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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.54 by root, Sun Oct 22 00:19:05 2006 UTC vs.
Revision 1.108 by root, Fri Jun 1 13:25:50 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 = '1.99';	194	our $VERSION = '2.4';
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	aio_group);	199	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
82	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	200	aio_chown aio_chmod aio_utime);
		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);
83		206
84	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
85		208
86	require XSLoader;	209	require XSLoader;
87	XSLoader::load ("IO::AIO", $VERSION);	210	XSLoader::load ("IO::AIO", $VERSION);
88	}	211	}
89		212
90	=head1 FUNCTIONS	213	=head1 FUNCTIONS
91		214
92	=head2 AIO FUNCTIONS	215	=head2 AIO REQUEST FUNCTIONS
93		216
94	All the C<aio_*> calls are more or less thin wrappers around the syscall	217	All the C<aio_*> calls are more or less thin wrappers around the syscall
95	with the same name (sans C<aio_>). The arguments are similar or identical,	218	with the same name (sans C<aio_>). The arguments are similar or identical,
96	and they all accept an additional (and optional) C<$callback> argument	219	and they all accept an additional (and optional) C<$callback> argument
97	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
…		…
100	syscall has been executed asynchronously.	223	syscall has been executed asynchronously.
101		224
102	All functions expecting a filehandle keep a copy of the filehandle	225	All functions expecting a filehandle keep a copy of the filehandle
103	internally until the request has finished.	226	internally until the request has finished.
104		227
105	All non-composite requests (requests that are not broken down into
106	multiple requests) return objects of type L<IO::AIO::REQ> that allow	228	All functions return request objects of type L<IO::AIO::REQ> that allow
107	further manipulation of running requests.	229	further manipulation of those requests while they are in-flight.
108		230
109	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
110	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
111	request is being executed, the current working directory could have	233	request is being executed, the current working directory could have
112	changed. Alternatively, you can make sure that you never change the	234	changed. Alternatively, you can make sure that you never change the
113	current working directory.	235	current working directory anywhere in the program and then use relative
		236	paths.
114		237
115	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
116	always pass in filenames you got from outside (command line, readdir	239	in filenames you got from outside (command line, readdir etc.) without
117	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
118	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
119	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)
120	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.
121		247
122	=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
123		282
124	=item aio_open $pathname, $flags, $mode, $callback->($fh)	283	=item aio_open $pathname, $flags, $mode, $callback->($fh)
125		284
126	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
127	created filehandle for the file.	286	created filehandle for the file.
…		…
133	list. They are the same as used by C<sysopen>.	292	list. They are the same as used by C<sysopen>.
134		293
135	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
136	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>,
137	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,
138	and C<0666> or C<0777> if you do).	297	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		298	by the umask in effect then the request is being executed, so better never
		299	change the umask.
139		300
140	Example:	301	Example:
141		302
142	aio_open "/etc/passwd", O_RDONLY, 0, sub {	303	aio_open "/etc/passwd", O_RDONLY, 0, sub {
143	if ($_[0]) {	304	if ($_[0]) {
…		…
146	} else {	307	} else {
147	die "open failed: $!\n";	308	die "open failed: $!\n";
148	}	309	}
149	};	310	};
150		311
		312
151	=item aio_close $fh, $callback->($status)	313	=item aio_close $fh, $callback->($status)
152		314
153	Asynchronously close a file and call the callback with the result	315	Asynchronously close a file and call the callback with the result
154	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
155	filehandle here, as perl will likely close the file descriptor another	317	filehandle here, as perl will likely close the file descriptor another
…		…
157	C<close> or just let filehandles go out of scope.	319	C<close> or just let filehandles go out of scope.
158		320
159	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
160	therefore best to avoid this function.	322	therefore best to avoid this function.
161		323
		324
162	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	325	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
163		326
164	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	327	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		328
166	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>
167	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
168	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
169	like the syscall).	332	like the syscall). If C<offset> is undefined, then the current file offset
		333	will be used (and updated), otherwise the file offset will not be changed
		334	by these calls.
170		335
171	The C<$data> scalar I<MUST NOT> be modified in any way while the request	336	The C<$data> scalar I<MUST NOT> be modified in any way while the request
172	is outstanding. Modifying it can result in segfaults or WW3 (if the	337	is outstanding. Modifying it can result in segfaults or World War III (if
173	necessary/optional hardware is installed).	338	the necessary/optional hardware is installed).
174		339
175	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	340	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
176	offset C<0> within the scalar:	341	offset C<0> within the scalar:
177		342
178	aio_read $fh, 7, 15, $buffer, 0, sub {	343	aio_read $fh, 7, 15, $buffer, 0, sub {
179	$_[0] > 0 or die "read error: $!";	344	$_[0] > 0 or die "read error: $!";
180	print "read $_[0] bytes: <$buffer>\n";	345	print "read $_[0] bytes: <$buffer>\n";
181	};	346	};
182		347
183	=item aio_move $srcpath, $dstpath, $callback->($status)
184
185	Try to move the I<file> (directories not supported as either source or
186	destination) from C<$srcpath> to C<$dstpath> and call the callback with
187	the C<0> (error) or C<-1> ok.
188
189	This is a composite request that tries to rename(2) the file first. If
190	rename files with C<EXDEV>, it creates the destination file with mode 0200
191	and copies the contents of the source file into it using C<aio_sendfile>,
192	followed by restoring atime, mtime, access mode and uid/gid, in that
193	order, and unlinking the C<$srcpath>.
194
195	If an error occurs, the partial destination file will be unlinked, if
196	possible, except when setting atime, mtime, access mode and uid/gid, where
197	errors are being ignored.
198
199	=cut
200
201	sub aio_move($$$) {
202	my ($src, $dst, $cb) = @_;
203
204	aio_rename $src, $dst, sub {
205	if ($_[0] && $! == EXDEV) {
206	aio_open $src, O_RDONLY, 0, sub {
207	if (my $src_fh = $_[0]) {
208	my @stat = stat $src_fh;
209
210	aio_open $dst, O_WRONLY, 0200, sub {
211	if (my $dst_fh = $_[0]) {
212	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
213	close $src_fh;
214
215	if ($_[0] == $stat[7]) {
216	utime $stat[8], $stat[9], $dst;
217	chmod $stat[2] & 07777, $dst_fh;
218	chown $stat[4], $stat[5], $dst_fh;
219	close $dst_fh;
220
221	aio_unlink $src, sub {
222	$cb->($_[0]);
223	};
224	} else {
225	my $errno = $!;
226	aio_unlink $dst, sub {
227	$! = $errno;
228	$cb->(-1);
229	};
230	}
231	};
232	} else {
233	$cb->(-1);
234	}
235	},
236
237	} else {
238	$cb->(-1);
239	}
240	};
241	} else {
242	$cb->($_[0]);
243	}
244	};
245	}
246		348
247	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	349	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
248		350
249	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	351	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
250	reading at byte offset C<$in_offset>, and starts writing at the current	352	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
264	C<$in_fh> than are written, and there is no way to find out how many	366	C<$in_fh> than are written, and there is no way to find out how many
265	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	367	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
266	provides the number of bytes written to C<$out_fh>. Only if the result	368	provides the number of bytes written to C<$out_fh>. Only if the result
267	value equals C<$length> one can assume that C<$length> bytes have been	369	value equals C<$length> one can assume that C<$length> bytes have been
268	read.	370	read.
		371
269		372
270	=item aio_readahead $fh,$offset,$length, $callback->($retval)	373	=item aio_readahead $fh,$offset,$length, $callback->($retval)
271		374
272	C<aio_readahead> populates the page cache with data from a file so that	375	C<aio_readahead> populates the page cache with data from a file so that
273	subsequent reads from that file will not block on disk I/O. The C<$offset>	376	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
279	file. The current file offset of the file is left unchanged.	382	file. The current file offset of the file is left unchanged.
280		383
281	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	384	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
282	emulated by simply reading the data, which would have a similar effect.	385	emulated by simply reading the data, which would have a similar effect.
283		386
		387
284	=item aio_stat $fh_or_path, $callback->($status)	388	=item aio_stat $fh_or_path, $callback->($status)
285		389
286	=item aio_lstat $fh, $callback->($status)	390	=item aio_lstat $fh, $callback->($status)
287		391
288	Works like perl's C<stat> or C<lstat> in void context. The callback will	392	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
301	aio_stat "/etc/passwd", sub {	405	aio_stat "/etc/passwd", sub {
302	$_[0] and die "stat failed: $!";	406	$_[0] and die "stat failed: $!";
303	print "size is ", -s _, "\n";	407	print "size is ", -s _, "\n";
304	};	408	};
305		409
		410
		411	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		412
		413	Works like perl's C<utime> function (including the special case of $atime
		414	and $mtime being undef). Fractional times are supported if the underlying
		415	syscalls support them.
		416
		417	When called with a pathname, uses utimes(2) if available, otherwise
		418	utime(2). If called on a file descriptor, uses futimes(2) if available,
		419	otherwise returns ENOSYS, so this is not portable.
		420
		421	Examples:
		422
		423	# set atime and mtime to current time (basically touch(1)):
		424	aio_utime "path", undef, undef;
		425	# set atime to current time and mtime to beginning of the epoch:
		426	aio_utime "path", time, undef; # undef==0
		427
		428
		429	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		430
		431	Works like perl's C<chown> function, except that C<undef> for either $uid
		432	or $gid is being interpreted as "do not change" (but -1 can also be used).
		433
		434	Examples:
		435
		436	# same as "chown root path" in the shell:
		437	aio_chown "path", 0, -1;
		438	# same as above:
		439	aio_chown "path", 0, undef;
		440
		441
		442	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		443
		444	Works like perl's C<chmod> function.
		445
		446
306	=item aio_unlink $pathname, $callback->($status)	447	=item aio_unlink $pathname, $callback->($status)
307		448
308	Asynchronously unlink (delete) a file and call the callback with the	449	Asynchronously unlink (delete) a file and call the callback with the
309	result code.	450	result code.
310		451
		452
		453	=item aio_mknod $path, $mode, $dev, $callback->($status)
		454
		455	[EXPERIMENTAL]
		456
		457	Asynchronously create a device node (or fifo). See mknod(2).
		458
		459	The only (POSIX-) portable way of calling this function is:
		460
		461	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		462
		463
311	=item aio_link $srcpath, $dstpath, $callback->($status)	464	=item aio_link $srcpath, $dstpath, $callback->($status)
312		465
313	Asynchronously create a new link to the existing object at C<$srcpath> at	466	Asynchronously create a new link to the existing object at C<$srcpath> at
314	the path C<$dstpath> and call the callback with the result code.	467	the path C<$dstpath> and call the callback with the result code.
315		468
		469
316	=item aio_symlink $srcpath, $dstpath, $callback->($status)	470	=item aio_symlink $srcpath, $dstpath, $callback->($status)
317		471
318	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	472	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
319	the path C<$dstpath> and call the callback with the result code.	473	the path C<$dstpath> and call the callback with the result code.
320		474
		475
		476	=item aio_readlink $path, $callback->($link)
		477
		478	Asynchronously read the symlink specified by C<$path> and pass it to
		479	the callback. If an error occurs, nothing or undef gets passed to the
		480	callback.
		481
		482
321	=item aio_rename $srcpath, $dstpath, $callback->($status)	483	=item aio_rename $srcpath, $dstpath, $callback->($status)
322		484
323	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	485	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
324	rename(2) and call the callback with the result code.	486	rename(2) and call the callback with the result code.
325		487
		488
		489	=item aio_mkdir $pathname, $mode, $callback->($status)
		490
		491	Asynchronously mkdir (create) a directory and call the callback with
		492	the result code. C<$mode> will be modified by the umask at the time the
		493	request is executed, so do not change your umask.
		494
		495
326	=item aio_rmdir $pathname, $callback->($status)	496	=item aio_rmdir $pathname, $callback->($status)
327		497
328	Asynchronously rmdir (delete) a directory and call the callback with the	498	Asynchronously rmdir (delete) a directory and call the callback with the
329	result code.	499	result code.
		500
330		501
331	=item aio_readdir $pathname, $callback->($entries)	502	=item aio_readdir $pathname, $callback->($entries)
332		503
333	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	504	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
334	directory (i.e. opendir + readdir + closedir). The entries will not be	505	directory (i.e. opendir + readdir + closedir). The entries will not be
335	sorted, and will B<NOT> include the C<.> and C<..> entries.	506	sorted, and will B<NOT> include the C<.> and C<..> entries.
336		507
337	The callback a single argument which is either C<undef> or an array-ref	508	The callback a single argument which is either C<undef> or an array-ref
338	with the filenames.	509	with the filenames.
339		510
		511
		512	=item aio_load $path, $data, $callback->($status)
		513
		514	This is a composite request that tries to fully load the given file into
		515	memory. Status is the same as with aio_read.
		516
		517	=cut
		518
		519	sub aio_load($$;$) {
		520	aio_block {
		521	my ($path, undef, $cb) = @_;
		522	my $data = \$_[1];
		523
		524	my $pri = aioreq_pri;
		525	my $grp = aio_group $cb;
		526
		527	aioreq_pri $pri;
		528	add $grp aio_open $path, O_RDONLY, 0, sub {
		529	my $fh = shift
		530	or return $grp->result (-1);
		531
		532	aioreq_pri $pri;
		533	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		534	$grp->result ($_[0]);
		535	};
		536	};
		537
		538	$grp
		539	}
		540	}
		541
		542	=item aio_copy $srcpath, $dstpath, $callback->($status)
		543
		544	Try to copy the I<file> (directories not supported as either source or
		545	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		546	the C<0> (error) or C<-1> ok.
		547
		548	This is a composite request that it creates the destination file with
		549	mode 0200 and copies the contents of the source file into it using
		550	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		551	uid/gid, in that order.
		552
		553	If an error occurs, the partial destination file will be unlinked, if
		554	possible, except when setting atime, mtime, access mode and uid/gid, where
		555	errors are being ignored.
		556
		557	=cut
		558
		559	sub aio_copy($$;$) {
		560	aio_block {
		561	my ($src, $dst, $cb) = @_;
		562
		563	my $pri = aioreq_pri;
		564	my $grp = aio_group $cb;
		565
		566	aioreq_pri $pri;
		567	add $grp aio_open $src, O_RDONLY, 0, sub {
		568	if (my $src_fh = $_[0]) {
		569	my @stat = stat $src_fh;
		570
		571	aioreq_pri $pri;
		572	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		573	if (my $dst_fh = $_[0]) {
		574	aioreq_pri $pri;
		575	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		576	if ($_[0] == $stat[7]) {
		577	$grp->result (0);
		578	close $src_fh;
		579
		580	# those should not normally block. should. should.
		581	utime $stat[8], $stat[9], $dst;
		582	chmod $stat[2] & 07777, $dst_fh;
		583	chown $stat[4], $stat[5], $dst_fh;
		584	close $dst_fh;
		585	} else {
		586	$grp->result (-1);
		587	close $src_fh;
		588	close $dst_fh;
		589
		590	aioreq $pri;
		591	add $grp aio_unlink $dst;
		592	}
		593	};
		594	} else {
		595	$grp->result (-1);
		596	}
		597	},
		598
		599	} else {
		600	$grp->result (-1);
		601	}
		602	};
		603
		604	$grp
		605	}
		606	}
		607
		608	=item aio_move $srcpath, $dstpath, $callback->($status)
		609
		610	Try to move the I<file> (directories not supported as either source or
		611	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		612	the C<0> (error) or C<-1> ok.
		613
		614	This is a composite request that tries to rename(2) the file first. If
		615	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		616	that is successful, unlinking the C<$srcpath>.
		617
		618	=cut
		619
		620	sub aio_move($$;$) {
		621	aio_block {
		622	my ($src, $dst, $cb) = @_;
		623
		624	my $pri = aioreq_pri;
		625	my $grp = aio_group $cb;
		626
		627	aioreq_pri $pri;
		628	add $grp aio_rename $src, $dst, sub {
		629	if ($_[0] && $! == EXDEV) {
		630	aioreq_pri $pri;
		631	add $grp aio_copy $src, $dst, sub {
		632	$grp->result ($_[0]);
		633
		634	if (!$_[0]) {
		635	aioreq_pri $pri;
		636	add $grp aio_unlink $src;
		637	}
		638	};
		639	} else {
		640	$grp->result ($_[0]);
		641	}
		642	};
		643
		644	$grp
		645	}
		646	}
		647
340	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	648	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
341		649
342	Scans a directory (similar to C<aio_readdir>) but additionally tries to	650	Scans a directory (similar to C<aio_readdir>) but additionally tries to
343	separate the entries of directory C<$path> into two sets of names, ones	651	efficiently separate the entries of directory C<$path> into two sets of
344	you can recurse into (directories or links to them), and ones you cannot	652	names, directories you can recurse into (directories), and ones you cannot
345	recurse into (everything else).	653	recurse into (everything else, including symlinks to directories).
346		654
347	C<aio_scandir> is a composite request that consists of many sub	655	C<aio_scandir> is a composite request that creates of many sub requests_
348	requests. C<$maxreq> specifies the maximum number of outstanding aio	656	C<$maxreq> specifies the maximum number of outstanding aio requests that
349	requests that this function generates. If it is C<< <= 0 >>, then a	657	this function generates. If it is C<< <= 0 >>, then a suitable default
350	suitable default will be chosen (currently 8).	658	will be chosen (currently 4).
351		659
352	On error, the callback is called without arguments, otherwise it receives	660	On error, the callback is called without arguments, otherwise it receives
353	two array-refs with path-relative entry names.	661	two array-refs with path-relative entry names.
354		662
355	Example:	663	Example:
…		…
389	as those tend to return 0 or 1 as link counts, which disables the	697	as those tend to return 0 or 1 as link counts, which disables the
390	directory counting heuristic.	698	directory counting heuristic.
391		699
392	=cut	700	=cut
393		701
394	sub aio_scandir($$$) {	702	sub aio_scandir($$;$) {
		703	aio_block {
395	my ($path, $maxreq, $cb) = @_;	704	my ($path, $maxreq, $cb) = @_;
396		705
		706	my $pri = aioreq_pri;
		707
		708	my $grp = aio_group $cb;
		709
397	$maxreq = 8 if $maxreq <= 0;	710	$maxreq = 4 if $maxreq <= 0;
398		711
399	# stat once	712	# stat once
		713	aioreq_pri $pri;
400	aio_stat $path, sub {	714	add $grp aio_stat $path, sub {
401	return $cb->() if $_[0];	715	return $grp->result () if $_[0];
402	my $now = time;	716	my $now = time;
403	my $hash1 = join ":", (stat _)[0,1,3,7,9];	717	my $hash1 = join ":", (stat _)[0,1,3,7,9];
404		718
405	# read the directory entries	719	# read the directory entries
		720	aioreq_pri $pri;
406	aio_readdir $path, sub {	721	add $grp aio_readdir $path, sub {
407	my $entries = shift	722	my $entries = shift
408	or return $cb->();	723	or return $grp->result ();
409		724
410	# stat the dir another time	725	# stat the dir another time
		726	aioreq_pri $pri;
411	aio_stat $path, sub {	727	add $grp aio_stat $path, sub {
412	my $hash2 = join ":", (stat _)[0,1,3,7,9];	728	my $hash2 = join ":", (stat _)[0,1,3,7,9];
413		729
414	my $ndirs;	730	my $ndirs;
415		731
416	# take the slow route if anything looks fishy	732	# take the slow route if anything looks fishy
417	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	733	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
418	$ndirs = -1;	734	$ndirs = -1;
419	} else {	735	} else {
420	# if nlink == 2, we are finished	736	# if nlink == 2, we are finished
421	# on non-posix-fs's, we rely on nlink < 2	737	# on non-posix-fs's, we rely on nlink < 2
422	$ndirs = (stat _)[3] - 2	738	$ndirs = (stat _)[3] - 2
423	or return $cb->([], $entries);	739	or return $grp->result ([], $entries);
424	}
425
426	# sort into likely dirs and likely nondirs
427	# dirs == files without ".", short entries first
428	$entries = [map $_->[0],
429	sort { $b->[1] cmp $a->[1] }
430	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
431	@$entries];
432
433	my (@dirs, @nondirs);
434
435	my ($statcb, $schedcb);
436	my $nreq = 0;
437
438	$schedcb = sub {
439	if (@$entries) {
440	if ($nreq < $maxreq) {
441	my $ent = pop @$entries;
442	$nreq++;
443	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
444	}
445	} elsif (!$nreq) {
446	# finished
447	undef $statcb;
448	undef $schedcb;
449	$cb->(\@dirs, \@nondirs) if $cb;
450	undef $cb;
451	}	740	}
		741
		742	# sort into likely dirs and likely nondirs
		743	# dirs == files without ".", short entries first
		744	$entries = [map $_->[0],
		745	sort { $b->[1] cmp $a->[1] }
		746	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		747	@$entries];
		748
		749	my (@dirs, @nondirs);
		750
		751	my $statgrp = add $grp aio_group sub {
		752	$grp->result (\@dirs, \@nondirs);
		753	};
		754
		755	limit $statgrp $maxreq;
		756	feed $statgrp sub {
		757	return unless @$entries;
		758	my $entry = pop @$entries;
		759
		760	aioreq_pri $pri;
		761	add $statgrp aio_stat "$path/$entry/.", sub {
		762	if ($_[0] < 0) {
		763	push @nondirs, $entry;
		764	} else {
		765	# need to check for real directory
		766	aioreq_pri $pri;
		767	add $statgrp aio_lstat "$path/$entry", sub {
		768	if (-d _) {
		769	push @dirs, $entry;
		770
		771	unless (--$ndirs) {
		772	push @nondirs, @$entries;
		773	feed $statgrp;
		774	}
		775	} else {
		776	push @nondirs, $entry;
		777	}
		778	}
		779	}
		780	};
		781	};
452	};	782	};
453	$statcb = sub {
454	my ($status, $entry) = @_;
455
456	if ($status < 0) {
457	$nreq--;
458	push @nondirs, $entry;
459	&$schedcb;
460	} else {
461	# need to check for real directory
462	aio_lstat "$path/$entry", sub {
463	$nreq--;
464
465	if (-d _) {
466	push @dirs, $entry;
467
468	if (!--$ndirs) {
469	push @nondirs, @$entries;
470	$entries = [];
471	}
472	} else {
473	push @nondirs, $entry;
474	}
475
476	&$schedcb;
477	}
478	}
479	};
480
481	&$schedcb while @$entries && $nreq < $maxreq;
482	};	783	};
483	};	784	};
		785
		786	$grp
484	};	787	}
		788	}
		789
		790	=item aio_rmtree $path, $callback->($status)
		791
		792	Delete a directory tree starting (and including) C<$path>, return the
		793	status of the final C<rmdir> only. This is a composite request that
		794	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		795	everything else.
		796
		797	=cut
		798
		799	sub aio_rmtree;
		800	sub aio_rmtree($;$) {
		801	aio_block {
		802	my ($path, $cb) = @_;
		803
		804	my $pri = aioreq_pri;
		805	my $grp = aio_group $cb;
		806
		807	aioreq_pri $pri;
		808	add $grp aio_scandir $path, 0, sub {
		809	my ($dirs, $nondirs) = @_;
		810
		811	my $dirgrp = aio_group sub {
		812	add $grp aio_rmdir $path, sub {
		813	$grp->result ($_[0]);
		814	};
		815	};
		816
		817	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		818	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		819
		820	add $grp $dirgrp;
		821	};
		822
		823	$grp
		824	}
485	}	825	}
486		826
487	=item aio_fsync $fh, $callback->($status)	827	=item aio_fsync $fh, $callback->($status)
488		828
489	Asynchronously call fsync on the given filehandle and call the callback	829	Asynchronously call fsync on the given filehandle and call the callback
…		…
495	callback with the fdatasync result code.	835	callback with the fdatasync result code.
496		836
497	If this call isn't available because your OS lacks it or it couldn't be	837	If this call isn't available because your OS lacks it or it couldn't be
498	detected, it will be emulated by calling C<fsync> instead.	838	detected, it will be emulated by calling C<fsync> instead.
499		839
500	=item aio_group $callback->()	840	=item aio_group $callback->(...)
501		841
		842	This is a very special aio request: Instead of doing something, it is a
		843	container for other aio requests, which is useful if you want to bundle
		844	many requests into a single, composite, request with a definite callback
		845	and the ability to cancel the whole request with its subrequests.
		846
		847	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		848	for more info.
		849
		850	Example:
		851
		852	my $grp = aio_group sub {
		853	print "all stats done\n";
		854	};
		855
		856	add $grp
		857	(aio_stat ...),
		858	(aio_stat ...),
		859	...;
		860
		861	=item aio_nop $callback->()
		862
		863	This is a special request - it does nothing in itself and is only used for
		864	side effects, such as when you want to add a dummy request to a group so
		865	that finishing the requests in the group depends on executing the given
		866	code.
		867
		868	While this request does nothing, it still goes through the execution
		869	phase and still requires a worker thread. Thus, the callback will not
		870	be executed immediately but only after other requests in the queue have
		871	entered their execution phase. This can be used to measure request
		872	latency.
		873
502	=item aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	874	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
503		875
504	Mainly used for debugging and benchmarking, this aio request puts one of	876	Mainly used for debugging and benchmarking, this aio request puts one of
505	the request workers to sleep for the given time.	877	the request workers to sleep for the given time.
506		878
		879	While it is theoretically handy to have simple I/O scheduling requests
		880	like sleep and file handle readable/writable, the overhead this creates is
		881	immense (it blocks a thread for a long time) so do not use this function
		882	except to put your application under artificial I/O pressure.
		883
507	=back	884	=back
508		885
509	=head2 IO::AIO::REQ CLASS	886	=head2 IO::AIO::REQ CLASS
510		887
511	All non-aggregate C<aio_*> functions return an object of this class when	888	All non-aggregate C<aio_*> functions return an object of this class when
512	called in non-void context.	889	called in non-void context.
513		890
514	A request always moves through the following five states in its lifetime,
515	in order: B<ready> (request has been created, but has not been executed
516	yet), B<execute> (request is currently being executed), B<pending>
517	(request has been executed but callback has not been called yet),
518	B<result> (results are being processed synchronously, includes calling the
519	callback) and B<done> (request has reached the end of its lifetime and
520	holds no resources anymore).
521
522	=over 4	891	=over 4
523		892
524	=item $req->cancel	893	=item cancel $req
525		894
526	Cancels the request, if possible. Has the effect of skipping execution	895	Cancels the request, if possible. Has the effect of skipping execution
527	when entering the B<execute> state and skipping calling the callback when	896	when entering the B<execute> state and skipping calling the callback when
528	entering the the B<result> state, but will leave the request otherwise	897	entering the the B<result> state, but will leave the request otherwise
529	untouched. That means that requests that currently execute will not be	898	untouched. That means that requests that currently execute will not be
530	stopped and resources held by the request will not be freed prematurely.	899	stopped and resources held by the request will not be freed prematurely.
531		900
		901	=item cb $req $callback->(...)
		902
		903	Replace (or simply set) the callback registered to the request.
		904
532	=back	905	=back
533		906
		907	=head2 IO::AIO::GRP CLASS
		908
		909	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		910	objects of this class, too.
		911
		912	A IO::AIO::GRP object is a special request that can contain multiple other
		913	aio requests.
		914
		915	You create one by calling the C<aio_group> constructing function with a
		916	callback that will be called when all contained requests have entered the
		917	C<done> state:
		918
		919	my $grp = aio_group sub {
		920	print "all requests are done\n";
		921	};
		922
		923	You add requests by calling the C<add> method with one or more
		924	C<IO::AIO::REQ> objects:
		925
		926	$grp->add (aio_unlink "...");
		927
		928	add $grp aio_stat "...", sub {
		929	$_[0] or return $grp->result ("error");
		930
		931	# add another request dynamically, if first succeeded
		932	add $grp aio_open "...", sub {
		933	$grp->result ("ok");
		934	};
		935	};
		936
		937	This makes it very easy to create composite requests (see the source of
		938	C<aio_move> for an application) that work and feel like simple requests.
		939
		940	=over 4
		941
		942	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		943	C<IO::AIO::poll_cb>, just like any other request.
		944
		945	=item * They can be canceled like any other request. Canceling will cancel not
		946	only the request itself, but also all requests it contains.
		947
		948	=item * They can also can also be added to other IO::AIO::GRP objects.
		949
		950	=item * You must not add requests to a group from within the group callback (or
		951	any later time).
		952
		953	=back
		954
		955	Their lifetime, simplified, looks like this: when they are empty, they
		956	will finish very quickly. If they contain only requests that are in the
		957	C<done> state, they will also finish. Otherwise they will continue to
		958	exist.
		959
		960	That means after creating a group you have some time to add requests. And
		961	in the callbacks of those requests, you can add further requests to the
		962	group. And only when all those requests have finished will the the group
		963	itself finish.
		964
		965	=over 4
		966
		967	=item add $grp ...
		968
		969	=item $grp->add (...)
		970
		971	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		972	be added, including other groups, as long as you do not create circular
		973	dependencies.
		974
		975	Returns all its arguments.
		976
		977	=item $grp->cancel_subs
		978
		979	Cancel all subrequests and clears any feeder, but not the group request
		980	itself. Useful when you queued a lot of events but got a result early.
		981
		982	=item $grp->result (...)
		983
		984	Set the result value(s) that will be passed to the group callback when all
		985	subrequests have finished and set thre groups errno to the current value
		986	of errno (just like calling C<errno> without an error number). By default,
		987	no argument will be passed and errno is zero.
		988
		989	=item $grp->errno ([$errno])
		990
		991	Sets the group errno value to C<$errno>, or the current value of errno
		992	when the argument is missing.
		993
		994	Every aio request has an associated errno value that is restored when
		995	the callback is invoked. This method lets you change this value from its
		996	default (0).
		997
		998	Calling C<result> will also set errno, so make sure you either set C<$!>
		999	before the call to C<result>, or call c<errno> after it.
		1000
		1001	=item feed $grp $callback->($grp)
		1002
		1003	Sets a feeder/generator on this group: every group can have an attached
		1004	generator that generates requests if idle. The idea behind this is that,
		1005	although you could just queue as many requests as you want in a group,
		1006	this might starve other requests for a potentially long time. For
		1007	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1008	requests, delaying any later requests for a long time.
		1009
		1010	To avoid this, and allow incremental generation of requests, you can
		1011	instead a group and set a feeder on it that generates those requests. The
		1012	feed callback will be called whenever there are few enough (see C<limit>,
		1013	below) requests active in the group itself and is expected to queue more
		1014	requests.
		1015
		1016	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1017	not impose any limits).
		1018
		1019	If the feed does not queue more requests when called, it will be
		1020	automatically removed from the group.
		1021
		1022	If the feed limit is C<0>, it will be set to C<2> automatically.
		1023
		1024	Example:
		1025
		1026	# stat all files in @files, but only ever use four aio requests concurrently:
		1027
		1028	my $grp = aio_group sub { print "finished\n" };
		1029	limit $grp 4;
		1030	feed $grp sub {
		1031	my $file = pop @files
		1032	or return;
		1033
		1034	add $grp aio_stat $file, sub { ... };
		1035	};
		1036
		1037	=item limit $grp $num
		1038
		1039	Sets the feeder limit for the group: The feeder will be called whenever
		1040	the group contains less than this many requests.
		1041
		1042	Setting the limit to C<0> will pause the feeding process.
		1043
		1044	=back
		1045
534	=head2 SUPPORT FUNCTIONS	1046	=head2 SUPPORT FUNCTIONS
		1047
		1048	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
535		1049
536	=over 4	1050	=over 4
537		1051
538	=item $fileno = IO::AIO::poll_fileno	1052	=item $fileno = IO::AIO::poll_fileno
539		1053
…		…
544		1058
545	See C<poll_cb> for an example.	1059	See C<poll_cb> for an example.
546		1060
547	=item IO::AIO::poll_cb	1061	=item IO::AIO::poll_cb
548		1062
549	Process all outstanding events on the result pipe. You have to call this	1063	Process some outstanding events on the result pipe. You have to call this
550	regularly. Returns the number of events processed. Returns immediately	1064	regularly. Returns the number of events processed. Returns immediately
551	when no events are outstanding.	1065	when no events are outstanding. The amount of events processed depends on
		1066	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1067
		1068	If not all requests were processed for whatever reason, the filehandle
		1069	will still be ready when C<poll_cb> returns.
552		1070
553	Example: Install an Event watcher that automatically calls	1071	Example: Install an Event watcher that automatically calls
554	IO::AIO::poll_cb with high priority:	1072	IO::AIO::poll_cb with high priority:
555		1073
556	Event->io (fd => IO::AIO::poll_fileno,	1074	Event->io (fd => IO::AIO::poll_fileno,
557	poll => 'r', async => 1,	1075	poll => 'r', async => 1,
558	cb => \&IO::AIO::poll_cb);	1076	cb => \&IO::AIO::poll_cb);
559		1077
		1078	=item IO::AIO::max_poll_reqs $nreqs
		1079
		1080	=item IO::AIO::max_poll_time $seconds
		1081
		1082	These set the maximum number of requests (default C<0>, meaning infinity)
		1083	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1084	the maximum amount of time (default C<0>, meaning infinity) spent in
		1085	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1086	of time C<poll_cb> is allowed to use).
		1087
		1088	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1089	syscall per request processed, which is not normally a problem unless your
		1090	callbacks are really really fast or your OS is really really slow (I am
		1091	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1092
		1093	Setting these is useful if you want to ensure some level of
		1094	interactiveness when perl is not fast enough to process all requests in
		1095	time.
		1096
		1097	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1098
		1099	Example: Install an Event watcher that automatically calls
		1100	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1101	program get the CPU sometimes even under high AIO load.
		1102
		1103	# try not to spend much more than 0.1s in poll_cb
		1104	IO::AIO::max_poll_time 0.1;
		1105
		1106	# use a low priority so other tasks have priority
		1107	Event->io (fd => IO::AIO::poll_fileno,
		1108	poll => 'r', nice => 1,
		1109	cb => &IO::AIO::poll_cb);
		1110
560	=item IO::AIO::poll_wait	1111	=item IO::AIO::poll_wait
561		1112
		1113	If there are any outstanding requests and none of them in the result
562	Wait till the result filehandle becomes ready for reading (simply does a	1114	phase, wait till the result filehandle becomes ready for reading (simply
563	C<select> on the filehandle. This is useful if you want to synchronously wait	1115	does a C<select> on the filehandle. This is useful if you want to
564	for some requests to finish).	1116	synchronously wait for some requests to finish).
565		1117
566	See C<nreqs> for an example.	1118	See C<nreqs> for an example.
567		1119
		1120	=item IO::AIO::poll
		1121
		1122	Waits until some requests have been handled.
		1123
		1124	Returns the number of requests processed, but is otherwise strictly
		1125	equivalent to:
		1126
		1127	IO::AIO::poll_wait, IO::AIO::poll_cb
		1128
568	=item IO::AIO::nreqs	1129	=item IO::AIO::flush
569		1130
570	Returns the number of requests currently outstanding (i.e. for which their	1131	Wait till all outstanding AIO requests have been handled.
571	callback has not been invoked yet).
572		1132
573	Example: wait till there are no outstanding requests anymore:	1133	Strictly equivalent to:
574		1134
575	IO::AIO::poll_wait, IO::AIO::poll_cb	1135	IO::AIO::poll_wait, IO::AIO::poll_cb
576	while IO::AIO::nreqs;	1136	while IO::AIO::nreqs;
577		1137
578	=item IO::AIO::flush	1138	=back
579		1139
580	Wait till all outstanding AIO requests have been handled.	1140	=head3 CONTROLLING THE NUMBER OF THREADS
581		1141
582	Strictly equivalent to:	1142	=over
583
584	IO::AIO::poll_wait, IO::AIO::poll_cb
585	while IO::AIO::nreqs;
586
587	=item IO::AIO::poll
588
589	Waits until some requests have been handled.
590
591	Strictly equivalent to:
592
593	IO::AIO::poll_wait, IO::AIO::poll_cb
594	if IO::AIO::nreqs;
595		1143
596	=item IO::AIO::min_parallel $nthreads	1144	=item IO::AIO::min_parallel $nthreads
597		1145
598	Set the minimum number of AIO threads to C<$nthreads>. The current default	1146	Set the minimum number of AIO threads to C<$nthreads>. The current
599	is C<4>, which means four asynchronous operations can be done at one time	1147	default is C<8>, which means eight asynchronous operations can execute
600	(the number of outstanding operations, however, is unlimited).	1148	concurrently at any one time (the number of outstanding requests,
		1149	however, is unlimited).
601		1150
602	IO::AIO starts threads only on demand, when an AIO request is queued and	1151	IO::AIO starts threads only on demand, when an AIO request is queued and
603	no free thread exists.	1152	no free thread exists. Please note that queueing up a hundred requests can
		1153	create demand for a hundred threads, even if it turns out that everything
		1154	is in the cache and could have been processed faster by a single thread.
604		1155
605	It is recommended to keep the number of threads low, as some Linux	1156	It is recommended to keep the number of threads relatively low, as some
606	kernel versions will scale negatively with the number of threads (higher	1157	Linux kernel versions will scale negatively with the number of threads
607	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1158	(higher parallelity => MUCH higher latency). With current Linux 2.6
608	threads should be fine.	1159	versions, 4-32 threads should be fine.
609		1160
610	Under most circumstances you don't need to call this function, as the	1161	Under most circumstances you don't need to call this function, as the
611	module selects a default that is suitable for low to moderate load.	1162	module selects a default that is suitable for low to moderate load.
612		1163
613	=item IO::AIO::max_parallel $nthreads	1164	=item IO::AIO::max_parallel $nthreads
…		…
622	This module automatically runs C<max_parallel 0> at program end, to ensure	1173	This module automatically runs C<max_parallel 0> at program end, to ensure
623	that all threads are killed and that there are no outstanding requests.	1174	that all threads are killed and that there are no outstanding requests.
624		1175
625	Under normal circumstances you don't need to call this function.	1176	Under normal circumstances you don't need to call this function.
626		1177
		1178	=item IO::AIO::max_idle $nthreads
		1179
		1180	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1181	threads that did not get a request to process within 10 seconds). That
		1182	means if a thread becomes idle while C<$nthreads> other threads are also
		1183	idle, it will free its resources and exit.
		1184
		1185	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1186	to allow for extremely high load situations, but want to free resources
		1187	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1188
		1189	The default is probably ok in most situations, especially if thread
		1190	creation is fast. If thread creation is very slow on your system you might
		1191	want to use larger values.
		1192
627	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1193	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1194
		1195	This is a very bad function to use in interactive programs because it
		1196	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1197	use an C<aio_group> together with a feed callback.
628		1198
629	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1199	Sets the maximum number of outstanding requests to C<$nreqs>. If you
630	try to queue up more than this number of requests, the caller will block until	1200	to queue up more than this number of requests, the next call to the
631	some requests have been handled.	1201	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1202	function will block until the limit is no longer exceeded.
632		1203
633	The default is very large, so normally there is no practical limit. If you	1204	The default value is very large, so there is no practical limit on the
634	queue up many requests in a loop it often improves speed if you set	1205	number of outstanding requests.
635	this to a relatively low number, such as C<100>.
636		1206
637	Under normal circumstances you don't need to call this function.	1207	You can still queue as many requests as you want. Therefore,
		1208	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1209	as a stop gap to shield against fatal memory overflow (with large values).
		1210
		1211	=back
		1212
		1213	=head3 STATISTICAL INFORMATION
		1214
		1215	=over
		1216
		1217	=item IO::AIO::nreqs
		1218
		1219	Returns the number of requests currently in the ready, execute or pending
		1220	states (i.e. for which their callback has not been invoked yet).
		1221
		1222	Example: wait till there are no outstanding requests anymore:
		1223
		1224	IO::AIO::poll_wait, IO::AIO::poll_cb
		1225	while IO::AIO::nreqs;
		1226
		1227	=item IO::AIO::nready
		1228
		1229	Returns the number of requests currently in the ready state (not yet
		1230	executed).
		1231
		1232	=item IO::AIO::npending
		1233
		1234	Returns the number of requests currently in the pending state (executed,
		1235	but not yet processed by poll_cb).
638		1236
639	=back	1237	=back
640		1238
641	=cut	1239	=cut
642		1240
…		…
654	or return undef;	1252	or return undef;
655		1253
656	*$sym	1254	*$sym
657	}	1255	}
658		1256
659	min_parallel 4;	1257	min_parallel 8;
660		1258
661	END {	1259	END { flush }
662	max_parallel 0;
663	}
664		1260
665	1;	1261	1;
666		1262
667	=head2 FORK BEHAVIOUR	1263	=head2 FORK BEHAVIOUR
668		1264
669	This module should do "the right thing" when the process using it forks:	1265	This module should do "the right thing" when the process using it forks:
670		1266
671	Before the fork, IO::AIO enters a quiescent state where no requests	1267	Before the fork, IO::AIO enters a quiescent state where no requests
672	can be added in other threads and no results will be processed. After	1268	can be added in other threads and no results will be processed. After
673	the fork the parent simply leaves the quiescent state and continues	1269	the fork the parent simply leaves the quiescent state and continues
674	request/result processing, while the child clears the request/result	1270	request/result processing, while the child frees the request/result queue
675	queue (so the requests started before the fork will only be handled in	1271	(so that the requests started before the fork will only be handled in the
676	the parent). Threads will be started on demand until the limit ste in the	1272	parent). Threads will be started on demand until the limit set in the
677	parent process has been reached again.	1273	parent process has been reached again.
678		1274
679	In short: the parent will, after a short pause, continue as if fork had	1275	In short: the parent will, after a short pause, continue as if fork had
680	not been called, while the child will act as if IO::AIO has not been used	1276	not been called, while the child will act as if IO::AIO has not been used
681	yet.	1277	yet.
682		1278
		1279	=head2 MEMORY USAGE
		1280
		1281	Per-request usage:
		1282
		1283	Each aio request uses - depending on your architecture - around 100-200
		1284	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1285	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1286	scalars and other data passed into aio requests will also be locked and
		1287	will consume memory till the request has entered the done state.
		1288
		1289	This is now awfully much, so queuing lots of requests is not usually a
		1290	problem.
		1291
		1292	Per-thread usage:
		1293
		1294	In the execution phase, some aio requests require more memory for
		1295	temporary buffers, and each thread requires a stack and other data
		1296	structures (usually around 16k-128k, depending on the OS).
		1297
		1298	=head1 KNOWN BUGS
		1299
		1300	Known bugs will be fixed in the next release.
		1301
683	=head1 SEE ALSO	1302	=head1 SEE ALSO
684		1303
685	L<Coro>, L<Linux::AIO> (obsolete).	1304	L<Coro::AIO>.
686		1305
687	=head1 AUTHOR	1306	=head1 AUTHOR
688		1307
689	Marc Lehmann <schmorp@schmorp.de>	1308	Marc Lehmann <schmorp@schmorp.de>
690	http://home.schmorp.de/	1309	http://home.schmorp.de/

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