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

Comparing IO-AIO/README (file contents):
Revision 1.41 by root, Sat Jan 2 14:24:32 2010 UTC vs.
Revision 1.52 by root, Tue Apr 10 05:01:33 2012 UTC

…		…
2	IO::AIO - Asynchronous Input/Output	2	IO::AIO - Asynchronous Input/Output
3		3
4	SYNOPSIS	4	SYNOPSIS
5	use IO::AIO;	5	use IO::AIO;
6		6
7	aio_open "/etc/passwd", O_RDONLY, 0, sub {	7	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8	my $fh = shift	8	my $fh = shift
9	or die "/etc/passwd: $!";	9	or die "/etc/passwd: $!";
10	...	10	...
11	};	11	};
12		12
…		…
23	my $req = aio_unlink "/tmp/file", sub { };	23	my $req = aio_unlink "/tmp/file", sub { };
24	$req->cancel; # cancel request if still in queue	24	$req->cancel; # cancel request if still in queue
25		25
26	my $grp = aio_group sub { print "all stats done\n" };	26	my $grp = aio_group sub { print "all stats done\n" };
27	add $grp aio_stat "..." for ...;	27	add $grp aio_stat "..." for ...;
28
29	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
30	use AnyEvent::AIO;
31
32	# EV integration
33	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
34
35	# Event integration
36	Event->io (fd => IO::AIO::poll_fileno,
37	poll => 'r',
38	cb => \&IO::AIO::poll_cb);
39
40	# Glib/Gtk2 integration
41	add_watch Glib::IO IO::AIO::poll_fileno,
42	in => sub { IO::AIO::poll_cb; 1 };
43
44	# Tk integration
45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
46	readable => \&IO::AIO::poll_cb);
47
48	# Danga::Socket integration
49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
50	\&IO::AIO::poll_cb);
51		28
52	DESCRIPTION	29	DESCRIPTION
53	This module implements asynchronous I/O using whatever means your	30	This module implements asynchronous I/O using whatever means your
54	operating system supports. It is implemented as an interface to "libeio"	31	operating system supports. It is implemented as an interface to "libeio"
55	(<http://software.schmorp.de/pkg/libeio.html>).	32	(<http://software.schmorp.de/pkg/libeio.html>).
…		…
95		72
96	# register the IO::AIO callback with EV	73	# register the IO::AIO callback with EV
97	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;	74	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
98		75
99	# queue the request to open /etc/passwd	76	# queue the request to open /etc/passwd
100	aio_open "/etc/passwd", O_RDONLY, 0, sub {	77	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
101	my $fh = shift	78	my $fh = shift
102	or die "error while opening: $!";	79	or die "error while opening: $!";
103		80
104	# stat'ing filehandles is generally non-blocking	81	# stat'ing filehandles is generally non-blocking
105	my $size = -s $fh;	82	my $size = -s $fh;
…		…
168	anymore (except possibly for the Perl object, but its connection to	145	anymore (except possibly for the Perl object, but its connection to
169	the actual aio request is severed and calling its methods will	146	the actual aio request is severed and calling its methods will
170	either do nothing or result in a runtime error).	147	either do nothing or result in a runtime error).
171		148
172	FUNCTIONS	149	FUNCTIONS
173	AIO REQUEST FUNCTIONS	150	QUICK OVERVIEW
		151	This section simply lists the prototypes of the most important functions
		152	for quick reference. See the following sections for function-by-function
		153	documentation.
		154
		155	aio_wd $pathname, $callback->($wd)
		156	aio_open $pathname, $flags, $mode, $callback->($fh)
		157	aio_close $fh, $callback->($status)
		158	aio_seek $fh,$offset,$whence, $callback->($offs)
		159	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		160	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		161	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		162	aio_readahead $fh,$offset,$length, $callback->($retval)
		163	aio_stat $fh_or_path, $callback->($status)
		164	aio_lstat $fh, $callback->($status)
		165	aio_statvfs $fh_or_path, $callback->($statvfs)
		166	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		167	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		168	aio_chmod $fh_or_path, $mode, $callback->($status)
		169	aio_truncate $fh_or_path, $offset, $callback->($status)
		170	aio_unlink $pathname, $callback->($status)
		171	aio_mknod $pathname, $mode, $dev, $callback->($status)
		172	aio_link $srcpath, $dstpath, $callback->($status)
		173	aio_symlink $srcpath, $dstpath, $callback->($status)
		174	aio_readlink $pathname, $callback->($link)
		175	aio_realpath $pathname, $callback->($link)
		176	aio_rename $srcpath, $dstpath, $callback->($status)
		177	aio_mkdir $pathname, $mode, $callback->($status)
		178	aio_rmdir $pathname, $callback->($status)
		179	aio_readdir $pathname, $callback->($entries)
		180	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		181	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		182	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		183	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		184	aio_load $pathname, $data, $callback->($status)
		185	aio_copy $srcpath, $dstpath, $callback->($status)
		186	aio_move $srcpath, $dstpath, $callback->($status)
		187	aio_rmtree $pathname, $callback->($status)
		188	aio_sync $callback->($status)
		189	aio_syncfs $fh, $callback->($status)
		190	aio_fsync $fh, $callback->($status)
		191	aio_fdatasync $fh, $callback->($status)
		192	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		193	aio_pathsync $pathname, $callback->($status)
		194	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		195	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		196	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		197	aio_mlockall $flags, $callback->($status)
		198	aio_group $callback->(...)
		199	aio_nop $callback->()
		200
		201	$prev_pri = aioreq_pri [$pri]
		202	aioreq_nice $pri_adjust
		203
		204	IO::AIO::poll_wait
		205	IO::AIO::poll_cb
		206	IO::AIO::poll
		207	IO::AIO::flush
		208	IO::AIO::max_poll_reqs $nreqs
		209	IO::AIO::max_poll_time $seconds
		210	IO::AIO::min_parallel $nthreads
		211	IO::AIO::max_parallel $nthreads
		212	IO::AIO::max_idle $nthreads
		213	IO::AIO::idle_timeout $seconds
		214	IO::AIO::max_outstanding $maxreqs
		215	IO::AIO::nreqs
		216	IO::AIO::nready
		217	IO::AIO::npending
		218
		219	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		220	IO::AIO::fadvise $fh, $offset, $len, $advice
		221	IO::AIO::madvise $scalar, $offset, $length, $advice
		222	IO::AIO::mprotect $scalar, $offset, $length, $protect
		223	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		224	IO::AIO::munlockall
		225
		226	API NOTES
174	All the "aio_*" calls are more or less thin wrappers around the syscall	227	All the "aio_*" calls are more or less thin wrappers around the syscall
175	with the same name (sans "aio_"). The arguments are similar or	228	with the same name (sans "aio_"). The arguments are similar or
176	identical, and they all accept an additional (and optional) $callback	229	identical, and they all accept an additional (and optional) $callback
177	argument which must be a code reference. This code reference will get	230	argument which must be a code reference. This code reference will be
178	called with the syscall return code (e.g. most syscalls return -1 on
179	error, unlike perl, which usually delivers "false") as its sole argument
180	after the given syscall has been executed asynchronously.	231	called after the syscall has been executed in an asynchronous fashion.
		232	The results of the request will be passed as arguments to the callback
		233	(and, if an error occured, in $!) - for most requests the syscall return
		234	code (e.g. most syscalls return -1 on error, unlike perl, which usually
		235	delivers "false").
		236
		237	Some requests (such as "aio_readdir") pass the actual results and
		238	communicate failures by passing "undef".
181		239
182	All functions expecting a filehandle keep a copy of the filehandle	240	All functions expecting a filehandle keep a copy of the filehandle
183	internally until the request has finished.	241	internally until the request has finished.
184		242
185	All functions return request objects of type IO::AIO::REQ that allow	243	All functions return request objects of type IO::AIO::REQ that allow
186	further manipulation of those requests while they are in-flight.	244	further manipulation of those requests while they are in-flight.
187		245
188	The pathnames you pass to these routines must be absolute and encoded	246	The pathnames you pass to these routines should be absolute. The
189	as octets. The reason for the former is that at the time the request is	247	reason for this is that at the time the request is being executed, the
190	being executed, the current working directory could have changed.	248	current working directory could have changed. Alternatively, you can
191	Alternatively, you can make sure that you never change the current	249	make sure that you never change the current working directory anywhere
192	working directory anywhere in the program and then use relative paths.	250	in the program and then use relative paths. You can also take advantage
		251	of IO::AIOs working directory abstraction, that lets you specify paths
		252	relative to some previously-opened "working directory object" - see the
		253	description of the "IO::AIO::WD" class later in this document.
193		254
194	To encode pathnames as octets, either make sure you either: a) always	255	To encode pathnames as octets, either make sure you either: a) always
195	pass in filenames you got from outside (command line, readdir etc.)	256	pass in filenames you got from outside (command line, readdir etc.)
196	without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module	257	without tinkering, b) are in your native filesystem encoding, c) use the
197	and encode your pathnames to the locale (or other) encoding in effect in	258	Encode module and encode your pathnames to the locale (or other)
198	the user environment, d) use Glib::filename_from_unicode on unicode	259	encoding in effect in the user environment, d) use
199	filenames or e) use something else to ensure your scalar has the correct	260	Glib::filename_from_unicode on unicode filenames or e) use something
200	contents.	261	else to ensure your scalar has the correct contents.
201		262
202	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	263	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203	handles correctly whether it is set or not.	264	handles correctly whether it is set or not.
204		265
		266	AIO REQUEST FUNCTIONS
205	$prev_pri = aioreq_pri [$pri]	267	$prev_pri = aioreq_pri [$pri]
206	Returns the priority value that would be used for the next request	268	Returns the priority value that would be used for the next request
207	and, if $pri is given, sets the priority for the next aio request.	269	and, if $pri is given, sets the priority for the next aio request.
208		270
209	The default priority is 0, the minimum and maximum priorities are -4	271	The default priority is 0, the minimum and maximum priorities are -4
…		…
248	will be modified by the umask in effect then the request is being	310	will be modified by the umask in effect then the request is being
249	executed, so better never change the umask.	311	executed, so better never change the umask.
250		312
251	Example:	313	Example:
252		314
253	aio_open "/etc/passwd", O_RDONLY, 0, sub {	315	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
254	if ($_[0]) {	316	if ($_[0]) {
255	print "open successful, fh is $_[0]\n";	317	print "open successful, fh is $_[0]\n";
256	...	318	...
257	} else {	319	} else {
258	die "open failed: $!\n";	320	die "open failed: $!\n";
259	}	321	}
260	};	322	};
261		323
		324	In addition to all the common open modes/flags ("O_RDONLY",
		325	"O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
		326	"O_APPEND"), the following POSIX and non-POSIX constants are
		327	available (missing ones on your system are, as usual, 0):
		328
		329	"O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
		330	"O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
		331	"O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
		332
262	aio_close $fh, $callback->($status)	333	aio_close $fh, $callback->($status)
263	Asynchronously close a file and call the callback with the result	334	Asynchronously close a file and call the callback with the result
264	code.	335	code.
265		336
266	Unfortunately, you can't do this to perl. Perl insists very	337	Unfortunately, you can't do this to perl. Perl insists very
…		…
271	will use dup2 to overwrite the file descriptor with the write-end of	342	will use dup2 to overwrite the file descriptor with the write-end of
272	a pipe (the pipe fd will be created on demand and will be cached).	343	a pipe (the pipe fd will be created on demand and will be cached).
273		344
274	Or in other words: the file descriptor will be closed, but it will	345	Or in other words: the file descriptor will be closed, but it will
275	not be free for reuse until the perl filehandle is closed.	346	not be free for reuse until the perl filehandle is closed.
		347
		348	aio_seek $fh, $offset, $whence, $callback->($offs)
		349	Seeks the filehandle to the new $offset, similarly to perl's
		350	"sysseek". The $whence can use the traditional values (0 for
		351	"IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
		352	"IO::AIO::SEEK_END").
		353
		354	The resulting absolute offset will be passed to the callback, or -1
		355	in case of an error.
		356
		357	In theory, the $whence constants could be different than the
		358	corresponding values from Fcntl, but perl guarantees they are the
		359	same, so don't panic.
		360
		361	As a GNU/Linux (and maybe Solaris) extension, also the constants
		362	"IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
		363	could be found. No guarantees about suitability for use in
		364	"aio_seek" or Perl's "sysseek" can be made though, although I would
		365	naively assume they "just work".
276		366
277	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	367	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
278	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	368	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
279	Reads or writes $length bytes from or to the specified $fh and	369	Reads or writes $length bytes from or to the specified $fh and
280	$offset into the scalar given by $data and offset $dataoffset and	370	$offset into the scalar given by $data and offset $dataoffset and
…		…
309	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	399	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
310	Tries to copy $length bytes from $in_fh to $out_fh. It starts	400	Tries to copy $length bytes from $in_fh to $out_fh. It starts
311	reading at byte offset $in_offset, and starts writing at the current	401	reading at byte offset $in_offset, and starts writing at the current
312	file offset of $out_fh. Because of that, it is not safe to issue	402	file offset of $out_fh. Because of that, it is not safe to issue
313	more than one "aio_sendfile" per $out_fh, as they will interfere	403	more than one "aio_sendfile" per $out_fh, as they will interfere
314	with each other.	404	with each other. The same $in_fh works fine though, as this function
		405	does not move or use the file offset of $in_fh.
315		406
		407	Please note that "aio_sendfile" can read more bytes from $in_fh than
		408	are written, and there is no way to find out how many more bytes
		409	have been read from "aio_sendfile" alone, as "aio_sendfile" only
		410	provides the number of bytes written to $out_fh. Only if the result
		411	value equals $length one can assume that $length bytes have been
		412	read.
		413
		414	Unlike with other "aio_" functions, it makes a lot of sense to use
		415	"aio_sendfile" on non-blocking sockets, as long as one end
		416	(typically the $in_fh) is a file - the file I/O will then be
		417	asynchronous, while the socket I/O will be non-blocking. Note,
		418	however, that you can run into a trap where "aio_sendfile" reads
		419	some data with readahead, then fails to write all data, and when the
		420	socket is ready the next time, the data in the cache is already
		421	lost, forcing "aio_sendfile" to again hit the disk. Explicit
		422	"aio_read" + "aio_write" let's you better control resource usage.
		423
316	This call tries to make use of a native "sendfile" syscall to	424	This call tries to make use of a native "sendfile"-like syscall to
317	provide zero-copy operation. For this to work, $out_fh should refer	425	provide zero-copy operation. For this to work, $out_fh should refer
318	to a socket, and $in_fh should refer to mmap'able file.	426	to a socket, and $in_fh should refer to an mmap'able file.
319		427
320	If a native sendfile cannot be found or it fails with "ENOSYS",	428	If a native sendfile cannot be found or it fails with "ENOSYS",
321	"ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK",	429	"EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
322	it will be emulated, so you can call "aio_sendfile" on any type of	430	"ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
323	filehandle regardless of the limitations of the operating system.	431	any type of filehandle regardless of the limitations of the
		432	operating system.
324		433
325	Please note, however, that "aio_sendfile" can read more bytes from	434	As native sendfile syscalls (as practically any non-POSIX interface
326	$in_fh than are written, and there is no way to find out how many	435	hacked together in a hurry to improve benchmark numbers) tend to be
327	bytes have been read from "aio_sendfile" alone, as "aio_sendfile"	436	rather buggy on many systems, this implementation tries to work
328	only provides the number of bytes written to $out_fh. Only if the	437	around some known bugs in Linux and FreeBSD kernels (probably
329	result value equals $length one can assume that $length bytes have	438	others, too), but that might fail, so you really really should check
330	been read.	439	the return value of "aio_sendfile" - fewre bytes than expected might
		440	have been transferred.
331		441
332	aio_readahead $fh,$offset,$length, $callback->($retval)	442	aio_readahead $fh,$offset,$length, $callback->($retval)
333	"aio_readahead" populates the page cache with data from a file so	443	"aio_readahead" populates the page cache with data from a file so
334	that subsequent reads from that file will not block on disk I/O. The	444	that subsequent reads from that file will not block on disk I/O. The
335	$offset argument specifies the starting point from which data is to	445	$offset argument specifies the starting point from which data is to
…		…
356	Currently, the stats are always 64-bit-stats, i.e. instead of	466	Currently, the stats are always 64-bit-stats, i.e. instead of
357	returning an error when stat'ing a large file, the results will be	467	returning an error when stat'ing a large file, the results will be
358	silently truncated unless perl itself is compiled with large file	468	silently truncated unless perl itself is compiled with large file
359	support.	469	support.
360		470
		471	To help interpret the mode and dev/rdev stat values, IO::AIO offers
		472	the following constants and functions (if not implemented, the
		473	constants will be 0 and the functions will either "croak" or fall
		474	back on traditional behaviour).
		475
		476	"S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
		477	"S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
		478	"IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
		479
361	Example: Print the length of /etc/passwd:	480	Example: Print the length of /etc/passwd:
362		481
363	aio_stat "/etc/passwd", sub {	482	aio_stat "/etc/passwd", sub {
364	$_[0] and die "stat failed: $!";	483	$_[0] and die "stat failed: $!";
365	print "size is ", -s _, "\n";	484	print "size is ", -s _, "\n";
366	};	485	};
367		486
		487	aio_statvfs $fh_or_path, $callback->($statvfs)
		488	Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
		489	whether a file handle or path was passed.
		490
		491	On success, the callback is passed a hash reference with the
		492	following members: "bsize", "frsize", "blocks", "bfree", "bavail",
		493	"files", "ffree", "favail", "fsid", "flag" and "namemax". On
		494	failure, "undef" is passed.
		495
		496	The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
		497	and "ST_NOSUID".
		498
		499	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		500	their correct value when available, or to 0 on systems that do not
		501	support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
		502	"ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
		503	"ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
		504
		505	Example: stat "/wd" and dump out the data if successful.
		506
		507	aio_statvfs "/wd", sub {
		508	my $f = $_[0]
		509	or die "statvfs: $!";
		510
		511	use Data::Dumper;
		512	say Dumper $f;
		513	};
		514
		515	# result:
		516	{
		517	bsize => 1024,
		518	bfree => 4333064312,
		519	blocks => 10253828096,
		520	files => 2050765568,
		521	flag => 4096,
		522	favail => 2042092649,
		523	bavail => 4333064312,
		524	ffree => 2042092649,
		525	namemax => 255,
		526	frsize => 1024,
		527	fsid => 1810
		528	}
		529
368	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	530	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
369	Works like perl's "utime" function (including the special case of	531	Works like perl's "utime" function (including the special case of
370	$atime and $mtime being undef). Fractional times are supported if	532	$atime and $mtime being undef). Fractional times are supported if
371	the underlying syscalls support them.	533	the underlying syscalls support them.
372		534
…		…
401		563
402	aio_unlink $pathname, $callback->($status)	564	aio_unlink $pathname, $callback->($status)
403	Asynchronously unlink (delete) a file and call the callback with the	565	Asynchronously unlink (delete) a file and call the callback with the
404	result code.	566	result code.
405		567
406	aio_mknod $path, $mode, $dev, $callback->($status)	568	aio_mknod $pathname, $mode, $dev, $callback->($status)
407	[EXPERIMENTAL]	569	[EXPERIMENTAL]
408		570
409	Asynchronously create a device node (or fifo). See mknod(2).	571	Asynchronously create a device node (or fifo). See mknod(2).
410		572
411	The only (POSIX-) portable way of calling this function is:	573	The only (POSIX-) portable way of calling this function is:
412		574
413	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...	575	aio_mknod $pathname, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		576
		577	See "aio_stat" for info about some potentially helpful extra
		578	constants and functions.
414		579
415	aio_link $srcpath, $dstpath, $callback->($status)	580	aio_link $srcpath, $dstpath, $callback->($status)
416	Asynchronously create a new link to the existing object at $srcpath	581	Asynchronously create a new link to the existing object at $srcpath
417	at the path $dstpath and call the callback with the result code.	582	at the path $dstpath and call the callback with the result code.
418		583
419	aio_symlink $srcpath, $dstpath, $callback->($status)	584	aio_symlink $srcpath, $dstpath, $callback->($status)
420	Asynchronously create a new symbolic link to the existing object at	585	Asynchronously create a new symbolic link to the existing object at
421	$srcpath at the path $dstpath and call the callback with the result	586	$srcpath at the path $dstpath and call the callback with the result
422	code.	587	code.
423		588
424	aio_readlink $path, $callback->($link)	589	aio_readlink $pathname, $callback->($link)
425	Asynchronously read the symlink specified by $path and pass it to	590	Asynchronously read the symlink specified by $path and pass it to
426	the callback. If an error occurs, nothing or undef gets passed to	591	the callback. If an error occurs, nothing or undef gets passed to
427	the callback.	592	the callback.
		593
		594	aio_realpath $pathname, $callback->($path)
		595	Asynchronously make the path absolute and resolve any symlinks in
		596	$path. The resulting path only consists of directories (Same as
		597	Cwd::realpath).
		598
		599	This request can be used to get the absolute path of the current
		600	working directory by passing it a path of . (a single dot).
428		601
429	aio_rename $srcpath, $dstpath, $callback->($status)	602	aio_rename $srcpath, $dstpath, $callback->($status)
430	Asynchronously rename the object at $srcpath to $dstpath, just as	603	Asynchronously rename the object at $srcpath to $dstpath, just as
431	rename(2) and call the callback with the result code.	604	rename(2) and call the callback with the result code.
432		605
…		…
446		619
447	The callback is passed a single argument which is either "undef" or	620	The callback is passed a single argument which is either "undef" or
448	an array-ref with the filenames.	621	an array-ref with the filenames.
449		622
450	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	623	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
451	Quite similar to "aio_readdir", but the $flags argument allows to	624	Quite similar to "aio_readdir", but the $flags argument allows one
452	tune behaviour and output format. In case of an error, $entries will	625	to tune behaviour and output format. In case of an error, $entries
453	be "undef".	626	will be "undef".
454		627
455	The flags are a combination of the following constants, ORed	628	The flags are a combination of the following constants, ORed
456	together (the flags will also be passed to the callback, possibly	629	together (the flags will also be passed to the callback, possibly
457	modified):	630	modified):
458		631
459	IO::AIO::READDIR_DENTS	632	IO::AIO::READDIR_DENTS
460	When this flag is off, then the callback gets an arrayref with	633	When this flag is off, then the callback gets an arrayref
461	of names only (as with "aio_readdir"), otherwise it gets an	634	consisting of names only (as with "aio_readdir"), otherwise it
462	arrayref with "[$name, $type, $inode]" arrayrefs, each	635	gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
463	describing a single directory entry in more detail.	636	describing a single directory entry in more detail.
464		637
465	$name is the name of the entry.	638	$name is the name of the entry.
466		639
467	$type is one of the "IO::AIO::DT_xxx" constants:	640	$type is one of the "IO::AIO::DT_xxx" constants:
…		…
480	unspecified content on systems that do not deliver the inode	653	unspecified content on systems that do not deliver the inode
481	information.	654	information.
482		655
483	IO::AIO::READDIR_DIRS_FIRST	656	IO::AIO::READDIR_DIRS_FIRST
484	When this flag is set, then the names will be returned in an	657	When this flag is set, then the names will be returned in an
485	order where likely directories come first. This is useful when	658	order where likely directories come first, in optimal stat
486	you need to quickly find directories, or you want to find all	659	order. This is useful when you need to quickly find directories,
487	directories while avoiding to stat() each entry.	660	or you want to find all directories while avoiding to stat()
		661	each entry.
488		662
489	If the system returns type information in readdir, then this is	663	If the system returns type information in readdir, then this is
490	used to find directories directly. Otherwise, likely directories	664	used to find directories directly. Otherwise, likely directories
491	are files beginning with ".", or otherwise files with no dots,	665	are names beginning with ".", or otherwise names with no dots,
492	of which files with short names are tried first.	666	of which names with short names are tried first.
493		667
494	IO::AIO::READDIR_STAT_ORDER	668	IO::AIO::READDIR_STAT_ORDER
495	When this flag is set, then the names will be returned in an	669	When this flag is set, then the names will be returned in an
496	order suitable for stat()'ing each one. That is, when you plan	670	order suitable for stat()'ing each one. That is, when you plan
497	to stat() all files in the given directory, then the returned	671	to stat() all files in the given directory, then the returned
…		…
502	optimal stat order.	676	optimal stat order.
503		677
504	IO::AIO::READDIR_FOUND_UNKNOWN	678	IO::AIO::READDIR_FOUND_UNKNOWN
505	This flag should not be set when calling "aio_readdirx".	679	This flag should not be set when calling "aio_readdirx".
506	Instead, it is being set by "aio_readdirx", when any of the	680	Instead, it is being set by "aio_readdirx", when any of the
507	$type's found were "IO::AIO::DT_UNKNOWN". The absense of this	681	$type's found were "IO::AIO::DT_UNKNOWN". The absence of this
508	flag therefore indicates that all $type's are known, which can	682	flag therefore indicates that all $type's are known, which can
509	be used to speed up some algorithms.	683	be used to speed up some algorithms.
510		684
511	aio_load $path, $data, $callback->($status)	685	aio_load $pathname, $data, $callback->($status)
512	This is a composite request that tries to fully load the given file	686	This is a composite request that tries to fully load the given file
513	into memory. Status is the same as with aio_read.	687	into memory. Status is the same as with aio_read.
514		688
515	aio_copy $srcpath, $dstpath, $callback->($status)	689	aio_copy $srcpath, $dstpath, $callback->($status)
516	Try to copy the file (directories not supported as either source	690	Try to copy the file (directories not supported as either source
…		…
533		707
534	This is a composite request that tries to rename(2) the file first;	708	This is a composite request that tries to rename(2) the file first;
535	if rename fails with "EXDEV", it copies the file with "aio_copy"	709	if rename fails with "EXDEV", it copies the file with "aio_copy"
536	and, if that is successful, unlinks the $srcpath.	710	and, if that is successful, unlinks the $srcpath.
537		711
538	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	712	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
539	Scans a directory (similar to "aio_readdir") but additionally tries	713	Scans a directory (similar to "aio_readdir") but additionally tries
540	to efficiently separate the entries of directory $path into two sets	714	to efficiently separate the entries of directory $path into two sets
541	of names, directories you can recurse into (directories), and ones	715	of names, directories you can recurse into (directories), and ones
542	you cannot recurse into (everything else, including symlinks to	716	you cannot recurse into (everything else, including symlinks to
543	directories).	717	directories).
…		…
576	Then entries will be sorted into likely directories a non-initial	750	Then entries will be sorted into likely directories a non-initial
577	dot currently) and likely non-directories (see "aio_readdirx"). Then	751	dot currently) and likely non-directories (see "aio_readdirx"). Then
578	every entry plus an appended "/." will be "stat"'ed, likely	752	every entry plus an appended "/." will be "stat"'ed, likely
579	directories first, in order of their inode numbers. If that	753	directories first, in order of their inode numbers. If that
580	succeeds, it assumes that the entry is a directory or a symlink to	754	succeeds, it assumes that the entry is a directory or a symlink to
581	directory (which will be checked seperately). This is often faster	755	directory (which will be checked separately). This is often faster
582	than stat'ing the entry itself because filesystems might detect the	756	than stat'ing the entry itself because filesystems might detect the
583	type of the entry without reading the inode data (e.g. ext2fs	757	type of the entry without reading the inode data (e.g. ext2fs
584	filetype feature), even on systems that cannot return the filetype	758	filetype feature), even on systems that cannot return the filetype
585	information on readdir.	759	information on readdir.
586		760
…		…
592		766
593	It will also likely work on non-POSIX filesystems with reduced	767	It will also likely work on non-POSIX filesystems with reduced
594	efficiency as those tend to return 0 or 1 as link counts, which	768	efficiency as those tend to return 0 or 1 as link counts, which
595	disables the directory counting heuristic.	769	disables the directory counting heuristic.
596		770
597	aio_rmtree $path, $callback->($status)	771	aio_rmtree $pathname, $callback->($status)
598	Delete a directory tree starting (and including) $path, return the	772	Delete a directory tree starting (and including) $path, return the
599	status of the final "rmdir" only. This is a composite request that	773	status of the final "rmdir" only. This is a composite request that
600	uses "aio_scandir" to recurse into and rmdir directories, and unlink	774	uses "aio_scandir" to recurse into and rmdir directories, and unlink
601	everything else.	775	everything else.
602		776
…		…
611	Asynchronously call fdatasync on the given filehandle and call the	785	Asynchronously call fdatasync on the given filehandle and call the
612	callback with the fdatasync result code.	786	callback with the fdatasync result code.
613		787
614	If this call isn't available because your OS lacks it or it couldn't	788	If this call isn't available because your OS lacks it or it couldn't
615	be detected, it will be emulated by calling "fsync" instead.	789	be detected, it will be emulated by calling "fsync" instead.
		790
		791	aio_syncfs $fh, $callback->($status)
		792	Asynchronously call the syncfs syscall to sync the filesystem
		793	associated to the given filehandle and call the callback with the
		794	syncfs result code. If syncfs is not available, calls sync(), but
		795	returns -1 and sets errno to "ENOSYS" nevertheless.
616		796
617	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	797	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
618	Sync the data portion of the file specified by $offset and $length	798	Sync the data portion of the file specified by $offset and $length
619	to disk (but NOT the metadata), by calling the Linux-specific	799	to disk (but NOT the metadata), by calling the Linux-specific
620	sync_file_range call. If sync_file_range is not available or it	800	sync_file_range call. If sync_file_range is not available or it
…		…
624	"IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",	804	"IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
625	"IO::AIO::SYNC_FILE_RANGE_WRITE" and	805	"IO::AIO::SYNC_FILE_RANGE_WRITE" and
626	"IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range	806	"IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
627	manpage for details.	807	manpage for details.
628		808
629	aio_pathsync $path, $callback->($status)	809	aio_pathsync $pathname, $callback->($status)
630	This request tries to open, fsync and close the given path. This is	810	This request tries to open, fsync and close the given path. This is
631	a composite request intended to sync directories after directory	811	a composite request intended to sync directories after directory
632	operations (E.g. rename). This might not work on all operating	812	operations (E.g. rename). This might not work on all operating
633	systems or have any specific effect, but usually it makes sure that	813	systems or have any specific effect, but usually it makes sure that
634	directory changes get written to disc. It works for anything that	814	directory changes get written to disc. It works for anything that
…		…
640	Passes 0 when everything went ok, and -1 on error.	820	Passes 0 when everything went ok, and -1 on error.
641		821
642	aio_msync $scalar, $offset = 0, $length = undef, flags = 0,	822	aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
643	$callback->($status)	823	$callback->($status)
644	This is a rather advanced IO::AIO call, which only works on	824	This is a rather advanced IO::AIO call, which only works on
645	mmap(2)ed scalars (see the Sys::Mmap or Mmap modules for details on	825	mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
		826	also works on data scalars managed by the Sys::Mmap or Mmap modules,
646	this, note that the scalar must only be modified in-place while an	827	note that the scalar must only be modified in-place while an aio
647	aio operation is pending on it).	828	operation is pending on it).
648		829
649	It calls the "msync" function of your OS, if available, with the	830	It calls the "msync" function of your OS, if available, with the
650	memory area starting at $offset in the string and ending $length	831	memory area starting at $offset in the string and ending $length
651	bytes later. If $length is negative, counts from the end, and if	832	bytes later. If $length is negative, counts from the end, and if
652	$length is "undef", then it goes till the end of the string. The	833	$length is "undef", then it goes till the end of the string. The
…		…
663	"aio_msync", above, except for flags, which must be either 0 (which	844	"aio_msync", above, except for flags, which must be either 0 (which
664	reads all pages and ensures they are instantiated) or	845	reads all pages and ensures they are instantiated) or
665	"IO::AIO::MT_MODIFY", which modifies the memory page s(by reading	846	"IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
666	and writing an octet from it, which dirties the page).	847	and writing an octet from it, which dirties the page).
667		848
		849	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		850	This is a rather advanced IO::AIO call, which works best on
		851	mmap(2)ed scalars.
		852
		853	It reads in all the pages of the underlying storage into memory (if
		854	any) and locks them, so they are not getting swapped/paged out or
		855	removed.
		856
		857	If $length is undefined, then the scalar will be locked till the
		858	end.
		859
		860	On systems that do not implement "mlock", this function returns -1
		861	and sets errno to "ENOSYS".
		862
		863	Note that the corresponding "munlock" is synchronous and is
		864	documented under "MISCELLANEOUS FUNCTIONS".
		865
		866	Example: open a file, mmap and mlock it - both will be undone when
		867	$data gets destroyed.
		868
		869	open my $fh, "<", $path or die "$path: $!";
		870	my $data;
		871	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		872	aio_mlock $data; # mlock in background
		873
		874	aio_mlockall $flags, $callback->($status)
		875	Calls the "mlockall" function with the given $flags (a combination
		876	of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
		877
		878	On systems that do not implement "mlockall", this function returns
		879	-1 and sets errno to "ENOSYS".
		880
		881	Note that the corresponding "munlockall" is synchronous and is
		882	documented under "MISCELLANEOUS FUNCTIONS".
		883
		884	Example: asynchronously lock all current and future pages into
		885	memory.
		886
		887	aio_mlockall IO::AIO::MCL_FUTURE;
		888
		889	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		890	Queries the extents of the given file (by calling the Linux FIEMAP
		891	ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
		892	details). If the "ioctl" is not available on your OS, then this
		893	rquiest will fail with "ENOSYS".
		894
		895	$start is the starting offset to query extents for, $length is the
		896	size of the range to query - if it is "undef", then the whole file
		897	will be queried.
		898
		899	$flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
		900	"IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
		901	also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
		902	query the data portion.
		903
		904	$count is the maximum number of extent records to return. If it is
		905	"undef", then IO::AIO queries all extents of the file. As a very
		906	special case, if it is 0, then the callback receives the number of
		907	extents instead of the extents themselves.
		908
		909	If an error occurs, the callback receives no arguments. The special
		910	"errno" value "IO::AIO::EBADR" is available to test for flag errors.
		911
		912	Otherwise, the callback receives an array reference with extent
		913	structures. Each extent structure is an array reference itself, with
		914	the following members:
		915
		916	[$logical, $physical, $length, $flags]
		917
		918	Flags is any combination of the following flag values (typically
		919	either 0 or "IO::AIO::FIEMAP_EXTENT_LAST"):
		920
		921	"IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
		922	"IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
		923	"IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
		924	"IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
		925	"IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
		926	"IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
		927	"IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
		928	or "IO::AIO::FIEMAP_EXTENT_SHARED".
		929
668	aio_group $callback->(...)	930	aio_group $callback->(...)
669	This is a very special aio request: Instead of doing something, it	931	This is a very special aio request: Instead of doing something, it
670	is a container for other aio requests, which is useful if you want	932	is a container for other aio requests, which is useful if you want
671	to bundle many requests into a single, composite, request with a	933	to bundle many requests into a single, composite, request with a
672	definite callback and the ability to cancel the whole request with	934	definite callback and the ability to cancel the whole request with
…		…
705	While it is theoretically handy to have simple I/O scheduling	967	While it is theoretically handy to have simple I/O scheduling
706	requests like sleep and file handle readable/writable, the overhead	968	requests like sleep and file handle readable/writable, the overhead
707	this creates is immense (it blocks a thread for a long time) so do	969	this creates is immense (it blocks a thread for a long time) so do
708	not use this function except to put your application under	970	not use this function except to put your application under
709	artificial I/O pressure.	971	artificial I/O pressure.
		972
		973	IO::AIO::WD - multiple working directories
		974	Your process only has one current working directory, which is used by
		975	all threads. This makes it hard to use relative paths (some other
		976	component could call "chdir" at any time, and it is hard to control when
		977	the path will be used by IO::AIO).
		978
		979	One solution for this is to always use absolute paths. This usually
		980	works, but can be quite slow (the kernel has to walk the whole path on
		981	every access), and can also be a hassle to implement.
		982
		983	Newer POSIX systems have a number of functions (openat, fdopendir,
		984	futimensat and so on) that make it possible to specify working
		985	directories per operation.
		986
		987	For portability, and because the clowns who "designed", or shall I
		988	write, perpetrated this new interface were obviously half-drunk, this
		989	abstraction cannot be perfect, though.
		990
		991	IO::AIO allows you to convert directory paths into a so-called
		992	IO::AIO::WD object. This object stores the canonicalised, absolute
		993	version of the path, and on systems that allow it, also a directory file
		994	descriptor.
		995
		996	Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
		997	or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
		998	object and a pathname instead (or the IO::AIO::WD object alone, which
		999	gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
		1000	IO::AIO::WD object is ignored, otherwise the pathname is resolved
		1001	relative to that IO::AIO::WD object.
		1002
		1003	For example, to get a wd object for /etc and then stat passwd inside,
		1004	you would write:
		1005
		1006	aio_wd "/etc", sub {
		1007	my $etcdir = shift;
		1008
		1009	# although $etcdir can be undef on error, there is generally no reason
		1010	# to check for errors here, as aio_stat will fail with ENOENT
		1011	# when $etcdir is undef.
		1012
		1013	aio_stat [$etcdir, "passwd"], sub {
		1014	# yay
		1015	};
		1016	};
		1017
		1018	That "aio_wd" is a request and not a normal function shows that creating
		1019	an IO::AIO::WD object is itself a potentially blocking operation, which
		1020	is why it is done asynchronously.
		1021
		1022	To stat the directory obtained with "aio_wd" above, one could write
		1023	either of the following three request calls:
		1024
		1025	aio_lstat "/etc" , sub { ... # pathname as normal string
		1026	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1027	aio_lstat $wd , sub { ... # shorthand for the previous
		1028
		1029	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1030	object and the pathname string, so you could write the following without
		1031	causing any issues due to $path getting reused:
		1032
		1033	my $path = [$wd, undef];
		1034
		1035	for my $name (qw(abc def ghi)) {
		1036	$path->[1] = $name;
		1037	aio_stat $path, sub {
		1038	# ...
		1039	};
		1040	}
		1041
		1042	There are some caveats: when directories get renamed (or deleted), the
		1043	pathname string doesn't change, so will point to the new directory (or
		1044	nowhere at all), while the directory fd, if available on the system,
		1045	will still point to the original directory. Most functions accepting a
		1046	pathname will use the directory fd on newer systems, and the string on
		1047	older systems. Some functions (such as realpath) will always rely on the
		1048	string form of the pathname.
		1049
		1050	So this fucntionality is mainly useful to get some protection against
		1051	"chdir", to easily get an absolute path out of a relative path for
		1052	future reference, and to speed up doing many operations in the same
		1053	directory (e.g. when stat'ing all files in a directory).
		1054
		1055	The following functions implement this working directory abstraction:
		1056
		1057	aio_wd $pathname, $callback->($wd)
		1058	Asynchonously canonicalise the given pathname and convert it to an
		1059	IO::AIO::WD object representing it. If possible and supported on the
		1060	system, also open a directory fd to speed up pathname resolution
		1061	relative to this working directory.
		1062
		1063	If something goes wrong, then "undef" is passwd to the callback
		1064	instead of a working directory object and $! is set appropriately.
		1065	Since passing "undef" as working directory component of a pathname
		1066	fails the request with "ENOENT", there is often no need for error
		1067	checking in the "aio_wd" callback, as future requests using the
		1068	value will fail in the expected way.
		1069
		1070	If this call isn't available because your OS lacks it or it couldn't
		1071	be detected, it will be emulated by calling "fsync" instead.
		1072
		1073	IO::AIO::CWD
		1074	This is a compiletime constant (object) that represents the process
		1075	current working directory.
		1076
		1077	Specifying this object as working directory object for a pathname is
		1078	as if the pathname would be specified directly, without a directory
		1079	object, e.g., these calls are functionally identical:
		1080
		1081	aio_stat "somefile", sub { ... };
		1082	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
710		1083
711	IO::AIO::REQ CLASS	1084	IO::AIO::REQ CLASS
712	All non-aggregate "aio_*" functions return an object of this class when	1085	All non-aggregate "aio_*" functions return an object of this class when
713	called in non-void context.	1086	called in non-void context.
714		1087
…		…
814	Sets a feeder/generator on this group: every group can have an	1187	Sets a feeder/generator on this group: every group can have an
815	attached generator that generates requests if idle. The idea behind	1188	attached generator that generates requests if idle. The idea behind
816	this is that, although you could just queue as many requests as you	1189	this is that, although you could just queue as many requests as you
817	want in a group, this might starve other requests for a potentially	1190	want in a group, this might starve other requests for a potentially
818	long time. For example, "aio_scandir" might generate hundreds of	1191	long time. For example, "aio_scandir" might generate hundreds of
819	thousands "aio_stat" requests, delaying any later requests for a	1192	thousands of "aio_stat" requests, delaying any later requests for a
820	long time.	1193	long time.
821		1194
822	To avoid this, and allow incremental generation of requests, you can	1195	To avoid this, and allow incremental generation of requests, you can
823	instead a group and set a feeder on it that generates those	1196	instead a group and set a feeder on it that generates those
824	requests. The feed callback will be called whenever there are few	1197	requests. The feed callback will be called whenever there are few
…		…
867		1240
868	See "poll_cb" for an example.	1241	See "poll_cb" for an example.
869		1242
870	IO::AIO::poll_cb	1243	IO::AIO::poll_cb
871	Process some outstanding events on the result pipe. You have to call	1244	Process some outstanding events on the result pipe. You have to call
872	this regularly. Returns 0 if all events could be processed, or -1 if	1245	this regularly. Returns 0 if all events could be processed (or there
873	it returned earlier for whatever reason. Returns immediately when no	1246	were no events to process), or -1 if it returned earlier for
874	events are outstanding. The amount of events processed depends on	1247	whatever reason. Returns immediately when no events are outstanding.
875	the settings of "IO::AIO::max_poll_req" and	1248	The amount of events processed depends on the settings of
876	"IO::AIO::max_poll_time".	1249	"IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
877		1250
878	If not all requests were processed for whatever reason, the	1251	If not all requests were processed for whatever reason, the
879	filehandle will still be ready when "poll_cb" returns, so normally	1252	filehandle will still be ready when "poll_cb" returns, so normally
880	you don't have to do anything special to have it called later.	1253	you don't have to do anything special to have it called later.
881		1254
		1255	Apart from calling "IO::AIO::poll_cb" when the event filehandle
		1256	becomes ready, it can be beneficial to call this function from loops
		1257	which submit a lot of requests, to make sure the results get
		1258	processed when they become available and not just when the loop is
		1259	finished and the event loop takes over again. This function returns
		1260	very fast when there are no outstanding requests.
		1261
882	Example: Install an Event watcher that automatically calls	1262	Example: Install an Event watcher that automatically calls
883	IO::AIO::poll_cb with high priority (more examples can be found in	1263	IO::AIO::poll_cb with high priority (more examples can be found in
884	the SYNOPSIS section, at the top of this document):	1264	the SYNOPSIS section, at the top of this document):
885		1265
886	Event->io (fd => IO::AIO::poll_fileno,	1266	Event->io (fd => IO::AIO::poll_fileno,
887	poll => 'r', async => 1,	1267	poll => 'r', async => 1,
888	cb => \&IO::AIO::poll_cb);	1268	cb => \&IO::AIO::poll_cb);
		1269
		1270	IO::AIO::poll_wait
		1271	If there are any outstanding requests and none of them in the result
		1272	phase, wait till the result filehandle becomes ready for reading
		1273	(simply does a "select" on the filehandle. This is useful if you
		1274	want to synchronously wait for some requests to finish).
		1275
		1276	See "nreqs" for an example.
		1277
		1278	IO::AIO::poll
		1279	Waits until some requests have been handled.
		1280
		1281	Returns the number of requests processed, but is otherwise strictly
		1282	equivalent to:
		1283
		1284	IO::AIO::poll_wait, IO::AIO::poll_cb
		1285
		1286	IO::AIO::flush
		1287	Wait till all outstanding AIO requests have been handled.
		1288
		1289	Strictly equivalent to:
		1290
		1291	IO::AIO::poll_wait, IO::AIO::poll_cb
		1292	while IO::AIO::nreqs;
889		1293
890	IO::AIO::max_poll_reqs $nreqs	1294	IO::AIO::max_poll_reqs $nreqs
891	IO::AIO::max_poll_time $seconds	1295	IO::AIO::max_poll_time $seconds
892	These set the maximum number of requests (default 0, meaning	1296	These set the maximum number of requests (default 0, meaning
893	infinity) that are being processed by "IO::AIO::poll_cb" in one	1297	infinity) that are being processed by "IO::AIO::poll_cb" in one
…		…
917	# use a low priority so other tasks have priority	1321	# use a low priority so other tasks have priority
918	Event->io (fd => IO::AIO::poll_fileno,	1322	Event->io (fd => IO::AIO::poll_fileno,
919	poll => 'r', nice => 1,	1323	poll => 'r', nice => 1,
920	cb => &IO::AIO::poll_cb);	1324	cb => &IO::AIO::poll_cb);
921		1325
922	IO::AIO::poll_wait
923	If there are any outstanding requests and none of them in the result
924	phase, wait till the result filehandle becomes ready for reading
925	(simply does a "select" on the filehandle. This is useful if you
926	want to synchronously wait for some requests to finish).
927
928	See "nreqs" for an example.
929
930	IO::AIO::poll
931	Waits until some requests have been handled.
932
933	Returns the number of requests processed, but is otherwise strictly
934	equivalent to:
935
936	IO::AIO::poll_wait, IO::AIO::poll_cb
937
938	IO::AIO::flush
939	Wait till all outstanding AIO requests have been handled.
940
941	Strictly equivalent to:
942
943	IO::AIO::poll_wait, IO::AIO::poll_cb
944	while IO::AIO::nreqs;
945
946	CONTROLLING THE NUMBER OF THREADS	1326	CONTROLLING THE NUMBER OF THREADS
947	IO::AIO::min_parallel $nthreads	1327	IO::AIO::min_parallel $nthreads
948	Set the minimum number of AIO threads to $nthreads. The current	1328	Set the minimum number of AIO threads to $nthreads. The current
949	default is 8, which means eight asynchronous operations can execute	1329	default is 8, which means eight asynchronous operations can execute
950	concurrently at any one time (the number of outstanding requests,	1330	concurrently at any one time (the number of outstanding requests,
…		…
979		1359
980	Under normal circumstances you don't need to call this function.	1360	Under normal circumstances you don't need to call this function.
981		1361
982	IO::AIO::max_idle $nthreads	1362	IO::AIO::max_idle $nthreads
983	Limit the number of threads (default: 4) that are allowed to idle	1363	Limit the number of threads (default: 4) that are allowed to idle
984	(i.e., threads that did not get a request to process within 10	1364	(i.e., threads that did not get a request to process within the idle
985	seconds). That means if a thread becomes idle while $nthreads other	1365	timeout (default: 10 seconds). That means if a thread becomes idle
986	threads are also idle, it will free its resources and exit.	1366	while $nthreads other threads are also idle, it will free its
		1367	resources and exit.
987		1368
988	This is useful when you allow a large number of threads (e.g. 100 or	1369	This is useful when you allow a large number of threads (e.g. 100 or
989	1000) to allow for extremely high load situations, but want to free	1370	1000) to allow for extremely high load situations, but want to free
990	resources under normal circumstances (1000 threads can easily	1371	resources under normal circumstances (1000 threads can easily
991	consume 30MB of RAM).	1372	consume 30MB of RAM).
992		1373
993	The default is probably ok in most situations, especially if thread	1374	The default is probably ok in most situations, especially if thread
994	creation is fast. If thread creation is very slow on your system you	1375	creation is fast. If thread creation is very slow on your system you
995	might want to use larger values.	1376	might want to use larger values.
996		1377
		1378	IO::AIO::idle_timeout $seconds
		1379	Sets the minimum idle timeout (default 10) after which worker
		1380	threads are allowed to exit. SEe "IO::AIO::max_idle".
		1381
997	IO::AIO::max_outstanding $maxreqs	1382	IO::AIO::max_outstanding $maxreqs
		1383	Sets the maximum number of outstanding requests to $nreqs. If you do
		1384	queue up more than this number of requests, the next call to
		1385	"IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
		1386	"IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
		1387	no longer exceeded.
		1388
		1389	In other words, this setting does not enforce a queue limit, but can
		1390	be used to make poll functions block if the limit is exceeded.
		1391
998	This is a very bad function to use in interactive programs because	1392	This is a very bad function to use in interactive programs because
999	it blocks, and a bad way to reduce concurrency because it is	1393	it blocks, and a bad way to reduce concurrency because it is
1000	inexact: Better use an "aio_group" together with a feed callback.	1394	inexact: Better use an "aio_group" together with a feed callback.
1001		1395
1002	Sets the maximum number of outstanding requests to $nreqs. If you do	1396	It's main use is in scripts without an event loop - when you want to
1003	queue up more than this number of requests, the next call to the	1397	stat a lot of files, you can write somehting like this:
1004	"poll_cb" (and "poll_some" and other functions calling "poll_cb")
1005	function will block until the limit is no longer exceeded.
1006		1398
1007	The default value is very large, so there is no practical limit on	1399	IO::AIO::max_outstanding 32;
		1400
		1401	for my $path (...) {
		1402	aio_stat $path , ...;
		1403	IO::AIO::poll_cb;
		1404	}
		1405
		1406	IO::AIO::flush;
		1407
		1408	The call to "poll_cb" inside the loop will normally return
		1409	instantly, but as soon as more thna 32 reqeusts are in-flight, it
		1410	will block until some requests have been handled. This keeps the
		1411	loop from pushing a large number of "aio_stat" requests onto the
		1412	queue.
		1413
		1414	The default value for "max_outstanding" is very large, so there is
1008	the number of outstanding requests.	1415	no practical limit on the number of outstanding requests.
1009
1010	You can still queue as many requests as you want. Therefore,
1011	"max_outstanding" is mainly useful in simple scripts (with low
1012	values) or as a stop gap to shield against fatal memory overflow
1013	(with large values).
1014		1416
1015	STATISTICAL INFORMATION	1417	STATISTICAL INFORMATION
1016	IO::AIO::nreqs	1418	IO::AIO::nreqs
1017	Returns the number of requests currently in the ready, execute or	1419	Returns the number of requests currently in the ready, execute or
1018	pending states (i.e. for which their callback has not been invoked	1420	pending states (i.e. for which their callback has not been invoked
…		…
1042	set to non-blocking operations).	1444	set to non-blocking operations).
1043		1445
1044	Returns the number of bytes copied, or -1 on error.	1446	Returns the number of bytes copied, or -1 on error.
1045		1447
1046	IO::AIO::fadvise $fh, $offset, $len, $advice	1448	IO::AIO::fadvise $fh, $offset, $len, $advice
1047	Simply calls the "posix_fadvise" function (see it's manpage for	1449	Simply calls the "posix_fadvise" function (see its manpage for
1048	details). The following advice constants are avaiable:	1450	details). The following advice constants are available:
1049	"IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",	1451	"IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1050	"IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",	1452	"IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1051	"IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".	1453	"IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1052		1454
1053	On systems that do not implement "posix_fadvise", this function	1455	On systems that do not implement "posix_fadvise", this function
1054	returns ENOSYS, otherwise the return value of "posix_fadvise".	1456	returns ENOSYS, otherwise the return value of "posix_fadvise".
1055		1457
		1458	IO::AIO::madvise $scalar, $offset, $len, $advice
		1459	Simply calls the "posix_madvise" function (see its manpage for
		1460	details). The following advice constants are available:
		1461	"IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
		1462	"IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
		1463	"IO::AIO::MADV_DONTNEED".
		1464
		1465	On systems that do not implement "posix_madvise", this function
		1466	returns ENOSYS, otherwise the return value of "posix_madvise".
		1467
		1468	IO::AIO::mprotect $scalar, $offset, $len, $protect
		1469	Simply calls the "mprotect" function on the preferably AIO::mmap'ed
		1470	$scalar (see its manpage for details). The following protect
		1471	constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
		1472	"IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
		1473
		1474	On systems that do not implement "mprotect", this function returns
		1475	ENOSYS, otherwise the return value of "mprotect".
		1476
		1477	IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1478	Memory-maps a file (or anonymous memory range) and attaches it to
		1479	the given $scalar, which will act like a string scalar.
		1480
		1481	The only operations allowed on the scalar are "substr"/"vec" that
		1482	don't change the string length, and most read-only operations such
		1483	as copying it or searching it with regexes and so on.
		1484
		1485	Anything else is unsafe and will, at best, result in memory leaks.
		1486
		1487	The memory map associated with the $scalar is automatically removed
		1488	when the $scalar is destroyed, or when the "IO::AIO::mmap" or
		1489	"IO::AIO::munmap" functions are called.
		1490
		1491	This calls the "mmap"(2) function internally. See your system's
		1492	manual page for details on the $length, $prot and $flags parameters.
		1493
		1494	The $length must be larger than zero and smaller than the actual
		1495	filesize.
		1496
		1497	$prot is a combination of "IO::AIO::PROT_NONE",
		1498	"IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
		1499	"IO::AIO::PROT_WRITE",
		1500
		1501	$flags can be a combination of "IO::AIO::MAP_SHARED" or
		1502	"IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
		1503	not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
		1504	(which is set to "MAP_ANON" if your system only provides this
		1505	constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
		1506	"IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
		1507	"IO::AIO::MAP_NONBLOCK"
		1508
		1509	If $fh is "undef", then a file descriptor of -1 is passed.
		1510
		1511	$offset is the offset from the start of the file - it generally must
		1512	be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
		1513
		1514	Example:
		1515
		1516	use Digest::MD5;
		1517	use IO::AIO;
		1518
		1519	open my $fh, "<verybigfile"
		1520	or die "$!";
		1521
		1522	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1523	or die "verybigfile: $!";
		1524
		1525	my $fast_md5 = md5 $data;
		1526
		1527	IO::AIO::munmap $scalar
		1528	Removes a previous mmap and undefines the $scalar.
		1529
		1530	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1531	Calls the "munlock" function, undoing the effects of a previous
		1532	"aio_mlock" call (see its description for details).
		1533
		1534	IO::AIO::munlockall
		1535	Calls the "munlockall" function.
		1536
		1537	On systems that do not implement "munlockall", this function returns
		1538	ENOSYS, otherwise the return value of "munlockall".
		1539
		1540	IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		1541	Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
		1542	$w_off are "undef", then "NULL" is passed for these, otherwise they
		1543	should be the file offset.
		1544
		1545	The following symbol flag values are available:
		1546	"IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
		1547	"IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
		1548
		1549	See the splice(2) manpage for details.
		1550
		1551	IO::AIO::tee $r_fh, $w_fh, $length, $flags
		1552	Calls the GNU/Linux tee(2) syscall, see it's manpage and the
		1553	description for "IO::AIO::splice" above for details.
		1554
		1555	EVENT LOOP INTEGRATION
		1556	It is recommended to use AnyEvent::AIO to integrate IO::AIO
		1557	automatically into many event loops:
		1558
		1559	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1560	use AnyEvent::AIO;
		1561
		1562	You can also integrate IO::AIO manually into many event loops, here are
		1563	some examples of how to do this:
		1564
		1565	# EV integration
		1566	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1567
		1568	# Event integration
		1569	Event->io (fd => IO::AIO::poll_fileno,
		1570	poll => 'r',
		1571	cb => \&IO::AIO::poll_cb);
		1572
		1573	# Glib/Gtk2 integration
		1574	add_watch Glib::IO IO::AIO::poll_fileno,
		1575	in => sub { IO::AIO::poll_cb; 1 };
		1576
		1577	# Tk integration
		1578	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1579	readable => \&IO::AIO::poll_cb);
		1580
		1581	# Danga::Socket integration
		1582	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1583	\&IO::AIO::poll_cb);
		1584
1056	FORK BEHAVIOUR	1585	FORK BEHAVIOUR
1057	This module should do "the right thing" when the process using it forks:	1586	Usage of pthreads in a program changes the semantics of fork
		1587	considerably. Specifically, only async-safe functions can be called
		1588	after fork. Perl doesn't know about this, so in general, you cannot call
		1589	fork with defined behaviour in perl if pthreads are involved. IO::AIO
		1590	uses pthreads, so this applies, but many other extensions and (for
		1591	inexplicable reasons) perl itself often is linked against pthreads, so
		1592	this limitation applies to quite a lot of perls.
1058		1593
1059	Before the fork, IO::AIO enters a quiescent state where no requests can	1594	This module no longer tries to fight your OS, or POSIX. That means
1060	be added in other threads and no results will be processed. After the	1595	IO::AIO only works in the process that loaded it. Forking is fully
1061	fork the parent simply leaves the quiescent state and continues	1596	supported, but using IO::AIO in the child is not.
1062	request/result processing, while the child frees the request/result
1063	queue (so that the requests started before the fork will only be handled
1064	in the parent). Threads will be started on demand until the limit set in
1065	the parent process has been reached again.
1066		1597
1067	In short: the parent will, after a short pause, continue as if fork had	1598	You might get around by not using IO::AIO before (or after) forking.
1068	not been called, while the child will act as if IO::AIO has not been	1599	You could also try to call the IO::AIO::reinit function in the child:
1069	used yet.	1600
		1601	IO::AIO::reinit
		1602	Abandons all current requests and I/O threads and simply
		1603	reinitialises all data structures. This is not an operation
		1604	supported by any standards, but happens to work on GNU/Linux and
		1605	some newer BSD systems.
		1606
		1607	The only reasonable use for this function is to call it after
		1608	forking, if "IO::AIO" was used in the parent. Calling it while
		1609	IO::AIO is active in the process will result in undefined behaviour.
		1610	Calling it at any time will also result in any undefined (by POSIX)
		1611	behaviour.
1070		1612
1071	MEMORY USAGE	1613	MEMORY USAGE
1072	Per-request usage:	1614	Per-request usage:
1073		1615
1074	Each aio request uses - depending on your architecture - around 100-200	1616	Each aio request uses - depending on your architecture - around 100-200

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Comparing IO-AIO/README (file contents): Revision 1.41 by root, Sat Jan 2 14:24:32 2010 UTC vs. Revision 1.52 by root, Tue Apr 10 05:01:33 2012 UTC

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Comparing IO-AIO/README (file contents):
Revision 1.41 by root, Sat Jan 2 14:24:32 2010 UTC vs.
Revision 1.52 by root, Tue Apr 10 05:01:33 2012 UTC