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Revision 1.68 by root, Tue Oct 24 03:17:39 2006 UTC vs.
Revision 1.172 by root, Thu Jan 7 18:08:21 2010 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
…		…
25	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
26		27
27	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
28	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
29		30
		31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		32	use AnyEvent::AIO;
		33
30	# AnyEvent integration	34	# EV integration
31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	35	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
33		36
34	# Event integration	37	# Event integration
35	Event->io (fd => IO::AIO::poll_fileno,	38	Event->io (fd => IO::AIO::poll_fileno,
36	poll => 'r',	39	poll => 'r',
37	cb => \&IO::AIO::poll_cb);	40	cb => \&IO::AIO::poll_cb);
…		…
49	\&IO::AIO::poll_cb);	52	\&IO::AIO::poll_cb);
50		53
51	=head1 DESCRIPTION	54	=head1 DESCRIPTION
52		55
53	This module implements asynchronous I/O using whatever means your	56	This module implements asynchronous I/O using whatever means your
54	operating system supports.	57	operating system supports. It is implemented as an interface to C<libeio>
		58	(L<http://software.schmorp.de/pkg/libeio.html>).
55		59
		60	Asynchronous means that operations that can normally block your program
		61	(e.g. reading from disk) will be done asynchronously: the operation
		62	will still block, but you can do something else in the meantime. This
		63	is extremely useful for programs that need to stay interactive even
		64	when doing heavy I/O (GUI programs, high performance network servers
		65	etc.), but can also be used to easily do operations in parallel that are
		66	normally done sequentially, e.g. stat'ing many files, which is much faster
		67	on a RAID volume or over NFS when you do a number of stat operations
		68	concurrently.
		69
		70	While most of this works on all types of file descriptors (for
		71	example sockets), using these functions on file descriptors that
		72	support nonblocking operation (again, sockets, pipes etc.) is
		73	very inefficient. Use an event loop for that (such as the L<EV>
		74	module): IO::AIO will naturally fit into such an event loop itself.
		75
56	Currently, a number of threads are started that execute your read/writes	76	In this version, a number of threads are started that execute your
57	and signal their completion. You don't need thread support in perl, and	77	requests and signal their completion. You don't need thread support
58	the threads created by this module will not be visible to perl. In the	78	in perl, and the threads created by this module will not be visible
59	future, this module might make use of the native aio functions available	79	to perl. In the future, this module might make use of the native aio
60	on many operating systems. However, they are often not well-supported	80	functions available on many operating systems. However, they are often
61	(Linux doesn't allow them on normal files currently, for example),	81	not well-supported or restricted (GNU/Linux doesn't allow them on normal
62	and they would only support aio_read and aio_write, so the remaining	82	files currently, for example), and they would only support aio_read and
63	functionality would have to be implemented using threads anyway.	83	aio_write, so the remaining functionality would have to be implemented
		84	using threads anyway.
64		85
65	Although the module will work with in the presence of other threads,	86	Although the module will work in the presence of other (Perl-) threads,
66	it is currently not reentrant in any way, so use appropriate locking	87	it is currently not reentrant in any way, so use appropriate locking
67	yourself, always call C<poll_cb> from within the same thread, or never	88	yourself, always call C<poll_cb> from within the same thread, or never
68	call C<poll_cb> (or other C<aio_> functions) recursively.	89	call C<poll_cb> (or other C<aio_> functions) recursively.
69		90
		91	=head2 EXAMPLE
		92
		93	This is a simple example that uses the EV module and loads
		94	F</etc/passwd> asynchronously:
		95
		96	use Fcntl;
		97	use EV;
		98	use IO::AIO;
		99
		100	# register the IO::AIO callback with EV
		101	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		102
		103	# queue the request to open /etc/passwd
		104	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		105	my $fh = shift
		106	or die "error while opening: $!";
		107
		108	# stat'ing filehandles is generally non-blocking
		109	my $size = -s $fh;
		110
		111	# queue a request to read the file
		112	my $contents;
		113	aio_read $fh, 0, $size, $contents, 0, sub {
		114	$_[0] == $size
		115	or die "short read: $!";
		116
		117	close $fh;
		118
		119	# file contents now in $contents
		120	print $contents;
		121
		122	# exit event loop and program
		123	EV::unloop;
		124	};
		125	};
		126
		127	# possibly queue up other requests, or open GUI windows,
		128	# check for sockets etc. etc.
		129
		130	# process events as long as there are some:
		131	EV::loop;
		132
		133	=head1 REQUEST ANATOMY AND LIFETIME
		134
		135	Every C<aio_*> function creates a request. which is a C data structure not
		136	directly visible to Perl.
		137
		138	If called in non-void context, every request function returns a Perl
		139	object representing the request. In void context, nothing is returned,
		140	which saves a bit of memory.
		141
		142	The perl object is a fairly standard ref-to-hash object. The hash contents
		143	are not used by IO::AIO so you are free to store anything you like in it.
		144
		145	During their existance, aio requests travel through the following states,
		146	in order:
		147
		148	=over 4
		149
		150	=item ready
		151
		152	Immediately after a request is created it is put into the ready state,
		153	waiting for a thread to execute it.
		154
		155	=item execute
		156
		157	A thread has accepted the request for processing and is currently
		158	executing it (e.g. blocking in read).
		159
		160	=item pending
		161
		162	The request has been executed and is waiting for result processing.
		163
		164	While request submission and execution is fully asynchronous, result
		165	processing is not and relies on the perl interpreter calling C<poll_cb>
		166	(or another function with the same effect).
		167
		168	=item result
		169
		170	The request results are processed synchronously by C<poll_cb>.
		171
		172	The C<poll_cb> function will process all outstanding aio requests by
		173	calling their callbacks, freeing memory associated with them and managing
		174	any groups they are contained in.
		175
		176	=item done
		177
		178	Request has reached the end of its lifetime and holds no resources anymore
		179	(except possibly for the Perl object, but its connection to the actual
		180	aio request is severed and calling its methods will either do nothing or
		181	result in a runtime error).
		182
		183	=back
		184
70	=cut	185	=cut
71		186
72	package IO::AIO;	187	package IO::AIO;
73		188
74	no warnings;	189	use Carp ();
75	use strict 'vars';	190
		191	use common::sense;
76		192
77	use base 'Exporter';	193	use base 'Exporter';
78		194
79	BEGIN {	195	BEGIN {
80	our $VERSION = '2.0';	196	our $VERSION = '3.4';
81		197
82	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	198	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
83	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	199	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
84	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	200	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
85	aio_group aio_nop);	201	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
		202	aio_rename aio_link aio_move aio_copy aio_group
		203	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		204	aio_chmod aio_utime aio_truncate
		205	aio_msync aio_mtouch aio_statvfs);
		206
86	our @EXPORT = (@AIO_REQ, qw(aioreq_pri));	207	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
87	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	208	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
88	min_parallel max_parallel max_outstanding nreqs);	209	min_parallel max_parallel max_idle
		210	nreqs nready npending nthreads
		211	max_poll_time max_poll_reqs
		212	sendfile fadvise);
		213
		214	push @AIO_REQ, qw(aio_busy); # not exported
89		215
90	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	216	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
91		217
92	require XSLoader;	218	require XSLoader;
93	XSLoader::load ("IO::AIO", $VERSION);	219	XSLoader::load ("IO::AIO", $VERSION);
94	}	220	}
95		221
96	=head1 FUNCTIONS	222	=head1 FUNCTIONS
97		223
98	=head2 AIO FUNCTIONS	224	=head2 AIO REQUEST FUNCTIONS
99		225
100	All the C<aio_*> calls are more or less thin wrappers around the syscall	226	All the C<aio_*> calls are more or less thin wrappers around the syscall
101	with the same name (sans C<aio_>). The arguments are similar or identical,	227	with the same name (sans C<aio_>). The arguments are similar or identical,
102	and they all accept an additional (and optional) C<$callback> argument	228	and they all accept an additional (and optional) C<$callback> argument
103	which must be a code reference. This code reference will get called with	229	which must be a code reference. This code reference will get called with
104	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
105	perl, which usually delivers "false") as it's sole argument when the given	231	perl, which usually delivers "false") as its sole argument after the given
106	syscall has been executed asynchronously.	232	syscall has been executed asynchronously.
107		233
108	All functions expecting a filehandle keep a copy of the filehandle	234	All functions expecting a filehandle keep a copy of the filehandle
109	internally until the request has finished.	235	internally until the request has finished.
110		236
111	All requests return objects of type L<IO::AIO::REQ> that allow further	237	All functions return request objects of type L<IO::AIO::REQ> that allow
112	manipulation of those requests while they are in-flight.	238	further manipulation of those requests while they are in-flight.
113		239
114	The pathnames you pass to these routines I<must> be absolute and	240	The pathnames you pass to these routines I<must> be absolute and
115	encoded in byte form. The reason for the former is that at the time the	241	encoded as octets. The reason for the former is that at the time the
116	request is being executed, the current working directory could have	242	request is being executed, the current working directory could have
117	changed. Alternatively, you can make sure that you never change the	243	changed. Alternatively, you can make sure that you never change the
118	current working directory.	244	current working directory anywhere in the program and then use relative
		245	paths.
119		246
120	To encode pathnames to byte form, either make sure you either: a)	247	To encode pathnames as octets, either make sure you either: a) always pass
121	always pass in filenames you got from outside (command line, readdir	248	in filenames you got from outside (command line, readdir etc.) without
122	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	249	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
123	your pathnames to the locale (or other) encoding in effect in the user	250	your pathnames to the locale (or other) encoding in effect in the user
124	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	251	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
125	use something else.	252	use something else to ensure your scalar has the correct contents.
		253
		254	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		255	handles correctly whether it is set or not.
126		256
127	=over 4	257	=over 4
128		258
129	=item aioreq_pri $pri	259	=item $prev_pri = aioreq_pri [$pri]
130		260
131	Sets the priority for the next aio request. The default priority	261	Returns the priority value that would be used for the next request and, if
		262	C<$pri> is given, sets the priority for the next aio request.
		263
132	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,	264	The default priority is C<0>, the minimum and maximum priorities are C<-4>
133	respectively. Requests with higher priority will be serviced first.	265	and C<4>, respectively. Requests with higher priority will be serviced
		266	first.
134		267
135	The priority will be reset to C<0> after each call to one of the C<aio_>	268	The priority will be reset to C<0> after each call to one of the C<aio_*>
136	functions.	269	functions.
		270
		271	Example: open a file with low priority, then read something from it with
		272	higher priority so the read request is serviced before other low priority
		273	open requests (potentially spamming the cache):
		274
		275	aioreq_pri -3;
		276	aio_open ..., sub {
		277	return unless $_[0];
		278
		279	aioreq_pri -2;
		280	aio_read $_[0], ..., sub {
		281	...
		282	};
		283	};
		284
		285
		286	=item aioreq_nice $pri_adjust
		287
		288	Similar to C<aioreq_pri>, but subtracts the given value from the current
		289	priority, so the effect is cumulative.
		290
137		291
138	=item aio_open $pathname, $flags, $mode, $callback->($fh)	292	=item aio_open $pathname, $flags, $mode, $callback->($fh)
139		293
140	Asynchronously open or create a file and call the callback with a newly	294	Asynchronously open or create a file and call the callback with a newly
141	created filehandle for the file.	295	created filehandle for the file.
…		…
147	list. They are the same as used by C<sysopen>.	301	list. They are the same as used by C<sysopen>.
148		302
149	Likewise, C<$mode> specifies the mode of the newly created file, if it	303	Likewise, C<$mode> specifies the mode of the newly created file, if it
150	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	304	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
151	except that it is mandatory (i.e. use C<0> if you don't create new files,	305	except that it is mandatory (i.e. use C<0> if you don't create new files,
152	and C<0666> or C<0777> if you do).	306	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		307	by the umask in effect then the request is being executed, so better never
		308	change the umask.
153		309
154	Example:	310	Example:
155		311
156	aio_open "/etc/passwd", O_RDONLY, 0, sub {	312	aio_open "/etc/passwd", O_RDONLY, 0, sub {
157	if ($_[0]) {	313	if ($_[0]) {
…		…
160	} else {	316	} else {
161	die "open failed: $!\n";	317	die "open failed: $!\n";
162	}	318	}
163	};	319	};
164		320
		321
165	=item aio_close $fh, $callback->($status)	322	=item aio_close $fh, $callback->($status)
166		323
167	Asynchronously close a file and call the callback with the result	324	Asynchronously close a file and call the callback with the result
168	code. I<WARNING:> although accepted, you should not pass in a perl	325	code.
169	filehandle here, as perl will likely close the file descriptor another
170	time when the filehandle is destroyed. Normally, you can safely call perls
171	C<close> or just let filehandles go out of scope.
172		326
173	This is supposed to be a bug in the API, so that might change. It's	327	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
174	therefore best to avoid this function.	328	closing the file descriptor associated with the filehandle itself.
		329
		330	Therefore, C<aio_close> will not close the filehandle - instead it will
		331	use dup2 to overwrite the file descriptor with the write-end of a pipe
		332	(the pipe fd will be created on demand and will be cached).
		333
		334	Or in other words: the file descriptor will be closed, but it will not be
		335	free for reuse until the perl filehandle is closed.
		336
		337	=cut
175		338
176	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
177		340
178	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
179		342
180	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	343	Reads or writes C<$length> bytes from or to the specified C<$fh> and
181	into the scalar given by C<data> and offset C<dataoffset> and calls the	344	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
182	callback without the actual number of bytes read (or -1 on error, just	345	and calls the callback without the actual number of bytes read (or -1 on
183	like the syscall).	346	error, just like the syscall).
		347
		348	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		349	offset plus the actual number of bytes read.
		350
		351	If C<$offset> is undefined, then the current file descriptor offset will
		352	be used (and updated), otherwise the file descriptor offset will not be
		353	changed by these calls.
		354
		355	If C<$length> is undefined in C<aio_write>, use the remaining length of
		356	C<$data>.
		357
		358	If C<$dataoffset> is less than zero, it will be counted from the end of
		359	C<$data>.
184		360
185	The C<$data> scalar I<MUST NOT> be modified in any way while the request	361	The C<$data> scalar I<MUST NOT> be modified in any way while the request
186	is outstanding. Modifying it can result in segfaults or WW3 (if the	362	is outstanding. Modifying it can result in segfaults or World War III (if
187	necessary/optional hardware is installed).	363	the necessary/optional hardware is installed).
188		364
189	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	365	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
190	offset C<0> within the scalar:	366	offset C<0> within the scalar:
191		367
192	aio_read $fh, 7, 15, $buffer, 0, sub {	368	aio_read $fh, 7, 15, $buffer, 0, sub {
193	$_[0] > 0 or die "read error: $!";	369	$_[0] > 0 or die "read error: $!";
194	print "read $_[0] bytes: <$buffer>\n";	370	print "read $_[0] bytes: <$buffer>\n";
195	};	371	};
196		372
197	=item aio_move $srcpath, $dstpath, $callback->($status)
198
199	[EXPERIMENTAL due to internal aio_group use]
200
201	Try to move the I<file> (directories not supported as either source or
202	destination) from C<$srcpath> to C<$dstpath> and call the callback with
203	the C<0> (error) or C<-1> ok.
204
205	This is a composite request that tries to rename(2) the file first. If
206	rename files with C<EXDEV>, it creates the destination file with mode 0200
207	and copies the contents of the source file into it using C<aio_sendfile>,
208	followed by restoring atime, mtime, access mode and uid/gid, in that
209	order, and unlinking the C<$srcpath>.
210
211	If an error occurs, the partial destination file will be unlinked, if
212	possible, except when setting atime, mtime, access mode and uid/gid, where
213	errors are being ignored.
214
215	=cut
216
217	sub aio_move($$$) {
218	my ($src, $dst, $cb) = @_;
219
220	my $grp = aio_group $cb;
221
222	add $grp aio_rename $src, $dst, sub {
223	if ($_[0] && $! == EXDEV) {
224	add $grp aio_open $src, O_RDONLY, 0, sub {
225	if (my $src_fh = $_[0]) {
226	my @stat = stat $src_fh;
227
228	add $grp aio_open $dst, O_WRONLY, 0200, sub {
229	if (my $dst_fh = $_[0]) {
230	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
231	close $src_fh;
232
233	if ($_[0] == $stat[7]) {
234	utime $stat[8], $stat[9], $dst;
235	chmod $stat[2] & 07777, $dst_fh;
236	chown $stat[4], $stat[5], $dst_fh;
237	close $dst_fh;
238
239	add $grp aio_unlink $src, sub {
240	$grp->result ($_[0]);
241	};
242	} else {
243	my $errno = $!;
244	add $grp aio_unlink $dst, sub {
245	$! = $errno;
246	$grp->result (-1);
247	};
248	}
249	};
250	} else {
251	$grp->result (-1);
252	}
253	},
254
255	} else {
256	$grp->result (-1);
257	}
258	};
259	} else {
260	$grp->result ($_[0]);
261	}
262	};
263
264	$grp
265	}
266		373
267	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	374	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
268		375
269	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	376	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
270	reading at byte offset C<$in_offset>, and starts writing at the current	377	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
274		381
275	This call tries to make use of a native C<sendfile> syscall to provide	382	This call tries to make use of a native C<sendfile> syscall to provide
276	zero-copy operation. For this to work, C<$out_fh> should refer to a	383	zero-copy operation. For this to work, C<$out_fh> should refer to a
277	socket, and C<$in_fh> should refer to mmap'able file.	384	socket, and C<$in_fh> should refer to mmap'able file.
278		385
279	If the native sendfile call fails or is not implemented, it will be	386	If a native sendfile cannot be found or it fails with C<ENOSYS>,
		387	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,
280	emulated, so you can call C<aio_sendfile> on any type of filehandle	388	it will be emulated, so you can call C<aio_sendfile> on any type of
281	regardless of the limitations of the operating system.	389	filehandle regardless of the limitations of the operating system.
282		390
283	Please note, however, that C<aio_sendfile> can read more bytes from	391	Please note, however, that C<aio_sendfile> can read more bytes from
284	C<$in_fh> than are written, and there is no way to find out how many	392	C<$in_fh> than are written, and there is no way to find out how many
285	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	393	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
286	provides the number of bytes written to C<$out_fh>. Only if the result	394	provides the number of bytes written to C<$out_fh>. Only if the result
287	value equals C<$length> one can assume that C<$length> bytes have been	395	value equals C<$length> one can assume that C<$length> bytes have been
288	read.	396	read.
		397
289		398
290	=item aio_readahead $fh,$offset,$length, $callback->($retval)	399	=item aio_readahead $fh,$offset,$length, $callback->($retval)
291		400
292	C<aio_readahead> populates the page cache with data from a file so that	401	C<aio_readahead> populates the page cache with data from a file so that
293	subsequent reads from that file will not block on disk I/O. The C<$offset>	402	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
299	file. The current file offset of the file is left unchanged.	408	file. The current file offset of the file is left unchanged.
300		409
301	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	410	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
302	emulated by simply reading the data, which would have a similar effect.	411	emulated by simply reading the data, which would have a similar effect.
303		412
		413
304	=item aio_stat $fh_or_path, $callback->($status)	414	=item aio_stat $fh_or_path, $callback->($status)
305		415
306	=item aio_lstat $fh, $callback->($status)	416	=item aio_lstat $fh, $callback->($status)
307		417
308	Works like perl's C<stat> or C<lstat> in void context. The callback will	418	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
321	aio_stat "/etc/passwd", sub {	431	aio_stat "/etc/passwd", sub {
322	$_[0] and die "stat failed: $!";	432	$_[0] and die "stat failed: $!";
323	print "size is ", -s _, "\n";	433	print "size is ", -s _, "\n";
324	};	434	};
325		435
		436
		437	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		438
		439	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		440	whether a file handle or path was passed.
		441
		442	On success, the callback is passed a hash reference with the following
		443	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		444	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		445	is passed.
		446
		447	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		448	C<ST_NOSUID>.
		449
		450	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		451	their correct value when available, or to C<0> on systems that do
		452	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		453	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		454	C<ST_NODIRATIME> and C<ST_RELATIME>.
		455
		456	Example: stat C</wd> and dump out the data if successful.
		457
		458	aio_statvfs "/wd", sub {
		459	my $f = $_[0]
		460	or die "statvfs: $!";
		461
		462	use Data::Dumper;
		463	say Dumper $f;
		464	};
		465
		466	# result:
		467	{
		468	bsize => 1024,
		469	bfree => 4333064312,
		470	blocks => 10253828096,
		471	files => 2050765568,
		472	flag => 4096,
		473	favail => 2042092649,
		474	bavail => 4333064312,
		475	ffree => 2042092649,
		476	namemax => 255,
		477	frsize => 1024,
		478	fsid => 1810
		479	}
		480
		481
		482	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		483
		484	Works like perl's C<utime> function (including the special case of $atime
		485	and $mtime being undef). Fractional times are supported if the underlying
		486	syscalls support them.
		487
		488	When called with a pathname, uses utimes(2) if available, otherwise
		489	utime(2). If called on a file descriptor, uses futimes(2) if available,
		490	otherwise returns ENOSYS, so this is not portable.
		491
		492	Examples:
		493
		494	# set atime and mtime to current time (basically touch(1)):
		495	aio_utime "path", undef, undef;
		496	# set atime to current time and mtime to beginning of the epoch:
		497	aio_utime "path", time, undef; # undef==0
		498
		499
		500	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		501
		502	Works like perl's C<chown> function, except that C<undef> for either $uid
		503	or $gid is being interpreted as "do not change" (but -1 can also be used).
		504
		505	Examples:
		506
		507	# same as "chown root path" in the shell:
		508	aio_chown "path", 0, -1;
		509	# same as above:
		510	aio_chown "path", 0, undef;
		511
		512
		513	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		514
		515	Works like truncate(2) or ftruncate(2).
		516
		517
		518	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		519
		520	Works like perl's C<chmod> function.
		521
		522
326	=item aio_unlink $pathname, $callback->($status)	523	=item aio_unlink $pathname, $callback->($status)
327		524
328	Asynchronously unlink (delete) a file and call the callback with the	525	Asynchronously unlink (delete) a file and call the callback with the
329	result code.	526	result code.
330		527
		528
		529	=item aio_mknod $path, $mode, $dev, $callback->($status)
		530
		531	[EXPERIMENTAL]
		532
		533	Asynchronously create a device node (or fifo). See mknod(2).
		534
		535	The only (POSIX-) portable way of calling this function is:
		536
		537	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		538
		539
331	=item aio_link $srcpath, $dstpath, $callback->($status)	540	=item aio_link $srcpath, $dstpath, $callback->($status)
332		541
333	Asynchronously create a new link to the existing object at C<$srcpath> at	542	Asynchronously create a new link to the existing object at C<$srcpath> at
334	the path C<$dstpath> and call the callback with the result code.	543	the path C<$dstpath> and call the callback with the result code.
335		544
		545
336	=item aio_symlink $srcpath, $dstpath, $callback->($status)	546	=item aio_symlink $srcpath, $dstpath, $callback->($status)
337		547
338	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	548	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
339	the path C<$dstpath> and call the callback with the result code.	549	the path C<$dstpath> and call the callback with the result code.
340		550
		551
		552	=item aio_readlink $path, $callback->($link)
		553
		554	Asynchronously read the symlink specified by C<$path> and pass it to
		555	the callback. If an error occurs, nothing or undef gets passed to the
		556	callback.
		557
		558
341	=item aio_rename $srcpath, $dstpath, $callback->($status)	559	=item aio_rename $srcpath, $dstpath, $callback->($status)
342		560
343	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	561	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
344	rename(2) and call the callback with the result code.	562	rename(2) and call the callback with the result code.
345		563
		564
		565	=item aio_mkdir $pathname, $mode, $callback->($status)
		566
		567	Asynchronously mkdir (create) a directory and call the callback with
		568	the result code. C<$mode> will be modified by the umask at the time the
		569	request is executed, so do not change your umask.
		570
		571
346	=item aio_rmdir $pathname, $callback->($status)	572	=item aio_rmdir $pathname, $callback->($status)
347		573
348	Asynchronously rmdir (delete) a directory and call the callback with the	574	Asynchronously rmdir (delete) a directory and call the callback with the
349	result code.	575	result code.
		576
350		577
351	=item aio_readdir $pathname, $callback->($entries)	578	=item aio_readdir $pathname, $callback->($entries)
352		579
353	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	580	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
354	directory (i.e. opendir + readdir + closedir). The entries will not be	581	directory (i.e. opendir + readdir + closedir). The entries will not be
355	sorted, and will B<NOT> include the C<.> and C<..> entries.	582	sorted, and will B<NOT> include the C<.> and C<..> entries.
356		583
357	The callback a single argument which is either C<undef> or an array-ref	584	The callback is passed a single argument which is either C<undef> or an
358	with the filenames.	585	array-ref with the filenames.
		586
		587
		588	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		589
		590	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune
		591	behaviour and output format. In case of an error, C<$entries> will be
		592	C<undef>.
		593
		594	The flags are a combination of the following constants, ORed together (the
		595	flags will also be passed to the callback, possibly modified):
		596
		597	=over 4
		598
		599	=item IO::AIO::READDIR_DENTS
		600
		601	When this flag is off, then the callback gets an arrayref with of names
		602	only (as with C<aio_readdir>), otherwise it gets an arrayref with
		603	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		604	entry in more detail.
		605
		606	C<$name> is the name of the entry.
		607
		608	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		609
		610	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		611	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		612	C<IO::AIO::DT_WHT>.
		613
		614	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		615	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		616	scalars are read-only: you can not modify them.
		617
		618	C<$inode> is the inode number (which might not be exact on systems with 64
		619	bit inode numbers and 32 bit perls). This field has unspecified content on
		620	systems that do not deliver the inode information.
		621
		622	=item IO::AIO::READDIR_DIRS_FIRST
		623
		624	When this flag is set, then the names will be returned in an order where
		625	likely directories come first. This is useful when you need to quickly
		626	find directories, or you want to find all directories while avoiding to
		627	stat() each entry.
		628
		629	If the system returns type information in readdir, then this is used
		630	to find directories directly. Otherwise, likely directories are files
		631	beginning with ".", or otherwise files with no dots, of which files with
		632	short names are tried first.
		633
		634	=item IO::AIO::READDIR_STAT_ORDER
		635
		636	When this flag is set, then the names will be returned in an order
		637	suitable for stat()'ing each one. That is, when you plan to stat()
		638	all files in the given directory, then the returned order will likely
		639	be fastest.
		640
		641	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		642	the likely dirs come first, resulting in a less optimal stat order.
		643
		644	=item IO::AIO::READDIR_FOUND_UNKNOWN
		645
		646	This flag should not be set when calling C<aio_readdirx>. Instead, it
		647	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		648	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all
		649	C<$type>'s are known, which can be used to speed up some algorithms.
		650
		651	=back
		652
		653
		654	=item aio_load $path, $data, $callback->($status)
		655
		656	This is a composite request that tries to fully load the given file into
		657	memory. Status is the same as with aio_read.
		658
		659	=cut
		660
		661	sub aio_load($$;$) {
		662	my ($path, undef, $cb) = @_;
		663	my $data = \$_[1];
		664
		665	my $pri = aioreq_pri;
		666	my $grp = aio_group $cb;
		667
		668	aioreq_pri $pri;
		669	add $grp aio_open $path, O_RDONLY, 0, sub {
		670	my $fh = shift
		671	or return $grp->result (-1);
		672
		673	aioreq_pri $pri;
		674	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		675	$grp->result ($_[0]);
		676	};
		677	};
		678
		679	$grp
		680	}
		681
		682	=item aio_copy $srcpath, $dstpath, $callback->($status)
		683
		684	Try to copy the I<file> (directories not supported as either source or
		685	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		686	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		687
		688	This is a composite request that creates the destination file with
		689	mode 0200 and copies the contents of the source file into it using
		690	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		691	uid/gid, in that order.
		692
		693	If an error occurs, the partial destination file will be unlinked, if
		694	possible, except when setting atime, mtime, access mode and uid/gid, where
		695	errors are being ignored.
		696
		697	=cut
		698
		699	sub aio_copy($$;$) {
		700	my ($src, $dst, $cb) = @_;
		701
		702	my $pri = aioreq_pri;
		703	my $grp = aio_group $cb;
		704
		705	aioreq_pri $pri;
		706	add $grp aio_open $src, O_RDONLY, 0, sub {
		707	if (my $src_fh = $_[0]) {
		708	my @stat = stat $src_fh; # hmm, might block over nfs?
		709
		710	aioreq_pri $pri;
		711	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		712	if (my $dst_fh = $_[0]) {
		713	aioreq_pri $pri;
		714	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		715	if ($_[0] == $stat[7]) {
		716	$grp->result (0);
		717	close $src_fh;
		718
		719	my $ch = sub {
		720	aioreq_pri $pri;
		721	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		722	aioreq_pri $pri;
		723	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		724	aioreq_pri $pri;
		725	add $grp aio_close $dst_fh;
		726	}
		727	};
		728	};
		729
		730	aioreq_pri $pri;
		731	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		732	if ($_[0] < 0 && $! == ENOSYS) {
		733	aioreq_pri $pri;
		734	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		735	} else {
		736	$ch->();
		737	}
		738	};
		739	} else {
		740	$grp->result (-1);
		741	close $src_fh;
		742	close $dst_fh;
		743
		744	aioreq $pri;
		745	add $grp aio_unlink $dst;
		746	}
		747	};
		748	} else {
		749	$grp->result (-1);
		750	}
		751	},
		752
		753	} else {
		754	$grp->result (-1);
		755	}
		756	};
		757
		758	$grp
		759	}
		760
		761	=item aio_move $srcpath, $dstpath, $callback->($status)
		762
		763	Try to move the I<file> (directories not supported as either source or
		764	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		765	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		766
		767	This is a composite request that tries to rename(2) the file first; if
		768	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		769	that is successful, unlinks the C<$srcpath>.
		770
		771	=cut
		772
		773	sub aio_move($$;$) {
		774	my ($src, $dst, $cb) = @_;
		775
		776	my $pri = aioreq_pri;
		777	my $grp = aio_group $cb;
		778
		779	aioreq_pri $pri;
		780	add $grp aio_rename $src, $dst, sub {
		781	if ($_[0] && $! == EXDEV) {
		782	aioreq_pri $pri;
		783	add $grp aio_copy $src, $dst, sub {
		784	$grp->result ($_[0]);
		785
		786	if (!$_[0]) {
		787	aioreq_pri $pri;
		788	add $grp aio_unlink $src;
		789	}
		790	};
		791	} else {
		792	$grp->result ($_[0]);
		793	}
		794	};
		795
		796	$grp
		797	}
359		798
360	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	799	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
361		800
362	[EXPERIMENTAL due to internal aio_group use]
363
364	Scans a directory (similar to C<aio_readdir>) but additionally tries to	801	Scans a directory (similar to C<aio_readdir>) but additionally tries to
365	separate the entries of directory C<$path> into two sets of names, ones	802	efficiently separate the entries of directory C<$path> into two sets of
366	you can recurse into (directories or links to them), and ones you cannot	803	names, directories you can recurse into (directories), and ones you cannot
367	recurse into (everything else).	804	recurse into (everything else, including symlinks to directories).
368		805
369	C<aio_scandir> is a composite request that creates of many sub requests_	806	C<aio_scandir> is a composite request that creates of many sub requests_
370	C<$maxreq> specifies the maximum number of outstanding aio requests that	807	C<$maxreq> specifies the maximum number of outstanding aio requests that
371	this function generates. If it is C<< <= 0 >>, then a suitable default	808	this function generates. If it is C<< <= 0 >>, then a suitable default
372	will be chosen (currently 6).	809	will be chosen (currently 4).
373		810
374	On error, the callback is called without arguments, otherwise it receives	811	On error, the callback is called without arguments, otherwise it receives
375	two array-refs with path-relative entry names.	812	two array-refs with path-relative entry names.
376		813
377	Example:	814	Example:
…		…
384		821
385	Implementation notes.	822	Implementation notes.
386		823
387	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	824	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
388		825
		826	If readdir returns file type information, then this is used directly to
		827	find directories.
		828
389	After reading the directory, the modification time, size etc. of the	829	Otherwise, after reading the directory, the modification time, size etc.
390	directory before and after the readdir is checked, and if they match (and	830	of the directory before and after the readdir is checked, and if they
391	isn't the current time), the link count will be used to decide how many	831	match (and isn't the current time), the link count will be used to decide
392	entries are directories (if >= 2). Otherwise, no knowledge of the number	832	how many entries are directories (if >= 2). Otherwise, no knowledge of the
393	of subdirectories will be assumed.	833	number of subdirectories will be assumed.
394		834
395	Then entries will be sorted into likely directories (everything without	835	Then entries will be sorted into likely directories a non-initial dot
396	a non-initial dot currently) and likely non-directories (everything	836	currently) and likely non-directories (see C<aio_readdirx>). Then every
397	else). Then every entry plus an appended C</.> will be C<stat>'ed,	837	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
398	likely directories first. If that succeeds, it assumes that the entry	838	in order of their inode numbers. If that succeeds, it assumes that the
399	is a directory or a symlink to directory (which will be checked	839	entry is a directory or a symlink to directory (which will be checked
400	seperately). This is often faster than stat'ing the entry itself because	840	seperately). This is often faster than stat'ing the entry itself because
401	filesystems might detect the type of the entry without reading the inode	841	filesystems might detect the type of the entry without reading the inode
402	data (e.g. ext2fs filetype feature).	842	data (e.g. ext2fs filetype feature), even on systems that cannot return
		843	the filetype information on readdir.
403		844
404	If the known number of directories (link count - 2) has been reached, the	845	If the known number of directories (link count - 2) has been reached, the
405	rest of the entries is assumed to be non-directories.	846	rest of the entries is assumed to be non-directories.
406		847
407	This only works with certainty on POSIX (= UNIX) filesystems, which	848	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
411	as those tend to return 0 or 1 as link counts, which disables the	852	as those tend to return 0 or 1 as link counts, which disables the
412	directory counting heuristic.	853	directory counting heuristic.
413		854
414	=cut	855	=cut
415		856
416	sub aio_scandir($$$) {	857	sub aio_scandir($$;$) {
417	my ($path, $maxreq, $cb) = @_;	858	my ($path, $maxreq, $cb) = @_;
418		859
		860	my $pri = aioreq_pri;
		861
419	my $grp = aio_group $cb;	862	my $grp = aio_group $cb;
420		863
421	$maxreq = 6 if $maxreq <= 0;	864	$maxreq = 4 if $maxreq <= 0;
422		865
423	# stat once	866	# stat once
		867	aioreq_pri $pri;
424	add $grp aio_stat $path, sub {	868	add $grp aio_stat $path, sub {
425	return $grp->result () if $_[0];	869	return $grp->result () if $_[0];
426	my $now = time;	870	my $now = time;
427	my $hash1 = join ":", (stat _)[0,1,3,7,9];	871	my $hash1 = join ":", (stat _)[0,1,3,7,9];
428		872
429	# read the directory entries	873	# read the directory entries
		874	aioreq_pri $pri;
430	add $grp aio_readdir $path, sub {	875	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {
431	my $entries = shift	876	my $entries = shift
432	or return $grp->result ();	877	or return $grp->result ();
433		878
434	# stat the dir another time	879	# stat the dir another time
		880	aioreq_pri $pri;
435	add $grp aio_stat $path, sub {	881	add $grp aio_stat $path, sub {
436	my $hash2 = join ":", (stat _)[0,1,3,7,9];	882	my $hash2 = join ":", (stat _)[0,1,3,7,9];
437		883
438	my $ndirs;	884	my $ndirs;
439		885
440	# take the slow route if anything looks fishy	886	# take the slow route if anything looks fishy
441	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	887	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
442	$ndirs = -1;	888	$ndirs = -1;
443	} else {	889	} else {
444	# if nlink == 2, we are finished	890	# if nlink == 2, we are finished
445	# on non-posix-fs's, we rely on nlink < 2	891	# for non-posix-fs's, we rely on nlink < 2
446	$ndirs = (stat _)[3] - 2	892	$ndirs = (stat _)[3] - 2
447	or return $grp->result ([], $entries);	893	or return $grp->result ([], $entries);
448	}	894	}
449		895
450	# sort into likely dirs and likely nondirs
451	# dirs == files without ".", short entries first
452	$entries = [map $_->[0],
453	sort { $b->[1] cmp $a->[1] }
454	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
455	@$entries];
456
457	my (@dirs, @nondirs);	896	my (@dirs, @nondirs);
458		897
459	my ($statcb, $schedcb);
460	my $nreq = 0;
461
462	my $statgrp = add $grp aio_group;	898	my $statgrp = add $grp aio_group sub {
		899	$grp->result (\@dirs, \@nondirs);
		900	};
463		901
464	$schedcb = sub {	902	limit $statgrp $maxreq;
465	if (@$entries) {	903	feed $statgrp sub {
466	if ($nreq < $maxreq) {	904	return unless @$entries;
467	my $ent = pop @$entries;	905	my $entry = shift @$entries;
		906
		907	aioreq_pri $pri;
		908	add $statgrp aio_stat "$path/$entry/.", sub {
		909	if ($_[0] < 0) {
		910	push @nondirs, $entry;
		911	} else {
		912	# need to check for real directory
		913	aioreq_pri $pri;
		914	add $statgrp aio_lstat "$path/$entry", sub {
		915	if (-d _) {
		916	push @dirs, $entry;
		917
		918	unless (--$ndirs) {
		919	push @nondirs, @$entries;
		920	feed $statgrp;
		921	}
		922	} else {
		923	push @nondirs, $entry;
		924	}
468	$nreq++;	925	}
469	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
470	}	926	}
471	} elsif (!$nreq) {
472	# finished
473	$statgrp->cancel;
474	undef $statcb;
475	undef $schedcb;
476	$grp->result (\@dirs, \@nondirs);
477	}	927	};
478	};	928	};
479	$statcb = sub {
480	my ($status, $entry) = @_;
481
482	if ($status < 0) {
483	$nreq--;
484	push @nondirs, $entry;
485	&$schedcb;
486	} else {
487	# need to check for real directory
488	add $grp aio_lstat "$path/$entry", sub {
489	$nreq--;
490
491	if (-d _) {
492	push @dirs, $entry;
493
494	if (!--$ndirs) {
495	push @nondirs, @$entries;
496	$entries = [];
497	}
498	} else {
499	push @nondirs, $entry;
500	}
501
502	&$schedcb;
503	}
504	}
505	};
506
507	&$schedcb while @$entries && $nreq < $maxreq;
508	};	929	};
509	};	930	};
510	};	931	};
511		932
512	$grp	933	$grp
513	}	934	}
514		935
		936	=item aio_rmtree $path, $callback->($status)
		937
		938	Delete a directory tree starting (and including) C<$path>, return the
		939	status of the final C<rmdir> only. This is a composite request that
		940	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		941	everything else.
		942
		943	=cut
		944
		945	sub aio_rmtree;
		946	sub aio_rmtree($;$) {
		947	my ($path, $cb) = @_;
		948
		949	my $pri = aioreq_pri;
		950	my $grp = aio_group $cb;
		951
		952	aioreq_pri $pri;
		953	add $grp aio_scandir $path, 0, sub {
		954	my ($dirs, $nondirs) = @_;
		955
		956	my $dirgrp = aio_group sub {
		957	add $grp aio_rmdir $path, sub {
		958	$grp->result ($_[0]);
		959	};
		960	};
		961
		962	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		963	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		964
		965	add $grp $dirgrp;
		966	};
		967
		968	$grp
		969	}
		970
		971	=item aio_sync $callback->($status)
		972
		973	Asynchronously call sync and call the callback when finished.
		974
515	=item aio_fsync $fh, $callback->($status)	975	=item aio_fsync $fh, $callback->($status)
516		976
517	Asynchronously call fsync on the given filehandle and call the callback	977	Asynchronously call fsync on the given filehandle and call the callback
518	with the fsync result code.	978	with the fsync result code.
519		979
…		…
523	callback with the fdatasync result code.	983	callback with the fdatasync result code.
524		984
525	If this call isn't available because your OS lacks it or it couldn't be	985	If this call isn't available because your OS lacks it or it couldn't be
526	detected, it will be emulated by calling C<fsync> instead.	986	detected, it will be emulated by calling C<fsync> instead.
527		987
		988	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		989
		990	Sync the data portion of the file specified by C<$offset> and C<$length>
		991	to disk (but NOT the metadata), by calling the Linux-specific
		992	sync_file_range call. If sync_file_range is not available or it returns
		993	ENOSYS, then fdatasync or fsync is being substituted.
		994
		995	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		996	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		997	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		998	manpage for details.
		999
		1000	=item aio_pathsync $path, $callback->($status)
		1001
		1002	This request tries to open, fsync and close the given path. This is a
		1003	composite request intended to sync directories after directory operations
		1004	(E.g. rename). This might not work on all operating systems or have any
		1005	specific effect, but usually it makes sure that directory changes get
		1006	written to disc. It works for anything that can be opened for read-only,
		1007	not just directories.
		1008
		1009	Future versions of this function might fall back to other methods when
		1010	C<fsync> on the directory fails (such as calling C<sync>).
		1011
		1012	Passes C<0> when everything went ok, and C<-1> on error.
		1013
		1014	=cut
		1015
		1016	sub aio_pathsync($;$) {
		1017	my ($path, $cb) = @_;
		1018
		1019	my $pri = aioreq_pri;
		1020	my $grp = aio_group $cb;
		1021
		1022	aioreq_pri $pri;
		1023	add $grp aio_open $path, O_RDONLY, 0, sub {
		1024	my ($fh) = @_;
		1025	if ($fh) {
		1026	aioreq_pri $pri;
		1027	add $grp aio_fsync $fh, sub {
		1028	$grp->result ($_[0]);
		1029
		1030	aioreq_pri $pri;
		1031	add $grp aio_close $fh;
		1032	};
		1033	} else {
		1034	$grp->result (-1);
		1035	}
		1036	};
		1037
		1038	$grp
		1039	}
		1040
		1041	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1042
		1043	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1044	scalars (see the L<Sys::Mmap> or L<Mmap> modules for details on this, note
		1045	that the scalar must only be modified in-place while an aio operation is
		1046	pending on it).
		1047
		1048	It calls the C<msync> function of your OS, if available, with the memory
		1049	area starting at C<$offset> in the string and ending C<$length> bytes
		1050	later. If C<$length> is negative, counts from the end, and if C<$length>
		1051	is C<undef>, then it goes till the end of the string. The flags can be
		1052	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1053	C<IO::AIO::MS_SYNC>.
		1054
		1055	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1056
		1057	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1058	scalars.
		1059
		1060	It touches (reads or writes) all memory pages in the specified
		1061	range inside the scalar. All caveats and parameters are the same
		1062	as for C<aio_msync>, above, except for flags, which must be either
		1063	C<0> (which reads all pages and ensures they are instantiated) or
		1064	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1065	writing an octet from it, which dirties the page).
		1066
528	=item aio_group $callback->(...)	1067	=item aio_group $callback->(...)
529
530	[EXPERIMENTAL]
531		1068
532	This is a very special aio request: Instead of doing something, it is a	1069	This is a very special aio request: Instead of doing something, it is a
533	container for other aio requests, which is useful if you want to bundle	1070	container for other aio requests, which is useful if you want to bundle
534	many requests into a single, composite, request.	1071	many requests into a single, composite, request with a definite callback
		1072	and the ability to cancel the whole request with its subrequests.
535		1073
536	Returns an object of class L<IO::AIO::GRP>. See its documentation below	1074	Returns an object of class L<IO::AIO::GRP>. See its documentation below
537	for more info.	1075	for more info.
538		1076
539	Example:	1077	Example:
…		…
558	phase and still requires a worker thread. Thus, the callback will not	1096	phase and still requires a worker thread. Thus, the callback will not
559	be executed immediately but only after other requests in the queue have	1097	be executed immediately but only after other requests in the queue have
560	entered their execution phase. This can be used to measure request	1098	entered their execution phase. This can be used to measure request
561	latency.	1099	latency.
562		1100
563	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	1101	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
564		1102
565	Mainly used for debugging and benchmarking, this aio request puts one of	1103	Mainly used for debugging and benchmarking, this aio request puts one of
566	the request workers to sleep for the given time.	1104	the request workers to sleep for the given time.
567		1105
568	While it is theoretically handy to have simple I/O scheduling requests	1106	While it is theoretically handy to have simple I/O scheduling requests
569	like sleep and file handle readable/writable, the overhead this creates	1107	like sleep and file handle readable/writable, the overhead this creates is
570	is immense, so do not use this function except to put your application	1108	immense (it blocks a thread for a long time) so do not use this function
571	under artificial I/O pressure.	1109	except to put your application under artificial I/O pressure.
572		1110
573	=back	1111	=back
574		1112
575	=head2 IO::AIO::REQ CLASS	1113	=head2 IO::AIO::REQ CLASS
576		1114
577	All non-aggregate C<aio_*> functions return an object of this class when	1115	All non-aggregate C<aio_*> functions return an object of this class when
578	called in non-void context.	1116	called in non-void context.
579
580	A request always moves through the following five states in its lifetime,
581	in order: B<ready> (request has been created, but has not been executed
582	yet), B<execute> (request is currently being executed), B<pending>
583	(request has been executed but callback has not been called yet),
584	B<result> (results are being processed synchronously, includes calling the
585	callback) and B<done> (request has reached the end of its lifetime and
586	holds no resources anymore).
587		1117
588	=over 4	1118	=over 4
589		1119
590	=item cancel $req	1120	=item cancel $req
591		1121
592	Cancels the request, if possible. Has the effect of skipping execution	1122	Cancels the request, if possible. Has the effect of skipping execution
593	when entering the B<execute> state and skipping calling the callback when	1123	when entering the B<execute> state and skipping calling the callback when
594	entering the the B<result> state, but will leave the request otherwise	1124	entering the the B<result> state, but will leave the request otherwise
595	untouched. That means that requests that currently execute will not be	1125	untouched (with the exception of readdir). That means that requests that
596	stopped and resources held by the request will not be freed prematurely.	1126	currently execute will not be stopped and resources held by the request
		1127	will not be freed prematurely.
597		1128
598	=item cb $req $callback->(...)	1129	=item cb $req $callback->(...)
599		1130
600	Replace (or simply set) the callback registered to the request.	1131	Replace (or simply set) the callback registered to the request.
601		1132
…		…
645	=item * They can also can also be added to other IO::AIO::GRP objects.	1176	=item * They can also can also be added to other IO::AIO::GRP objects.
646		1177
647	=item * You must not add requests to a group from within the group callback (or	1178	=item * You must not add requests to a group from within the group callback (or
648	any later time).	1179	any later time).
649		1180
650	=item * This does not harmonise well with C<max_outstanding>, so best do
651	not combine C<aio_group> with it. Groups and feeders are recommended for
652	this kind of concurrency-limiting.
653
654	=back	1181	=back
655		1182
656	Their lifetime, simplified, looks like this: when they are empty, they	1183	Their lifetime, simplified, looks like this: when they are empty, they
657	will finish very quickly. If they contain only requests that are in the	1184	will finish very quickly. If they contain only requests that are in the
658	C<done> state, they will also finish. Otherwise they will continue to	1185	C<done> state, they will also finish. Otherwise they will continue to
659	exist.	1186	exist.
660		1187
661	That means after creating a group you have some time to add requests. And	1188	That means after creating a group you have some time to add requests
662	in the callbacks of those requests, you can add further requests to the	1189	(precisely before the callback has been invoked, which is only done within
663	group. And only when all those requests have finished will the the group	1190	the C<poll_cb>). And in the callbacks of those requests, you can add
664	itself finish.	1191	further requests to the group. And only when all those requests have
		1192	finished will the the group itself finish.
665		1193
666	=over 4	1194	=over 4
667		1195
668	=item add $grp ...	1196	=item add $grp ...
669		1197
…		…
673	be added, including other groups, as long as you do not create circular	1201	be added, including other groups, as long as you do not create circular
674	dependencies.	1202	dependencies.
675		1203
676	Returns all its arguments.	1204	Returns all its arguments.
677		1205
		1206	=item $grp->cancel_subs
		1207
		1208	Cancel all subrequests and clears any feeder, but not the group request
		1209	itself. Useful when you queued a lot of events but got a result early.
		1210
		1211	The group request will finish normally (you cannot add requests to the
		1212	group).
		1213
678	=item $grp->result (...)	1214	=item $grp->result (...)
679		1215
680	Set the result value(s) that will be passed to the group callback when all	1216	Set the result value(s) that will be passed to the group callback when all
681	subrequests have finished. By default, no argument will be passed.	1217	subrequests have finished and set the groups errno to the current value
		1218	of errno (just like calling C<errno> without an error number). By default,
		1219	no argument will be passed and errno is zero.
		1220
		1221	=item $grp->errno ([$errno])
		1222
		1223	Sets the group errno value to C<$errno>, or the current value of errno
		1224	when the argument is missing.
		1225
		1226	Every aio request has an associated errno value that is restored when
		1227	the callback is invoked. This method lets you change this value from its
		1228	default (0).
		1229
		1230	Calling C<result> will also set errno, so make sure you either set C<$!>
		1231	before the call to C<result>, or call c<errno> after it.
682		1232
683	=item feed $grp $callback->($grp)	1233	=item feed $grp $callback->($grp)
684
685	[VERY EXPERIMENTAL]
686		1234
687	Sets a feeder/generator on this group: every group can have an attached	1235	Sets a feeder/generator on this group: every group can have an attached
688	generator that generates requests if idle. The idea behind this is that,	1236	generator that generates requests if idle. The idea behind this is that,
689	although you could just queue as many requests as you want in a group,	1237	although you could just queue as many requests as you want in a group,
690	this might starve other requests for a potentially long time. For	1238	this might starve other requests for a potentially long time. For example,
691	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1239	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,
692	requests, delaying any later requests for a long time.	1240	delaying any later requests for a long time.
693		1241
694	To avoid this, and allow incremental generation of requests, you can	1242	To avoid this, and allow incremental generation of requests, you can
695	instead a group and set a feeder on it that generates those requests. The	1243	instead a group and set a feeder on it that generates those requests. The
696	feed callback will be called whenever there are few enough (see C<limit>,	1244	feed callback will be called whenever there are few enough (see C<limit>,
697	below) requests active in the group itself and is expected to queue more	1245	below) requests active in the group itself and is expected to queue more
…		…
701	not impose any limits).	1249	not impose any limits).
702		1250
703	If the feed does not queue more requests when called, it will be	1251	If the feed does not queue more requests when called, it will be
704	automatically removed from the group.	1252	automatically removed from the group.
705		1253
706	If the feed limit is C<0>, it will be set to C<2> automatically.	1254	If the feed limit is C<0> when this method is called, it will be set to
		1255	C<2> automatically.
707		1256
708	Example:	1257	Example:
709		1258
710	# stat all files in @files, but only ever use four aio requests concurrently:	1259	# stat all files in @files, but only ever use four aio requests concurrently:
711		1260
…		…
723	Sets the feeder limit for the group: The feeder will be called whenever	1272	Sets the feeder limit for the group: The feeder will be called whenever
724	the group contains less than this many requests.	1273	the group contains less than this many requests.
725		1274
726	Setting the limit to C<0> will pause the feeding process.	1275	Setting the limit to C<0> will pause the feeding process.
727		1276
		1277	The default value for the limit is C<0>, but note that setting a feeder
		1278	automatically bumps it up to C<2>.
		1279
728	=back	1280	=back
729		1281
730	=head2 SUPPORT FUNCTIONS	1282	=head2 SUPPORT FUNCTIONS
731		1283
		1284	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1285
732	=over 4	1286	=over 4
733		1287
734	=item $fileno = IO::AIO::poll_fileno	1288	=item $fileno = IO::AIO::poll_fileno
735		1289
736	Return the I<request result pipe file descriptor>. This filehandle must be	1290	Return the I<request result pipe file descriptor>. This filehandle must be
737	polled for reading by some mechanism outside this module (e.g. Event or	1291	polled for reading by some mechanism outside this module (e.g. EV, Glib,
738	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1292	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
739	to call C<poll_cb> to check the results.	1293	you have to call C<poll_cb> to check the results.
740		1294
741	See C<poll_cb> for an example.	1295	See C<poll_cb> for an example.
742		1296
743	=item IO::AIO::poll_cb	1297	=item IO::AIO::poll_cb
744		1298
745	Process all outstanding events on the result pipe. You have to call this	1299	Process some outstanding events on the result pipe. You have to call this
746	regularly. Returns the number of events processed. Returns immediately	1300	regularly. Returns C<0> if all events could be processed, or C<-1> if it
747	when no events are outstanding.	1301	returned earlier for whatever reason. Returns immediately when no events
		1302	are outstanding. The amount of events processed depends on the settings of
		1303	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1304
		1305	If not all requests were processed for whatever reason, the filehandle
		1306	will still be ready when C<poll_cb> returns, so normally you don't have to
		1307	do anything special to have it called later.
748		1308
749	Example: Install an Event watcher that automatically calls	1309	Example: Install an Event watcher that automatically calls
750	IO::AIO::poll_cb with high priority:	1310	IO::AIO::poll_cb with high priority (more examples can be found in the
		1311	SYNOPSIS section, at the top of this document):
751		1312
752	Event->io (fd => IO::AIO::poll_fileno,	1313	Event->io (fd => IO::AIO::poll_fileno,
753	poll => 'r', async => 1,	1314	poll => 'r', async => 1,
754	cb => \&IO::AIO::poll_cb);	1315	cb => \&IO::AIO::poll_cb);
755		1316
		1317	=item IO::AIO::max_poll_reqs $nreqs
		1318
		1319	=item IO::AIO::max_poll_time $seconds
		1320
		1321	These set the maximum number of requests (default C<0>, meaning infinity)
		1322	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1323	the maximum amount of time (default C<0>, meaning infinity) spent in
		1324	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1325	of time C<poll_cb> is allowed to use).
		1326
		1327	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1328	syscall per request processed, which is not normally a problem unless your
		1329	callbacks are really really fast or your OS is really really slow (I am
		1330	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1331
		1332	Setting these is useful if you want to ensure some level of
		1333	interactiveness when perl is not fast enough to process all requests in
		1334	time.
		1335
		1336	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1337
		1338	Example: Install an Event watcher that automatically calls
		1339	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1340	program get the CPU sometimes even under high AIO load.
		1341
		1342	# try not to spend much more than 0.1s in poll_cb
		1343	IO::AIO::max_poll_time 0.1;
		1344
		1345	# use a low priority so other tasks have priority
		1346	Event->io (fd => IO::AIO::poll_fileno,
		1347	poll => 'r', nice => 1,
		1348	cb => &IO::AIO::poll_cb);
		1349
756	=item IO::AIO::poll_wait	1350	=item IO::AIO::poll_wait
757		1351
		1352	If there are any outstanding requests and none of them in the result
758	Wait till the result filehandle becomes ready for reading (simply does a	1353	phase, wait till the result filehandle becomes ready for reading (simply
759	C<select> on the filehandle. This is useful if you want to synchronously wait	1354	does a C<select> on the filehandle. This is useful if you want to
760	for some requests to finish).	1355	synchronously wait for some requests to finish).
761		1356
762	See C<nreqs> for an example.	1357	See C<nreqs> for an example.
763		1358
		1359	=item IO::AIO::poll
		1360
		1361	Waits until some requests have been handled.
		1362
		1363	Returns the number of requests processed, but is otherwise strictly
		1364	equivalent to:
		1365
		1366	IO::AIO::poll_wait, IO::AIO::poll_cb
		1367
764	=item IO::AIO::nreqs	1368	=item IO::AIO::flush
765		1369
766	Returns the number of requests currently outstanding (i.e. for which their	1370	Wait till all outstanding AIO requests have been handled.
767	callback has not been invoked yet).
768		1371
769	Example: wait till there are no outstanding requests anymore:	1372	Strictly equivalent to:
770		1373
771	IO::AIO::poll_wait, IO::AIO::poll_cb	1374	IO::AIO::poll_wait, IO::AIO::poll_cb
772	while IO::AIO::nreqs;	1375	while IO::AIO::nreqs;
773		1376
774	=item IO::AIO::flush	1377	=back
775		1378
776	Wait till all outstanding AIO requests have been handled.	1379	=head3 CONTROLLING THE NUMBER OF THREADS
777		1380
778	Strictly equivalent to:	1381	=over
779
780	IO::AIO::poll_wait, IO::AIO::poll_cb
781	while IO::AIO::nreqs;
782
783	=item IO::AIO::poll
784
785	Waits until some requests have been handled.
786
787	Strictly equivalent to:
788
789	IO::AIO::poll_wait, IO::AIO::poll_cb
790	if IO::AIO::nreqs;
791		1382
792	=item IO::AIO::min_parallel $nthreads	1383	=item IO::AIO::min_parallel $nthreads
793		1384
794	Set the minimum number of AIO threads to C<$nthreads>. The current	1385	Set the minimum number of AIO threads to C<$nthreads>. The current
795	default is C<8>, which means eight asynchronous operations can execute	1386	default is C<8>, which means eight asynchronous operations can execute
796	concurrently at any one time (the number of outstanding requests,	1387	concurrently at any one time (the number of outstanding requests,
797	however, is unlimited).	1388	however, is unlimited).
798		1389
799	IO::AIO starts threads only on demand, when an AIO request is queued and	1390	IO::AIO starts threads only on demand, when an AIO request is queued and
800	no free thread exists.	1391	no free thread exists. Please note that queueing up a hundred requests can
		1392	create demand for a hundred threads, even if it turns out that everything
		1393	is in the cache and could have been processed faster by a single thread.
801		1394
802	It is recommended to keep the number of threads relatively low, as some	1395	It is recommended to keep the number of threads relatively low, as some
803	Linux kernel versions will scale negatively with the number of threads	1396	Linux kernel versions will scale negatively with the number of threads
804	(higher parallelity => MUCH higher latency). With current Linux 2.6	1397	(higher parallelity => MUCH higher latency). With current Linux 2.6
805	versions, 4-32 threads should be fine.	1398	versions, 4-32 threads should be fine.
…		…
819	This module automatically runs C<max_parallel 0> at program end, to ensure	1412	This module automatically runs C<max_parallel 0> at program end, to ensure
820	that all threads are killed and that there are no outstanding requests.	1413	that all threads are killed and that there are no outstanding requests.
821		1414
822	Under normal circumstances you don't need to call this function.	1415	Under normal circumstances you don't need to call this function.
823		1416
		1417	=item IO::AIO::max_idle $nthreads
		1418
		1419	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1420	threads that did not get a request to process within 10 seconds). That
		1421	means if a thread becomes idle while C<$nthreads> other threads are also
		1422	idle, it will free its resources and exit.
		1423
		1424	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1425	to allow for extremely high load situations, but want to free resources
		1426	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1427
		1428	The default is probably ok in most situations, especially if thread
		1429	creation is fast. If thread creation is very slow on your system you might
		1430	want to use larger values.
		1431
824	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1432	=item IO::AIO::max_outstanding $maxreqs
825		1433
826	[DEPRECATED]	1434	This is a very bad function to use in interactive programs because it
		1435	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1436	use an C<aio_group> together with a feed callback.
827		1437
828	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1438	Sets the maximum number of outstanding requests to C<$nreqs>. If you
829	try to queue up more than this number of requests, the caller will block until	1439	do queue up more than this number of requests, the next call to the
830	some requests have been handled.	1440	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1441	function will block until the limit is no longer exceeded.
831		1442
832	The default is very large, so normally there is no practical limit. If you	1443	The default value is very large, so there is no practical limit on the
833	queue up many requests in a loop it often improves speed if you set	1444	number of outstanding requests.
834	this to a relatively low number, such as C<100>.
835		1445
836	This function does not work well together with C<aio_group>'s, and their	1446	You can still queue as many requests as you want. Therefore,
837	feeder interface is better suited to limiting concurrency, so do not use	1447	C<max_outstanding> is mainly useful in simple scripts (with low values) or
838	this function.	1448	as a stop gap to shield against fatal memory overflow (with large values).
839
840	Under normal circumstances you don't need to call this function.
841		1449
842	=back	1450	=back
843		1451
		1452	=head3 STATISTICAL INFORMATION
		1453
		1454	=over
		1455
		1456	=item IO::AIO::nreqs
		1457
		1458	Returns the number of requests currently in the ready, execute or pending
		1459	states (i.e. for which their callback has not been invoked yet).
		1460
		1461	Example: wait till there are no outstanding requests anymore:
		1462
		1463	IO::AIO::poll_wait, IO::AIO::poll_cb
		1464	while IO::AIO::nreqs;
		1465
		1466	=item IO::AIO::nready
		1467
		1468	Returns the number of requests currently in the ready state (not yet
		1469	executed).
		1470
		1471	=item IO::AIO::npending
		1472
		1473	Returns the number of requests currently in the pending state (executed,
		1474	but not yet processed by poll_cb).
		1475
		1476	=back
		1477
		1478	=head3 MISCELLANEOUS FUNCTIONS
		1479
		1480	IO::AIO implements some functions that might be useful, but are not
		1481	asynchronous.
		1482
		1483	=over 4
		1484
		1485	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1486
		1487	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1488	but is blocking (this makes most sense if you know the input data is
		1489	likely cached already and the output filehandle is set to non-blocking
		1490	operations).
		1491
		1492	Returns the number of bytes copied, or C<-1> on error.
		1493
		1494	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1495
		1496	Simply calls the C<posix_fadvise> function (see it's
		1497	manpage for details). The following advice constants are
		1498	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1499	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1500	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1501
		1502	On systems that do not implement C<posix_fadvise>, this function returns
		1503	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1504
		1505	=back
		1506
844	=cut	1507	=cut
845		1508
846	# support function to convert a fd into a perl filehandle
847	sub _fd2fh {
848	return undef if $_[0] < 0;
849
850	# try to generate nice filehandles
851	my $sym = "IO::AIO::fd#$_[0]";
852	local *$sym;
853
854	open *$sym, "+<&=$_[0]" # usually works under any unix
855	or open *$sym, "<&=$_[0]" # cygwin needs this
856	or open *$sym, ">&=$_[0]" # or this
857	or return undef;
858
859	*$sym
860	}
861
862	min_parallel 8;	1509	min_parallel 8;
863		1510
864	END {	1511	END { flush }
865	max_parallel 0;
866	}
867		1512
868	1;	1513	1;
869		1514
870	=head2 FORK BEHAVIOUR	1515	=head2 FORK BEHAVIOUR
871		1516
872	This module should do "the right thing" when the process using it forks:	1517	This module should do "the right thing" when the process using it forks:
873		1518
874	Before the fork, IO::AIO enters a quiescent state where no requests	1519	Before the fork, IO::AIO enters a quiescent state where no requests
875	can be added in other threads and no results will be processed. After	1520	can be added in other threads and no results will be processed. After
876	the fork the parent simply leaves the quiescent state and continues	1521	the fork the parent simply leaves the quiescent state and continues
877	request/result processing, while the child clears the request/result	1522	request/result processing, while the child frees the request/result queue
878	queue (so the requests started before the fork will only be handled in	1523	(so that the requests started before the fork will only be handled in the
879	the parent). Threads will be started on demand until the limit ste in the	1524	parent). Threads will be started on demand until the limit set in the
880	parent process has been reached again.	1525	parent process has been reached again.
881		1526
882	In short: the parent will, after a short pause, continue as if fork had	1527	In short: the parent will, after a short pause, continue as if fork had
883	not been called, while the child will act as if IO::AIO has not been used	1528	not been called, while the child will act as if IO::AIO has not been used
884	yet.	1529	yet.
885		1530
886	=head2 MEMORY USAGE	1531	=head2 MEMORY USAGE
887		1532
		1533	Per-request usage:
		1534
888	Each aio request uses - depending on your architecture - around 128 bytes	1535	Each aio request uses - depending on your architecture - around 100-200
889	of memory. In addition, stat requests need a stat buffer (possibly a few	1536	bytes of memory. In addition, stat requests need a stat buffer (possibly
890	hundred bytes). Perl scalars and other data passed into aio requests will	1537	a few hundred bytes), readdir requires a result buffer and so on. Perl
891	also be locked.	1538	scalars and other data passed into aio requests will also be locked and
		1539	will consume memory till the request has entered the done state.
892		1540
893	This is now awfully much, so queuing lots of requests is not usually a	1541	This is not awfully much, so queuing lots of requests is not usually a
894	problem.	1542	problem.
895		1543
896	Each thread needs a stack area which is usually around 16k, sometimes much	1544	Per-thread usage:
897	larger, depending on the OS.	1545
		1546	In the execution phase, some aio requests require more memory for
		1547	temporary buffers, and each thread requires a stack and other data
		1548	structures (usually around 16k-128k, depending on the OS).
		1549
		1550	=head1 KNOWN BUGS
		1551
		1552	Known bugs will be fixed in the next release.
898		1553
899	=head1 SEE ALSO	1554	=head1 SEE ALSO
900		1555
901	L<Coro::AIO>.	1556	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1557	more natural syntax.
902		1558
903	=head1 AUTHOR	1559	=head1 AUTHOR
904		1560
905	Marc Lehmann <schmorp@schmorp.de>	1561	Marc Lehmann <schmorp@schmorp.de>
906	http://home.schmorp.de/	1562	http://home.schmorp.de/

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