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Revision 1.136 by root, Tue Sep 30 14:07:59 2008 UTC vs.
Revision 1.257 by root, Mon Jan 18 11:53:09 2016 UTC

…		…
4		4
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", IO::AIO::O_RDONLY, 0, sub {
10	my $fh = shift	10	my $fh = shift
11	or die "/etc/passwd: $!";	11	or die "/etc/passwd: $!";
12	...	12	...
13	};	13	};
14		14
…		…
26	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
27		27
28	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
29	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
30		30
31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
32	use AnyEvent::AIO;
33
34	# EV integration
35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
36
37	# Event integration
38	Event->io (fd => IO::AIO::poll_fileno,
39	poll => 'r',
40	cb => \&IO::AIO::poll_cb);
41
42	# Glib/Gtk2 integration
43	add_watch Glib::IO IO::AIO::poll_fileno,
44	in => sub { IO::AIO::poll_cb; 1 };
45
46	# Tk integration
47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
48	readable => \&IO::AIO::poll_cb);
49
50	# Danga::Socket integration
51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
52	\&IO::AIO::poll_cb);
53
54	=head1 DESCRIPTION	31	=head1 DESCRIPTION
55		32
56	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
57	operating system supports.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
58		36
59	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
60	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
61	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
62	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
66	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
67	concurrently.	45	concurrently.
68		46
69	While most of this works on all types of file descriptors (for	47	While most of this works on all types of file descriptors (for
70	example sockets), using these functions on file descriptors that	48	example sockets), using these functions on file descriptors that
71	support nonblocking operation (again, sockets, pipes etc.) is very	49	support nonblocking operation (again, sockets, pipes etc.) is
72	inefficient. Use an event loop for that (such as the L<Event|Event>	50	very inefficient. Use an event loop for that (such as the L<EV>
73	module): IO::AIO will naturally fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
74		52
75	In this version, a number of threads are started that execute your	53	In this version, a number of threads are started that execute your
76	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
77	in perl, and the threads created by this module will not be visible	55	in perl, and the threads created by this module will not be visible
…		…
87	yourself, always call C<poll_cb> from within the same thread, or never	65	yourself, always call C<poll_cb> from within the same thread, or never
88	call C<poll_cb> (or other C<aio_> functions) recursively.	66	call C<poll_cb> (or other C<aio_> functions) recursively.
89		67
90	=head2 EXAMPLE	68	=head2 EXAMPLE
91		69
92	This is a simple example that uses the Event module and loads	70	This is a simple example that uses the EV module and loads
93	F</etc/passwd> asynchronously:	71	F</etc/passwd> asynchronously:
94		72
95	use Fcntl;
96	use Event;	73	use EV;
97	use IO::AIO;	74	use IO::AIO;
98		75
99	# register the IO::AIO callback with Event	76	# register the IO::AIO callback with EV
100	Event->io (fd => IO::AIO::poll_fileno,	77	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
101	poll => 'r',
102	cb => \&IO::AIO::poll_cb);
103		78
104	# queue the request to open /etc/passwd	79	# queue the request to open /etc/passwd
105	aio_open "/etc/passwd", O_RDONLY, 0, sub {	80	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
106	my $fh = shift	81	my $fh = shift
107	or die "error while opening: $!";	82	or die "error while opening: $!";
108		83
109	# stat'ing filehandles is generally non-blocking	84	# stat'ing filehandles is generally non-blocking
110	my $size = -s $fh;	85	my $size = -s $fh;
…		…
119		94
120	# file contents now in $contents	95	# file contents now in $contents
121	print $contents;	96	print $contents;
122		97
123	# exit event loop and program	98	# exit event loop and program
124	Event::unloop;	99	EV::break;
125	};	100	};
126	};	101	};
127		102
128	# possibly queue up other requests, or open GUI windows,	103	# possibly queue up other requests, or open GUI windows,
129	# check for sockets etc. etc.	104	# check for sockets etc. etc.
130		105
131	# process events as long as there are some:	106	# process events as long as there are some:
132	Event::loop;	107	EV::run;
133		108
134	=head1 REQUEST ANATOMY AND LIFETIME	109	=head1 REQUEST ANATOMY AND LIFETIME
135		110
136	Every C<aio_*> function creates a request. which is a C data structure not	111	Every C<aio_*> function creates a request. which is a C data structure not
137	directly visible to Perl.	112	directly visible to Perl.
…		…
187		162
188	package IO::AIO;	163	package IO::AIO;
189		164
190	use Carp ();	165	use Carp ();
191		166
192	no warnings;	167	use common::sense;
193	use strict 'vars';
194		168
195	use base 'Exporter';	169	use base 'Exporter';
196		170
197	BEGIN {	171	BEGIN {
198	our $VERSION = '3.1';	172	our $VERSION = 4.33;
199		173
200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	174	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir	175	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	176	aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
		177	aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_allocate
203	aio_fdatasync aio_pathsync aio_readahead	178	aio_pathsync aio_readahead aio_fiemap
204	aio_rename aio_link aio_move aio_copy aio_group	179	aio_rename aio_link aio_move aio_copy aio_group
205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	180	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
206	aio_chmod aio_utime aio_truncate);	181	aio_chmod aio_utime aio_truncate
		182	aio_msync aio_mtouch aio_mlock aio_mlockall
		183	aio_statvfs
		184	aio_wd);
207		185
208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	186	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	187	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
210	min_parallel max_parallel max_idle	188	min_parallel max_parallel max_idle idle_timeout
211	nreqs nready npending nthreads	189	nreqs nready npending nthreads
212	max_poll_time max_poll_reqs);	190	max_poll_time max_poll_reqs
		191	sendfile fadvise madvise
		192	mmap munmap munlock munlockall);
		193
		194	push @AIO_REQ, qw(aio_busy); # not exported
213		195
214	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	196	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
215		197
216	require XSLoader;	198	require XSLoader;
217	XSLoader::load ("IO::AIO", $VERSION);	199	XSLoader::load ("IO::AIO", $VERSION);
218	}	200	}
219		201
220	=head1 FUNCTIONS	202	=head1 FUNCTIONS
221		203
222	=head2 AIO REQUEST FUNCTIONS	204	=head2 QUICK OVERVIEW
		205
		206	This section simply lists the prototypes most of the functions for
		207	quick reference. See the following sections for function-by-function
		208	documentation.
		209
		210	aio_wd $pathname, $callback->($wd)
		211	aio_open $pathname, $flags, $mode, $callback->($fh)
		212	aio_close $fh, $callback->($status)
		213	aio_seek $fh,$offset,$whence, $callback->($offs)
		214	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		215	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		216	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		217	aio_readahead $fh,$offset,$length, $callback->($retval)
		218	aio_stat $fh_or_path, $callback->($status)
		219	aio_lstat $fh, $callback->($status)
		220	aio_statvfs $fh_or_path, $callback->($statvfs)
		221	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		222	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		223	aio_chmod $fh_or_path, $mode, $callback->($status)
		224	aio_truncate $fh_or_path, $offset, $callback->($status)
		225	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		226	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		227	aio_unlink $pathname, $callback->($status)
		228	aio_mknod $pathname, $mode, $dev, $callback->($status)
		229	aio_link $srcpath, $dstpath, $callback->($status)
		230	aio_symlink $srcpath, $dstpath, $callback->($status)
		231	aio_readlink $pathname, $callback->($link)
		232	aio_realpath $pathname, $callback->($path)
		233	aio_rename $srcpath, $dstpath, $callback->($status)
		234	aio_mkdir $pathname, $mode, $callback->($status)
		235	aio_rmdir $pathname, $callback->($status)
		236	aio_readdir $pathname, $callback->($entries)
		237	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		238	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		239	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		240	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		241	aio_load $pathname, $data, $callback->($status)
		242	aio_copy $srcpath, $dstpath, $callback->($status)
		243	aio_move $srcpath, $dstpath, $callback->($status)
		244	aio_rmtree $pathname, $callback->($status)
		245	aio_sync $callback->($status)
		246	aio_syncfs $fh, $callback->($status)
		247	aio_fsync $fh, $callback->($status)
		248	aio_fdatasync $fh, $callback->($status)
		249	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		250	aio_pathsync $pathname, $callback->($status)
		251	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		252	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		253	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		254	aio_mlockall $flags, $callback->($status)
		255	aio_group $callback->(...)
		256	aio_nop $callback->()
		257
		258	$prev_pri = aioreq_pri [$pri]
		259	aioreq_nice $pri_adjust
		260
		261	IO::AIO::poll_wait
		262	IO::AIO::poll_cb
		263	IO::AIO::poll
		264	IO::AIO::flush
		265	IO::AIO::max_poll_reqs $nreqs
		266	IO::AIO::max_poll_time $seconds
		267	IO::AIO::min_parallel $nthreads
		268	IO::AIO::max_parallel $nthreads
		269	IO::AIO::max_idle $nthreads
		270	IO::AIO::idle_timeout $seconds
		271	IO::AIO::max_outstanding $maxreqs
		272	IO::AIO::nreqs
		273	IO::AIO::nready
		274	IO::AIO::npending
		275
		276	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		277	IO::AIO::fadvise $fh, $offset, $len, $advice
		278	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		279	IO::AIO::munmap $scalar
		280	IO::AIO::madvise $scalar, $offset, $length, $advice
		281	IO::AIO::mprotect $scalar, $offset, $length, $protect
		282	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		283	IO::AIO::munlockall
		284
		285	=head2 API NOTES
223		286
224	All the C<aio_*> calls are more or less thin wrappers around the syscall	287	All the C<aio_*> calls are more or less thin wrappers around the syscall
225	with the same name (sans C<aio_>). The arguments are similar or identical,	288	with the same name (sans C<aio_>). The arguments are similar or identical,
226	and they all accept an additional (and optional) C<$callback> argument	289	and they all accept an additional (and optional) C<$callback> argument
227	which must be a code reference. This code reference will get called with	290	which must be a code reference. This code reference will be called after
228	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	291	the syscall has been executed in an asynchronous fashion. The results
229	perl, which usually delivers "false") as its sole argument after the given	292	of the request will be passed as arguments to the callback (and, if an
230	syscall has been executed asynchronously.	293	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		294	most syscalls return C<-1> on error, unlike perl, which usually delivers
		295	"false").
		296
		297	Some requests (such as C<aio_readdir>) pass the actual results and
		298	communicate failures by passing C<undef>.
231		299
232	All functions expecting a filehandle keep a copy of the filehandle	300	All functions expecting a filehandle keep a copy of the filehandle
233	internally until the request has finished.	301	internally until the request has finished.
234		302
235	All functions return request objects of type L<IO::AIO::REQ> that allow	303	All functions return request objects of type L<IO::AIO::REQ> that allow
236	further manipulation of those requests while they are in-flight.	304	further manipulation of those requests while they are in-flight.
237		305
238	The pathnames you pass to these routines I<must> be absolute and	306	The pathnames you pass to these routines I<should> be absolute. The
239	encoded as octets. The reason for the former is that at the time the	307	reason for this is that at the time the request is being executed, the
240	request is being executed, the current working directory could have	308	current working directory could have changed. Alternatively, you can
241	changed. Alternatively, you can make sure that you never change the	309	make sure that you never change the current working directory anywhere
242	current working directory anywhere in the program and then use relative	310	in the program and then use relative paths. You can also take advantage
243	paths.	311	of IO::AIOs working directory abstraction, that lets you specify paths
		312	relative to some previously-opened "working directory object" - see the
		313	description of the C<IO::AIO::WD> class later in this document.
244		314
245	To encode pathnames as octets, either make sure you either: a) always pass	315	To encode pathnames as octets, either make sure you either: a) always pass
246	in filenames you got from outside (command line, readdir etc.) without	316	in filenames you got from outside (command line, readdir etc.) without
247	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	317	tinkering, b) are in your native filesystem encoding, c) use the Encode
248	your pathnames to the locale (or other) encoding in effect in the user	318	module and encode your pathnames to the locale (or other) encoding in
249	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	319	effect in the user environment, d) use Glib::filename_from_unicode on
250	use something else to ensure your scalar has the correct contents.	320	unicode filenames or e) use something else to ensure your scalar has the
		321	correct contents.
251		322
252	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	323	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
253	handles correctly whether it is set or not.	324	handles correctly whether it is set or not.
		325
		326	=head2 AIO REQUEST FUNCTIONS
254		327
255	=over 4	328	=over 4
256		329
257	=item $prev_pri = aioreq_pri [$pri]	330	=item $prev_pri = aioreq_pri [$pri]
258		331
…		…
288		361
289		362
290	=item aio_open $pathname, $flags, $mode, $callback->($fh)	363	=item aio_open $pathname, $flags, $mode, $callback->($fh)
291		364
292	Asynchronously open or create a file and call the callback with a newly	365	Asynchronously open or create a file and call the callback with a newly
293	created filehandle for the file.	366	created filehandle for the file (or C<undef> in case of an error).
294		367
295	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	368	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
296	for an explanation.	369	for an explanation.
297		370
298	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	371	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
305	by the umask in effect then the request is being executed, so better never	378	by the umask in effect then the request is being executed, so better never
306	change the umask.	379	change the umask.
307		380
308	Example:	381	Example:
309		382
310	aio_open "/etc/passwd", O_RDONLY, 0, sub {	383	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
311	if ($_[0]) {	384	if ($_[0]) {
312	print "open successful, fh is $_[0]\n";	385	print "open successful, fh is $_[0]\n";
313	...	386	...
314	} else {	387	} else {
315	die "open failed: $!\n";	388	die "open failed: $!\n";
316	}	389	}
317	};	390	};
318		391
		392	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		393	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		394	following POSIX and non-POSIX constants are available (missing ones on
		395	your system are, as usual, C<0>):
		396
		397	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		398	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		399	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		400
319		401
320	=item aio_close $fh, $callback->($status)	402	=item aio_close $fh, $callback->($status)
321		403
322	Asynchronously close a file and call the callback with the result	404	Asynchronously close a file and call the callback with the result
323	code.	405	code.
…		…
332	Or in other words: the file descriptor will be closed, but it will not be	414	Or in other words: the file descriptor will be closed, but it will not be
333	free for reuse until the perl filehandle is closed.	415	free for reuse until the perl filehandle is closed.
334		416
335	=cut	417	=cut
336		418
		419	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		420
		421	Seeks the filehandle to the new C<$offset>, similarly to perl's
		422	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		423	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		424	C<IO::AIO::SEEK_END>).
		425
		426	The resulting absolute offset will be passed to the callback, or C<-1> in
		427	case of an error.
		428
		429	In theory, the C<$whence> constants could be different than the
		430	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		431	so don't panic.
		432
		433	As a GNU/Linux (and maybe Solaris) extension, also the constants
		434	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		435	could be found. No guarantees about suitability for use in C<aio_seek> or
		436	Perl's C<sysseek> can be made though, although I would naively assume they
		437	"just work".
		438
337	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	439	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
338		440
339	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	441	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
340		442
341	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>	443	Reads or writes C<$length> bytes from or to the specified C<$fh> and
342	into the scalar given by C<$data> and offset C<$dataoffset> and calls the	444	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
343	callback without the actual number of bytes read (or -1 on error, just	445	and calls the callback without the actual number of bytes read (or -1 on
344	like the syscall).	446	error, just like the syscall).
		447
		448	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		449	offset plus the actual number of bytes read.
345		450
346	If C<$offset> is undefined, then the current file descriptor offset will	451	If C<$offset> is undefined, then the current file descriptor offset will
347	be used (and updated), otherwise the file descriptor offset will not be	452	be used (and updated), otherwise the file descriptor offset will not be
348	changed by these calls.	453	changed by these calls.
349		454
350	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.	455	If C<$length> is undefined in C<aio_write>, use the remaining length of
		456	C<$data>.
351		457
352	If C<$dataoffset> is less than zero, it will be counted from the end of	458	If C<$dataoffset> is less than zero, it will be counted from the end of
353	C<$data>.	459	C<$data>.
354		460
355	The C<$data> scalar I<MUST NOT> be modified in any way while the request	461	The C<$data> scalar I<MUST NOT> be modified in any way while the request
…		…
369		475
370	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	476	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
371	reading at byte offset C<$in_offset>, and starts writing at the current	477	reading at byte offset C<$in_offset>, and starts writing at the current
372	file offset of C<$out_fh>. Because of that, it is not safe to issue more	478	file offset of C<$out_fh>. Because of that, it is not safe to issue more
373	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	479	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
374	other.	480	other. The same C<$in_fh> works fine though, as this function does not
		481	move or use the file offset of C<$in_fh>.
375		482
		483	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		484	are written, and there is no way to find out how many more bytes have been
		485	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		486	number of bytes written to C<$out_fh>. Only if the result value equals
		487	C<$length> one can assume that C<$length> bytes have been read.
		488
		489	Unlike with other C<aio_> functions, it makes a lot of sense to use
		490	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		491	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		492	the socket I/O will be non-blocking. Note, however, that you can run
		493	into a trap where C<aio_sendfile> reads some data with readahead, then
		494	fails to write all data, and when the socket is ready the next time, the
		495	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		496	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		497	resource usage.
		498
376	This call tries to make use of a native C<sendfile> syscall to provide	499	This call tries to make use of a native C<sendfile>-like syscall to
377	zero-copy operation. For this to work, C<$out_fh> should refer to a	500	provide zero-copy operation. For this to work, C<$out_fh> should refer to
378	socket, and C<$in_fh> should refer to mmap'able file.	501	a socket, and C<$in_fh> should refer to an mmap'able file.
379		502
380	If the native sendfile call fails or is not implemented, it will be	503	If a native sendfile cannot be found or it fails with C<ENOSYS>,
381	emulated, so you can call C<aio_sendfile> on any type of filehandle	504	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		505	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
382	regardless of the limitations of the operating system.	506	type of filehandle regardless of the limitations of the operating system.
383		507
384	Please note, however, that C<aio_sendfile> can read more bytes from	508	As native sendfile syscalls (as practically any non-POSIX interface hacked
385	C<$in_fh> than are written, and there is no way to find out how many	509	together in a hurry to improve benchmark numbers) tend to be rather buggy
386	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	510	on many systems, this implementation tries to work around some known bugs
387	provides the number of bytes written to C<$out_fh>. Only if the result	511	in Linux and FreeBSD kernels (probably others, too), but that might fail,
388	value equals C<$length> one can assume that C<$length> bytes have been	512	so you really really should check the return value of C<aio_sendfile> -
389	read.	513	fewre bytes than expected might have been transferred.
390		514
391		515
392	=item aio_readahead $fh,$offset,$length, $callback->($retval)	516	=item aio_readahead $fh,$offset,$length, $callback->($retval)
393		517
394	C<aio_readahead> populates the page cache with data from a file so that	518	C<aio_readahead> populates the page cache with data from a file so that
…		…
417		541
418	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	542	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
419	error when stat'ing a large file, the results will be silently truncated	543	error when stat'ing a large file, the results will be silently truncated
420	unless perl itself is compiled with large file support.	544	unless perl itself is compiled with large file support.
421		545
		546	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		547	following constants and functions (if not implemented, the constants will
		548	be C<0> and the functions will either C<croak> or fall back on traditional
		549	behaviour).
		550
		551	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		552	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		553	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		554
422	Example: Print the length of F</etc/passwd>:	555	Example: Print the length of F</etc/passwd>:
423		556
424	aio_stat "/etc/passwd", sub {	557	aio_stat "/etc/passwd", sub {
425	$_[0] and die "stat failed: $!";	558	$_[0] and die "stat failed: $!";
426	print "size is ", -s _, "\n";	559	print "size is ", -s _, "\n";
427	};	560	};
428		561
429		562
		563	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		564
		565	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		566	whether a file handle or path was passed.
		567
		568	On success, the callback is passed a hash reference with the following
		569	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		570	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		571	is passed.
		572
		573	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		574	C<ST_NOSUID>.
		575
		576	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		577	their correct value when available, or to C<0> on systems that do
		578	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		579	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		580	C<ST_NODIRATIME> and C<ST_RELATIME>.
		581
		582	Example: stat C</wd> and dump out the data if successful.
		583
		584	aio_statvfs "/wd", sub {
		585	my $f = $_[0]
		586	or die "statvfs: $!";
		587
		588	use Data::Dumper;
		589	say Dumper $f;
		590	};
		591
		592	# result:
		593	{
		594	bsize => 1024,
		595	bfree => 4333064312,
		596	blocks => 10253828096,
		597	files => 2050765568,
		598	flag => 4096,
		599	favail => 2042092649,
		600	bavail => 4333064312,
		601	ffree => 2042092649,
		602	namemax => 255,
		603	frsize => 1024,
		604	fsid => 1810
		605	}
		606
		607	Here is a (likely partial - send me updates!) list of fsid values used by
		608	Linux - it is safe to hardcode these when C<$^O> is C<linux>:
		609
		610	0x0000adf5 adfs
		611	0x0000adff affs
		612	0x5346414f afs
		613	0x09041934 anon-inode filesystem
		614	0x00000187 autofs
		615	0x42465331 befs
		616	0x1badface bfs
		617	0x42494e4d binfmt_misc
		618	0x9123683e btrfs
		619	0x0027e0eb cgroupfs
		620	0xff534d42 cifs
		621	0x73757245 coda
		622	0x012ff7b7 coh
		623	0x28cd3d45 cramfs
		624	0x453dcd28 cramfs-wend (wrong endianness)
		625	0x64626720 debugfs
		626	0x00001373 devfs
		627	0x00001cd1 devpts
		628	0x0000f15f ecryptfs
		629	0x00414a53 efs
		630	0x0000137d ext
		631	0x0000ef53 ext2/ext3/ext4
		632	0x0000ef51 ext2
		633	0xf2f52010 f2fs
		634	0x00004006 fat
		635	0x65735546 fuseblk
		636	0x65735543 fusectl
		637	0x0bad1dea futexfs
		638	0x01161970 gfs2
		639	0x47504653 gpfs
		640	0x00004244 hfs
		641	0xf995e849 hpfs
		642	0x00c0ffee hostfs
		643	0x958458f6 hugetlbfs
		644	0x2bad1dea inotifyfs
		645	0x00009660 isofs
		646	0x000072b6 jffs2
		647	0x3153464a jfs
		648	0x6b414653 k-afs
		649	0x0bd00bd0 lustre
		650	0x0000137f minix
		651	0x0000138f minix 30 char names
		652	0x00002468 minix v2
		653	0x00002478 minix v2 30 char names
		654	0x00004d5a minix v3
		655	0x19800202 mqueue
		656	0x00004d44 msdos
		657	0x0000564c novell
		658	0x00006969 nfs
		659	0x6e667364 nfsd
		660	0x00003434 nilfs
		661	0x5346544e ntfs
		662	0x00009fa1 openprom
		663	0x7461636F ocfs2
		664	0x00009fa0 proc
		665	0x6165676c pstorefs
		666	0x0000002f qnx4
		667	0x68191122 qnx6
		668	0x858458f6 ramfs
		669	0x52654973 reiserfs
		670	0x00007275 romfs
		671	0x67596969 rpc_pipefs
		672	0x73636673 securityfs
		673	0xf97cff8c selinux
		674	0x0000517b smb
		675	0x534f434b sockfs
		676	0x73717368 squashfs
		677	0x62656572 sysfs
		678	0x012ff7b6 sysv2
		679	0x012ff7b5 sysv4
		680	0x01021994 tmpfs
		681	0x15013346 udf
		682	0x00011954 ufs
		683	0x54190100 ufs byteswapped
		684	0x00009fa2 usbdevfs
		685	0x01021997 v9fs
		686	0xa501fcf5 vxfs
		687	0xabba1974 xenfs
		688	0x012ff7b4 xenix
		689	0x58465342 xfs
		690	0x012fd16d xia
		691
430	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	692	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
431		693
432	Works like perl's C<utime> function (including the special case of $atime	694	Works like perl's C<utime> function (including the special case of $atime
433	and $mtime being undef). Fractional times are supported if the underlying	695	and $mtime being undef). Fractional times are supported if the underlying
434	syscalls support them.	696	syscalls support them.
…		…
461	=item aio_truncate $fh_or_path, $offset, $callback->($status)	723	=item aio_truncate $fh_or_path, $offset, $callback->($status)
462		724
463	Works like truncate(2) or ftruncate(2).	725	Works like truncate(2) or ftruncate(2).
464		726
465		727
		728	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		729
		730	Allocates or frees disk space according to the C<$mode> argument. See the
		731	linux C<fallocate> documentation for details.
		732
		733	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		734	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		735	to deallocate a file range.
		736
		737	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		738	(without leaving a hole) and C<FALLOC_FL_ZERO_RANGE>, to zero a range (see
		739	your L<fallocate(2)> manpage).
		740
		741	The file system block size used by C<fallocate> is presumably the
		742	C<f_bsize> returned by C<statvfs>.
		743
		744	If C<fallocate> isn't available or cannot be emulated (currently no
		745	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		746
		747
466	=item aio_chmod $fh_or_path, $mode, $callback->($status)	748	=item aio_chmod $fh_or_path, $mode, $callback->($status)
467		749
468	Works like perl's C<chmod> function.	750	Works like perl's C<chmod> function.
469		751
470		752
…		…
472		754
473	Asynchronously unlink (delete) a file and call the callback with the	755	Asynchronously unlink (delete) a file and call the callback with the
474	result code.	756	result code.
475		757
476		758
477	=item aio_mknod $path, $mode, $dev, $callback->($status)	759	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
478		760
479	[EXPERIMENTAL]	761	[EXPERIMENTAL]
480		762
481	Asynchronously create a device node (or fifo). See mknod(2).	763	Asynchronously create a device node (or fifo). See mknod(2).
482		764
483	The only (POSIX-) portable way of calling this function is:	765	The only (POSIX-) portable way of calling this function is:
484		766
485	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	767	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
486		768
		769	See C<aio_stat> for info about some potentially helpful extra constants
		770	and functions.
487		771
488	=item aio_link $srcpath, $dstpath, $callback->($status)	772	=item aio_link $srcpath, $dstpath, $callback->($status)
489		773
490	Asynchronously create a new link to the existing object at C<$srcpath> at	774	Asynchronously create a new link to the existing object at C<$srcpath> at
491	the path C<$dstpath> and call the callback with the result code.	775	the path C<$dstpath> and call the callback with the result code.
…		…
495		779
496	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	780	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
497	the path C<$dstpath> and call the callback with the result code.	781	the path C<$dstpath> and call the callback with the result code.
498		782
499		783
500	=item aio_readlink $path, $callback->($link)	784	=item aio_readlink $pathname, $callback->($link)
501		785
502	Asynchronously read the symlink specified by C<$path> and pass it to	786	Asynchronously read the symlink specified by C<$path> and pass it to
503	the callback. If an error occurs, nothing or undef gets passed to the	787	the callback. If an error occurs, nothing or undef gets passed to the
504	callback.	788	callback.
505		789
506		790
		791	=item aio_realpath $pathname, $callback->($path)
		792
		793	Asynchronously make the path absolute and resolve any symlinks in
		794	C<$path>. The resulting path only consists of directories (same as
		795	L<Cwd::realpath>).
		796
		797	This request can be used to get the absolute path of the current working
		798	directory by passing it a path of F<.> (a single dot).
		799
		800
507	=item aio_rename $srcpath, $dstpath, $callback->($status)	801	=item aio_rename $srcpath, $dstpath, $callback->($status)
508		802
509	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	803	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
510	rename(2) and call the callback with the result code.	804	rename(2) and call the callback with the result code.
		805
		806	On systems that support the AIO::WD working directory abstraction
		807	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		808	of failing, C<rename> is called on the absolute path of C<$wd>.
511		809
512		810
513	=item aio_mkdir $pathname, $mode, $callback->($status)	811	=item aio_mkdir $pathname, $mode, $callback->($status)
514		812
515	Asynchronously mkdir (create) a directory and call the callback with	813	Asynchronously mkdir (create) a directory and call the callback with
…		…
520	=item aio_rmdir $pathname, $callback->($status)	818	=item aio_rmdir $pathname, $callback->($status)
521		819
522	Asynchronously rmdir (delete) a directory and call the callback with the	820	Asynchronously rmdir (delete) a directory and call the callback with the
523	result code.	821	result code.
524		822
		823	On systems that support the AIO::WD working directory abstraction
		824	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		825	C<rmdir> is called on the absolute path of C<$wd>.
		826
525		827
526	=item aio_readdir $pathname, $callback->($entries)	828	=item aio_readdir $pathname, $callback->($entries)
527		829
528	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	830	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
529	directory (i.e. opendir + readdir + closedir). The entries will not be	831	directory (i.e. opendir + readdir + closedir). The entries will not be
530	sorted, and will B<NOT> include the C<.> and C<..> entries.	832	sorted, and will B<NOT> include the C<.> and C<..> entries.
531		833
532	The callback a single argument which is either C<undef> or an array-ref	834	The callback is passed a single argument which is either C<undef> or an
533	with the filenames.	835	array-ref with the filenames.
534		836
535		837
		838	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		839
		840	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		841	tune behaviour and output format. In case of an error, C<$entries> will be
		842	C<undef>.
		843
		844	The flags are a combination of the following constants, ORed together (the
		845	flags will also be passed to the callback, possibly modified):
		846
		847	=over 4
		848
		849	=item IO::AIO::READDIR_DENTS
		850
		851	When this flag is off, then the callback gets an arrayref consisting of
		852	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		853	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		854	entry in more detail.
		855
		856	C<$name> is the name of the entry.
		857
		858	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		859
		860	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		861	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		862	C<IO::AIO::DT_WHT>.
		863
		864	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		865	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		866	scalars are read-only: you can not modify them.
		867
		868	C<$inode> is the inode number (which might not be exact on systems with 64
		869	bit inode numbers and 32 bit perls). This field has unspecified content on
		870	systems that do not deliver the inode information.
		871
		872	=item IO::AIO::READDIR_DIRS_FIRST
		873
		874	When this flag is set, then the names will be returned in an order where
		875	likely directories come first, in optimal stat order. This is useful when
		876	you need to quickly find directories, or you want to find all directories
		877	while avoiding to stat() each entry.
		878
		879	If the system returns type information in readdir, then this is used
		880	to find directories directly. Otherwise, likely directories are names
		881	beginning with ".", or otherwise names with no dots, of which names with
		882	short names are tried first.
		883
		884	=item IO::AIO::READDIR_STAT_ORDER
		885
		886	When this flag is set, then the names will be returned in an order
		887	suitable for stat()'ing each one. That is, when you plan to stat()
		888	all files in the given directory, then the returned order will likely
		889	be fastest.
		890
		891	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		892	the likely dirs come first, resulting in a less optimal stat order.
		893
		894	=item IO::AIO::READDIR_FOUND_UNKNOWN
		895
		896	This flag should not be set when calling C<aio_readdirx>. Instead, it
		897	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		898	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		899	C<$type>'s are known, which can be used to speed up some algorithms.
		900
		901	=back
		902
		903
536	=item aio_load $path, $data, $callback->($status)	904	=item aio_load $pathname, $data, $callback->($status)
537		905
538	This is a composite request that tries to fully load the given file into	906	This is a composite request that tries to fully load the given file into
539	memory. Status is the same as with aio_read.	907	memory. Status is the same as with aio_read.
540		908
541	=cut	909	=cut
…		…
563		931
564	=item aio_copy $srcpath, $dstpath, $callback->($status)	932	=item aio_copy $srcpath, $dstpath, $callback->($status)
565		933
566	Try to copy the I<file> (directories not supported as either source or	934	Try to copy the I<file> (directories not supported as either source or
567	destination) from C<$srcpath> to C<$dstpath> and call the callback with	935	destination) from C<$srcpath> to C<$dstpath> and call the callback with
568	the C<0> (error) or C<-1> ok.	936	a status of C<0> (ok) or C<-1> (error, see C<$!>).
569		937
570	This is a composite request that creates the destination file with	938	This is a composite request that creates the destination file with
571	mode 0200 and copies the contents of the source file into it using	939	mode 0200 and copies the contents of the source file into it using
572	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	940	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
573	uid/gid, in that order.	941	uid/gid, in that order.
…		…
585	my $grp = aio_group $cb;	953	my $grp = aio_group $cb;
586		954
587	aioreq_pri $pri;	955	aioreq_pri $pri;
588	add $grp aio_open $src, O_RDONLY, 0, sub {	956	add $grp aio_open $src, O_RDONLY, 0, sub {
589	if (my $src_fh = $_[0]) {	957	if (my $src_fh = $_[0]) {
590	my @stat = stat $src_fh;	958	my @stat = stat $src_fh; # hmm, might block over nfs?
591		959
592	aioreq_pri $pri;	960	aioreq_pri $pri;
593	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	961	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
594	if (my $dst_fh = $_[0]) {	962	if (my $dst_fh = $_[0]) {
595	aioreq_pri $pri;	963	aioreq_pri $pri;
596	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	964	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
597	if ($_[0] == $stat[7]) {	965	if ($_[0] == $stat[7]) {
598	$grp->result (0);	966	$grp->result (0);
599	close $src_fh;	967	close $src_fh;
600		968
601	# those should not normally block. should. should.	969	my $ch = sub {
602	utime $stat[8], $stat[9], $dst;	970	aioreq_pri $pri;
603	chmod $stat[2] & 07777, $dst_fh;	971	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
604	chown $stat[4], $stat[5], $dst_fh;	972	aioreq_pri $pri;
		973	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		974	aioreq_pri $pri;
		975	add $grp aio_close $dst_fh;
		976	}
		977	};
		978	};
605		979
606	aioreq_pri $pri;	980	aioreq_pri $pri;
607	add $grp aio_close $dst_fh;	981	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		982	if ($_[0] < 0 && $! == ENOSYS) {
		983	aioreq_pri $pri;
		984	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		985	} else {
		986	$ch->();
		987	}
		988	};
608	} else {	989	} else {
609	$grp->result (-1);	990	$grp->result (-1);
610	close $src_fh;	991	close $src_fh;
611	close $dst_fh;	992	close $dst_fh;
612		993
…		…
629		1010
630	=item aio_move $srcpath, $dstpath, $callback->($status)	1011	=item aio_move $srcpath, $dstpath, $callback->($status)
631		1012
632	Try to move the I<file> (directories not supported as either source or	1013	Try to move the I<file> (directories not supported as either source or
633	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1014	destination) from C<$srcpath> to C<$dstpath> and call the callback with
634	the C<0> (error) or C<-1> ok.	1015	a status of C<0> (ok) or C<-1> (error, see C<$!>).
635		1016
636	This is a composite request that tries to rename(2) the file first. If	1017	This is a composite request that tries to rename(2) the file first; if
637	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1018	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
638	that is successful, unlinking the C<$srcpath>.	1019	that is successful, unlinks the C<$srcpath>.
639		1020
640	=cut	1021	=cut
641		1022
642	sub aio_move($$;$) {	1023	sub aio_move($$;$) {
643	my ($src, $dst, $cb) = @_;	1024	my ($src, $dst, $cb) = @_;
…		…
650	if ($_[0] && $! == EXDEV) {	1031	if ($_[0] && $! == EXDEV) {
651	aioreq_pri $pri;	1032	aioreq_pri $pri;
652	add $grp aio_copy $src, $dst, sub {	1033	add $grp aio_copy $src, $dst, sub {
653	$grp->result ($_[0]);	1034	$grp->result ($_[0]);
654		1035
655	if (!$_[0]) {	1036	unless ($_[0]) {
656	aioreq_pri $pri;	1037	aioreq_pri $pri;
657	add $grp aio_unlink $src;	1038	add $grp aio_unlink $src;
658	}	1039	}
659	};	1040	};
660	} else {	1041	} else {
…		…
663	};	1044	};
664		1045
665	$grp	1046	$grp
666	}	1047	}
667		1048
668	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1049	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
669		1050
670	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1051	Scans a directory (similar to C<aio_readdir>) but additionally tries to
671	efficiently separate the entries of directory C<$path> into two sets of	1052	efficiently separate the entries of directory C<$path> into two sets of
672	names, directories you can recurse into (directories), and ones you cannot	1053	names, directories you can recurse into (directories), and ones you cannot
673	recurse into (everything else, including symlinks to directories).	1054	recurse into (everything else, including symlinks to directories).
…		…
690		1071
691	Implementation notes.	1072	Implementation notes.
692		1073
693	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1074	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
694		1075
		1076	If readdir returns file type information, then this is used directly to
		1077	find directories.
		1078
695	After reading the directory, the modification time, size etc. of the	1079	Otherwise, after reading the directory, the modification time, size etc.
696	directory before and after the readdir is checked, and if they match (and	1080	of the directory before and after the readdir is checked, and if they
697	isn't the current time), the link count will be used to decide how many	1081	match (and isn't the current time), the link count will be used to decide
698	entries are directories (if >= 2). Otherwise, no knowledge of the number	1082	how many entries are directories (if >= 2). Otherwise, no knowledge of the
699	of subdirectories will be assumed.	1083	number of subdirectories will be assumed.
700		1084
701	Then entries will be sorted into likely directories (everything without	1085	Then entries will be sorted into likely directories a non-initial dot
702	a non-initial dot currently) and likely non-directories (everything	1086	currently) and likely non-directories (see C<aio_readdirx>). Then every
703	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1087	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
704	likely directories first. If that succeeds, it assumes that the entry	1088	in order of their inode numbers. If that succeeds, it assumes that the
705	is a directory or a symlink to directory (which will be checked	1089	entry is a directory or a symlink to directory (which will be checked
706	seperately). This is often faster than stat'ing the entry itself because	1090	separately). This is often faster than stat'ing the entry itself because
707	filesystems might detect the type of the entry without reading the inode	1091	filesystems might detect the type of the entry without reading the inode
708	data (e.g. ext2fs filetype feature).	1092	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1093	the filetype information on readdir.
709		1094
710	If the known number of directories (link count - 2) has been reached, the	1095	If the known number of directories (link count - 2) has been reached, the
711	rest of the entries is assumed to be non-directories.	1096	rest of the entries is assumed to be non-directories.
712		1097
713	This only works with certainty on POSIX (= UNIX) filesystems, which	1098	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
726		1111
727	my $grp = aio_group $cb;	1112	my $grp = aio_group $cb;
728		1113
729	$maxreq = 4 if $maxreq <= 0;	1114	$maxreq = 4 if $maxreq <= 0;
730		1115
731	# stat once	1116	# get a wd object
732	aioreq_pri $pri;	1117	aioreq_pri $pri;
733	add $grp aio_stat $path, sub {	1118	add $grp aio_wd $path, sub {
		1119	$_[0]
734	return $grp->result () if $_[0];	1120	or return $grp->result ();
735	my $now = time;
736	my $hash1 = join ":", (stat _)[0,1,3,7,9];
737		1121
738	# read the directory entries	1122	my $wd = [shift, "."];
		1123
		1124	# stat once
739	aioreq_pri $pri;	1125	aioreq_pri $pri;
740	add $grp aio_readdir $path, sub {	1126	add $grp aio_stat $wd, sub {
741	my $entries = shift
742	or return $grp->result ();	1127	return $grp->result () if $_[0];
		1128	my $now = time;
		1129	my $hash1 = join ":", (stat _)[0,1,3,7,9];
743		1130
744	# stat the dir another time	1131	# read the directory entries
745	aioreq_pri $pri;	1132	aioreq_pri $pri;
		1133	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1134	my $entries = shift
		1135	or return $grp->result ();
		1136
		1137	# stat the dir another time
		1138	aioreq_pri $pri;
746	add $grp aio_stat $path, sub {	1139	add $grp aio_stat $wd, sub {
747	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1140	my $hash2 = join ":", (stat _)[0,1,3,7,9];
748		1141
749	my $ndirs;	1142	my $ndirs;
750		1143
751	# take the slow route if anything looks fishy	1144	# take the slow route if anything looks fishy
752	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1145	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
753	$ndirs = -1;	1146	$ndirs = -1;
754	} else {	1147	} else {
755	# if nlink == 2, we are finished	1148	# if nlink == 2, we are finished
756	# on non-posix-fs's, we rely on nlink < 2	1149	# for non-posix-fs's, we rely on nlink < 2
757	$ndirs = (stat _)[3] - 2	1150	$ndirs = (stat _)[3] - 2
758	or return $grp->result ([], $entries);	1151	or return $grp->result ([], $entries);
759	}	1152	}
760		1153
761	# sort into likely dirs and likely nondirs
762	# dirs == files without ".", short entries first
763	$entries = [map $_->[0],
764	sort { $b->[1] cmp $a->[1] }
765	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
766	@$entries];
767
768	my (@dirs, @nondirs);	1154	my (@dirs, @nondirs);
769		1155
770	my $statgrp = add $grp aio_group sub {	1156	my $statgrp = add $grp aio_group sub {
771	$grp->result (\@dirs, \@nondirs);	1157	$grp->result (\@dirs, \@nondirs);
772	};	1158	};
773		1159
774	limit $statgrp $maxreq;	1160	limit $statgrp $maxreq;
775	feed $statgrp sub {	1161	feed $statgrp sub {
776	return unless @$entries;	1162	return unless @$entries;
777	my $entry = pop @$entries;	1163	my $entry = shift @$entries;
778		1164
779	aioreq_pri $pri;	1165	aioreq_pri $pri;
		1166	$wd->[1] = "$entry/.";
780	add $statgrp aio_stat "$path/$entry/.", sub {	1167	add $statgrp aio_stat $wd, sub {
781	if ($_[0] < 0) {	1168	if ($_[0] < 0) {
782	push @nondirs, $entry;	1169	push @nondirs, $entry;
783	} else {	1170	} else {
784	# need to check for real directory	1171	# need to check for real directory
785	aioreq_pri $pri;	1172	aioreq_pri $pri;
		1173	$wd->[1] = $entry;
786	add $statgrp aio_lstat "$path/$entry", sub {	1174	add $statgrp aio_lstat $wd, sub {
787	if (-d _) {	1175	if (-d _) {
788	push @dirs, $entry;	1176	push @dirs, $entry;
789		1177
790	unless (--$ndirs) {	1178	unless (--$ndirs) {
791	push @nondirs, @$entries;	1179	push @nondirs, @$entries;
792	feed $statgrp;	1180	feed $statgrp;
		1181	}
		1182	} else {
		1183	push @nondirs, $entry;
793	}	1184	}
794	} else {
795	push @nondirs, $entry;
796	}	1185	}
797	}	1186	}
798	}	1187	};
799	};	1188	};
800	};	1189	};
801	};	1190	};
802	};	1191	};
803	};	1192	};
804		1193
805	$grp	1194	$grp
806	}	1195	}
807		1196
808	=item aio_rmtree $path, $callback->($status)	1197	=item aio_rmtree $pathname, $callback->($status)
809		1198
810	Delete a directory tree starting (and including) C<$path>, return the	1199	Delete a directory tree starting (and including) C<$path>, return the
811	status of the final C<rmdir> only. This is a composite request that	1200	status of the final C<rmdir> only. This is a composite request that
812	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1201	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
813	everything else.	1202	everything else.
814		1203
815	=cut	1204	=cut
816		1205
…		…
855	callback with the fdatasync result code.	1244	callback with the fdatasync result code.
856		1245
857	If this call isn't available because your OS lacks it or it couldn't be	1246	If this call isn't available because your OS lacks it or it couldn't be
858	detected, it will be emulated by calling C<fsync> instead.	1247	detected, it will be emulated by calling C<fsync> instead.
859		1248
		1249	=item aio_syncfs $fh, $callback->($status)
		1250
		1251	Asynchronously call the syncfs syscall to sync the filesystem associated
		1252	to the given filehandle and call the callback with the syncfs result
		1253	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1254	errno to C<ENOSYS> nevertheless.
		1255
		1256	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1257
		1258	Sync the data portion of the file specified by C<$offset> and C<$length>
		1259	to disk (but NOT the metadata), by calling the Linux-specific
		1260	sync_file_range call. If sync_file_range is not available or it returns
		1261	ENOSYS, then fdatasync or fsync is being substituted.
		1262
		1263	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1264	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1265	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1266	manpage for details.
		1267
860	=item aio_pathsync $path, $callback->($status)	1268	=item aio_pathsync $pathname, $callback->($status)
861		1269
862	This request tries to open, fsync and close the given path. This is a	1270	This request tries to open, fsync and close the given path. This is a
863	composite request intended to sync directories after directory operations	1271	composite request intended to sync directories after directory operations
864	(E.g. rename). This might not work on all operating systems or have any	1272	(E.g. rename). This might not work on all operating systems or have any
865	specific effect, but usually it makes sure that directory changes get	1273	specific effect, but usually it makes sure that directory changes get
866	written to disc. It works for anything that can be opened for read-only,	1274	written to disc. It works for anything that can be opened for read-only,
867	not just directories.	1275	not just directories.
		1276
		1277	Future versions of this function might fall back to other methods when
		1278	C<fsync> on the directory fails (such as calling C<sync>).
868		1279
869	Passes C<0> when everything went ok, and C<-1> on error.	1280	Passes C<0> when everything went ok, and C<-1> on error.
870		1281
871	=cut	1282	=cut
872		1283
…		…
893	};	1304	};
894		1305
895	$grp	1306	$grp
896	}	1307	}
897		1308
		1309	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1310
		1311	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1312	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1313	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1314	scalar must only be modified in-place while an aio operation is pending on
		1315	it).
		1316
		1317	It calls the C<msync> function of your OS, if available, with the memory
		1318	area starting at C<$offset> in the string and ending C<$length> bytes
		1319	later. If C<$length> is negative, counts from the end, and if C<$length>
		1320	is C<undef>, then it goes till the end of the string. The flags can be
		1321	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1322	C<IO::AIO::MS_SYNC>.
		1323
		1324	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1325
		1326	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1327	scalars.
		1328
		1329	It touches (reads or writes) all memory pages in the specified
		1330	range inside the scalar. All caveats and parameters are the same
		1331	as for C<aio_msync>, above, except for flags, which must be either
		1332	C<0> (which reads all pages and ensures they are instantiated) or
		1333	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1334	writing an octet from it, which dirties the page).
		1335
		1336	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1337
		1338	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1339	scalars.
		1340
		1341	It reads in all the pages of the underlying storage into memory (if any)
		1342	and locks them, so they are not getting swapped/paged out or removed.
		1343
		1344	If C<$length> is undefined, then the scalar will be locked till the end.
		1345
		1346	On systems that do not implement C<mlock>, this function returns C<-1>
		1347	and sets errno to C<ENOSYS>.
		1348
		1349	Note that the corresponding C<munlock> is synchronous and is
		1350	documented under L<MISCELLANEOUS FUNCTIONS>.
		1351
		1352	Example: open a file, mmap and mlock it - both will be undone when
		1353	C<$data> gets destroyed.
		1354
		1355	open my $fh, "<", $path or die "$path: $!";
		1356	my $data;
		1357	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1358	aio_mlock $data; # mlock in background
		1359
		1360	=item aio_mlockall $flags, $callback->($status)
		1361
		1362	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1363	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1364
		1365	On systems that do not implement C<mlockall>, this function returns C<-1>
		1366	and sets errno to C<ENOSYS>.
		1367
		1368	Note that the corresponding C<munlockall> is synchronous and is
		1369	documented under L<MISCELLANEOUS FUNCTIONS>.
		1370
		1371	Example: asynchronously lock all current and future pages into memory.
		1372
		1373	aio_mlockall IO::AIO::MCL_FUTURE;
		1374
		1375	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1376
		1377	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1378	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1379	the ioctl is not available on your OS, then this request will fail with
		1380	C<ENOSYS>.
		1381
		1382	C<$start> is the starting offset to query extents for, C<$length> is the
		1383	size of the range to query - if it is C<undef>, then the whole file will
		1384	be queried.
		1385
		1386	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1387	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1388	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1389	the data portion.
		1390
		1391	C<$count> is the maximum number of extent records to return. If it is
		1392	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1393	case, if it is C<0>, then the callback receives the number of extents
		1394	instead of the extents themselves (which is unreliable, see below).
		1395
		1396	If an error occurs, the callback receives no arguments. The special
		1397	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1398
		1399	Otherwise, the callback receives an array reference with extent
		1400	structures. Each extent structure is an array reference itself, with the
		1401	following members:
		1402
		1403	[$logical, $physical, $length, $flags]
		1404
		1405	Flags is any combination of the following flag values (typically either C<0>
		1406	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1407
		1408	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1409	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1410	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1411	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1412	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1413	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1414
		1415	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1416	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1417	it to return all extents of a range for files with large number of
		1418	extents. The code works around all these issues if C<$count> is undef.
		1419
898	=item aio_group $callback->(...)	1420	=item aio_group $callback->(...)
899		1421
900	This is a very special aio request: Instead of doing something, it is a	1422	This is a very special aio request: Instead of doing something, it is a
901	container for other aio requests, which is useful if you want to bundle	1423	container for other aio requests, which is useful if you want to bundle
902	many requests into a single, composite, request with a definite callback	1424	many requests into a single, composite, request with a definite callback
…		…
939	immense (it blocks a thread for a long time) so do not use this function	1461	immense (it blocks a thread for a long time) so do not use this function
940	except to put your application under artificial I/O pressure.	1462	except to put your application under artificial I/O pressure.
941		1463
942	=back	1464	=back
943		1465
		1466
		1467	=head2 IO::AIO::WD - multiple working directories
		1468
		1469	Your process only has one current working directory, which is used by all
		1470	threads. This makes it hard to use relative paths (some other component
		1471	could call C<chdir> at any time, and it is hard to control when the path
		1472	will be used by IO::AIO).
		1473
		1474	One solution for this is to always use absolute paths. This usually works,
		1475	but can be quite slow (the kernel has to walk the whole path on every
		1476	access), and can also be a hassle to implement.
		1477
		1478	Newer POSIX systems have a number of functions (openat, fdopendir,
		1479	futimensat and so on) that make it possible to specify working directories
		1480	per operation.
		1481
		1482	For portability, and because the clowns who "designed", or shall I write,
		1483	perpetrated this new interface were obviously half-drunk, this abstraction
		1484	cannot be perfect, though.
		1485
		1486	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1487	object. This object stores the canonicalised, absolute version of the
		1488	path, and on systems that allow it, also a directory file descriptor.
		1489
		1490	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1491	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1492	object and a pathname instead (or the IO::AIO::WD object alone, which
		1493	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1494	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1495	to that IO::AIO::WD object.
		1496
		1497	For example, to get a wd object for F</etc> and then stat F<passwd>
		1498	inside, you would write:
		1499
		1500	aio_wd "/etc", sub {
		1501	my $etcdir = shift;
		1502
		1503	# although $etcdir can be undef on error, there is generally no reason
		1504	# to check for errors here, as aio_stat will fail with ENOENT
		1505	# when $etcdir is undef.
		1506
		1507	aio_stat [$etcdir, "passwd"], sub {
		1508	# yay
		1509	};
		1510	};
		1511
		1512	The fact that C<aio_wd> is a request and not a normal function shows that
		1513	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1514	which is why it is done asynchronously.
		1515
		1516	To stat the directory obtained with C<aio_wd> above, one could write
		1517	either of the following three request calls:
		1518
		1519	aio_lstat "/etc" , sub { ... # pathname as normal string
		1520	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1521	aio_lstat $wd , sub { ... # shorthand for the previous
		1522
		1523	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1524	object and the pathname string, so you could write the following without
		1525	causing any issues due to C<$path> getting reused:
		1526
		1527	my $path = [$wd, undef];
		1528
		1529	for my $name (qw(abc def ghi)) {
		1530	$path->[1] = $name;
		1531	aio_stat $path, sub {
		1532	# ...
		1533	};
		1534	}
		1535
		1536	There are some caveats: when directories get renamed (or deleted), the
		1537	pathname string doesn't change, so will point to the new directory (or
		1538	nowhere at all), while the directory fd, if available on the system,
		1539	will still point to the original directory. Most functions accepting a
		1540	pathname will use the directory fd on newer systems, and the string on
		1541	older systems. Some functions (such as realpath) will always rely on the
		1542	string form of the pathname.
		1543
		1544	So this functionality is mainly useful to get some protection against
		1545	C<chdir>, to easily get an absolute path out of a relative path for future
		1546	reference, and to speed up doing many operations in the same directory
		1547	(e.g. when stat'ing all files in a directory).
		1548
		1549	The following functions implement this working directory abstraction:
		1550
		1551	=over 4
		1552
		1553	=item aio_wd $pathname, $callback->($wd)
		1554
		1555	Asynchonously canonicalise the given pathname and convert it to an
		1556	IO::AIO::WD object representing it. If possible and supported on the
		1557	system, also open a directory fd to speed up pathname resolution relative
		1558	to this working directory.
		1559
		1560	If something goes wrong, then C<undef> is passwd to the callback instead
		1561	of a working directory object and C<$!> is set appropriately. Since
		1562	passing C<undef> as working directory component of a pathname fails the
		1563	request with C<ENOENT>, there is often no need for error checking in the
		1564	C<aio_wd> callback, as future requests using the value will fail in the
		1565	expected way.
		1566
		1567	=item IO::AIO::CWD
		1568
		1569	This is a compiletime constant (object) that represents the process
		1570	current working directory.
		1571
		1572	Specifying this object as working directory object for a pathname is as if
		1573	the pathname would be specified directly, without a directory object. For
		1574	example, these calls are functionally identical:
		1575
		1576	aio_stat "somefile", sub { ... };
		1577	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1578
		1579	=back
		1580
		1581	To recover the path associated with an IO::AIO::WD object, you can use
		1582	C<aio_realpath>:
		1583
		1584	aio_realpath $wd, sub {
		1585	warn "path is $_[0]\n";
		1586	};
		1587
		1588	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1589	sometimes, fall back to using an absolue path.
		1590
944	=head2 IO::AIO::REQ CLASS	1591	=head2 IO::AIO::REQ CLASS
945		1592
946	All non-aggregate C<aio_*> functions return an object of this class when	1593	All non-aggregate C<aio_*> functions return an object of this class when
947	called in non-void context.	1594	called in non-void context.
948		1595
…		…
951	=item cancel $req	1598	=item cancel $req
952		1599
953	Cancels the request, if possible. Has the effect of skipping execution	1600	Cancels the request, if possible. Has the effect of skipping execution
954	when entering the B<execute> state and skipping calling the callback when	1601	when entering the B<execute> state and skipping calling the callback when
955	entering the the B<result> state, but will leave the request otherwise	1602	entering the the B<result> state, but will leave the request otherwise
956	untouched. That means that requests that currently execute will not be	1603	untouched (with the exception of readdir). That means that requests that
957	stopped and resources held by the request will not be freed prematurely.	1604	currently execute will not be stopped and resources held by the request
		1605	will not be freed prematurely.
958		1606
959	=item cb $req $callback->(...)	1607	=item cb $req $callback->(...)
960		1608
961	Replace (or simply set) the callback registered to the request.	1609	Replace (or simply set) the callback registered to the request.
962		1610
…		…
1036	=item $grp->cancel_subs	1684	=item $grp->cancel_subs
1037		1685
1038	Cancel all subrequests and clears any feeder, but not the group request	1686	Cancel all subrequests and clears any feeder, but not the group request
1039	itself. Useful when you queued a lot of events but got a result early.	1687	itself. Useful when you queued a lot of events but got a result early.
1040		1688
		1689	The group request will finish normally (you cannot add requests to the
		1690	group).
		1691
1041	=item $grp->result (...)	1692	=item $grp->result (...)
1042		1693
1043	Set the result value(s) that will be passed to the group callback when all	1694	Set the result value(s) that will be passed to the group callback when all
1044	subrequests have finished and set the groups errno to the current value	1695	subrequests have finished and set the groups errno to the current value
1045	of errno (just like calling C<errno> without an error number). By default,	1696	of errno (just like calling C<errno> without an error number). By default,
…		…
1060	=item feed $grp $callback->($grp)	1711	=item feed $grp $callback->($grp)
1061		1712
1062	Sets a feeder/generator on this group: every group can have an attached	1713	Sets a feeder/generator on this group: every group can have an attached
1063	generator that generates requests if idle. The idea behind this is that,	1714	generator that generates requests if idle. The idea behind this is that,
1064	although you could just queue as many requests as you want in a group,	1715	although you could just queue as many requests as you want in a group,
1065	this might starve other requests for a potentially long time. For	1716	this might starve other requests for a potentially long time. For example,
1066	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1717	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1067	requests, delaying any later requests for a long time.	1718	requests, delaying any later requests for a long time.
1068		1719
1069	To avoid this, and allow incremental generation of requests, you can	1720	To avoid this, and allow incremental generation of requests, you can
1070	instead a group and set a feeder on it that generates those requests. The	1721	instead a group and set a feeder on it that generates those requests. The
1071	feed callback will be called whenever there are few enough (see C<limit>,	1722	feed callback will be called whenever there are few enough (see C<limit>,
…		…
1076	not impose any limits).	1727	not impose any limits).
1077		1728
1078	If the feed does not queue more requests when called, it will be	1729	If the feed does not queue more requests when called, it will be
1079	automatically removed from the group.	1730	automatically removed from the group.
1080		1731
1081	If the feed limit is C<0>, it will be set to C<2> automatically.	1732	If the feed limit is C<0> when this method is called, it will be set to
		1733	C<2> automatically.
1082		1734
1083	Example:	1735	Example:
1084		1736
1085	# stat all files in @files, but only ever use four aio requests concurrently:	1737	# stat all files in @files, but only ever use four aio requests concurrently:
1086		1738
…		…
1098	Sets the feeder limit for the group: The feeder will be called whenever	1750	Sets the feeder limit for the group: The feeder will be called whenever
1099	the group contains less than this many requests.	1751	the group contains less than this many requests.
1100		1752
1101	Setting the limit to C<0> will pause the feeding process.	1753	Setting the limit to C<0> will pause the feeding process.
1102		1754
		1755	The default value for the limit is C<0>, but note that setting a feeder
		1756	automatically bumps it up to C<2>.
		1757
1103	=back	1758	=back
1104		1759
1105	=head2 SUPPORT FUNCTIONS	1760	=head2 SUPPORT FUNCTIONS
1106		1761
1107	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1762	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
1109	=over 4	1764	=over 4
1110		1765
1111	=item $fileno = IO::AIO::poll_fileno	1766	=item $fileno = IO::AIO::poll_fileno
1112		1767
1113	Return the I<request result pipe file descriptor>. This filehandle must be	1768	Return the I<request result pipe file descriptor>. This filehandle must be
1114	polled for reading by some mechanism outside this module (e.g. Event or	1769	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1115	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1770	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1116	to call C<poll_cb> to check the results.	1771	you have to call C<poll_cb> to check the results.
1117		1772
1118	See C<poll_cb> for an example.	1773	See C<poll_cb> for an example.
1119		1774
1120	=item IO::AIO::poll_cb	1775	=item IO::AIO::poll_cb
1121		1776
1122	Process some outstanding events on the result pipe. You have to call this	1777	Process some requests that have reached the result phase (i.e. they have
1123	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1778	been executed but the results are not yet reported). You have to call
1124	returned earlier for whatever reason. Returns immediately when no events	1779	this "regularly" to finish outstanding requests.
1125	are outstanding. The amount of events processed depends on the settings of
1126	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1127		1780
		1781	Returns C<0> if all events could be processed (or there were no
		1782	events to process), or C<-1> if it returned earlier for whatever
		1783	reason. Returns immediately when no events are outstanding. The amount
		1784	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1785	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1786
1128	If not all requests were processed for whatever reason, the filehandle	1787	If not all requests were processed for whatever reason, the poll file
1129	will still be ready when C<poll_cb> returns, so normally you don't have to	1788	descriptor will still be ready when C<poll_cb> returns, so normally you
1130	do anything special to have it called later.	1789	don't have to do anything special to have it called later.
		1790
		1791	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1792	ready, it can be beneficial to call this function from loops which submit
		1793	a lot of requests, to make sure the results get processed when they become
		1794	available and not just when the loop is finished and the event loop takes
		1795	over again. This function returns very fast when there are no outstanding
		1796	requests.
1131		1797
1132	Example: Install an Event watcher that automatically calls	1798	Example: Install an Event watcher that automatically calls
1133	IO::AIO::poll_cb with high priority:	1799	IO::AIO::poll_cb with high priority (more examples can be found in the
		1800	SYNOPSIS section, at the top of this document):
1134		1801
1135	Event->io (fd => IO::AIO::poll_fileno,	1802	Event->io (fd => IO::AIO::poll_fileno,
1136	poll => 'r', async => 1,	1803	poll => 'r', async => 1,
1137	cb => \&IO::AIO::poll_cb);	1804	cb => \&IO::AIO::poll_cb);
		1805
		1806	=item IO::AIO::poll_wait
		1807
		1808	Wait until either at least one request is in the result phase or no
		1809	requests are outstanding anymore.
		1810
		1811	This is useful if you want to synchronously wait for some requests to
		1812	become ready, without actually handling them.
		1813
		1814	See C<nreqs> for an example.
		1815
		1816	=item IO::AIO::poll
		1817
		1818	Waits until some requests have been handled.
		1819
		1820	Returns the number of requests processed, but is otherwise strictly
		1821	equivalent to:
		1822
		1823	IO::AIO::poll_wait, IO::AIO::poll_cb
		1824
		1825	=item IO::AIO::flush
		1826
		1827	Wait till all outstanding AIO requests have been handled.
		1828
		1829	Strictly equivalent to:
		1830
		1831	IO::AIO::poll_wait, IO::AIO::poll_cb
		1832	while IO::AIO::nreqs;
1138		1833
1139	=item IO::AIO::max_poll_reqs $nreqs	1834	=item IO::AIO::max_poll_reqs $nreqs
1140		1835
1141	=item IO::AIO::max_poll_time $seconds	1836	=item IO::AIO::max_poll_time $seconds
1142		1837
…		…
1167	# use a low priority so other tasks have priority	1862	# use a low priority so other tasks have priority
1168	Event->io (fd => IO::AIO::poll_fileno,	1863	Event->io (fd => IO::AIO::poll_fileno,
1169	poll => 'r', nice => 1,	1864	poll => 'r', nice => 1,
1170	cb => &IO::AIO::poll_cb);	1865	cb => &IO::AIO::poll_cb);
1171		1866
1172	=item IO::AIO::poll_wait
1173
1174	If there are any outstanding requests and none of them in the result
1175	phase, wait till the result filehandle becomes ready for reading (simply
1176	does a C<select> on the filehandle. This is useful if you want to
1177	synchronously wait for some requests to finish).
1178
1179	See C<nreqs> for an example.
1180
1181	=item IO::AIO::poll
1182
1183	Waits until some requests have been handled.
1184
1185	Returns the number of requests processed, but is otherwise strictly
1186	equivalent to:
1187
1188	IO::AIO::poll_wait, IO::AIO::poll_cb
1189
1190	=item IO::AIO::flush
1191
1192	Wait till all outstanding AIO requests have been handled.
1193
1194	Strictly equivalent to:
1195
1196	IO::AIO::poll_wait, IO::AIO::poll_cb
1197	while IO::AIO::nreqs;
1198
1199	=back	1867	=back
1200		1868
1201	=head3 CONTROLLING THE NUMBER OF THREADS	1869	=head3 CONTROLLING THE NUMBER OF THREADS
1202		1870
1203	=over	1871	=over
…		…
1236		1904
1237	Under normal circumstances you don't need to call this function.	1905	Under normal circumstances you don't need to call this function.
1238		1906
1239	=item IO::AIO::max_idle $nthreads	1907	=item IO::AIO::max_idle $nthreads
1240		1908
1241	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1909	Limit the number of threads (default: 4) that are allowed to idle
1242	threads that did not get a request to process within 10 seconds). That	1910	(i.e., threads that did not get a request to process within the idle
1243	means if a thread becomes idle while C<$nthreads> other threads are also	1911	timeout (default: 10 seconds). That means if a thread becomes idle while
1244	idle, it will free its resources and exit.	1912	C<$nthreads> other threads are also idle, it will free its resources and
		1913	exit.
1245		1914
1246	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1915	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1247	to allow for extremely high load situations, but want to free resources	1916	to allow for extremely high load situations, but want to free resources
1248	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1917	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1249		1918
1250	The default is probably ok in most situations, especially if thread	1919	The default is probably ok in most situations, especially if thread
1251	creation is fast. If thread creation is very slow on your system you might	1920	creation is fast. If thread creation is very slow on your system you might
1252	want to use larger values.	1921	want to use larger values.
1253		1922
		1923	=item IO::AIO::idle_timeout $seconds
		1924
		1925	Sets the minimum idle timeout (default 10) after which worker threads are
		1926	allowed to exit. SEe C<IO::AIO::max_idle>.
		1927
1254	=item IO::AIO::max_outstanding $maxreqs	1928	=item IO::AIO::max_outstanding $maxreqs
		1929
		1930	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1931	you do queue up more than this number of requests, the next call to
		1932	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1933	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1934	longer exceeded.
		1935
		1936	In other words, this setting does not enforce a queue limit, but can be
		1937	used to make poll functions block if the limit is exceeded.
1255		1938
1256	This is a very bad function to use in interactive programs because it	1939	This is a very bad function to use in interactive programs because it
1257	blocks, and a bad way to reduce concurrency because it is inexact: Better	1940	blocks, and a bad way to reduce concurrency because it is inexact: Better
1258	use an C<aio_group> together with a feed callback.	1941	use an C<aio_group> together with a feed callback.
1259		1942
1260	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1943	Its main use is in scripts without an event loop - when you want to stat
1261	do queue up more than this number of requests, the next call to the	1944	a lot of files, you can write somehting like this:
1262	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1263	function will block until the limit is no longer exceeded.
1264		1945
1265	The default value is very large, so there is no practical limit on the	1946	IO::AIO::max_outstanding 32;
1266	number of outstanding requests.
1267		1947
1268	You can still queue as many requests as you want. Therefore,	1948	for my $path (...) {
1269	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1949	aio_stat $path , ...;
1270	as a stop gap to shield against fatal memory overflow (with large values).	1950	IO::AIO::poll_cb;
		1951	}
		1952
		1953	IO::AIO::flush;
		1954
		1955	The call to C<poll_cb> inside the loop will normally return instantly, but
		1956	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1957	some requests have been handled. This keeps the loop from pushing a large
		1958	number of C<aio_stat> requests onto the queue.
		1959
		1960	The default value for C<max_outstanding> is very large, so there is no
		1961	practical limit on the number of outstanding requests.
1271		1962
1272	=back	1963	=back
1273		1964
1274	=head3 STATISTICAL INFORMATION	1965	=head3 STATISTICAL INFORMATION
1275		1966
…		…
1295	Returns the number of requests currently in the pending state (executed,	1986	Returns the number of requests currently in the pending state (executed,
1296	but not yet processed by poll_cb).	1987	but not yet processed by poll_cb).
1297		1988
1298	=back	1989	=back
1299		1990
		1991	=head3 MISCELLANEOUS FUNCTIONS
		1992
		1993	IO::AIO implements some functions that are useful when you want to use
		1994	some "Advanced I/O" function not available to in Perl, without going the
		1995	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		1996	counterpart.
		1997
		1998	=over 4
		1999
		2000	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2001
		2002	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2003	but is blocking (this makes most sense if you know the input data is
		2004	likely cached already and the output filehandle is set to non-blocking
		2005	operations).
		2006
		2007	Returns the number of bytes copied, or C<-1> on error.
		2008
		2009	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2010
		2011	Simply calls the C<posix_fadvise> function (see its
		2012	manpage for details). The following advice constants are
		2013	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2014	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2015	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2016
		2017	On systems that do not implement C<posix_fadvise>, this function returns
		2018	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2019
		2020	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2021
		2022	Simply calls the C<posix_madvise> function (see its
		2023	manpage for details). The following advice constants are
		2024	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2025	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		2026
		2027	On systems that do not implement C<posix_madvise>, this function returns
		2028	ENOSYS, otherwise the return value of C<posix_madvise>.
		2029
		2030	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2031
		2032	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2033	$scalar (see its manpage for details). The following protect
		2034	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2035	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2036
		2037	On systems that do not implement C<mprotect>, this function returns
		2038	ENOSYS, otherwise the return value of C<mprotect>.
		2039
		2040	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2041
		2042	Memory-maps a file (or anonymous memory range) and attaches it to the
		2043	given C<$scalar>, which will act like a string scalar. Returns true on
		2044	success, and false otherwise.
		2045
		2046	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		2047	change the string length, and most read-only operations such as copying it
		2048	or searching it with regexes and so on.
		2049
		2050	Anything else is unsafe and will, at best, result in memory leaks.
		2051
		2052	The memory map associated with the C<$scalar> is automatically removed
		2053	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		2054	C<IO::AIO::munmap> functions are called.
		2055
		2056	This calls the C<mmap>(2) function internally. See your system's manual
		2057	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2058
		2059	The C<$length> must be larger than zero and smaller than the actual
		2060	filesize.
		2061
		2062	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2063	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2064
		2065	C<$flags> can be a combination of
		2066	C<IO::AIO::MAP_SHARED> or
		2067	C<IO::AIO::MAP_PRIVATE>,
		2068	or a number of system-specific flags (when not available, the are C<0>):
		2069	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2070	C<IO::AIO::MAP_HUGETLB>,
		2071	C<IO::AIO::MAP_LOCKED>,
		2072	C<IO::AIO::MAP_NORESERVE>,
		2073	C<IO::AIO::MAP_POPULATE>,
		2074	C<IO::AIO::MAP_NONBLOCK>,
		2075	C<IO::AIO::MAP_FIXED>,
		2076	C<IO::AIO::MAP_GROWSDOWN>,
		2077	C<IO::AIO::MAP_32BIT>,
		2078	C<IO::AIO::MAP_HUGETLB> or
		2079	C<IO::AIO::MAP_STACK>.
		2080
		2081	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2082
		2083	C<$offset> is the offset from the start of the file - it generally must be
		2084	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2085
		2086	Example:
		2087
		2088	use Digest::MD5;
		2089	use IO::AIO;
		2090
		2091	open my $fh, "<verybigfile"
		2092	or die "$!";
		2093
		2094	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2095	or die "verybigfile: $!";
		2096
		2097	my $fast_md5 = md5 $data;
		2098
		2099	=item IO::AIO::munmap $scalar
		2100
		2101	Removes a previous mmap and undefines the C<$scalar>.
		2102
		2103	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2104
		2105	Calls the C<munlock> function, undoing the effects of a previous
		2106	C<aio_mlock> call (see its description for details).
		2107
		2108	=item IO::AIO::munlockall
		2109
		2110	Calls the C<munlockall> function.
		2111
		2112	On systems that do not implement C<munlockall>, this function returns
		2113	ENOSYS, otherwise the return value of C<munlockall>.
		2114
		2115	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2116
		2117	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2118	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2119	should be the file offset.
		2120
		2121	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2122	silently corrupt the data in this case.
		2123
		2124	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2125	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2126	C<IO::AIO::SPLICE_F_GIFT>.
		2127
		2128	See the C<splice(2)> manpage for details.
		2129
		2130	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2131
		2132	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2133	description for C<IO::AIO::splice> above for details.
		2134
		2135	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2136
		2137	Attempts to query or change the pipe buffer size. Obviously works only
		2138	on pipes, and currently works only on GNU/Linux systems, and fails with
		2139	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2140	size on other systems, drop me a note.
		2141
		2142	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2143
		2144	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2145	C<$flags> is missing or C<0>, then this should be the same as a call to
		2146	perl's built-in C<pipe> function and create a new pipe, and works on
		2147	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2148	(..., 4096, O_BINARY)>.
		2149
		2150	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2151	the given flags (Linux 2.6.27, glibc 2.9).
		2152
		2153	On success, the read and write file handles are returned.
		2154
		2155	On error, nothing will be returned. If the pipe2 syscall is missing and
		2156	C<$flags> is non-zero, fails with C<ENOSYS>.
		2157
		2158	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2159	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2160	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2161
		2162	=back
		2163
1300	=cut	2164	=cut
1301		2165
1302	min_parallel 8;	2166	min_parallel 8;
1303		2167
1304	END { flush }	2168	END { flush }
1305		2169
1306	1;	2170	1;
1307		2171
		2172	=head1 EVENT LOOP INTEGRATION
		2173
		2174	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2175	automatically into many event loops:
		2176
		2177	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2178	use AnyEvent::AIO;
		2179
		2180	You can also integrate IO::AIO manually into many event loops, here are
		2181	some examples of how to do this:
		2182
		2183	# EV integration
		2184	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2185
		2186	# Event integration
		2187	Event->io (fd => IO::AIO::poll_fileno,
		2188	poll => 'r',
		2189	cb => \&IO::AIO::poll_cb);
		2190
		2191	# Glib/Gtk2 integration
		2192	add_watch Glib::IO IO::AIO::poll_fileno,
		2193	in => sub { IO::AIO::poll_cb; 1 };
		2194
		2195	# Tk integration
		2196	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2197	readable => \&IO::AIO::poll_cb);
		2198
		2199	# Danga::Socket integration
		2200	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2201	\&IO::AIO::poll_cb);
		2202
1308	=head2 FORK BEHAVIOUR	2203	=head2 FORK BEHAVIOUR
1309		2204
1310	This module should do "the right thing" when the process using it forks:	2205	Usage of pthreads in a program changes the semantics of fork
		2206	considerably. Specifically, only async-safe functions can be called after
		2207	fork. Perl doesn't know about this, so in general, you cannot call fork
		2208	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2209	pthreads, so this applies, but many other extensions and (for inexplicable
		2210	reasons) perl itself often is linked against pthreads, so this limitation
		2211	applies to quite a lot of perls.
1311		2212
1312	Before the fork, IO::AIO enters a quiescent state where no requests	2213	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1313	can be added in other threads and no results will be processed. After	2214	only works in the process that loaded it. Forking is fully supported, but
1314	the fork the parent simply leaves the quiescent state and continues	2215	using IO::AIO in the child is not.
1315	request/result processing, while the child frees the request/result queue
1316	(so that the requests started before the fork will only be handled in the
1317	parent). Threads will be started on demand until the limit set in the
1318	parent process has been reached again.
1319		2216
1320	In short: the parent will, after a short pause, continue as if fork had	2217	You might get around by not I<using> IO::AIO before (or after)
1321	not been called, while the child will act as if IO::AIO has not been used	2218	forking. You could also try to call the L<IO::AIO::reinit> function in the
1322	yet.	2219	child:
		2220
		2221	=over 4
		2222
		2223	=item IO::AIO::reinit
		2224
		2225	Abandons all current requests and I/O threads and simply reinitialises all
		2226	data structures. This is not an operation supported by any standards, but
		2227	happens to work on GNU/Linux and some newer BSD systems.
		2228
		2229	The only reasonable use for this function is to call it after forking, if
		2230	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2231	the process will result in undefined behaviour. Calling it at any time
		2232	will also result in any undefined (by POSIX) behaviour.
		2233
		2234	=back
1323		2235
1324	=head2 MEMORY USAGE	2236	=head2 MEMORY USAGE
1325		2237
1326	Per-request usage:	2238	Per-request usage:
1327		2239

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