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

Comparing IO-AIO/README (file contents):
Revision 1.20 by root, Tue Oct 31 00:45:41 2006 UTC vs.
Revision 1.49 by root, Mon Jul 18 03:09:06 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) = @_;	8	my $fh = shift
		9	or die "/etc/passwd: $!";
9	...	10	...
10	};	11	};
11		12
12	aio_unlink "/tmp/file", sub { };	13	aio_unlink "/tmp/file", sub { };
13		14
…		…
23	$req->cancel; # cancel request if still in queue	24	$req->cancel; # cancel request if still in queue
24		25
25	my $grp = aio_group sub { print "all stats done\n" };	26	my $grp = aio_group sub { print "all stats done\n" };
26	add $grp aio_stat "..." for ...;	27	add $grp aio_stat "..." for ...;
27		28
28	# AnyEvent integration
29	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
30	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
31
32	# Event integration
33	Event->io (fd => IO::AIO::poll_fileno,
34	poll => 'r',
35	cb => \&IO::AIO::poll_cb);
36
37	# Glib/Gtk2 integration
38	add_watch Glib::IO IO::AIO::poll_fileno,
39	in => sub { IO::AIO::poll_cb; 1 };
40
41	# Tk integration
42	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
43	readable => \&IO::AIO::poll_cb);
44
45	# Danga::Socket integration
46	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
47	\&IO::AIO::poll_cb);
48
49	DESCRIPTION	29	DESCRIPTION
50	This module implements asynchronous I/O using whatever means your	30	This module implements asynchronous I/O using whatever means your
51	operating system supports.	31	operating system supports. It is implemented as an interface to "libeio"
		32	(<http://software.schmorp.de/pkg/libeio.html>).
52		33
53	Asynchronous means that operations that can normally block your program	34	Asynchronous means that operations that can normally block your program
54	(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
55	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
56	extremely useful for programs that need to stay interactive even when	37	extremely useful for programs that need to stay interactive even when
…		…
60	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
61	operations concurrently.	42	operations concurrently.
62		43
63	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
64	sockets), using these functions on file descriptors that support	45	sockets), using these functions on file descriptors that support
65	nonblocking operation (again, sockets, pipes etc.) is very inefficient	46	nonblocking operation (again, sockets, pipes etc.) is very inefficient.
66	or might not work (aio_read fails on sockets/pipes/fifos). Use an event
67	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
68	into such an event loop itself.	48	naturally fit into such an event loop itself.
69		49
70	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
71	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
72	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
73	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
…		…
75	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
76	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
77	aio_write, so the remaining functionality would have to be implemented	57	aio_write, so the remaining functionality would have to be implemented
78	using threads anyway.	58	using threads anyway.
79		59
80	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,
81	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
82	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
83	never call "poll_cb" (or other "aio_" functions) recursively.	63	call "poll_cb" (or other "aio_" functions) recursively.
84		64
85	EXAMPLE	65	EXAMPLE
86	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
87	/etc/passwd asynchronously:	67	asynchronously:
88		68
89	use Fcntl;	69	use Fcntl;
90	use Event;	70	use EV;
91	use IO::AIO;	71	use IO::AIO;
92		72
93	# register the IO::AIO callback with Event	73	# register the IO::AIO callback with EV
94	Event->io (fd => IO::AIO::poll_fileno,	74	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
95	poll => 'r',
96	cb => \&IO::AIO::poll_cb);
97		75
98	# queue the request to open /etc/passwd	76	# queue the request to open /etc/passwd
99	aio_open "/etc/passwd", O_RDONLY, 0, sub {	77	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
100	my $fh = $_[0]	78	my $fh = shift
101	or die "error while opening: $!";	79	or die "error while opening: $!";
102		80
103	# stat'ing filehandles is generally non-blocking	81	# stat'ing filehandles is generally non-blocking
104	my $size = -s $fh;	82	my $size = -s $fh;
105		83
…		…
113		91
114	# file contents now in $contents	92	# file contents now in $contents
115	print $contents;	93	print $contents;
116		94
117	# exit event loop and program	95	# exit event loop and program
118	Event::unloop;	96	EV::unloop;
119	};	97	};
120	};	98	};
121		99
122	# possibly queue up other requests, or open GUI windows,	100	# possibly queue up other requests, or open GUI windows,
123	# check for sockets etc. etc.	101	# check for sockets etc. etc.
124		102
125	# process events as long as there are some:	103	# process events as long as there are some:
126	Event::loop;	104	EV::loop;
127		105
128	REQUEST ANATOMY AND LIFETIME	106	REQUEST ANATOMY AND LIFETIME
129	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
130	not directly visible to Perl.	108	not directly visible to Perl.
131		109
…		…
167	anymore (except possibly for the Perl object, but its connection to	145	anymore (except possibly for the Perl object, but its connection to
168	the actual aio request is severed and calling its methods will	146	the actual aio request is severed and calling its methods will
169	either do nothing or result in a runtime error).	147	either do nothing or result in a runtime error).
170		148
171	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_open $pathname, $flags, $mode, $callback->($fh)
		156	aio_close $fh, $callback->($status)
		157	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		158	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		159	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		160	aio_readahead $fh,$offset,$length, $callback->($retval)
		161	aio_stat $fh_or_path, $callback->($status)
		162	aio_lstat $fh, $callback->($status)
		163	aio_statvfs $fh_or_path, $callback->($statvfs)
		164	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		165	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		166	aio_truncate $fh_or_path, $offset, $callback->($status)
		167	aio_chmod $fh_or_path, $mode, $callback->($status)
		168	aio_unlink $pathname, $callback->($status)
		169	aio_mknod $path, $mode, $dev, $callback->($status)
		170	aio_link $srcpath, $dstpath, $callback->($status)
		171	aio_symlink $srcpath, $dstpath, $callback->($status)
		172	aio_readlink $path, $callback->($link)
		173	aio_realpath $path, $callback->($link)
		174	aio_rename $srcpath, $dstpath, $callback->($status)
		175	aio_mkdir $pathname, $mode, $callback->($status)
		176	aio_rmdir $pathname, $callback->($status)
		177	aio_readdir $pathname, $callback->($entries)
		178	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		179	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		180	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		181	aio_load $path, $data, $callback->($status)
		182	aio_copy $srcpath, $dstpath, $callback->($status)
		183	aio_move $srcpath, $dstpath, $callback->($status)
		184	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		185	aio_rmtree $path, $callback->($status)
		186	aio_sync $callback->($status)
		187	aio_fsync $fh, $callback->($status)
		188	aio_fdatasync $fh, $callback->($status)
		189	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		190	aio_pathsync $path, $callback->($status)
		191	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		192	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		193	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		194	aio_mlockall $flags, $callback->($status)
		195	aio_group $callback->(...)
		196	aio_nop $callback->()
		197
		198	$prev_pri = aioreq_pri [$pri]
		199	aioreq_nice $pri_adjust
		200
		201	IO::AIO::poll_wait
		202	IO::AIO::poll_cb
		203	IO::AIO::poll
		204	IO::AIO::flush
		205	IO::AIO::max_poll_reqs $nreqs
		206	IO::AIO::max_poll_time $seconds
		207	IO::AIO::min_parallel $nthreads
		208	IO::AIO::max_parallel $nthreads
		209	IO::AIO::max_idle $nthreads
		210	IO::AIO::idle_timeout $seconds
		211	IO::AIO::max_outstanding $maxreqs
		212	IO::AIO::nreqs
		213	IO::AIO::nready
		214	IO::AIO::npending
		215
		216	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		217	IO::AIO::fadvise $fh, $offset, $len, $advice
		218	IO::AIO::madvise $scalar, $offset, $length, $advice
		219	IO::AIO::mprotect $scalar, $offset, $length, $protect
		220	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		221	IO::AIO::munlockall
		222
172	AIO REQUEST FUNCTIONS	223	AIO REQUEST FUNCTIONS
173	All the "aio_*" calls are more or less thin wrappers around the syscall	224	All the "aio_*" calls are more or less thin wrappers around the syscall
174	with the same name (sans "aio_"). The arguments are similar or	225	with the same name (sans "aio_"). The arguments are similar or
175	identical, and they all accept an additional (and optional) $callback	226	identical, and they all accept an additional (and optional) $callback
176	argument which must be a code reference. This code reference will get	227	argument which must be a code reference. This code reference will get
177	called with the syscall return code (e.g. most syscalls return -1 on	228	called with the syscall return code (e.g. most syscalls return -1 on
178	error, unlike perl, which usually delivers "false") as it's sole	229	error, unlike perl, which usually delivers "false") as its sole argument
179	argument when the given syscall has been executed asynchronously.	230	after the given syscall has been executed asynchronously.
180		231
181	All functions expecting a filehandle keep a copy of the filehandle	232	All functions expecting a filehandle keep a copy of the filehandle
182	internally until the request has finished.	233	internally until the request has finished.
183		234
184	All functions return request objects of type IO::AIO::REQ that allow	235	All functions return request objects of type IO::AIO::REQ that allow
…		…
197	the user environment, d) use Glib::filename_from_unicode on unicode	248	the user environment, d) use Glib::filename_from_unicode on unicode
198	filenames or e) use something else to ensure your scalar has the correct	249	filenames or e) use something else to ensure your scalar has the correct
199	contents.	250	contents.
200		251
201	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	252	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
202	handles correctly wether it is set or not.	253	handles correctly whether it is set or not.
203		254
204	$prev_pri = aioreq_pri [$pri]	255	$prev_pri = aioreq_pri [$pri]
205	Returns the priority value that would be used for the next request	256	Returns the priority value that would be used for the next request
206	and, if $pri is given, sets the priority for the next aio request.	257	and, if $pri is given, sets the priority for the next aio request.
207		258
…		…
241	They are the same as used by "sysopen".	292	They are the same as used by "sysopen".
242		293
243	Likewise, $mode specifies the mode of the newly created file, if it	294	Likewise, $mode specifies the mode of the newly created file, if it
244	didn't exist and "O_CREAT" has been given, just like perl's	295	didn't exist and "O_CREAT" has been given, just like perl's
245	"sysopen", except that it is mandatory (i.e. use 0 if you don't	296	"sysopen", except that it is mandatory (i.e. use 0 if you don't
246	create new files, and 0666 or 0777 if you do).	297	create new files, and 0666 or 0777 if you do). Note that the $mode
		298	will be modified by the umask in effect then the request is being
		299	executed, so better never change the umask.
247		300
248	Example:	301	Example:
249		302
250	aio_open "/etc/passwd", O_RDONLY, 0, sub {	303	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
251	if ($_[0]) {	304	if ($_[0]) {
252	print "open successful, fh is $_[0]\n";	305	print "open successful, fh is $_[0]\n";
253	...	306	...
254	} else {	307	} else {
255	die "open failed: $!\n";	308	die "open failed: $!\n";
256	}	309	}
257	};	310	};
258		311
		312	In addition to all the common open modes/flags ("O_RDONLY",
		313	"O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
		314	"O_APPEND"), the following POSIX and non-POSIX constants are
		315	available (missing ones on your system are, as usual, 0):
		316
		317	"O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
		318	"O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
		319	"O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
		320
259	aio_close $fh, $callback->($status)	321	aio_close $fh, $callback->($status)
260	Asynchronously close a file and call the callback with the result	322	Asynchronously close a file and call the callback with the result
261	code. WARNING: although accepted, you should not pass in a perl	323	code.
262	filehandle here, as perl will likely close the file descriptor
263	another time when the filehandle is destroyed. Normally, you can
264	safely call perls "close" or just let filehandles go out of scope.
265		324
266	This is supposed to be a bug in the API, so that might change. It's	325	Unfortunately, you can't do this to perl. Perl insists very
267	therefore best to avoid this function.	326	strongly on closing the file descriptor associated with the
		327	filehandle itself.
		328
		329	Therefore, "aio_close" will not close the filehandle - instead it
		330	will use dup2 to overwrite the file descriptor with the write-end of
		331	a pipe (the pipe fd will be created on demand and will be cached).
		332
		333	Or in other words: the file descriptor will be closed, but it will
		334	not be free for reuse until the perl filehandle is closed.
268		335
269	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	336	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
270	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	337	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
271	Reads or writes "length" bytes from the specified "fh" and "offset"	338	Reads or writes $length bytes from or to the specified $fh and
272	into the scalar given by "data" and offset "dataoffset" and calls	339	$offset into the scalar given by $data and offset $dataoffset and
273	the callback without the actual number of bytes read (or -1 on	340	calls the callback without the actual number of bytes read (or -1 on
274	error, just like the syscall).	341	error, just like the syscall).
275		342
		343	"aio_read" will, like "sysread", shrink or grow the $data scalar to
		344	offset plus the actual number of bytes read.
		345
		346	If $offset is undefined, then the current file descriptor offset
		347	will be used (and updated), otherwise the file descriptor offset
		348	will not be changed by these calls.
		349
		350	If $length is undefined in "aio_write", use the remaining length of
		351	$data.
		352
		353	If $dataoffset is less than zero, it will be counted from the end of
		354	$data.
		355
276	The $data scalar MUST NOT be modified in any way while the request	356	The $data scalar MUST NOT be modified in any way while the request
277	is outstanding. Modifying it can result in segfaults or WW3 (if the	357	is outstanding. Modifying it can result in segfaults or World War
278	necessary/optional hardware is installed).	358	III (if the necessary/optional hardware is installed).
279		359
280	Example: Read 15 bytes at offset 7 into scalar $buffer, starting at	360	Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
281	offset 0 within the scalar:	361	offset 0 within the scalar:
282		362
283	aio_read $fh, 7, 15, $buffer, 0, sub {	363	aio_read $fh, 7, 15, $buffer, 0, sub {
…		…
288	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	368	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
289	Tries to copy $length bytes from $in_fh to $out_fh. It starts	369	Tries to copy $length bytes from $in_fh to $out_fh. It starts
290	reading at byte offset $in_offset, and starts writing at the current	370	reading at byte offset $in_offset, and starts writing at the current
291	file offset of $out_fh. Because of that, it is not safe to issue	371	file offset of $out_fh. Because of that, it is not safe to issue
292	more than one "aio_sendfile" per $out_fh, as they will interfere	372	more than one "aio_sendfile" per $out_fh, as they will interfere
293	with each other.	373	with each other. The same $in_fh works fine though, as this function
		374	does not move or use the file offset of $in_fh.
294		375
		376	Please note that "aio_sendfile" can read more bytes from $in_fh than
		377	are written, and there is no way to find out how many more bytes
		378	have been read from "aio_sendfile" alone, as "aio_sendfile" only
		379	provides the number of bytes written to $out_fh. Only if the result
		380	value equals $length one can assume that $length bytes have been
		381	read.
		382
		383	Unlike with other "aio_" functions, it makes a lot of sense to use
		384	"aio_sendfile" on non-blocking sockets, as long as one end
		385	(typically the $in_fh) is a file - the file I/O will then be
		386	asynchronous, while the socket I/O will be non-blocking. Note,
		387	however, that you can run into a trap where "aio_sendfile" reads
		388	some data with readahead, then fails to write all data, and when the
		389	socket is ready the next time, the data in the cache is already
		390	lost, forcing "aio_sendfile" to again hit the disk. Explicit
		391	"aio_read" + "aio_write" let's you better control resource usage.
		392
295	This call tries to make use of a native "sendfile" syscall to	393	This call tries to make use of a native "sendfile"-like syscall to
296	provide zero-copy operation. For this to work, $out_fh should refer	394	provide zero-copy operation. For this to work, $out_fh should refer
297	to a socket, and $in_fh should refer to mmap'able file.	395	to a socket, and $in_fh should refer to an mmap'able file.
298		396
299	If the native sendfile call fails or is not implemented, it will be	397	If a native sendfile cannot be found or it fails with "ENOSYS",
300	emulated, so you can call "aio_sendfile" on any type of filehandle	398	"EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
301	regardless of the limitations of the operating system.	399	"ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
		400	any type of filehandle regardless of the limitations of the
		401	operating system.
302		402
303	Please note, however, that "aio_sendfile" can read more bytes from	403	As native sendfile syscalls (as practically any non-POSIX interface
304	$in_fh than are written, and there is no way to find out how many	404	hacked together in a hurry to improve benchmark numbers) tend to be
305	bytes have been read from "aio_sendfile" alone, as "aio_sendfile"	405	rather buggy on many systems, this implementation tries to work
306	only provides the number of bytes written to $out_fh. Only if the	406	around some known bugs in Linux and FreeBSD kernels (probably
307	result value equals $length one can assume that $length bytes have	407	others, too), but that might fail, so you really really should check
308	been read.	408	the return value of "aio_sendfile" - fewre bytes than expected might
		409	have been transferred.
309		410
310	aio_readahead $fh,$offset,$length, $callback->($retval)	411	aio_readahead $fh,$offset,$length, $callback->($retval)
311	"aio_readahead" populates the page cache with data from a file so	412	"aio_readahead" populates the page cache with data from a file so
312	that subsequent reads from that file will not block on disk I/O. The	413	that subsequent reads from that file will not block on disk I/O. The
313	$offset argument specifies the starting point from which data is to	414	$offset argument specifies the starting point from which data is to
…		…
334	Currently, the stats are always 64-bit-stats, i.e. instead of	435	Currently, the stats are always 64-bit-stats, i.e. instead of
335	returning an error when stat'ing a large file, the results will be	436	returning an error when stat'ing a large file, the results will be
336	silently truncated unless perl itself is compiled with large file	437	silently truncated unless perl itself is compiled with large file
337	support.	438	support.
338		439
		440	To help interpret the mode and dev/rdev stat values, IO::AIO offers
		441	the following constants and functions (if not implemented, the
		442	constants will be 0 and the functions will either "croak" or fall
		443	back on traditional behaviour).
		444
		445	"S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
		446	"S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
		447	"IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
		448
339	Example: Print the length of /etc/passwd:	449	Example: Print the length of /etc/passwd:
340		450
341	aio_stat "/etc/passwd", sub {	451	aio_stat "/etc/passwd", sub {
342	$_[0] and die "stat failed: $!";	452	$_[0] and die "stat failed: $!";
343	print "size is ", -s _, "\n";	453	print "size is ", -s _, "\n";
344	};	454	};
345		455
		456	aio_statvfs $fh_or_path, $callback->($statvfs)
		457	Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
		458	whether a file handle or path was passed.
		459
		460	On success, the callback is passed a hash reference with the
		461	following members: "bsize", "frsize", "blocks", "bfree", "bavail",
		462	"files", "ffree", "favail", "fsid", "flag" and "namemax". On
		463	failure, "undef" is passed.
		464
		465	The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
		466	and "ST_NOSUID".
		467
		468	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		469	their correct value when available, or to 0 on systems that do not
		470	support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
		471	"ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
		472	"ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
		473
		474	Example: stat "/wd" and dump out the data if successful.
		475
		476	aio_statvfs "/wd", sub {
		477	my $f = $_[0]
		478	or die "statvfs: $!";
		479
		480	use Data::Dumper;
		481	say Dumper $f;
		482	};
		483
		484	# result:
		485	{
		486	bsize => 1024,
		487	bfree => 4333064312,
		488	blocks => 10253828096,
		489	files => 2050765568,
		490	flag => 4096,
		491	favail => 2042092649,
		492	bavail => 4333064312,
		493	ffree => 2042092649,
		494	namemax => 255,
		495	frsize => 1024,
		496	fsid => 1810
		497	}
		498
		499	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		500	Works like perl's "utime" function (including the special case of
		501	$atime and $mtime being undef). Fractional times are supported if
		502	the underlying syscalls support them.
		503
		504	When called with a pathname, uses utimes(2) if available, otherwise
		505	utime(2). If called on a file descriptor, uses futimes(2) if
		506	available, otherwise returns ENOSYS, so this is not portable.
		507
		508	Examples:
		509
		510	# set atime and mtime to current time (basically touch(1)):
		511	aio_utime "path", undef, undef;
		512	# set atime to current time and mtime to beginning of the epoch:
		513	aio_utime "path", time, undef; # undef==0
		514
		515	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		516	Works like perl's "chown" function, except that "undef" for either
		517	$uid or $gid is being interpreted as "do not change" (but -1 can
		518	also be used).
		519
		520	Examples:
		521
		522	# same as "chown root path" in the shell:
		523	aio_chown "path", 0, -1;
		524	# same as above:
		525	aio_chown "path", 0, undef;
		526
		527	aio_truncate $fh_or_path, $offset, $callback->($status)
		528	Works like truncate(2) or ftruncate(2).
		529
		530	aio_chmod $fh_or_path, $mode, $callback->($status)
		531	Works like perl's "chmod" function.
		532
346	aio_unlink $pathname, $callback->($status)	533	aio_unlink $pathname, $callback->($status)
347	Asynchronously unlink (delete) a file and call the callback with the	534	Asynchronously unlink (delete) a file and call the callback with the
348	result code.	535	result code.
349		536
350	aio_mknod $path, $mode, $dev, $callback->($status)	537	aio_mknod $path, $mode, $dev, $callback->($status)
…		…
353	Asynchronously create a device node (or fifo). See mknod(2).	540	Asynchronously create a device node (or fifo). See mknod(2).
354		541
355	The only (POSIX-) portable way of calling this function is:	542	The only (POSIX-) portable way of calling this function is:
356		543
357	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...	544	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		545
		546	See "aio_stat" for info about some potentially helpful extra
		547	constants and functions.
358		548
359	aio_link $srcpath, $dstpath, $callback->($status)	549	aio_link $srcpath, $dstpath, $callback->($status)
360	Asynchronously create a new link to the existing object at $srcpath	550	Asynchronously create a new link to the existing object at $srcpath
361	at the path $dstpath and call the callback with the result code.	551	at the path $dstpath and call the callback with the result code.
362		552
…		…
368	aio_readlink $path, $callback->($link)	558	aio_readlink $path, $callback->($link)
369	Asynchronously read the symlink specified by $path and pass it to	559	Asynchronously read the symlink specified by $path and pass it to
370	the callback. If an error occurs, nothing or undef gets passed to	560	the callback. If an error occurs, nothing or undef gets passed to
371	the callback.	561	the callback.
372		562
		563	aio_realpath $path, $callback->($path)
		564	Asynchronously make the path absolute and resolve any symlinks in
		565	$path. The resulting path only consists of directories (Same as
		566	Cwd::realpath).
		567
		568	This request can be used to get the absolute path of the current
		569	working directory by passing it a path of . (a single dot).
		570
373	aio_rename $srcpath, $dstpath, $callback->($status)	571	aio_rename $srcpath, $dstpath, $callback->($status)
374	Asynchronously rename the object at $srcpath to $dstpath, just as	572	Asynchronously rename the object at $srcpath to $dstpath, just as
375	rename(2) and call the callback with the result code.	573	rename(2) and call the callback with the result code.
		574
		575	aio_mkdir $pathname, $mode, $callback->($status)
		576	Asynchronously mkdir (create) a directory and call the callback with
		577	the result code. $mode will be modified by the umask at the time the
		578	request is executed, so do not change your umask.
376		579
377	aio_rmdir $pathname, $callback->($status)	580	aio_rmdir $pathname, $callback->($status)
378	Asynchronously rmdir (delete) a directory and call the callback with	581	Asynchronously rmdir (delete) a directory and call the callback with
379	the result code.	582	the result code.
380		583
381	aio_readdir $pathname, $callback->($entries)	584	aio_readdir $pathname, $callback->($entries)
382	Unlike the POSIX call of the same name, "aio_readdir" reads an	585	Unlike the POSIX call of the same name, "aio_readdir" reads an
383	entire directory (i.e. opendir + readdir + closedir). The entries	586	entire directory (i.e. opendir + readdir + closedir). The entries
384	will not be sorted, and will NOT include the "." and ".." entries.	587	will not be sorted, and will NOT include the "." and ".." entries.
385		588
386	The callback a single argument which is either "undef" or an	589	The callback is passed a single argument which is either "undef" or
387	array-ref with the filenames.	590	an array-ref with the filenames.
		591
		592	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		593	Quite similar to "aio_readdir", but the $flags argument allows to
		594	tune behaviour and output format. In case of an error, $entries will
		595	be "undef".
		596
		597	The flags are a combination of the following constants, ORed
		598	together (the flags will also be passed to the callback, possibly
		599	modified):
		600
		601	IO::AIO::READDIR_DENTS
		602	When this flag is off, then the callback gets an arrayref
		603	consisting of names only (as with "aio_readdir"), otherwise it
		604	gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
		605	describing a single directory entry in more detail.
		606
		607	$name is the name of the entry.
		608
		609	$type is one of the "IO::AIO::DT_xxx" constants:
		610
		611	"IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
		612	"IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
		613	"IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
		614
		615	"IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
		616	you need to know, you have to run stat yourself. Also, for speed
		617	reasons, the $type scalars are read-only: you can not modify
		618	them.
		619
		620	$inode is the inode number (which might not be exact on systems
		621	with 64 bit inode numbers and 32 bit perls). This field has
		622	unspecified content on systems that do not deliver the inode
		623	information.
		624
		625	IO::AIO::READDIR_DIRS_FIRST
		626	When this flag is set, then the names will be returned in an
		627	order where likely directories come first, in optimal stat
		628	order. This is useful when you need to quickly find directories,
		629	or you want to find all directories while avoiding to stat()
		630	each entry.
		631
		632	If the system returns type information in readdir, then this is
		633	used to find directories directly. Otherwise, likely directories
		634	are names beginning with ".", or otherwise names with no dots,
		635	of which names with short names are tried first.
		636
		637	IO::AIO::READDIR_STAT_ORDER
		638	When this flag is set, then the names will be returned in an
		639	order suitable for stat()'ing each one. That is, when you plan
		640	to stat() all files in the given directory, then the returned
		641	order will likely be fastest.
		642
		643	If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
		644	specified, then the likely dirs come first, resulting in a less
		645	optimal stat order.
		646
		647	IO::AIO::READDIR_FOUND_UNKNOWN
		648	This flag should not be set when calling "aio_readdirx".
		649	Instead, it is being set by "aio_readdirx", when any of the
		650	$type's found were "IO::AIO::DT_UNKNOWN". The absense of this
		651	flag therefore indicates that all $type's are known, which can
		652	be used to speed up some algorithms.
		653
		654	aio_load $path, $data, $callback->($status)
		655	This is a composite request that tries to fully load the given file
		656	into memory. Status is the same as with aio_read.
388		657
389	aio_copy $srcpath, $dstpath, $callback->($status)	658	aio_copy $srcpath, $dstpath, $callback->($status)
390	Try to copy the file (directories not supported as either source	659	Try to copy the file (directories not supported as either source
391	or destination) from $srcpath to $dstpath and call the callback with	660	or destination) from $srcpath to $dstpath and call the callback with
392	the 0 (error) or -1 ok.	661	a status of 0 (ok) or -1 (error, see $!).
393		662
394	This is a composite request that it creates the destination file	663	This is a composite request that creates the destination file with
395	with mode 0200 and copies the contents of the source file into it	664	mode 0200 and copies the contents of the source file into it using
396	using "aio_sendfile", followed by restoring atime, mtime, access	665	"aio_sendfile", followed by restoring atime, mtime, access mode and
397	mode and uid/gid, in that order.	666	uid/gid, in that order.
398		667
399	If an error occurs, the partial destination file will be unlinked,	668	If an error occurs, the partial destination file will be unlinked,
400	if possible, except when setting atime, mtime, access mode and	669	if possible, except when setting atime, mtime, access mode and
401	uid/gid, where errors are being ignored.	670	uid/gid, where errors are being ignored.
402		671
403	aio_move $srcpath, $dstpath, $callback->($status)	672	aio_move $srcpath, $dstpath, $callback->($status)
404	Try to move the file (directories not supported as either source	673	Try to move the file (directories not supported as either source
405	or destination) from $srcpath to $dstpath and call the callback with	674	or destination) from $srcpath to $dstpath and call the callback with
406	the 0 (error) or -1 ok.	675	a status of 0 (ok) or -1 (error, see $!).
407		676
408	This is a composite request that tries to rename(2) the file first.	677	This is a composite request that tries to rename(2) the file first;
409	If rename files with "EXDEV", it copies the file with "aio_copy"	678	if rename fails with "EXDEV", it copies the file with "aio_copy"
410	and, if that is successful, unlinking the $srcpath.	679	and, if that is successful, unlinks the $srcpath.
411		680
412	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	681	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
413	Scans a directory (similar to "aio_readdir") but additionally tries	682	Scans a directory (similar to "aio_readdir") but additionally tries
414	to efficiently separate the entries of directory $path into two sets	683	to efficiently separate the entries of directory $path into two sets
415	of names, directories you can recurse into (directories), and ones	684	of names, directories you can recurse into (directories), and ones
…		…
435	Implementation notes.	704	Implementation notes.
436		705
437	The "aio_readdir" cannot be avoided, but "stat()"'ing every entry	706	The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
438	can.	707	can.
439		708
		709	If readdir returns file type information, then this is used directly
		710	to find directories.
		711
440	After reading the directory, the modification time, size etc. of the	712	Otherwise, after reading the directory, the modification time, size
441	directory before and after the readdir is checked, and if they match	713	etc. of the directory before and after the readdir is checked, and
442	(and isn't the current time), the link count will be used to decide	714	if they match (and isn't the current time), the link count will be
443	how many entries are directories (if >= 2). Otherwise, no knowledge	715	used to decide how many entries are directories (if >= 2).
444	of the number of subdirectories will be assumed.	716	Otherwise, no knowledge of the number of subdirectories will be
		717	assumed.
445		718
446	Then entries will be sorted into likely directories (everything	719	Then entries will be sorted into likely directories a non-initial
447	without a non-initial dot currently) and likely non-directories	720	dot currently) and likely non-directories (see "aio_readdirx"). Then
448	(everything else). Then every entry plus an appended "/." will be	721	every entry plus an appended "/." will be "stat"'ed, likely
449	"stat"'ed, likely directories first. If that succeeds, it assumes	722	directories first, in order of their inode numbers. If that
450	that the entry is a directory or a symlink to directory (which will	723	succeeds, it assumes that the entry is a directory or a symlink to
451	be checked seperately). This is often faster than stat'ing the entry	724	directory (which will be checked seperately). This is often faster
452	itself because filesystems might detect the type of the entry	725	than stat'ing the entry itself because filesystems might detect the
453	without reading the inode data (e.g. ext2fs filetype feature).	726	type of the entry without reading the inode data (e.g. ext2fs
		727	filetype feature), even on systems that cannot return the filetype
		728	information on readdir.
454		729
455	If the known number of directories (link count - 2) has been	730	If the known number of directories (link count - 2) has been
456	reached, the rest of the entries is assumed to be non-directories.	731	reached, the rest of the entries is assumed to be non-directories.
457		732
458	This only works with certainty on POSIX (= UNIX) filesystems, which	733	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
460		735
461	It will also likely work on non-POSIX filesystems with reduced	736	It will also likely work on non-POSIX filesystems with reduced
462	efficiency as those tend to return 0 or 1 as link counts, which	737	efficiency as those tend to return 0 or 1 as link counts, which
463	disables the directory counting heuristic.	738	disables the directory counting heuristic.
464		739
		740	aio_rmtree $path, $callback->($status)
		741	Delete a directory tree starting (and including) $path, return the
		742	status of the final "rmdir" only. This is a composite request that
		743	uses "aio_scandir" to recurse into and rmdir directories, and unlink
		744	everything else.
		745
		746	aio_sync $callback->($status)
		747	Asynchronously call sync and call the callback when finished.
		748
465	aio_fsync $fh, $callback->($status)	749	aio_fsync $fh, $callback->($status)
466	Asynchronously call fsync on the given filehandle and call the	750	Asynchronously call fsync on the given filehandle and call the
467	callback with the fsync result code.	751	callback with the fsync result code.
468		752
469	aio_fdatasync $fh, $callback->($status)	753	aio_fdatasync $fh, $callback->($status)
470	Asynchronously call fdatasync on the given filehandle and call the	754	Asynchronously call fdatasync on the given filehandle and call the
471	callback with the fdatasync result code.	755	callback with the fdatasync result code.
472		756
473	If this call isn't available because your OS lacks it or it couldn't	757	If this call isn't available because your OS lacks it or it couldn't
474	be detected, it will be emulated by calling "fsync" instead.	758	be detected, it will be emulated by calling "fsync" instead.
		759
		760	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		761	Sync the data portion of the file specified by $offset and $length
		762	to disk (but NOT the metadata), by calling the Linux-specific
		763	sync_file_range call. If sync_file_range is not available or it
		764	returns ENOSYS, then fdatasync or fsync is being substituted.
		765
		766	$flags can be a combination of
		767	"IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
		768	"IO::AIO::SYNC_FILE_RANGE_WRITE" and
		769	"IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
		770	manpage for details.
		771
		772	aio_pathsync $path, $callback->($status)
		773	This request tries to open, fsync and close the given path. This is
		774	a composite request intended to sync directories after directory
		775	operations (E.g. rename). This might not work on all operating
		776	systems or have any specific effect, but usually it makes sure that
		777	directory changes get written to disc. It works for anything that
		778	can be opened for read-only, not just directories.
		779
		780	Future versions of this function might fall back to other methods
		781	when "fsync" on the directory fails (such as calling "sync").
		782
		783	Passes 0 when everything went ok, and -1 on error.
		784
		785	aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
		786	$callback->($status)
		787	This is a rather advanced IO::AIO call, which only works on
		788	mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
		789	also works on data scalars managed by the Sys::Mmap or Mmap modules,
		790	note that the scalar must only be modified in-place while an aio
		791	operation is pending on it).
		792
		793	It calls the "msync" function of your OS, if available, with the
		794	memory area starting at $offset in the string and ending $length
		795	bytes later. If $length is negative, counts from the end, and if
		796	$length is "undef", then it goes till the end of the string. The
		797	flags can be a combination of "IO::AIO::MS_ASYNC",
		798	"IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
		799
		800	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
		801	$callback->($status)
		802	This is a rather advanced IO::AIO call, which works best on
		803	mmap(2)ed scalars.
		804
		805	It touches (reads or writes) all memory pages in the specified range
		806	inside the scalar. All caveats and parameters are the same as for
		807	"aio_msync", above, except for flags, which must be either 0 (which
		808	reads all pages and ensures they are instantiated) or
		809	"IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
		810	and writing an octet from it, which dirties the page).
		811
		812	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		813	This is a rather advanced IO::AIO call, which works best on
		814	mmap(2)ed scalars.
		815
		816	It reads in all the pages of the underlying storage into memory (if
		817	any) and locks them, so they are not getting swapped/paged out or
		818	removed.
		819
		820	If $length is undefined, then the scalar will be locked till the
		821	end.
		822
		823	On systems that do not implement "mlock", this function returns -1
		824	and sets errno to "ENOSYS".
		825
		826	Note that the corresponding "munlock" is synchronous and is
		827	documented under "MISCELLANEOUS FUNCTIONS".
		828
		829	Example: open a file, mmap and mlock it - both will be undone when
		830	$data gets destroyed.
		831
		832	open my $fh, "<", $path or die "$path: $!";
		833	my $data;
		834	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		835	aio_mlock $data; # mlock in background
		836
		837	aio_mlockall $flags, $callback->($status)
		838	Calls the "mlockall" function with the given $flags (a combination
		839	of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
		840
		841	On systems that do not implement "mlockall", this function returns
		842	-1 and sets errno to "ENOSYS".
		843
		844	Note that the corresponding "munlockall" is synchronous and is
		845	documented under "MISCELLANEOUS FUNCTIONS".
		846
		847	Example: asynchronously lock all current and future pages into
		848	memory.
		849
		850	aio_mlockall IO::AIO::MCL_FUTURE;
475		851
476	aio_group $callback->(...)	852	aio_group $callback->(...)
477	This is a very special aio request: Instead of doing something, it	853	This is a very special aio request: Instead of doing something, it
478	is a container for other aio requests, which is useful if you want	854	is a container for other aio requests, which is useful if you want
479	to bundle many requests into a single, composite, request with a	855	to bundle many requests into a single, composite, request with a
…		…
522		898
523	cancel $req	899	cancel $req
524	Cancels the request, if possible. Has the effect of skipping	900	Cancels the request, if possible. Has the effect of skipping
525	execution when entering the execute state and skipping calling the	901	execution when entering the execute state and skipping calling the
526	callback when entering the the result state, but will leave the	902	callback when entering the the result state, but will leave the
527	request otherwise untouched. That means that requests that currently	903	request otherwise untouched (with the exception of readdir). That
528	execute will not be stopped and resources held by the request will	904	means that requests that currently execute will not be stopped and
529	not be freed prematurely.	905	resources held by the request will not be freed prematurely.
530		906
531	cb $req $callback->(...)	907	cb $req $callback->(...)
532	Replace (or simply set) the callback registered to the request.	908	Replace (or simply set) the callback registered to the request.
533		909
534	IO::AIO::GRP CLASS	910	IO::AIO::GRP CLASS
…		…
561	};	937	};
562		938
563	This makes it very easy to create composite requests (see the source of	939	This makes it very easy to create composite requests (see the source of
564	"aio_move" for an application) that work and feel like simple requests.	940	"aio_move" for an application) that work and feel like simple requests.
565		941
566	* The IO::AIO::GRP objects will be cleaned up during calls to	942	* The IO::AIO::GRP objects will be cleaned up during calls to
567	"IO::AIO::poll_cb", just like any other request.	943	"IO::AIO::poll_cb", just like any other request.
		944
568	* They can be canceled like any other request. Canceling will cancel not	945	* They can be canceled like any other request. Canceling will cancel
569	only the request itself, but also all requests it contains.	946	not only the request itself, but also all requests it contains.
		947
570	* They can also can also be added to other IO::AIO::GRP objects.	948	* They can also can also be added to other IO::AIO::GRP objects.
		949
571	* You must not add requests to a group from within the group callback	950	* You must not add requests to a group from within the group callback
572	(or any later time).	951	(or any later time).
573		952
574	Their lifetime, simplified, looks like this: when they are empty, they	953	Their lifetime, simplified, looks like this: when they are empty, they
575	will finish very quickly. If they contain only requests that are in the	954	will finish very quickly. If they contain only requests that are in the
576	"done" state, they will also finish. Otherwise they will continue to	955	"done" state, they will also finish. Otherwise they will continue to
577	exist.	956	exist.
578		957
579	That means after creating a group you have some time to add requests.	958	That means after creating a group you have some time to add requests
580	And in the callbacks of those requests, you can add further requests to	959	(precisely before the callback has been invoked, which is only done
581	the group. And only when all those requests have finished will the the	960	within the "poll_cb"). And in the callbacks of those requests, you can
582	group itself finish.	961	add further requests to the group. And only when all those requests have
		962	finished will the the group itself finish.
583		963
584	add $grp ...	964	add $grp ...
585	$grp->add (...)	965	$grp->add (...)
586	Add one or more requests to the group. Any type of IO::AIO::REQ can	966	Add one or more requests to the group. Any type of IO::AIO::REQ can
587	be added, including other groups, as long as you do not create	967	be added, including other groups, as long as you do not create
…		…
592	$grp->cancel_subs	972	$grp->cancel_subs
593	Cancel all subrequests and clears any feeder, but not the group	973	Cancel all subrequests and clears any feeder, but not the group
594	request itself. Useful when you queued a lot of events but got a	974	request itself. Useful when you queued a lot of events but got a
595	result early.	975	result early.
596		976
		977	The group request will finish normally (you cannot add requests to
		978	the group).
		979
597	$grp->result (...)	980	$grp->result (...)
598	Set the result value(s) that will be passed to the group callback	981	Set the result value(s) that will be passed to the group callback
599	when all subrequests have finished and set thre groups errno to the	982	when all subrequests have finished and set the groups errno to the
600	current value of errno (just like calling "errno" without an error	983	current value of errno (just like calling "errno" without an error
601	number). By default, no argument will be passed and errno is zero.	984	number). By default, no argument will be passed and errno is zero.
602		985
603	$grp->errno ([$errno])	986	$grp->errno ([$errno])
604	Sets the group errno value to $errno, or the current value of errno	987	Sets the group errno value to $errno, or the current value of errno
…		…
630	does not impose any limits).	1013	does not impose any limits).
631		1014
632	If the feed does not queue more requests when called, it will be	1015	If the feed does not queue more requests when called, it will be
633	automatically removed from the group.	1016	automatically removed from the group.
634		1017
635	If the feed limit is 0, it will be set to 2 automatically.	1018	If the feed limit is 0 when this method is called, it will be set to
		1019	2 automatically.
636		1020
637	Example:	1021	Example:
638		1022
639	# stat all files in @files, but only ever use four aio requests concurrently:	1023	# stat all files in @files, but only ever use four aio requests concurrently:
640		1024
…		…
651	Sets the feeder limit for the group: The feeder will be called	1035	Sets the feeder limit for the group: The feeder will be called
652	whenever the group contains less than this many requests.	1036	whenever the group contains less than this many requests.
653		1037
654	Setting the limit to 0 will pause the feeding process.	1038	Setting the limit to 0 will pause the feeding process.
655		1039
		1040	The default value for the limit is 0, but note that setting a feeder
		1041	automatically bumps it up to 2.
		1042
656	SUPPORT FUNCTIONS	1043	SUPPORT FUNCTIONS
657	EVENT PROCESSING AND EVENT LOOP INTEGRATION	1044	EVENT PROCESSING AND EVENT LOOP INTEGRATION
658	$fileno = IO::AIO::poll_fileno	1045	$fileno = IO::AIO::poll_fileno
659	Return the request result pipe file descriptor. This filehandle	1046	Return the request result pipe file descriptor. This filehandle
660	must be polled for reading by some mechanism outside this module	1047	must be polled for reading by some mechanism outside this module
661	(e.g. Event or select, see below or the SYNOPSIS). If the pipe	1048	(e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
662	becomes readable you have to call "poll_cb" to check the results.	1049	pipe becomes readable you have to call "poll_cb" to check the
		1050	results.
663		1051
664	See "poll_cb" for an example.	1052	See "poll_cb" for an example.
665		1053
666	IO::AIO::poll_cb	1054	IO::AIO::poll_cb
667	Process some outstanding events on the result pipe. You have to call	1055	Process some outstanding events on the result pipe. You have to call
668	this regularly. Returns the number of events processed. Returns	1056	this regularly. Returns 0 if all events could be processed (or there
669	immediately when no events are outstanding. The amount of events	1057	were no events to process), or -1 if it returned earlier for
670	processed depends on the settings of "IO::AIO::max_poll_req" and	1058	whatever reason. Returns immediately when no events are outstanding.
671	"IO::AIO::max_poll_time".	1059	The amount of events processed depends on the settings of
		1060	"IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
672		1061
673	If not all requests were processed for whatever reason, the	1062	If not all requests were processed for whatever reason, the
674	filehandle will still be ready when "poll_cb" returns.	1063	filehandle will still be ready when "poll_cb" returns, so normally
		1064	you don't have to do anything special to have it called later.
		1065
		1066	Apart from calling "IO::AIO::poll_cb" when the event filehandle
		1067	becomes ready, it can be beneficial to call this function from loops
		1068	which submit a lot of requests, to make sure the results get
		1069	processed when they become available and not just when the loop is
		1070	finished and the event loop takes over again. This function returns
		1071	very fast when there are no outstanding requests.
675		1072
676	Example: Install an Event watcher that automatically calls	1073	Example: Install an Event watcher that automatically calls
677	IO::AIO::poll_cb with high priority:	1074	IO::AIO::poll_cb with high priority (more examples can be found in
		1075	the SYNOPSIS section, at the top of this document):
678		1076
679	Event->io (fd => IO::AIO::poll_fileno,	1077	Event->io (fd => IO::AIO::poll_fileno,
680	poll => 'r', async => 1,	1078	poll => 'r', async => 1,
681	cb => \&IO::AIO::poll_cb);	1079	cb => \&IO::AIO::poll_cb);
		1080
		1081	IO::AIO::poll_wait
		1082	If there are any outstanding requests and none of them in the result
		1083	phase, wait till the result filehandle becomes ready for reading
		1084	(simply does a "select" on the filehandle. This is useful if you
		1085	want to synchronously wait for some requests to finish).
		1086
		1087	See "nreqs" for an example.
		1088
		1089	IO::AIO::poll
		1090	Waits until some requests have been handled.
		1091
		1092	Returns the number of requests processed, but is otherwise strictly
		1093	equivalent to:
		1094
		1095	IO::AIO::poll_wait, IO::AIO::poll_cb
		1096
		1097	IO::AIO::flush
		1098	Wait till all outstanding AIO requests have been handled.
		1099
		1100	Strictly equivalent to:
		1101
		1102	IO::AIO::poll_wait, IO::AIO::poll_cb
		1103	while IO::AIO::nreqs;
682		1104
683	IO::AIO::max_poll_reqs $nreqs	1105	IO::AIO::max_poll_reqs $nreqs
684	IO::AIO::max_poll_time $seconds	1106	IO::AIO::max_poll_time $seconds
685	These set the maximum number of requests (default 0, meaning	1107	These set the maximum number of requests (default 0, meaning
686	infinity) that are being processed by "IO::AIO::poll_cb" in one	1108	infinity) that are being processed by "IO::AIO::poll_cb" in one
…		…
710	# use a low priority so other tasks have priority	1132	# use a low priority so other tasks have priority
711	Event->io (fd => IO::AIO::poll_fileno,	1133	Event->io (fd => IO::AIO::poll_fileno,
712	poll => 'r', nice => 1,	1134	poll => 'r', nice => 1,
713	cb => &IO::AIO::poll_cb);	1135	cb => &IO::AIO::poll_cb);
714		1136
715	IO::AIO::poll_wait
716	Wait till the result filehandle becomes ready for reading (simply
717	does a "select" on the filehandle. This is useful if you want to
718	synchronously wait for some requests to finish).
719
720	See "nreqs" for an example.
721
722	IO::AIO::poll
723	Waits until some requests have been handled.
724
725	Strictly equivalent to:
726
727	IO::AIO::poll_wait, IO::AIO::poll_cb
728	if IO::AIO::nreqs;
729
730	IO::AIO::flush
731	Wait till all outstanding AIO requests have been handled.
732
733	Strictly equivalent to:
734
735	IO::AIO::poll_wait, IO::AIO::poll_cb
736	while IO::AIO::nreqs;
737
738	CONTROLLING THE NUMBER OF THREADS	1137	CONTROLLING THE NUMBER OF THREADS
739	IO::AIO::min_parallel $nthreads	1138	IO::AIO::min_parallel $nthreads
740	Set the minimum number of AIO threads to $nthreads. The current	1139	Set the minimum number of AIO threads to $nthreads. The current
741	default is 8, which means eight asynchronous operations can execute	1140	default is 8, which means eight asynchronous operations can execute
742	concurrently at any one time (the number of outstanding requests,	1141	concurrently at any one time (the number of outstanding requests,
…		…
771		1170
772	Under normal circumstances you don't need to call this function.	1171	Under normal circumstances you don't need to call this function.
773		1172
774	IO::AIO::max_idle $nthreads	1173	IO::AIO::max_idle $nthreads
775	Limit the number of threads (default: 4) that are allowed to idle	1174	Limit the number of threads (default: 4) that are allowed to idle
776	(i.e., threads that did not get a request to process within 10	1175	(i.e., threads that did not get a request to process within the idle
777	seconds). That means if a thread becomes idle while $nthreads other	1176	timeout (default: 10 seconds). That means if a thread becomes idle
778	threads are also idle, it will free its resources and exit.	1177	while $nthreads other threads are also idle, it will free its
		1178	resources and exit.
779		1179
780	This is useful when you allow a large number of threads (e.g. 100 or	1180	This is useful when you allow a large number of threads (e.g. 100 or
781	1000) to allow for extremely high load situations, but want to free	1181	1000) to allow for extremely high load situations, but want to free
782	resources under normal circumstances (1000 threads can easily	1182	resources under normal circumstances (1000 threads can easily
783	consume 30MB of RAM).	1183	consume 30MB of RAM).
784		1184
785	The default is probably ok in most situations, especially if thread	1185	The default is probably ok in most situations, especially if thread
786	creation is fast. If thread creation is very slow on your system you	1186	creation is fast. If thread creation is very slow on your system you
787	might want to use larger values.	1187	might want to use larger values.
788		1188
		1189	IO::AIO::idle_timeout $seconds
		1190	Sets the minimum idle timeout (default 10) after which worker
		1191	threads are allowed to exit. SEe "IO::AIO::max_idle".
		1192
789	$oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1193	IO::AIO::max_outstanding $maxreqs
		1194	Sets the maximum number of outstanding requests to $nreqs. If you do
		1195	queue up more than this number of requests, the next call to
		1196	"IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
		1197	"IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
		1198	no longer exceeded.
		1199
		1200	In other words, this setting does not enforce a queue limit, but can
		1201	be used to make poll functions block if the limit is exceeded.
		1202
790	This is a very bad function to use in interactive programs because	1203	This is a very bad function to use in interactive programs because
791	it blocks, and a bad way to reduce concurrency because it is	1204	it blocks, and a bad way to reduce concurrency because it is
792	inexact: Better use an "aio_group" together with a feed callback.	1205	inexact: Better use an "aio_group" together with a feed callback.
793		1206
794	Sets the maximum number of outstanding requests to $nreqs. If you to	1207	It's main use is in scripts without an event loop - when you want to
795	queue up more than this number of requests, the next call to the	1208	stat a lot of files, you can write somehting like this:
796	"poll_cb" (and "poll_some" and other functions calling "poll_cb")
797	function will block until the limit is no longer exceeded.
798		1209
799	The default value is very large, so there is no practical limit on	1210	IO::AIO::max_outstanding 32;
		1211
		1212	for my $path (...) {
		1213	aio_stat $path , ...;
		1214	IO::AIO::poll_cb;
		1215	}
		1216
		1217	IO::AIO::flush;
		1218
		1219	The call to "poll_cb" inside the loop will normally return
		1220	instantly, but as soon as more thna 32 reqeusts are in-flight, it
		1221	will block until some requests have been handled. This keeps the
		1222	loop from pushing a large number of "aio_stat" requests onto the
		1223	queue.
		1224
		1225	The default value for "max_outstanding" is very large, so there is
800	the number of outstanding requests.	1226	no practical limit on the number of outstanding requests.
801
802	You can still queue as many requests as you want. Therefore,
803	"max_oustsanding" is mainly useful in simple scripts (with low
804	values) or as a stop gap to shield against fatal memory overflow
805	(with large values).
806		1227
807	STATISTICAL INFORMATION	1228	STATISTICAL INFORMATION
808	IO::AIO::nreqs	1229	IO::AIO::nreqs
809	Returns the number of requests currently in the ready, execute or	1230	Returns the number of requests currently in the ready, execute or
810	pending states (i.e. for which their callback has not been invoked	1231	pending states (i.e. for which their callback has not been invoked
…		…
821		1242
822	IO::AIO::npending	1243	IO::AIO::npending
823	Returns the number of requests currently in the pending state	1244	Returns the number of requests currently in the pending state
824	(executed, but not yet processed by poll_cb).	1245	(executed, but not yet processed by poll_cb).
825		1246
		1247	MISCELLANEOUS FUNCTIONS
		1248	IO::AIO implements some functions that might be useful, but are not
		1249	asynchronous.
		1250
		1251	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1252	Calls the "eio_sendfile_sync" function, which is like
		1253	"aio_sendfile", but is blocking (this makes most sense if you know
		1254	the input data is likely cached already and the output filehandle is
		1255	set to non-blocking operations).
		1256
		1257	Returns the number of bytes copied, or -1 on error.
		1258
		1259	IO::AIO::fadvise $fh, $offset, $len, $advice
		1260	Simply calls the "posix_fadvise" function (see its manpage for
		1261	details). The following advice constants are avaiable:
		1262	"IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
		1263	"IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
		1264	"IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
		1265
		1266	On systems that do not implement "posix_fadvise", this function
		1267	returns ENOSYS, otherwise the return value of "posix_fadvise".
		1268
		1269	IO::AIO::madvise $scalar, $offset, $len, $advice
		1270	Simply calls the "posix_madvise" function (see its manpage for
		1271	details). The following advice constants are avaiable:
		1272	"IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
		1273	"IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
		1274	"IO::AIO::MADV_DONTNEED".
		1275
		1276	On systems that do not implement "posix_madvise", this function
		1277	returns ENOSYS, otherwise the return value of "posix_madvise".
		1278
		1279	IO::AIO::mprotect $scalar, $offset, $len, $protect
		1280	Simply calls the "mprotect" function on the preferably AIO::mmap'ed
		1281	$scalar (see its manpage for details). The following protect
		1282	constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
		1283	"IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
		1284
		1285	On systems that do not implement "mprotect", this function returns
		1286	ENOSYS, otherwise the return value of "mprotect".
		1287
		1288	IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1289	Memory-maps a file (or anonymous memory range) and attaches it to
		1290	the given $scalar, which will act like a string scalar.
		1291
		1292	The only operations allowed on the scalar are "substr"/"vec" that
		1293	don't change the string length, and most read-only operations such
		1294	as copying it or searching it with regexes and so on.
		1295
		1296	Anything else is unsafe and will, at best, result in memory leaks.
		1297
		1298	The memory map associated with the $scalar is automatically removed
		1299	when the $scalar is destroyed, or when the "IO::AIO::mmap" or
		1300	"IO::AIO::munmap" functions are called.
		1301
		1302	This calls the "mmap"(2) function internally. See your system's
		1303	manual page for details on the $length, $prot and $flags parameters.
		1304
		1305	The $length must be larger than zero and smaller than the actual
		1306	filesize.
		1307
		1308	$prot is a combination of "IO::AIO::PROT_NONE",
		1309	"IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
		1310	"IO::AIO::PROT_WRITE",
		1311
		1312	$flags can be a combination of "IO::AIO::MAP_SHARED" or
		1313	"IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
		1314	not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
		1315	(which is set to "MAP_ANON" if your system only provides this
		1316	constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
		1317	"IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
		1318	"IO::AIO::MAP_NONBLOCK"
		1319
		1320	If $fh is "undef", then a file descriptor of -1 is passed.
		1321
		1322	$offset is the offset from the start of the file - it generally must
		1323	be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
		1324
		1325	Example:
		1326
		1327	use Digest::MD5;
		1328	use IO::AIO;
		1329
		1330	open my $fh, "<verybigfile"
		1331	or die "$!";
		1332
		1333	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1334	or die "verybigfile: $!";
		1335
		1336	my $fast_md5 = md5 $data;
		1337
		1338	IO::AIO::munmap $scalar
		1339	Removes a previous mmap and undefines the $scalar.
		1340
		1341	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1342	Calls the "munlock" function, undoing the effects of a previous
		1343	"aio_mlock" call (see its description for details).
		1344
		1345	IO::AIO::munlockall
		1346	Calls the "munlockall" function.
		1347
		1348	On systems that do not implement "munlockall", this function returns
		1349	ENOSYS, otherwise the return value of "munlockall".
		1350
		1351	EVENT LOOP INTEGRATION
		1352	It is recommended to use AnyEvent::AIO to integrate IO::AIO
		1353	automatically into many event loops:
		1354
		1355	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1356	use AnyEvent::AIO;
		1357
		1358	You can also integrate IO::AIO manually into many event loops, here are
		1359	some examples of how to do this:
		1360
		1361	# EV integration
		1362	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1363
		1364	# Event integration
		1365	Event->io (fd => IO::AIO::poll_fileno,
		1366	poll => 'r',
		1367	cb => \&IO::AIO::poll_cb);
		1368
		1369	# Glib/Gtk2 integration
		1370	add_watch Glib::IO IO::AIO::poll_fileno,
		1371	in => sub { IO::AIO::poll_cb; 1 };
		1372
		1373	# Tk integration
		1374	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1375	readable => \&IO::AIO::poll_cb);
		1376
		1377	# Danga::Socket integration
		1378	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1379	\&IO::AIO::poll_cb);
		1380
826	FORK BEHAVIOUR	1381	FORK BEHAVIOUR
827	This module should do "the right thing" when the process using it forks:	1382	Usage of pthreads in a program changes the semantics of fork
		1383	considerably. Specifically, only async-safe functions can be called
		1384	after fork. Perl doesn't know about this, so in general, you cannot call
		1385	fork with defined behaviour in perl if pthreads are involved. IO::AIO
		1386	uses pthreads, so this applies, but many other extensions and (for
		1387	inexplicable reasons) perl itself often is linked against pthreads, so
		1388	this limitation applies to quite a lot of perls.
828		1389
829	Before the fork, IO::AIO enters a quiescent state where no requests can	1390	This module no longer tries to fight your OS, or POSIX. That means
830	be added in other threads and no results will be processed. After the	1391	IO::AIO only works in the process that loaded it. Forking is fully
831	fork the parent simply leaves the quiescent state and continues	1392	supported, but using IO::AIO in the child is not.
832	request/result processing, while the child frees the request/result
833	queue (so that the requests started before the fork will only be handled
834	in the parent). Threads will be started on demand until the limit set in
835	the parent process has been reached again.
836		1393
837	In short: the parent will, after a short pause, continue as if fork had	1394	You might get around by not using IO::AIO before (or after) forking.
838	not been called, while the child will act as if IO::AIO has not been	1395	You could also try to call the IO::AIO::reinit function in the child:
839	used yet.	1396
		1397	IO::AIO::reinit
		1398	Abondons all current requests and I/O threads and simply
		1399	reinitialises all data structures. This is not an operation
		1400	suppported by any standards, but happens to work on GNU/Linux and
		1401	some newer BSD systems.
		1402
		1403	The only reasonable use for this function is to call it after
		1404	forking, if "IO::AIO" was used in the parent. Calling it while
		1405	IO::AIO is active in the process will result in undefined behaviour.
		1406	Calling it at any time will also result in any undefined (by POSIX)
		1407	behaviour.
840		1408
841	MEMORY USAGE	1409	MEMORY USAGE
842	Per-request usage:	1410	Per-request usage:
843		1411
844	Each aio request uses - depending on your architecture - around 100-200	1412	Each aio request uses - depending on your architecture - around 100-200
845	bytes of memory. In addition, stat requests need a stat buffer (possibly	1413	bytes of memory. In addition, stat requests need a stat buffer (possibly
846	a few hundred bytes), readdir requires a result buffer and so on. Perl	1414	a few hundred bytes), readdir requires a result buffer and so on. Perl
847	scalars and other data passed into aio requests will also be locked and	1415	scalars and other data passed into aio requests will also be locked and
848	will consume memory till the request has entered the done state.	1416	will consume memory till the request has entered the done state.
849		1417
850	This is now awfully much, so queuing lots of requests is not usually a	1418	This is not awfully much, so queuing lots of requests is not usually a
851	problem.	1419	problem.
852		1420
853	Per-thread usage:	1421	Per-thread usage:
854		1422
855	In the execution phase, some aio requests require more memory for	1423	In the execution phase, some aio requests require more memory for
…		…
858		1426
859	KNOWN BUGS	1427	KNOWN BUGS
860	Known bugs will be fixed in the next release.	1428	Known bugs will be fixed in the next release.
861		1429
862	SEE ALSO	1430	SEE ALSO
863	Coro::AIO.	1431	AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
		1432	more natural syntax.
864		1433
865	AUTHOR	1434	AUTHOR
866	Marc Lehmann <schmorp@schmorp.de>	1435	Marc Lehmann <schmorp@schmorp.de>
867	http://home.schmorp.de/	1436	http://home.schmorp.de/
868		1437

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Comparing IO-AIO/README (file contents): Revision 1.20 by root, Tue Oct 31 00:45:41 2006 UTC vs. Revision 1.49 by root, Mon Jul 18 03:09:06 2011 UTC

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Comparing IO-AIO/README (file contents):
Revision 1.20 by root, Tue Oct 31 00:45:41 2006 UTC vs.
Revision 1.49 by root, Mon Jul 18 03:09:06 2011 UTC