[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 1.48 by root, Wed Jun 29 11:25:17 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_rename $srcpath, $dstpath, $callback->($status)
		174	aio_mkdir $pathname, $mode, $callback->($status)
		175	aio_rmdir $pathname, $callback->($status)
		176	aio_readdir $pathname, $callback->($entries)
		177	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		178	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		179	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		180	aio_load $path, $data, $callback->($status)
		181	aio_copy $srcpath, $dstpath, $callback->($status)
		182	aio_move $srcpath, $dstpath, $callback->($status)
		183	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		184	aio_rmtree $path, $callback->($status)
		185	aio_sync $callback->($status)
		186	aio_fsync $fh, $callback->($status)
		187	aio_fdatasync $fh, $callback->($status)
		188	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		189	aio_pathsync $path, $callback->($status)
		190	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		191	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		192	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		193	aio_mlockall $flags, $callback->($status)
		194	aio_group $callback->(...)
		195	aio_nop $callback->()
		196
		197	$prev_pri = aioreq_pri [$pri]
		198	aioreq_nice $pri_adjust
		199
		200	IO::AIO::poll_wait
		201	IO::AIO::poll_cb
		202	IO::AIO::poll
		203	IO::AIO::flush
		204	IO::AIO::max_poll_reqs $nreqs
		205	IO::AIO::max_poll_time $seconds
		206	IO::AIO::min_parallel $nthreads
		207	IO::AIO::max_parallel $nthreads
		208	IO::AIO::max_idle $nthreads
		209	IO::AIO::idle_timeout $seconds
		210	IO::AIO::max_outstanding $maxreqs
		211	IO::AIO::nreqs
		212	IO::AIO::nready
		213	IO::AIO::npending
		214
		215	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		216	IO::AIO::fadvise $fh, $offset, $len, $advice
		217	IO::AIO::madvise $scalar, $offset, $length, $advice
		218	IO::AIO::mprotect $scalar, $offset, $length, $protect
		219	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		220	IO::AIO::munlockall
		221
172	AIO REQUEST FUNCTIONS	222	AIO REQUEST FUNCTIONS
173	All the "aio_*" calls are more or less thin wrappers around the syscall	223	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	224	with the same name (sans "aio_"). The arguments are similar or
175	identical, and they all accept an additional (and optional) $callback	225	identical, and they all accept an additional (and optional) $callback
176	argument which must be a code reference. This code reference will get	226	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	227	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	228	error, unlike perl, which usually delivers "false") as its sole argument
179	argument when the given syscall has been executed asynchronously.	229	after the given syscall has been executed asynchronously.
180		230
181	All functions expecting a filehandle keep a copy of the filehandle	231	All functions expecting a filehandle keep a copy of the filehandle
182	internally until the request has finished.	232	internally until the request has finished.
183		233
184	All functions return request objects of type IO::AIO::REQ that allow	234	All functions return request objects of type IO::AIO::REQ that allow
…		…
197	the user environment, d) use Glib::filename_from_unicode on unicode	247	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	248	filenames or e) use something else to ensure your scalar has the correct
199	contents.	249	contents.
200		250
201	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	251	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
202	handles correctly wether it is set or not.	252	handles correctly whether it is set or not.
203		253
204	$prev_pri = aioreq_pri [$pri]	254	$prev_pri = aioreq_pri [$pri]
205	Returns the priority value that would be used for the next request	255	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.	256	and, if $pri is given, sets the priority for the next aio request.
207		257
…		…
241	They are the same as used by "sysopen".	291	They are the same as used by "sysopen".
242		292
243	Likewise, $mode specifies the mode of the newly created file, if it	293	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	294	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	295	"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).	296	create new files, and 0666 or 0777 if you do). Note that the $mode
		297	will be modified by the umask in effect then the request is being
		298	executed, so better never change the umask.
247		299
248	Example:	300	Example:
249		301
250	aio_open "/etc/passwd", O_RDONLY, 0, sub {	302	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
251	if ($_[0]) {	303	if ($_[0]) {
252	print "open successful, fh is $_[0]\n";	304	print "open successful, fh is $_[0]\n";
253	...	305	...
254	} else {	306	} else {
255	die "open failed: $!\n";	307	die "open failed: $!\n";
256	}	308	}
257	};	309	};
258		310
		311	In addition to all the common open modes/flags ("O_RDONLY",
		312	"O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
		313	"O_APPEND"), the following POSIX and non-POSIX constants are
		314	available (missing ones on your system are, as usual, 0):
		315
		316	"O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
		317	"O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
		318	"O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
		319
259	aio_close $fh, $callback->($status)	320	aio_close $fh, $callback->($status)
260	Asynchronously close a file and call the callback with the result	321	Asynchronously close a file and call the callback with the result
261	code. WARNING: although accepted, you should not pass in a perl	322	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		323
266	This is supposed to be a bug in the API, so that might change. It's	324	Unfortunately, you can't do this to perl. Perl insists very
267	therefore best to avoid this function.	325	strongly on closing the file descriptor associated with the
		326	filehandle itself.
		327
		328	Therefore, "aio_close" will not close the filehandle - instead it
		329	will use dup2 to overwrite the file descriptor with the write-end of
		330	a pipe (the pipe fd will be created on demand and will be cached).
		331
		332	Or in other words: the file descriptor will be closed, but it will
		333	not be free for reuse until the perl filehandle is closed.
268		334
269	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	335	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
270	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	336	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
271	Reads or writes "length" bytes from the specified "fh" and "offset"	337	Reads or writes $length bytes from or to the specified $fh and
272	into the scalar given by "data" and offset "dataoffset" and calls	338	$offset into the scalar given by $data and offset $dataoffset and
273	the callback without the actual number of bytes read (or -1 on	339	calls the callback without the actual number of bytes read (or -1 on
274	error, just like the syscall).	340	error, just like the syscall).
275		341
		342	"aio_read" will, like "sysread", shrink or grow the $data scalar to
		343	offset plus the actual number of bytes read.
		344
		345	If $offset is undefined, then the current file descriptor offset
		346	will be used (and updated), otherwise the file descriptor offset
		347	will not be changed by these calls.
		348
		349	If $length is undefined in "aio_write", use the remaining length of
		350	$data.
		351
		352	If $dataoffset is less than zero, it will be counted from the end of
		353	$data.
		354
276	The $data scalar MUST NOT be modified in any way while the request	355	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	356	is outstanding. Modifying it can result in segfaults or World War
278	necessary/optional hardware is installed).	357	III (if the necessary/optional hardware is installed).
279		358
280	Example: Read 15 bytes at offset 7 into scalar $buffer, starting at	359	Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
281	offset 0 within the scalar:	360	offset 0 within the scalar:
282		361
283	aio_read $fh, 7, 15, $buffer, 0, sub {	362	aio_read $fh, 7, 15, $buffer, 0, sub {
…		…
288	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	367	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	368	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	369	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	370	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	371	more than one "aio_sendfile" per $out_fh, as they will interfere
293	with each other.	372	with each other. The same $in_fh works fine though, as this function
		373	does not move or use the file offset of $in_fh.
294		374
		375	Please note that "aio_sendfile" can read more bytes from $in_fh than
		376	are written, and there is no way to find out how many more bytes
		377	have been read from "aio_sendfile" alone, as "aio_sendfile" only
		378	provides the number of bytes written to $out_fh. Only if the result
		379	value equals $length one can assume that $length bytes have been
		380	read.
		381
		382	Unlike with other "aio_" functions, it makes a lot of sense to use
		383	"aio_sendfile" on non-blocking sockets, as long as one end
		384	(typically the $in_fh) is a file - the file I/O will then be
		385	asynchronous, while the socket I/O will be non-blocking. Note,
		386	however, that you can run into a trap where "aio_sendfile" reads
		387	some data with readahead, then fails to write all data, and when the
		388	socket is ready the next time, the data in the cache is already
		389	lost, forcing "aio_sendfile" to again hit the disk. Explicit
		390	"aio_read" + "aio_write" let's you better control resource usage.
		391
295	This call tries to make use of a native "sendfile" syscall to	392	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	393	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.	394	to a socket, and $in_fh should refer to an mmap'able file.
298		395
299	If the native sendfile call fails or is not implemented, it will be	396	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	397	"EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
301	regardless of the limitations of the operating system.	398	"ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
		399	any type of filehandle regardless of the limitations of the
		400	operating system.
302		401
303	Please note, however, that "aio_sendfile" can read more bytes from	402	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	403	hacked together in a hurry to improve benchmark numbers) tend to be
305	bytes have been read from "aio_sendfile" alone, as "aio_sendfile"	404	rather buggy on many systems, this implementation tries to work
306	only provides the number of bytes written to $out_fh. Only if the	405	around some known bugs in Linux and FreeBSD kernels (probably
307	result value equals $length one can assume that $length bytes have	406	others, too), but that might fail, so you really really should check
308	been read.	407	the return value of "aio_sendfile" - fewre bytes than expected might
		408	have been transferred.
309		409
310	aio_readahead $fh,$offset,$length, $callback->($retval)	410	aio_readahead $fh,$offset,$length, $callback->($retval)
311	"aio_readahead" populates the page cache with data from a file so	411	"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	412	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	413	$offset argument specifies the starting point from which data is to
…		…
334	Currently, the stats are always 64-bit-stats, i.e. instead of	434	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	435	returning an error when stat'ing a large file, the results will be
336	silently truncated unless perl itself is compiled with large file	436	silently truncated unless perl itself is compiled with large file
337	support.	437	support.
338		438
		439	To help interpret the mode and dev/rdev stat values, IO::AIO offers
		440	the following constants and functions (if not implemented, the
		441	constants will be 0 and the functions will either "croak" or fall
		442	back on traditional behaviour).
		443
		444	"S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
		445	"S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
		446	"IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
		447
339	Example: Print the length of /etc/passwd:	448	Example: Print the length of /etc/passwd:
340		449
341	aio_stat "/etc/passwd", sub {	450	aio_stat "/etc/passwd", sub {
342	$_[0] and die "stat failed: $!";	451	$_[0] and die "stat failed: $!";
343	print "size is ", -s _, "\n";	452	print "size is ", -s _, "\n";
344	};	453	};
345		454
		455	aio_statvfs $fh_or_path, $callback->($statvfs)
		456	Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
		457	whether a file handle or path was passed.
		458
		459	On success, the callback is passed a hash reference with the
		460	following members: "bsize", "frsize", "blocks", "bfree", "bavail",
		461	"files", "ffree", "favail", "fsid", "flag" and "namemax". On
		462	failure, "undef" is passed.
		463
		464	The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
		465	and "ST_NOSUID".
		466
		467	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		468	their correct value when available, or to 0 on systems that do not
		469	support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
		470	"ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
		471	"ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
		472
		473	Example: stat "/wd" and dump out the data if successful.
		474
		475	aio_statvfs "/wd", sub {
		476	my $f = $_[0]
		477	or die "statvfs: $!";
		478
		479	use Data::Dumper;
		480	say Dumper $f;
		481	};
		482
		483	# result:
		484	{
		485	bsize => 1024,
		486	bfree => 4333064312,
		487	blocks => 10253828096,
		488	files => 2050765568,
		489	flag => 4096,
		490	favail => 2042092649,
		491	bavail => 4333064312,
		492	ffree => 2042092649,
		493	namemax => 255,
		494	frsize => 1024,
		495	fsid => 1810
		496	}
		497
		498	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		499	Works like perl's "utime" function (including the special case of
		500	$atime and $mtime being undef). Fractional times are supported if
		501	the underlying syscalls support them.
		502
		503	When called with a pathname, uses utimes(2) if available, otherwise
		504	utime(2). If called on a file descriptor, uses futimes(2) if
		505	available, otherwise returns ENOSYS, so this is not portable.
		506
		507	Examples:
		508
		509	# set atime and mtime to current time (basically touch(1)):
		510	aio_utime "path", undef, undef;
		511	# set atime to current time and mtime to beginning of the epoch:
		512	aio_utime "path", time, undef; # undef==0
		513
		514	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		515	Works like perl's "chown" function, except that "undef" for either
		516	$uid or $gid is being interpreted as "do not change" (but -1 can
		517	also be used).
		518
		519	Examples:
		520
		521	# same as "chown root path" in the shell:
		522	aio_chown "path", 0, -1;
		523	# same as above:
		524	aio_chown "path", 0, undef;
		525
		526	aio_truncate $fh_or_path, $offset, $callback->($status)
		527	Works like truncate(2) or ftruncate(2).
		528
		529	aio_chmod $fh_or_path, $mode, $callback->($status)
		530	Works like perl's "chmod" function.
		531
346	aio_unlink $pathname, $callback->($status)	532	aio_unlink $pathname, $callback->($status)
347	Asynchronously unlink (delete) a file and call the callback with the	533	Asynchronously unlink (delete) a file and call the callback with the
348	result code.	534	result code.
349		535
350	aio_mknod $path, $mode, $dev, $callback->($status)	536	aio_mknod $path, $mode, $dev, $callback->($status)
…		…
353	Asynchronously create a device node (or fifo). See mknod(2).	539	Asynchronously create a device node (or fifo). See mknod(2).
354		540
355	The only (POSIX-) portable way of calling this function is:	541	The only (POSIX-) portable way of calling this function is:
356		542
357	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...	543	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		544
		545	See "aio_stat" for info about some potentially helpful extra
		546	constants and functions.
358		547
359	aio_link $srcpath, $dstpath, $callback->($status)	548	aio_link $srcpath, $dstpath, $callback->($status)
360	Asynchronously create a new link to the existing object at $srcpath	549	Asynchronously create a new link to the existing object at $srcpath
361	at the path $dstpath and call the callback with the result code.	550	at the path $dstpath and call the callback with the result code.
362		551
…		…
372		561
373	aio_rename $srcpath, $dstpath, $callback->($status)	562	aio_rename $srcpath, $dstpath, $callback->($status)
374	Asynchronously rename the object at $srcpath to $dstpath, just as	563	Asynchronously rename the object at $srcpath to $dstpath, just as
375	rename(2) and call the callback with the result code.	564	rename(2) and call the callback with the result code.
376		565
		566	aio_mkdir $pathname, $mode, $callback->($status)
		567	Asynchronously mkdir (create) a directory and call the callback with
		568	the result code. $mode will be modified by the umask at the time the
		569	request is executed, so do not change your umask.
		570
377	aio_rmdir $pathname, $callback->($status)	571	aio_rmdir $pathname, $callback->($status)
378	Asynchronously rmdir (delete) a directory and call the callback with	572	Asynchronously rmdir (delete) a directory and call the callback with
379	the result code.	573	the result code.
380		574
381	aio_readdir $pathname, $callback->($entries)	575	aio_readdir $pathname, $callback->($entries)
382	Unlike the POSIX call of the same name, "aio_readdir" reads an	576	Unlike the POSIX call of the same name, "aio_readdir" reads an
383	entire directory (i.e. opendir + readdir + closedir). The entries	577	entire directory (i.e. opendir + readdir + closedir). The entries
384	will not be sorted, and will NOT include the "." and ".." entries.	578	will not be sorted, and will NOT include the "." and ".." entries.
385		579
386	The callback a single argument which is either "undef" or an	580	The callback is passed a single argument which is either "undef" or
387	array-ref with the filenames.	581	an array-ref with the filenames.
		582
		583	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		584	Quite similar to "aio_readdir", but the $flags argument allows to
		585	tune behaviour and output format. In case of an error, $entries will
		586	be "undef".
		587
		588	The flags are a combination of the following constants, ORed
		589	together (the flags will also be passed to the callback, possibly
		590	modified):
		591
		592	IO::AIO::READDIR_DENTS
		593	When this flag is off, then the callback gets an arrayref
		594	consisting of names only (as with "aio_readdir"), otherwise it
		595	gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
		596	describing a single directory entry in more detail.
		597
		598	$name is the name of the entry.
		599
		600	$type is one of the "IO::AIO::DT_xxx" constants:
		601
		602	"IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
		603	"IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
		604	"IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
		605
		606	"IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
		607	you need to know, you have to run stat yourself. Also, for speed
		608	reasons, the $type scalars are read-only: you can not modify
		609	them.
		610
		611	$inode is the inode number (which might not be exact on systems
		612	with 64 bit inode numbers and 32 bit perls). This field has
		613	unspecified content on systems that do not deliver the inode
		614	information.
		615
		616	IO::AIO::READDIR_DIRS_FIRST
		617	When this flag is set, then the names will be returned in an
		618	order where likely directories come first, in optimal stat
		619	order. This is useful when you need to quickly find directories,
		620	or you want to find all directories while avoiding to stat()
		621	each entry.
		622
		623	If the system returns type information in readdir, then this is
		624	used to find directories directly. Otherwise, likely directories
		625	are names beginning with ".", or otherwise names with no dots,
		626	of which names with short names are tried first.
		627
		628	IO::AIO::READDIR_STAT_ORDER
		629	When this flag is set, then the names will be returned in an
		630	order suitable for stat()'ing each one. That is, when you plan
		631	to stat() all files in the given directory, then the returned
		632	order will likely be fastest.
		633
		634	If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
		635	specified, then the likely dirs come first, resulting in a less
		636	optimal stat order.
		637
		638	IO::AIO::READDIR_FOUND_UNKNOWN
		639	This flag should not be set when calling "aio_readdirx".
		640	Instead, it is being set by "aio_readdirx", when any of the
		641	$type's found were "IO::AIO::DT_UNKNOWN". The absense of this
		642	flag therefore indicates that all $type's are known, which can
		643	be used to speed up some algorithms.
		644
		645	aio_load $path, $data, $callback->($status)
		646	This is a composite request that tries to fully load the given file
		647	into memory. Status is the same as with aio_read.
388		648
389	aio_copy $srcpath, $dstpath, $callback->($status)	649	aio_copy $srcpath, $dstpath, $callback->($status)
390	Try to copy the file (directories not supported as either source	650	Try to copy the file (directories not supported as either source
391	or destination) from $srcpath to $dstpath and call the callback with	651	or destination) from $srcpath to $dstpath and call the callback with
392	the 0 (error) or -1 ok.	652	a status of 0 (ok) or -1 (error, see $!).
393		653
394	This is a composite request that it creates the destination file	654	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	655	mode 0200 and copies the contents of the source file into it using
396	using "aio_sendfile", followed by restoring atime, mtime, access	656	"aio_sendfile", followed by restoring atime, mtime, access mode and
397	mode and uid/gid, in that order.	657	uid/gid, in that order.
398		658
399	If an error occurs, the partial destination file will be unlinked,	659	If an error occurs, the partial destination file will be unlinked,
400	if possible, except when setting atime, mtime, access mode and	660	if possible, except when setting atime, mtime, access mode and
401	uid/gid, where errors are being ignored.	661	uid/gid, where errors are being ignored.
402		662
403	aio_move $srcpath, $dstpath, $callback->($status)	663	aio_move $srcpath, $dstpath, $callback->($status)
404	Try to move the file (directories not supported as either source	664	Try to move the file (directories not supported as either source
405	or destination) from $srcpath to $dstpath and call the callback with	665	or destination) from $srcpath to $dstpath and call the callback with
406	the 0 (error) or -1 ok.	666	a status of 0 (ok) or -1 (error, see $!).
407		667
408	This is a composite request that tries to rename(2) the file first.	668	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"	669	if rename fails with "EXDEV", it copies the file with "aio_copy"
410	and, if that is successful, unlinking the $srcpath.	670	and, if that is successful, unlinks the $srcpath.
411		671
412	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	672	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
413	Scans a directory (similar to "aio_readdir") but additionally tries	673	Scans a directory (similar to "aio_readdir") but additionally tries
414	to efficiently separate the entries of directory $path into two sets	674	to efficiently separate the entries of directory $path into two sets
415	of names, directories you can recurse into (directories), and ones	675	of names, directories you can recurse into (directories), and ones
…		…
435	Implementation notes.	695	Implementation notes.
436		696
437	The "aio_readdir" cannot be avoided, but "stat()"'ing every entry	697	The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
438	can.	698	can.
439		699
		700	If readdir returns file type information, then this is used directly
		701	to find directories.
		702
440	After reading the directory, the modification time, size etc. of the	703	Otherwise, after reading the directory, the modification time, size
441	directory before and after the readdir is checked, and if they match	704	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	705	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	706	used to decide how many entries are directories (if >= 2).
444	of the number of subdirectories will be assumed.	707	Otherwise, no knowledge of the number of subdirectories will be
		708	assumed.
445		709
446	Then entries will be sorted into likely directories (everything	710	Then entries will be sorted into likely directories a non-initial
447	without a non-initial dot currently) and likely non-directories	711	dot currently) and likely non-directories (see "aio_readdirx"). Then
448	(everything else). Then every entry plus an appended "/." will be	712	every entry plus an appended "/." will be "stat"'ed, likely
449	"stat"'ed, likely directories first. If that succeeds, it assumes	713	directories first, in order of their inode numbers. If that
450	that the entry is a directory or a symlink to directory (which will	714	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	715	directory (which will be checked seperately). This is often faster
452	itself because filesystems might detect the type of the entry	716	than stat'ing the entry itself because filesystems might detect the
453	without reading the inode data (e.g. ext2fs filetype feature).	717	type of the entry without reading the inode data (e.g. ext2fs
		718	filetype feature), even on systems that cannot return the filetype
		719	information on readdir.
454		720
455	If the known number of directories (link count - 2) has been	721	If the known number of directories (link count - 2) has been
456	reached, the rest of the entries is assumed to be non-directories.	722	reached, the rest of the entries is assumed to be non-directories.
457		723
458	This only works with certainty on POSIX (= UNIX) filesystems, which	724	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
460		726
461	It will also likely work on non-POSIX filesystems with reduced	727	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	728	efficiency as those tend to return 0 or 1 as link counts, which
463	disables the directory counting heuristic.	729	disables the directory counting heuristic.
464		730
		731	aio_rmtree $path, $callback->($status)
		732	Delete a directory tree starting (and including) $path, return the
		733	status of the final "rmdir" only. This is a composite request that
		734	uses "aio_scandir" to recurse into and rmdir directories, and unlink
		735	everything else.
		736
		737	aio_sync $callback->($status)
		738	Asynchronously call sync and call the callback when finished.
		739
465	aio_fsync $fh, $callback->($status)	740	aio_fsync $fh, $callback->($status)
466	Asynchronously call fsync on the given filehandle and call the	741	Asynchronously call fsync on the given filehandle and call the
467	callback with the fsync result code.	742	callback with the fsync result code.
468		743
469	aio_fdatasync $fh, $callback->($status)	744	aio_fdatasync $fh, $callback->($status)
470	Asynchronously call fdatasync on the given filehandle and call the	745	Asynchronously call fdatasync on the given filehandle and call the
471	callback with the fdatasync result code.	746	callback with the fdatasync result code.
472		747
473	If this call isn't available because your OS lacks it or it couldn't	748	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.	749	be detected, it will be emulated by calling "fsync" instead.
		750
		751	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		752	Sync the data portion of the file specified by $offset and $length
		753	to disk (but NOT the metadata), by calling the Linux-specific
		754	sync_file_range call. If sync_file_range is not available or it
		755	returns ENOSYS, then fdatasync or fsync is being substituted.
		756
		757	$flags can be a combination of
		758	"IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
		759	"IO::AIO::SYNC_FILE_RANGE_WRITE" and
		760	"IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
		761	manpage for details.
		762
		763	aio_pathsync $path, $callback->($status)
		764	This request tries to open, fsync and close the given path. This is
		765	a composite request intended to sync directories after directory
		766	operations (E.g. rename). This might not work on all operating
		767	systems or have any specific effect, but usually it makes sure that
		768	directory changes get written to disc. It works for anything that
		769	can be opened for read-only, not just directories.
		770
		771	Future versions of this function might fall back to other methods
		772	when "fsync" on the directory fails (such as calling "sync").
		773
		774	Passes 0 when everything went ok, and -1 on error.
		775
		776	aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
		777	$callback->($status)
		778	This is a rather advanced IO::AIO call, which only works on
		779	mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
		780	also works on data scalars managed by the Sys::Mmap or Mmap modules,
		781	note that the scalar must only be modified in-place while an aio
		782	operation is pending on it).
		783
		784	It calls the "msync" function of your OS, if available, with the
		785	memory area starting at $offset in the string and ending $length
		786	bytes later. If $length is negative, counts from the end, and if
		787	$length is "undef", then it goes till the end of the string. The
		788	flags can be a combination of "IO::AIO::MS_ASYNC",
		789	"IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
		790
		791	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
		792	$callback->($status)
		793	This is a rather advanced IO::AIO call, which works best on
		794	mmap(2)ed scalars.
		795
		796	It touches (reads or writes) all memory pages in the specified range
		797	inside the scalar. All caveats and parameters are the same as for
		798	"aio_msync", above, except for flags, which must be either 0 (which
		799	reads all pages and ensures they are instantiated) or
		800	"IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
		801	and writing an octet from it, which dirties the page).
		802
		803	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		804	This is a rather advanced IO::AIO call, which works best on
		805	mmap(2)ed scalars.
		806
		807	It reads in all the pages of the underlying storage into memory (if
		808	any) and locks them, so they are not getting swapped/paged out or
		809	removed.
		810
		811	If $length is undefined, then the scalar will be locked till the
		812	end.
		813
		814	On systems that do not implement "mlock", this function returns -1
		815	and sets errno to "ENOSYS".
		816
		817	Note that the corresponding "munlock" is synchronous and is
		818	documented under "MISCELLANEOUS FUNCTIONS".
		819
		820	Example: open a file, mmap and mlock it - both will be undone when
		821	$data gets destroyed.
		822
		823	open my $fh, "<", $path or die "$path: $!";
		824	my $data;
		825	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		826	aio_mlock $data; # mlock in background
		827
		828	aio_mlockall $flags, $callback->($status)
		829	Calls the "mlockall" function with the given $flags (a combination
		830	of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
		831
		832	On systems that do not implement "mlockall", this function returns
		833	-1 and sets errno to "ENOSYS".
		834
		835	Note that the corresponding "munlockall" is synchronous and is
		836	documented under "MISCELLANEOUS FUNCTIONS".
		837
		838	Example: asynchronously lock all current and future pages into
		839	memory.
		840
		841	aio_mlockall IO::AIO::MCL_FUTURE;
475		842
476	aio_group $callback->(...)	843	aio_group $callback->(...)
477	This is a very special aio request: Instead of doing something, it	844	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	845	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	846	to bundle many requests into a single, composite, request with a
…		…
522		889
523	cancel $req	890	cancel $req
524	Cancels the request, if possible. Has the effect of skipping	891	Cancels the request, if possible. Has the effect of skipping
525	execution when entering the execute state and skipping calling the	892	execution when entering the execute state and skipping calling the
526	callback when entering the the result state, but will leave the	893	callback when entering the the result state, but will leave the
527	request otherwise untouched. That means that requests that currently	894	request otherwise untouched (with the exception of readdir). That
528	execute will not be stopped and resources held by the request will	895	means that requests that currently execute will not be stopped and
529	not be freed prematurely.	896	resources held by the request will not be freed prematurely.
530		897
531	cb $req $callback->(...)	898	cb $req $callback->(...)
532	Replace (or simply set) the callback registered to the request.	899	Replace (or simply set) the callback registered to the request.
533		900
534	IO::AIO::GRP CLASS	901	IO::AIO::GRP CLASS
…		…
561	};	928	};
562		929
563	This makes it very easy to create composite requests (see the source of	930	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.	931	"aio_move" for an application) that work and feel like simple requests.
565		932
566	* The IO::AIO::GRP objects will be cleaned up during calls to	933	* The IO::AIO::GRP objects will be cleaned up during calls to
567	"IO::AIO::poll_cb", just like any other request.	934	"IO::AIO::poll_cb", just like any other request.
		935
568	* They can be canceled like any other request. Canceling will cancel not	936	* They can be canceled like any other request. Canceling will cancel
569	only the request itself, but also all requests it contains.	937	not only the request itself, but also all requests it contains.
		938
570	* They can also can also be added to other IO::AIO::GRP objects.	939	* They can also can also be added to other IO::AIO::GRP objects.
		940
571	* You must not add requests to a group from within the group callback	941	* You must not add requests to a group from within the group callback
572	(or any later time).	942	(or any later time).
573		943
574	Their lifetime, simplified, looks like this: when they are empty, they	944	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	945	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	946	"done" state, they will also finish. Otherwise they will continue to
577	exist.	947	exist.
578		948
579	That means after creating a group you have some time to add requests.	949	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	950	(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	951	within the "poll_cb"). And in the callbacks of those requests, you can
582	group itself finish.	952	add further requests to the group. And only when all those requests have
		953	finished will the the group itself finish.
583		954
584	add $grp ...	955	add $grp ...
585	$grp->add (...)	956	$grp->add (...)
586	Add one or more requests to the group. Any type of IO::AIO::REQ can	957	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	958	be added, including other groups, as long as you do not create
…		…
592	$grp->cancel_subs	963	$grp->cancel_subs
593	Cancel all subrequests and clears any feeder, but not the group	964	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	965	request itself. Useful when you queued a lot of events but got a
595	result early.	966	result early.
596		967
		968	The group request will finish normally (you cannot add requests to
		969	the group).
		970
597	$grp->result (...)	971	$grp->result (...)
598	Set the result value(s) that will be passed to the group callback	972	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	973	when all subrequests have finished and set the groups errno to the
600	current value of errno (just like calling "errno" without an error	974	current value of errno (just like calling "errno" without an error
601	number). By default, no argument will be passed and errno is zero.	975	number). By default, no argument will be passed and errno is zero.
602		976
603	$grp->errno ([$errno])	977	$grp->errno ([$errno])
604	Sets the group errno value to $errno, or the current value of errno	978	Sets the group errno value to $errno, or the current value of errno
…		…
630	does not impose any limits).	1004	does not impose any limits).
631		1005
632	If the feed does not queue more requests when called, it will be	1006	If the feed does not queue more requests when called, it will be
633	automatically removed from the group.	1007	automatically removed from the group.
634		1008
635	If the feed limit is 0, it will be set to 2 automatically.	1009	If the feed limit is 0 when this method is called, it will be set to
		1010	2 automatically.
636		1011
637	Example:	1012	Example:
638		1013
639	# stat all files in @files, but only ever use four aio requests concurrently:	1014	# stat all files in @files, but only ever use four aio requests concurrently:
640		1015
…		…
651	Sets the feeder limit for the group: The feeder will be called	1026	Sets the feeder limit for the group: The feeder will be called
652	whenever the group contains less than this many requests.	1027	whenever the group contains less than this many requests.
653		1028
654	Setting the limit to 0 will pause the feeding process.	1029	Setting the limit to 0 will pause the feeding process.
655		1030
		1031	The default value for the limit is 0, but note that setting a feeder
		1032	automatically bumps it up to 2.
		1033
656	SUPPORT FUNCTIONS	1034	SUPPORT FUNCTIONS
657	EVENT PROCESSING AND EVENT LOOP INTEGRATION	1035	EVENT PROCESSING AND EVENT LOOP INTEGRATION
658	$fileno = IO::AIO::poll_fileno	1036	$fileno = IO::AIO::poll_fileno
659	Return the request result pipe file descriptor. This filehandle	1037	Return the request result pipe file descriptor. This filehandle
660	must be polled for reading by some mechanism outside this module	1038	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	1039	(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.	1040	pipe becomes readable you have to call "poll_cb" to check the
		1041	results.
663		1042
664	See "poll_cb" for an example.	1043	See "poll_cb" for an example.
665		1044
666	IO::AIO::poll_cb	1045	IO::AIO::poll_cb
667	Process some outstanding events on the result pipe. You have to call	1046	Process some outstanding events on the result pipe. You have to call
668	this regularly. Returns the number of events processed. Returns	1047	this regularly. Returns 0 if all events could be processed (or there
669	immediately when no events are outstanding. The amount of events	1048	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	1049	whatever reason. Returns immediately when no events are outstanding.
671	"IO::AIO::max_poll_time".	1050	The amount of events processed depends on the settings of
		1051	"IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
672		1052
673	If not all requests were processed for whatever reason, the	1053	If not all requests were processed for whatever reason, the
674	filehandle will still be ready when "poll_cb" returns.	1054	filehandle will still be ready when "poll_cb" returns, so normally
		1055	you don't have to do anything special to have it called later.
		1056
		1057	Apart from calling "IO::AIO::poll_cb" when the event filehandle
		1058	becomes ready, it can be beneficial to call this function from loops
		1059	which submit a lot of requests, to make sure the results get
		1060	processed when they become available and not just when the loop is
		1061	finished and the event loop takes over again. This function returns
		1062	very fast when there are no outstanding requests.
675		1063
676	Example: Install an Event watcher that automatically calls	1064	Example: Install an Event watcher that automatically calls
677	IO::AIO::poll_cb with high priority:	1065	IO::AIO::poll_cb with high priority (more examples can be found in
		1066	the SYNOPSIS section, at the top of this document):
678		1067
679	Event->io (fd => IO::AIO::poll_fileno,	1068	Event->io (fd => IO::AIO::poll_fileno,
680	poll => 'r', async => 1,	1069	poll => 'r', async => 1,
681	cb => \&IO::AIO::poll_cb);	1070	cb => \&IO::AIO::poll_cb);
		1071
		1072	IO::AIO::poll_wait
		1073	If there are any outstanding requests and none of them in the result
		1074	phase, wait till the result filehandle becomes ready for reading
		1075	(simply does a "select" on the filehandle. This is useful if you
		1076	want to synchronously wait for some requests to finish).
		1077
		1078	See "nreqs" for an example.
		1079
		1080	IO::AIO::poll
		1081	Waits until some requests have been handled.
		1082
		1083	Returns the number of requests processed, but is otherwise strictly
		1084	equivalent to:
		1085
		1086	IO::AIO::poll_wait, IO::AIO::poll_cb
		1087
		1088	IO::AIO::flush
		1089	Wait till all outstanding AIO requests have been handled.
		1090
		1091	Strictly equivalent to:
		1092
		1093	IO::AIO::poll_wait, IO::AIO::poll_cb
		1094	while IO::AIO::nreqs;
682		1095
683	IO::AIO::max_poll_reqs $nreqs	1096	IO::AIO::max_poll_reqs $nreqs
684	IO::AIO::max_poll_time $seconds	1097	IO::AIO::max_poll_time $seconds
685	These set the maximum number of requests (default 0, meaning	1098	These set the maximum number of requests (default 0, meaning
686	infinity) that are being processed by "IO::AIO::poll_cb" in one	1099	infinity) that are being processed by "IO::AIO::poll_cb" in one
…		…
710	# use a low priority so other tasks have priority	1123	# use a low priority so other tasks have priority
711	Event->io (fd => IO::AIO::poll_fileno,	1124	Event->io (fd => IO::AIO::poll_fileno,
712	poll => 'r', nice => 1,	1125	poll => 'r', nice => 1,
713	cb => &IO::AIO::poll_cb);	1126	cb => &IO::AIO::poll_cb);
714		1127
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	1128	CONTROLLING THE NUMBER OF THREADS
739	IO::AIO::min_parallel $nthreads	1129	IO::AIO::min_parallel $nthreads
740	Set the minimum number of AIO threads to $nthreads. The current	1130	Set the minimum number of AIO threads to $nthreads. The current
741	default is 8, which means eight asynchronous operations can execute	1131	default is 8, which means eight asynchronous operations can execute
742	concurrently at any one time (the number of outstanding requests,	1132	concurrently at any one time (the number of outstanding requests,
…		…
771		1161
772	Under normal circumstances you don't need to call this function.	1162	Under normal circumstances you don't need to call this function.
773		1163
774	IO::AIO::max_idle $nthreads	1164	IO::AIO::max_idle $nthreads
775	Limit the number of threads (default: 4) that are allowed to idle	1165	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	1166	(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	1167	timeout (default: 10 seconds). That means if a thread becomes idle
778	threads are also idle, it will free its resources and exit.	1168	while $nthreads other threads are also idle, it will free its
		1169	resources and exit.
779		1170
780	This is useful when you allow a large number of threads (e.g. 100 or	1171	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	1172	1000) to allow for extremely high load situations, but want to free
782	resources under normal circumstances (1000 threads can easily	1173	resources under normal circumstances (1000 threads can easily
783	consume 30MB of RAM).	1174	consume 30MB of RAM).
784		1175
785	The default is probably ok in most situations, especially if thread	1176	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	1177	creation is fast. If thread creation is very slow on your system you
787	might want to use larger values.	1178	might want to use larger values.
788		1179
		1180	IO::AIO::idle_timeout $seconds
		1181	Sets the minimum idle timeout (default 10) after which worker
		1182	threads are allowed to exit. SEe "IO::AIO::max_idle".
		1183
789	$oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1184	IO::AIO::max_outstanding $maxreqs
		1185	Sets the maximum number of outstanding requests to $nreqs. If you do
		1186	queue up more than this number of requests, the next call to
		1187	"IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
		1188	"IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
		1189	no longer exceeded.
		1190
		1191	In other words, this setting does not enforce a queue limit, but can
		1192	be used to make poll functions block if the limit is exceeded.
		1193
790	This is a very bad function to use in interactive programs because	1194	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	1195	it blocks, and a bad way to reduce concurrency because it is
792	inexact: Better use an "aio_group" together with a feed callback.	1196	inexact: Better use an "aio_group" together with a feed callback.
793		1197
794	Sets the maximum number of outstanding requests to $nreqs. If you to	1198	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	1199	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		1200
799	The default value is very large, so there is no practical limit on	1201	IO::AIO::max_outstanding 32;
		1202
		1203	for my $path (...) {
		1204	aio_stat $path , ...;
		1205	IO::AIO::poll_cb;
		1206	}
		1207
		1208	IO::AIO::flush;
		1209
		1210	The call to "poll_cb" inside the loop will normally return
		1211	instantly, but as soon as more thna 32 reqeusts are in-flight, it
		1212	will block until some requests have been handled. This keeps the
		1213	loop from pushing a large number of "aio_stat" requests onto the
		1214	queue.
		1215
		1216	The default value for "max_outstanding" is very large, so there is
800	the number of outstanding requests.	1217	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		1218
807	STATISTICAL INFORMATION	1219	STATISTICAL INFORMATION
808	IO::AIO::nreqs	1220	IO::AIO::nreqs
809	Returns the number of requests currently in the ready, execute or	1221	Returns the number of requests currently in the ready, execute or
810	pending states (i.e. for which their callback has not been invoked	1222	pending states (i.e. for which their callback has not been invoked
…		…
821		1233
822	IO::AIO::npending	1234	IO::AIO::npending
823	Returns the number of requests currently in the pending state	1235	Returns the number of requests currently in the pending state
824	(executed, but not yet processed by poll_cb).	1236	(executed, but not yet processed by poll_cb).
825		1237
		1238	MISCELLANEOUS FUNCTIONS
		1239	IO::AIO implements some functions that might be useful, but are not
		1240	asynchronous.
		1241
		1242	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1243	Calls the "eio_sendfile_sync" function, which is like
		1244	"aio_sendfile", but is blocking (this makes most sense if you know
		1245	the input data is likely cached already and the output filehandle is
		1246	set to non-blocking operations).
		1247
		1248	Returns the number of bytes copied, or -1 on error.
		1249
		1250	IO::AIO::fadvise $fh, $offset, $len, $advice
		1251	Simply calls the "posix_fadvise" function (see its manpage for
		1252	details). The following advice constants are avaiable:
		1253	"IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
		1254	"IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
		1255	"IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
		1256
		1257	On systems that do not implement "posix_fadvise", this function
		1258	returns ENOSYS, otherwise the return value of "posix_fadvise".
		1259
		1260	IO::AIO::madvise $scalar, $offset, $len, $advice
		1261	Simply calls the "posix_madvise" function (see its manpage for
		1262	details). The following advice constants are avaiable:
		1263	"IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
		1264	"IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
		1265	"IO::AIO::MADV_DONTNEED".
		1266
		1267	On systems that do not implement "posix_madvise", this function
		1268	returns ENOSYS, otherwise the return value of "posix_madvise".
		1269
		1270	IO::AIO::mprotect $scalar, $offset, $len, $protect
		1271	Simply calls the "mprotect" function on the preferably AIO::mmap'ed
		1272	$scalar (see its manpage for details). The following protect
		1273	constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
		1274	"IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
		1275
		1276	On systems that do not implement "mprotect", this function returns
		1277	ENOSYS, otherwise the return value of "mprotect".
		1278
		1279	IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1280	Memory-maps a file (or anonymous memory range) and attaches it to
		1281	the given $scalar, which will act like a string scalar.
		1282
		1283	The only operations allowed on the scalar are "substr"/"vec" that
		1284	don't change the string length, and most read-only operations such
		1285	as copying it or searching it with regexes and so on.
		1286
		1287	Anything else is unsafe and will, at best, result in memory leaks.
		1288
		1289	The memory map associated with the $scalar is automatically removed
		1290	when the $scalar is destroyed, or when the "IO::AIO::mmap" or
		1291	"IO::AIO::munmap" functions are called.
		1292
		1293	This calls the "mmap"(2) function internally. See your system's
		1294	manual page for details on the $length, $prot and $flags parameters.
		1295
		1296	The $length must be larger than zero and smaller than the actual
		1297	filesize.
		1298
		1299	$prot is a combination of "IO::AIO::PROT_NONE",
		1300	"IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
		1301	"IO::AIO::PROT_WRITE",
		1302
		1303	$flags can be a combination of "IO::AIO::MAP_SHARED" or
		1304	"IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
		1305	not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
		1306	(which is set to "MAP_ANON" if your system only provides this
		1307	constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
		1308	"IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
		1309	"IO::AIO::MAP_NONBLOCK"
		1310
		1311	If $fh is "undef", then a file descriptor of -1 is passed.
		1312
		1313	$offset is the offset from the start of the file - it generally must
		1314	be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
		1315
		1316	Example:
		1317
		1318	use Digest::MD5;
		1319	use IO::AIO;
		1320
		1321	open my $fh, "<verybigfile"
		1322	or die "$!";
		1323
		1324	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1325	or die "verybigfile: $!";
		1326
		1327	my $fast_md5 = md5 $data;
		1328
		1329	IO::AIO::munmap $scalar
		1330	Removes a previous mmap and undefines the $scalar.
		1331
		1332	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1333	Calls the "munlock" function, undoing the effects of a previous
		1334	"aio_mlock" call (see its description for details).
		1335
		1336	IO::AIO::munlockall
		1337	Calls the "munlockall" function.
		1338
		1339	On systems that do not implement "munlockall", this function returns
		1340	ENOSYS, otherwise the return value of "munlockall".
		1341
		1342	EVENT LOOP INTEGRATION
		1343	It is recommended to use AnyEvent::AIO to integrate IO::AIO
		1344	automatically into many event loops:
		1345
		1346	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1347	use AnyEvent::AIO;
		1348
		1349	You can also integrate IO::AIO manually into many event loops, here are
		1350	some examples of how to do this:
		1351
		1352	# EV integration
		1353	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1354
		1355	# Event integration
		1356	Event->io (fd => IO::AIO::poll_fileno,
		1357	poll => 'r',
		1358	cb => \&IO::AIO::poll_cb);
		1359
		1360	# Glib/Gtk2 integration
		1361	add_watch Glib::IO IO::AIO::poll_fileno,
		1362	in => sub { IO::AIO::poll_cb; 1 };
		1363
		1364	# Tk integration
		1365	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1366	readable => \&IO::AIO::poll_cb);
		1367
		1368	# Danga::Socket integration
		1369	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1370	\&IO::AIO::poll_cb);
		1371
826	FORK BEHAVIOUR	1372	FORK BEHAVIOUR
827	This module should do "the right thing" when the process using it forks:	1373	Usage of pthreads in a program changes the semantics of fork
		1374	considerably. Specifically, only async-safe functions can be called
		1375	after fork. Perl doesn't know about this, so in general, you cannot call
		1376	fork with defined behaviour in perl. IO::AIO uses pthreads, so this
		1377	applies, but many other extensions and (for inexplicable reasons) perl
		1378	itself often is linked against pthreads, so this limitation applies.
828		1379
829	Before the fork, IO::AIO enters a quiescent state where no requests can	1380	Some operating systems have extensions that allow safe use of fork, and
830	be added in other threads and no results will be processed. After the	1381	this module should do "the right thing" on those, and tries on others.
831	fork the parent simply leaves the quiescent state and continues	1382	At the time of this writing (2011) only GNU/Linux supports these
832	request/result processing, while the child frees the request/result	1383	extensions to POSIX.
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
837	In short: the parent will, after a short pause, continue as if fork had
838	not been called, while the child will act as if IO::AIO has not been
839	used yet.
840		1384
841	MEMORY USAGE	1385	MEMORY USAGE
842	Per-request usage:	1386	Per-request usage:
843		1387
844	Each aio request uses - depending on your architecture - around 100-200	1388	Each aio request uses - depending on your architecture - around 100-200
845	bytes of memory. In addition, stat requests need a stat buffer (possibly	1389	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	1390	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	1391	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.	1392	will consume memory till the request has entered the done state.
849		1393
850	This is now awfully much, so queuing lots of requests is not usually a	1394	This is not awfully much, so queuing lots of requests is not usually a
851	problem.	1395	problem.
852		1396
853	Per-thread usage:	1397	Per-thread usage:
854		1398
855	In the execution phase, some aio requests require more memory for	1399	In the execution phase, some aio requests require more memory for
…		…
858		1402
859	KNOWN BUGS	1403	KNOWN BUGS
860	Known bugs will be fixed in the next release.	1404	Known bugs will be fixed in the next release.
861		1405
862	SEE ALSO	1406	SEE ALSO
863	Coro::AIO.	1407	AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
		1408	more natural syntax.
864		1409
865	AUTHOR	1410	AUTHOR
866	Marc Lehmann <schmorp@schmorp.de>	1411	Marc Lehmann <schmorp@schmorp.de>
867	http://home.schmorp.de/	1412	http://home.schmorp.de/
868		1413

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Revision 1.48 by root, Wed Jun 29 11:25:17 2011 UTC