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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 1.111 by root, Mon Aug 13 12:08:13 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 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);
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<$dataoffset> and calls the
168	callback without the actual number of bytes read (or -1 on error, just	331	callback without the actual number of bytes read (or -1 on error, just
169	like the syscall).	332	like the syscall).
170		333
		334	If C<$offset> is undefined, then the current file offset will be used (and
		335	updated), otherwise the file offset will not be changed by these calls.
		336
		337	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		338
		339	If C<$dataoffset> is less than zero, it will be counted from the end of
		340	C<$data>.
		341
171	The C<$data> scalar I<MUST NOT> be modified in any way while the request	342	The C<$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	343	is outstanding. Modifying it can result in segfaults or World War III (if
173	necessary/optional hardware is installed).	344	the necessary/optional hardware is installed).
174		345
175	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	346	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
176	offset C<0> within the scalar:	347	offset C<0> within the scalar:
177		348
178	aio_read $fh, 7, 15, $buffer, 0, sub {	349	aio_read $fh, 7, 15, $buffer, 0, sub {
179	$_[0] > 0 or die "read error: $!";	350	$_[0] > 0 or die "read error: $!";
180	print "read $_[0] bytes: <$buffer>\n";	351	print "read $_[0] bytes: <$buffer>\n";
181	};	352	};
182		353
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		354
247	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	355	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
248		356
249	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	357	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	358	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	372	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	373	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	374	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	375	value equals C<$length> one can assume that C<$length> bytes have been
268	read.	376	read.
		377
269		378
270	=item aio_readahead $fh,$offset,$length, $callback->($retval)	379	=item aio_readahead $fh,$offset,$length, $callback->($retval)
271		380
272	C<aio_readahead> populates the page cache with data from a file so that	381	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>	382	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.	388	file. The current file offset of the file is left unchanged.
280		389
281	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	390	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.	391	emulated by simply reading the data, which would have a similar effect.
283		392
		393
284	=item aio_stat $fh_or_path, $callback->($status)	394	=item aio_stat $fh_or_path, $callback->($status)
285		395
286	=item aio_lstat $fh, $callback->($status)	396	=item aio_lstat $fh, $callback->($status)
287		397
288	Works like perl's C<stat> or C<lstat> in void context. The callback will	398	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
301	aio_stat "/etc/passwd", sub {	411	aio_stat "/etc/passwd", sub {
302	$_[0] and die "stat failed: $!";	412	$_[0] and die "stat failed: $!";
303	print "size is ", -s _, "\n";	413	print "size is ", -s _, "\n";
304	};	414	};
305		415
		416
		417	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		418
		419	Works like perl's C<utime> function (including the special case of $atime
		420	and $mtime being undef). Fractional times are supported if the underlying
		421	syscalls support them.
		422
		423	When called with a pathname, uses utimes(2) if available, otherwise
		424	utime(2). If called on a file descriptor, uses futimes(2) if available,
		425	otherwise returns ENOSYS, so this is not portable.
		426
		427	Examples:
		428
		429	# set atime and mtime to current time (basically touch(1)):
		430	aio_utime "path", undef, undef;
		431	# set atime to current time and mtime to beginning of the epoch:
		432	aio_utime "path", time, undef; # undef==0
		433
		434
		435	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		436
		437	Works like perl's C<chown> function, except that C<undef> for either $uid
		438	or $gid is being interpreted as "do not change" (but -1 can also be used).
		439
		440	Examples:
		441
		442	# same as "chown root path" in the shell:
		443	aio_chown "path", 0, -1;
		444	# same as above:
		445	aio_chown "path", 0, undef;
		446
		447
		448	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		449
		450	Works like truncate(2) or ftruncate(2).
		451
		452
		453	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		454
		455	Works like perl's C<chmod> function.
		456
		457
306	=item aio_unlink $pathname, $callback->($status)	458	=item aio_unlink $pathname, $callback->($status)
307		459
308	Asynchronously unlink (delete) a file and call the callback with the	460	Asynchronously unlink (delete) a file and call the callback with the
309	result code.	461	result code.
310		462
		463
		464	=item aio_mknod $path, $mode, $dev, $callback->($status)
		465
		466	[EXPERIMENTAL]
		467
		468	Asynchronously create a device node (or fifo). See mknod(2).
		469
		470	The only (POSIX-) portable way of calling this function is:
		471
		472	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		473
		474
311	=item aio_link $srcpath, $dstpath, $callback->($status)	475	=item aio_link $srcpath, $dstpath, $callback->($status)
312		476
313	Asynchronously create a new link to the existing object at C<$srcpath> at	477	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.	478	the path C<$dstpath> and call the callback with the result code.
315		479
		480
316	=item aio_symlink $srcpath, $dstpath, $callback->($status)	481	=item aio_symlink $srcpath, $dstpath, $callback->($status)
317		482
318	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	483	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.	484	the path C<$dstpath> and call the callback with the result code.
320		485
		486
		487	=item aio_readlink $path, $callback->($link)
		488
		489	Asynchronously read the symlink specified by C<$path> and pass it to
		490	the callback. If an error occurs, nothing or undef gets passed to the
		491	callback.
		492
		493
321	=item aio_rename $srcpath, $dstpath, $callback->($status)	494	=item aio_rename $srcpath, $dstpath, $callback->($status)
322		495
323	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	496	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
324	rename(2) and call the callback with the result code.	497	rename(2) and call the callback with the result code.
325		498
		499
		500	=item aio_mkdir $pathname, $mode, $callback->($status)
		501
		502	Asynchronously mkdir (create) a directory and call the callback with
		503	the result code. C<$mode> will be modified by the umask at the time the
		504	request is executed, so do not change your umask.
		505
		506
326	=item aio_rmdir $pathname, $callback->($status)	507	=item aio_rmdir $pathname, $callback->($status)
327		508
328	Asynchronously rmdir (delete) a directory and call the callback with the	509	Asynchronously rmdir (delete) a directory and call the callback with the
329	result code.	510	result code.
		511
330		512
331	=item aio_readdir $pathname, $callback->($entries)	513	=item aio_readdir $pathname, $callback->($entries)
332		514
333	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	515	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	516	directory (i.e. opendir + readdir + closedir). The entries will not be
335	sorted, and will B<NOT> include the C<.> and C<..> entries.	517	sorted, and will B<NOT> include the C<.> and C<..> entries.
336		518
337	The callback a single argument which is either C<undef> or an array-ref	519	The callback a single argument which is either C<undef> or an array-ref
338	with the filenames.	520	with the filenames.
339		521
		522
		523	=item aio_load $path, $data, $callback->($status)
		524
		525	This is a composite request that tries to fully load the given file into
		526	memory. Status is the same as with aio_read.
		527
		528	=cut
		529
		530	sub aio_load($$;$) {
		531	aio_block {
		532	my ($path, undef, $cb) = @_;
		533	my $data = \$_[1];
		534
		535	my $pri = aioreq_pri;
		536	my $grp = aio_group $cb;
		537
		538	aioreq_pri $pri;
		539	add $grp aio_open $path, O_RDONLY, 0, sub {
		540	my $fh = shift
		541	or return $grp->result (-1);
		542
		543	aioreq_pri $pri;
		544	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		545	$grp->result ($_[0]);
		546	};
		547	};
		548
		549	$grp
		550	}
		551	}
		552
		553	=item aio_copy $srcpath, $dstpath, $callback->($status)
		554
		555	Try to copy the I<file> (directories not supported as either source or
		556	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		557	the C<0> (error) or C<-1> ok.
		558
		559	This is a composite request that it creates the destination file with
		560	mode 0200 and copies the contents of the source file into it using
		561	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		562	uid/gid, in that order.
		563
		564	If an error occurs, the partial destination file will be unlinked, if
		565	possible, except when setting atime, mtime, access mode and uid/gid, where
		566	errors are being ignored.
		567
		568	=cut
		569
		570	sub aio_copy($$;$) {
		571	aio_block {
		572	my ($src, $dst, $cb) = @_;
		573
		574	my $pri = aioreq_pri;
		575	my $grp = aio_group $cb;
		576
		577	aioreq_pri $pri;
		578	add $grp aio_open $src, O_RDONLY, 0, sub {
		579	if (my $src_fh = $_[0]) {
		580	my @stat = stat $src_fh;
		581
		582	aioreq_pri $pri;
		583	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		584	if (my $dst_fh = $_[0]) {
		585	aioreq_pri $pri;
		586	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		587	if ($_[0] == $stat[7]) {
		588	$grp->result (0);
		589	close $src_fh;
		590
		591	# those should not normally block. should. should.
		592	utime $stat[8], $stat[9], $dst;
		593	chmod $stat[2] & 07777, $dst_fh;
		594	chown $stat[4], $stat[5], $dst_fh;
		595	close $dst_fh;
		596	} else {
		597	$grp->result (-1);
		598	close $src_fh;
		599	close $dst_fh;
		600
		601	aioreq $pri;
		602	add $grp aio_unlink $dst;
		603	}
		604	};
		605	} else {
		606	$grp->result (-1);
		607	}
		608	},
		609
		610	} else {
		611	$grp->result (-1);
		612	}
		613	};
		614
		615	$grp
		616	}
		617	}
		618
		619	=item aio_move $srcpath, $dstpath, $callback->($status)
		620
		621	Try to move the I<file> (directories not supported as either source or
		622	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		623	the C<0> (error) or C<-1> ok.
		624
		625	This is a composite request that tries to rename(2) the file first. If
		626	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		627	that is successful, unlinking the C<$srcpath>.
		628
		629	=cut
		630
		631	sub aio_move($$;$) {
		632	aio_block {
		633	my ($src, $dst, $cb) = @_;
		634
		635	my $pri = aioreq_pri;
		636	my $grp = aio_group $cb;
		637
		638	aioreq_pri $pri;
		639	add $grp aio_rename $src, $dst, sub {
		640	if ($_[0] && $! == EXDEV) {
		641	aioreq_pri $pri;
		642	add $grp aio_copy $src, $dst, sub {
		643	$grp->result ($_[0]);
		644
		645	if (!$_[0]) {
		646	aioreq_pri $pri;
		647	add $grp aio_unlink $src;
		648	}
		649	};
		650	} else {
		651	$grp->result ($_[0]);
		652	}
		653	};
		654
		655	$grp
		656	}
		657	}
		658
340	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	659	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
341		660
342	Scans a directory (similar to C<aio_readdir>) but additionally tries to	661	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	662	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	663	names, directories you can recurse into (directories), and ones you cannot
345	recurse into (everything else).	664	recurse into (everything else, including symlinks to directories).
346		665
347	C<aio_scandir> is a composite request that consists of many sub	666	C<aio_scandir> is a composite request that creates of many sub requests_
348	requests. C<$maxreq> specifies the maximum number of outstanding aio	667	C<$maxreq> specifies the maximum number of outstanding aio requests that
349	requests that this function generates. If it is C<< <= 0 >>, then a	668	this function generates. If it is C<< <= 0 >>, then a suitable default
350	suitable default will be chosen (currently 8).	669	will be chosen (currently 4).
351		670
352	On error, the callback is called without arguments, otherwise it receives	671	On error, the callback is called without arguments, otherwise it receives
353	two array-refs with path-relative entry names.	672	two array-refs with path-relative entry names.
354		673
355	Example:	674	Example:
…		…
389	as those tend to return 0 or 1 as link counts, which disables the	708	as those tend to return 0 or 1 as link counts, which disables the
390	directory counting heuristic.	709	directory counting heuristic.
391		710
392	=cut	711	=cut
393		712
394	sub aio_scandir($$$) {	713	sub aio_scandir($$;$) {
		714	aio_block {
395	my ($path, $maxreq, $cb) = @_;	715	my ($path, $maxreq, $cb) = @_;
396		716
		717	my $pri = aioreq_pri;
		718
		719	my $grp = aio_group $cb;
		720
397	$maxreq = 8 if $maxreq <= 0;	721	$maxreq = 4 if $maxreq <= 0;
398		722
399	# stat once	723	# stat once
		724	aioreq_pri $pri;
400	aio_stat $path, sub {	725	add $grp aio_stat $path, sub {
401	return $cb->() if $_[0];	726	return $grp->result () if $_[0];
402	my $now = time;	727	my $now = time;
403	my $hash1 = join ":", (stat _)[0,1,3,7,9];	728	my $hash1 = join ":", (stat _)[0,1,3,7,9];
404		729
405	# read the directory entries	730	# read the directory entries
		731	aioreq_pri $pri;
406	aio_readdir $path, sub {	732	add $grp aio_readdir $path, sub {
407	my $entries = shift	733	my $entries = shift
408	or return $cb->();	734	or return $grp->result ();
409		735
410	# stat the dir another time	736	# stat the dir another time
		737	aioreq_pri $pri;
411	aio_stat $path, sub {	738	add $grp aio_stat $path, sub {
412	my $hash2 = join ":", (stat _)[0,1,3,7,9];	739	my $hash2 = join ":", (stat _)[0,1,3,7,9];
413		740
414	my $ndirs;	741	my $ndirs;
415		742
416	# take the slow route if anything looks fishy	743	# take the slow route if anything looks fishy
417	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	744	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
418	$ndirs = -1;	745	$ndirs = -1;
419	} else {	746	} else {
420	# if nlink == 2, we are finished	747	# if nlink == 2, we are finished
421	# on non-posix-fs's, we rely on nlink < 2	748	# on non-posix-fs's, we rely on nlink < 2
422	$ndirs = (stat _)[3] - 2	749	$ndirs = (stat _)[3] - 2
423	or return $cb->([], $entries);	750	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	}	751	}
		752
		753	# sort into likely dirs and likely nondirs
		754	# dirs == files without ".", short entries first
		755	$entries = [map $_->[0],
		756	sort { $b->[1] cmp $a->[1] }
		757	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		758	@$entries];
		759
		760	my (@dirs, @nondirs);
		761
		762	my $statgrp = add $grp aio_group sub {
		763	$grp->result (\@dirs, \@nondirs);
		764	};
		765
		766	limit $statgrp $maxreq;
		767	feed $statgrp sub {
		768	return unless @$entries;
		769	my $entry = pop @$entries;
		770
		771	aioreq_pri $pri;
		772	add $statgrp aio_stat "$path/$entry/.", sub {
		773	if ($_[0] < 0) {
		774	push @nondirs, $entry;
		775	} else {
		776	# need to check for real directory
		777	aioreq_pri $pri;
		778	add $statgrp aio_lstat "$path/$entry", sub {
		779	if (-d _) {
		780	push @dirs, $entry;
		781
		782	unless (--$ndirs) {
		783	push @nondirs, @$entries;
		784	feed $statgrp;
		785	}
		786	} else {
		787	push @nondirs, $entry;
		788	}
		789	}
		790	}
		791	};
		792	};
452	};	793	};
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	};	794	};
483	};	795	};
		796
		797	$grp
484	};	798	}
		799	}
		800
		801	=item aio_rmtree $path, $callback->($status)
		802
		803	Delete a directory tree starting (and including) C<$path>, return the
		804	status of the final C<rmdir> only. This is a composite request that
		805	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		806	everything else.
		807
		808	=cut
		809
		810	sub aio_rmtree;
		811	sub aio_rmtree($;$) {
		812	aio_block {
		813	my ($path, $cb) = @_;
		814
		815	my $pri = aioreq_pri;
		816	my $grp = aio_group $cb;
		817
		818	aioreq_pri $pri;
		819	add $grp aio_scandir $path, 0, sub {
		820	my ($dirs, $nondirs) = @_;
		821
		822	my $dirgrp = aio_group sub {
		823	add $grp aio_rmdir $path, sub {
		824	$grp->result ($_[0]);
		825	};
		826	};
		827
		828	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		829	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		830
		831	add $grp $dirgrp;
		832	};
		833
		834	$grp
		835	}
485	}	836	}
486		837
487	=item aio_fsync $fh, $callback->($status)	838	=item aio_fsync $fh, $callback->($status)
488		839
489	Asynchronously call fsync on the given filehandle and call the callback	840	Asynchronously call fsync on the given filehandle and call the callback
…		…
495	callback with the fdatasync result code.	846	callback with the fdatasync result code.
496		847
497	If this call isn't available because your OS lacks it or it couldn't be	848	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.	849	detected, it will be emulated by calling C<fsync> instead.
499		850
500	=item aio_group $callback->()	851	=item aio_group $callback->(...)
501		852
		853	This is a very special aio request: Instead of doing something, it is a
		854	container for other aio requests, which is useful if you want to bundle
		855	many requests into a single, composite, request with a definite callback
		856	and the ability to cancel the whole request with its subrequests.
		857
		858	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		859	for more info.
		860
		861	Example:
		862
		863	my $grp = aio_group sub {
		864	print "all stats done\n";
		865	};
		866
		867	add $grp
		868	(aio_stat ...),
		869	(aio_stat ...),
		870	...;
		871
		872	=item aio_nop $callback->()
		873
		874	This is a special request - it does nothing in itself and is only used for
		875	side effects, such as when you want to add a dummy request to a group so
		876	that finishing the requests in the group depends on executing the given
		877	code.
		878
		879	While this request does nothing, it still goes through the execution
		880	phase and still requires a worker thread. Thus, the callback will not
		881	be executed immediately but only after other requests in the queue have
		882	entered their execution phase. This can be used to measure request
		883	latency.
		884
502	=item aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	885	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
503		886
504	Mainly used for debugging and benchmarking, this aio request puts one of	887	Mainly used for debugging and benchmarking, this aio request puts one of
505	the request workers to sleep for the given time.	888	the request workers to sleep for the given time.
506		889
		890	While it is theoretically handy to have simple I/O scheduling requests
		891	like sleep and file handle readable/writable, the overhead this creates is
		892	immense (it blocks a thread for a long time) so do not use this function
		893	except to put your application under artificial I/O pressure.
		894
507	=back	895	=back
508		896
509	=head2 IO::AIO::REQ CLASS	897	=head2 IO::AIO::REQ CLASS
510		898
511	All non-aggregate C<aio_*> functions return an object of this class when	899	All non-aggregate C<aio_*> functions return an object of this class when
512	called in non-void context.	900	called in non-void context.
513		901
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	902	=over 4
523		903
524	=item $req->cancel	904	=item cancel $req
525		905
526	Cancels the request, if possible. Has the effect of skipping execution	906	Cancels the request, if possible. Has the effect of skipping execution
527	when entering the B<execute> state and skipping calling the callback when	907	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	908	entering the the B<result> state, but will leave the request otherwise
529	untouched. That means that requests that currently execute will not be	909	untouched. That means that requests that currently execute will not be
530	stopped and resources held by the request will not be freed prematurely.	910	stopped and resources held by the request will not be freed prematurely.
531		911
		912	=item cb $req $callback->(...)
		913
		914	Replace (or simply set) the callback registered to the request.
		915
532	=back	916	=back
533		917
		918	=head2 IO::AIO::GRP CLASS
		919
		920	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		921	objects of this class, too.
		922
		923	A IO::AIO::GRP object is a special request that can contain multiple other
		924	aio requests.
		925
		926	You create one by calling the C<aio_group> constructing function with a
		927	callback that will be called when all contained requests have entered the
		928	C<done> state:
		929
		930	my $grp = aio_group sub {
		931	print "all requests are done\n";
		932	};
		933
		934	You add requests by calling the C<add> method with one or more
		935	C<IO::AIO::REQ> objects:
		936
		937	$grp->add (aio_unlink "...");
		938
		939	add $grp aio_stat "...", sub {
		940	$_[0] or return $grp->result ("error");
		941
		942	# add another request dynamically, if first succeeded
		943	add $grp aio_open "...", sub {
		944	$grp->result ("ok");
		945	};
		946	};
		947
		948	This makes it very easy to create composite requests (see the source of
		949	C<aio_move> for an application) that work and feel like simple requests.
		950
		951	=over 4
		952
		953	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		954	C<IO::AIO::poll_cb>, just like any other request.
		955
		956	=item * They can be canceled like any other request. Canceling will cancel not
		957	only the request itself, but also all requests it contains.
		958
		959	=item * They can also can also be added to other IO::AIO::GRP objects.
		960
		961	=item * You must not add requests to a group from within the group callback (or
		962	any later time).
		963
		964	=back
		965
		966	Their lifetime, simplified, looks like this: when they are empty, they
		967	will finish very quickly. If they contain only requests that are in the
		968	C<done> state, they will also finish. Otherwise they will continue to
		969	exist.
		970
		971	That means after creating a group you have some time to add requests. And
		972	in the callbacks of those requests, you can add further requests to the
		973	group. And only when all those requests have finished will the the group
		974	itself finish.
		975
		976	=over 4
		977
		978	=item add $grp ...
		979
		980	=item $grp->add (...)
		981
		982	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		983	be added, including other groups, as long as you do not create circular
		984	dependencies.
		985
		986	Returns all its arguments.
		987
		988	=item $grp->cancel_subs
		989
		990	Cancel all subrequests and clears any feeder, but not the group request
		991	itself. Useful when you queued a lot of events but got a result early.
		992
		993	=item $grp->result (...)
		994
		995	Set the result value(s) that will be passed to the group callback when all
		996	subrequests have finished and set thre groups errno to the current value
		997	of errno (just like calling C<errno> without an error number). By default,
		998	no argument will be passed and errno is zero.
		999
		1000	=item $grp->errno ([$errno])
		1001
		1002	Sets the group errno value to C<$errno>, or the current value of errno
		1003	when the argument is missing.
		1004
		1005	Every aio request has an associated errno value that is restored when
		1006	the callback is invoked. This method lets you change this value from its
		1007	default (0).
		1008
		1009	Calling C<result> will also set errno, so make sure you either set C<$!>
		1010	before the call to C<result>, or call c<errno> after it.
		1011
		1012	=item feed $grp $callback->($grp)
		1013
		1014	Sets a feeder/generator on this group: every group can have an attached
		1015	generator that generates requests if idle. The idea behind this is that,
		1016	although you could just queue as many requests as you want in a group,
		1017	this might starve other requests for a potentially long time. For
		1018	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1019	requests, delaying any later requests for a long time.
		1020
		1021	To avoid this, and allow incremental generation of requests, you can
		1022	instead a group and set a feeder on it that generates those requests. The
		1023	feed callback will be called whenever there are few enough (see C<limit>,
		1024	below) requests active in the group itself and is expected to queue more
		1025	requests.
		1026
		1027	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1028	not impose any limits).
		1029
		1030	If the feed does not queue more requests when called, it will be
		1031	automatically removed from the group.
		1032
		1033	If the feed limit is C<0>, it will be set to C<2> automatically.
		1034
		1035	Example:
		1036
		1037	# stat all files in @files, but only ever use four aio requests concurrently:
		1038
		1039	my $grp = aio_group sub { print "finished\n" };
		1040	limit $grp 4;
		1041	feed $grp sub {
		1042	my $file = pop @files
		1043	or return;
		1044
		1045	add $grp aio_stat $file, sub { ... };
		1046	};
		1047
		1048	=item limit $grp $num
		1049
		1050	Sets the feeder limit for the group: The feeder will be called whenever
		1051	the group contains less than this many requests.
		1052
		1053	Setting the limit to C<0> will pause the feeding process.
		1054
		1055	=back
		1056
534	=head2 SUPPORT FUNCTIONS	1057	=head2 SUPPORT FUNCTIONS
		1058
		1059	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
535		1060
536	=over 4	1061	=over 4
537		1062
538	=item $fileno = IO::AIO::poll_fileno	1063	=item $fileno = IO::AIO::poll_fileno
539		1064
…		…
544		1069
545	See C<poll_cb> for an example.	1070	See C<poll_cb> for an example.
546		1071
547	=item IO::AIO::poll_cb	1072	=item IO::AIO::poll_cb
548		1073
549	Process all outstanding events on the result pipe. You have to call this	1074	Process some outstanding events on the result pipe. You have to call this
550	regularly. Returns the number of events processed. Returns immediately	1075	regularly. Returns the number of events processed. Returns immediately
551	when no events are outstanding.	1076	when no events are outstanding. The amount of events processed depends on
		1077	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1078
		1079	If not all requests were processed for whatever reason, the filehandle
		1080	will still be ready when C<poll_cb> returns.
552		1081
553	Example: Install an Event watcher that automatically calls	1082	Example: Install an Event watcher that automatically calls
554	IO::AIO::poll_cb with high priority:	1083	IO::AIO::poll_cb with high priority:
555		1084
556	Event->io (fd => IO::AIO::poll_fileno,	1085	Event->io (fd => IO::AIO::poll_fileno,
557	poll => 'r', async => 1,	1086	poll => 'r', async => 1,
558	cb => \&IO::AIO::poll_cb);	1087	cb => \&IO::AIO::poll_cb);
559		1088
		1089	=item IO::AIO::max_poll_reqs $nreqs
		1090
		1091	=item IO::AIO::max_poll_time $seconds
		1092
		1093	These set the maximum number of requests (default C<0>, meaning infinity)
		1094	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1095	the maximum amount of time (default C<0>, meaning infinity) spent in
		1096	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1097	of time C<poll_cb> is allowed to use).
		1098
		1099	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1100	syscall per request processed, which is not normally a problem unless your
		1101	callbacks are really really fast or your OS is really really slow (I am
		1102	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1103
		1104	Setting these is useful if you want to ensure some level of
		1105	interactiveness when perl is not fast enough to process all requests in
		1106	time.
		1107
		1108	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1109
		1110	Example: Install an Event watcher that automatically calls
		1111	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1112	program get the CPU sometimes even under high AIO load.
		1113
		1114	# try not to spend much more than 0.1s in poll_cb
		1115	IO::AIO::max_poll_time 0.1;
		1116
		1117	# use a low priority so other tasks have priority
		1118	Event->io (fd => IO::AIO::poll_fileno,
		1119	poll => 'r', nice => 1,
		1120	cb => &IO::AIO::poll_cb);
		1121
560	=item IO::AIO::poll_wait	1122	=item IO::AIO::poll_wait
561		1123
		1124	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	1125	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	1126	does a C<select> on the filehandle. This is useful if you want to
564	for some requests to finish).	1127	synchronously wait for some requests to finish).
565		1128
566	See C<nreqs> for an example.	1129	See C<nreqs> for an example.
567		1130
		1131	=item IO::AIO::poll
		1132
		1133	Waits until some requests have been handled.
		1134
		1135	Returns the number of requests processed, but is otherwise strictly
		1136	equivalent to:
		1137
		1138	IO::AIO::poll_wait, IO::AIO::poll_cb
		1139
568	=item IO::AIO::nreqs	1140	=item IO::AIO::flush
569		1141
570	Returns the number of requests currently outstanding (i.e. for which their	1142	Wait till all outstanding AIO requests have been handled.
571	callback has not been invoked yet).
572		1143
573	Example: wait till there are no outstanding requests anymore:	1144	Strictly equivalent to:
574		1145
575	IO::AIO::poll_wait, IO::AIO::poll_cb	1146	IO::AIO::poll_wait, IO::AIO::poll_cb
576	while IO::AIO::nreqs;	1147	while IO::AIO::nreqs;
577		1148
578	=item IO::AIO::flush	1149	=back
579		1150
580	Wait till all outstanding AIO requests have been handled.	1151	=head3 CONTROLLING THE NUMBER OF THREADS
581		1152
582	Strictly equivalent to:	1153	=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		1154
596	=item IO::AIO::min_parallel $nthreads	1155	=item IO::AIO::min_parallel $nthreads
597		1156
598	Set the minimum number of AIO threads to C<$nthreads>. The current default	1157	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	1158	default is C<8>, which means eight asynchronous operations can execute
600	(the number of outstanding operations, however, is unlimited).	1159	concurrently at any one time (the number of outstanding requests,
		1160	however, is unlimited).
601		1161
602	IO::AIO starts threads only on demand, when an AIO request is queued and	1162	IO::AIO starts threads only on demand, when an AIO request is queued and
603	no free thread exists.	1163	no free thread exists. Please note that queueing up a hundred requests can
		1164	create demand for a hundred threads, even if it turns out that everything
		1165	is in the cache and could have been processed faster by a single thread.
604		1166
605	It is recommended to keep the number of threads low, as some Linux	1167	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	1168	Linux kernel versions will scale negatively with the number of threads
607	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1169	(higher parallelity => MUCH higher latency). With current Linux 2.6
608	threads should be fine.	1170	versions, 4-32 threads should be fine.
609		1171
610	Under most circumstances you don't need to call this function, as the	1172	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.	1173	module selects a default that is suitable for low to moderate load.
612		1174
613	=item IO::AIO::max_parallel $nthreads	1175	=item IO::AIO::max_parallel $nthreads
…		…
622	This module automatically runs C<max_parallel 0> at program end, to ensure	1184	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.	1185	that all threads are killed and that there are no outstanding requests.
624		1186
625	Under normal circumstances you don't need to call this function.	1187	Under normal circumstances you don't need to call this function.
626		1188
		1189	=item IO::AIO::max_idle $nthreads
		1190
		1191	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1192	threads that did not get a request to process within 10 seconds). That
		1193	means if a thread becomes idle while C<$nthreads> other threads are also
		1194	idle, it will free its resources and exit.
		1195
		1196	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1197	to allow for extremely high load situations, but want to free resources
		1198	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1199
		1200	The default is probably ok in most situations, especially if thread
		1201	creation is fast. If thread creation is very slow on your system you might
		1202	want to use larger values.
		1203
627	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1204	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1205
		1206	This is a very bad function to use in interactive programs because it
		1207	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1208	use an C<aio_group> together with a feed callback.
628		1209
629	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1210	Sets the maximum number of outstanding requests to C<$nreqs>. If you
630	try to queue up more than this number of requests, the caller will block until	1211	to queue up more than this number of requests, the next call to the
631	some requests have been handled.	1212	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1213	function will block until the limit is no longer exceeded.
632		1214
633	The default is very large, so normally there is no practical limit. If you	1215	The default value is very large, so there is no practical limit on the
634	queue up many requests in a loop it often improves speed if you set	1216	number of outstanding requests.
635	this to a relatively low number, such as C<100>.
636		1217
637	Under normal circumstances you don't need to call this function.	1218	You can still queue as many requests as you want. Therefore,
		1219	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1220	as a stop gap to shield against fatal memory overflow (with large values).
		1221
		1222	=back
		1223
		1224	=head3 STATISTICAL INFORMATION
		1225
		1226	=over
		1227
		1228	=item IO::AIO::nreqs
		1229
		1230	Returns the number of requests currently in the ready, execute or pending
		1231	states (i.e. for which their callback has not been invoked yet).
		1232
		1233	Example: wait till there are no outstanding requests anymore:
		1234
		1235	IO::AIO::poll_wait, IO::AIO::poll_cb
		1236	while IO::AIO::nreqs;
		1237
		1238	=item IO::AIO::nready
		1239
		1240	Returns the number of requests currently in the ready state (not yet
		1241	executed).
		1242
		1243	=item IO::AIO::npending
		1244
		1245	Returns the number of requests currently in the pending state (executed,
		1246	but not yet processed by poll_cb).
638		1247
639	=back	1248	=back
640		1249
641	=cut	1250	=cut
642		1251
…		…
654	or return undef;	1263	or return undef;
655		1264
656	*$sym	1265	*$sym
657	}	1266	}
658		1267
659	min_parallel 4;	1268	min_parallel 8;
660		1269
661	END {	1270	END { flush }
662	max_parallel 0;
663	}
664		1271
665	1;	1272	1;
666		1273
667	=head2 FORK BEHAVIOUR	1274	=head2 FORK BEHAVIOUR
668		1275
669	This module should do "the right thing" when the process using it forks:	1276	This module should do "the right thing" when the process using it forks:
670		1277
671	Before the fork, IO::AIO enters a quiescent state where no requests	1278	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	1279	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	1280	the fork the parent simply leaves the quiescent state and continues
674	request/result processing, while the child clears the request/result	1281	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	1282	(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	1283	parent). Threads will be started on demand until the limit set in the
677	parent process has been reached again.	1284	parent process has been reached again.
678		1285
679	In short: the parent will, after a short pause, continue as if fork had	1286	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	1287	not been called, while the child will act as if IO::AIO has not been used
681	yet.	1288	yet.
682		1289
		1290	=head2 MEMORY USAGE
		1291
		1292	Per-request usage:
		1293
		1294	Each aio request uses - depending on your architecture - around 100-200
		1295	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1296	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1297	scalars and other data passed into aio requests will also be locked and
		1298	will consume memory till the request has entered the done state.
		1299
		1300	This is not awfully much, so queuing lots of requests is not usually a
		1301	problem.
		1302
		1303	Per-thread usage:
		1304
		1305	In the execution phase, some aio requests require more memory for
		1306	temporary buffers, and each thread requires a stack and other data
		1307	structures (usually around 16k-128k, depending on the OS).
		1308
		1309	=head1 KNOWN BUGS
		1310
		1311	Known bugs will be fixed in the next release.
		1312
683	=head1 SEE ALSO	1313	=head1 SEE ALSO
684		1314
685	L<Coro>, L<Linux::AIO> (obsolete).	1315	L<Coro::AIO>.
686		1316
687	=head1 AUTHOR	1317	=head1 AUTHOR
688		1318
689	Marc Lehmann <schmorp@schmorp.de>	1319	Marc Lehmann <schmorp@schmorp.de>
690	http://home.schmorp.de/	1320	http://home.schmorp.de/

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