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Revision 1.24 by root, Sun Jul 31 18:45:48 2005 UTC vs.
Revision 1.145 by root, Sun Apr 19 19:20:10 2009 UTC

…		…
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	# Event	21	# version 2+ has request and group objects
		22	use IO::AIO 2;
		23
		24	aioreq_pri 4; # give next request a very high priority
		25	my $req = aio_unlink "/tmp/file", sub { };
		26	$req->cancel; # cancel request if still in queue
		27
		28	my $grp = aio_group sub { print "all stats done\n" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		32	use AnyEvent::AIO;
		33
		34	# EV integration
		35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		36
		37	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	38	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	39	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	40	cb => \&IO::AIO::poll_cb);
24		41
25	# Glib/Gtk2	42	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	43	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb; 1 };	44	in => sub { IO::AIO::poll_cb; 1 };
28		45
29	# Tk	46	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	48	readable => \&IO::AIO::poll_cb);
32		49
33	# Danga::Socket	50	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	52	\&IO::AIO::poll_cb);
36		53
37
38	=head1 DESCRIPTION	54	=head1 DESCRIPTION
39		55
40	This module implements asynchronous I/O using whatever means your	56	This module implements asynchronous I/O using whatever means your
41	operating system supports.	57	operating system supports.
42		58
		59	Asynchronous means that operations that can normally block your program
		60	(e.g. reading from disk) will be done asynchronously: the operation
		61	will still block, but you can do something else in the meantime. This
		62	is extremely useful for programs that need to stay interactive even
		63	when doing heavy I/O (GUI programs, high performance network servers
		64	etc.), but can also be used to easily do operations in parallel that are
		65	normally done sequentially, e.g. stat'ing many files, which is much faster
		66	on a RAID volume or over NFS when you do a number of stat operations
		67	concurrently.
		68
		69	While most of this works on all types of file descriptors (for
		70	example sockets), using these functions on file descriptors that
		71	support nonblocking operation (again, sockets, pipes etc.) is very
		72	inefficient. Use an event loop for that (such as the L<Event|Event>
		73	module): IO::AIO will naturally fit into such an event loop itself.
		74
43	Currently, a number of threads are started that execute your read/writes	75	In this version, a number of threads are started that execute your
44	and signal their completion. You don't need thread support in your libc or	76	requests and signal their completion. You don't need thread support
45	perl, and the threads created by this module will not be visible to the	77	in perl, and the threads created by this module will not be visible
46	pthreads library. In the future, this module might make use of the native	78	to perl. In the future, this module might make use of the native aio
47	aio functions available on many operating systems. However, they are often	79	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	80	not well-supported or restricted (GNU/Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	81	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	82	aio_write, so the remaining functionality would have to be implemented
		83	using threads anyway.
51		84
52	Although the module will work with in the presence of other threads, it is	85	Although the module will work in the presence of other (Perl-) threads,
53	currently not reentrant, so use appropriate locking yourself, always call	86	it is currently not reentrant in any way, so use appropriate locking
54	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	87	yourself, always call C<poll_cb> from within the same thread, or never
55	C<aio_> functions) recursively.	88	call C<poll_cb> (or other C<aio_> functions) recursively.
		89
		90	=head2 EXAMPLE
		91
		92	This is a simple example that uses the Event module and loads
		93	F</etc/passwd> asynchronously:
		94
		95	use Fcntl;
		96	use Event;
		97	use IO::AIO;
		98
		99	# register the IO::AIO callback with Event
		100	Event->io (fd => IO::AIO::poll_fileno,
		101	poll => 'r',
		102	cb => \&IO::AIO::poll_cb);
		103
		104	# queue the request to open /etc/passwd
		105	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		106	my $fh = shift
		107	or die "error while opening: $!";
		108
		109	# stat'ing filehandles is generally non-blocking
		110	my $size = -s $fh;
		111
		112	# queue a request to read the file
		113	my $contents;
		114	aio_read $fh, 0, $size, $contents, 0, sub {
		115	$_[0] == $size
		116	or die "short read: $!";
		117
		118	close $fh;
		119
		120	# file contents now in $contents
		121	print $contents;
		122
		123	# exit event loop and program
		124	Event::unloop;
		125	};
		126	};
		127
		128	# possibly queue up other requests, or open GUI windows,
		129	# check for sockets etc. etc.
		130
		131	# process events as long as there are some:
		132	Event::loop;
		133
		134	=head1 REQUEST ANATOMY AND LIFETIME
		135
		136	Every C<aio_*> function creates a request. which is a C data structure not
		137	directly visible to Perl.
		138
		139	If called in non-void context, every request function returns a Perl
		140	object representing the request. In void context, nothing is returned,
		141	which saves a bit of memory.
		142
		143	The perl object is a fairly standard ref-to-hash object. The hash contents
		144	are not used by IO::AIO so you are free to store anything you like in it.
		145
		146	During their existance, aio requests travel through the following states,
		147	in order:
		148
		149	=over 4
		150
		151	=item ready
		152
		153	Immediately after a request is created it is put into the ready state,
		154	waiting for a thread to execute it.
		155
		156	=item execute
		157
		158	A thread has accepted the request for processing and is currently
		159	executing it (e.g. blocking in read).
		160
		161	=item pending
		162
		163	The request has been executed and is waiting for result processing.
		164
		165	While request submission and execution is fully asynchronous, result
		166	processing is not and relies on the perl interpreter calling C<poll_cb>
		167	(or another function with the same effect).
		168
		169	=item result
		170
		171	The request results are processed synchronously by C<poll_cb>.
		172
		173	The C<poll_cb> function will process all outstanding aio requests by
		174	calling their callbacks, freeing memory associated with them and managing
		175	any groups they are contained in.
		176
		177	=item done
		178
		179	Request has reached the end of its lifetime and holds no resources anymore
		180	(except possibly for the Perl object, but its connection to the actual
		181	aio request is severed and calling its methods will either do nothing or
		182	result in a runtime error).
		183
		184	=back
56		185
57	=cut	186	=cut
58		187
59	package IO::AIO;	188	package IO::AIO;
60		189
		190	use Carp ();
		191
61	no warnings;	192	no warnings;
		193	use strict 'vars';
62		194
63	use base 'Exporter';	195	use base 'Exporter';
64		196
65	use Fcntl ();
66
67	BEGIN {	197	BEGIN {
68	$VERSION = 1.1;	198	our $VERSION = '3.18';
69		199
70	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
71	aio_fsync aio_fdatasync aio_readahead);	201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir
72	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
		203	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
		204	aio_rename aio_link aio_move aio_copy aio_group
		205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		206	aio_chmod aio_utime aio_truncate);
		207
		208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		210	min_parallel max_parallel max_idle
		211	nreqs nready npending nthreads
		212	max_poll_time max_poll_reqs);
		213
		214	push @AIO_REQ, qw(aio_busy); # not exported
		215
		216	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
73		217
74	require XSLoader;	218	require XSLoader;
75	XSLoader::load IO::AIO, $VERSION;	219	XSLoader::load ("IO::AIO", $VERSION);
76	}	220	}
77		221
78	=head1 FUNCTIONS	222	=head1 FUNCTIONS
79		223
80	=head2 AIO FUNCTIONS	224	=head2 AIO REQUEST FUNCTIONS
81		225
82	All the C<aio_*> calls are more or less thin wrappers around the syscall	226	All the C<aio_*> calls are more or less thin wrappers around the syscall
83	with the same name (sans C<aio_>). The arguments are similar or identical,	227	with the same name (sans C<aio_>). The arguments are similar or identical,
84	and they all accept an additional (and optional) C<$callback> argument	228	and they all accept an additional (and optional) C<$callback> argument
85	which must be a code reference. This code reference will get called with	229	which must be a code reference. This code reference will get called with
86	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
87	perl, which usually delivers "false") as it's sole argument when the given	231	perl, which usually delivers "false") as its sole argument after the given
88	syscall has been executed asynchronously.	232	syscall has been executed asynchronously.
89		233
90	All functions expecting a filehandle keep a copy of the filehandle	234	All functions expecting a filehandle keep a copy of the filehandle
91	internally until the request has finished.	235	internally until the request has finished.
92		236
		237	All functions return request objects of type L<IO::AIO::REQ> that allow
		238	further manipulation of those requests while they are in-flight.
		239
93	The filenames you pass to these routines I<must> be absolute. The reason	240	The pathnames you pass to these routines I<must> be absolute and
94	for this is that at the time the request is being executed, the current	241	encoded as octets. The reason for the former is that at the time the
95	working directory could have changed. Alternatively, you can make sure	242	request is being executed, the current working directory could have
96	that you never change the current working directory.	243	changed. Alternatively, you can make sure that you never change the
		244	current working directory anywhere in the program and then use relative
		245	paths.
		246
		247	To encode pathnames as octets, either make sure you either: a) always pass
		248	in filenames you got from outside (command line, readdir etc.) without
		249	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		250	your pathnames to the locale (or other) encoding in effect in the user
		251	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		252	use something else to ensure your scalar has the correct contents.
		253
		254	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		255	handles correctly whether it is set or not.
97		256
98	=over 4	257	=over 4
99		258
		259	=item $prev_pri = aioreq_pri [$pri]
		260
		261	Returns the priority value that would be used for the next request and, if
		262	C<$pri> is given, sets the priority for the next aio request.
		263
		264	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		265	and C<4>, respectively. Requests with higher priority will be serviced
		266	first.
		267
		268	The priority will be reset to C<0> after each call to one of the C<aio_*>
		269	functions.
		270
		271	Example: open a file with low priority, then read something from it with
		272	higher priority so the read request is serviced before other low priority
		273	open requests (potentially spamming the cache):
		274
		275	aioreq_pri -3;
		276	aio_open ..., sub {
		277	return unless $_[0];
		278
		279	aioreq_pri -2;
		280	aio_read $_[0], ..., sub {
		281	...
		282	};
		283	};
		284
		285
		286	=item aioreq_nice $pri_adjust
		287
		288	Similar to C<aioreq_pri>, but subtracts the given value from the current
		289	priority, so the effect is cumulative.
		290
		291
100	=item aio_open $pathname, $flags, $mode, $callback	292	=item aio_open $pathname, $flags, $mode, $callback->($fh)
101		293
102	Asynchronously open or create a file and call the callback with a newly	294	Asynchronously open or create a file and call the callback with a newly
103	created filehandle for the file.	295	created filehandle for the file.
104		296
105	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	297	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
109	list. They are the same as used by C<sysopen>.	301	list. They are the same as used by C<sysopen>.
110		302
111	Likewise, C<$mode> specifies the mode of the newly created file, if it	303	Likewise, C<$mode> specifies the mode of the newly created file, if it
112	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	304	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
113	except that it is mandatory (i.e. use C<0> if you don't create new files,	305	except that it is mandatory (i.e. use C<0> if you don't create new files,
114	and C<0666> or C<0777> if you do).	306	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		307	by the umask in effect then the request is being executed, so better never
		308	change the umask.
115		309
116	Example:	310	Example:
117		311
118	aio_open "/etc/passwd", O_RDONLY, 0, sub {	312	aio_open "/etc/passwd", O_RDONLY, 0, sub {
119	if ($_[0]) {	313	if ($_[0]) {
…		…
122	} else {	316	} else {
123	die "open failed: $!\n";	317	die "open failed: $!\n";
124	}	318	}
125	};	319	};
126		320
		321
127	=item aio_close $fh, $callback	322	=item aio_close $fh, $callback->($status)
128		323
129	Asynchronously close a file and call the callback with the result	324	Asynchronously close a file and call the callback with the result
130	code. I<WARNING:> although accepted, you should not pass in a perl	325	code.
131	filehandle here, as perl will likely close the file descriptor another
132	time when the filehandle is destroyed. Normally, you can safely call perls
133	C<close> or just let filehandles go out of scope.
134		326
135	This is supposed to be a bug in the API, so that might change. It's	327	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
136	therefore best to avoid this function.	328	closing the file descriptor associated with the filehandle itself.
137		329
		330	Therefore, C<aio_close> will not close the filehandle - instead it will
		331	use dup2 to overwrite the file descriptor with the write-end of a pipe
		332	(the pipe fd will be created on demand and will be cached).
		333
		334	Or in other words: the file descriptor will be closed, but it will not be
		335	free for reuse until the perl filehandle is closed.
		336
		337	=cut
		338
138	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
139		340
140	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
141		342
142	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	343	Reads or writes C<$length> bytes from or to the specified C<$fh> and
143	into the scalar given by C<data> and offset C<dataoffset> and calls the	344	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
144	callback without the actual number of bytes read (or -1 on error, just	345	and calls the callback without the actual number of bytes read (or -1 on
145	like the syscall).	346	error, just like the syscall).
		347
		348	If C<$offset> is undefined, then the current file descriptor offset will
		349	be used (and updated), otherwise the file descriptor offset will not be
		350	changed by these calls.
		351
		352	If C<$length> is undefined in C<aio_write>, use the remaining length of
		353	C<$data>.
		354
		355	If C<$dataoffset> is less than zero, it will be counted from the end of
		356	C<$data>.
		357
		358	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		359	is outstanding. Modifying it can result in segfaults or World War III (if
		360	the necessary/optional hardware is installed).
146		361
147	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	362	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
148	offset C<0> within the scalar:	363	offset C<0> within the scalar:
149		364
150	aio_read $fh, 7, 15, $buffer, 0, sub {	365	aio_read $fh, 7, 15, $buffer, 0, sub {
151	$_[0] > 0 or die "read error: $!";	366	$_[0] > 0 or die "read error: $!";
152	print "read $_[0] bytes: <$buffer>\n";	367	print "read $_[0] bytes: <$buffer>\n";
153	};	368	};
154		369
		370
		371	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		372
		373	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		374	reading at byte offset C<$in_offset>, and starts writing at the current
		375	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		376	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		377	other.
		378
		379	This call tries to make use of a native C<sendfile> syscall to provide
		380	zero-copy operation. For this to work, C<$out_fh> should refer to a
		381	socket, and C<$in_fh> should refer to mmap'able file.
		382
		383	If the native sendfile call fails or is not implemented, it will be
		384	emulated, so you can call C<aio_sendfile> on any type of filehandle
		385	regardless of the limitations of the operating system.
		386
		387	Please note, however, that C<aio_sendfile> can read more bytes from
		388	C<$in_fh> than are written, and there is no way to find out how many
		389	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		390	provides the number of bytes written to C<$out_fh>. Only if the result
		391	value equals C<$length> one can assume that C<$length> bytes have been
		392	read.
		393
		394
155	=item aio_readahead $fh,$offset,$length, $callback	395	=item aio_readahead $fh,$offset,$length, $callback->($retval)
156
157	Asynchronously reads the specified byte range into the page cache, using
158	the C<readahead> syscall. If that syscall doesn't exist (likely if your OS
159	isn't Linux) the status will be C<-1> and C<$!> is set to C<ENOSYS>.
160		396
161	C<aio_readahead> populates the page cache with data from a file so that	397	C<aio_readahead> populates the page cache with data from a file so that
162	subsequent reads from that file will not block on disk I/O. The C<$offset>	398	subsequent reads from that file will not block on disk I/O. The C<$offset>
163	argument specifies the starting point from which data is to be read and	399	argument specifies the starting point from which data is to be read and
164	C<$length> specifies the number of bytes to be read. I/O is performed in	400	C<$length> specifies the number of bytes to be read. I/O is performed in
165	whole pages, so that offset is effectively rounded down to a page boundary	401	whole pages, so that offset is effectively rounded down to a page boundary
166	and bytes are read up to the next page boundary greater than or equal to	402	and bytes are read up to the next page boundary greater than or equal to
167	(off-set+length). C<aio_readahead> does not read beyond the end of the	403	(off-set+length). C<aio_readahead> does not read beyond the end of the
168	file. The current file offset of the file is left unchanged.	404	file. The current file offset of the file is left unchanged.
169		405
		406	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		407	emulated by simply reading the data, which would have a similar effect.
		408
		409
170	=item aio_stat $fh_or_path, $callback	410	=item aio_stat $fh_or_path, $callback->($status)
171		411
172	=item aio_lstat $fh, $callback	412	=item aio_lstat $fh, $callback->($status)
173		413
174	Works like perl's C<stat> or C<lstat> in void context. The callback will	414	Works like perl's C<stat> or C<lstat> in void context. The callback will
175	be called after the stat and the results will be available using C<stat _>	415	be called after the stat and the results will be available using C<stat _>
176	or C<-s _> etc...	416	or C<-s _> etc...
177		417
…		…
187	aio_stat "/etc/passwd", sub {	427	aio_stat "/etc/passwd", sub {
188	$_[0] and die "stat failed: $!";	428	$_[0] and die "stat failed: $!";
189	print "size is ", -s _, "\n";	429	print "size is ", -s _, "\n";
190	};	430	};
191		431
		432
		433	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		434
		435	Works like perl's C<utime> function (including the special case of $atime
		436	and $mtime being undef). Fractional times are supported if the underlying
		437	syscalls support them.
		438
		439	When called with a pathname, uses utimes(2) if available, otherwise
		440	utime(2). If called on a file descriptor, uses futimes(2) if available,
		441	otherwise returns ENOSYS, so this is not portable.
		442
		443	Examples:
		444
		445	# set atime and mtime to current time (basically touch(1)):
		446	aio_utime "path", undef, undef;
		447	# set atime to current time and mtime to beginning of the epoch:
		448	aio_utime "path", time, undef; # undef==0
		449
		450
		451	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		452
		453	Works like perl's C<chown> function, except that C<undef> for either $uid
		454	or $gid is being interpreted as "do not change" (but -1 can also be used).
		455
		456	Examples:
		457
		458	# same as "chown root path" in the shell:
		459	aio_chown "path", 0, -1;
		460	# same as above:
		461	aio_chown "path", 0, undef;
		462
		463
		464	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		465
		466	Works like truncate(2) or ftruncate(2).
		467
		468
		469	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		470
		471	Works like perl's C<chmod> function.
		472
		473
192	=item aio_unlink $pathname, $callback	474	=item aio_unlink $pathname, $callback->($status)
193		475
194	Asynchronously unlink (delete) a file and call the callback with the	476	Asynchronously unlink (delete) a file and call the callback with the
195	result code.	477	result code.
196		478
		479
		480	=item aio_mknod $path, $mode, $dev, $callback->($status)
		481
		482	[EXPERIMENTAL]
		483
		484	Asynchronously create a device node (or fifo). See mknod(2).
		485
		486	The only (POSIX-) portable way of calling this function is:
		487
		488	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		489
		490
		491	=item aio_link $srcpath, $dstpath, $callback->($status)
		492
		493	Asynchronously create a new link to the existing object at C<$srcpath> at
		494	the path C<$dstpath> and call the callback with the result code.
		495
		496
		497	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		498
		499	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		500	the path C<$dstpath> and call the callback with the result code.
		501
		502
		503	=item aio_readlink $path, $callback->($link)
		504
		505	Asynchronously read the symlink specified by C<$path> and pass it to
		506	the callback. If an error occurs, nothing or undef gets passed to the
		507	callback.
		508
		509
		510	=item aio_rename $srcpath, $dstpath, $callback->($status)
		511
		512	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		513	rename(2) and call the callback with the result code.
		514
		515
		516	=item aio_mkdir $pathname, $mode, $callback->($status)
		517
		518	Asynchronously mkdir (create) a directory and call the callback with
		519	the result code. C<$mode> will be modified by the umask at the time the
		520	request is executed, so do not change your umask.
		521
		522
		523	=item aio_rmdir $pathname, $callback->($status)
		524
		525	Asynchronously rmdir (delete) a directory and call the callback with the
		526	result code.
		527
		528
		529	=item aio_readdir $pathname, $callback->($entries)
		530
		531	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		532	directory (i.e. opendir + readdir + closedir). The entries will not be
		533	sorted, and will B<NOT> include the C<.> and C<..> entries.
		534
		535	The callback a single argument which is either C<undef> or an array-ref
		536	with the filenames.
		537
		538
		539	=item aio_load $path, $data, $callback->($status)
		540
		541	This is a composite request that tries to fully load the given file into
		542	memory. Status is the same as with aio_read.
		543
		544	=cut
		545
		546	sub aio_load($$;$) {
		547	my ($path, undef, $cb) = @_;
		548	my $data = \$_[1];
		549
		550	my $pri = aioreq_pri;
		551	my $grp = aio_group $cb;
		552
		553	aioreq_pri $pri;
		554	add $grp aio_open $path, O_RDONLY, 0, sub {
		555	my $fh = shift
		556	or return $grp->result (-1);
		557
		558	aioreq_pri $pri;
		559	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		560	$grp->result ($_[0]);
		561	};
		562	};
		563
		564	$grp
		565	}
		566
		567	=item aio_copy $srcpath, $dstpath, $callback->($status)
		568
		569	Try to copy the I<file> (directories not supported as either source or
		570	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		571	the C<0> (error) or C<-1> ok.
		572
		573	This is a composite request that creates the destination file with
		574	mode 0200 and copies the contents of the source file into it using
		575	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		576	uid/gid, in that order.
		577
		578	If an error occurs, the partial destination file will be unlinked, if
		579	possible, except when setting atime, mtime, access mode and uid/gid, where
		580	errors are being ignored.
		581
		582	=cut
		583
		584	sub aio_copy($$;$) {
		585	my ($src, $dst, $cb) = @_;
		586
		587	my $pri = aioreq_pri;
		588	my $grp = aio_group $cb;
		589
		590	aioreq_pri $pri;
		591	add $grp aio_open $src, O_RDONLY, 0, sub {
		592	if (my $src_fh = $_[0]) {
		593	my @stat = stat $src_fh;
		594
		595	aioreq_pri $pri;
		596	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		597	if (my $dst_fh = $_[0]) {
		598	aioreq_pri $pri;
		599	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		600	if ($_[0] == $stat[7]) {
		601	$grp->result (0);
		602	close $src_fh;
		603
		604	# those should not normally block. should. should.
		605	utime $stat[8], $stat[9], $dst;
		606	chmod $stat[2] & 07777, $dst_fh;
		607	chown $stat[4], $stat[5], $dst_fh;
		608
		609	aioreq_pri $pri;
		610	add $grp aio_close $dst_fh;
		611	} else {
		612	$grp->result (-1);
		613	close $src_fh;
		614	close $dst_fh;
		615
		616	aioreq $pri;
		617	add $grp aio_unlink $dst;
		618	}
		619	};
		620	} else {
		621	$grp->result (-1);
		622	}
		623	},
		624
		625	} else {
		626	$grp->result (-1);
		627	}
		628	};
		629
		630	$grp
		631	}
		632
		633	=item aio_move $srcpath, $dstpath, $callback->($status)
		634
		635	Try to move the I<file> (directories not supported as either source or
		636	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		637	the C<0> (error) or C<-1> ok.
		638
		639	This is a composite request that tries to rename(2) the file first; if
		640	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		641	that is successful, unlinks the C<$srcpath>.
		642
		643	=cut
		644
		645	sub aio_move($$;$) {
		646	my ($src, $dst, $cb) = @_;
		647
		648	my $pri = aioreq_pri;
		649	my $grp = aio_group $cb;
		650
		651	aioreq_pri $pri;
		652	add $grp aio_rename $src, $dst, sub {
		653	if ($_[0] && $! == EXDEV) {
		654	aioreq_pri $pri;
		655	add $grp aio_copy $src, $dst, sub {
		656	$grp->result ($_[0]);
		657
		658	if (!$_[0]) {
		659	aioreq_pri $pri;
		660	add $grp aio_unlink $src;
		661	}
		662	};
		663	} else {
		664	$grp->result ($_[0]);
		665	}
		666	};
		667
		668	$grp
		669	}
		670
		671	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		672
		673	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		674	efficiently separate the entries of directory C<$path> into two sets of
		675	names, directories you can recurse into (directories), and ones you cannot
		676	recurse into (everything else, including symlinks to directories).
		677
		678	C<aio_scandir> is a composite request that creates of many sub requests_
		679	C<$maxreq> specifies the maximum number of outstanding aio requests that
		680	this function generates. If it is C<< <= 0 >>, then a suitable default
		681	will be chosen (currently 4).
		682
		683	On error, the callback is called without arguments, otherwise it receives
		684	two array-refs with path-relative entry names.
		685
		686	Example:
		687
		688	aio_scandir $dir, 0, sub {
		689	my ($dirs, $nondirs) = @_;
		690	print "real directories: @$dirs\n";
		691	print "everything else: @$nondirs\n";
		692	};
		693
		694	Implementation notes.
		695
		696	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		697
		698	After reading the directory, the modification time, size etc. of the
		699	directory before and after the readdir is checked, and if they match (and
		700	isn't the current time), the link count will be used to decide how many
		701	entries are directories (if >= 2). Otherwise, no knowledge of the number
		702	of subdirectories will be assumed.
		703
		704	Then entries will be sorted into likely directories (everything without
		705	a non-initial dot currently) and likely non-directories (everything
		706	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		707	likely directories first. If that succeeds, it assumes that the entry
		708	is a directory or a symlink to directory (which will be checked
		709	seperately). This is often faster than stat'ing the entry itself because
		710	filesystems might detect the type of the entry without reading the inode
		711	data (e.g. ext2fs filetype feature).
		712
		713	If the known number of directories (link count - 2) has been reached, the
		714	rest of the entries is assumed to be non-directories.
		715
		716	This only works with certainty on POSIX (= UNIX) filesystems, which
		717	fortunately are the vast majority of filesystems around.
		718
		719	It will also likely work on non-POSIX filesystems with reduced efficiency
		720	as those tend to return 0 or 1 as link counts, which disables the
		721	directory counting heuristic.
		722
		723	=cut
		724
		725	sub aio_scandir($$;$) {
		726	my ($path, $maxreq, $cb) = @_;
		727
		728	my $pri = aioreq_pri;
		729
		730	my $grp = aio_group $cb;
		731
		732	$maxreq = 4 if $maxreq <= 0;
		733
		734	# stat once
		735	aioreq_pri $pri;
		736	add $grp aio_stat $path, sub {
		737	return $grp->result () if $_[0];
		738	my $now = time;
		739	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		740
		741	# read the directory entries
		742	aioreq_pri $pri;
		743	add $grp aio_readdir $path, sub {
		744	my $entries = shift
		745	or return $grp->result ();
		746
		747	# stat the dir another time
		748	aioreq_pri $pri;
		749	add $grp aio_stat $path, sub {
		750	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		751
		752	my $ndirs;
		753
		754	# take the slow route if anything looks fishy
		755	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		756	$ndirs = -1;
		757	} else {
		758	# if nlink == 2, we are finished
		759	# on non-posix-fs's, we rely on nlink < 2
		760	$ndirs = (stat _)[3] - 2
		761	or return $grp->result ([], $entries);
		762	}
		763
		764	# sort into likely dirs and likely nondirs
		765	# dirs == files without ".", short entries first
		766	$entries = [map $_->[0],
		767	sort { $b->[1] cmp $a->[1] }
		768	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		769	@$entries];
		770
		771	my (@dirs, @nondirs);
		772
		773	my $statgrp = add $grp aio_group sub {
		774	$grp->result (\@dirs, \@nondirs);
		775	};
		776
		777	limit $statgrp $maxreq;
		778	feed $statgrp sub {
		779	return unless @$entries;
		780	my $entry = pop @$entries;
		781
		782	aioreq_pri $pri;
		783	add $statgrp aio_stat "$path/$entry/.", sub {
		784	if ($_[0] < 0) {
		785	push @nondirs, $entry;
		786	} else {
		787	# need to check for real directory
		788	aioreq_pri $pri;
		789	add $statgrp aio_lstat "$path/$entry", sub {
		790	if (-d _) {
		791	push @dirs, $entry;
		792
		793	unless (--$ndirs) {
		794	push @nondirs, @$entries;
		795	feed $statgrp;
		796	}
		797	} else {
		798	push @nondirs, $entry;
		799	}
		800	}
		801	}
		802	};
		803	};
		804	};
		805	};
		806	};
		807
		808	$grp
		809	}
		810
		811	=item aio_rmtree $path, $callback->($status)
		812
		813	Delete a directory tree starting (and including) C<$path>, return the
		814	status of the final C<rmdir> only. This is a composite request that
		815	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		816	everything else.
		817
		818	=cut
		819
		820	sub aio_rmtree;
		821	sub aio_rmtree($;$) {
		822	my ($path, $cb) = @_;
		823
		824	my $pri = aioreq_pri;
		825	my $grp = aio_group $cb;
		826
		827	aioreq_pri $pri;
		828	add $grp aio_scandir $path, 0, sub {
		829	my ($dirs, $nondirs) = @_;
		830
		831	my $dirgrp = aio_group sub {
		832	add $grp aio_rmdir $path, sub {
		833	$grp->result ($_[0]);
		834	};
		835	};
		836
		837	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		838	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		839
		840	add $grp $dirgrp;
		841	};
		842
		843	$grp
		844	}
		845
		846	=item aio_sync $callback->($status)
		847
		848	Asynchronously call sync and call the callback when finished.
		849
197	=item aio_fsync $fh, $callback	850	=item aio_fsync $fh, $callback->($status)
198		851
199	Asynchronously call fsync on the given filehandle and call the callback	852	Asynchronously call fsync on the given filehandle and call the callback
200	with the fsync result code.	853	with the fsync result code.
201		854
202	=item aio_fdatasync $fh, $callback	855	=item aio_fdatasync $fh, $callback->($status)
203		856
204	Asynchronously call fdatasync on the given filehandle and call the	857	Asynchronously call fdatasync on the given filehandle and call the
205	callback with the fdatasync result code. Might set C<$!> to C<ENOSYS> if	858	callback with the fdatasync result code.
206	C<fdatasync> is not available.	859
		860	If this call isn't available because your OS lacks it or it couldn't be
		861	detected, it will be emulated by calling C<fsync> instead.
		862
		863	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		864
		865	Sync the data portion of the file specified by C<$offset> and C<$length>
		866	to disk (but NOT the metadata), by calling the Linux-specific
		867	sync_file_range call. If sync_file_range is not available or it returns
		868	ENOSYS, then fdatasync or fsync is being substituted.
		869
		870	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		871	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		872	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		873	manpage for details.
		874
		875	=item aio_pathsync $path, $callback->($status)
		876
		877	This request tries to open, fsync and close the given path. This is a
		878	composite request intended to sync directories after directory operations
		879	(E.g. rename). This might not work on all operating systems or have any
		880	specific effect, but usually it makes sure that directory changes get
		881	written to disc. It works for anything that can be opened for read-only,
		882	not just directories.
		883
		884	Passes C<0> when everything went ok, and C<-1> on error.
		885
		886	=cut
		887
		888	sub aio_pathsync($;$) {
		889	my ($path, $cb) = @_;
		890
		891	my $pri = aioreq_pri;
		892	my $grp = aio_group $cb;
		893
		894	aioreq_pri $pri;
		895	add $grp aio_open $path, O_RDONLY, 0, sub {
		896	my ($fh) = @_;
		897	if ($fh) {
		898	aioreq_pri $pri;
		899	add $grp aio_fsync $fh, sub {
		900	$grp->result ($_[0]);
		901
		902	aioreq_pri $pri;
		903	add $grp aio_close $fh;
		904	};
		905	} else {
		906	$grp->result (-1);
		907	}
		908	};
		909
		910	$grp
		911	}
		912
		913	=item aio_group $callback->(...)
		914
		915	This is a very special aio request: Instead of doing something, it is a
		916	container for other aio requests, which is useful if you want to bundle
		917	many requests into a single, composite, request with a definite callback
		918	and the ability to cancel the whole request with its subrequests.
		919
		920	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		921	for more info.
		922
		923	Example:
		924
		925	my $grp = aio_group sub {
		926	print "all stats done\n";
		927	};
		928
		929	add $grp
		930	(aio_stat ...),
		931	(aio_stat ...),
		932	...;
		933
		934	=item aio_nop $callback->()
		935
		936	This is a special request - it does nothing in itself and is only used for
		937	side effects, such as when you want to add a dummy request to a group so
		938	that finishing the requests in the group depends on executing the given
		939	code.
		940
		941	While this request does nothing, it still goes through the execution
		942	phase and still requires a worker thread. Thus, the callback will not
		943	be executed immediately but only after other requests in the queue have
		944	entered their execution phase. This can be used to measure request
		945	latency.
		946
		947	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		948
		949	Mainly used for debugging and benchmarking, this aio request puts one of
		950	the request workers to sleep for the given time.
		951
		952	While it is theoretically handy to have simple I/O scheduling requests
		953	like sleep and file handle readable/writable, the overhead this creates is
		954	immense (it blocks a thread for a long time) so do not use this function
		955	except to put your application under artificial I/O pressure.
207		956
208	=back	957	=back
209		958
		959	=head2 IO::AIO::REQ CLASS
		960
		961	All non-aggregate C<aio_*> functions return an object of this class when
		962	called in non-void context.
		963
		964	=over 4
		965
		966	=item cancel $req
		967
		968	Cancels the request, if possible. Has the effect of skipping execution
		969	when entering the B<execute> state and skipping calling the callback when
		970	entering the the B<result> state, but will leave the request otherwise
		971	untouched. That means that requests that currently execute will not be
		972	stopped and resources held by the request will not be freed prematurely.
		973
		974	=item cb $req $callback->(...)
		975
		976	Replace (or simply set) the callback registered to the request.
		977
		978	=back
		979
		980	=head2 IO::AIO::GRP CLASS
		981
		982	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		983	objects of this class, too.
		984
		985	A IO::AIO::GRP object is a special request that can contain multiple other
		986	aio requests.
		987
		988	You create one by calling the C<aio_group> constructing function with a
		989	callback that will be called when all contained requests have entered the
		990	C<done> state:
		991
		992	my $grp = aio_group sub {
		993	print "all requests are done\n";
		994	};
		995
		996	You add requests by calling the C<add> method with one or more
		997	C<IO::AIO::REQ> objects:
		998
		999	$grp->add (aio_unlink "...");
		1000
		1001	add $grp aio_stat "...", sub {
		1002	$_[0] or return $grp->result ("error");
		1003
		1004	# add another request dynamically, if first succeeded
		1005	add $grp aio_open "...", sub {
		1006	$grp->result ("ok");
		1007	};
		1008	};
		1009
		1010	This makes it very easy to create composite requests (see the source of
		1011	C<aio_move> for an application) that work and feel like simple requests.
		1012
		1013	=over 4
		1014
		1015	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1016	C<IO::AIO::poll_cb>, just like any other request.
		1017
		1018	=item * They can be canceled like any other request. Canceling will cancel not
		1019	only the request itself, but also all requests it contains.
		1020
		1021	=item * They can also can also be added to other IO::AIO::GRP objects.
		1022
		1023	=item * You must not add requests to a group from within the group callback (or
		1024	any later time).
		1025
		1026	=back
		1027
		1028	Their lifetime, simplified, looks like this: when they are empty, they
		1029	will finish very quickly. If they contain only requests that are in the
		1030	C<done> state, they will also finish. Otherwise they will continue to
		1031	exist.
		1032
		1033	That means after creating a group you have some time to add requests
		1034	(precisely before the callback has been invoked, which is only done within
		1035	the C<poll_cb>). And in the callbacks of those requests, you can add
		1036	further requests to the group. And only when all those requests have
		1037	finished will the the group itself finish.
		1038
		1039	=over 4
		1040
		1041	=item add $grp ...
		1042
		1043	=item $grp->add (...)
		1044
		1045	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1046	be added, including other groups, as long as you do not create circular
		1047	dependencies.
		1048
		1049	Returns all its arguments.
		1050
		1051	=item $grp->cancel_subs
		1052
		1053	Cancel all subrequests and clears any feeder, but not the group request
		1054	itself. Useful when you queued a lot of events but got a result early.
		1055
		1056	=item $grp->result (...)
		1057
		1058	Set the result value(s) that will be passed to the group callback when all
		1059	subrequests have finished and set the groups errno to the current value
		1060	of errno (just like calling C<errno> without an error number). By default,
		1061	no argument will be passed and errno is zero.
		1062
		1063	=item $grp->errno ([$errno])
		1064
		1065	Sets the group errno value to C<$errno>, or the current value of errno
		1066	when the argument is missing.
		1067
		1068	Every aio request has an associated errno value that is restored when
		1069	the callback is invoked. This method lets you change this value from its
		1070	default (0).
		1071
		1072	Calling C<result> will also set errno, so make sure you either set C<$!>
		1073	before the call to C<result>, or call c<errno> after it.
		1074
		1075	=item feed $grp $callback->($grp)
		1076
		1077	Sets a feeder/generator on this group: every group can have an attached
		1078	generator that generates requests if idle. The idea behind this is that,
		1079	although you could just queue as many requests as you want in a group,
		1080	this might starve other requests for a potentially long time. For example,
		1081	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,
		1082	delaying any later requests for a long time.
		1083
		1084	To avoid this, and allow incremental generation of requests, you can
		1085	instead a group and set a feeder on it that generates those requests. The
		1086	feed callback will be called whenever there are few enough (see C<limit>,
		1087	below) requests active in the group itself and is expected to queue more
		1088	requests.
		1089
		1090	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1091	not impose any limits).
		1092
		1093	If the feed does not queue more requests when called, it will be
		1094	automatically removed from the group.
		1095
		1096	If the feed limit is C<0> when this method is called, it will be set to
		1097	C<2> automatically.
		1098
		1099	Example:
		1100
		1101	# stat all files in @files, but only ever use four aio requests concurrently:
		1102
		1103	my $grp = aio_group sub { print "finished\n" };
		1104	limit $grp 4;
		1105	feed $grp sub {
		1106	my $file = pop @files
		1107	or return;
		1108
		1109	add $grp aio_stat $file, sub { ... };
		1110	};
		1111
		1112	=item limit $grp $num
		1113
		1114	Sets the feeder limit for the group: The feeder will be called whenever
		1115	the group contains less than this many requests.
		1116
		1117	Setting the limit to C<0> will pause the feeding process.
		1118
		1119	The default value for the limit is C<0>, but note that setting a feeder
		1120	automatically bumps it up to C<2>.
		1121
		1122	=back
		1123
210	=head2 SUPPORT FUNCTIONS	1124	=head2 SUPPORT FUNCTIONS
		1125
		1126	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
211		1127
212	=over 4	1128	=over 4
213		1129
214	=item $fileno = IO::AIO::poll_fileno	1130	=item $fileno = IO::AIO::poll_fileno
215		1131
…		…
220		1136
221	See C<poll_cb> for an example.	1137	See C<poll_cb> for an example.
222		1138
223	=item IO::AIO::poll_cb	1139	=item IO::AIO::poll_cb
224		1140
225	Process all outstanding events on the result pipe. You have to call this	1141	Process some outstanding events on the result pipe. You have to call this
226	regularly. Returns the number of events processed. Returns immediately	1142	regularly. Returns C<0> if all events could be processed, or C<-1> if it
227	when no events are outstanding.	1143	returned earlier for whatever reason. Returns immediately when no events
		1144	are outstanding. The amount of events processed depends on the settings of
		1145	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1146
		1147	If not all requests were processed for whatever reason, the filehandle
		1148	will still be ready when C<poll_cb> returns, so normally you don't have to
		1149	do anything special to have it called later.
228		1150
229	Example: Install an Event watcher that automatically calls	1151	Example: Install an Event watcher that automatically calls
230	IO::AIO::poll_cb with high priority:	1152	IO::AIO::poll_cb with high priority:
231		1153
232	Event->io (fd => IO::AIO::poll_fileno,	1154	Event->io (fd => IO::AIO::poll_fileno,
233	poll => 'r', async => 1,	1155	poll => 'r', async => 1,
234	cb => \&IO::AIO::poll_cb);	1156	cb => \&IO::AIO::poll_cb);
235		1157
		1158	=item IO::AIO::max_poll_reqs $nreqs
		1159
		1160	=item IO::AIO::max_poll_time $seconds
		1161
		1162	These set the maximum number of requests (default C<0>, meaning infinity)
		1163	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1164	the maximum amount of time (default C<0>, meaning infinity) spent in
		1165	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1166	of time C<poll_cb> is allowed to use).
		1167
		1168	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1169	syscall per request processed, which is not normally a problem unless your
		1170	callbacks are really really fast or your OS is really really slow (I am
		1171	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1172
		1173	Setting these is useful if you want to ensure some level of
		1174	interactiveness when perl is not fast enough to process all requests in
		1175	time.
		1176
		1177	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1178
		1179	Example: Install an Event watcher that automatically calls
		1180	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1181	program get the CPU sometimes even under high AIO load.
		1182
		1183	# try not to spend much more than 0.1s in poll_cb
		1184	IO::AIO::max_poll_time 0.1;
		1185
		1186	# use a low priority so other tasks have priority
		1187	Event->io (fd => IO::AIO::poll_fileno,
		1188	poll => 'r', nice => 1,
		1189	cb => &IO::AIO::poll_cb);
		1190
236	=item IO::AIO::poll_wait	1191	=item IO::AIO::poll_wait
237		1192
		1193	If there are any outstanding requests and none of them in the result
238	Wait till the result filehandle becomes ready for reading (simply does a	1194	phase, wait till the result filehandle becomes ready for reading (simply
239	C<select> on the filehandle. This is useful if you want to synchronously wait	1195	does a C<select> on the filehandle. This is useful if you want to
240	for some requests to finish).	1196	synchronously wait for some requests to finish).
241		1197
242	See C<nreqs> for an example.	1198	See C<nreqs> for an example.
243		1199
		1200	=item IO::AIO::poll
		1201
		1202	Waits until some requests have been handled.
		1203
		1204	Returns the number of requests processed, but is otherwise strictly
		1205	equivalent to:
		1206
		1207	IO::AIO::poll_wait, IO::AIO::poll_cb
		1208
244	=item IO::AIO::nreqs	1209	=item IO::AIO::flush
245		1210
246	Returns the number of requests currently outstanding (i.e. for which their	1211	Wait till all outstanding AIO requests have been handled.
247	callback has not been invoked yet).
248		1212
249	Example: wait till there are no outstanding requests anymore:	1213	Strictly equivalent to:
250		1214
251	IO::AIO::poll_wait, IO::AIO::poll_cb	1215	IO::AIO::poll_wait, IO::AIO::poll_cb
252	while IO::AIO::nreqs;	1216	while IO::AIO::nreqs;
253		1217
		1218	=back
		1219
		1220	=head3 CONTROLLING THE NUMBER OF THREADS
		1221
		1222	=over
		1223
		1224	=item IO::AIO::min_parallel $nthreads
		1225
		1226	Set the minimum number of AIO threads to C<$nthreads>. The current
		1227	default is C<8>, which means eight asynchronous operations can execute
		1228	concurrently at any one time (the number of outstanding requests,
		1229	however, is unlimited).
		1230
		1231	IO::AIO starts threads only on demand, when an AIO request is queued and
		1232	no free thread exists. Please note that queueing up a hundred requests can
		1233	create demand for a hundred threads, even if it turns out that everything
		1234	is in the cache and could have been processed faster by a single thread.
		1235
		1236	It is recommended to keep the number of threads relatively low, as some
		1237	Linux kernel versions will scale negatively with the number of threads
		1238	(higher parallelity => MUCH higher latency). With current Linux 2.6
		1239	versions, 4-32 threads should be fine.
		1240
		1241	Under most circumstances you don't need to call this function, as the
		1242	module selects a default that is suitable for low to moderate load.
		1243
		1244	=item IO::AIO::max_parallel $nthreads
		1245
		1246	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		1247	specified number of threads are currently running, this function kills
		1248	them. This function blocks until the limit is reached.
		1249
		1250	While C<$nthreads> are zero, aio requests get queued but not executed
		1251	until the number of threads has been increased again.
		1252
		1253	This module automatically runs C<max_parallel 0> at program end, to ensure
		1254	that all threads are killed and that there are no outstanding requests.
		1255
		1256	Under normal circumstances you don't need to call this function.
		1257
		1258	=item IO::AIO::max_idle $nthreads
		1259
		1260	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1261	threads that did not get a request to process within 10 seconds). That
		1262	means if a thread becomes idle while C<$nthreads> other threads are also
		1263	idle, it will free its resources and exit.
		1264
		1265	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1266	to allow for extremely high load situations, but want to free resources
		1267	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1268
		1269	The default is probably ok in most situations, especially if thread
		1270	creation is fast. If thread creation is very slow on your system you might
		1271	want to use larger values.
		1272
		1273	=item IO::AIO::max_outstanding $maxreqs
		1274
		1275	This is a very bad function to use in interactive programs because it
		1276	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1277	use an C<aio_group> together with a feed callback.
		1278
		1279	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		1280	do queue up more than this number of requests, the next call to the
		1281	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1282	function will block until the limit is no longer exceeded.
		1283
		1284	The default value is very large, so there is no practical limit on the
		1285	number of outstanding requests.
		1286
		1287	You can still queue as many requests as you want. Therefore,
		1288	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1289	as a stop gap to shield against fatal memory overflow (with large values).
		1290
		1291	=back
		1292
		1293	=head3 STATISTICAL INFORMATION
		1294
		1295	=over
		1296
254	=item IO::AIO::flush	1297	=item IO::AIO::nreqs
255		1298
256	Wait till all outstanding AIO requests have been handled.	1299	Returns the number of requests currently in the ready, execute or pending
		1300	states (i.e. for which their callback has not been invoked yet).
257		1301
258	Strictly equivalent to:	1302	Example: wait till there are no outstanding requests anymore:
259		1303
260	IO::AIO::poll_wait, IO::AIO::poll_cb	1304	IO::AIO::poll_wait, IO::AIO::poll_cb
261	while IO::AIO::nreqs;	1305	while IO::AIO::nreqs;
262		1306
		1307	=item IO::AIO::nready
		1308
		1309	Returns the number of requests currently in the ready state (not yet
		1310	executed).
		1311
263	=item IO::AIO::poll	1312	=item IO::AIO::npending
264		1313
265	Waits until some requests have been handled.	1314	Returns the number of requests currently in the pending state (executed,
266		1315	but not yet processed by poll_cb).
267	Strictly equivalent to:
268
269	IO::AIO::poll_wait, IO::AIO::poll_cb
270	if IO::AIO::nreqs;
271
272	=item IO::AIO::min_parallel $nthreads
273
274	Set the minimum number of AIO threads to C<$nthreads>. The default is
275	C<1>, which means a single asynchronous operation can be done at one time
276	(the number of outstanding operations, however, is unlimited).
277
278	It is recommended to keep the number of threads low, as some Linux
279	kernel versions will scale negatively with the number of threads (higher
280	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
281	threads should be fine.
282
283	Under normal circumstances you don't need to call this function, as this
284	module automatically starts some threads (the exact number might change,
285	and is currently 4).
286
287	=item IO::AIO::max_parallel $nthreads
288
289	Sets the maximum number of AIO threads to C<$nthreads>. If more than
290	the specified number of threads are currently running, kill them. This
291	function blocks until the limit is reached.
292
293	This module automatically runs C<max_parallel 0> at program end, to ensure
294	that all threads are killed and that there are no outstanding requests.
295
296	Under normal circumstances you don't need to call this function.
297
298	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
299
300	Sets the maximum number of outstanding requests to C<$nreqs>. If you
301	try to queue up more than this number of requests, the caller will block until
302	some requests have been handled.
303
304	The default is very large, so normally there is no practical limit. If you
305	queue up many requests in a loop it it often improves speed if you set
306	this to a relatively low number, such as C<100>.
307
308	Under normal circumstances you don't need to call this function.
309		1316
310	=back	1317	=back
311		1318
312	=cut	1319	=cut
313		1320
314	# support function to convert a fd into a perl filehandle
315	sub _fd2fh {
316	return undef if $_[0] < 0;
317
318	# try to generate nice filehandles
319	my $sym = "IO::AIO::fd#$_[0]";
320	local *$sym;
321	open *$sym, "+<&=$_[0]"
322	or return undef;
323
324	*$sym
325	}
326
327	min_parallel 4;	1321	min_parallel 8;
328		1322
329	END {	1323	END { flush }
330	max_parallel 0;
331	}
332		1324
333	1;	1325	1;
334		1326
		1327	=head2 FORK BEHAVIOUR
		1328
		1329	This module should do "the right thing" when the process using it forks:
		1330
		1331	Before the fork, IO::AIO enters a quiescent state where no requests
		1332	can be added in other threads and no results will be processed. After
		1333	the fork the parent simply leaves the quiescent state and continues
		1334	request/result processing, while the child frees the request/result queue
		1335	(so that the requests started before the fork will only be handled in the
		1336	parent). Threads will be started on demand until the limit set in the
		1337	parent process has been reached again.
		1338
		1339	In short: the parent will, after a short pause, continue as if fork had
		1340	not been called, while the child will act as if IO::AIO has not been used
		1341	yet.
		1342
		1343	=head2 MEMORY USAGE
		1344
		1345	Per-request usage:
		1346
		1347	Each aio request uses - depending on your architecture - around 100-200
		1348	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1349	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1350	scalars and other data passed into aio requests will also be locked and
		1351	will consume memory till the request has entered the done state.
		1352
		1353	This is not awfully much, so queuing lots of requests is not usually a
		1354	problem.
		1355
		1356	Per-thread usage:
		1357
		1358	In the execution phase, some aio requests require more memory for
		1359	temporary buffers, and each thread requires a stack and other data
		1360	structures (usually around 16k-128k, depending on the OS).
		1361
		1362	=head1 KNOWN BUGS
		1363
		1364	Known bugs will be fixed in the next release.
		1365
335	=head1 SEE ALSO	1366	=head1 SEE ALSO
336		1367
337	L<Coro>, L<Linux::AIO>.	1368	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1369	more natural syntax.
338		1370
339	=head1 AUTHOR	1371	=head1 AUTHOR
340		1372
341	Marc Lehmann <schmorp@schmorp.de>	1373	Marc Lehmann <schmorp@schmorp.de>
342	http://home.schmorp.de/	1374	http://home.schmorp.de/

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