[ViewVC] Diff of: cvs/IO-AIO/AIO.pm

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.42 by root, Mon Dec 26 18:15:23 2005 UTC vs.
Revision 1.106 by root, Fri Jun 1 05:51:21 2007 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	# AnyEvent	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
21	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
22	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });	33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
23		34
24	# Event	35	# Event integration
25	Event->io (fd => IO::AIO::poll_fileno,	36	Event->io (fd => IO::AIO::poll_fileno,
26	poll => 'r',	37	poll => 'r',
27	cb => \&IO::AIO::poll_cb);	38	cb => \&IO::AIO::poll_cb);
28		39
29	# Glib/Gtk2	40	# Glib/Gtk2 integration
30	add_watch Glib::IO IO::AIO::poll_fileno,	41	add_watch Glib::IO IO::AIO::poll_fileno,
31	in => sub { IO::AIO::poll_cb; 1 };	42	in => sub { IO::AIO::poll_cb; 1 };
32		43
33	# Tk	44	# Tk integration
34	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
35	readable => \&IO::AIO::poll_cb);	46	readable => \&IO::AIO::poll_cb);
36		47
37	# Danga::Socket	48	# Danga::Socket integration
38	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
39	\&IO::AIO::poll_cb);	50	\&IO::AIO::poll_cb);
40		51
41
42	=head1 DESCRIPTION	52	=head1 DESCRIPTION
43		53
44	This module implements asynchronous I/O using whatever means your	54	This module implements asynchronous I/O using whatever means your
45	operating system supports.	55	operating system supports.
46		56
		57	Asynchronous means that operations that can normally block your program
		58	(e.g. reading from disk) will be done asynchronously: the operation
		59	will still block, but you can do something else in the meantime. This
		60	is extremely useful for programs that need to stay interactive even
		61	when doing heavy I/O (GUI programs, high performance network servers
		62	etc.), but can also be used to easily do operations in parallel that are
		63	normally done sequentially, e.g. stat'ing many files, which is much faster
		64	on a RAID volume or over NFS when you do a number of stat operations
		65	concurrently.
		66
		67	While most of this works on all types of file descriptors (for example
		68	sockets), using these functions on file descriptors that support
		69	nonblocking operation (again, sockets, pipes etc.) is very inefficient or
		70	might not work (aio_read fails on sockets/pipes/fifos). Use an event loop
		71	for that (such as the L<Event\|Event> module): IO::AIO will naturally fit
		72	into such an event loop itself.
		73
47	Currently, a number of threads are started that execute your read/writes	74	In this version, a number of threads are started that execute your
48	and signal their completion. You don't need thread support in your libc or	75	requests and signal their completion. You don't need thread support
49	perl, and the threads created by this module will not be visible to the	76	in perl, and the threads created by this module will not be visible
50	pthreads library. In the future, this module might make use of the native	77	to perl. In the future, this module might make use of the native aio
51	aio functions available on many operating systems. However, they are often	78	functions available on many operating systems. However, they are often
52	not well-supported (Linux doesn't allow them on normal files currently,	79	not well-supported or restricted (GNU/Linux doesn't allow them on normal
53	for example), and they would only support aio_read and aio_write, so the	80	files currently, for example), and they would only support aio_read and
54	remaining functionality would have to be implemented using threads anyway.	81	aio_write, so the remaining functionality would have to be implemented
		82	using threads anyway.
55		83
56	Although the module will work with in the presence of other threads, it is	84	Although the module will work with in the presence of other (Perl-)
57	currently not reentrant, so use appropriate locking yourself, always call	85	threads, it is currently not reentrant in any way, so use appropriate
58	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	86	locking yourself, always call C<poll_cb> from within the same thread, or
59	C<aio_> functions) recursively.	87	never call C<poll_cb> (or other C<aio_> functions) recursively.
		88
		89	=head2 EXAMPLE
		90
		91	This is a simple example that uses the Event module and loads
		92	F</etc/passwd> asynchronously:
		93
		94	use Fcntl;
		95	use Event;
		96	use IO::AIO;
		97
		98	# register the IO::AIO callback with Event
		99	Event->io (fd => IO::AIO::poll_fileno,
		100	poll => 'r',
		101	cb => \&IO::AIO::poll_cb);
		102
		103	# queue the request to open /etc/passwd
		104	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		105	my $fh = shift
		106	or die "error while opening: $!";
		107
		108	# stat'ing filehandles is generally non-blocking
		109	my $size = -s $fh;
		110
		111	# queue a request to read the file
		112	my $contents;
		113	aio_read $fh, 0, $size, $contents, 0, sub {
		114	$_[0] == $size
		115	or die "short read: $!";
		116
		117	close $fh;
		118
		119	# file contents now in $contents
		120	print $contents;
		121
		122	# exit event loop and program
		123	Event::unloop;
		124	};
		125	};
		126
		127	# possibly queue up other requests, or open GUI windows,
		128	# check for sockets etc. etc.
		129
		130	# process events as long as there are some:
		131	Event::loop;
		132
		133	=head1 REQUEST ANATOMY AND LIFETIME
		134
		135	Every C<aio_*> function creates a request. which is a C data structure not
		136	directly visible to Perl.
		137
		138	If called in non-void context, every request function returns a Perl
		139	object representing the request. In void context, nothing is returned,
		140	which saves a bit of memory.
		141
		142	The perl object is a fairly standard ref-to-hash object. The hash contents
		143	are not used by IO::AIO so you are free to store anything you like in it.
		144
		145	During their existance, aio requests travel through the following states,
		146	in order:
		147
		148	=over 4
		149
		150	=item ready
		151
		152	Immediately after a request is created it is put into the ready state,
		153	waiting for a thread to execute it.
		154
		155	=item execute
		156
		157	A thread has accepted the request for processing and is currently
		158	executing it (e.g. blocking in read).
		159
		160	=item pending
		161
		162	The request has been executed and is waiting for result processing.
		163
		164	While request submission and execution is fully asynchronous, result
		165	processing is not and relies on the perl interpreter calling C<poll_cb>
		166	(or another function with the same effect).
		167
		168	=item result
		169
		170	The request results are processed synchronously by C<poll_cb>.
		171
		172	The C<poll_cb> function will process all outstanding aio requests by
		173	calling their callbacks, freeing memory associated with them and managing
		174	any groups they are contained in.
		175
		176	=item done
		177
		178	Request has reached the end of its lifetime and holds no resources anymore
		179	(except possibly for the Perl object, but its connection to the actual
		180	aio request is severed and calling its methods will either do nothing or
		181	result in a runtime error).
		182
		183	=back
60		184
61	=cut	185	=cut
62		186
63	package IO::AIO;	187	package IO::AIO;
64		188
65	no warnings;	189	no warnings;
		190	use strict 'vars';
66		191
67	use base 'Exporter';	192	use base 'Exporter';
68		193
69	use Fcntl ();
70
71	BEGIN {	194	BEGIN {
72	$VERSION = '1.61';	195	our $VERSION = '2.4';
73		196
74	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	197	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
75	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	198	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
76	aio_fsync aio_fdatasync aio_readahead);	199	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
77	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	200	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
78	max_outstanding nreqs);	201	aio_chown aio_chmod aio_utime);
		202	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		203	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		204	min_parallel max_parallel max_idle
		205	nreqs nready npending nthreads
		206	max_poll_time max_poll_reqs);
		207
		208	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
79		209
80	require XSLoader;	210	require XSLoader;
81	XSLoader::load IO::AIO, $VERSION;	211	XSLoader::load ("IO::AIO", $VERSION);
82	}	212	}
83		213
84	=head1 FUNCTIONS	214	=head1 FUNCTIONS
85		215
86	=head2 AIO FUNCTIONS	216	=head2 AIO REQUEST FUNCTIONS
87		217
88	All the C<aio_*> calls are more or less thin wrappers around the syscall	218	All the C<aio_*> calls are more or less thin wrappers around the syscall
89	with the same name (sans C<aio_>). The arguments are similar or identical,	219	with the same name (sans C<aio_>). The arguments are similar or identical,
90	and they all accept an additional (and optional) C<$callback> argument	220	and they all accept an additional (and optional) C<$callback> argument
91	which must be a code reference. This code reference will get called with	221	which must be a code reference. This code reference will get called with
…		…
94	syscall has been executed asynchronously.	224	syscall has been executed asynchronously.
95		225
96	All functions expecting a filehandle keep a copy of the filehandle	226	All functions expecting a filehandle keep a copy of the filehandle
97	internally until the request has finished.	227	internally until the request has finished.
98		228
		229	All functions return request objects of type L<IO::AIO::REQ> that allow
		230	further manipulation of those requests while they are in-flight.
		231
99	The pathnames you pass to these routines I<must> be absolute and	232	The pathnames you pass to these routines I<must> be absolute and
100	encoded in byte form. The reason for the former is that at the time the	233	encoded as octets. The reason for the former is that at the time the
101	request is being executed, the current working directory could have	234	request is being executed, the current working directory could have
102	changed. Alternatively, you can make sure that you never change the	235	changed. Alternatively, you can make sure that you never change the
103	current working directory.	236	current working directory anywhere in the program and then use relative
		237	paths.
104		238
105	To encode pathnames to byte form, either make sure you either: a)	239	To encode pathnames as octets, either make sure you either: a) always pass
106	always pass in filenames you got from outside (command line, readdir	240	in filenames you got from outside (command line, readdir etc.) without
107	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	241	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
108	your pathnames to the locale (or other) encoding in effect in the user	242	your pathnames to the locale (or other) encoding in effect in the user
109	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	243	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
110	use something else.	244	use something else to ensure your scalar has the correct contents.
		245
		246	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		247	handles correctly wether it is set or not.
111		248
112	=over 4	249	=over 4
		250
		251	=item $prev_pri = aioreq_pri [$pri]
		252
		253	Returns the priority value that would be used for the next request and, if
		254	C<$pri> is given, sets the priority for the next aio request.
		255
		256	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		257	and C<4>, respectively. Requests with higher priority will be serviced
		258	first.
		259
		260	The priority will be reset to C<0> after each call to one of the C<aio_*>
		261	functions.
		262
		263	Example: open a file with low priority, then read something from it with
		264	higher priority so the read request is serviced before other low priority
		265	open requests (potentially spamming the cache):
		266
		267	aioreq_pri -3;
		268	aio_open ..., sub {
		269	return unless $_[0];
		270
		271	aioreq_pri -2;
		272	aio_read $_[0], ..., sub {
		273	...
		274	};
		275	};
		276
		277
		278	=item aioreq_nice $pri_adjust
		279
		280	Similar to C<aioreq_pri>, but subtracts the given value from the current
		281	priority, so the effect is cumulative.
		282
113		283
114	=item aio_open $pathname, $flags, $mode, $callback->($fh)	284	=item aio_open $pathname, $flags, $mode, $callback->($fh)
115		285
116	Asynchronously open or create a file and call the callback with a newly	286	Asynchronously open or create a file and call the callback with a newly
117	created filehandle for the file.	287	created filehandle for the file.
…		…
123	list. They are the same as used by C<sysopen>.	293	list. They are the same as used by C<sysopen>.
124		294
125	Likewise, C<$mode> specifies the mode of the newly created file, if it	295	Likewise, C<$mode> specifies the mode of the newly created file, if it
126	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	296	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
127	except that it is mandatory (i.e. use C<0> if you don't create new files,	297	except that it is mandatory (i.e. use C<0> if you don't create new files,
128	and C<0666> or C<0777> if you do).	298	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		299	by the umask in effect then the request is being executed, so better never
		300	change the umask.
129		301
130	Example:	302	Example:
131		303
132	aio_open "/etc/passwd", O_RDONLY, 0, sub {	304	aio_open "/etc/passwd", O_RDONLY, 0, sub {
133	if ($_[0]) {	305	if ($_[0]) {
…		…
136	} else {	308	} else {
137	die "open failed: $!\n";	309	die "open failed: $!\n";
138	}	310	}
139	};	311	};
140		312
		313
141	=item aio_close $fh, $callback->($status)	314	=item aio_close $fh, $callback->($status)
142		315
143	Asynchronously close a file and call the callback with the result	316	Asynchronously close a file and call the callback with the result
144	code. I<WARNING:> although accepted, you should not pass in a perl	317	code. I<WARNING:> although accepted, you should not pass in a perl
145	filehandle here, as perl will likely close the file descriptor another	318	filehandle here, as perl will likely close the file descriptor another
…		…
147	C<close> or just let filehandles go out of scope.	320	C<close> or just let filehandles go out of scope.
148		321
149	This is supposed to be a bug in the API, so that might change. It's	322	This is supposed to be a bug in the API, so that might change. It's
150	therefore best to avoid this function.	323	therefore best to avoid this function.
151		324
		325
152	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	326	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
153		327
154	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	328	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
155		329
156	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	330	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
…		…
167		341
168	aio_read $fh, 7, 15, $buffer, 0, sub {	342	aio_read $fh, 7, 15, $buffer, 0, sub {
169	$_[0] > 0 or die "read error: $!";	343	$_[0] > 0 or die "read error: $!";
170	print "read $_[0] bytes: <$buffer>\n";	344	print "read $_[0] bytes: <$buffer>\n";
171	};	345	};
		346
172		347
173	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	348	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
174		349
175	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	350	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
176	reading at byte offset C<$in_offset>, and starts writing at the current	351	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
190	C<$in_fh> than are written, and there is no way to find out how many	365	C<$in_fh> than are written, and there is no way to find out how many
191	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	366	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
192	provides the number of bytes written to C<$out_fh>. Only if the result	367	provides the number of bytes written to C<$out_fh>. Only if the result
193	value equals C<$length> one can assume that C<$length> bytes have been	368	value equals C<$length> one can assume that C<$length> bytes have been
194	read.	369	read.
		370
195		371
196	=item aio_readahead $fh,$offset,$length, $callback->($retval)	372	=item aio_readahead $fh,$offset,$length, $callback->($retval)
197		373
198	C<aio_readahead> populates the page cache with data from a file so that	374	C<aio_readahead> populates the page cache with data from a file so that
199	subsequent reads from that file will not block on disk I/O. The C<$offset>	375	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
205	file. The current file offset of the file is left unchanged.	381	file. The current file offset of the file is left unchanged.
206		382
207	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	383	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
208	emulated by simply reading the data, which would have a similar effect.	384	emulated by simply reading the data, which would have a similar effect.
209		385
		386
210	=item aio_stat $fh_or_path, $callback->($status)	387	=item aio_stat $fh_or_path, $callback->($status)
211		388
212	=item aio_lstat $fh, $callback->($status)	389	=item aio_lstat $fh, $callback->($status)
213		390
214	Works like perl's C<stat> or C<lstat> in void context. The callback will	391	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
227	aio_stat "/etc/passwd", sub {	404	aio_stat "/etc/passwd", sub {
228	$_[0] and die "stat failed: $!";	405	$_[0] and die "stat failed: $!";
229	print "size is ", -s _, "\n";	406	print "size is ", -s _, "\n";
230	};	407	};
231		408
		409
		410	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		411
		412	Works like perl's C<utime> function (including the special case of $atime
		413	and $mtime being undef). Fractional times are supported if the underlying
		414	syscalls support them.
		415
		416	When called with a pathname, uses utimes(2) if available, otherwise
		417	utime(2). If called on a file descriptor, uses futimes(2) if available,
		418	otherwise returns ENOSYS, so this is not portable.
		419
		420	Examples:
		421
		422	# set atime and mtime to current time:
		423	aio_utime "path", undef, undef;
		424	# set atime to current time and mtime to beginning of the epoch:
		425	aio_utime "path", time, undef; # undef==0
		426
		427
		428	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		429
		430	Works like perl's C<chown> function, except that C<undef> for either $uid
		431	or $gid is being interpreted as "do not change" (but -1 can also be used).
		432
		433	Examples:
		434
		435	# same as "chown root path" in the shell:
		436	aio_chown "path", 0, -1;
		437	# same as above:
		438	aio_chown "path", 0, undef;
		439
		440
		441	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		442
		443	Works like perl's C<chmod> function.
		444
		445
232	=item aio_unlink $pathname, $callback->($status)	446	=item aio_unlink $pathname, $callback->($status)
233		447
234	Asynchronously unlink (delete) a file and call the callback with the	448	Asynchronously unlink (delete) a file and call the callback with the
235	result code.	449	result code.
236		450
		451
		452	=item aio_mknod $path, $mode, $dev, $callback->($status)
		453
		454	[EXPERIMENTAL]
		455
		456	Asynchronously create a device node (or fifo). See mknod(2).
		457
		458	The only (POSIX-) portable way of calling this function is:
		459
		460	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		461
		462
		463	=item aio_link $srcpath, $dstpath, $callback->($status)
		464
		465	Asynchronously create a new link to the existing object at C<$srcpath> at
		466	the path C<$dstpath> and call the callback with the result code.
		467
		468
		469	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		470
		471	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		472	the path C<$dstpath> and call the callback with the result code.
		473
		474
		475	=item aio_readlink $path, $callback->($link)
		476
		477	Asynchronously read the symlink specified by C<$path> and pass it to
		478	the callback. If an error occurs, nothing or undef gets passed to the
		479	callback.
		480
		481
		482	=item aio_rename $srcpath, $dstpath, $callback->($status)
		483
		484	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		485	rename(2) and call the callback with the result code.
		486
		487
		488	=item aio_mkdir $pathname, $mode, $callback->($status)
		489
		490	Asynchronously mkdir (create) a directory and call the callback with
		491	the result code. C<$mode> will be modified by the umask at the time the
		492	request is executed, so do not change your umask.
		493
		494
237	=item aio_rmdir $pathname, $callback->($status)	495	=item aio_rmdir $pathname, $callback->($status)
238		496
239	Asynchronously rmdir (delete) a directory and call the callback with the	497	Asynchronously rmdir (delete) a directory and call the callback with the
240	result code.	498	result code.
241		499
		500
242	=item aio_readdir $pathname $callback->($entries)	501	=item aio_readdir $pathname, $callback->($entries)
243		502
244	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	503	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
245	directory (i.e. opendir + readdir + closedir). The entries will not be	504	directory (i.e. opendir + readdir + closedir). The entries will not be
246	sorted, and will B<NOT> include the C<.> and C<..> entries.	505	sorted, and will B<NOT> include the C<.> and C<..> entries.
247		506
248	The callback a single argument which is either C<undef> or an array-ref	507	The callback a single argument which is either C<undef> or an array-ref
249	with the filenames.	508	with the filenames.
250		509
		510
		511	=item aio_load $path, $data, $callback->($status)
		512
		513	This is a composite request that tries to fully load the given file into
		514	memory. Status is the same as with aio_read.
		515
		516	=cut
		517
		518	sub aio_load($$;$) {
		519	aio_block {
		520	my ($path, undef, $cb) = @_;
		521	my $data = \$_[1];
		522
		523	my $pri = aioreq_pri;
		524	my $grp = aio_group $cb;
		525
		526	aioreq_pri $pri;
		527	add $grp aio_open $path, O_RDONLY, 0, sub {
		528	my $fh = shift
		529	or return $grp->result (-1);
		530
		531	aioreq_pri $pri;
		532	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		533	$grp->result ($_[0]);
		534	};
		535	};
		536
		537	$grp
		538	}
		539	}
		540
		541	=item aio_copy $srcpath, $dstpath, $callback->($status)
		542
		543	Try to copy the I<file> (directories not supported as either source or
		544	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		545	the C<0> (error) or C<-1> ok.
		546
		547	This is a composite request that it creates the destination file with
		548	mode 0200 and copies the contents of the source file into it using
		549	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		550	uid/gid, in that order.
		551
		552	If an error occurs, the partial destination file will be unlinked, if
		553	possible, except when setting atime, mtime, access mode and uid/gid, where
		554	errors are being ignored.
		555
		556	=cut
		557
		558	sub aio_copy($$;$) {
		559	aio_block {
		560	my ($src, $dst, $cb) = @_;
		561
		562	my $pri = aioreq_pri;
		563	my $grp = aio_group $cb;
		564
		565	aioreq_pri $pri;
		566	add $grp aio_open $src, O_RDONLY, 0, sub {
		567	if (my $src_fh = $_[0]) {
		568	my @stat = stat $src_fh;
		569
		570	aioreq_pri $pri;
		571	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		572	if (my $dst_fh = $_[0]) {
		573	aioreq_pri $pri;
		574	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		575	if ($_[0] == $stat[7]) {
		576	$grp->result (0);
		577	close $src_fh;
		578
		579	# those should not normally block. should. should.
		580	utime $stat[8], $stat[9], $dst;
		581	chmod $stat[2] & 07777, $dst_fh;
		582	chown $stat[4], $stat[5], $dst_fh;
		583	close $dst_fh;
		584	} else {
		585	$grp->result (-1);
		586	close $src_fh;
		587	close $dst_fh;
		588
		589	aioreq $pri;
		590	add $grp aio_unlink $dst;
		591	}
		592	};
		593	} else {
		594	$grp->result (-1);
		595	}
		596	},
		597
		598	} else {
		599	$grp->result (-1);
		600	}
		601	};
		602
		603	$grp
		604	}
		605	}
		606
		607	=item aio_move $srcpath, $dstpath, $callback->($status)
		608
		609	Try to move the I<file> (directories not supported as either source or
		610	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		611	the C<0> (error) or C<-1> ok.
		612
		613	This is a composite request that tries to rename(2) the file first. If
		614	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		615	that is successful, unlinking the C<$srcpath>.
		616
		617	=cut
		618
		619	sub aio_move($$;$) {
		620	aio_block {
		621	my ($src, $dst, $cb) = @_;
		622
		623	my $pri = aioreq_pri;
		624	my $grp = aio_group $cb;
		625
		626	aioreq_pri $pri;
		627	add $grp aio_rename $src, $dst, sub {
		628	if ($_[0] && $! == EXDEV) {
		629	aioreq_pri $pri;
		630	add $grp aio_copy $src, $dst, sub {
		631	$grp->result ($_[0]);
		632
		633	if (!$_[0]) {
		634	aioreq_pri $pri;
		635	add $grp aio_unlink $src;
		636	}
		637	};
		638	} else {
		639	$grp->result ($_[0]);
		640	}
		641	};
		642
		643	$grp
		644	}
		645	}
		646
251	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	647	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
252		648
253	Scans a directory (similar to C<aio_readdir>) and tries to separate the	649	Scans a directory (similar to C<aio_readdir>) but additionally tries to
254	entries of directory C<$path> into two sets of names, ones you can recurse	650	efficiently separate the entries of directory C<$path> into two sets of
255	into (directories), and ones you cannot recurse into (everything else).	651	names, directories you can recurse into (directories), and ones you cannot
		652	recurse into (everything else, including symlinks to directories).
256		653
257	C<aio_scandir> is a composite request that consists of many	654	C<aio_scandir> is a composite request that creates of many sub requests_
258	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	655	C<$maxreq> specifies the maximum number of outstanding aio requests that
259	aio requests that this function generates. If it is C<< <= 0 >>, then a	656	this function generates. If it is C<< <= 0 >>, then a suitable default
260	suitable default will be chosen (currently 8).	657	will be chosen (currently 4).
261		658
262	On error, the callback is called without arguments, otherwise it receives	659	On error, the callback is called without arguments, otherwise it receives
263	two array-refs with path-relative entry names.	660	two array-refs with path-relative entry names.
264		661
265	Example:	662	Example:
…		…
273	Implementation notes.	670	Implementation notes.
274		671
275	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	672	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
276		673
277	After reading the directory, the modification time, size etc. of the	674	After reading the directory, the modification time, size etc. of the
278	directory before and after the readdir is checked, and if they match, the	675	directory before and after the readdir is checked, and if they match (and
279	link count will be used to decide how many entries are directories (if	676	isn't the current time), the link count will be used to decide how many
280	>= 2). Otherwise, no knowledge of the number of subdirectories will be	677	entries are directories (if >= 2). Otherwise, no knowledge of the number
281	assumed.	678	of subdirectories will be assumed.
282		679
283	Then entires will be sorted into likely directories (everything without a	680	Then entries will be sorted into likely directories (everything without
284	non-initial dot) and likely non-directories (everything else). Then every	681	a non-initial dot currently) and likely non-directories (everything
285	entry + C</.> will be C<stat>'ed, likely directories first. This is often	682	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		683	likely directories first. If that succeeds, it assumes that the entry
		684	is a directory or a symlink to directory (which will be checked
		685	seperately). This is often faster than stat'ing the entry itself because
286	faster because filesystems might detect the type of the entry without	686	filesystems might detect the type of the entry without reading the inode
287	reading the inode data (e.g. ext2s filetype feature). If that succeeds,	687	data (e.g. ext2fs filetype feature).
288	it assumes that the entry is a directory or a symlink to directory (which
289	will be checked seperately).
290		688
291	If the known number of directories has been reached, the rest of the	689	If the known number of directories (link count - 2) has been reached, the
292	entries is assumed to be non-directories.	690	rest of the entries is assumed to be non-directories.
		691
		692	This only works with certainty on POSIX (= UNIX) filesystems, which
		693	fortunately are the vast majority of filesystems around.
		694
		695	It will also likely work on non-POSIX filesystems with reduced efficiency
		696	as those tend to return 0 or 1 as link counts, which disables the
		697	directory counting heuristic.
293		698
294	=cut	699	=cut
295		700
296	sub aio_scandir($$$) {	701	sub aio_scandir($$;$) {
		702	aio_block {
297	my ($path, $maxreq, $cb) = @_;	703	my ($path, $maxreq, $cb) = @_;
298		704
		705	my $pri = aioreq_pri;
		706
		707	my $grp = aio_group $cb;
		708
299	$maxreq = 8 if $maxreq <= 0;	709	$maxreq = 4 if $maxreq <= 0;
300		710
301	# stat once	711	# stat once
		712	aioreq_pri $pri;
302	aio_stat $path, sub {	713	add $grp aio_stat $path, sub {
303	$cb->() if $_[0];	714	return $grp->result () if $_[0];
		715	my $now = time;
304	my $hash1 = join ":", (stat _)[0,1,3,7,9];	716	my $hash1 = join ":", (stat _)[0,1,3,7,9];
305		717
306	# read the directory entries	718	# read the directory entries
		719	aioreq_pri $pri;
307	aio_readdir $path, sub {	720	add $grp aio_readdir $path, sub {
308	my $entries = shift	721	my $entries = shift
309	or return $cb->();	722	or return $grp->result ();
310		723
311	# stat the dir another time	724	# stat the dir another time
		725	aioreq_pri $pri;
312	aio_stat $path, sub {	726	add $grp aio_stat $path, sub {
313	my $hash2 = join ":", (stat _)[0,1,3,7,9];	727	my $hash2 = join ":", (stat _)[0,1,3,7,9];
314		728
315	my $ndirs;	729	my $ndirs;
316		730
317	# take the slow route if anything looks fishy	731	# take the slow route if anything looks fishy
318	if ($hash1 ne $hash2) {	732	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
319	$ndirs = -1;	733	$ndirs = -1;
320	} else {	734	} else {
321	# if nlink == 2, we are finished	735	# if nlink == 2, we are finished
322	# on non-posix-fs's, we rely on nlink < 2	736	# on non-posix-fs's, we rely on nlink < 2
323	$ndirs = (stat _)[3] - 2	737	$ndirs = (stat _)[3] - 2
324	or $cb->([], $entries);	738	or return $grp->result ([], $entries);
325	}
326
327	# sort into likely dirs and likely nondirs
328	# dirs == files without ".", short entries first
329	$entries = [map $_->[0],
330	sort { $b->[1] cmp $a->[1] }
331	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
332	@$entries];
333
334	my (@dirs, @nondirs);
335
336	my ($statcb, $schedcb);
337	my $nreq = 0;
338
339	$schedcb = sub {
340	if (@$entries) {
341	if ($nreq < $maxreq) {
342	my $ent = pop @$entries;
343	$nreq++;
344	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
345	}
346	} elsif (!$nreq) {
347	# finished
348	undef $statcb;
349	undef $schedcb;
350	$cb->(\@dirs, \@nondirs);
351	undef $cb;
352	}	739	}
		740
		741	# sort into likely dirs and likely nondirs
		742	# dirs == files without ".", short entries first
		743	$entries = [map $_->[0],
		744	sort { $b->[1] cmp $a->[1] }
		745	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		746	@$entries];
		747
		748	my (@dirs, @nondirs);
		749
		750	my $statgrp = add $grp aio_group sub {
		751	$grp->result (\@dirs, \@nondirs);
		752	};
		753
		754	limit $statgrp $maxreq;
		755	feed $statgrp sub {
		756	return unless @$entries;
		757	my $entry = pop @$entries;
		758
		759	aioreq_pri $pri;
		760	add $statgrp aio_stat "$path/$entry/.", sub {
		761	if ($_[0] < 0) {
		762	push @nondirs, $entry;
		763	} else {
		764	# need to check for real directory
		765	aioreq_pri $pri;
		766	add $statgrp aio_lstat "$path/$entry", sub {
		767	if (-d _) {
		768	push @dirs, $entry;
		769
		770	unless (--$ndirs) {
		771	push @nondirs, @$entries;
		772	feed $statgrp;
		773	}
		774	} else {
		775	push @nondirs, $entry;
		776	}
		777	}
		778	}
		779	};
		780	};
353	};	781	};
354	$statcb = sub {
355	my ($status, $entry) = @_;
356
357	if ($status < 0) {
358	$nreq--;
359	push @nondirs, $entry;
360	&$schedcb;
361	} else {
362	# need to check for real directory
363	aio_lstat "$path/$entry", sub {
364	$nreq--;
365
366	if (-d _) {
367	push @dirs, $entry;
368
369	if (!--$ndirs) {
370	push @nondirs, @$entries;
371	$entries = [];
372	}
373	} else {
374	push @nondirs, $entry;
375	}
376
377	&$schedcb;
378	}
379	}
380	};
381
382	&$schedcb while @$entries && $nreq < $maxreq;
383	};	782	};
384	};	783	};
		784
		785	$grp
385	};	786	}
		787	}
		788
		789	=item aio_rmtree $path, $callback->($status)
		790
		791	Delete a directory tree starting (and including) C<$path>, return the
		792	status of the final C<rmdir> only. This is a composite request that
		793	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		794	everything else.
		795
		796	=cut
		797
		798	sub aio_rmtree;
		799	sub aio_rmtree($;$) {
		800	aio_block {
		801	my ($path, $cb) = @_;
		802
		803	my $pri = aioreq_pri;
		804	my $grp = aio_group $cb;
		805
		806	aioreq_pri $pri;
		807	add $grp aio_scandir $path, 0, sub {
		808	my ($dirs, $nondirs) = @_;
		809
		810	my $dirgrp = aio_group sub {
		811	add $grp aio_rmdir $path, sub {
		812	$grp->result ($_[0]);
		813	};
		814	};
		815
		816	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		817	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		818
		819	add $grp $dirgrp;
		820	};
		821
		822	$grp
		823	}
386	}	824	}
387		825
388	=item aio_fsync $fh, $callback->($status)	826	=item aio_fsync $fh, $callback->($status)
389		827
390	Asynchronously call fsync on the given filehandle and call the callback	828	Asynchronously call fsync on the given filehandle and call the callback
…		…
396	callback with the fdatasync result code.	834	callback with the fdatasync result code.
397		835
398	If this call isn't available because your OS lacks it or it couldn't be	836	If this call isn't available because your OS lacks it or it couldn't be
399	detected, it will be emulated by calling C<fsync> instead.	837	detected, it will be emulated by calling C<fsync> instead.
400		838
		839	=item aio_group $callback->(...)
		840
		841	This is a very special aio request: Instead of doing something, it is a
		842	container for other aio requests, which is useful if you want to bundle
		843	many requests into a single, composite, request with a definite callback
		844	and the ability to cancel the whole request with its subrequests.
		845
		846	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		847	for more info.
		848
		849	Example:
		850
		851	my $grp = aio_group sub {
		852	print "all stats done\n";
		853	};
		854
		855	add $grp
		856	(aio_stat ...),
		857	(aio_stat ...),
		858	...;
		859
		860	=item aio_nop $callback->()
		861
		862	This is a special request - it does nothing in itself and is only used for
		863	side effects, such as when you want to add a dummy request to a group so
		864	that finishing the requests in the group depends on executing the given
		865	code.
		866
		867	While this request does nothing, it still goes through the execution
		868	phase and still requires a worker thread. Thus, the callback will not
		869	be executed immediately but only after other requests in the queue have
		870	entered their execution phase. This can be used to measure request
		871	latency.
		872
		873	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		874
		875	Mainly used for debugging and benchmarking, this aio request puts one of
		876	the request workers to sleep for the given time.
		877
		878	While it is theoretically handy to have simple I/O scheduling requests
		879	like sleep and file handle readable/writable, the overhead this creates is
		880	immense (it blocks a thread for a long time) so do not use this function
		881	except to put your application under artificial I/O pressure.
		882
401	=back	883	=back
402		884
		885	=head2 IO::AIO::REQ CLASS
		886
		887	All non-aggregate C<aio_*> functions return an object of this class when
		888	called in non-void context.
		889
		890	=over 4
		891
		892	=item cancel $req
		893
		894	Cancels the request, if possible. Has the effect of skipping execution
		895	when entering the B<execute> state and skipping calling the callback when
		896	entering the the B<result> state, but will leave the request otherwise
		897	untouched. That means that requests that currently execute will not be
		898	stopped and resources held by the request will not be freed prematurely.
		899
		900	=item cb $req $callback->(...)
		901
		902	Replace (or simply set) the callback registered to the request.
		903
		904	=back
		905
		906	=head2 IO::AIO::GRP CLASS
		907
		908	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		909	objects of this class, too.
		910
		911	A IO::AIO::GRP object is a special request that can contain multiple other
		912	aio requests.
		913
		914	You create one by calling the C<aio_group> constructing function with a
		915	callback that will be called when all contained requests have entered the
		916	C<done> state:
		917
		918	my $grp = aio_group sub {
		919	print "all requests are done\n";
		920	};
		921
		922	You add requests by calling the C<add> method with one or more
		923	C<IO::AIO::REQ> objects:
		924
		925	$grp->add (aio_unlink "...");
		926
		927	add $grp aio_stat "...", sub {
		928	$_[0] or return $grp->result ("error");
		929
		930	# add another request dynamically, if first succeeded
		931	add $grp aio_open "...", sub {
		932	$grp->result ("ok");
		933	};
		934	};
		935
		936	This makes it very easy to create composite requests (see the source of
		937	C<aio_move> for an application) that work and feel like simple requests.
		938
		939	=over 4
		940
		941	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		942	C<IO::AIO::poll_cb>, just like any other request.
		943
		944	=item * They can be canceled like any other request. Canceling will cancel not
		945	only the request itself, but also all requests it contains.
		946
		947	=item * They can also can also be added to other IO::AIO::GRP objects.
		948
		949	=item * You must not add requests to a group from within the group callback (or
		950	any later time).
		951
		952	=back
		953
		954	Their lifetime, simplified, looks like this: when they are empty, they
		955	will finish very quickly. If they contain only requests that are in the
		956	C<done> state, they will also finish. Otherwise they will continue to
		957	exist.
		958
		959	That means after creating a group you have some time to add requests. And
		960	in the callbacks of those requests, you can add further requests to the
		961	group. And only when all those requests have finished will the the group
		962	itself finish.
		963
		964	=over 4
		965
		966	=item add $grp ...
		967
		968	=item $grp->add (...)
		969
		970	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		971	be added, including other groups, as long as you do not create circular
		972	dependencies.
		973
		974	Returns all its arguments.
		975
		976	=item $grp->cancel_subs
		977
		978	Cancel all subrequests and clears any feeder, but not the group request
		979	itself. Useful when you queued a lot of events but got a result early.
		980
		981	=item $grp->result (...)
		982
		983	Set the result value(s) that will be passed to the group callback when all
		984	subrequests have finished and set thre groups errno to the current value
		985	of errno (just like calling C<errno> without an error number). By default,
		986	no argument will be passed and errno is zero.
		987
		988	=item $grp->errno ([$errno])
		989
		990	Sets the group errno value to C<$errno>, or the current value of errno
		991	when the argument is missing.
		992
		993	Every aio request has an associated errno value that is restored when
		994	the callback is invoked. This method lets you change this value from its
		995	default (0).
		996
		997	Calling C<result> will also set errno, so make sure you either set C<$!>
		998	before the call to C<result>, or call c<errno> after it.
		999
		1000	=item feed $grp $callback->($grp)
		1001
		1002	Sets a feeder/generator on this group: every group can have an attached
		1003	generator that generates requests if idle. The idea behind this is that,
		1004	although you could just queue as many requests as you want in a group,
		1005	this might starve other requests for a potentially long time. For
		1006	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1007	requests, delaying any later requests for a long time.
		1008
		1009	To avoid this, and allow incremental generation of requests, you can
		1010	instead a group and set a feeder on it that generates those requests. The
		1011	feed callback will be called whenever there are few enough (see C<limit>,
		1012	below) requests active in the group itself and is expected to queue more
		1013	requests.
		1014
		1015	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1016	not impose any limits).
		1017
		1018	If the feed does not queue more requests when called, it will be
		1019	automatically removed from the group.
		1020
		1021	If the feed limit is C<0>, it will be set to C<2> automatically.
		1022
		1023	Example:
		1024
		1025	# stat all files in @files, but only ever use four aio requests concurrently:
		1026
		1027	my $grp = aio_group sub { print "finished\n" };
		1028	limit $grp 4;
		1029	feed $grp sub {
		1030	my $file = pop @files
		1031	or return;
		1032
		1033	add $grp aio_stat $file, sub { ... };
		1034	};
		1035
		1036	=item limit $grp $num
		1037
		1038	Sets the feeder limit for the group: The feeder will be called whenever
		1039	the group contains less than this many requests.
		1040
		1041	Setting the limit to C<0> will pause the feeding process.
		1042
		1043	=back
		1044
403	=head2 SUPPORT FUNCTIONS	1045	=head2 SUPPORT FUNCTIONS
		1046
		1047	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
404		1048
405	=over 4	1049	=over 4
406		1050
407	=item $fileno = IO::AIO::poll_fileno	1051	=item $fileno = IO::AIO::poll_fileno
408		1052
…		…
413		1057
414	See C<poll_cb> for an example.	1058	See C<poll_cb> for an example.
415		1059
416	=item IO::AIO::poll_cb	1060	=item IO::AIO::poll_cb
417		1061
418	Process all outstanding events on the result pipe. You have to call this	1062	Process some outstanding events on the result pipe. You have to call this
419	regularly. Returns the number of events processed. Returns immediately	1063	regularly. Returns the number of events processed. Returns immediately
420	when no events are outstanding.	1064	when no events are outstanding. The amount of events processed depends on
		1065	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1066
		1067	If not all requests were processed for whatever reason, the filehandle
		1068	will still be ready when C<poll_cb> returns.
421		1069
422	Example: Install an Event watcher that automatically calls	1070	Example: Install an Event watcher that automatically calls
423	IO::AIO::poll_cb with high priority:	1071	IO::AIO::poll_cb with high priority:
424		1072
425	Event->io (fd => IO::AIO::poll_fileno,	1073	Event->io (fd => IO::AIO::poll_fileno,
426	poll => 'r', async => 1,	1074	poll => 'r', async => 1,
427	cb => \&IO::AIO::poll_cb);	1075	cb => \&IO::AIO::poll_cb);
428		1076
		1077	=item IO::AIO::max_poll_reqs $nreqs
		1078
		1079	=item IO::AIO::max_poll_time $seconds
		1080
		1081	These set the maximum number of requests (default C<0>, meaning infinity)
		1082	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1083	the maximum amount of time (default C<0>, meaning infinity) spent in
		1084	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1085	of time C<poll_cb> is allowed to use).
		1086
		1087	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1088	syscall per request processed, which is not normally a problem unless your
		1089	callbacks are really really fast or your OS is really really slow (I am
		1090	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1091
		1092	Setting these is useful if you want to ensure some level of
		1093	interactiveness when perl is not fast enough to process all requests in
		1094	time.
		1095
		1096	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1097
		1098	Example: Install an Event watcher that automatically calls
		1099	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1100	program get the CPU sometimes even under high AIO load.
		1101
		1102	# try not to spend much more than 0.1s in poll_cb
		1103	IO::AIO::max_poll_time 0.1;
		1104
		1105	# use a low priority so other tasks have priority
		1106	Event->io (fd => IO::AIO::poll_fileno,
		1107	poll => 'r', nice => 1,
		1108	cb => &IO::AIO::poll_cb);
		1109
429	=item IO::AIO::poll_wait	1110	=item IO::AIO::poll_wait
430		1111
		1112	If there are any outstanding requests and none of them in the result
431	Wait till the result filehandle becomes ready for reading (simply does a	1113	phase, wait till the result filehandle becomes ready for reading (simply
432	C<select> on the filehandle. This is useful if you want to synchronously wait	1114	does a C<select> on the filehandle. This is useful if you want to
433	for some requests to finish).	1115	synchronously wait for some requests to finish).
434		1116
435	See C<nreqs> for an example.	1117	See C<nreqs> for an example.
436		1118
		1119	=item IO::AIO::poll
		1120
		1121	Waits until some requests have been handled.
		1122
		1123	Returns the number of requests processed, but is otherwise strictly
		1124	equivalent to:
		1125
		1126	IO::AIO::poll_wait, IO::AIO::poll_cb
		1127
437	=item IO::AIO::nreqs	1128	=item IO::AIO::flush
438		1129
439	Returns the number of requests currently outstanding (i.e. for which their	1130	Wait till all outstanding AIO requests have been handled.
440	callback has not been invoked yet).
441		1131
442	Example: wait till there are no outstanding requests anymore:	1132	Strictly equivalent to:
443		1133
444	IO::AIO::poll_wait, IO::AIO::poll_cb	1134	IO::AIO::poll_wait, IO::AIO::poll_cb
445	while IO::AIO::nreqs;	1135	while IO::AIO::nreqs;
446		1136
447	=item IO::AIO::flush	1137	=back
448		1138
449	Wait till all outstanding AIO requests have been handled.	1139	=head3 CONTROLLING THE NUMBER OF THREADS
450		1140
451	Strictly equivalent to:	1141	=over
452
453	IO::AIO::poll_wait, IO::AIO::poll_cb
454	while IO::AIO::nreqs;
455
456	=item IO::AIO::poll
457
458	Waits until some requests have been handled.
459
460	Strictly equivalent to:
461
462	IO::AIO::poll_wait, IO::AIO::poll_cb
463	if IO::AIO::nreqs;
464		1142
465	=item IO::AIO::min_parallel $nthreads	1143	=item IO::AIO::min_parallel $nthreads
466		1144
467	Set the minimum number of AIO threads to C<$nthreads>. The current default	1145	Set the minimum number of AIO threads to C<$nthreads>. The current
468	is C<4>, which means four asynchronous operations can be done at one time	1146	default is C<8>, which means eight asynchronous operations can execute
469	(the number of outstanding operations, however, is unlimited).	1147	concurrently at any one time (the number of outstanding requests,
		1148	however, is unlimited).
470		1149
471	IO::AIO starts threads only on demand, when an AIO request is queued and	1150	IO::AIO starts threads only on demand, when an AIO request is queued and
472	no free thread exists.	1151	no free thread exists. Please note that queueing up a hundred requests can
		1152	create demand for a hundred threads, even if it turns out that everything
		1153	is in the cache and could have been processed faster by a single thread.
473		1154
474	It is recommended to keep the number of threads low, as some Linux	1155	It is recommended to keep the number of threads relatively low, as some
475	kernel versions will scale negatively with the number of threads (higher	1156	Linux kernel versions will scale negatively with the number of threads
476	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1157	(higher parallelity => MUCH higher latency). With current Linux 2.6
477	threads should be fine.	1158	versions, 4-32 threads should be fine.
478		1159
479	Under most circumstances you don't need to call this function, as the	1160	Under most circumstances you don't need to call this function, as the
480	module selects a default that is suitable for low to moderate load.	1161	module selects a default that is suitable for low to moderate load.
481		1162
482	=item IO::AIO::max_parallel $nthreads	1163	=item IO::AIO::max_parallel $nthreads
…		…
491	This module automatically runs C<max_parallel 0> at program end, to ensure	1172	This module automatically runs C<max_parallel 0> at program end, to ensure
492	that all threads are killed and that there are no outstanding requests.	1173	that all threads are killed and that there are no outstanding requests.
493		1174
494	Under normal circumstances you don't need to call this function.	1175	Under normal circumstances you don't need to call this function.
495		1176
		1177	=item IO::AIO::max_idle $nthreads
		1178
		1179	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1180	threads that did not get a request to process within 10 seconds). That
		1181	means if a thread becomes idle while C<$nthreads> other threads are also
		1182	idle, it will free its resources and exit.
		1183
		1184	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1185	to allow for extremely high load situations, but want to free resources
		1186	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1187
		1188	The default is probably ok in most situations, especially if thread
		1189	creation is fast. If thread creation is very slow on your system you might
		1190	want to use larger values.
		1191
496	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1192	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1193
		1194	This is a very bad function to use in interactive programs because it
		1195	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1196	use an C<aio_group> together with a feed callback.
497		1197
498	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1198	Sets the maximum number of outstanding requests to C<$nreqs>. If you
499	try to queue up more than this number of requests, the caller will block until	1199	to queue up more than this number of requests, the next call to the
500	some requests have been handled.	1200	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1201	function will block until the limit is no longer exceeded.
501		1202
502	The default is very large, so normally there is no practical limit. If you	1203	The default value is very large, so there is no practical limit on the
503	queue up many requests in a loop it often improves speed if you set	1204	number of outstanding requests.
504	this to a relatively low number, such as C<100>.
505		1205
506	Under normal circumstances you don't need to call this function.	1206	You can still queue as many requests as you want. Therefore,
		1207	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1208	as a stop gap to shield against fatal memory overflow (with large values).
		1209
		1210	=back
		1211
		1212	=head3 STATISTICAL INFORMATION
		1213
		1214	=over
		1215
		1216	=item IO::AIO::nreqs
		1217
		1218	Returns the number of requests currently in the ready, execute or pending
		1219	states (i.e. for which their callback has not been invoked yet).
		1220
		1221	Example: wait till there are no outstanding requests anymore:
		1222
		1223	IO::AIO::poll_wait, IO::AIO::poll_cb
		1224	while IO::AIO::nreqs;
		1225
		1226	=item IO::AIO::nready
		1227
		1228	Returns the number of requests currently in the ready state (not yet
		1229	executed).
		1230
		1231	=item IO::AIO::npending
		1232
		1233	Returns the number of requests currently in the pending state (executed,
		1234	but not yet processed by poll_cb).
507		1235
508	=back	1236	=back
509		1237
510	=cut	1238	=cut
511		1239
…		…
523	or return undef;	1251	or return undef;
524		1252
525	*$sym	1253	*$sym
526	}	1254	}
527		1255
528	min_parallel 4;	1256	min_parallel 8;
529		1257
530	END {	1258	END { flush }
531	max_parallel 0;
532	}
533		1259
534	1;	1260	1;
535		1261
536	=head2 FORK BEHAVIOUR	1262	=head2 FORK BEHAVIOUR
		1263
		1264	This module should do "the right thing" when the process using it forks:
537		1265
538	Before the fork, IO::AIO enters a quiescent state where no requests	1266	Before the fork, IO::AIO enters a quiescent state where no requests
539	can be added in other threads and no results will be processed. After	1267	can be added in other threads and no results will be processed. After
540	the fork the parent simply leaves the quiescent state and continues	1268	the fork the parent simply leaves the quiescent state and continues
541	request/result processing, while the child clears the request/result	1269	request/result processing, while the child frees the request/result queue
542	queue (so the requests started before the fork will only be handled in	1270	(so that the requests started before the fork will only be handled in the
543	the parent). Threats will be started on demand until the limit ste in the	1271	parent). Threads will be started on demand until the limit set in the
544	parent process has been reached again.	1272	parent process has been reached again.
545		1273
		1274	In short: the parent will, after a short pause, continue as if fork had
		1275	not been called, while the child will act as if IO::AIO has not been used
		1276	yet.
		1277
		1278	=head2 MEMORY USAGE
		1279
		1280	Per-request usage:
		1281
		1282	Each aio request uses - depending on your architecture - around 100-200
		1283	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1284	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1285	scalars and other data passed into aio requests will also be locked and
		1286	will consume memory till the request has entered the done state.
		1287
		1288	This is now awfully much, so queuing lots of requests is not usually a
		1289	problem.
		1290
		1291	Per-thread usage:
		1292
		1293	In the execution phase, some aio requests require more memory for
		1294	temporary buffers, and each thread requires a stack and other data
		1295	structures (usually around 16k-128k, depending on the OS).
		1296
		1297	=head1 KNOWN BUGS
		1298
		1299	Known bugs will be fixed in the next release.
		1300
546	=head1 SEE ALSO	1301	=head1 SEE ALSO
547		1302
548	L<Coro>, L<Linux::AIO>.	1303	L<Coro::AIO>.
549		1304
550	=head1 AUTHOR	1305	=head1 AUTHOR
551		1306
552	Marc Lehmann <schmorp@schmorp.de>	1307	Marc Lehmann <schmorp@schmorp.de>
553	http://home.schmorp.de/	1308	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.42 by root, Mon Dec 26 18:15:23 2005 UTC vs. Revision 1.106 by root, Fri Jun 1 05:51:21 2007 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.42 by root, Mon Dec 26 18:15:23 2005 UTC vs.
Revision 1.106 by root, Fri Jun 1 05:51:21 2007 UTC