		1038	# stat all files in @files, but only ever use four aio requests concurrently:
		1039
		1040	my $grp = aio_group sub { print "finished\n" };
		1041	limit $grp 4;
		1042	feed $grp sub {
		1043	my $file = pop @files
		1044	or return;
		1045
		1046	add $grp aio_stat $file, sub { ... };
		1047	};
		1048
		1049	=item limit $grp $num
		1050
		1051	Sets the feeder limit for the group: The feeder will be called whenever
		1052	the group contains less than this many requests.
		1053
		1054	Setting the limit to C<0> will pause the feeding process.
		1055
		1056	=back
		1057
524	=head2 SUPPORT FUNCTIONS	1058	=head2 SUPPORT FUNCTIONS
		1059
		1060	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
525		1061
526	=over 4	1062	=over 4
527		1063
528	=item $fileno = IO::AIO::poll_fileno	1064	=item $fileno = IO::AIO::poll_fileno
529		1065
…		…
534		1070
535	See C<poll_cb> for an example.	1071	See C<poll_cb> for an example.
536		1072
537	=item IO::AIO::poll_cb	1073	=item IO::AIO::poll_cb
538		1074
539	Process all outstanding events on the result pipe. You have to call this	1075	Process some outstanding events on the result pipe. You have to call this
540	regularly. Returns the number of events processed. Returns immediately	1076	regularly. Returns the number of events processed. Returns immediately
541	when no events are outstanding.	1077	when no events are outstanding. The amount of events processed depends on
		1078	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1079
		1080	If not all requests were processed for whatever reason, the filehandle
		1081	will still be ready when C<poll_cb> returns.
542		1082
543	Example: Install an Event watcher that automatically calls	1083	Example: Install an Event watcher that automatically calls
544	IO::AIO::poll_cb with high priority:	1084	IO::AIO::poll_cb with high priority:
545		1085
546	Event->io (fd => IO::AIO::poll_fileno,	1086	Event->io (fd => IO::AIO::poll_fileno,
547	poll => 'r', async => 1,	1087	poll => 'r', async => 1,
548	cb => \&IO::AIO::poll_cb);	1088	cb => \&IO::AIO::poll_cb);
549		1089
		1090	=item IO::AIO::max_poll_reqs $nreqs
		1091
		1092	=item IO::AIO::max_poll_time $seconds
		1093
		1094	These set the maximum number of requests (default C<0>, meaning infinity)
		1095	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1096	the maximum amount of time (default C<0>, meaning infinity) spent in
		1097	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1098	of time C<poll_cb> is allowed to use).
		1099
		1100	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1101	syscall per request processed, which is not normally a problem unless your
		1102	callbacks are really really fast or your OS is really really slow (I am
		1103	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1104
		1105	Setting these is useful if you want to ensure some level of
		1106	interactiveness when perl is not fast enough to process all requests in
		1107	time.
		1108
		1109	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1110
		1111	Example: Install an Event watcher that automatically calls
		1112	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1113	program get the CPU sometimes even under high AIO load.
		1114
		1115	# try not to spend much more than 0.1s in poll_cb
		1116	IO::AIO::max_poll_time 0.1;
		1117
		1118	# use a low priority so other tasks have priority
		1119	Event->io (fd => IO::AIO::poll_fileno,
		1120	poll => 'r', nice => 1,
		1121	cb => &IO::AIO::poll_cb);
		1122
550	=item IO::AIO::poll_wait	1123	=item IO::AIO::poll_wait
551		1124
		1125	If there are any outstanding requests and none of them in the result
552	Wait till the result filehandle becomes ready for reading (simply does a	1126	phase, wait till the result filehandle becomes ready for reading (simply
553	C<select> on the filehandle. This is useful if you want to synchronously wait	1127	does a C<select> on the filehandle. This is useful if you want to
554	for some requests to finish).	1128	synchronously wait for some requests to finish).
555		1129
556	See C<nreqs> for an example.	1130	See C<nreqs> for an example.
557		1131
		1132	=item IO::AIO::poll
		1133
		1134	Waits until some requests have been handled.
		1135
		1136	Returns the number of requests processed, but is otherwise strictly
		1137	equivalent to:
		1138
		1139	IO::AIO::poll_wait, IO::AIO::poll_cb
		1140
558	=item IO::AIO::nreqs	1141	=item IO::AIO::flush
559		1142
560	Returns the number of requests currently outstanding (i.e. for which their	1143	Wait till all outstanding AIO requests have been handled.
561	callback has not been invoked yet).
562		1144
563	Example: wait till there are no outstanding requests anymore:	1145	Strictly equivalent to:
564		1146
565	IO::AIO::poll_wait, IO::AIO::poll_cb	1147	IO::AIO::poll_wait, IO::AIO::poll_cb
566	while IO::AIO::nreqs;	1148	while IO::AIO::nreqs;
567		1149
568	=item IO::AIO::flush	1150	=back
569		1151
570	Wait till all outstanding AIO requests have been handled.	1152	=head3 CONTROLLING THE NUMBER OF THREADS
571		1153
572	Strictly equivalent to:	1154	=over
573
574	IO::AIO::poll_wait, IO::AIO::poll_cb
575	while IO::AIO::nreqs;
576
577	=item IO::AIO::poll
578
579	Waits until some requests have been handled.
580
581	Strictly equivalent to:
582
583	IO::AIO::poll_wait, IO::AIO::poll_cb
584	if IO::AIO::nreqs;
585		1155
586	=item IO::AIO::min_parallel $nthreads	1156	=item IO::AIO::min_parallel $nthreads
587		1157
588	Set the minimum number of AIO threads to C<$nthreads>. The current default	1158	Set the minimum number of AIO threads to C<$nthreads>. The current
589	is C<4>, which means four asynchronous operations can be done at one time	1159	default is C<8>, which means eight asynchronous operations can execute
590	(the number of outstanding operations, however, is unlimited).	1160	concurrently at any one time (the number of outstanding requests,
		1161	however, is unlimited).
591		1162
592	IO::AIO starts threads only on demand, when an AIO request is queued and	1163	IO::AIO starts threads only on demand, when an AIO request is queued and
593	no free thread exists.	1164	no free thread exists. Please note that queueing up a hundred requests can
		1165	create demand for a hundred threads, even if it turns out that everything
		1166	is in the cache and could have been processed faster by a single thread.
594		1167
595	It is recommended to keep the number of threads low, as some Linux	1168	It is recommended to keep the number of threads relatively low, as some
596	kernel versions will scale negatively with the number of threads (higher	1169	Linux kernel versions will scale negatively with the number of threads
597	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1170	(higher parallelity => MUCH higher latency). With current Linux 2.6
598	threads should be fine.	1171	versions, 4-32 threads should be fine.
599		1172
600	Under most circumstances you don't need to call this function, as the	1173	Under most circumstances you don't need to call this function, as the
601	module selects a default that is suitable for low to moderate load.	1174	module selects a default that is suitable for low to moderate load.
602		1175
603	=item IO::AIO::max_parallel $nthreads	1176	=item IO::AIO::max_parallel $nthreads
…		…
612	This module automatically runs C<max_parallel 0> at program end, to ensure	1185	This module automatically runs C<max_parallel 0> at program end, to ensure
613	that all threads are killed and that there are no outstanding requests.	1186	that all threads are killed and that there are no outstanding requests.
614		1187
615	Under normal circumstances you don't need to call this function.	1188	Under normal circumstances you don't need to call this function.
616		1189
		1190	=item IO::AIO::max_idle $nthreads
		1191
		1192	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1193	threads that did not get a request to process within 10 seconds). That
		1194	means if a thread becomes idle while C<$nthreads> other threads are also
		1195	idle, it will free its resources and exit.
		1196
		1197	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1198	to allow for extremely high load situations, but want to free resources
		1199	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1200
		1201	The default is probably ok in most situations, especially if thread
		1202	creation is fast. If thread creation is very slow on your system you might
		1203	want to use larger values.
		1204
617	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1205	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1206
		1207	This is a very bad function to use in interactive programs because it
		1208	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1209	use an C<aio_group> together with a feed callback.
618		1210
619	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1211	Sets the maximum number of outstanding requests to C<$nreqs>. If you
620	try to queue up more than this number of requests, the caller will block until	1212	do queue up more than this number of requests, the next call to the
621	some requests have been handled.	1213	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1214	function will block until the limit is no longer exceeded.
622		1215
623	The default is very large, so normally there is no practical limit. If you	1216	The default value is very large, so there is no practical limit on the
624	queue up many requests in a loop it often improves speed if you set	1217	number of outstanding requests.
625	this to a relatively low number, such as C<100>.
626		1218
627	Under normal circumstances you don't need to call this function.	1219	You can still queue as many requests as you want. Therefore,
		1220	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1221	as a stop gap to shield against fatal memory overflow (with large values).
		1222
		1223	=back
		1224
		1225	=head3 STATISTICAL INFORMATION
		1226
		1227	=over
		1228
		1229	=item IO::AIO::nreqs
		1230
		1231	Returns the number of requests currently in the ready, execute or pending
		1232	states (i.e. for which their callback has not been invoked yet).
		1233
		1234	Example: wait till there are no outstanding requests anymore:
		1235
		1236	IO::AIO::poll_wait, IO::AIO::poll_cb
		1237	while IO::AIO::nreqs;
		1238
		1239	=item IO::AIO::nready
		1240
		1241	Returns the number of requests currently in the ready state (not yet
		1242	executed).
		1243
		1244	=item IO::AIO::npending
		1245
		1246	Returns the number of requests currently in the pending state (executed,
		1247	but not yet processed by poll_cb).
628		1248
629	=back	1249	=back
630		1250
631	=cut	1251	=cut
632		1252
…		…
644	or return undef;	1264	or return undef;
645		1265
646	*$sym	1266	*$sym
647	}	1267	}
648		1268
649	min_parallel 4;	1269	min_parallel 8;
650		1270
651	END {	1271	END { flush }
652	max_parallel 0;
653	}
654		1272
655	1;	1273	1;
656		1274
657	=head2 FORK BEHAVIOUR	1275	=head2 FORK BEHAVIOUR
658		1276
659	This module should do "the right thing" when the process using it forks:	1277	This module should do "the right thing" when the process using it forks:
660		1278
661	Before the fork, IO::AIO enters a quiescent state where no requests	1279	Before the fork, IO::AIO enters a quiescent state where no requests
662	can be added in other threads and no results will be processed. After	1280	can be added in other threads and no results will be processed. After
663	the fork the parent simply leaves the quiescent state and continues	1281	the fork the parent simply leaves the quiescent state and continues
664	request/result processing, while the child clears the request/result	1282	request/result processing, while the child frees the request/result queue
665	queue (so the requests started before the fork will only be handled in	1283	(so that the requests started before the fork will only be handled in the
666	the parent). Threads will be started on demand until the limit ste in the	1284	parent). Threads will be started on demand until the limit set in the
667	parent process has been reached again.	1285	parent process has been reached again.
668		1286
669	In short: the parent will, after a short pause, continue as if fork had	1287	In short: the parent will, after a short pause, continue as if fork had
670	not been called, while the child will act as if IO::AIO has not been used	1288	not been called, while the child will act as if IO::AIO has not been used
671	yet.	1289	yet.
672		1290
		1291	=head2 MEMORY USAGE
		1292
		1293	Per-request usage:
		1294
		1295	Each aio request uses - depending on your architecture - around 100-200
		1296	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1297	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1298	scalars and other data passed into aio requests will also be locked and
		1299	will consume memory till the request has entered the done state.
		1300
		1301	This is not awfully much, so queuing lots of requests is not usually a
		1302	problem.
		1303
		1304	Per-thread usage:
		1305
		1306	In the execution phase, some aio requests require more memory for
		1307	temporary buffers, and each thread requires a stack and other data
		1308	structures (usually around 16k-128k, depending on the OS).
		1309
		1310	=head1 KNOWN BUGS
		1311
		1312	Known bugs will be fixed in the next release.
		1313
673	=head1 SEE ALSO	1314	=head1 SEE ALSO
674		1315
675	L<Coro>, L<Linux::AIO> (obsolete).	1316	L<Coro::AIO>.
676		1317
677	=head1 AUTHOR	1318	=head1 AUTHOR
678		1319
679	Marc Lehmann <schmorp@schmorp.de>	1320	Marc Lehmann <schmorp@schmorp.de>
680	http://home.schmorp.de/	1321	http://home.schmorp.de/

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