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

Comparing IO-AIO/README (file contents):
Revision 1.21 by root, Fri Dec 22 04:05:50 2006 UTC vs.
Revision 1.44 by root, Mon Nov 1 22:03:43 2010 UTC

…		…
2	IO::AIO - Asynchronous Input/Output	2	IO::AIO - Asynchronous Input/Output
3		3
4	SYNOPSIS	4	SYNOPSIS
5	use IO::AIO;	5	use IO::AIO;
6		6
7	aio_open "/etc/passwd", O_RDONLY, 0, sub {	7	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8	my $fh = shift	8	my $fh = shift
9	or die "/etc/passwd: $!";	9	or die "/etc/passwd: $!";
10	...	10	...
11	};	11	};
12		12
…		…
24	$req->cancel; # cancel request if still in queue	24	$req->cancel; # cancel request if still in queue
25		25
26	my $grp = aio_group sub { print "all stats done\n" };	26	my $grp = aio_group sub { print "all stats done\n" };
27	add $grp aio_stat "..." for ...;	27	add $grp aio_stat "..." for ...;
28		28
29	# AnyEvent integration
30	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
31	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
32
33	# Event integration
34	Event->io (fd => IO::AIO::poll_fileno,
35	poll => 'r',
36	cb => \&IO::AIO::poll_cb);
37
38	# Glib/Gtk2 integration
39	add_watch Glib::IO IO::AIO::poll_fileno,
40	in => sub { IO::AIO::poll_cb; 1 };
41
42	# Tk integration
43	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
44	readable => \&IO::AIO::poll_cb);
45
46	# Danga::Socket integration
47	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
48	\&IO::AIO::poll_cb);
49
50	DESCRIPTION	29	DESCRIPTION
51	This module implements asynchronous I/O using whatever means your	30	This module implements asynchronous I/O using whatever means your
52	operating system supports.	31	operating system supports. It is implemented as an interface to "libeio"
		32	(<http://software.schmorp.de/pkg/libeio.html>).
53		33
54	Asynchronous means that operations that can normally block your program	34	Asynchronous means that operations that can normally block your program
55	(e.g. reading from disk) will be done asynchronously: the operation will	35	(e.g. reading from disk) will be done asynchronously: the operation will
56	still block, but you can do something else in the meantime. This is	36	still block, but you can do something else in the meantime. This is
57	extremely useful for programs that need to stay interactive even when	37	extremely useful for programs that need to stay interactive even when
…		…
61	faster on a RAID volume or over NFS when you do a number of stat	41	faster on a RAID volume or over NFS when you do a number of stat
62	operations concurrently.	42	operations concurrently.
63		43
64	While most of this works on all types of file descriptors (for example	44	While most of this works on all types of file descriptors (for example
65	sockets), using these functions on file descriptors that support	45	sockets), using these functions on file descriptors that support
66	nonblocking operation (again, sockets, pipes etc.) is very inefficient	46	nonblocking operation (again, sockets, pipes etc.) is very inefficient.
67	or might not work (aio_read fails on sockets/pipes/fifos). Use an event
68	loop for that (such as the Event module): IO::AIO will naturally fit	47	Use an event loop for that (such as the EV module): IO::AIO will
69	into such an event loop itself.	48	naturally fit into such an event loop itself.
70		49
71	In this version, a number of threads are started that execute your	50	In this version, a number of threads are started that execute your
72	requests and signal their completion. You don't need thread support in	51	requests and signal their completion. You don't need thread support in
73	perl, and the threads created by this module will not be visible to	52	perl, and the threads created by this module will not be visible to
74	perl. In the future, this module might make use of the native aio	53	perl. In the future, this module might make use of the native aio
…		…
76	not well-supported or restricted (GNU/Linux doesn't allow them on normal	55	not well-supported or restricted (GNU/Linux doesn't allow them on normal
77	files currently, for example), and they would only support aio_read and	56	files currently, for example), and they would only support aio_read and
78	aio_write, so the remaining functionality would have to be implemented	57	aio_write, so the remaining functionality would have to be implemented
79	using threads anyway.	58	using threads anyway.
80		59
81	Although the module will work with in the presence of other (Perl-)	60	Although the module will work in the presence of other (Perl-) threads,
82	threads, it is currently not reentrant in any way, so use appropriate	61	it is currently not reentrant in any way, so use appropriate locking
83	locking yourself, always call "poll_cb" from within the same thread, or	62	yourself, always call "poll_cb" from within the same thread, or never
84	never call "poll_cb" (or other "aio_" functions) recursively.	63	call "poll_cb" (or other "aio_" functions) recursively.
85		64
86	EXAMPLE	65	EXAMPLE
87	This is a simple example that uses the Event module and loads	66	This is a simple example that uses the EV module and loads /etc/passwd
88	/etc/passwd asynchronously:	67	asynchronously:
89		68
90	use Fcntl;	69	use Fcntl;
91	use Event;	70	use EV;
92	use IO::AIO;	71	use IO::AIO;
93		72
94	# register the IO::AIO callback with Event	73	# register the IO::AIO callback with EV
95	Event->io (fd => IO::AIO::poll_fileno,	74	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
96	poll => 'r',
97	cb => \&IO::AIO::poll_cb);
98		75
99	# queue the request to open /etc/passwd	76	# queue the request to open /etc/passwd
100	aio_open "/etc/passwd", O_RDONLY, 0, sub {	77	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
101	my $fh = shift	78	my $fh = shift
102	or die "error while opening: $!";	79	or die "error while opening: $!";
103		80
104	# stat'ing filehandles is generally non-blocking	81	# stat'ing filehandles is generally non-blocking
105	my $size = -s $fh;	82	my $size = -s $fh;
…		…
114		91
115	# file contents now in $contents	92	# file contents now in $contents
116	print $contents;	93	print $contents;
117		94
118	# exit event loop and program	95	# exit event loop and program
119	Event::unloop;	96	EV::unloop;
120	};	97	};
121	};	98	};
122		99
123	# possibly queue up other requests, or open GUI windows,	100	# possibly queue up other requests, or open GUI windows,
124	# check for sockets etc. etc.	101	# check for sockets etc. etc.
125		102
126	# process events as long as there are some:	103	# process events as long as there are some:
127	Event::loop;	104	EV::loop;
128		105
129	REQUEST ANATOMY AND LIFETIME	106	REQUEST ANATOMY AND LIFETIME
130	Every "aio_*" function creates a request. which is a C data structure	107	Every "aio_*" function creates a request. which is a C data structure
131	not directly visible to Perl.	108	not directly visible to Perl.
132		109
…		…
168	anymore (except possibly for the Perl object, but its connection to	145	anymore (except possibly for the Perl object, but its connection to
169	the actual aio request is severed and calling its methods will	146	the actual aio request is severed and calling its methods will
170	either do nothing or result in a runtime error).	147	either do nothing or result in a runtime error).
171		148
172	FUNCTIONS	149	FUNCTIONS
		150	QUICK OVERVIEW
		151	This section simply lists the prototypes of the most important functions
		152	for quick reference. See the following sections for function-by-function
		153	documentation.
		154
		155	aio_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::max_outstanding $maxreqs
		210	IO::AIO::nreqs
		211	IO::AIO::nready
		212	IO::AIO::npending
		213
		214	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		215	IO::AIO::fadvise $fh, $offset, $len, $advice
		216	IO::AIO::madvise $scalar, $offset, $length, $advice
		217	IO::AIO::mprotect $scalar, $offset, $length, $protect
		218	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		219	IO::AIO::munlockall
		220
173	AIO REQUEST FUNCTIONS	221	AIO REQUEST FUNCTIONS
174	All the "aio_*" calls are more or less thin wrappers around the syscall	222	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	223	with the same name (sans "aio_"). The arguments are similar or
176	identical, and they all accept an additional (and optional) $callback	224	identical, and they all accept an additional (and optional) $callback
177	argument which must be a code reference. This code reference will get	225	argument which must be a code reference. This code reference will get
178	called with the syscall return code (e.g. most syscalls return -1 on	226	called with the syscall return code (e.g. most syscalls return -1 on
179	error, unlike perl, which usually delivers "false") as it's sole	227	error, unlike perl, which usually delivers "false") as its sole argument
180	argument when the given syscall has been executed asynchronously.	228	after the given syscall has been executed asynchronously.
181		229
182	All functions expecting a filehandle keep a copy of the filehandle	230	All functions expecting a filehandle keep a copy of the filehandle
183	internally until the request has finished.	231	internally until the request has finished.
184		232
185	All functions return request objects of type IO::AIO::REQ that allow	233	All functions return request objects of type IO::AIO::REQ that allow
…		…
198	the user environment, d) use Glib::filename_from_unicode on unicode	246	the user environment, d) use Glib::filename_from_unicode on unicode
199	filenames or e) use something else to ensure your scalar has the correct	247	filenames or e) use something else to ensure your scalar has the correct
200	contents.	248	contents.
201		249
202	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	250	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203	handles correctly wether it is set or not.	251	handles correctly whether it is set or not.
204		252
205	$prev_pri = aioreq_pri [$pri]	253	$prev_pri = aioreq_pri [$pri]
206	Returns the priority value that would be used for the next request	254	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.	255	and, if $pri is given, sets the priority for the next aio request.
208		256
…		…
242	They are the same as used by "sysopen".	290	They are the same as used by "sysopen".
243		291
244	Likewise, $mode specifies the mode of the newly created file, if it	292	Likewise, $mode specifies the mode of the newly created file, if it
245	didn't exist and "O_CREAT" has been given, just like perl's	293	didn't exist and "O_CREAT" has been given, just like perl's
246	"sysopen", except that it is mandatory (i.e. use 0 if you don't	294	"sysopen", except that it is mandatory (i.e. use 0 if you don't
247	create new files, and 0666 or 0777 if you do).	295	create new files, and 0666 or 0777 if you do). Note that the $mode
		296	will be modified by the umask in effect then the request is being
		297	executed, so better never change the umask.
248		298
249	Example:	299	Example:
250		300
251	aio_open "/etc/passwd", O_RDONLY, 0, sub {	301	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
252	if ($_[0]) {	302	if ($_[0]) {
253	print "open successful, fh is $_[0]\n";	303	print "open successful, fh is $_[0]\n";
254	...	304	...
255	} else {	305	} else {
256	die "open failed: $!\n";	306	die "open failed: $!\n";
257	}	307	}
258	};	308	};
259		309
260	aio_close $fh, $callback->($status)	310	aio_close $fh, $callback->($status)
261	Asynchronously close a file and call the callback with the result	311	Asynchronously close a file and call the callback with the result
262	code. WARNING: although accepted, you should not pass in a perl	312	code.
263	filehandle here, as perl will likely close the file descriptor
264	another time when the filehandle is destroyed. Normally, you can
265	safely call perls "close" or just let filehandles go out of scope.
266		313
267	This is supposed to be a bug in the API, so that might change. It's	314	Unfortunately, you can't do this to perl. Perl insists very
268	therefore best to avoid this function.	315	strongly on closing the file descriptor associated with the
		316	filehandle itself.
		317
		318	Therefore, "aio_close" will not close the filehandle - instead it
		319	will use dup2 to overwrite the file descriptor with the write-end of
		320	a pipe (the pipe fd will be created on demand and will be cached).
		321
		322	Or in other words: the file descriptor will be closed, but it will
		323	not be free for reuse until the perl filehandle is closed.
269		324
270	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	325	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
271	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	326	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
272	Reads or writes "length" bytes from the specified "fh" and "offset"	327	Reads or writes $length bytes from or to the specified $fh and
273	into the scalar given by "data" and offset "dataoffset" and calls	328	$offset into the scalar given by $data and offset $dataoffset and
274	the callback without the actual number of bytes read (or -1 on	329	calls the callback without the actual number of bytes read (or -1 on
275	error, just like the syscall).	330	error, just like the syscall).
276		331
		332	"aio_read" will, like "sysread", shrink or grow the $data scalar to
		333	offset plus the actual number of bytes read.
		334
		335	If $offset is undefined, then the current file descriptor offset
		336	will be used (and updated), otherwise the file descriptor offset
		337	will not be changed by these calls.
		338
		339	If $length is undefined in "aio_write", use the remaining length of
		340	$data.
		341
		342	If $dataoffset is less than zero, it will be counted from the end of
		343	$data.
		344
277	The $data scalar MUST NOT be modified in any way while the request	345	The $data scalar MUST NOT be modified in any way while the request
278	is outstanding. Modifying it can result in segfaults or WW3 (if the	346	is outstanding. Modifying it can result in segfaults or World War
279	necessary/optional hardware is installed).	347	III (if the necessary/optional hardware is installed).
280		348
281	Example: Read 15 bytes at offset 7 into scalar $buffer, starting at	349	Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
282	offset 0 within the scalar:	350	offset 0 within the scalar:
283		351
284	aio_read $fh, 7, 15, $buffer, 0, sub {	352	aio_read $fh, 7, 15, $buffer, 0, sub {
…		…
293	more than one "aio_sendfile" per $out_fh, as they will interfere	361	more than one "aio_sendfile" per $out_fh, as they will interfere
294	with each other.	362	with each other.
295		363
296	This call tries to make use of a native "sendfile" syscall to	364	This call tries to make use of a native "sendfile" syscall to
297	provide zero-copy operation. For this to work, $out_fh should refer	365	provide zero-copy operation. For this to work, $out_fh should refer
298	to a socket, and $in_fh should refer to mmap'able file.	366	to a socket, and $in_fh should refer to an mmap'able file.
299		367
300	If the native sendfile call fails or is not implemented, it will be	368	If a native sendfile cannot be found or it fails with "ENOSYS",
		369	"ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK",
301	emulated, so you can call "aio_sendfile" on any type of filehandle	370	it will be emulated, so you can call "aio_sendfile" on any type of
302	regardless of the limitations of the operating system.	371	filehandle regardless of the limitations of the operating system.
303		372
304	Please note, however, that "aio_sendfile" can read more bytes from	373	Please note, however, that "aio_sendfile" can read more bytes from
305	$in_fh than are written, and there is no way to find out how many	374	$in_fh than are written, and there is no way to find out how many
306	bytes have been read from "aio_sendfile" alone, as "aio_sendfile"	375	bytes have been read from "aio_sendfile" alone, as "aio_sendfile"
307	only provides the number of bytes written to $out_fh. Only if the	376	only provides the number of bytes written to $out_fh. Only if the
…		…
342	aio_stat "/etc/passwd", sub {	411	aio_stat "/etc/passwd", sub {
343	$_[0] and die "stat failed: $!";	412	$_[0] and die "stat failed: $!";
344	print "size is ", -s _, "\n";	413	print "size is ", -s _, "\n";
345	};	414	};
346		415
		416	aio_statvfs $fh_or_path, $callback->($statvfs)
		417	Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
		418	whether a file handle or path was passed.
		419
		420	On success, the callback is passed a hash reference with the
		421	following members: "bsize", "frsize", "blocks", "bfree", "bavail",
		422	"files", "ffree", "favail", "fsid", "flag" and "namemax". On
		423	failure, "undef" is passed.
		424
		425	The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
		426	and "ST_NOSUID".
		427
		428	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		429	their correct value when available, or to 0 on systems that do not
		430	support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
		431	"ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
		432	"ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
		433
		434	Example: stat "/wd" and dump out the data if successful.
		435
		436	aio_statvfs "/wd", sub {
		437	my $f = $_[0]
		438	or die "statvfs: $!";
		439
		440	use Data::Dumper;
		441	say Dumper $f;
		442	};
		443
		444	# result:
		445	{
		446	bsize => 1024,
		447	bfree => 4333064312,
		448	blocks => 10253828096,
		449	files => 2050765568,
		450	flag => 4096,
		451	favail => 2042092649,
		452	bavail => 4333064312,
		453	ffree => 2042092649,
		454	namemax => 255,
		455	frsize => 1024,
		456	fsid => 1810
		457	}
		458
		459	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		460	Works like perl's "utime" function (including the special case of
		461	$atime and $mtime being undef). Fractional times are supported if
		462	the underlying syscalls support them.
		463
		464	When called with a pathname, uses utimes(2) if available, otherwise
		465	utime(2). If called on a file descriptor, uses futimes(2) if
		466	available, otherwise returns ENOSYS, so this is not portable.
		467
		468	Examples:
		469
		470	# set atime and mtime to current time (basically touch(1)):
		471	aio_utime "path", undef, undef;
		472	# set atime to current time and mtime to beginning of the epoch:
		473	aio_utime "path", time, undef; # undef==0
		474
		475	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		476	Works like perl's "chown" function, except that "undef" for either
		477	$uid or $gid is being interpreted as "do not change" (but -1 can
		478	also be used).
		479
		480	Examples:
		481
		482	# same as "chown root path" in the shell:
		483	aio_chown "path", 0, -1;
		484	# same as above:
		485	aio_chown "path", 0, undef;
		486
		487	aio_truncate $fh_or_path, $offset, $callback->($status)
		488	Works like truncate(2) or ftruncate(2).
		489
		490	aio_chmod $fh_or_path, $mode, $callback->($status)
		491	Works like perl's "chmod" function.
		492
347	aio_unlink $pathname, $callback->($status)	493	aio_unlink $pathname, $callback->($status)
348	Asynchronously unlink (delete) a file and call the callback with the	494	Asynchronously unlink (delete) a file and call the callback with the
349	result code.	495	result code.
350		496
351	aio_mknod $path, $mode, $dev, $callback->($status)	497	aio_mknod $path, $mode, $dev, $callback->($status)
…		…
373		519
374	aio_rename $srcpath, $dstpath, $callback->($status)	520	aio_rename $srcpath, $dstpath, $callback->($status)
375	Asynchronously rename the object at $srcpath to $dstpath, just as	521	Asynchronously rename the object at $srcpath to $dstpath, just as
376	rename(2) and call the callback with the result code.	522	rename(2) and call the callback with the result code.
377		523
		524	aio_mkdir $pathname, $mode, $callback->($status)
		525	Asynchronously mkdir (create) a directory and call the callback with
		526	the result code. $mode will be modified by the umask at the time the
		527	request is executed, so do not change your umask.
		528
378	aio_rmdir $pathname, $callback->($status)	529	aio_rmdir $pathname, $callback->($status)
379	Asynchronously rmdir (delete) a directory and call the callback with	530	Asynchronously rmdir (delete) a directory and call the callback with
380	the result code.	531	the result code.
381		532
382	aio_readdir $pathname, $callback->($entries)	533	aio_readdir $pathname, $callback->($entries)
383	Unlike the POSIX call of the same name, "aio_readdir" reads an	534	Unlike the POSIX call of the same name, "aio_readdir" reads an
384	entire directory (i.e. opendir + readdir + closedir). The entries	535	entire directory (i.e. opendir + readdir + closedir). The entries
385	will not be sorted, and will NOT include the "." and ".." entries.	536	will not be sorted, and will NOT include the "." and ".." entries.
386		537
387	The callback a single argument which is either "undef" or an	538	The callback is passed a single argument which is either "undef" or
388	array-ref with the filenames.	539	an array-ref with the filenames.
		540
		541	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		542	Quite similar to "aio_readdir", but the $flags argument allows to
		543	tune behaviour and output format. In case of an error, $entries will
		544	be "undef".
		545
		546	The flags are a combination of the following constants, ORed
		547	together (the flags will also be passed to the callback, possibly
		548	modified):
		549
		550	IO::AIO::READDIR_DENTS
		551	When this flag is off, then the callback gets an arrayref with
		552	of names only (as with "aio_readdir"), otherwise it gets an
		553	arrayref with "[$name, $type, $inode]" arrayrefs, each
		554	describing a single directory entry in more detail.
		555
		556	$name is the name of the entry.
		557
		558	$type is one of the "IO::AIO::DT_xxx" constants:
		559
		560	"IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
		561	"IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
		562	"IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
		563
		564	"IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
		565	you need to know, you have to run stat yourself. Also, for speed
		566	reasons, the $type scalars are read-only: you can not modify
		567	them.
		568
		569	$inode is the inode number (which might not be exact on systems
		570	with 64 bit inode numbers and 32 bit perls). This field has
		571	unspecified content on systems that do not deliver the inode
		572	information.
		573
		574	IO::AIO::READDIR_DIRS_FIRST
		575	When this flag is set, then the names will be returned in an
		576	order where likely directories come first. This is useful when
		577	you need to quickly find directories, or you want to find all
		578	directories while avoiding to stat() each entry.
		579
		580	If the system returns type information in readdir, then this is
		581	used to find directories directly. Otherwise, likely directories
		582	are files beginning with ".", or otherwise files with no dots,
		583	of which files with short names are tried first.
		584
		585	IO::AIO::READDIR_STAT_ORDER
		586	When this flag is set, then the names will be returned in an
		587	order suitable for stat()'ing each one. That is, when you plan
		588	to stat() all files in the given directory, then the returned
		589	order will likely be fastest.
		590
		591	If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
		592	specified, then the likely dirs come first, resulting in a less
		593	optimal stat order.
		594
		595	IO::AIO::READDIR_FOUND_UNKNOWN
		596	This flag should not be set when calling "aio_readdirx".
		597	Instead, it is being set by "aio_readdirx", when any of the
		598	$type's found were "IO::AIO::DT_UNKNOWN". The absense of this
		599	flag therefore indicates that all $type's are known, which can
		600	be used to speed up some algorithms.
		601
		602	aio_load $path, $data, $callback->($status)
		603	This is a composite request that tries to fully load the given file
		604	into memory. Status is the same as with aio_read.
389		605
390	aio_copy $srcpath, $dstpath, $callback->($status)	606	aio_copy $srcpath, $dstpath, $callback->($status)
391	Try to copy the file (directories not supported as either source	607	Try to copy the file (directories not supported as either source
392	or destination) from $srcpath to $dstpath and call the callback with	608	or destination) from $srcpath to $dstpath and call the callback with
393	the 0 (error) or -1 ok.	609	a status of 0 (ok) or -1 (error, see $!).
394		610
395	This is a composite request that it creates the destination file	611	This is a composite request that creates the destination file with
396	with mode 0200 and copies the contents of the source file into it	612	mode 0200 and copies the contents of the source file into it using
397	using "aio_sendfile", followed by restoring atime, mtime, access	613	"aio_sendfile", followed by restoring atime, mtime, access mode and
398	mode and uid/gid, in that order.	614	uid/gid, in that order.
399		615
400	If an error occurs, the partial destination file will be unlinked,	616	If an error occurs, the partial destination file will be unlinked,
401	if possible, except when setting atime, mtime, access mode and	617	if possible, except when setting atime, mtime, access mode and
402	uid/gid, where errors are being ignored.	618	uid/gid, where errors are being ignored.
403		619
404	aio_move $srcpath, $dstpath, $callback->($status)	620	aio_move $srcpath, $dstpath, $callback->($status)
405	Try to move the file (directories not supported as either source	621	Try to move the file (directories not supported as either source
406	or destination) from $srcpath to $dstpath and call the callback with	622	or destination) from $srcpath to $dstpath and call the callback with
407	the 0 (error) or -1 ok.	623	a status of 0 (ok) or -1 (error, see $!).
408		624
409	This is a composite request that tries to rename(2) the file first.	625	This is a composite request that tries to rename(2) the file first;
410	If rename files with "EXDEV", it copies the file with "aio_copy"	626	if rename fails with "EXDEV", it copies the file with "aio_copy"
411	and, if that is successful, unlinking the $srcpath.	627	and, if that is successful, unlinks the $srcpath.
412		628
413	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	629	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
414	Scans a directory (similar to "aio_readdir") but additionally tries	630	Scans a directory (similar to "aio_readdir") but additionally tries
415	to efficiently separate the entries of directory $path into two sets	631	to efficiently separate the entries of directory $path into two sets
416	of names, directories you can recurse into (directories), and ones	632	of names, directories you can recurse into (directories), and ones
…		…
436	Implementation notes.	652	Implementation notes.
437		653
438	The "aio_readdir" cannot be avoided, but "stat()"'ing every entry	654	The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
439	can.	655	can.
440		656
		657	If readdir returns file type information, then this is used directly
		658	to find directories.
		659
441	After reading the directory, the modification time, size etc. of the	660	Otherwise, after reading the directory, the modification time, size
442	directory before and after the readdir is checked, and if they match	661	etc. of the directory before and after the readdir is checked, and
443	(and isn't the current time), the link count will be used to decide	662	if they match (and isn't the current time), the link count will be
444	how many entries are directories (if >= 2). Otherwise, no knowledge	663	used to decide how many entries are directories (if >= 2).
445	of the number of subdirectories will be assumed.	664	Otherwise, no knowledge of the number of subdirectories will be
		665	assumed.
446		666
447	Then entries will be sorted into likely directories (everything	667	Then entries will be sorted into likely directories a non-initial
448	without a non-initial dot currently) and likely non-directories	668	dot currently) and likely non-directories (see "aio_readdirx"). Then
449	(everything else). Then every entry plus an appended "/." will be	669	every entry plus an appended "/." will be "stat"'ed, likely
450	"stat"'ed, likely directories first. If that succeeds, it assumes	670	directories first, in order of their inode numbers. If that
451	that the entry is a directory or a symlink to directory (which will	671	succeeds, it assumes that the entry is a directory or a symlink to
452	be checked seperately). This is often faster than stat'ing the entry	672	directory (which will be checked seperately). This is often faster
453	itself because filesystems might detect the type of the entry	673	than stat'ing the entry itself because filesystems might detect the
454	without reading the inode data (e.g. ext2fs filetype feature).	674	type of the entry without reading the inode data (e.g. ext2fs
		675	filetype feature), even on systems that cannot return the filetype
		676	information on readdir.
455		677
456	If the known number of directories (link count - 2) has been	678	If the known number of directories (link count - 2) has been
457	reached, the rest of the entries is assumed to be non-directories.	679	reached, the rest of the entries is assumed to be non-directories.
458		680
459	This only works with certainty on POSIX (= UNIX) filesystems, which	681	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
461		683
462	It will also likely work on non-POSIX filesystems with reduced	684	It will also likely work on non-POSIX filesystems with reduced
463	efficiency as those tend to return 0 or 1 as link counts, which	685	efficiency as those tend to return 0 or 1 as link counts, which
464	disables the directory counting heuristic.	686	disables the directory counting heuristic.
465		687
		688	aio_rmtree $path, $callback->($status)
		689	Delete a directory tree starting (and including) $path, return the
		690	status of the final "rmdir" only. This is a composite request that
		691	uses "aio_scandir" to recurse into and rmdir directories, and unlink
		692	everything else.
		693
		694	aio_sync $callback->($status)
		695	Asynchronously call sync and call the callback when finished.
		696
466	aio_fsync $fh, $callback->($status)	697	aio_fsync $fh, $callback->($status)
467	Asynchronously call fsync on the given filehandle and call the	698	Asynchronously call fsync on the given filehandle and call the
468	callback with the fsync result code.	699	callback with the fsync result code.
469		700
470	aio_fdatasync $fh, $callback->($status)	701	aio_fdatasync $fh, $callback->($status)
471	Asynchronously call fdatasync on the given filehandle and call the	702	Asynchronously call fdatasync on the given filehandle and call the
472	callback with the fdatasync result code.	703	callback with the fdatasync result code.
473		704
474	If this call isn't available because your OS lacks it or it couldn't	705	If this call isn't available because your OS lacks it or it couldn't
475	be detected, it will be emulated by calling "fsync" instead.	706	be detected, it will be emulated by calling "fsync" instead.
		707
		708	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		709	Sync the data portion of the file specified by $offset and $length
		710	to disk (but NOT the metadata), by calling the Linux-specific
		711	sync_file_range call. If sync_file_range is not available or it
		712	returns ENOSYS, then fdatasync or fsync is being substituted.
		713
		714	$flags can be a combination of
		715	"IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
		716	"IO::AIO::SYNC_FILE_RANGE_WRITE" and
		717	"IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
		718	manpage for details.
		719
		720	aio_pathsync $path, $callback->($status)
		721	This request tries to open, fsync and close the given path. This is
		722	a composite request intended to sync directories after directory
		723	operations (E.g. rename). This might not work on all operating
		724	systems or have any specific effect, but usually it makes sure that
		725	directory changes get written to disc. It works for anything that
		726	can be opened for read-only, not just directories.
		727
		728	Future versions of this function might fall back to other methods
		729	when "fsync" on the directory fails (such as calling "sync").
		730
		731	Passes 0 when everything went ok, and -1 on error.
		732
		733	aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
		734	$callback->($status)
		735	This is a rather advanced IO::AIO call, which only works on
		736	mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
		737	also works on data scalars managed by the Sys::Mmap or Mmap modules,
		738	note that the scalar must only be modified in-place while an aio
		739	operation is pending on it).
		740
		741	It calls the "msync" function of your OS, if available, with the
		742	memory area starting at $offset in the string and ending $length
		743	bytes later. If $length is negative, counts from the end, and if
		744	$length is "undef", then it goes till the end of the string. The
		745	flags can be a combination of "IO::AIO::MS_ASYNC",
		746	"IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
		747
		748	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
		749	$callback->($status)
		750	This is a rather advanced IO::AIO call, which works best on
		751	mmap(2)ed scalars.
		752
		753	It touches (reads or writes) all memory pages in the specified range
		754	inside the scalar. All caveats and parameters are the same as for
		755	"aio_msync", above, except for flags, which must be either 0 (which
		756	reads all pages and ensures they are instantiated) or
		757	"IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
		758	and writing an octet from it, which dirties the page).
		759
		760	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		761	This is a rather advanced IO::AIO call, which works best on
		762	mmap(2)ed scalars.
		763
		764	It reads in all the pages of the underlying storage into memory (if
		765	any) and locks them, so they are not getting swapped/paged out or
		766	removed.
		767
		768	If $length is undefined, then the scalar will be locked till the
		769	end.
		770
		771	On systems that do not implement "mlock", this function returns -1
		772	and sets errno to "ENOSYS".
		773
		774	Note that the corresponding "munlock" is synchronous and is
		775	documented under "MISCELLANEOUS FUNCTIONS".
		776
		777	Example: open a file, mmap and mlock it - both will be undone when
		778	$data gets destroyed.
		779
		780	open my $fh, "<", $path or die "$path: $!";
		781	my $data;
		782	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		783	aio_mlock $data; # mlock in background
		784
		785	aio_mlockall $flags, $callback->($status)
		786	Calls the "mlockall" function with the given $flags (a combination
		787	of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
		788
		789	On systems that do not implement "mlockall", this function returns
		790	-1 and sets errno to "ENOSYS".
		791
		792	Note that the corresponding "munlockall" is synchronous and is
		793	documented under "MISCELLANEOUS FUNCTIONS".
		794
		795	Example: asynchronously lock all current and future pages into
		796	memory.
		797
		798	aio_mlockall IO::AIO::MCL_FUTURE;
476		799
477	aio_group $callback->(...)	800	aio_group $callback->(...)
478	This is a very special aio request: Instead of doing something, it	801	This is a very special aio request: Instead of doing something, it
479	is a container for other aio requests, which is useful if you want	802	is a container for other aio requests, which is useful if you want
480	to bundle many requests into a single, composite, request with a	803	to bundle many requests into a single, composite, request with a
…		…
523		846
524	cancel $req	847	cancel $req
525	Cancels the request, if possible. Has the effect of skipping	848	Cancels the request, if possible. Has the effect of skipping
526	execution when entering the execute state and skipping calling the	849	execution when entering the execute state and skipping calling the
527	callback when entering the the result state, but will leave the	850	callback when entering the the result state, but will leave the
528	request otherwise untouched. That means that requests that currently	851	request otherwise untouched (with the exception of readdir). That
529	execute will not be stopped and resources held by the request will	852	means that requests that currently execute will not be stopped and
530	not be freed prematurely.	853	resources held by the request will not be freed prematurely.
531		854
532	cb $req $callback->(...)	855	cb $req $callback->(...)
533	Replace (or simply set) the callback registered to the request.	856	Replace (or simply set) the callback registered to the request.
534		857
535	IO::AIO::GRP CLASS	858	IO::AIO::GRP CLASS
…		…
562	};	885	};
563		886
564	This makes it very easy to create composite requests (see the source of	887	This makes it very easy to create composite requests (see the source of
565	"aio_move" for an application) that work and feel like simple requests.	888	"aio_move" for an application) that work and feel like simple requests.
566		889
567	* The IO::AIO::GRP objects will be cleaned up during calls to	890	* The IO::AIO::GRP objects will be cleaned up during calls to
568	"IO::AIO::poll_cb", just like any other request.	891	"IO::AIO::poll_cb", just like any other request.
		892
569	* They can be canceled like any other request. Canceling will cancel not	893	* They can be canceled like any other request. Canceling will cancel
570	only the request itself, but also all requests it contains.	894	not only the request itself, but also all requests it contains.
		895
571	* They can also can also be added to other IO::AIO::GRP objects.	896	* They can also can also be added to other IO::AIO::GRP objects.
		897
572	* You must not add requests to a group from within the group callback	898	* You must not add requests to a group from within the group callback
573	(or any later time).	899	(or any later time).
574		900
575	Their lifetime, simplified, looks like this: when they are empty, they	901	Their lifetime, simplified, looks like this: when they are empty, they
576	will finish very quickly. If they contain only requests that are in the	902	will finish very quickly. If they contain only requests that are in the
577	"done" state, they will also finish. Otherwise they will continue to	903	"done" state, they will also finish. Otherwise they will continue to
578	exist.	904	exist.
579		905
580	That means after creating a group you have some time to add requests.	906	That means after creating a group you have some time to add requests
581	And in the callbacks of those requests, you can add further requests to	907	(precisely before the callback has been invoked, which is only done
582	the group. And only when all those requests have finished will the the	908	within the "poll_cb"). And in the callbacks of those requests, you can
583	group itself finish.	909	add further requests to the group. And only when all those requests have
		910	finished will the the group itself finish.
584		911
585	add $grp ...	912	add $grp ...
586	$grp->add (...)	913	$grp->add (...)
587	Add one or more requests to the group. Any type of IO::AIO::REQ can	914	Add one or more requests to the group. Any type of IO::AIO::REQ can
588	be added, including other groups, as long as you do not create	915	be added, including other groups, as long as you do not create
…		…
593	$grp->cancel_subs	920	$grp->cancel_subs
594	Cancel all subrequests and clears any feeder, but not the group	921	Cancel all subrequests and clears any feeder, but not the group
595	request itself. Useful when you queued a lot of events but got a	922	request itself. Useful when you queued a lot of events but got a
596	result early.	923	result early.
597		924
		925	The group request will finish normally (you cannot add requests to
		926	the group).
		927
598	$grp->result (...)	928	$grp->result (...)
599	Set the result value(s) that will be passed to the group callback	929	Set the result value(s) that will be passed to the group callback
600	when all subrequests have finished and set thre groups errno to the	930	when all subrequests have finished and set the groups errno to the
601	current value of errno (just like calling "errno" without an error	931	current value of errno (just like calling "errno" without an error
602	number). By default, no argument will be passed and errno is zero.	932	number). By default, no argument will be passed and errno is zero.
603		933
604	$grp->errno ([$errno])	934	$grp->errno ([$errno])
605	Sets the group errno value to $errno, or the current value of errno	935	Sets the group errno value to $errno, or the current value of errno
…		…
631	does not impose any limits).	961	does not impose any limits).
632		962
633	If the feed does not queue more requests when called, it will be	963	If the feed does not queue more requests when called, it will be
634	automatically removed from the group.	964	automatically removed from the group.
635		965
636	If the feed limit is 0, it will be set to 2 automatically.	966	If the feed limit is 0 when this method is called, it will be set to
		967	2 automatically.
637		968
638	Example:	969	Example:
639		970
640	# stat all files in @files, but only ever use four aio requests concurrently:	971	# stat all files in @files, but only ever use four aio requests concurrently:
641		972
…		…
652	Sets the feeder limit for the group: The feeder will be called	983	Sets the feeder limit for the group: The feeder will be called
653	whenever the group contains less than this many requests.	984	whenever the group contains less than this many requests.
654		985
655	Setting the limit to 0 will pause the feeding process.	986	Setting the limit to 0 will pause the feeding process.
656		987
		988	The default value for the limit is 0, but note that setting a feeder
		989	automatically bumps it up to 2.
		990
657	SUPPORT FUNCTIONS	991	SUPPORT FUNCTIONS
658	EVENT PROCESSING AND EVENT LOOP INTEGRATION	992	EVENT PROCESSING AND EVENT LOOP INTEGRATION
659	$fileno = IO::AIO::poll_fileno	993	$fileno = IO::AIO::poll_fileno
660	Return the request result pipe file descriptor. This filehandle	994	Return the request result pipe file descriptor. This filehandle
661	must be polled for reading by some mechanism outside this module	995	must be polled for reading by some mechanism outside this module
662	(e.g. Event or select, see below or the SYNOPSIS). If the pipe	996	(e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
663	becomes readable you have to call "poll_cb" to check the results.	997	pipe becomes readable you have to call "poll_cb" to check the
		998	results.
664		999
665	See "poll_cb" for an example.	1000	See "poll_cb" for an example.
666		1001
667	IO::AIO::poll_cb	1002	IO::AIO::poll_cb
668	Process some outstanding events on the result pipe. You have to call	1003	Process some outstanding events on the result pipe. You have to call
669	this regularly. Returns the number of events processed. Returns	1004	this regularly. Returns 0 if all events could be processed, or -1 if
670	immediately when no events are outstanding. The amount of events	1005	it returned earlier for whatever reason. Returns immediately when no
		1006	events are outstanding. The amount of events processed depends on
671	processed depends on the settings of "IO::AIO::max_poll_req" and	1007	the settings of "IO::AIO::max_poll_req" and
672	"IO::AIO::max_poll_time".	1008	"IO::AIO::max_poll_time".
673		1009
674	If not all requests were processed for whatever reason, the	1010	If not all requests were processed for whatever reason, the
675	filehandle will still be ready when "poll_cb" returns.	1011	filehandle will still be ready when "poll_cb" returns, so normally
		1012	you don't have to do anything special to have it called later.
676		1013
677	Example: Install an Event watcher that automatically calls	1014	Example: Install an Event watcher that automatically calls
678	IO::AIO::poll_cb with high priority:	1015	IO::AIO::poll_cb with high priority (more examples can be found in
		1016	the SYNOPSIS section, at the top of this document):
679		1017
680	Event->io (fd => IO::AIO::poll_fileno,	1018	Event->io (fd => IO::AIO::poll_fileno,
681	poll => 'r', async => 1,	1019	poll => 'r', async => 1,
682	cb => \&IO::AIO::poll_cb);	1020	cb => \&IO::AIO::poll_cb);
		1021
		1022	IO::AIO::poll_wait
		1023	If there are any outstanding requests and none of them in the result
		1024	phase, wait till the result filehandle becomes ready for reading
		1025	(simply does a "select" on the filehandle. This is useful if you
		1026	want to synchronously wait for some requests to finish).
		1027
		1028	See "nreqs" for an example.
		1029
		1030	IO::AIO::poll
		1031	Waits until some requests have been handled.
		1032
		1033	Returns the number of requests processed, but is otherwise strictly
		1034	equivalent to:
		1035
		1036	IO::AIO::poll_wait, IO::AIO::poll_cb
		1037
		1038	IO::AIO::flush
		1039	Wait till all outstanding AIO requests have been handled.
		1040
		1041	Strictly equivalent to:
		1042
		1043	IO::AIO::poll_wait, IO::AIO::poll_cb
		1044	while IO::AIO::nreqs;
683		1045
684	IO::AIO::max_poll_reqs $nreqs	1046	IO::AIO::max_poll_reqs $nreqs
685	IO::AIO::max_poll_time $seconds	1047	IO::AIO::max_poll_time $seconds
686	These set the maximum number of requests (default 0, meaning	1048	These set the maximum number of requests (default 0, meaning
687	infinity) that are being processed by "IO::AIO::poll_cb" in one	1049	infinity) that are being processed by "IO::AIO::poll_cb" in one
…		…
711	# use a low priority so other tasks have priority	1073	# use a low priority so other tasks have priority
712	Event->io (fd => IO::AIO::poll_fileno,	1074	Event->io (fd => IO::AIO::poll_fileno,
713	poll => 'r', nice => 1,	1075	poll => 'r', nice => 1,
714	cb => &IO::AIO::poll_cb);	1076	cb => &IO::AIO::poll_cb);
715		1077
716	IO::AIO::poll_wait
717	If there are any outstanding requests and none of them in the result
718	phase, wait till the result filehandle becomes ready for reading
719	(simply does a "select" on the filehandle. This is useful if you
720	want to synchronously wait for some requests to finish).
721
722	See "nreqs" for an example.
723
724	IO::AIO::poll
725	Waits until some requests have been handled.
726
727	Returns the number of requests processed, but is otherwise strictly
728	equivalent to:
729
730	IO::AIO::poll_wait, IO::AIO::poll_cb
731
732	IO::AIO::flush
733	Wait till all outstanding AIO requests have been handled.
734
735	Strictly equivalent to:
736
737	IO::AIO::poll_wait, IO::AIO::poll_cb
738	while IO::AIO::nreqs;
739
740	CONTROLLING THE NUMBER OF THREADS	1078	CONTROLLING THE NUMBER OF THREADS
741	IO::AIO::min_parallel $nthreads	1079	IO::AIO::min_parallel $nthreads
742	Set the minimum number of AIO threads to $nthreads. The current	1080	Set the minimum number of AIO threads to $nthreads. The current
743	default is 8, which means eight asynchronous operations can execute	1081	default is 8, which means eight asynchronous operations can execute
744	concurrently at any one time (the number of outstanding requests,	1082	concurrently at any one time (the number of outstanding requests,
…		…
786		1124
787	The default is probably ok in most situations, especially if thread	1125	The default is probably ok in most situations, especially if thread
788	creation is fast. If thread creation is very slow on your system you	1126	creation is fast. If thread creation is very slow on your system you
789	might want to use larger values.	1127	might want to use larger values.
790		1128
791	$oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1129	IO::AIO::max_outstanding $maxreqs
792	This is a very bad function to use in interactive programs because	1130	This is a very bad function to use in interactive programs because
793	it blocks, and a bad way to reduce concurrency because it is	1131	it blocks, and a bad way to reduce concurrency because it is
794	inexact: Better use an "aio_group" together with a feed callback.	1132	inexact: Better use an "aio_group" together with a feed callback.
795		1133
796	Sets the maximum number of outstanding requests to $nreqs. If you to	1134	Sets the maximum number of outstanding requests to $nreqs. If you do
797	queue up more than this number of requests, the next call to the	1135	queue up more than this number of requests, the next call to the
798	"poll_cb" (and "poll_some" and other functions calling "poll_cb")	1136	"poll_cb" (and "poll_some" and other functions calling "poll_cb")
799	function will block until the limit is no longer exceeded.	1137	function will block until the limit is no longer exceeded.
800		1138
801	The default value is very large, so there is no practical limit on	1139	The default value is very large, so there is no practical limit on
802	the number of outstanding requests.	1140	the number of outstanding requests.
803		1141
804	You can still queue as many requests as you want. Therefore,	1142	You can still queue as many requests as you want. Therefore,
805	"max_oustsanding" is mainly useful in simple scripts (with low	1143	"max_outstanding" is mainly useful in simple scripts (with low
806	values) or as a stop gap to shield against fatal memory overflow	1144	values) or as a stop gap to shield against fatal memory overflow
807	(with large values).	1145	(with large values).
808		1146
809	STATISTICAL INFORMATION	1147	STATISTICAL INFORMATION
810	IO::AIO::nreqs	1148	IO::AIO::nreqs
…		…
822	executed).	1160	executed).
823		1161
824	IO::AIO::npending	1162	IO::AIO::npending
825	Returns the number of requests currently in the pending state	1163	Returns the number of requests currently in the pending state
826	(executed, but not yet processed by poll_cb).	1164	(executed, but not yet processed by poll_cb).
		1165
		1166	MISCELLANEOUS FUNCTIONS
		1167	IO::AIO implements some functions that might be useful, but are not
		1168	asynchronous.
		1169
		1170	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1171	Calls the "eio_sendfile_sync" function, which is like
		1172	"aio_sendfile", but is blocking (this makes most sense if you know
		1173	the input data is likely cached already and the output filehandle is
		1174	set to non-blocking operations).
		1175
		1176	Returns the number of bytes copied, or -1 on error.
		1177
		1178	IO::AIO::fadvise $fh, $offset, $len, $advice
		1179	Simply calls the "posix_fadvise" function (see its manpage for
		1180	details). The following advice constants are avaiable:
		1181	"IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
		1182	"IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
		1183	"IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
		1184
		1185	On systems that do not implement "posix_fadvise", this function
		1186	returns ENOSYS, otherwise the return value of "posix_fadvise".
		1187
		1188	IO::AIO::madvise $scalar, $offset, $len, $advice
		1189	Simply calls the "posix_madvise" function (see its manpage for
		1190	details). The following advice constants are avaiable:
		1191	"IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
		1192	"IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
		1193	"IO::AIO::MADV_DONTNEED".
		1194
		1195	On systems that do not implement "posix_madvise", this function
		1196	returns ENOSYS, otherwise the return value of "posix_madvise".
		1197
		1198	IO::AIO::mprotect $scalar, $offset, $len, $protect
		1199	Simply calls the "mprotect" function on the preferably AIO::mmap'ed
		1200	$scalar (see its manpage for details). The following protect
		1201	constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
		1202	"IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
		1203
		1204	On systems that do not implement "mprotect", this function returns
		1205	ENOSYS, otherwise the return value of "mprotect".
		1206
		1207	IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1208	Memory-maps a file (or anonymous memory range) and attaches it to
		1209	the given $scalar, which will act like a string scalar.
		1210
		1211	The only operations allowed on the scalar are "substr"/"vec" that
		1212	don't change the string length, and most read-only operations such
		1213	as copying it or searching it with regexes and so on.
		1214
		1215	Anything else is unsafe and will, at best, result in memory leaks.
		1216
		1217	The memory map associated with the $scalar is automatically removed
		1218	when the $scalar is destroyed, or when the "IO::AIO::mmap" or
		1219	"IO::AIO::munmap" functions are called.
		1220
		1221	This calls the "mmap"(2) function internally. See your system's
		1222	manual page for details on the $length, $prot and $flags parameters.
		1223
		1224	The $length must be larger than zero and smaller than the actual
		1225	filesize.
		1226
		1227	$prot is a combination of "IO::AIO::PROT_NONE",
		1228	"IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
		1229	"IO::AIO::PROT_WRITE",
		1230
		1231	$flags can be a combination of "IO::AIO::MAP_SHARED" or
		1232	"IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
		1233	not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
		1234	(which is set to "MAP_ANON" if your system only provides this
		1235	constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
		1236	"IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
		1237	"IO::AIO::MAP_NONBLOCK"
		1238
		1239	If $fh is "undef", then a file descriptor of -1 is passed.
		1240
		1241	$offset is the offset from the start of the file - it generally must
		1242	be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
		1243
		1244	Example:
		1245
		1246	use Digest::MD5;
		1247	use IO::AIO;
		1248
		1249	open my $fh, "<verybigfile"
		1250	or die "$!";
		1251
		1252	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1253	or die "verybigfile: $!";
		1254
		1255	my $fast_md5 = md5 $data;
		1256
		1257	IO::AIO::munmap $scalar
		1258	Removes a previous mmap and undefines the $scalar.
		1259
		1260	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1261	Calls the "munlock" function, undoing the effects of a previous
		1262	"aio_mlock" call (see its description for details).
		1263
		1264	IO::AIO::munlockall
		1265	Calls the "munlockall" function.
		1266
		1267	On systems that do not implement "munlockall", this function returns
		1268	ENOSYS, otherwise the return value of "munlockall".
		1269
		1270	EVENT LOOP INTEGRATION
		1271	It is recommended to use AnyEvent::AIO to integrate IO::AIO
		1272	automatically into many event loops:
		1273
		1274	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1275	use AnyEvent::AIO;
		1276
		1277	You can also integrate IO::AIO manually into many event loops, here are
		1278	some examples of how to do this:
		1279
		1280	# EV integration
		1281	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1282
		1283	# Event integration
		1284	Event->io (fd => IO::AIO::poll_fileno,
		1285	poll => 'r',
		1286	cb => \&IO::AIO::poll_cb);
		1287
		1288	# Glib/Gtk2 integration
		1289	add_watch Glib::IO IO::AIO::poll_fileno,
		1290	in => sub { IO::AIO::poll_cb; 1 };
		1291
		1292	# Tk integration
		1293	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1294	readable => \&IO::AIO::poll_cb);
		1295
		1296	# Danga::Socket integration
		1297	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1298	\&IO::AIO::poll_cb);
827		1299
828	FORK BEHAVIOUR	1300	FORK BEHAVIOUR
829	This module should do "the right thing" when the process using it forks:	1301	This module should do "the right thing" when the process using it forks:
830		1302
831	Before the fork, IO::AIO enters a quiescent state where no requests can	1303	Before the fork, IO::AIO enters a quiescent state where no requests can
…		…
847	bytes of memory. In addition, stat requests need a stat buffer (possibly	1319	bytes of memory. In addition, stat requests need a stat buffer (possibly
848	a few hundred bytes), readdir requires a result buffer and so on. Perl	1320	a few hundred bytes), readdir requires a result buffer and so on. Perl
849	scalars and other data passed into aio requests will also be locked and	1321	scalars and other data passed into aio requests will also be locked and
850	will consume memory till the request has entered the done state.	1322	will consume memory till the request has entered the done state.
851		1323
852	This is now awfully much, so queuing lots of requests is not usually a	1324	This is not awfully much, so queuing lots of requests is not usually a
853	problem.	1325	problem.
854		1326
855	Per-thread usage:	1327	Per-thread usage:
856		1328
857	In the execution phase, some aio requests require more memory for	1329	In the execution phase, some aio requests require more memory for
…		…
860		1332
861	KNOWN BUGS	1333	KNOWN BUGS
862	Known bugs will be fixed in the next release.	1334	Known bugs will be fixed in the next release.
863		1335
864	SEE ALSO	1336	SEE ALSO
865	Coro::AIO.	1337	AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
		1338	more natural syntax.
866		1339
867	AUTHOR	1340	AUTHOR
868	Marc Lehmann <schmorp@schmorp.de>	1341	Marc Lehmann <schmorp@schmorp.de>
869	http://home.schmorp.de/	1342	http://home.schmorp.de/
870		1343

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Comparing IO-AIO/README (file contents): Revision 1.21 by root, Fri Dec 22 04:05:50 2006 UTC vs. Revision 1.44 by root, Mon Nov 1 22:03:43 2010 UTC

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Comparing IO-AIO/README (file contents):
Revision 1.21 by root, Fri Dec 22 04:05:50 2006 UTC vs.
Revision 1.44 by root, Mon Nov 1 22:03:43 2010 UTC