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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.54 by root, Sun Oct 22 00:19:05 2006 UTC vs.
Revision 1.100 by root, Sun Jan 7 21:36:58 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	use IO::AIO 2; # version has aio objects	21	# version 2+ has request and group objects
		22	use IO::AIO 2;
21		23
		24	aioreq_pri 4; # give next request a very high priority
22	my $req = aio_unlink "/tmp/file", sub { };	25	my $req = aio_unlink "/tmp/file", sub { };
23	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
24		27
25	# AnyEvent	28	my $grp = aio_group sub { print "all stats done\n" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration
26	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
27	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 });
28		34
29	# Event	35	# Event integration
30	Event->io (fd => IO::AIO::poll_fileno,	36	Event->io (fd => IO::AIO::poll_fileno,
31	poll => 'r',	37	poll => 'r',
32	cb => \&IO::AIO::poll_cb);	38	cb => \&IO::AIO::poll_cb);
33		39
34	# Glib/Gtk2	40	# Glib/Gtk2 integration
35	add_watch Glib::IO IO::AIO::poll_fileno,	41	add_watch Glib::IO IO::AIO::poll_fileno,
36	in => sub { IO::AIO::poll_cb; 1 };	42	in => sub { IO::AIO::poll_cb; 1 };
37		43
38	# Tk	44	# Tk integration
39	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
40	readable => \&IO::AIO::poll_cb);	46	readable => \&IO::AIO::poll_cb);
41		47
42	# Danga::Socket	48	# Danga::Socket integration
43	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
44	\&IO::AIO::poll_cb);	50	\&IO::AIO::poll_cb);
45		51
46
47	=head1 DESCRIPTION	52	=head1 DESCRIPTION
48		53
49	This module implements asynchronous I/O using whatever means your	54	This module implements asynchronous I/O using whatever means your
50	operating system supports.	55	operating system supports.
51		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
52	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
53	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
54	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
55	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
56	aio functions available on many operating systems. However, they are often	78	functions available on many operating systems. However, they are often
57	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
58	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
59	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.
60		83
61	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-)
62	currently not reentrant, so use appropriate locking yourself, always call	85	threads, it is currently not reentrant in any way, so use appropriate
63	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
64	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
65		184
66	=cut	185	=cut
67		186
68	package IO::AIO;	187	package IO::AIO;
69		188
…		…
71	use strict 'vars';	190	use strict 'vars';
72		191
73	use base 'Exporter';	192	use base 'Exporter';
74		193
75	BEGIN {	194	BEGIN {
76	our $VERSION = '1.99';	195	our $VERSION = '2.32';
77		196
78	our @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
79	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
80	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	199	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
81	aio_group);	200	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree);
82	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	201	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		202	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		203	min_parallel max_parallel max_idle
		204	nreqs nready npending nthreads
		205	max_poll_time max_poll_reqs);
83		206
84	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
85		208
86	require XSLoader;	209	require XSLoader;
87	XSLoader::load ("IO::AIO", $VERSION);	210	XSLoader::load ("IO::AIO", $VERSION);
88	}	211	}
89		212
90	=head1 FUNCTIONS	213	=head1 FUNCTIONS
91		214
92	=head2 AIO FUNCTIONS	215	=head2 AIO REQUEST FUNCTIONS
93		216
94	All the C<aio_*> calls are more or less thin wrappers around the syscall	217	All the C<aio_*> calls are more or less thin wrappers around the syscall
95	with the same name (sans C<aio_>). The arguments are similar or identical,	218	with the same name (sans C<aio_>). The arguments are similar or identical,
96	and they all accept an additional (and optional) C<$callback> argument	219	and they all accept an additional (and optional) C<$callback> argument
97	which must be a code reference. This code reference will get called with	220	which must be a code reference. This code reference will get called with
…		…
100	syscall has been executed asynchronously.	223	syscall has been executed asynchronously.
101		224
102	All functions expecting a filehandle keep a copy of the filehandle	225	All functions expecting a filehandle keep a copy of the filehandle
103	internally until the request has finished.	226	internally until the request has finished.
104		227
105	All non-composite requests (requests that are not broken down into
106	multiple requests) return objects of type L<IO::AIO::REQ> that allow	228	All functions return request objects of type L<IO::AIO::REQ> that allow
107	further manipulation of running requests.	229	further manipulation of those requests while they are in-flight.
108		230
109	The pathnames you pass to these routines I<must> be absolute and	231	The pathnames you pass to these routines I<must> be absolute and
110	encoded in byte form. The reason for the former is that at the time the	232	encoded as octets. The reason for the former is that at the time the
111	request is being executed, the current working directory could have	233	request is being executed, the current working directory could have
112	changed. Alternatively, you can make sure that you never change the	234	changed. Alternatively, you can make sure that you never change the
113	current working directory.	235	current working directory anywhere in the program and then use relative
		236	paths.
114		237
115	To encode pathnames to byte form, either make sure you either: a)	238	To encode pathnames as octets, either make sure you either: a) always pass
116	always pass in filenames you got from outside (command line, readdir	239	in filenames you got from outside (command line, readdir etc.) without
117	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	240	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
118	your pathnames to the locale (or other) encoding in effect in the user	241	your pathnames to the locale (or other) encoding in effect in the user
119	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	242	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
120	use something else.	243	use something else to ensure your scalar has the correct contents.
		244
		245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		246	handles correctly wether it is set or not.
121		247
122	=over 4	248	=over 4
		249
		250	=item $prev_pri = aioreq_pri [$pri]
		251
		252	Returns the priority value that would be used for the next request and, if
		253	C<$pri> is given, sets the priority for the next aio request.
		254
		255	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		256	and C<4>, respectively. Requests with higher priority will be serviced
		257	first.
		258
		259	The priority will be reset to C<0> after each call to one of the C<aio_*>
		260	functions.
		261
		262	Example: open a file with low priority, then read something from it with
		263	higher priority so the read request is serviced before other low priority
		264	open requests (potentially spamming the cache):
		265
		266	aioreq_pri -3;
		267	aio_open ..., sub {
		268	return unless $_[0];
		269
		270	aioreq_pri -2;
		271	aio_read $_[0], ..., sub {
		272	...
		273	};
		274	};
		275
		276	=item aioreq_nice $pri_adjust
		277
		278	Similar to C<aioreq_pri>, but subtracts the given value from the current
		279	priority, so the effect is cumulative.
123		280
124	=item aio_open $pathname, $flags, $mode, $callback->($fh)	281	=item aio_open $pathname, $flags, $mode, $callback->($fh)
125		282
126	Asynchronously open or create a file and call the callback with a newly	283	Asynchronously open or create a file and call the callback with a newly
127	created filehandle for the file.	284	created filehandle for the file.
…		…
178	aio_read $fh, 7, 15, $buffer, 0, sub {	335	aio_read $fh, 7, 15, $buffer, 0, sub {
179	$_[0] > 0 or die "read error: $!";	336	$_[0] > 0 or die "read error: $!";
180	print "read $_[0] bytes: <$buffer>\n";	337	print "read $_[0] bytes: <$buffer>\n";
181	};	338	};
182		339
183	=item aio_move $srcpath, $dstpath, $callback->($status)
184
185	Try to move the I<file> (directories not supported as either source or
186	destination) from C<$srcpath> to C<$dstpath> and call the callback with
187	the C<0> (error) or C<-1> ok.
188
189	This is a composite request that tries to rename(2) the file first. If
190	rename files with C<EXDEV>, it creates the destination file with mode 0200
191	and copies the contents of the source file into it using C<aio_sendfile>,
192	followed by restoring atime, mtime, access mode and uid/gid, in that
193	order, and unlinking the C<$srcpath>.
194
195	If an error occurs, the partial destination file will be unlinked, if
196	possible, except when setting atime, mtime, access mode and uid/gid, where
197	errors are being ignored.
198
199	=cut
200
201	sub aio_move($$$) {
202	my ($src, $dst, $cb) = @_;
203
204	aio_rename $src, $dst, sub {
205	if ($_[0] && $! == EXDEV) {
206	aio_open $src, O_RDONLY, 0, sub {
207	if (my $src_fh = $_[0]) {
208	my @stat = stat $src_fh;
209
210	aio_open $dst, O_WRONLY, 0200, sub {
211	if (my $dst_fh = $_[0]) {
212	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
213	close $src_fh;
214
215	if ($_[0] == $stat[7]) {
216	utime $stat[8], $stat[9], $dst;
217	chmod $stat[2] & 07777, $dst_fh;
218	chown $stat[4], $stat[5], $dst_fh;
219	close $dst_fh;
220
221	aio_unlink $src, sub {
222	$cb->($_[0]);
223	};
224	} else {
225	my $errno = $!;
226	aio_unlink $dst, sub {
227	$! = $errno;
228	$cb->(-1);
229	};
230	}
231	};
232	} else {
233	$cb->(-1);
234	}
235	},
236
237	} else {
238	$cb->(-1);
239	}
240	};
241	} else {
242	$cb->($_[0]);
243	}
244	};
245	}
246
247	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	340	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
248		341
249	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	342	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
250	reading at byte offset C<$in_offset>, and starts writing at the current	343	reading at byte offset C<$in_offset>, and starts writing at the current
251	file offset of C<$out_fh>. Because of that, it is not safe to issue more	344	file offset of C<$out_fh>. Because of that, it is not safe to issue more
…		…
306	=item aio_unlink $pathname, $callback->($status)	399	=item aio_unlink $pathname, $callback->($status)
307		400
308	Asynchronously unlink (delete) a file and call the callback with the	401	Asynchronously unlink (delete) a file and call the callback with the
309	result code.	402	result code.
310		403
		404	=item aio_mknod $path, $mode, $dev, $callback->($status)
		405
		406	[EXPERIMENTAL]
		407
		408	Asynchronously create a device node (or fifo). See mknod(2).
		409
		410	The only (POSIX-) portable way of calling this function is:
		411
		412	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		413
311	=item aio_link $srcpath, $dstpath, $callback->($status)	414	=item aio_link $srcpath, $dstpath, $callback->($status)
312		415
313	Asynchronously create a new link to the existing object at C<$srcpath> at	416	Asynchronously create a new link to the existing object at C<$srcpath> at
314	the path C<$dstpath> and call the callback with the result code.	417	the path C<$dstpath> and call the callback with the result code.
315		418
316	=item aio_symlink $srcpath, $dstpath, $callback->($status)	419	=item aio_symlink $srcpath, $dstpath, $callback->($status)
317		420
318	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	421	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
319	the path C<$dstpath> and call the callback with the result code.	422	the path C<$dstpath> and call the callback with the result code.
		423
		424	=item aio_readlink $path, $callback->($link)
		425
		426	Asynchronously read the symlink specified by C<$path> and pass it to
		427	the callback. If an error occurs, nothing or undef gets passed to the
		428	callback.
320		429
321	=item aio_rename $srcpath, $dstpath, $callback->($status)	430	=item aio_rename $srcpath, $dstpath, $callback->($status)
322		431
323	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	432	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
324	rename(2) and call the callback with the result code.	433	rename(2) and call the callback with the result code.
…		…
335	sorted, and will B<NOT> include the C<.> and C<..> entries.	444	sorted, and will B<NOT> include the C<.> and C<..> entries.
336		445
337	The callback a single argument which is either C<undef> or an array-ref	446	The callback a single argument which is either C<undef> or an array-ref
338	with the filenames.	447	with the filenames.
339		448
		449	=item aio_load $path, $data, $callback->($status)
		450
		451	This is a composite request that tries to fully load the given file into
		452	memory. Status is the same as with aio_read.
		453
		454	=cut
		455
		456	sub aio_load($$;$) {
		457	aio_block {
		458	my ($path, undef, $cb) = @_;
		459	my $data = \$_[1];
		460
		461	my $pri = aioreq_pri;
		462	my $grp = aio_group $cb;
		463
		464	aioreq_pri $pri;
		465	add $grp aio_open $path, O_RDONLY, 0, sub {
		466	my ($fh) = @_
		467	or return $grp->result (-1);
		468
		469	aioreq_pri $pri;
		470	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		471	$grp->result ($_[0]);
		472	};
		473	};
		474
		475	$grp
		476	}
		477	}
		478
		479	=item aio_copy $srcpath, $dstpath, $callback->($status)
		480
		481	Try to copy the I<file> (directories not supported as either source or
		482	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		483	the C<0> (error) or C<-1> ok.
		484
		485	This is a composite request that it creates the destination file with
		486	mode 0200 and copies the contents of the source file into it using
		487	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		488	uid/gid, in that order.
		489
		490	If an error occurs, the partial destination file will be unlinked, if
		491	possible, except when setting atime, mtime, access mode and uid/gid, where
		492	errors are being ignored.
		493
		494	=cut
		495
		496	sub aio_copy($$;$) {
		497	aio_block {
		498	my ($src, $dst, $cb) = @_;
		499
		500	my $pri = aioreq_pri;
		501	my $grp = aio_group $cb;
		502
		503	aioreq_pri $pri;
		504	add $grp aio_open $src, O_RDONLY, 0, sub {
		505	if (my $src_fh = $_[0]) {
		506	my @stat = stat $src_fh;
		507
		508	aioreq_pri $pri;
		509	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		510	if (my $dst_fh = $_[0]) {
		511	aioreq_pri $pri;
		512	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		513	if ($_[0] == $stat[7]) {
		514	$grp->result (0);
		515	close $src_fh;
		516
		517	# those should not normally block. should. should.
		518	utime $stat[8], $stat[9], $dst;
		519	chmod $stat[2] & 07777, $dst_fh;
		520	chown $stat[4], $stat[5], $dst_fh;
		521	close $dst_fh;
		522	} else {
		523	$grp->result (-1);
		524	close $src_fh;
		525	close $dst_fh;
		526
		527	aioreq $pri;
		528	add $grp aio_unlink $dst;
		529	}
		530	};
		531	} else {
		532	$grp->result (-1);
		533	}
		534	},
		535
		536	} else {
		537	$grp->result (-1);
		538	}
		539	};
		540
		541	$grp
		542	}
		543	}
		544
		545	=item aio_move $srcpath, $dstpath, $callback->($status)
		546
		547	Try to move the I<file> (directories not supported as either source or
		548	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		549	the C<0> (error) or C<-1> ok.
		550
		551	This is a composite request that tries to rename(2) the file first. If
		552	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		553	that is successful, unlinking the C<$srcpath>.
		554
		555	=cut
		556
		557	sub aio_move($$;$) {
		558	aio_block {
		559	my ($src, $dst, $cb) = @_;
		560
		561	my $pri = aioreq_pri;
		562	my $grp = aio_group $cb;
		563
		564	aioreq_pri $pri;
		565	add $grp aio_rename $src, $dst, sub {
		566	if ($_[0] && $! == EXDEV) {
		567	aioreq_pri $pri;
		568	add $grp aio_copy $src, $dst, sub {
		569	$grp->result ($_[0]);
		570
		571	if (!$_[0]) {
		572	aioreq_pri $pri;
		573	add $grp aio_unlink $src;
		574	}
		575	};
		576	} else {
		577	$grp->result ($_[0]);
		578	}
		579	};
		580
		581	$grp
		582	}
		583	}
		584
340	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	585	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
341		586
342	Scans a directory (similar to C<aio_readdir>) but additionally tries to	587	Scans a directory (similar to C<aio_readdir>) but additionally tries to
343	separate the entries of directory C<$path> into two sets of names, ones	588	efficiently separate the entries of directory C<$path> into two sets of
344	you can recurse into (directories or links to them), and ones you cannot	589	names, directories you can recurse into (directories), and ones you cannot
345	recurse into (everything else).	590	recurse into (everything else, including symlinks to directories).
346		591
347	C<aio_scandir> is a composite request that consists of many sub	592	C<aio_scandir> is a composite request that creates of many sub requests_
348	requests. C<$maxreq> specifies the maximum number of outstanding aio	593	C<$maxreq> specifies the maximum number of outstanding aio requests that
349	requests that this function generates. If it is C<< <= 0 >>, then a	594	this function generates. If it is C<< <= 0 >>, then a suitable default
350	suitable default will be chosen (currently 8).	595	will be chosen (currently 4).
351		596
352	On error, the callback is called without arguments, otherwise it receives	597	On error, the callback is called without arguments, otherwise it receives
353	two array-refs with path-relative entry names.	598	two array-refs with path-relative entry names.
354		599
355	Example:	600	Example:
…		…
389	as those tend to return 0 or 1 as link counts, which disables the	634	as those tend to return 0 or 1 as link counts, which disables the
390	directory counting heuristic.	635	directory counting heuristic.
391		636
392	=cut	637	=cut
393		638
394	sub aio_scandir($$$) {	639	sub aio_scandir($$;$) {
		640	aio_block {
395	my ($path, $maxreq, $cb) = @_;	641	my ($path, $maxreq, $cb) = @_;
396		642
		643	my $pri = aioreq_pri;
		644
		645	my $grp = aio_group $cb;
		646
397	$maxreq = 8 if $maxreq <= 0;	647	$maxreq = 4 if $maxreq <= 0;
398		648
399	# stat once	649	# stat once
		650	aioreq_pri $pri;
400	aio_stat $path, sub {	651	add $grp aio_stat $path, sub {
401	return $cb->() if $_[0];	652	return $grp->result () if $_[0];
402	my $now = time;	653	my $now = time;
403	my $hash1 = join ":", (stat _)[0,1,3,7,9];	654	my $hash1 = join ":", (stat _)[0,1,3,7,9];
404		655
405	# read the directory entries	656	# read the directory entries
		657	aioreq_pri $pri;
406	aio_readdir $path, sub {	658	add $grp aio_readdir $path, sub {
407	my $entries = shift	659	my $entries = shift
408	or return $cb->();	660	or return $grp->result ();
409		661
410	# stat the dir another time	662	# stat the dir another time
		663	aioreq_pri $pri;
411	aio_stat $path, sub {	664	add $grp aio_stat $path, sub {
412	my $hash2 = join ":", (stat _)[0,1,3,7,9];	665	my $hash2 = join ":", (stat _)[0,1,3,7,9];
413		666
414	my $ndirs;	667	my $ndirs;
415		668
416	# take the slow route if anything looks fishy	669	# take the slow route if anything looks fishy
417	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	670	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
418	$ndirs = -1;	671	$ndirs = -1;
419	} else {	672	} else {
420	# if nlink == 2, we are finished	673	# if nlink == 2, we are finished
421	# on non-posix-fs's, we rely on nlink < 2	674	# on non-posix-fs's, we rely on nlink < 2
422	$ndirs = (stat _)[3] - 2	675	$ndirs = (stat _)[3] - 2
423	or return $cb->([], $entries);	676	or return $grp->result ([], $entries);
424	}
425
426	# sort into likely dirs and likely nondirs
427	# dirs == files without ".", short entries first
428	$entries = [map $_->[0],
429	sort { $b->[1] cmp $a->[1] }
430	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
431	@$entries];
432
433	my (@dirs, @nondirs);
434
435	my ($statcb, $schedcb);
436	my $nreq = 0;
437
438	$schedcb = sub {
439	if (@$entries) {
440	if ($nreq < $maxreq) {
441	my $ent = pop @$entries;
442	$nreq++;
443	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
444	}
445	} elsif (!$nreq) {
446	# finished
447	undef $statcb;
448	undef $schedcb;
449	$cb->(\@dirs, \@nondirs) if $cb;
450	undef $cb;
451	}	677	}
		678
		679	# sort into likely dirs and likely nondirs
		680	# dirs == files without ".", short entries first
		681	$entries = [map $_->[0],
		682	sort { $b->[1] cmp $a->[1] }
		683	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		684	@$entries];
		685
		686	my (@dirs, @nondirs);
		687
		688	my $statgrp = add $grp aio_group sub {
		689	$grp->result (\@dirs, \@nondirs);
		690	};
		691
		692	limit $statgrp $maxreq;
		693	feed $statgrp sub {
		694	return unless @$entries;
		695	my $entry = pop @$entries;
		696
		697	aioreq_pri $pri;
		698	add $statgrp aio_stat "$path/$entry/.", sub {
		699	if ($_[0] < 0) {
		700	push @nondirs, $entry;
		701	} else {
		702	# need to check for real directory
		703	aioreq_pri $pri;
		704	add $statgrp aio_lstat "$path/$entry", sub {
		705	if (-d _) {
		706	push @dirs, $entry;
		707
		708	unless (--$ndirs) {
		709	push @nondirs, @$entries;
		710	feed $statgrp;
		711	}
		712	} else {
		713	push @nondirs, $entry;
		714	}
		715	}
		716	}
		717	};
		718	};
452	};	719	};
453	$statcb = sub {
454	my ($status, $entry) = @_;
455
456	if ($status < 0) {
457	$nreq--;
458	push @nondirs, $entry;
459	&$schedcb;
460	} else {
461	# need to check for real directory
462	aio_lstat "$path/$entry", sub {
463	$nreq--;
464
465	if (-d _) {
466	push @dirs, $entry;
467
468	if (!--$ndirs) {
469	push @nondirs, @$entries;
470	$entries = [];
471	}
472	} else {
473	push @nondirs, $entry;
474	}
475
476	&$schedcb;
477	}
478	}
479	};
480
481	&$schedcb while @$entries && $nreq < $maxreq;
482	};	720	};
483	};	721	};
		722
		723	$grp
484	};	724	}
		725	}
		726
		727	=item aio_rmtree $path, $callback->($status)
		728
		729	Delete a directory tree starting (and including) C<$path>, return the
		730	status of the final C<rmdir> only. This is a composite request that
		731	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		732	everything else.
		733
		734	=cut
		735
		736	sub aio_rmtree;
		737	sub aio_rmtree($;$) {
		738	aio_block {
		739	my ($path, $cb) = @_;
		740
		741	my $pri = aioreq_pri;
		742	my $grp = aio_group $cb;
		743
		744	aioreq_pri $pri;
		745	add $grp aio_scandir $path, 0, sub {
		746	my ($dirs, $nondirs) = @_;
		747
		748	my $dirgrp = aio_group sub {
		749	add $grp aio_rmdir $path, sub {
		750	$grp->result ($_[0]);
		751	};
		752	};
		753
		754	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		755	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		756
		757	add $grp $dirgrp;
		758	};
		759
		760	$grp
		761	}
485	}	762	}
486		763
487	=item aio_fsync $fh, $callback->($status)	764	=item aio_fsync $fh, $callback->($status)
488		765
489	Asynchronously call fsync on the given filehandle and call the callback	766	Asynchronously call fsync on the given filehandle and call the callback
…		…
495	callback with the fdatasync result code.	772	callback with the fdatasync result code.
496		773
497	If this call isn't available because your OS lacks it or it couldn't be	774	If this call isn't available because your OS lacks it or it couldn't be
498	detected, it will be emulated by calling C<fsync> instead.	775	detected, it will be emulated by calling C<fsync> instead.
499		776
500	=item aio_group $callback->()	777	=item aio_group $callback->(...)
501		778
		779	This is a very special aio request: Instead of doing something, it is a
		780	container for other aio requests, which is useful if you want to bundle
		781	many requests into a single, composite, request with a definite callback
		782	and the ability to cancel the whole request with its subrequests.
		783
		784	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		785	for more info.
		786
		787	Example:
		788
		789	my $grp = aio_group sub {
		790	print "all stats done\n";
		791	};
		792
		793	add $grp
		794	(aio_stat ...),
		795	(aio_stat ...),
		796	...;
		797
		798	=item aio_nop $callback->()
		799
		800	This is a special request - it does nothing in itself and is only used for
		801	side effects, such as when you want to add a dummy request to a group so
		802	that finishing the requests in the group depends on executing the given
		803	code.
		804
		805	While this request does nothing, it still goes through the execution
		806	phase and still requires a worker thread. Thus, the callback will not
		807	be executed immediately but only after other requests in the queue have
		808	entered their execution phase. This can be used to measure request
		809	latency.
		810
502	=item aio_sleep $fractional_seconds, $callback->() NOT EXPORTED	811	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
503		812
504	Mainly used for debugging and benchmarking, this aio request puts one of	813	Mainly used for debugging and benchmarking, this aio request puts one of
505	the request workers to sleep for the given time.	814	the request workers to sleep for the given time.
506		815
		816	While it is theoretically handy to have simple I/O scheduling requests
		817	like sleep and file handle readable/writable, the overhead this creates is
		818	immense (it blocks a thread for a long time) so do not use this function
		819	except to put your application under artificial I/O pressure.
		820
507	=back	821	=back
508		822
509	=head2 IO::AIO::REQ CLASS	823	=head2 IO::AIO::REQ CLASS
510		824
511	All non-aggregate C<aio_*> functions return an object of this class when	825	All non-aggregate C<aio_*> functions return an object of this class when
512	called in non-void context.	826	called in non-void context.
513		827
514	A request always moves through the following five states in its lifetime,
515	in order: B<ready> (request has been created, but has not been executed
516	yet), B<execute> (request is currently being executed), B<pending>
517	(request has been executed but callback has not been called yet),
518	B<result> (results are being processed synchronously, includes calling the
519	callback) and B<done> (request has reached the end of its lifetime and
520	holds no resources anymore).
521
522	=over 4	828	=over 4
523		829
524	=item $req->cancel	830	=item cancel $req
525		831
526	Cancels the request, if possible. Has the effect of skipping execution	832	Cancels the request, if possible. Has the effect of skipping execution
527	when entering the B<execute> state and skipping calling the callback when	833	when entering the B<execute> state and skipping calling the callback when
528	entering the the B<result> state, but will leave the request otherwise	834	entering the the B<result> state, but will leave the request otherwise
529	untouched. That means that requests that currently execute will not be	835	untouched. That means that requests that currently execute will not be
530	stopped and resources held by the request will not be freed prematurely.	836	stopped and resources held by the request will not be freed prematurely.
531		837
		838	=item cb $req $callback->(...)
		839
		840	Replace (or simply set) the callback registered to the request.
		841
532	=back	842	=back
533		843
		844	=head2 IO::AIO::GRP CLASS
		845
		846	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		847	objects of this class, too.
		848
		849	A IO::AIO::GRP object is a special request that can contain multiple other
		850	aio requests.
		851
		852	You create one by calling the C<aio_group> constructing function with a
		853	callback that will be called when all contained requests have entered the
		854	C<done> state:
		855
		856	my $grp = aio_group sub {
		857	print "all requests are done\n";
		858	};
		859
		860	You add requests by calling the C<add> method with one or more
		861	C<IO::AIO::REQ> objects:
		862
		863	$grp->add (aio_unlink "...");
		864
		865	add $grp aio_stat "...", sub {
		866	$_[0] or return $grp->result ("error");
		867
		868	# add another request dynamically, if first succeeded
		869	add $grp aio_open "...", sub {
		870	$grp->result ("ok");
		871	};
		872	};
		873
		874	This makes it very easy to create composite requests (see the source of
		875	C<aio_move> for an application) that work and feel like simple requests.
		876
		877	=over 4
		878
		879	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		880	C<IO::AIO::poll_cb>, just like any other request.
		881
		882	=item * They can be canceled like any other request. Canceling will cancel not
		883	only the request itself, but also all requests it contains.
		884
		885	=item * They can also can also be added to other IO::AIO::GRP objects.
		886
		887	=item * You must not add requests to a group from within the group callback (or
		888	any later time).
		889
		890	=back
		891
		892	Their lifetime, simplified, looks like this: when they are empty, they
		893	will finish very quickly. If they contain only requests that are in the
		894	C<done> state, they will also finish. Otherwise they will continue to
		895	exist.
		896
		897	That means after creating a group you have some time to add requests. And
		898	in the callbacks of those requests, you can add further requests to the
		899	group. And only when all those requests have finished will the the group
		900	itself finish.
		901
		902	=over 4
		903
		904	=item add $grp ...
		905
		906	=item $grp->add (...)
		907
		908	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		909	be added, including other groups, as long as you do not create circular
		910	dependencies.
		911
		912	Returns all its arguments.
		913
		914	=item $grp->cancel_subs
		915
		916	Cancel all subrequests and clears any feeder, but not the group request
		917	itself. Useful when you queued a lot of events but got a result early.
		918
		919	=item $grp->result (...)
		920
		921	Set the result value(s) that will be passed to the group callback when all
		922	subrequests have finished and set thre groups errno to the current value
		923	of errno (just like calling C<errno> without an error number). By default,
		924	no argument will be passed and errno is zero.
		925
		926	=item $grp->errno ([$errno])
		927
		928	Sets the group errno value to C<$errno>, or the current value of errno
		929	when the argument is missing.
		930
		931	Every aio request has an associated errno value that is restored when
		932	the callback is invoked. This method lets you change this value from its
		933	default (0).
		934
		935	Calling C<result> will also set errno, so make sure you either set C<$!>
		936	before the call to C<result>, or call c<errno> after it.
		937
		938	=item feed $grp $callback->($grp)
		939
		940	Sets a feeder/generator on this group: every group can have an attached
		941	generator that generates requests if idle. The idea behind this is that,
		942	although you could just queue as many requests as you want in a group,
		943	this might starve other requests for a potentially long time. For
		944	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		945	requests, delaying any later requests for a long time.
		946
		947	To avoid this, and allow incremental generation of requests, you can
		948	instead a group and set a feeder on it that generates those requests. The
		949	feed callback will be called whenever there are few enough (see C<limit>,
		950	below) requests active in the group itself and is expected to queue more
		951	requests.
		952
		953	The feed callback can queue as many requests as it likes (i.e. C<add> does
		954	not impose any limits).
		955
		956	If the feed does not queue more requests when called, it will be
		957	automatically removed from the group.
		958
		959	If the feed limit is C<0>, it will be set to C<2> automatically.
		960
		961	Example:
		962
		963	# stat all files in @files, but only ever use four aio requests concurrently:
		964
		965	my $grp = aio_group sub { print "finished\n" };
		966	limit $grp 4;
		967	feed $grp sub {
		968	my $file = pop @files
		969	or return;
		970
		971	add $grp aio_stat $file, sub { ... };
		972	};
		973
		974	=item limit $grp $num
		975
		976	Sets the feeder limit for the group: The feeder will be called whenever
		977	the group contains less than this many requests.
		978
		979	Setting the limit to C<0> will pause the feeding process.
		980
		981	=back
		982
534	=head2 SUPPORT FUNCTIONS	983	=head2 SUPPORT FUNCTIONS
		984
		985	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
535		986
536	=over 4	987	=over 4
537		988
538	=item $fileno = IO::AIO::poll_fileno	989	=item $fileno = IO::AIO::poll_fileno
539		990
…		…
544		995
545	See C<poll_cb> for an example.	996	See C<poll_cb> for an example.
546		997
547	=item IO::AIO::poll_cb	998	=item IO::AIO::poll_cb
548		999
549	Process all outstanding events on the result pipe. You have to call this	1000	Process some outstanding events on the result pipe. You have to call this
550	regularly. Returns the number of events processed. Returns immediately	1001	regularly. Returns the number of events processed. Returns immediately
551	when no events are outstanding.	1002	when no events are outstanding. The amount of events processed depends on
		1003	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1004
		1005	If not all requests were processed for whatever reason, the filehandle
		1006	will still be ready when C<poll_cb> returns.
552		1007
553	Example: Install an Event watcher that automatically calls	1008	Example: Install an Event watcher that automatically calls
554	IO::AIO::poll_cb with high priority:	1009	IO::AIO::poll_cb with high priority:
555		1010
556	Event->io (fd => IO::AIO::poll_fileno,	1011	Event->io (fd => IO::AIO::poll_fileno,
557	poll => 'r', async => 1,	1012	poll => 'r', async => 1,
558	cb => \&IO::AIO::poll_cb);	1013	cb => \&IO::AIO::poll_cb);
559		1014
		1015	=item IO::AIO::max_poll_reqs $nreqs
		1016
		1017	=item IO::AIO::max_poll_time $seconds
		1018
		1019	These set the maximum number of requests (default C<0>, meaning infinity)
		1020	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1021	the maximum amount of time (default C<0>, meaning infinity) spent in
		1022	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1023	of time C<poll_cb> is allowed to use).
		1024
		1025	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1026	syscall per request processed, which is not normally a problem unless your
		1027	callbacks are really really fast or your OS is really really slow (I am
		1028	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1029
		1030	Setting these is useful if you want to ensure some level of
		1031	interactiveness when perl is not fast enough to process all requests in
		1032	time.
		1033
		1034	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1035
		1036	Example: Install an Event watcher that automatically calls
		1037	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1038	program get the CPU sometimes even under high AIO load.
		1039
		1040	# try not to spend much more than 0.1s in poll_cb
		1041	IO::AIO::max_poll_time 0.1;
		1042
		1043	# use a low priority so other tasks have priority
		1044	Event->io (fd => IO::AIO::poll_fileno,
		1045	poll => 'r', nice => 1,
		1046	cb => &IO::AIO::poll_cb);
		1047
560	=item IO::AIO::poll_wait	1048	=item IO::AIO::poll_wait
561		1049
		1050	If there are any outstanding requests and none of them in the result
562	Wait till the result filehandle becomes ready for reading (simply does a	1051	phase, wait till the result filehandle becomes ready for reading (simply
563	C<select> on the filehandle. This is useful if you want to synchronously wait	1052	does a C<select> on the filehandle. This is useful if you want to
564	for some requests to finish).	1053	synchronously wait for some requests to finish).
565		1054
566	See C<nreqs> for an example.	1055	See C<nreqs> for an example.
567		1056
		1057	=item IO::AIO::poll
		1058
		1059	Waits until some requests have been handled.
		1060
		1061	Returns the number of requests processed, but is otherwise strictly
		1062	equivalent to:
		1063
		1064	IO::AIO::poll_wait, IO::AIO::poll_cb
		1065
568	=item IO::AIO::nreqs	1066	=item IO::AIO::flush
569		1067
570	Returns the number of requests currently outstanding (i.e. for which their	1068	Wait till all outstanding AIO requests have been handled.
571	callback has not been invoked yet).
572		1069
573	Example: wait till there are no outstanding requests anymore:	1070	Strictly equivalent to:
574		1071
575	IO::AIO::poll_wait, IO::AIO::poll_cb	1072	IO::AIO::poll_wait, IO::AIO::poll_cb
576	while IO::AIO::nreqs;	1073	while IO::AIO::nreqs;
577		1074
578	=item IO::AIO::flush	1075	=head3 CONTROLLING THE NUMBER OF THREADS
579
580	Wait till all outstanding AIO requests have been handled.
581
582	Strictly equivalent to:
583
584	IO::AIO::poll_wait, IO::AIO::poll_cb
585	while IO::AIO::nreqs;
586
587	=item IO::AIO::poll
588
589	Waits until some requests have been handled.
590
591	Strictly equivalent to:
592
593	IO::AIO::poll_wait, IO::AIO::poll_cb
594	if IO::AIO::nreqs;
595		1076
596	=item IO::AIO::min_parallel $nthreads	1077	=item IO::AIO::min_parallel $nthreads
597		1078
598	Set the minimum number of AIO threads to C<$nthreads>. The current default	1079	Set the minimum number of AIO threads to C<$nthreads>. The current
599	is C<4>, which means four asynchronous operations can be done at one time	1080	default is C<8>, which means eight asynchronous operations can execute
600	(the number of outstanding operations, however, is unlimited).	1081	concurrently at any one time (the number of outstanding requests,
		1082	however, is unlimited).
601		1083
602	IO::AIO starts threads only on demand, when an AIO request is queued and	1084	IO::AIO starts threads only on demand, when an AIO request is queued and
603	no free thread exists.	1085	no free thread exists. Please note that queueing up a hundred requests can
		1086	create demand for a hundred threads, even if it turns out that everything
		1087	is in the cache and could have been processed faster by a single thread.
604		1088
605	It is recommended to keep the number of threads low, as some Linux	1089	It is recommended to keep the number of threads relatively low, as some
606	kernel versions will scale negatively with the number of threads (higher	1090	Linux kernel versions will scale negatively with the number of threads
607	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1091	(higher parallelity => MUCH higher latency). With current Linux 2.6
608	threads should be fine.	1092	versions, 4-32 threads should be fine.
609		1093
610	Under most circumstances you don't need to call this function, as the	1094	Under most circumstances you don't need to call this function, as the
611	module selects a default that is suitable for low to moderate load.	1095	module selects a default that is suitable for low to moderate load.
612		1096
613	=item IO::AIO::max_parallel $nthreads	1097	=item IO::AIO::max_parallel $nthreads
…		…
622	This module automatically runs C<max_parallel 0> at program end, to ensure	1106	This module automatically runs C<max_parallel 0> at program end, to ensure
623	that all threads are killed and that there are no outstanding requests.	1107	that all threads are killed and that there are no outstanding requests.
624		1108
625	Under normal circumstances you don't need to call this function.	1109	Under normal circumstances you don't need to call this function.
626		1110
		1111	=item IO::AIO::max_idle $nthreads
		1112
		1113	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1114	threads that did not get a request to process within 10 seconds). That
		1115	means if a thread becomes idle while C<$nthreads> other threads are also
		1116	idle, it will free its resources and exit.
		1117
		1118	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1119	to allow for extremely high load situations, but want to free resources
		1120	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1121
		1122	The default is probably ok in most situations, especially if thread
		1123	creation is fast. If thread creation is very slow on your system you might
		1124	want to use larger values.
		1125
627	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1126	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1127
		1128	This is a very bad function to use in interactive programs because it
		1129	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1130	use an C<aio_group> together with a feed callback.
628		1131
629	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1132	Sets the maximum number of outstanding requests to C<$nreqs>. If you
630	try to queue up more than this number of requests, the caller will block until	1133	to queue up more than this number of requests, the next call to the
631	some requests have been handled.	1134	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1135	function will block until the limit is no longer exceeded.
632		1136
633	The default is very large, so normally there is no practical limit. If you	1137	The default value is very large, so there is no practical limit on the
634	queue up many requests in a loop it often improves speed if you set	1138	number of outstanding requests.
635	this to a relatively low number, such as C<100>.
636		1139
637	Under normal circumstances you don't need to call this function.	1140	You can still queue as many requests as you want. Therefore,
		1141	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1142	as a stop gap to shield against fatal memory overflow (with large values).
		1143
		1144	=head3 STATISTICAL INFORMATION
		1145
		1146	=item IO::AIO::nreqs
		1147
		1148	Returns the number of requests currently in the ready, execute or pending
		1149	states (i.e. for which their callback has not been invoked yet).
		1150
		1151	Example: wait till there are no outstanding requests anymore:
		1152
		1153	IO::AIO::poll_wait, IO::AIO::poll_cb
		1154	while IO::AIO::nreqs;
		1155
		1156	=item IO::AIO::nready
		1157
		1158	Returns the number of requests currently in the ready state (not yet
		1159	executed).
		1160
		1161	=item IO::AIO::npending
		1162
		1163	Returns the number of requests currently in the pending state (executed,
		1164	but not yet processed by poll_cb).
638		1165
639	=back	1166	=back
640		1167
641	=cut	1168	=cut
642		1169
…		…
654	or return undef;	1181	or return undef;
655		1182
656	*$sym	1183	*$sym
657	}	1184	}
658		1185
659	min_parallel 4;	1186	min_parallel 8;
660		1187
661	END {	1188	END { flush }
662	max_parallel 0;
663	}
664		1189
665	1;	1190	1;
666		1191
667	=head2 FORK BEHAVIOUR	1192	=head2 FORK BEHAVIOUR
668		1193
669	This module should do "the right thing" when the process using it forks:	1194	This module should do "the right thing" when the process using it forks:
670		1195
671	Before the fork, IO::AIO enters a quiescent state where no requests	1196	Before the fork, IO::AIO enters a quiescent state where no requests
672	can be added in other threads and no results will be processed. After	1197	can be added in other threads and no results will be processed. After
673	the fork the parent simply leaves the quiescent state and continues	1198	the fork the parent simply leaves the quiescent state and continues
674	request/result processing, while the child clears the request/result	1199	request/result processing, while the child frees the request/result queue
675	queue (so the requests started before the fork will only be handled in	1200	(so that the requests started before the fork will only be handled in the
676	the parent). Threads will be started on demand until the limit ste in the	1201	parent). Threads will be started on demand until the limit set in the
677	parent process has been reached again.	1202	parent process has been reached again.
678		1203
679	In short: the parent will, after a short pause, continue as if fork had	1204	In short: the parent will, after a short pause, continue as if fork had
680	not been called, while the child will act as if IO::AIO has not been used	1205	not been called, while the child will act as if IO::AIO has not been used
681	yet.	1206	yet.
682		1207
		1208	=head2 MEMORY USAGE
		1209
		1210	Per-request usage:
		1211
		1212	Each aio request uses - depending on your architecture - around 100-200
		1213	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1214	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1215	scalars and other data passed into aio requests will also be locked and
		1216	will consume memory till the request has entered the done state.
		1217
		1218	This is now awfully much, so queuing lots of requests is not usually a
		1219	problem.
		1220
		1221	Per-thread usage:
		1222
		1223	In the execution phase, some aio requests require more memory for
		1224	temporary buffers, and each thread requires a stack and other data
		1225	structures (usually around 16k-128k, depending on the OS).
		1226
		1227	=head1 KNOWN BUGS
		1228
		1229	Known bugs will be fixed in the next release.
		1230
683	=head1 SEE ALSO	1231	=head1 SEE ALSO
684		1232
685	L<Coro>, L<Linux::AIO> (obsolete).	1233	L<Coro::AIO>.
686		1234
687	=head1 AUTHOR	1235	=head1 AUTHOR
688		1236
689	Marc Lehmann <schmorp@schmorp.de>	1237	Marc Lehmann <schmorp@schmorp.de>
690	http://home.schmorp.de/	1238	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.54 by root, Sun Oct 22 00:19:05 2006 UTC vs. Revision 1.100 by root, Sun Jan 7 21:36:58 2007 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.54 by root, Sun Oct 22 00:19:05 2006 UTC vs.
Revision 1.100 by root, Sun Jan 7 21:36:58 2007 UTC