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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.39 by root, Sun Aug 28 11:05:50 2005 UTC vs.
Revision 1.86 by root, Sat Oct 28 23:32:29 2006 UTC

…		…
15		15
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	16	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	17	$_[0] > 0 or die "read error: $!";
18	};	18	};
19		19
20	# Event	20	# version 2+ has request and group objects
		21	use IO::AIO 2;
		22
		23	aioreq_pri 4; # give next request a very high priority
		24	my $req = aio_unlink "/tmp/file", sub { };
		25	$req->cancel; # cancel request if still in queue
		26
		27	my $grp = aio_group sub { print "all stats done\n" };
		28	add $grp aio_stat "..." for ...;
		29
		30	# AnyEvent integration
		31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		33
		34	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	35	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	36	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	37	cb => \&IO::AIO::poll_cb);
24		38
25	# Glib/Gtk2	39	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	40	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb; 1 };	41	in => sub { IO::AIO::poll_cb; 1 };
28		42
29	# Tk	43	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	45	readable => \&IO::AIO::poll_cb);
32		46
33	# Danga::Socket	47	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	49	\&IO::AIO::poll_cb);
36		50
37
38	=head1 DESCRIPTION	51	=head1 DESCRIPTION
39		52
40	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
41	operating system supports.	54	operating system supports.
42		55
		56	Asynchronous means that operations that can normally block your program
		57	(e.g. reading from disk) will be done asynchronously: the operation
		58	will still block, but you can do something else in the meantime. This
		59	is extremely useful for programs that need to stay interactive even
		60	when doing heavy I/O (GUI programs, high performance network servers
		61	etc.), but can also be used to easily do operations in parallel that are
		62	normally done sequentially, e.g. stat'ing many files, which is much faster
		63	on a RAID volume or over NFS when you do a number of stat operations
		64	concurrently.
		65
		66	While this works on all types of file descriptors (for example sockets),
		67	using these functions on file descriptors that support nonblocking
		68	operation (again, sockets, pipes etc.) is very inefficient. Use an event
		69	loop for that (such as the L<Event\|Event> module): IO::AIO will naturally
		70	fit into such an event loop itself.
		71
43	Currently, a number of threads are started that execute your read/writes	72	In this version, a number of threads are started that execute your
44	and signal their completion. You don't need thread support in your libc or	73	requests and signal their completion. You don't need thread support
45	perl, and the threads created by this module will not be visible to the	74	in perl, and the threads created by this module will not be visible
46	pthreads library. In the future, this module might make use of the native	75	to perl. In the future, this module might make use of the native aio
47	aio functions available on many operating systems. However, they are often	76	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	77	not well-supported or restricted (GNU/Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	78	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	79	aio_write, so the remaining functionality would have to be implemented
		80	using threads anyway.
51		81
52	Although the module will work with in the presence of other threads, it is	82	Although the module will work with in the presence of other (Perl-)
53	currently not reentrant, so use appropriate locking yourself, always call	83	threads, it is currently not reentrant in any way, so use appropriate
54	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	84	locking yourself, always call C<poll_cb> from within the same thread, or
55	C<aio_> functions) recursively.	85	never call C<poll_cb> (or other C<aio_> functions) recursively.
		86
		87	=head2 EXAMPLE
		88
		89	This is a simple example that uses the Event module and loads
		90	F</etc/passwd> asynchronously:
		91
		92	use Fcntl;
		93	use Event;
		94	use IO::AIO;
		95
		96	# register the IO::AIO callback with Event
		97	Event->io (fd => IO::AIO::poll_fileno,
		98	poll => 'r',
		99	cb => \&IO::AIO::poll_cb);
		100
		101	# queue the request to open /etc/passwd
		102	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		103	my $fh = $_[0]
		104	or die "error while opening: $!";
		105
		106	# stat'ing filehandles is generally non-blocking
		107	my $size = -s $fh;
		108
		109	# queue a request to read the file
		110	my $contents;
		111	aio_read $fh, 0, $size, $contents, 0, sub {
		112	$_[0] == $size
		113	or die "short read: $!";
		114
		115	close $fh;
		116
		117	# file contents now in $contents
		118	print $contents;
		119
		120	# exit event loop and program
		121	Event::unloop;
		122	};
		123	};
		124
		125	# possibly queue up other requests, or open GUI windows,
		126	# check for sockets etc. etc.
		127
		128	# process events as long as there are some:
		129	Event::loop;
		130
		131	=head1 REQUEST ANATOMY AND LIFETIME
		132
		133	Every C<aio_*> function creates a request. which is a C data structure not
		134	directly visible to Perl.
		135
		136	If called in non-void context, every request function returns a Perl
		137	object representing the request. In void context, nothing is returned,
		138	which saves a bit of memory.
		139
		140	The perl object is a fairly standard ref-to-hash object. The hash contents
		141	are not used by IO::AIO so you are free to store anything you like in it.
		142
		143	During their existance, aio requests travel through the following states,
		144	in order:
		145
		146	=over 4
		147
		148	=item ready
		149
		150	Immediately after a request is created it is put into the ready state,
		151	waiting for a thread to execute it.
		152
		153	=item execute
		154
		155	A thread has accepted the request for processing and is currently
		156	executing it (e.g. blocking in read).
		157
		158	=item pending
		159
		160	The request has been executed and is waiting for result processing.
		161
		162	While request submission and execution is fully asynchronous, result
		163	processing is not and relies on the perl interpreter calling C<poll_cb>
		164	(or another function with the same effect).
		165
		166	=item result
		167
		168	The request results are processed synchronously by C<poll_cb>.
		169
		170	The C<poll_cb> function will process all outstanding aio requests by
		171	calling their callbacks, freeing memory associated with them and managing
		172	any groups they are contained in.
		173
		174	=item done
		175
		176	Request has reached the end of its lifetime and holds no resources anymore
		177	(except possibly for the Perl object, but its connection to the actual
		178	aio request is severed and calling its methods will either do nothing or
		179	result in a runtime error).
56		180
57	=cut	181	=cut
58		182
59	package IO::AIO;	183	package IO::AIO;
60		184
61	no warnings;	185	no warnings;
		186	use strict 'vars';
62		187
63	use base 'Exporter';	188	use base 'Exporter';
64		189
65	use Fcntl ();
66
67	BEGIN {	190	BEGIN {
68	$VERSION = 1.6;	191	our $VERSION = '2.1';
69		192
70	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	193	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71	aio_lstat aio_unlink aio_rmdir aio_readdir aio_symlink	194	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72	aio_fsync aio_fdatasync aio_readahead);	195	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
73	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	196	aio_copy aio_group aio_nop aio_mknod);
74	max_outstanding nreqs);	197	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		198	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		199	min_parallel max_parallel max_idle
		200	nreqs nready npending nthreads
		201	max_poll_time max_poll_reqs);
		202
		203	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
75		204
76	require XSLoader;	205	require XSLoader;
77	XSLoader::load IO::AIO, $VERSION;	206	XSLoader::load ("IO::AIO", $VERSION);
78	}	207	}
79		208
80	=head1 FUNCTIONS	209	=head1 FUNCTIONS
81		210
82	=head2 AIO FUNCTIONS	211	=head2 AIO FUNCTIONS
…		…
90	syscall has been executed asynchronously.	219	syscall has been executed asynchronously.
91		220
92	All functions expecting a filehandle keep a copy of the filehandle	221	All functions expecting a filehandle keep a copy of the filehandle
93	internally until the request has finished.	222	internally until the request has finished.
94		223
		224	All requests return objects of type L<IO::AIO::REQ> that allow further
		225	manipulation of those requests while they are in-flight.
		226
95	The pathnames you pass to these routines I<must> be absolute and	227	The pathnames you pass to these routines I<must> be absolute and
96	encoded in byte form. The reason for the former is that at the time the	228	encoded in byte form. The reason for the former is that at the time the
97	request is being executed, the current working directory could have	229	request is being executed, the current working directory could have
98	changed. Alternatively, you can make sure that you never change the	230	changed. Alternatively, you can make sure that you never change the
99	current working directory.	231	current working directory.
…		…
105	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	237	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
106	use something else.	238	use something else.
107		239
108	=over 4	240	=over 4
109		241
		242	=item $prev_pri = aioreq_pri [$pri]
		243
		244	Returns the priority value that would be used for the next request and, if
		245	C<$pri> is given, sets the priority for the next aio request.
		246
		247	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		248	and C<4>, respectively. Requests with higher priority will be serviced
		249	first.
		250
		251	The priority will be reset to C<0> after each call to one of the C<aio_*>
		252	functions.
		253
		254	Example: open a file with low priority, then read something from it with
		255	higher priority so the read request is serviced before other low priority
		256	open requests (potentially spamming the cache):
		257
		258	aioreq_pri -3;
		259	aio_open ..., sub {
		260	return unless $_[0];
		261
		262	aioreq_pri -2;
		263	aio_read $_[0], ..., sub {
		264	...
		265	};
		266	};
		267
		268	=item aioreq_nice $pri_adjust
		269
		270	Similar to C<aioreq_pri>, but subtracts the given value from the current
		271	priority, so effects are cumulative.
		272
110	=item aio_open $pathname, $flags, $mode, $callback	273	=item aio_open $pathname, $flags, $mode, $callback->($fh)
111		274
112	Asynchronously open or create a file and call the callback with a newly	275	Asynchronously open or create a file and call the callback with a newly
113	created filehandle for the file.	276	created filehandle for the file.
114		277
115	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	278	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
132	} else {	295	} else {
133	die "open failed: $!\n";	296	die "open failed: $!\n";
134	}	297	}
135	};	298	};
136		299
137	=item aio_close $fh, $callback	300	=item aio_close $fh, $callback->($status)
138		301
139	Asynchronously close a file and call the callback with the result	302	Asynchronously close a file and call the callback with the result
140	code. I<WARNING:> although accepted, you should not pass in a perl	303	code. I<WARNING:> although accepted, you should not pass in a perl
141	filehandle here, as perl will likely close the file descriptor another	304	filehandle here, as perl will likely close the file descriptor another
142	time when the filehandle is destroyed. Normally, you can safely call perls	305	time when the filehandle is destroyed. Normally, you can safely call perls
143	C<close> or just let filehandles go out of scope.	306	C<close> or just let filehandles go out of scope.
144		307
145	This is supposed to be a bug in the API, so that might change. It's	308	This is supposed to be a bug in the API, so that might change. It's
146	therefore best to avoid this function.	309	therefore best to avoid this function.
147		310
148	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	311	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149		312
150	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	313	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
151		314
152	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	315	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
153	into the scalar given by C<data> and offset C<dataoffset> and calls the	316	into the scalar given by C<data> and offset C<dataoffset> and calls the
154	callback without the actual number of bytes read (or -1 on error, just	317	callback without the actual number of bytes read (or -1 on error, just
155	like the syscall).	318	like the syscall).
…		…
164	aio_read $fh, 7, 15, $buffer, 0, sub {	327	aio_read $fh, 7, 15, $buffer, 0, sub {
165	$_[0] > 0 or die "read error: $!";	328	$_[0] > 0 or die "read error: $!";
166	print "read $_[0] bytes: <$buffer>\n";	329	print "read $_[0] bytes: <$buffer>\n";
167	};	330	};
168		331
169	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback	332	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
170		333
171	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	334	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
172	reading at byte offset C<$in_offset>, and starts writing at the current	335	reading at byte offset C<$in_offset>, and starts writing at the current
173	file offset of C<$out_fh>. Because of that, it is not safe to issue more	336	file offset of C<$out_fh>. Because of that, it is not safe to issue more
174	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	337	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
…		…
187	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	350	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
188	provides the number of bytes written to C<$out_fh>. Only if the result	351	provides the number of bytes written to C<$out_fh>. Only if the result
189	value equals C<$length> one can assume that C<$length> bytes have been	352	value equals C<$length> one can assume that C<$length> bytes have been
190	read.	353	read.
191		354
192	=item aio_readahead $fh,$offset,$length, $callback	355	=item aio_readahead $fh,$offset,$length, $callback->($retval)
193		356
194	C<aio_readahead> populates the page cache with data from a file so that	357	C<aio_readahead> populates the page cache with data from a file so that
195	subsequent reads from that file will not block on disk I/O. The C<$offset>	358	subsequent reads from that file will not block on disk I/O. The C<$offset>
196	argument specifies the starting point from which data is to be read and	359	argument specifies the starting point from which data is to be read and
197	C<$length> specifies the number of bytes to be read. I/O is performed in	360	C<$length> specifies the number of bytes to be read. I/O is performed in
…		…
201	file. The current file offset of the file is left unchanged.	364	file. The current file offset of the file is left unchanged.
202		365
203	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	366	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
204	emulated by simply reading the data, which would have a similar effect.	367	emulated by simply reading the data, which would have a similar effect.
205		368
206	=item aio_stat $fh_or_path, $callback	369	=item aio_stat $fh_or_path, $callback->($status)
207		370
208	=item aio_lstat $fh, $callback	371	=item aio_lstat $fh, $callback->($status)
209		372
210	Works like perl's C<stat> or C<lstat> in void context. The callback will	373	Works like perl's C<stat> or C<lstat> in void context. The callback will
211	be called after the stat and the results will be available using C<stat _>	374	be called after the stat and the results will be available using C<stat _>
212	or C<-s _> etc...	375	or C<-s _> etc...
213		376
…		…
223	aio_stat "/etc/passwd", sub {	386	aio_stat "/etc/passwd", sub {
224	$_[0] and die "stat failed: $!";	387	$_[0] and die "stat failed: $!";
225	print "size is ", -s _, "\n";	388	print "size is ", -s _, "\n";
226	};	389	};
227		390
228	=item aio_unlink $pathname, $callback	391	=item aio_unlink $pathname, $callback->($status)
229		392
230	Asynchronously unlink (delete) a file and call the callback with the	393	Asynchronously unlink (delete) a file and call the callback with the
231	result code.	394	result code.
232		395
		396	=item aio_mknod $path, $mode, $dev, $callback->($status)
		397
		398	[EXPERIMENTAL]
		399
		400	Asynchronously create a device node (or fifo). See mknod(2).
		401
		402	The only (POSIX-) portable way of calling this function is:
		403
		404	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		405
		406	=item aio_link $srcpath, $dstpath, $callback->($status)
		407
		408	Asynchronously create a new link to the existing object at C<$srcpath> at
		409	the path C<$dstpath> and call the callback with the result code.
		410
		411	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		412
		413	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		414	the path C<$dstpath> and call the callback with the result code.
		415
		416	=item aio_rename $srcpath, $dstpath, $callback->($status)
		417
		418	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		419	rename(2) and call the callback with the result code.
		420
233	=item aio_rmdir $pathname, $callback	421	=item aio_rmdir $pathname, $callback->($status)
234		422
235	Asynchronously rmdir (delete) a directory and call the callback with the	423	Asynchronously rmdir (delete) a directory and call the callback with the
236	result code.	424	result code.
237		425
238	=item aio_readdir $pathname $callback	426	=item aio_readdir $pathname, $callback->($entries)
239		427
240	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	428	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
241	directory (i.e. opendir + readdir + closedir). The entries will not be	429	directory (i.e. opendir + readdir + closedir). The entries will not be
242	sorted, and will B<NOT> include the C<.> and C<..> entries.	430	sorted, and will B<NOT> include the C<.> and C<..> entries.
243		431
244	The callback a single argument which is either C<undef> or an array-ref	432	The callback a single argument which is either C<undef> or an array-ref
245	with the filenames.	433	with the filenames.
246		434
		435	=item aio_copy $srcpath, $dstpath, $callback->($status)
		436
		437	Try to copy the I<file> (directories not supported as either source or
		438	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		439	the C<0> (error) or C<-1> ok.
		440
		441	This is a composite request that it creates the destination file with
		442	mode 0200 and copies the contents of the source file into it using
		443	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		444	uid/gid, in that order.
		445
		446	If an error occurs, the partial destination file will be unlinked, if
		447	possible, except when setting atime, mtime, access mode and uid/gid, where
		448	errors are being ignored.
		449
		450	=cut
		451
		452	sub aio_copy($$;$) {
		453	my ($src, $dst, $cb) = @_;
		454
		455	my $pri = aioreq_pri;
		456	my $grp = aio_group $cb;
		457
		458	aioreq_pri $pri;
		459	add $grp aio_open $src, O_RDONLY, 0, sub {
		460	if (my $src_fh = $_[0]) {
		461	my @stat = stat $src_fh;
		462
		463	aioreq_pri $pri;
		464	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		465	if (my $dst_fh = $_[0]) {
		466	aioreq_pri $pri;
		467	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		468	if ($_[0] == $stat[7]) {
		469	$grp->result (0);
		470	close $src_fh;
		471
		472	# those should not normally block. should. should.
		473	utime $stat[8], $stat[9], $dst;
		474	chmod $stat[2] & 07777, $dst_fh;
		475	chown $stat[4], $stat[5], $dst_fh;
		476	close $dst_fh;
		477	} else {
		478	$grp->result (-1);
		479	close $src_fh;
		480	close $dst_fh;
		481
		482	aioreq $pri;
		483	add $grp aio_unlink $dst;
		484	}
		485	};
		486	} else {
		487	$grp->result (-1);
		488	}
		489	},
		490
		491	} else {
		492	$grp->result (-1);
		493	}
		494	};
		495
		496	$grp
		497	}
		498
		499	=item aio_move $srcpath, $dstpath, $callback->($status)
		500
		501	Try to move the I<file> (directories not supported as either source or
		502	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		503	the C<0> (error) or C<-1> ok.
		504
		505	This is a composite request that tries to rename(2) the file first. If
		506	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		507	that is successful, unlinking the C<$srcpath>.
		508
		509	=cut
		510
		511	sub aio_move($$;$) {
		512	my ($src, $dst, $cb) = @_;
		513
		514	my $pri = aioreq_pri;
		515	my $grp = aio_group $cb;
		516
		517	aioreq_pri $pri;
		518	add $grp aio_rename $src, $dst, sub {
		519	if ($_[0] && $! == EXDEV) {
		520	aioreq_pri $pri;
		521	add $grp aio_copy $src, $dst, sub {
		522	$grp->result ($_[0]);
		523
		524	if (!$_[0]) {
		525	aioreq_pri $pri;
		526	add $grp aio_unlink $src;
		527	}
		528	};
		529	} else {
		530	$grp->result ($_[0]);
		531	}
		532	};
		533
		534	$grp
		535	}
		536
		537	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		538
		539	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		540	efficiently separate the entries of directory C<$path> into two sets of
		541	names, directories you can recurse into (directories), and ones you cannot
		542	recurse into (everything else, including symlinks to directories).
		543
		544	C<aio_scandir> is a composite request that creates of many sub requests_
		545	C<$maxreq> specifies the maximum number of outstanding aio requests that
		546	this function generates. If it is C<< <= 0 >>, then a suitable default
		547	will be chosen (currently 4).
		548
		549	On error, the callback is called without arguments, otherwise it receives
		550	two array-refs with path-relative entry names.
		551
		552	Example:
		553
		554	aio_scandir $dir, 0, sub {
		555	my ($dirs, $nondirs) = @_;
		556	print "real directories: @$dirs\n";
		557	print "everything else: @$nondirs\n";
		558	};
		559
		560	Implementation notes.
		561
		562	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		563
		564	After reading the directory, the modification time, size etc. of the
		565	directory before and after the readdir is checked, and if they match (and
		566	isn't the current time), the link count will be used to decide how many
		567	entries are directories (if >= 2). Otherwise, no knowledge of the number
		568	of subdirectories will be assumed.
		569
		570	Then entries will be sorted into likely directories (everything without
		571	a non-initial dot currently) and likely non-directories (everything
		572	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		573	likely directories first. If that succeeds, it assumes that the entry
		574	is a directory or a symlink to directory (which will be checked
		575	seperately). This is often faster than stat'ing the entry itself because
		576	filesystems might detect the type of the entry without reading the inode
		577	data (e.g. ext2fs filetype feature).
		578
		579	If the known number of directories (link count - 2) has been reached, the
		580	rest of the entries is assumed to be non-directories.
		581
		582	This only works with certainty on POSIX (= UNIX) filesystems, which
		583	fortunately are the vast majority of filesystems around.
		584
		585	It will also likely work on non-POSIX filesystems with reduced efficiency
		586	as those tend to return 0 or 1 as link counts, which disables the
		587	directory counting heuristic.
		588
		589	=cut
		590
		591	sub aio_scandir($$$) {
		592	my ($path, $maxreq, $cb) = @_;
		593
		594	my $pri = aioreq_pri;
		595
		596	my $grp = aio_group $cb;
		597
		598	$maxreq = 4 if $maxreq <= 0;
		599
		600	# stat once
		601	aioreq_pri $pri;
		602	add $grp aio_stat $path, sub {
		603	return $grp->result () if $_[0];
		604	my $now = time;
		605	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		606
		607	# read the directory entries
		608	aioreq_pri $pri;
		609	add $grp aio_readdir $path, sub {
		610	my $entries = shift
		611	or return $grp->result ();
		612
		613	# stat the dir another time
		614	aioreq_pri $pri;
		615	add $grp aio_stat $path, sub {
		616	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		617
		618	my $ndirs;
		619
		620	# take the slow route if anything looks fishy
		621	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		622	$ndirs = -1;
		623	} else {
		624	# if nlink == 2, we are finished
		625	# on non-posix-fs's, we rely on nlink < 2
		626	$ndirs = (stat _)[3] - 2
		627	or return $grp->result ([], $entries);
		628	}
		629
		630	# sort into likely dirs and likely nondirs
		631	# dirs == files without ".", short entries first
		632	$entries = [map $_->[0],
		633	sort { $b->[1] cmp $a->[1] }
		634	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		635	@$entries];
		636
		637	my (@dirs, @nondirs);
		638
		639	my $statgrp = add $grp aio_group sub {
		640	$grp->result (\@dirs, \@nondirs);
		641	};
		642
		643	limit $statgrp $maxreq;
		644	feed $statgrp sub {
		645	return unless @$entries;
		646	my $entry = pop @$entries;
		647
		648	aioreq_pri $pri;
		649	add $statgrp aio_stat "$path/$entry/.", sub {
		650	if ($_[0] < 0) {
		651	push @nondirs, $entry;
		652	} else {
		653	# need to check for real directory
		654	aioreq_pri $pri;
		655	add $statgrp aio_lstat "$path/$entry", sub {
		656	if (-d _) {
		657	push @dirs, $entry;
		658
		659	unless (--$ndirs) {
		660	push @nondirs, @$entries;
		661	feed $statgrp;
		662	}
		663	} else {
		664	push @nondirs, $entry;
		665	}
		666	}
		667	}
		668	};
		669	};
		670	};
		671	};
		672	};
		673
		674	$grp
		675	}
		676
247	=item aio_fsync $fh, $callback	677	=item aio_fsync $fh, $callback->($status)
248		678
249	Asynchronously call fsync on the given filehandle and call the callback	679	Asynchronously call fsync on the given filehandle and call the callback
250	with the fsync result code.	680	with the fsync result code.
251		681
252	=item aio_fdatasync $fh, $callback	682	=item aio_fdatasync $fh, $callback->($status)
253		683
254	Asynchronously call fdatasync on the given filehandle and call the	684	Asynchronously call fdatasync on the given filehandle and call the
255	callback with the fdatasync result code.	685	callback with the fdatasync result code.
256		686
257	If this call isn't available because your OS lacks it or it couldn't be	687	If this call isn't available because your OS lacks it or it couldn't be
258	detected, it will be emulated by calling C<fsync> instead.	688	detected, it will be emulated by calling C<fsync> instead.
259		689
		690	=item aio_group $callback->(...)
		691
		692	This is a very special aio request: Instead of doing something, it is a
		693	container for other aio requests, which is useful if you want to bundle
		694	many requests into a single, composite, request with a definite callback
		695	and the ability to cancel the whole request with its subrequests.
		696
		697	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		698	for more info.
		699
		700	Example:
		701
		702	my $grp = aio_group sub {
		703	print "all stats done\n";
		704	};
		705
		706	add $grp
		707	(aio_stat ...),
		708	(aio_stat ...),
		709	...;
		710
		711	=item aio_nop $callback->()
		712
		713	This is a special request - it does nothing in itself and is only used for
		714	side effects, such as when you want to add a dummy request to a group so
		715	that finishing the requests in the group depends on executing the given
		716	code.
		717
		718	While this request does nothing, it still goes through the execution
		719	phase and still requires a worker thread. Thus, the callback will not
		720	be executed immediately but only after other requests in the queue have
		721	entered their execution phase. This can be used to measure request
		722	latency.
		723
		724	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		725
		726	Mainly used for debugging and benchmarking, this aio request puts one of
		727	the request workers to sleep for the given time.
		728
		729	While it is theoretically handy to have simple I/O scheduling requests
		730	like sleep and file handle readable/writable, the overhead this creates is
		731	immense (it blocks a thread for a long time) so do not use this function
		732	except to put your application under artificial I/O pressure.
		733
260	=back	734	=back
261		735
		736	=head2 IO::AIO::REQ CLASS
		737
		738	All non-aggregate C<aio_*> functions return an object of this class when
		739	called in non-void context.
		740
		741	=over 4
		742
		743	=item cancel $req
		744
		745	Cancels the request, if possible. Has the effect of skipping execution
		746	when entering the B<execute> state and skipping calling the callback when
		747	entering the the B<result> state, but will leave the request otherwise
		748	untouched. That means that requests that currently execute will not be
		749	stopped and resources held by the request will not be freed prematurely.
		750
		751	=item cb $req $callback->(...)
		752
		753	Replace (or simply set) the callback registered to the request.
		754
		755	=back
		756
		757	=head2 IO::AIO::GRP CLASS
		758
		759	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		760	objects of this class, too.
		761
		762	A IO::AIO::GRP object is a special request that can contain multiple other
		763	aio requests.
		764
		765	You create one by calling the C<aio_group> constructing function with a
		766	callback that will be called when all contained requests have entered the
		767	C<done> state:
		768
		769	my $grp = aio_group sub {
		770	print "all requests are done\n";
		771	};
		772
		773	You add requests by calling the C<add> method with one or more
		774	C<IO::AIO::REQ> objects:
		775
		776	$grp->add (aio_unlink "...");
		777
		778	add $grp aio_stat "...", sub {
		779	$_[0] or return $grp->result ("error");
		780
		781	# add another request dynamically, if first succeeded
		782	add $grp aio_open "...", sub {
		783	$grp->result ("ok");
		784	};
		785	};
		786
		787	This makes it very easy to create composite requests (see the source of
		788	C<aio_move> for an application) that work and feel like simple requests.
		789
		790	=over 4
		791
		792	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		793	C<IO::AIO::poll_cb>, just like any other request.
		794
		795	=item * They can be canceled like any other request. Canceling will cancel not
		796	only the request itself, but also all requests it contains.
		797
		798	=item * They can also can also be added to other IO::AIO::GRP objects.
		799
		800	=item * You must not add requests to a group from within the group callback (or
		801	any later time).
		802
		803	=back
		804
		805	Their lifetime, simplified, looks like this: when they are empty, they
		806	will finish very quickly. If they contain only requests that are in the
		807	C<done> state, they will also finish. Otherwise they will continue to
		808	exist.
		809
		810	That means after creating a group you have some time to add requests. And
		811	in the callbacks of those requests, you can add further requests to the
		812	group. And only when all those requests have finished will the the group
		813	itself finish.
		814
		815	=over 4
		816
		817	=item add $grp ...
		818
		819	=item $grp->add (...)
		820
		821	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		822	be added, including other groups, as long as you do not create circular
		823	dependencies.
		824
		825	Returns all its arguments.
		826
		827	=item $grp->cancel_subs
		828
		829	Cancel all subrequests and clears any feeder, but not the group request
		830	itself. Useful when you queued a lot of events but got a result early.
		831
		832	=item $grp->result (...)
		833
		834	Set the result value(s) that will be passed to the group callback when all
		835	subrequests have finished and set thre groups errno to the current value
		836	of errno (just like calling C<errno> without an error number). By default,
		837	no argument will be passed and errno is zero.
		838
		839	=item $grp->errno ([$errno])
		840
		841	Sets the group errno value to C<$errno>, or the current value of errno
		842	when the argument is missing.
		843
		844	Every aio request has an associated errno value that is restored when
		845	the callback is invoked. This method lets you change this value from its
		846	default (0).
		847
		848	Calling C<result> will also set errno, so make sure you either set C<$!>
		849	before the call to C<result>, or call c<errno> after it.
		850
		851	=item feed $grp $callback->($grp)
		852
		853	Sets a feeder/generator on this group: every group can have an attached
		854	generator that generates requests if idle. The idea behind this is that,
		855	although you could just queue as many requests as you want in a group,
		856	this might starve other requests for a potentially long time. For
		857	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		858	requests, delaying any later requests for a long time.
		859
		860	To avoid this, and allow incremental generation of requests, you can
		861	instead a group and set a feeder on it that generates those requests. The
		862	feed callback will be called whenever there are few enough (see C<limit>,
		863	below) requests active in the group itself and is expected to queue more
		864	requests.
		865
		866	The feed callback can queue as many requests as it likes (i.e. C<add> does
		867	not impose any limits).
		868
		869	If the feed does not queue more requests when called, it will be
		870	automatically removed from the group.
		871
		872	If the feed limit is C<0>, it will be set to C<2> automatically.
		873
		874	Example:
		875
		876	# stat all files in @files, but only ever use four aio requests concurrently:
		877
		878	my $grp = aio_group sub { print "finished\n" };
		879	limit $grp 4;
		880	feed $grp sub {
		881	my $file = pop @files
		882	or return;
		883
		884	add $grp aio_stat $file, sub { ... };
		885	};
		886
		887	=item limit $grp $num
		888
		889	Sets the feeder limit for the group: The feeder will be called whenever
		890	the group contains less than this many requests.
		891
		892	Setting the limit to C<0> will pause the feeding process.
		893
		894	=back
		895
262	=head2 SUPPORT FUNCTIONS	896	=head2 SUPPORT FUNCTIONS
		897
		898	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
263		899
264	=over 4	900	=over 4
265		901
266	=item $fileno = IO::AIO::poll_fileno	902	=item $fileno = IO::AIO::poll_fileno
267		903
…		…
272		908
273	See C<poll_cb> for an example.	909	See C<poll_cb> for an example.
274		910
275	=item IO::AIO::poll_cb	911	=item IO::AIO::poll_cb
276		912
277	Process all outstanding events on the result pipe. You have to call this	913	Process some outstanding events on the result pipe. You have to call this
278	regularly. Returns the number of events processed. Returns immediately	914	regularly. Returns the number of events processed. Returns immediately
279	when no events are outstanding.	915	when no events are outstanding. The amount of events processed depends on
		916	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		917
		918	If not all requests were processed for whatever reason, the filehandle
		919	will still be ready when C<poll_cb> returns.
280		920
281	Example: Install an Event watcher that automatically calls	921	Example: Install an Event watcher that automatically calls
282	IO::AIO::poll_cb with high priority:	922	IO::AIO::poll_cb with high priority:
283		923
284	Event->io (fd => IO::AIO::poll_fileno,	924	Event->io (fd => IO::AIO::poll_fileno,
285	poll => 'r', async => 1,	925	poll => 'r', async => 1,
286	cb => \&IO::AIO::poll_cb);	926	cb => \&IO::AIO::poll_cb);
287		927
		928	=item IO::AIO::max_poll_reqs $nreqs
		929
		930	=item IO::AIO::max_poll_time $seconds
		931
		932	These set the maximum number of requests (default C<0>, meaning infinity)
		933	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		934	the maximum amount of time (default C<0>, meaning infinity) spent in
		935	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		936	of time C<poll_cb> is allowed to use).
		937
		938	Setting these is useful if you want to ensure some level of
		939	interactiveness when perl is not fast enough to process all requests in
		940	time.
		941
		942	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		943
		944	Example: Install an Event watcher that automatically calls
		945	IO::AIO::poll_some with low priority, to ensure that other parts of the
		946	program get the CPU sometimes even under high AIO load.
		947
		948	# try not to spend much more than 0.1s in poll_cb
		949	IO::AIO::max_poll_time 0.1;
		950
		951	# use a low priority so other tasks have priority
		952	Event->io (fd => IO::AIO::poll_fileno,
		953	poll => 'r', nice => 1,
		954	cb => &IO::AIO::poll_cb);
		955
288	=item IO::AIO::poll_wait	956	=item IO::AIO::poll_wait
289		957
290	Wait till the result filehandle becomes ready for reading (simply does a	958	Wait till the result filehandle becomes ready for reading (simply does a
291	C<select> on the filehandle. This is useful if you want to synchronously wait	959	C<select> on the filehandle. This is useful if you want to synchronously
292	for some requests to finish).	960	wait for some requests to finish).
293		961
294	See C<nreqs> for an example.	962	See C<nreqs> for an example.
295		963
		964	=item IO::AIO::poll
		965
		966	Waits until some requests have been handled.
		967
		968	Strictly equivalent to:
		969
		970	IO::AIO::poll_wait, IO::AIO::poll_cb
		971	if IO::AIO::nreqs;
		972
296	=item IO::AIO::nreqs	973	=item IO::AIO::flush
297		974
298	Returns the number of requests currently outstanding (i.e. for which their	975	Wait till all outstanding AIO requests have been handled.
299	callback has not been invoked yet).
300		976
301	Example: wait till there are no outstanding requests anymore:	977	Strictly equivalent to:
302		978
303	IO::AIO::poll_wait, IO::AIO::poll_cb	979	IO::AIO::poll_wait, IO::AIO::poll_cb
304	while IO::AIO::nreqs;	980	while IO::AIO::nreqs;
305		981
306	=item IO::AIO::flush	982	=head3 CONTROLLING THE NUMBER OF THREADS
307
308	Wait till all outstanding AIO requests have been handled.
309
310	Strictly equivalent to:
311
312	IO::AIO::poll_wait, IO::AIO::poll_cb
313	while IO::AIO::nreqs;
314
315	=item IO::AIO::poll
316
317	Waits until some requests have been handled.
318
319	Strictly equivalent to:
320
321	IO::AIO::poll_wait, IO::AIO::poll_cb
322	if IO::AIO::nreqs;
323		983
324	=item IO::AIO::min_parallel $nthreads	984	=item IO::AIO::min_parallel $nthreads
325		985
326	Set the minimum number of AIO threads to C<$nthreads>. The current default	986	Set the minimum number of AIO threads to C<$nthreads>. The current
327	is C<4>, which means four asynchronous operations can be done at one time	987	default is C<8>, which means eight asynchronous operations can execute
328	(the number of outstanding operations, however, is unlimited).	988	concurrently at any one time (the number of outstanding requests,
		989	however, is unlimited).
329		990
330	IO::AIO starts threads only on demand, when an AIO request is queued and	991	IO::AIO starts threads only on demand, when an AIO request is queued and
331	no free thread exists.	992	no free thread exists. Please note that queueing up a hundred requests can
		993	create demand for a hundred threads, even if it turns out that everything
		994	is in the cache and could have been processed faster by a single thread.
332		995
333	It is recommended to keep the number of threads low, as some Linux	996	It is recommended to keep the number of threads relatively low, as some
334	kernel versions will scale negatively with the number of threads (higher	997	Linux kernel versions will scale negatively with the number of threads
335	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	998	(higher parallelity => MUCH higher latency). With current Linux 2.6
336	threads should be fine.	999	versions, 4-32 threads should be fine.
337		1000
338	Under most circumstances you don't need to call this function, as the	1001	Under most circumstances you don't need to call this function, as the
339	module selects a default that is suitable for low to moderate load.	1002	module selects a default that is suitable for low to moderate load.
340		1003
341	=item IO::AIO::max_parallel $nthreads	1004	=item IO::AIO::max_parallel $nthreads
…		…
350	This module automatically runs C<max_parallel 0> at program end, to ensure	1013	This module automatically runs C<max_parallel 0> at program end, to ensure
351	that all threads are killed and that there are no outstanding requests.	1014	that all threads are killed and that there are no outstanding requests.
352		1015
353	Under normal circumstances you don't need to call this function.	1016	Under normal circumstances you don't need to call this function.
354		1017
		1018	=item IO::AIO::max_idle $nthreads
		1019
		1020	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1021	threads that did not get a request to process within 10 seconds). That
		1022	means if a thread becomes idle while C<$nthreads> other threads are also
		1023	idle, it will free its resources and exit.
		1024
		1025	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1026	to allow for extremely high load situations, but want to free resources
		1027	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1028
		1029	The default is probably ok in most situations, especially if thread
		1030	creation is fast. If thread creation is very slow on your system you might
		1031	want to use larger values.
		1032
355	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1033	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1034
		1035	This is a very bad function to use in interactive programs because it
		1036	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1037	use an C<aio_group> together with a feed callback.
356		1038
357	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1039	Sets the maximum number of outstanding requests to C<$nreqs>. If you
358	try to queue up more than this number of requests, the caller will block until	1040	to queue up more than this number of requests, the next call to the
359	some requests have been handled.	1041	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1042	function will block until the limit is no longer exceeded.
360		1043
361	The default is very large, so normally there is no practical limit. If you	1044	The default value is very large, so there is no practical limit on the
362	queue up many requests in a loop it often improves speed if you set	1045	number of outstanding requests.
363	this to a relatively low number, such as C<100>.
364		1046
365	Under normal circumstances you don't need to call this function.	1047	You can still queue as many requests as you want. Therefore,
		1048	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1049	as a stop gap to shield against fatal memory overflow (with large values).
		1050
		1051	=head3 STATISTICAL INFORMATION
		1052
		1053	=item IO::AIO::nreqs
		1054
		1055	Returns the number of requests currently in the ready, execute or pending
		1056	states (i.e. for which their callback has not been invoked yet).
		1057
		1058	Example: wait till there are no outstanding requests anymore:
		1059
		1060	IO::AIO::poll_wait, IO::AIO::poll_cb
		1061	while IO::AIO::nreqs;
		1062
		1063	=item IO::AIO::nready
		1064
		1065	Returns the number of requests currently in the ready state (not yet
		1066	executed).
		1067
		1068	=item IO::AIO::npending
		1069
		1070	Returns the number of requests currently in the pending state (executed,
		1071	but not yet processed by poll_cb).
366		1072
367	=back	1073	=back
368		1074
369	=cut	1075	=cut
370		1076
…		…
382	or return undef;	1088	or return undef;
383		1089
384	*$sym	1090	*$sym
385	}	1091	}
386		1092
387	min_parallel 4;	1093	min_parallel 8;
388		1094
389	END {	1095	END {
390	max_parallel 0;	1096	min_parallel 1;
391	}	1097	flush;
		1098	};
392		1099
393	1;	1100	1;
394		1101
395	=head2 FORK BEHAVIOUR	1102	=head2 FORK BEHAVIOUR
		1103
		1104	This module should do "the right thing" when the process using it forks:
396		1105
397	Before the fork, IO::AIO enters a quiescent state where no requests	1106	Before the fork, IO::AIO enters a quiescent state where no requests
398	can be added in other threads and no results will be processed. After	1107	can be added in other threads and no results will be processed. After
399	the fork the parent simply leaves the quiescent state and continues	1108	the fork the parent simply leaves the quiescent state and continues
400	request/result processing, while the child clears the request/result	1109	request/result processing, while the child frees the request/result queue
401	queue (so the requests started before the fork will only be handled in	1110	(so that the requests started before the fork will only be handled in the
402	the parent). Threats will be started on demand until the limit ste in the	1111	parent). Threads will be started on demand until the limit set in the
403	parent process has been reached again.	1112	parent process has been reached again.
404		1113
		1114	In short: the parent will, after a short pause, continue as if fork had
		1115	not been called, while the child will act as if IO::AIO has not been used
		1116	yet.
		1117
		1118	=head2 MEMORY USAGE
		1119
		1120	Per-request usage:
		1121
		1122	Each aio request uses - depending on your architecture - around 100-200
		1123	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1124	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1125	scalars and other data passed into aio requests will also be locked and
		1126	will consume memory till the request has entered the done state.
		1127
		1128	This is now awfully much, so queuing lots of requests is not usually a
		1129	problem.
		1130
		1131	Per-thread usage:
		1132
		1133	In the execution phase, some aio requests require more memory for
		1134	temporary buffers, and each thread requires a stack and other data
		1135	structures (usually around 16k-128k, depending on the OS).
		1136
		1137	=head1 KNOWN BUGS
		1138
		1139	Known bugs will be fixed in the next release.
		1140
405	=head1 SEE ALSO	1141	=head1 SEE ALSO
406		1142
407	L<Coro>, L<Linux::AIO>.	1143	L<Coro::AIO>.
408		1144
409	=head1 AUTHOR	1145	=head1 AUTHOR
410		1146
411	Marc Lehmann <schmorp@schmorp.de>	1147	Marc Lehmann <schmorp@schmorp.de>
412	http://home.schmorp.de/	1148	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.39 by root, Sun Aug 28 11:05:50 2005 UTC vs. Revision 1.86 by root, Sat Oct 28 23:32:29 2006 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.39 by root, Sun Aug 28 11:05:50 2005 UTC vs.
Revision 1.86 by root, Sat Oct 28 23:32:29 2006 UTC