[ViewVC] Diff of: cvs/IO-AIO/README

Comparing IO-AIO/README (file contents):
Revision 1.22 by root, Sat Jan 6 02:47:11 2007 UTC vs.
Revision 1.50 by root, Sun Oct 9 08:24:49 2011 UTC

…		…
2	IO::AIO - Asynchronous Input/Output	2	IO::AIO - Asynchronous Input/Output
3		3
4	SYNOPSIS	4	SYNOPSIS
5	use IO::AIO;	5	use IO::AIO;
6		6
7	aio_open "/etc/passwd", O_RDONLY, 0, sub {	7	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8	my $fh = shift	8	my $fh = shift
9	or die "/etc/passwd: $!";	9	or die "/etc/passwd: $!";
10	...	10	...
11	};	11	};
12		12
…		…
24	$req->cancel; # cancel request if still in queue	24	$req->cancel; # cancel request if still in queue
25		25
26	my $grp = aio_group sub { print "all stats done\n" };	26	my $grp = aio_group sub { print "all stats done\n" };
27	add $grp aio_stat "..." for ...;	27	add $grp aio_stat "..." for ...;
28		28
29	# AnyEvent integration
30	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
31	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
32
33	# Event integration
34	Event->io (fd => IO::AIO::poll_fileno,
35	poll => 'r',
36	cb => \&IO::AIO::poll_cb);
37
38	# Glib/Gtk2 integration
39	add_watch Glib::IO IO::AIO::poll_fileno,
40	in => sub { IO::AIO::poll_cb; 1 };
41
42	# Tk integration
43	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
44	readable => \&IO::AIO::poll_cb);
45
46	# Danga::Socket integration
47	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
48	\&IO::AIO::poll_cb);
49
50	DESCRIPTION	29	DESCRIPTION
51	This module implements asynchronous I/O using whatever means your	30	This module implements asynchronous I/O using whatever means your
52	operating system supports.	31	operating system supports. It is implemented as an interface to "libeio"
		32	(<http://software.schmorp.de/pkg/libeio.html>).
53		33
54	Asynchronous means that operations that can normally block your program	34	Asynchronous means that operations that can normally block your program
55	(e.g. reading from disk) will be done asynchronously: the operation will	35	(e.g. reading from disk) will be done asynchronously: the operation will
56	still block, but you can do something else in the meantime. This is	36	still block, but you can do something else in the meantime. This is
57	extremely useful for programs that need to stay interactive even when	37	extremely useful for programs that need to stay interactive even when
…		…
61	faster on a RAID volume or over NFS when you do a number of stat	41	faster on a RAID volume or over NFS when you do a number of stat
62	operations concurrently.	42	operations concurrently.
63		43
64	While most of this works on all types of file descriptors (for example	44	While most of this works on all types of file descriptors (for example
65	sockets), using these functions on file descriptors that support	45	sockets), using these functions on file descriptors that support
66	nonblocking operation (again, sockets, pipes etc.) is very inefficient	46	nonblocking operation (again, sockets, pipes etc.) is very inefficient.
67	or might not work (aio_read fails on sockets/pipes/fifos). Use an event
68	loop for that (such as the Event module): IO::AIO will naturally fit	47	Use an event loop for that (such as the EV module): IO::AIO will
69	into such an event loop itself.	48	naturally fit into such an event loop itself.
70		49
71	In this version, a number of threads are started that execute your	50	In this version, a number of threads are started that execute your
72	requests and signal their completion. You don't need thread support in	51	requests and signal their completion. You don't need thread support in
73	perl, and the threads created by this module will not be visible to	52	perl, and the threads created by this module will not be visible to
74	perl. In the future, this module might make use of the native aio	53	perl. In the future, this module might make use of the native aio
…		…
76	not well-supported or restricted (GNU/Linux doesn't allow them on normal	55	not well-supported or restricted (GNU/Linux doesn't allow them on normal
77	files currently, for example), and they would only support aio_read and	56	files currently, for example), and they would only support aio_read and
78	aio_write, so the remaining functionality would have to be implemented	57	aio_write, so the remaining functionality would have to be implemented
79	using threads anyway.	58	using threads anyway.
80		59
81	Although the module will work with in the presence of other (Perl-)	60	Although the module will work in the presence of other (Perl-) threads,
82	threads, it is currently not reentrant in any way, so use appropriate	61	it is currently not reentrant in any way, so use appropriate locking
83	locking yourself, always call "poll_cb" from within the same thread, or	62	yourself, always call "poll_cb" from within the same thread, or never
84	never call "poll_cb" (or other "aio_" functions) recursively.	63	call "poll_cb" (or other "aio_" functions) recursively.
85		64
86	EXAMPLE	65	EXAMPLE
87	This is a simple example that uses the Event module and loads	66	This is a simple example that uses the EV module and loads /etc/passwd
88	/etc/passwd asynchronously:	67	asynchronously:
89		68
90	use Fcntl;	69	use Fcntl;
91	use Event;	70	use EV;
92	use IO::AIO;	71	use IO::AIO;
93		72
94	# register the IO::AIO callback with Event	73	# register the IO::AIO callback with EV
95	Event->io (fd => IO::AIO::poll_fileno,	74	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
96	poll => 'r',
97	cb => \&IO::AIO::poll_cb);
98		75
99	# queue the request to open /etc/passwd	76	# queue the request to open /etc/passwd
100	aio_open "/etc/passwd", O_RDONLY, 0, sub {	77	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
101	my $fh = shift	78	my $fh = shift
102	or die "error while opening: $!";	79	or die "error while opening: $!";
103		80
104	# stat'ing filehandles is generally non-blocking	81	# stat'ing filehandles is generally non-blocking
105	my $size = -s $fh;	82	my $size = -s $fh;
…		…
114		91
115	# file contents now in $contents	92	# file contents now in $contents
116	print $contents;	93	print $contents;
117		94
118	# exit event loop and program	95	# exit event loop and program
119	Event::unloop;	96	EV::unloop;
120	};	97	};
121	};	98	};
122		99
123	# possibly queue up other requests, or open GUI windows,	100	# possibly queue up other requests, or open GUI windows,
124	# check for sockets etc. etc.	101	# check for sockets etc. etc.
125		102
126	# process events as long as there are some:	103	# process events as long as there are some:
127	Event::loop;	104	EV::loop;
128		105
129	REQUEST ANATOMY AND LIFETIME	106	REQUEST ANATOMY AND LIFETIME
130	Every "aio_*" function creates a request. which is a C data structure	107	Every "aio_*" function creates a request. which is a C data structure
131	not directly visible to Perl.	108	not directly visible to Perl.
132		109
…		…
168	anymore (except possibly for the Perl object, but its connection to	145	anymore (except possibly for the Perl object, but its connection to
169	the actual aio request is severed and calling its methods will	146	the actual aio request is severed and calling its methods will
170	either do nothing or result in a runtime error).	147	either do nothing or result in a runtime error).
171		148
172	FUNCTIONS	149	FUNCTIONS
		150	QUICK OVERVIEW
		151	This section simply lists the prototypes of the most important functions
		152	for quick reference. See the following sections for function-by-function
		153	documentation.
		154
		155	aio_wd $pathname, $callback->($wd)
		156	aio_open $pathname, $flags, $mode, $callback->($fh)
		157	aio_close $fh, $callback->($status)
		158	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		159	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		160	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		161	aio_readahead $fh,$offset,$length, $callback->($retval)
		162	aio_stat $fh_or_path, $callback->($status)
		163	aio_lstat $fh, $callback->($status)
		164	aio_statvfs $fh_or_path, $callback->($statvfs)
		165	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		166	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		167	aio_truncate $fh_or_path, $offset, $callback->($status)
		168	aio_chmod $fh_or_path, $mode, $callback->($status)
		169	aio_unlink $pathname, $callback->($status)
		170	aio_mknod $pathname, $mode, $dev, $callback->($status)
		171	aio_link $srcpath, $dstpath, $callback->($status)
		172	aio_symlink $srcpath, $dstpath, $callback->($status)
		173	aio_readlink $pathname, $callback->($link)
		174	aio_realpath $pathname, $callback->($link)
		175	aio_rename $srcpath, $dstpath, $callback->($status)
		176	aio_mkdir $pathname, $mode, $callback->($status)
		177	aio_rmdir $pathname, $callback->($status)
		178	aio_readdir $pathname, $callback->($entries)
		179	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		180	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		181	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		182	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		183	aio_load $pathname, $data, $callback->($status)
		184	aio_copy $srcpath, $dstpath, $callback->($status)
		185	aio_move $srcpath, $dstpath, $callback->($status)
		186	aio_rmtree $pathname, $callback->($status)
		187	aio_sync $callback->($status)
		188	aio_syncfs $fh, $callback->($status)
		189	aio_fsync $fh, $callback->($status)
		190	aio_fdatasync $fh, $callback->($status)
		191	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		192	aio_pathsync $pathname, $callback->($status)
		193	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		194	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		195	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		196	aio_mlockall $flags, $callback->($status)
		197	aio_group $callback->(...)
		198	aio_nop $callback->()
		199
		200	$prev_pri = aioreq_pri [$pri]
		201	aioreq_nice $pri_adjust
		202
		203	IO::AIO::poll_wait
		204	IO::AIO::poll_cb
		205	IO::AIO::poll
		206	IO::AIO::flush
		207	IO::AIO::max_poll_reqs $nreqs
		208	IO::AIO::max_poll_time $seconds
		209	IO::AIO::min_parallel $nthreads
		210	IO::AIO::max_parallel $nthreads
		211	IO::AIO::max_idle $nthreads
		212	IO::AIO::idle_timeout $seconds
		213	IO::AIO::max_outstanding $maxreqs
		214	IO::AIO::nreqs
		215	IO::AIO::nready
		216	IO::AIO::npending
		217
		218	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		219	IO::AIO::fadvise $fh, $offset, $len, $advice
		220	IO::AIO::madvise $scalar, $offset, $length, $advice
		221	IO::AIO::mprotect $scalar, $offset, $length, $protect
		222	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		223	IO::AIO::munlockall
		224
173	AIO REQUEST FUNCTIONS	225	AIO REQUEST FUNCTIONS
174	All the "aio_*" calls are more or less thin wrappers around the syscall	226	All the "aio_*" calls are more or less thin wrappers around the syscall
175	with the same name (sans "aio_"). The arguments are similar or	227	with the same name (sans "aio_"). The arguments are similar or
176	identical, and they all accept an additional (and optional) $callback	228	identical, and they all accept an additional (and optional) $callback
177	argument which must be a code reference. This code reference will get	229	argument which must be a code reference. This code reference will be
178	called with the syscall return code (e.g. most syscalls return -1 on	230	called after the syscall has been executed in an asynchronous fashion.
179	error, unlike perl, which usually delivers "false") as it's sole	231	The results of the request will be passed as arguments to the callback
180	argument when the given syscall has been executed asynchronously.	232	(and, if an error occured, in $!) - for most requests the syscall return
		233	code (e.g. most syscalls return -1 on error, unlike perl, which usually
		234	delivers "false").
		235
		236	Some requests (such as "aio_readdir") pass the actual results and
		237	communicate failures by passing "undef".
181		238
182	All functions expecting a filehandle keep a copy of the filehandle	239	All functions expecting a filehandle keep a copy of the filehandle
183	internally until the request has finished.	240	internally until the request has finished.
184		241
185	All functions return request objects of type IO::AIO::REQ that allow	242	All functions return request objects of type IO::AIO::REQ that allow
186	further manipulation of those requests while they are in-flight.	243	further manipulation of those requests while they are in-flight.
187		244
188	The pathnames you pass to these routines must be absolute and encoded	245	The pathnames you pass to these routines should be absolute. The
189	as octets. The reason for the former is that at the time the request is	246	reason for this is that at the time the request is being executed, the
190	being executed, the current working directory could have changed.	247	current working directory could have changed. Alternatively, you can
191	Alternatively, you can make sure that you never change the current	248	make sure that you never change the current working directory anywhere
192	working directory anywhere in the program and then use relative paths.	249	in the program and then use relative paths. You can also take advantage
		250	of IO::AIOs working directory abstraction, that lets you specify paths
		251	relative to some previously-opened "working directory object" - see the
		252	description of the "IO::AIO::WD" class later in this document.
193		253
194	To encode pathnames as octets, either make sure you either: a) always	254	To encode pathnames as octets, either make sure you either: a) always
195	pass in filenames you got from outside (command line, readdir etc.)	255	pass in filenames you got from outside (command line, readdir etc.)
196	without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module	256	without tinkering, b) are in your native filesystem encoding, c) use the
197	and encode your pathnames to the locale (or other) encoding in effect in	257	Encode module and encode your pathnames to the locale (or other)
198	the user environment, d) use Glib::filename_from_unicode on unicode	258	encoding in effect in the user environment, d) use
199	filenames or e) use something else to ensure your scalar has the correct	259	Glib::filename_from_unicode on unicode filenames or e) use something
200	contents.	260	else to ensure your scalar has the correct contents.
201		261
202	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	262	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203	handles correctly wether it is set or not.	263	handles correctly whether it is set or not.
204		264
205	$prev_pri = aioreq_pri [$pri]	265	$prev_pri = aioreq_pri [$pri]
206	Returns the priority value that would be used for the next request	266	Returns the priority value that would be used for the next request
207	and, if $pri is given, sets the priority for the next aio request.	267	and, if $pri is given, sets the priority for the next aio request.
208		268
…		…
242	They are the same as used by "sysopen".	302	They are the same as used by "sysopen".
243		303
244	Likewise, $mode specifies the mode of the newly created file, if it	304	Likewise, $mode specifies the mode of the newly created file, if it
245	didn't exist and "O_CREAT" has been given, just like perl's	305	didn't exist and "O_CREAT" has been given, just like perl's
246	"sysopen", except that it is mandatory (i.e. use 0 if you don't	306	"sysopen", except that it is mandatory (i.e. use 0 if you don't
247	create new files, and 0666 or 0777 if you do).	307	create new files, and 0666 or 0777 if you do). Note that the $mode
		308	will be modified by the umask in effect then the request is being
		309	executed, so better never change the umask.
248		310
249	Example:	311	Example:
250		312
251	aio_open "/etc/passwd", O_RDONLY, 0, sub {	313	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
252	if ($_[0]) {	314	if ($_[0]) {
253	print "open successful, fh is $_[0]\n";	315	print "open successful, fh is $_[0]\n";
254	...	316	...
255	} else {	317	} else {
256	die "open failed: $!\n";	318	die "open failed: $!\n";
257	}	319	}
258	};	320	};
259		321
		322	In addition to all the common open modes/flags ("O_RDONLY",
		323	"O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
		324	"O_APPEND"), the following POSIX and non-POSIX constants are
		325	available (missing ones on your system are, as usual, 0):
		326
		327	"O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
		328	"O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
		329	"O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
		330
260	aio_close $fh, $callback->($status)	331	aio_close $fh, $callback->($status)
261	Asynchronously close a file and call the callback with the result	332	Asynchronously close a file and call the callback with the result
262	code. WARNING: although accepted, you should not pass in a perl	333	code.
263	filehandle here, as perl will likely close the file descriptor
264	another time when the filehandle is destroyed. Normally, you can
265	safely call perls "close" or just let filehandles go out of scope.
266		334
267	This is supposed to be a bug in the API, so that might change. It's	335	Unfortunately, you can't do this to perl. Perl insists very
268	therefore best to avoid this function.	336	strongly on closing the file descriptor associated with the
		337	filehandle itself.
		338
		339	Therefore, "aio_close" will not close the filehandle - instead it
		340	will use dup2 to overwrite the file descriptor with the write-end of
		341	a pipe (the pipe fd will be created on demand and will be cached).
		342
		343	Or in other words: the file descriptor will be closed, but it will
		344	not be free for reuse until the perl filehandle is closed.
269		345
270	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	346	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
271	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	347	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
272	Reads or writes "length" bytes from the specified "fh" and "offset"	348	Reads or writes $length bytes from or to the specified $fh and
273	into the scalar given by "data" and offset "dataoffset" and calls	349	$offset into the scalar given by $data and offset $dataoffset and
274	the callback without the actual number of bytes read (or -1 on	350	calls the callback without the actual number of bytes read (or -1 on
275	error, just like the syscall).	351	error, just like the syscall).
276		352
		353	"aio_read" will, like "sysread", shrink or grow the $data scalar to
		354	offset plus the actual number of bytes read.
		355
		356	If $offset is undefined, then the current file descriptor offset
		357	will be used (and updated), otherwise the file descriptor offset
		358	will not be changed by these calls.
		359
		360	If $length is undefined in "aio_write", use the remaining length of
		361	$data.
		362
		363	If $dataoffset is less than zero, it will be counted from the end of
		364	$data.
		365
277	The $data scalar MUST NOT be modified in any way while the request	366	The $data scalar MUST NOT be modified in any way while the request
278	is outstanding. Modifying it can result in segfaults or WW3 (if the	367	is outstanding. Modifying it can result in segfaults or World War
279	necessary/optional hardware is installed).	368	III (if the necessary/optional hardware is installed).
280		369
281	Example: Read 15 bytes at offset 7 into scalar $buffer, starting at	370	Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
282	offset 0 within the scalar:	371	offset 0 within the scalar:
283		372
284	aio_read $fh, 7, 15, $buffer, 0, sub {	373	aio_read $fh, 7, 15, $buffer, 0, sub {
…		…
289	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	378	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
290	Tries to copy $length bytes from $in_fh to $out_fh. It starts	379	Tries to copy $length bytes from $in_fh to $out_fh. It starts
291	reading at byte offset $in_offset, and starts writing at the current	380	reading at byte offset $in_offset, and starts writing at the current
292	file offset of $out_fh. Because of that, it is not safe to issue	381	file offset of $out_fh. Because of that, it is not safe to issue
293	more than one "aio_sendfile" per $out_fh, as they will interfere	382	more than one "aio_sendfile" per $out_fh, as they will interfere
294	with each other.	383	with each other. The same $in_fh works fine though, as this function
		384	does not move or use the file offset of $in_fh.
295		385
		386	Please note that "aio_sendfile" can read more bytes from $in_fh than
		387	are written, and there is no way to find out how many more bytes
		388	have been read from "aio_sendfile" alone, as "aio_sendfile" only
		389	provides the number of bytes written to $out_fh. Only if the result
		390	value equals $length one can assume that $length bytes have been
		391	read.
		392
		393	Unlike with other "aio_" functions, it makes a lot of sense to use
		394	"aio_sendfile" on non-blocking sockets, as long as one end
		395	(typically the $in_fh) is a file - the file I/O will then be
		396	asynchronous, while the socket I/O will be non-blocking. Note,
		397	however, that you can run into a trap where "aio_sendfile" reads
		398	some data with readahead, then fails to write all data, and when the
		399	socket is ready the next time, the data in the cache is already
		400	lost, forcing "aio_sendfile" to again hit the disk. Explicit
		401	"aio_read" + "aio_write" let's you better control resource usage.
		402
296	This call tries to make use of a native "sendfile" syscall to	403	This call tries to make use of a native "sendfile"-like syscall to
297	provide zero-copy operation. For this to work, $out_fh should refer	404	provide zero-copy operation. For this to work, $out_fh should refer
298	to a socket, and $in_fh should refer to mmap'able file.	405	to a socket, and $in_fh should refer to an mmap'able file.
299		406
300	If the native sendfile call fails or is not implemented, it will be	407	If a native sendfile cannot be found or it fails with "ENOSYS",
301	emulated, so you can call "aio_sendfile" on any type of filehandle	408	"EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
302	regardless of the limitations of the operating system.	409	"ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
		410	any type of filehandle regardless of the limitations of the
		411	operating system.
303		412
304	Please note, however, that "aio_sendfile" can read more bytes from	413	As native sendfile syscalls (as practically any non-POSIX interface
305	$in_fh than are written, and there is no way to find out how many	414	hacked together in a hurry to improve benchmark numbers) tend to be
306	bytes have been read from "aio_sendfile" alone, as "aio_sendfile"	415	rather buggy on many systems, this implementation tries to work
307	only provides the number of bytes written to $out_fh. Only if the	416	around some known bugs in Linux and FreeBSD kernels (probably
308	result value equals $length one can assume that $length bytes have	417	others, too), but that might fail, so you really really should check
309	been read.	418	the return value of "aio_sendfile" - fewre bytes than expected might
		419	have been transferred.
310		420
311	aio_readahead $fh,$offset,$length, $callback->($retval)	421	aio_readahead $fh,$offset,$length, $callback->($retval)
312	"aio_readahead" populates the page cache with data from a file so	422	"aio_readahead" populates the page cache with data from a file so
313	that subsequent reads from that file will not block on disk I/O. The	423	that subsequent reads from that file will not block on disk I/O. The
314	$offset argument specifies the starting point from which data is to	424	$offset argument specifies the starting point from which data is to
…		…
335	Currently, the stats are always 64-bit-stats, i.e. instead of	445	Currently, the stats are always 64-bit-stats, i.e. instead of
336	returning an error when stat'ing a large file, the results will be	446	returning an error when stat'ing a large file, the results will be
337	silently truncated unless perl itself is compiled with large file	447	silently truncated unless perl itself is compiled with large file
338	support.	448	support.
339		449
		450	To help interpret the mode and dev/rdev stat values, IO::AIO offers
		451	the following constants and functions (if not implemented, the
		452	constants will be 0 and the functions will either "croak" or fall
		453	back on traditional behaviour).
		454
		455	"S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
		456	"S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
		457	"IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
		458
340	Example: Print the length of /etc/passwd:	459	Example: Print the length of /etc/passwd:
341		460
342	aio_stat "/etc/passwd", sub {	461	aio_stat "/etc/passwd", sub {
343	$_[0] and die "stat failed: $!";	462	$_[0] and die "stat failed: $!";
344	print "size is ", -s _, "\n";	463	print "size is ", -s _, "\n";
345	};	464	};
346		465
		466	aio_statvfs $fh_or_path, $callback->($statvfs)
		467	Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
		468	whether a file handle or path was passed.
		469
		470	On success, the callback is passed a hash reference with the
		471	following members: "bsize", "frsize", "blocks", "bfree", "bavail",
		472	"files", "ffree", "favail", "fsid", "flag" and "namemax". On
		473	failure, "undef" is passed.
		474
		475	The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
		476	and "ST_NOSUID".
		477
		478	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		479	their correct value when available, or to 0 on systems that do not
		480	support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
		481	"ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
		482	"ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
		483
		484	Example: stat "/wd" and dump out the data if successful.
		485
		486	aio_statvfs "/wd", sub {
		487	my $f = $_[0]
		488	or die "statvfs: $!";
		489
		490	use Data::Dumper;
		491	say Dumper $f;
		492	};
		493
		494	# result:
		495	{
		496	bsize => 1024,
		497	bfree => 4333064312,
		498	blocks => 10253828096,
		499	files => 2050765568,
		500	flag => 4096,
		501	favail => 2042092649,
		502	bavail => 4333064312,
		503	ffree => 2042092649,
		504	namemax => 255,
		505	frsize => 1024,
		506	fsid => 1810
		507	}
		508
		509	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		510	Works like perl's "utime" function (including the special case of
		511	$atime and $mtime being undef). Fractional times are supported if
		512	the underlying syscalls support them.
		513
		514	When called with a pathname, uses utimes(2) if available, otherwise
		515	utime(2). If called on a file descriptor, uses futimes(2) if
		516	available, otherwise returns ENOSYS, so this is not portable.
		517
		518	Examples:
		519
		520	# set atime and mtime to current time (basically touch(1)):
		521	aio_utime "path", undef, undef;
		522	# set atime to current time and mtime to beginning of the epoch:
		523	aio_utime "path", time, undef; # undef==0
		524
		525	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		526	Works like perl's "chown" function, except that "undef" for either
		527	$uid or $gid is being interpreted as "do not change" (but -1 can
		528	also be used).
		529
		530	Examples:
		531
		532	# same as "chown root path" in the shell:
		533	aio_chown "path", 0, -1;
		534	# same as above:
		535	aio_chown "path", 0, undef;
		536
		537	aio_truncate $fh_or_path, $offset, $callback->($status)
		538	Works like truncate(2) or ftruncate(2).
		539
		540	aio_chmod $fh_or_path, $mode, $callback->($status)
		541	Works like perl's "chmod" function.
		542
347	aio_unlink $pathname, $callback->($status)	543	aio_unlink $pathname, $callback->($status)
348	Asynchronously unlink (delete) a file and call the callback with the	544	Asynchronously unlink (delete) a file and call the callback with the
349	result code.	545	result code.
350		546
351	aio_mknod $path, $mode, $dev, $callback->($status)	547	aio_mknod $pathname, $mode, $dev, $callback->($status)
352	[EXPERIMENTAL]	548	[EXPERIMENTAL]
353		549
354	Asynchronously create a device node (or fifo). See mknod(2).	550	Asynchronously create a device node (or fifo). See mknod(2).
355		551
356	The only (POSIX-) portable way of calling this function is:	552	The only (POSIX-) portable way of calling this function is:
357		553
358	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...	554	aio_mknod $pathname, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		555
		556	See "aio_stat" for info about some potentially helpful extra
		557	constants and functions.
359		558
360	aio_link $srcpath, $dstpath, $callback->($status)	559	aio_link $srcpath, $dstpath, $callback->($status)
361	Asynchronously create a new link to the existing object at $srcpath	560	Asynchronously create a new link to the existing object at $srcpath
362	at the path $dstpath and call the callback with the result code.	561	at the path $dstpath and call the callback with the result code.
363		562
364	aio_symlink $srcpath, $dstpath, $callback->($status)	563	aio_symlink $srcpath, $dstpath, $callback->($status)
365	Asynchronously create a new symbolic link to the existing object at	564	Asynchronously create a new symbolic link to the existing object at
366	$srcpath at the path $dstpath and call the callback with the result	565	$srcpath at the path $dstpath and call the callback with the result
367	code.	566	code.
368		567
369	aio_readlink $path, $callback->($link)	568	aio_readlink $pathname, $callback->($link)
370	Asynchronously read the symlink specified by $path and pass it to	569	Asynchronously read the symlink specified by $path and pass it to
371	the callback. If an error occurs, nothing or undef gets passed to	570	the callback. If an error occurs, nothing or undef gets passed to
372	the callback.	571	the callback.
373		572
		573	aio_realpath $pathname, $callback->($path)
		574	Asynchronously make the path absolute and resolve any symlinks in
		575	$path. The resulting path only consists of directories (Same as
		576	Cwd::realpath).
		577
		578	This request can be used to get the absolute path of the current
		579	working directory by passing it a path of . (a single dot).
		580
374	aio_rename $srcpath, $dstpath, $callback->($status)	581	aio_rename $srcpath, $dstpath, $callback->($status)
375	Asynchronously rename the object at $srcpath to $dstpath, just as	582	Asynchronously rename the object at $srcpath to $dstpath, just as
376	rename(2) and call the callback with the result code.	583	rename(2) and call the callback with the result code.
		584
		585	aio_mkdir $pathname, $mode, $callback->($status)
		586	Asynchronously mkdir (create) a directory and call the callback with
		587	the result code. $mode will be modified by the umask at the time the
		588	request is executed, so do not change your umask.
377		589
378	aio_rmdir $pathname, $callback->($status)	590	aio_rmdir $pathname, $callback->($status)
379	Asynchronously rmdir (delete) a directory and call the callback with	591	Asynchronously rmdir (delete) a directory and call the callback with
380	the result code.	592	the result code.
381		593
382	aio_readdir $pathname, $callback->($entries)	594	aio_readdir $pathname, $callback->($entries)
383	Unlike the POSIX call of the same name, "aio_readdir" reads an	595	Unlike the POSIX call of the same name, "aio_readdir" reads an
384	entire directory (i.e. opendir + readdir + closedir). The entries	596	entire directory (i.e. opendir + readdir + closedir). The entries
385	will not be sorted, and will NOT include the "." and ".." entries.	597	will not be sorted, and will NOT include the "." and ".." entries.
386		598
387	The callback a single argument which is either "undef" or an	599	The callback is passed a single argument which is either "undef" or
388	array-ref with the filenames.	600	an array-ref with the filenames.
389		601
		602	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		603	Quite similar to "aio_readdir", but the $flags argument allows one
		604	to tune behaviour and output format. In case of an error, $entries
		605	will be "undef".
		606
		607	The flags are a combination of the following constants, ORed
		608	together (the flags will also be passed to the callback, possibly
		609	modified):
		610
		611	IO::AIO::READDIR_DENTS
		612	When this flag is off, then the callback gets an arrayref
		613	consisting of names only (as with "aio_readdir"), otherwise it
		614	gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
		615	describing a single directory entry in more detail.
		616
		617	$name is the name of the entry.
		618
		619	$type is one of the "IO::AIO::DT_xxx" constants:
		620
		621	"IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
		622	"IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
		623	"IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
		624
		625	"IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
		626	you need to know, you have to run stat yourself. Also, for speed
		627	reasons, the $type scalars are read-only: you can not modify
		628	them.
		629
		630	$inode is the inode number (which might not be exact on systems
		631	with 64 bit inode numbers and 32 bit perls). This field has
		632	unspecified content on systems that do not deliver the inode
		633	information.
		634
		635	IO::AIO::READDIR_DIRS_FIRST
		636	When this flag is set, then the names will be returned in an
		637	order where likely directories come first, in optimal stat
		638	order. This is useful when you need to quickly find directories,
		639	or you want to find all directories while avoiding to stat()
		640	each entry.
		641
		642	If the system returns type information in readdir, then this is
		643	used to find directories directly. Otherwise, likely directories
		644	are names beginning with ".", or otherwise names with no dots,
		645	of which names with short names are tried first.
		646
		647	IO::AIO::READDIR_STAT_ORDER
		648	When this flag is set, then the names will be returned in an
		649	order suitable for stat()'ing each one. That is, when you plan
		650	to stat() all files in the given directory, then the returned
		651	order will likely be fastest.
		652
		653	If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
		654	specified, then the likely dirs come first, resulting in a less
		655	optimal stat order.
		656
		657	IO::AIO::READDIR_FOUND_UNKNOWN
		658	This flag should not be set when calling "aio_readdirx".
		659	Instead, it is being set by "aio_readdirx", when any of the
		660	$type's found were "IO::AIO::DT_UNKNOWN". The absence of this
		661	flag therefore indicates that all $type's are known, which can
		662	be used to speed up some algorithms.
		663
390	aio_load $path, $data, $callback->($status)	664	aio_load $pathname, $data, $callback->($status)
391	This is a composite request that tries to fully load the given file	665	This is a composite request that tries to fully load the given file
392	into memory. Status is the same as with aio_read.	666	into memory. Status is the same as with aio_read.
393		667
394	aio_copy $srcpath, $dstpath, $callback->($status)	668	aio_copy $srcpath, $dstpath, $callback->($status)
395	Try to copy the file (directories not supported as either source	669	Try to copy the file (directories not supported as either source
396	or destination) from $srcpath to $dstpath and call the callback with	670	or destination) from $srcpath to $dstpath and call the callback with
397	the 0 (error) or -1 ok.	671	a status of 0 (ok) or -1 (error, see $!).
398		672
399	This is a composite request that it creates the destination file	673	This is a composite request that creates the destination file with
400	with mode 0200 and copies the contents of the source file into it	674	mode 0200 and copies the contents of the source file into it using
401	using "aio_sendfile", followed by restoring atime, mtime, access	675	"aio_sendfile", followed by restoring atime, mtime, access mode and
402	mode and uid/gid, in that order.	676	uid/gid, in that order.
403		677
404	If an error occurs, the partial destination file will be unlinked,	678	If an error occurs, the partial destination file will be unlinked,
405	if possible, except when setting atime, mtime, access mode and	679	if possible, except when setting atime, mtime, access mode and
406	uid/gid, where errors are being ignored.	680	uid/gid, where errors are being ignored.
407		681
408	aio_move $srcpath, $dstpath, $callback->($status)	682	aio_move $srcpath, $dstpath, $callback->($status)
409	Try to move the file (directories not supported as either source	683	Try to move the file (directories not supported as either source
410	or destination) from $srcpath to $dstpath and call the callback with	684	or destination) from $srcpath to $dstpath and call the callback with
411	the 0 (error) or -1 ok.	685	a status of 0 (ok) or -1 (error, see $!).
412		686
413	This is a composite request that tries to rename(2) the file first.	687	This is a composite request that tries to rename(2) the file first;
414	If rename files with "EXDEV", it copies the file with "aio_copy"	688	if rename fails with "EXDEV", it copies the file with "aio_copy"
415	and, if that is successful, unlinking the $srcpath.	689	and, if that is successful, unlinks the $srcpath.
416		690
417	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	691	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
418	Scans a directory (similar to "aio_readdir") but additionally tries	692	Scans a directory (similar to "aio_readdir") but additionally tries
419	to efficiently separate the entries of directory $path into two sets	693	to efficiently separate the entries of directory $path into two sets
420	of names, directories you can recurse into (directories), and ones	694	of names, directories you can recurse into (directories), and ones
421	you cannot recurse into (everything else, including symlinks to	695	you cannot recurse into (everything else, including symlinks to
422	directories).	696	directories).
…		…
440	Implementation notes.	714	Implementation notes.
441		715
442	The "aio_readdir" cannot be avoided, but "stat()"'ing every entry	716	The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
443	can.	717	can.
444		718
		719	If readdir returns file type information, then this is used directly
		720	to find directories.
		721
445	After reading the directory, the modification time, size etc. of the	722	Otherwise, after reading the directory, the modification time, size
446	directory before and after the readdir is checked, and if they match	723	etc. of the directory before and after the readdir is checked, and
447	(and isn't the current time), the link count will be used to decide	724	if they match (and isn't the current time), the link count will be
448	how many entries are directories (if >= 2). Otherwise, no knowledge	725	used to decide how many entries are directories (if >= 2).
449	of the number of subdirectories will be assumed.	726	Otherwise, no knowledge of the number of subdirectories will be
		727	assumed.
450		728
451	Then entries will be sorted into likely directories (everything	729	Then entries will be sorted into likely directories a non-initial
452	without a non-initial dot currently) and likely non-directories	730	dot currently) and likely non-directories (see "aio_readdirx"). Then
453	(everything else). Then every entry plus an appended "/." will be	731	every entry plus an appended "/." will be "stat"'ed, likely
454	"stat"'ed, likely directories first. If that succeeds, it assumes	732	directories first, in order of their inode numbers. If that
455	that the entry is a directory or a symlink to directory (which will	733	succeeds, it assumes that the entry is a directory or a symlink to
456	be checked seperately). This is often faster than stat'ing the entry	734	directory (which will be checked separately). This is often faster
457	itself because filesystems might detect the type of the entry	735	than stat'ing the entry itself because filesystems might detect the
458	without reading the inode data (e.g. ext2fs filetype feature).	736	type of the entry without reading the inode data (e.g. ext2fs
		737	filetype feature), even on systems that cannot return the filetype
		738	information on readdir.
459		739
460	If the known number of directories (link count - 2) has been	740	If the known number of directories (link count - 2) has been
461	reached, the rest of the entries is assumed to be non-directories.	741	reached, the rest of the entries is assumed to be non-directories.
462		742
463	This only works with certainty on POSIX (= UNIX) filesystems, which	743	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
465		745
466	It will also likely work on non-POSIX filesystems with reduced	746	It will also likely work on non-POSIX filesystems with reduced
467	efficiency as those tend to return 0 or 1 as link counts, which	747	efficiency as those tend to return 0 or 1 as link counts, which
468	disables the directory counting heuristic.	748	disables the directory counting heuristic.
469		749
		750	aio_rmtree $pathname, $callback->($status)
		751	Delete a directory tree starting (and including) $path, return the
		752	status of the final "rmdir" only. This is a composite request that
		753	uses "aio_scandir" to recurse into and rmdir directories, and unlink
		754	everything else.
		755
		756	aio_sync $callback->($status)
		757	Asynchronously call sync and call the callback when finished.
		758
470	aio_fsync $fh, $callback->($status)	759	aio_fsync $fh, $callback->($status)
471	Asynchronously call fsync on the given filehandle and call the	760	Asynchronously call fsync on the given filehandle and call the
472	callback with the fsync result code.	761	callback with the fsync result code.
473		762
474	aio_fdatasync $fh, $callback->($status)	763	aio_fdatasync $fh, $callback->($status)
475	Asynchronously call fdatasync on the given filehandle and call the	764	Asynchronously call fdatasync on the given filehandle and call the
476	callback with the fdatasync result code.	765	callback with the fdatasync result code.
477		766
478	If this call isn't available because your OS lacks it or it couldn't	767	If this call isn't available because your OS lacks it or it couldn't
479	be detected, it will be emulated by calling "fsync" instead.	768	be detected, it will be emulated by calling "fsync" instead.
		769
		770	aio_syncfs $fh, $callback->($status)
		771	Asynchronously call the syncfs syscall to sync the filesystem
		772	associated to the given filehandle and call the callback with the
		773	syncfs result code. If syncfs is not available, calls sync(), but
		774	returns -1 and sets errno to "ENOSYS" nevertheless.
		775
		776	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		777	Sync the data portion of the file specified by $offset and $length
		778	to disk (but NOT the metadata), by calling the Linux-specific
		779	sync_file_range call. If sync_file_range is not available or it
		780	returns ENOSYS, then fdatasync or fsync is being substituted.
		781
		782	$flags can be a combination of
		783	"IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
		784	"IO::AIO::SYNC_FILE_RANGE_WRITE" and
		785	"IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
		786	manpage for details.
		787
		788	aio_pathsync $pathname, $callback->($status)
		789	This request tries to open, fsync and close the given path. This is
		790	a composite request intended to sync directories after directory
		791	operations (E.g. rename). This might not work on all operating
		792	systems or have any specific effect, but usually it makes sure that
		793	directory changes get written to disc. It works for anything that
		794	can be opened for read-only, not just directories.
		795
		796	Future versions of this function might fall back to other methods
		797	when "fsync" on the directory fails (such as calling "sync").
		798
		799	Passes 0 when everything went ok, and -1 on error.
		800
		801	aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
		802	$callback->($status)
		803	This is a rather advanced IO::AIO call, which only works on
		804	mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
		805	also works on data scalars managed by the Sys::Mmap or Mmap modules,
		806	note that the scalar must only be modified in-place while an aio
		807	operation is pending on it).
		808
		809	It calls the "msync" function of your OS, if available, with the
		810	memory area starting at $offset in the string and ending $length
		811	bytes later. If $length is negative, counts from the end, and if
		812	$length is "undef", then it goes till the end of the string. The
		813	flags can be a combination of "IO::AIO::MS_ASYNC",
		814	"IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
		815
		816	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
		817	$callback->($status)
		818	This is a rather advanced IO::AIO call, which works best on
		819	mmap(2)ed scalars.
		820
		821	It touches (reads or writes) all memory pages in the specified range
		822	inside the scalar. All caveats and parameters are the same as for
		823	"aio_msync", above, except for flags, which must be either 0 (which
		824	reads all pages and ensures they are instantiated) or
		825	"IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
		826	and writing an octet from it, which dirties the page).
		827
		828	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		829	This is a rather advanced IO::AIO call, which works best on
		830	mmap(2)ed scalars.
		831
		832	It reads in all the pages of the underlying storage into memory (if
		833	any) and locks them, so they are not getting swapped/paged out or
		834	removed.
		835
		836	If $length is undefined, then the scalar will be locked till the
		837	end.
		838
		839	On systems that do not implement "mlock", this function returns -1
		840	and sets errno to "ENOSYS".
		841
		842	Note that the corresponding "munlock" is synchronous and is
		843	documented under "MISCELLANEOUS FUNCTIONS".
		844
		845	Example: open a file, mmap and mlock it - both will be undone when
		846	$data gets destroyed.
		847
		848	open my $fh, "<", $path or die "$path: $!";
		849	my $data;
		850	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		851	aio_mlock $data; # mlock in background
		852
		853	aio_mlockall $flags, $callback->($status)
		854	Calls the "mlockall" function with the given $flags (a combination
		855	of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
		856
		857	On systems that do not implement "mlockall", this function returns
		858	-1 and sets errno to "ENOSYS".
		859
		860	Note that the corresponding "munlockall" is synchronous and is
		861	documented under "MISCELLANEOUS FUNCTIONS".
		862
		863	Example: asynchronously lock all current and future pages into
		864	memory.
		865
		866	aio_mlockall IO::AIO::MCL_FUTURE;
480		867
481	aio_group $callback->(...)	868	aio_group $callback->(...)
482	This is a very special aio request: Instead of doing something, it	869	This is a very special aio request: Instead of doing something, it
483	is a container for other aio requests, which is useful if you want	870	is a container for other aio requests, which is useful if you want
484	to bundle many requests into a single, composite, request with a	871	to bundle many requests into a single, composite, request with a
…		…
519	requests like sleep and file handle readable/writable, the overhead	906	requests like sleep and file handle readable/writable, the overhead
520	this creates is immense (it blocks a thread for a long time) so do	907	this creates is immense (it blocks a thread for a long time) so do
521	not use this function except to put your application under	908	not use this function except to put your application under
522	artificial I/O pressure.	909	artificial I/O pressure.
523		910
		911	IO::AIO::WD - multiple working directories
		912	Your process only has one current working directory, which is used by
		913	all threads. This makes it hard to use relative paths (some other
		914	component could call "chdir" at any time, and it is hard to control when
		915	the path will be used by IO::AIO).
		916
		917	One solution for this is to always use absolute paths. This usually
		918	works, but can be quite slow (the kernel has to walk the whole path on
		919	every access), and can also be a hassle to implement.
		920
		921	Newer POSIX systems have a number of functions (openat, fdopendir,
		922	futimensat and so on) that make it possible to specify working
		923	directories per operation.
		924
		925	For portability, and because the clowns who "designed", or shall I
		926	write, perpetrated this new interface were obviously half-drunk, this
		927	abstraction cannot be perfect, though.
		928
		929	IO::AIO allows you to convert directory paths into a so-called
		930	IO::AIO::WD object. This object stores the canonicalised, absolute
		931	version of the path, and on systems that allow it, also a directory file
		932	descriptor.
		933
		934	Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
		935	or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
		936	object and a pathname instead (or the IO::AIO::WD object alone, which
		937	gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
		938	IO::AIO::WD object is ignored, otherwise the pathname is resolved
		939	relative to that IO::AIO::WD object.
		940
		941	For example, to get a wd object for /etc and then stat passwd inside,
		942	you would write:
		943
		944	aio_wd "/etc", sub {
		945	my $etcdir = shift;
		946
		947	# although $etcdir can be undef on error, there is generally no reason
		948	# to check for errors here, as aio_stat will fail with ENOENT
		949	# when $etcdir is undef.
		950
		951	aio_stat [$etcdir, "passwd"], sub {
		952	# yay
		953	};
		954	};
		955
		956	That "aio_wd" is a request and not a normal function shows that creating
		957	an IO::AIO::WD object is itself a potentially blocking operation, which
		958	is why it is done asynchronously.
		959
		960	To stat the directory obtained with "aio_wd" above, one could write
		961	either of the following three request calls:
		962
		963	aio_lstat "/etc" , sub { ... # pathname as normal string
		964	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		965	aio_lstat $wd , sub { ... # shorthand for the previous
		966
		967	As with normal pathnames, IO::AIO keeps a copy of the working directory
		968	object and the pathname string, so you could write the following without
		969	causing any issues due to $path getting reused:
		970
		971	my $path = [$wd, undef];
		972
		973	for my $name (qw(abc def ghi)) {
		974	$path->[1] = $name;
		975	aio_stat $path, sub {
		976	# ...
		977	};
		978	}
		979
		980	There are some caveats: when directories get renamed (or deleted), the
		981	pathname string doesn't change, so will point to the new directory (or
		982	nowhere at all), while the directory fd, if available on the system,
		983	will still point to the original directory. Most functions accepting a
		984	pathname will use the directory fd on newer systems, and the string on
		985	older systems. Some functions (such as realpath) will always rely on the
		986	string form of the pathname.
		987
		988	So this fucntionality is mainly useful to get some protection against
		989	"chdir", to easily get an absolute path out of a relative path for
		990	future reference, and to speed up doing many operations in the same
		991	directory (e.g. when stat'ing all files in a directory).
		992
		993	The following functions implement this working directory abstraction:
		994
		995	aio_wd $pathname, $callback->($wd)
		996	Asynchonously canonicalise the given pathname and convert it to an
		997	IO::AIO::WD object representing it. If possible and supported on the
		998	system, also open a directory fd to speed up pathname resolution
		999	relative to this working directory.
		1000
		1001	If something goes wrong, then "undef" is passwd to the callback
		1002	instead of a working directory object and $! is set appropriately.
		1003	Since passing "undef" as working directory component of a pathname
		1004	fails the request with "ENOENT", there is often no need for error
		1005	checking in the "aio_wd" callback, as future requests using the
		1006	value will fail in the expected way.
		1007
		1008	If this call isn't available because your OS lacks it or it couldn't
		1009	be detected, it will be emulated by calling "fsync" instead.
		1010
		1011	IO::AIO::CWD
		1012	This is a compiletime constant (object) that represents the process
		1013	current working directory.
		1014
		1015	Specifying this object as working directory object for a pathname is
		1016	as if the pathname would be specified directly, without a directory
		1017	object, e.g., these calls are functionally identical:
		1018
		1019	aio_stat "somefile", sub { ... };
		1020	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1021
524	IO::AIO::REQ CLASS	1022	IO::AIO::REQ CLASS
525	All non-aggregate "aio_*" functions return an object of this class when	1023	All non-aggregate "aio_*" functions return an object of this class when
526	called in non-void context.	1024	called in non-void context.
527		1025
528	cancel $req	1026	cancel $req
529	Cancels the request, if possible. Has the effect of skipping	1027	Cancels the request, if possible. Has the effect of skipping
530	execution when entering the execute state and skipping calling the	1028	execution when entering the execute state and skipping calling the
531	callback when entering the the result state, but will leave the	1029	callback when entering the the result state, but will leave the
532	request otherwise untouched. That means that requests that currently	1030	request otherwise untouched (with the exception of readdir). That
533	execute will not be stopped and resources held by the request will	1031	means that requests that currently execute will not be stopped and
534	not be freed prematurely.	1032	resources held by the request will not be freed prematurely.
535		1033
536	cb $req $callback->(...)	1034	cb $req $callback->(...)
537	Replace (or simply set) the callback registered to the request.	1035	Replace (or simply set) the callback registered to the request.
538		1036
539	IO::AIO::GRP CLASS	1037	IO::AIO::GRP CLASS
…		…
566	};	1064	};
567		1065
568	This makes it very easy to create composite requests (see the source of	1066	This makes it very easy to create composite requests (see the source of
569	"aio_move" for an application) that work and feel like simple requests.	1067	"aio_move" for an application) that work and feel like simple requests.
570		1068
571	* The IO::AIO::GRP objects will be cleaned up during calls to	1069	* The IO::AIO::GRP objects will be cleaned up during calls to
572	"IO::AIO::poll_cb", just like any other request.	1070	"IO::AIO::poll_cb", just like any other request.
		1071
573	* They can be canceled like any other request. Canceling will cancel not	1072	* They can be canceled like any other request. Canceling will cancel
574	only the request itself, but also all requests it contains.	1073	not only the request itself, but also all requests it contains.
		1074
575	* They can also can also be added to other IO::AIO::GRP objects.	1075	* They can also can also be added to other IO::AIO::GRP objects.
		1076
576	* You must not add requests to a group from within the group callback	1077	* You must not add requests to a group from within the group callback
577	(or any later time).	1078	(or any later time).
578		1079
579	Their lifetime, simplified, looks like this: when they are empty, they	1080	Their lifetime, simplified, looks like this: when they are empty, they
580	will finish very quickly. If they contain only requests that are in the	1081	will finish very quickly. If they contain only requests that are in the
581	"done" state, they will also finish. Otherwise they will continue to	1082	"done" state, they will also finish. Otherwise they will continue to
582	exist.	1083	exist.
583		1084
584	That means after creating a group you have some time to add requests.	1085	That means after creating a group you have some time to add requests
585	And in the callbacks of those requests, you can add further requests to	1086	(precisely before the callback has been invoked, which is only done
586	the group. And only when all those requests have finished will the the	1087	within the "poll_cb"). And in the callbacks of those requests, you can
587	group itself finish.	1088	add further requests to the group. And only when all those requests have
		1089	finished will the the group itself finish.
588		1090
589	add $grp ...	1091	add $grp ...
590	$grp->add (...)	1092	$grp->add (...)
591	Add one or more requests to the group. Any type of IO::AIO::REQ can	1093	Add one or more requests to the group. Any type of IO::AIO::REQ can
592	be added, including other groups, as long as you do not create	1094	be added, including other groups, as long as you do not create
…		…
597	$grp->cancel_subs	1099	$grp->cancel_subs
598	Cancel all subrequests and clears any feeder, but not the group	1100	Cancel all subrequests and clears any feeder, but not the group
599	request itself. Useful when you queued a lot of events but got a	1101	request itself. Useful when you queued a lot of events but got a
600	result early.	1102	result early.
601		1103
		1104	The group request will finish normally (you cannot add requests to
		1105	the group).
		1106
602	$grp->result (...)	1107	$grp->result (...)
603	Set the result value(s) that will be passed to the group callback	1108	Set the result value(s) that will be passed to the group callback
604	when all subrequests have finished and set thre groups errno to the	1109	when all subrequests have finished and set the groups errno to the
605	current value of errno (just like calling "errno" without an error	1110	current value of errno (just like calling "errno" without an error
606	number). By default, no argument will be passed and errno is zero.	1111	number). By default, no argument will be passed and errno is zero.
607		1112
608	$grp->errno ([$errno])	1113	$grp->errno ([$errno])
609	Sets the group errno value to $errno, or the current value of errno	1114	Sets the group errno value to $errno, or the current value of errno
…		…
620	Sets a feeder/generator on this group: every group can have an	1125	Sets a feeder/generator on this group: every group can have an
621	attached generator that generates requests if idle. The idea behind	1126	attached generator that generates requests if idle. The idea behind
622	this is that, although you could just queue as many requests as you	1127	this is that, although you could just queue as many requests as you
623	want in a group, this might starve other requests for a potentially	1128	want in a group, this might starve other requests for a potentially
624	long time. For example, "aio_scandir" might generate hundreds of	1129	long time. For example, "aio_scandir" might generate hundreds of
625	thousands "aio_stat" requests, delaying any later requests for a	1130	thousands of "aio_stat" requests, delaying any later requests for a
626	long time.	1131	long time.
627		1132
628	To avoid this, and allow incremental generation of requests, you can	1133	To avoid this, and allow incremental generation of requests, you can
629	instead a group and set a feeder on it that generates those	1134	instead a group and set a feeder on it that generates those
630	requests. The feed callback will be called whenever there are few	1135	requests. The feed callback will be called whenever there are few
…		…
635	does not impose any limits).	1140	does not impose any limits).
636		1141
637	If the feed does not queue more requests when called, it will be	1142	If the feed does not queue more requests when called, it will be
638	automatically removed from the group.	1143	automatically removed from the group.
639		1144
640	If the feed limit is 0, it will be set to 2 automatically.	1145	If the feed limit is 0 when this method is called, it will be set to
		1146	2 automatically.
641		1147
642	Example:	1148	Example:
643		1149
644	# stat all files in @files, but only ever use four aio requests concurrently:	1150	# stat all files in @files, but only ever use four aio requests concurrently:
645		1151
…		…
656	Sets the feeder limit for the group: The feeder will be called	1162	Sets the feeder limit for the group: The feeder will be called
657	whenever the group contains less than this many requests.	1163	whenever the group contains less than this many requests.
658		1164
659	Setting the limit to 0 will pause the feeding process.	1165	Setting the limit to 0 will pause the feeding process.
660		1166
		1167	The default value for the limit is 0, but note that setting a feeder
		1168	automatically bumps it up to 2.
		1169
661	SUPPORT FUNCTIONS	1170	SUPPORT FUNCTIONS
662	EVENT PROCESSING AND EVENT LOOP INTEGRATION	1171	EVENT PROCESSING AND EVENT LOOP INTEGRATION
663	$fileno = IO::AIO::poll_fileno	1172	$fileno = IO::AIO::poll_fileno
664	Return the request result pipe file descriptor. This filehandle	1173	Return the request result pipe file descriptor. This filehandle
665	must be polled for reading by some mechanism outside this module	1174	must be polled for reading by some mechanism outside this module
666	(e.g. Event or select, see below or the SYNOPSIS). If the pipe	1175	(e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
667	becomes readable you have to call "poll_cb" to check the results.	1176	pipe becomes readable you have to call "poll_cb" to check the
		1177	results.
668		1178
669	See "poll_cb" for an example.	1179	See "poll_cb" for an example.
670		1180
671	IO::AIO::poll_cb	1181	IO::AIO::poll_cb
672	Process some outstanding events on the result pipe. You have to call	1182	Process some outstanding events on the result pipe. You have to call
673	this regularly. Returns the number of events processed. Returns	1183	this regularly. Returns 0 if all events could be processed (or there
674	immediately when no events are outstanding. The amount of events	1184	were no events to process), or -1 if it returned earlier for
675	processed depends on the settings of "IO::AIO::max_poll_req" and	1185	whatever reason. Returns immediately when no events are outstanding.
676	"IO::AIO::max_poll_time".	1186	The amount of events processed depends on the settings of
		1187	"IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
677		1188
678	If not all requests were processed for whatever reason, the	1189	If not all requests were processed for whatever reason, the
679	filehandle will still be ready when "poll_cb" returns.	1190	filehandle will still be ready when "poll_cb" returns, so normally
		1191	you don't have to do anything special to have it called later.
		1192
		1193	Apart from calling "IO::AIO::poll_cb" when the event filehandle
		1194	becomes ready, it can be beneficial to call this function from loops
		1195	which submit a lot of requests, to make sure the results get
		1196	processed when they become available and not just when the loop is
		1197	finished and the event loop takes over again. This function returns
		1198	very fast when there are no outstanding requests.
680		1199
681	Example: Install an Event watcher that automatically calls	1200	Example: Install an Event watcher that automatically calls
682	IO::AIO::poll_cb with high priority:	1201	IO::AIO::poll_cb with high priority (more examples can be found in
		1202	the SYNOPSIS section, at the top of this document):
683		1203
684	Event->io (fd => IO::AIO::poll_fileno,	1204	Event->io (fd => IO::AIO::poll_fileno,
685	poll => 'r', async => 1,	1205	poll => 'r', async => 1,
686	cb => \&IO::AIO::poll_cb);	1206	cb => \&IO::AIO::poll_cb);
		1207
		1208	IO::AIO::poll_wait
		1209	If there are any outstanding requests and none of them in the result
		1210	phase, wait till the result filehandle becomes ready for reading
		1211	(simply does a "select" on the filehandle. This is useful if you
		1212	want to synchronously wait for some requests to finish).
		1213
		1214	See "nreqs" for an example.
		1215
		1216	IO::AIO::poll
		1217	Waits until some requests have been handled.
		1218
		1219	Returns the number of requests processed, but is otherwise strictly
		1220	equivalent to:
		1221
		1222	IO::AIO::poll_wait, IO::AIO::poll_cb
		1223
		1224	IO::AIO::flush
		1225	Wait till all outstanding AIO requests have been handled.
		1226
		1227	Strictly equivalent to:
		1228
		1229	IO::AIO::poll_wait, IO::AIO::poll_cb
		1230	while IO::AIO::nreqs;
687		1231
688	IO::AIO::max_poll_reqs $nreqs	1232	IO::AIO::max_poll_reqs $nreqs
689	IO::AIO::max_poll_time $seconds	1233	IO::AIO::max_poll_time $seconds
690	These set the maximum number of requests (default 0, meaning	1234	These set the maximum number of requests (default 0, meaning
691	infinity) that are being processed by "IO::AIO::poll_cb" in one	1235	infinity) that are being processed by "IO::AIO::poll_cb" in one
…		…
715	# use a low priority so other tasks have priority	1259	# use a low priority so other tasks have priority
716	Event->io (fd => IO::AIO::poll_fileno,	1260	Event->io (fd => IO::AIO::poll_fileno,
717	poll => 'r', nice => 1,	1261	poll => 'r', nice => 1,
718	cb => &IO::AIO::poll_cb);	1262	cb => &IO::AIO::poll_cb);
719		1263
720	IO::AIO::poll_wait
721	If there are any outstanding requests and none of them in the result
722	phase, wait till the result filehandle becomes ready for reading
723	(simply does a "select" on the filehandle. This is useful if you
724	want to synchronously wait for some requests to finish).
725
726	See "nreqs" for an example.
727
728	IO::AIO::poll
729	Waits until some requests have been handled.
730
731	Returns the number of requests processed, but is otherwise strictly
732	equivalent to:
733
734	IO::AIO::poll_wait, IO::AIO::poll_cb
735
736	IO::AIO::flush
737	Wait till all outstanding AIO requests have been handled.
738
739	Strictly equivalent to:
740
741	IO::AIO::poll_wait, IO::AIO::poll_cb
742	while IO::AIO::nreqs;
743
744	CONTROLLING THE NUMBER OF THREADS	1264	CONTROLLING THE NUMBER OF THREADS
745	IO::AIO::min_parallel $nthreads	1265	IO::AIO::min_parallel $nthreads
746	Set the minimum number of AIO threads to $nthreads. The current	1266	Set the minimum number of AIO threads to $nthreads. The current
747	default is 8, which means eight asynchronous operations can execute	1267	default is 8, which means eight asynchronous operations can execute
748	concurrently at any one time (the number of outstanding requests,	1268	concurrently at any one time (the number of outstanding requests,
…		…
777		1297
778	Under normal circumstances you don't need to call this function.	1298	Under normal circumstances you don't need to call this function.
779		1299
780	IO::AIO::max_idle $nthreads	1300	IO::AIO::max_idle $nthreads
781	Limit the number of threads (default: 4) that are allowed to idle	1301	Limit the number of threads (default: 4) that are allowed to idle
782	(i.e., threads that did not get a request to process within 10	1302	(i.e., threads that did not get a request to process within the idle
783	seconds). That means if a thread becomes idle while $nthreads other	1303	timeout (default: 10 seconds). That means if a thread becomes idle
784	threads are also idle, it will free its resources and exit.	1304	while $nthreads other threads are also idle, it will free its
		1305	resources and exit.
785		1306
786	This is useful when you allow a large number of threads (e.g. 100 or	1307	This is useful when you allow a large number of threads (e.g. 100 or
787	1000) to allow for extremely high load situations, but want to free	1308	1000) to allow for extremely high load situations, but want to free
788	resources under normal circumstances (1000 threads can easily	1309	resources under normal circumstances (1000 threads can easily
789	consume 30MB of RAM).	1310	consume 30MB of RAM).
790		1311
791	The default is probably ok in most situations, especially if thread	1312	The default is probably ok in most situations, especially if thread
792	creation is fast. If thread creation is very slow on your system you	1313	creation is fast. If thread creation is very slow on your system you
793	might want to use larger values.	1314	might want to use larger values.
794		1315
		1316	IO::AIO::idle_timeout $seconds
		1317	Sets the minimum idle timeout (default 10) after which worker
		1318	threads are allowed to exit. SEe "IO::AIO::max_idle".
		1319
795	$oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1320	IO::AIO::max_outstanding $maxreqs
		1321	Sets the maximum number of outstanding requests to $nreqs. If you do
		1322	queue up more than this number of requests, the next call to
		1323	"IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
		1324	"IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
		1325	no longer exceeded.
		1326
		1327	In other words, this setting does not enforce a queue limit, but can
		1328	be used to make poll functions block if the limit is exceeded.
		1329
796	This is a very bad function to use in interactive programs because	1330	This is a very bad function to use in interactive programs because
797	it blocks, and a bad way to reduce concurrency because it is	1331	it blocks, and a bad way to reduce concurrency because it is
798	inexact: Better use an "aio_group" together with a feed callback.	1332	inexact: Better use an "aio_group" together with a feed callback.
799		1333
800	Sets the maximum number of outstanding requests to $nreqs. If you to	1334	It's main use is in scripts without an event loop - when you want to
801	queue up more than this number of requests, the next call to the	1335	stat a lot of files, you can write somehting like this:
802	"poll_cb" (and "poll_some" and other functions calling "poll_cb")
803	function will block until the limit is no longer exceeded.
804		1336
805	The default value is very large, so there is no practical limit on	1337	IO::AIO::max_outstanding 32;
		1338
		1339	for my $path (...) {
		1340	aio_stat $path , ...;
		1341	IO::AIO::poll_cb;
		1342	}
		1343
		1344	IO::AIO::flush;
		1345
		1346	The call to "poll_cb" inside the loop will normally return
		1347	instantly, but as soon as more thna 32 reqeusts are in-flight, it
		1348	will block until some requests have been handled. This keeps the
		1349	loop from pushing a large number of "aio_stat" requests onto the
		1350	queue.
		1351
		1352	The default value for "max_outstanding" is very large, so there is
806	the number of outstanding requests.	1353	no practical limit on the number of outstanding requests.
807
808	You can still queue as many requests as you want. Therefore,
809	"max_oustsanding" is mainly useful in simple scripts (with low
810	values) or as a stop gap to shield against fatal memory overflow
811	(with large values).
812		1354
813	STATISTICAL INFORMATION	1355	STATISTICAL INFORMATION
814	IO::AIO::nreqs	1356	IO::AIO::nreqs
815	Returns the number of requests currently in the ready, execute or	1357	Returns the number of requests currently in the ready, execute or
816	pending states (i.e. for which their callback has not been invoked	1358	pending states (i.e. for which their callback has not been invoked
…		…
827		1369
828	IO::AIO::npending	1370	IO::AIO::npending
829	Returns the number of requests currently in the pending state	1371	Returns the number of requests currently in the pending state
830	(executed, but not yet processed by poll_cb).	1372	(executed, but not yet processed by poll_cb).
831		1373
		1374	MISCELLANEOUS FUNCTIONS
		1375	IO::AIO implements some functions that might be useful, but are not
		1376	asynchronous.
		1377
		1378	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1379	Calls the "eio_sendfile_sync" function, which is like
		1380	"aio_sendfile", but is blocking (this makes most sense if you know
		1381	the input data is likely cached already and the output filehandle is
		1382	set to non-blocking operations).
		1383
		1384	Returns the number of bytes copied, or -1 on error.
		1385
		1386	IO::AIO::fadvise $fh, $offset, $len, $advice
		1387	Simply calls the "posix_fadvise" function (see its manpage for
		1388	details). The following advice constants are available:
		1389	"IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
		1390	"IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
		1391	"IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
		1392
		1393	On systems that do not implement "posix_fadvise", this function
		1394	returns ENOSYS, otherwise the return value of "posix_fadvise".
		1395
		1396	IO::AIO::madvise $scalar, $offset, $len, $advice
		1397	Simply calls the "posix_madvise" function (see its manpage for
		1398	details). The following advice constants are available:
		1399	"IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
		1400	"IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
		1401	"IO::AIO::MADV_DONTNEED".
		1402
		1403	On systems that do not implement "posix_madvise", this function
		1404	returns ENOSYS, otherwise the return value of "posix_madvise".
		1405
		1406	IO::AIO::mprotect $scalar, $offset, $len, $protect
		1407	Simply calls the "mprotect" function on the preferably AIO::mmap'ed
		1408	$scalar (see its manpage for details). The following protect
		1409	constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
		1410	"IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
		1411
		1412	On systems that do not implement "mprotect", this function returns
		1413	ENOSYS, otherwise the return value of "mprotect".
		1414
		1415	IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1416	Memory-maps a file (or anonymous memory range) and attaches it to
		1417	the given $scalar, which will act like a string scalar.
		1418
		1419	The only operations allowed on the scalar are "substr"/"vec" that
		1420	don't change the string length, and most read-only operations such
		1421	as copying it or searching it with regexes and so on.
		1422
		1423	Anything else is unsafe and will, at best, result in memory leaks.
		1424
		1425	The memory map associated with the $scalar is automatically removed
		1426	when the $scalar is destroyed, or when the "IO::AIO::mmap" or
		1427	"IO::AIO::munmap" functions are called.
		1428
		1429	This calls the "mmap"(2) function internally. See your system's
		1430	manual page for details on the $length, $prot and $flags parameters.
		1431
		1432	The $length must be larger than zero and smaller than the actual
		1433	filesize.
		1434
		1435	$prot is a combination of "IO::AIO::PROT_NONE",
		1436	"IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
		1437	"IO::AIO::PROT_WRITE",
		1438
		1439	$flags can be a combination of "IO::AIO::MAP_SHARED" or
		1440	"IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
		1441	not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
		1442	(which is set to "MAP_ANON" if your system only provides this
		1443	constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
		1444	"IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
		1445	"IO::AIO::MAP_NONBLOCK"
		1446
		1447	If $fh is "undef", then a file descriptor of -1 is passed.
		1448
		1449	$offset is the offset from the start of the file - it generally must
		1450	be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
		1451
		1452	Example:
		1453
		1454	use Digest::MD5;
		1455	use IO::AIO;
		1456
		1457	open my $fh, "<verybigfile"
		1458	or die "$!";
		1459
		1460	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1461	or die "verybigfile: $!";
		1462
		1463	my $fast_md5 = md5 $data;
		1464
		1465	IO::AIO::munmap $scalar
		1466	Removes a previous mmap and undefines the $scalar.
		1467
		1468	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1469	Calls the "munlock" function, undoing the effects of a previous
		1470	"aio_mlock" call (see its description for details).
		1471
		1472	IO::AIO::munlockall
		1473	Calls the "munlockall" function.
		1474
		1475	On systems that do not implement "munlockall", this function returns
		1476	ENOSYS, otherwise the return value of "munlockall".
		1477
		1478	EVENT LOOP INTEGRATION
		1479	It is recommended to use AnyEvent::AIO to integrate IO::AIO
		1480	automatically into many event loops:
		1481
		1482	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1483	use AnyEvent::AIO;
		1484
		1485	You can also integrate IO::AIO manually into many event loops, here are
		1486	some examples of how to do this:
		1487
		1488	# EV integration
		1489	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1490
		1491	# Event integration
		1492	Event->io (fd => IO::AIO::poll_fileno,
		1493	poll => 'r',
		1494	cb => \&IO::AIO::poll_cb);
		1495
		1496	# Glib/Gtk2 integration
		1497	add_watch Glib::IO IO::AIO::poll_fileno,
		1498	in => sub { IO::AIO::poll_cb; 1 };
		1499
		1500	# Tk integration
		1501	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1502	readable => \&IO::AIO::poll_cb);
		1503
		1504	# Danga::Socket integration
		1505	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1506	\&IO::AIO::poll_cb);
		1507
832	FORK BEHAVIOUR	1508	FORK BEHAVIOUR
833	This module should do "the right thing" when the process using it forks:	1509	Usage of pthreads in a program changes the semantics of fork
		1510	considerably. Specifically, only async-safe functions can be called
		1511	after fork. Perl doesn't know about this, so in general, you cannot call
		1512	fork with defined behaviour in perl if pthreads are involved. IO::AIO
		1513	uses pthreads, so this applies, but many other extensions and (for
		1514	inexplicable reasons) perl itself often is linked against pthreads, so
		1515	this limitation applies to quite a lot of perls.
834		1516
835	Before the fork, IO::AIO enters a quiescent state where no requests can	1517	This module no longer tries to fight your OS, or POSIX. That means
836	be added in other threads and no results will be processed. After the	1518	IO::AIO only works in the process that loaded it. Forking is fully
837	fork the parent simply leaves the quiescent state and continues	1519	supported, but using IO::AIO in the child is not.
838	request/result processing, while the child frees the request/result
839	queue (so that the requests started before the fork will only be handled
840	in the parent). Threads will be started on demand until the limit set in
841	the parent process has been reached again.
842		1520
843	In short: the parent will, after a short pause, continue as if fork had	1521	You might get around by not using IO::AIO before (or after) forking.
844	not been called, while the child will act as if IO::AIO has not been	1522	You could also try to call the IO::AIO::reinit function in the child:
845	used yet.	1523
		1524	IO::AIO::reinit
		1525	Abandons all current requests and I/O threads and simply
		1526	reinitialises all data structures. This is not an operation
		1527	supported by any standards, but happens to work on GNU/Linux and
		1528	some newer BSD systems.
		1529
		1530	The only reasonable use for this function is to call it after
		1531	forking, if "IO::AIO" was used in the parent. Calling it while
		1532	IO::AIO is active in the process will result in undefined behaviour.
		1533	Calling it at any time will also result in any undefined (by POSIX)
		1534	behaviour.
846		1535
847	MEMORY USAGE	1536	MEMORY USAGE
848	Per-request usage:	1537	Per-request usage:
849		1538
850	Each aio request uses - depending on your architecture - around 100-200	1539	Each aio request uses - depending on your architecture - around 100-200
851	bytes of memory. In addition, stat requests need a stat buffer (possibly	1540	bytes of memory. In addition, stat requests need a stat buffer (possibly
852	a few hundred bytes), readdir requires a result buffer and so on. Perl	1541	a few hundred bytes), readdir requires a result buffer and so on. Perl
853	scalars and other data passed into aio requests will also be locked and	1542	scalars and other data passed into aio requests will also be locked and
854	will consume memory till the request has entered the done state.	1543	will consume memory till the request has entered the done state.
855		1544
856	This is now awfully much, so queuing lots of requests is not usually a	1545	This is not awfully much, so queuing lots of requests is not usually a
857	problem.	1546	problem.
858		1547
859	Per-thread usage:	1548	Per-thread usage:
860		1549
861	In the execution phase, some aio requests require more memory for	1550	In the execution phase, some aio requests require more memory for
…		…
864		1553
865	KNOWN BUGS	1554	KNOWN BUGS
866	Known bugs will be fixed in the next release.	1555	Known bugs will be fixed in the next release.
867		1556
868	SEE ALSO	1557	SEE ALSO
869	Coro::AIO.	1558	AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
		1559	more natural syntax.
870		1560
871	AUTHOR	1561	AUTHOR
872	Marc Lehmann <schmorp@schmorp.de>	1562	Marc Lehmann <schmorp@schmorp.de>
873	http://home.schmorp.de/	1563	http://home.schmorp.de/
874		1564

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Revision 1.50 by root, Sun Oct 9 08:24:49 2011 UTC