[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 1.75 by root, Tue Oct 24 20:10:26 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
43	Currently, a number of threads are started that execute your read/writes	56	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	57	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	58	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	59	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	60	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	61	not well-supported or restricted (Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	62	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	63	aio_write, so the remaining functionality would have to be implemented
		64	using threads anyway.
51		65
52	Although the module will work with in the presence of other threads, it is	66	Although the module will work with in the presence of other (Perl-)
53	currently not reentrant, so use appropriate locking yourself, always call	67	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	68	locking yourself, always call C<poll_cb> from within the same thread, or
55	C<aio_> functions) recursively.	69	never call C<poll_cb> (or other C<aio_> functions) recursively.
		70
		71	=head1 REQUEST ANATOMY AND LIFETIME
		72
		73	Every C<aio_*> function creates a request. which is a C data structure not
		74	directly visible to Perl.
		75
		76	If called in non-void context, every request function returns a Perl
		77	object representing the request. In void context, nothing is returned,
		78	which saves a bit of memory.
		79
		80	The perl object is a fairly standard ref-to-hash object. The hash contents
		81	are not used by IO::AIO so you are free to store anything you like in it.
		82
		83	During their existance, aio requests travel through the following states,
		84	in order:
		85
		86	=over 4
		87
		88	=item ready
		89
		90	Immediately after a request is created it is put into the ready state,
		91	waiting for a thread to execute it.
		92
		93	=item execute
		94
		95	A thread has accepted the request for processing and is currently
		96	executing it (e.g. blocking in read).
		97
		98	=item pending
		99
		100	The request has been executed and is waiting for result processing.
		101
		102	While request submission and execution is fully asynchronous, result
		103	processing is not and relies on the perl interpreter calling C<poll_cb>
		104	(or another function with the same effect).
		105
		106	=item result
		107
		108	The request results are processed synchronously by C<poll_cb>.
		109
		110	The C<poll_cb> function will process all outstanding aio requests by
		111	calling their callbacks, freeing memory associated with them and managing
		112	any groups they are contained in.
		113
		114	=item done
		115
		116	Request has reached the end of its lifetime and holds no resources anymore
		117	(except possibly for the Perl object, but its connection to the actual
		118	aio request is severed and calling its methods will either do nothing or
		119	result in a runtime error).
56		120
57	=cut	121	=cut
58		122
59	package IO::AIO;	123	package IO::AIO;
60		124
61	no warnings;	125	no warnings;
		126	use strict 'vars';
62		127
63	use base 'Exporter';	128	use base 'Exporter';
64		129
65	use Fcntl ();
66
67	BEGIN {	130	BEGIN {
68	$VERSION = 1.6;	131	our $VERSION = '2.0';
69		132
70	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	133	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	134	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72	aio_fsync aio_fdatasync aio_readahead);	135	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
73	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	136	aio_group aio_nop);
74	max_outstanding nreqs);	137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		139	min_parallel max_parallel max_outstanding nreqs);
		140
		141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
75		142
76	require XSLoader;	143	require XSLoader;
77	XSLoader::load IO::AIO, $VERSION;	144	XSLoader::load ("IO::AIO", $VERSION);
78	}	145	}
79		146
80	=head1 FUNCTIONS	147	=head1 FUNCTIONS
81		148
82	=head2 AIO FUNCTIONS	149	=head2 AIO FUNCTIONS
…		…
90	syscall has been executed asynchronously.	157	syscall has been executed asynchronously.
91		158
92	All functions expecting a filehandle keep a copy of the filehandle	159	All functions expecting a filehandle keep a copy of the filehandle
93	internally until the request has finished.	160	internally until the request has finished.
94		161
		162	All requests return objects of type L<IO::AIO::REQ> that allow further
		163	manipulation of those requests while they are in-flight.
		164
95	The pathnames you pass to these routines I<must> be absolute and	165	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	166	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	167	request is being executed, the current working directory could have
98	changed. Alternatively, you can make sure that you never change the	168	changed. Alternatively, you can make sure that you never change the
99	current working directory.	169	current working directory.
…		…
105	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	175	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
106	use something else.	176	use something else.
107		177
108	=over 4	178	=over 4
109		179
		180	=item aioreq_pri $pri
		181
		182	Sets the priority for the next aio request. The default priority
		183	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,
		184	respectively. Requests with higher priority will be serviced first.
		185
		186	The priority will be reset to C<0> after each call to one of the C<aio_>
		187	functions.
		188
		189	Example: open a file with low priority, then read something from it with
		190	higher priority so the read request is serviced before other low priority
		191	open requests (potentially spamming the cache):
		192
		193	aioreq_pri -3;
		194	aio_open ..., sub {
		195	return unless $_[0];
		196
		197	aioreq_pri -2;
		198	aio_read $_[0], ..., sub {
		199	...
		200	};
		201	};
		202
		203	=item aioreq_nice $pri_adjust
		204
		205	Similar to C<aioreq_pri>, but subtracts the given value from the current
		206	priority, so effects are cumulative.
		207
110	=item aio_open $pathname, $flags, $mode, $callback	208	=item aio_open $pathname, $flags, $mode, $callback->($fh)
111		209
112	Asynchronously open or create a file and call the callback with a newly	210	Asynchronously open or create a file and call the callback with a newly
113	created filehandle for the file.	211	created filehandle for the file.
114		212
115	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	213	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
132	} else {	230	} else {
133	die "open failed: $!\n";	231	die "open failed: $!\n";
134	}	232	}
135	};	233	};
136		234
137	=item aio_close $fh, $callback	235	=item aio_close $fh, $callback->($status)
138		236
139	Asynchronously close a file and call the callback with the result	237	Asynchronously close a file and call the callback with the result
140	code. I<WARNING:> although accepted, you should not pass in a perl	238	code. I<WARNING:> although accepted, you should not pass in a perl
141	filehandle here, as perl will likely close the file descriptor another	239	filehandle here, as perl will likely close the file descriptor another
142	time when the filehandle is destroyed. Normally, you can safely call perls	240	time when the filehandle is destroyed. Normally, you can safely call perls
143	C<close> or just let filehandles go out of scope.	241	C<close> or just let filehandles go out of scope.
144		242
145	This is supposed to be a bug in the API, so that might change. It's	243	This is supposed to be a bug in the API, so that might change. It's
146	therefore best to avoid this function.	244	therefore best to avoid this function.
147		245
148	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	246	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149		247
150	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	248	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
151		249
152	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	250	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	251	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	252	callback without the actual number of bytes read (or -1 on error, just
155	like the syscall).	253	like the syscall).
…		…
164	aio_read $fh, 7, 15, $buffer, 0, sub {	262	aio_read $fh, 7, 15, $buffer, 0, sub {
165	$_[0] > 0 or die "read error: $!";	263	$_[0] > 0 or die "read error: $!";
166	print "read $_[0] bytes: <$buffer>\n";	264	print "read $_[0] bytes: <$buffer>\n";
167	};	265	};
168		266
		267	=item aio_move $srcpath, $dstpath, $callback->($status)
		268
		269	Try to move the I<file> (directories not supported as either source or
		270	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		271	the C<0> (error) or C<-1> ok.
		272
		273	This is a composite request that tries to rename(2) the file first. If
		274	rename files with C<EXDEV>, it creates the destination file with mode 0200
		275	and copies the contents of the source file into it using C<aio_sendfile>,
		276	followed by restoring atime, mtime, access mode and uid/gid, in that
		277	order, and unlinking the C<$srcpath>.
		278
		279	If an error occurs, the partial destination file will be unlinked, if
		280	possible, except when setting atime, mtime, access mode and uid/gid, where
		281	errors are being ignored.
		282
		283	=cut
		284
		285	sub aio_move($$$) {
		286	my ($src, $dst, $cb) = @_;
		287
		288	my $grp = aio_group $cb;
		289
		290	add $grp aio_rename $src, $dst, sub {
		291	if ($_[0] && $! == EXDEV) {
		292	add $grp aio_open $src, O_RDONLY, 0, sub {
		293	if (my $src_fh = $_[0]) {
		294	my @stat = stat $src_fh;
		295
		296	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		297	if (my $dst_fh = $_[0]) {
		298	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		299	close $src_fh;
		300
		301	if ($_[0] == $stat[7]) {
		302	utime $stat[8], $stat[9], $dst;
		303	chmod $stat[2] & 07777, $dst_fh;
		304	chown $stat[4], $stat[5], $dst_fh;
		305	close $dst_fh;
		306
		307	add $grp aio_unlink $src, sub {
		308	$grp->result ($_[0]);
		309	};
		310	} else {
		311	my $errno = $!;
		312	add $grp aio_unlink $dst, sub {
		313	$! = $errno;
		314	$grp->result (-1);
		315	};
		316	}
		317	};
		318	} else {
		319	$grp->result (-1);
		320	}
		321	},
		322
		323	} else {
		324	$grp->result (-1);
		325	}
		326	};
		327	} else {
		328	$grp->result ($_[0]);
		329	}
		330	};
		331
		332	$grp
		333	}
		334
169	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback	335	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
170		336
171	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	337	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	338	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	339	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	340	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	353	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	354	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	355	value equals C<$length> one can assume that C<$length> bytes have been
190	read.	356	read.
191		357
192	=item aio_readahead $fh,$offset,$length, $callback	358	=item aio_readahead $fh,$offset,$length, $callback->($retval)
193		359
194	C<aio_readahead> populates the page cache with data from a file so that	360	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>	361	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	362	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	363	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.	367	file. The current file offset of the file is left unchanged.
202		368
203	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	369	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.	370	emulated by simply reading the data, which would have a similar effect.
205		371
206	=item aio_stat $fh_or_path, $callback	372	=item aio_stat $fh_or_path, $callback->($status)
207		373
208	=item aio_lstat $fh, $callback	374	=item aio_lstat $fh, $callback->($status)
209		375
210	Works like perl's C<stat> or C<lstat> in void context. The callback will	376	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 _>	377	be called after the stat and the results will be available using C<stat _>
212	or C<-s _> etc...	378	or C<-s _> etc...
213		379
…		…
223	aio_stat "/etc/passwd", sub {	389	aio_stat "/etc/passwd", sub {
224	$_[0] and die "stat failed: $!";	390	$_[0] and die "stat failed: $!";
225	print "size is ", -s _, "\n";	391	print "size is ", -s _, "\n";
226	};	392	};
227		393
228	=item aio_unlink $pathname, $callback	394	=item aio_unlink $pathname, $callback->($status)
229		395
230	Asynchronously unlink (delete) a file and call the callback with the	396	Asynchronously unlink (delete) a file and call the callback with the
231	result code.	397	result code.
232		398
		399	=item aio_link $srcpath, $dstpath, $callback->($status)
		400
		401	Asynchronously create a new link to the existing object at C<$srcpath> at
		402	the path C<$dstpath> and call the callback with the result code.
		403
		404	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		405
		406	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		407	the path C<$dstpath> and call the callback with the result code.
		408
		409	=item aio_rename $srcpath, $dstpath, $callback->($status)
		410
		411	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		412	rename(2) and call the callback with the result code.
		413
233	=item aio_rmdir $pathname, $callback	414	=item aio_rmdir $pathname, $callback->($status)
234		415
235	Asynchronously rmdir (delete) a directory and call the callback with the	416	Asynchronously rmdir (delete) a directory and call the callback with the
236	result code.	417	result code.
237		418
238	=item aio_readdir $pathname $callback	419	=item aio_readdir $pathname, $callback->($entries)
239		420
240	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	421	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	422	directory (i.e. opendir + readdir + closedir). The entries will not be
242	sorted, and will B<NOT> include the C<.> and C<..> entries.	423	sorted, and will B<NOT> include the C<.> and C<..> entries.
243		424
244	The callback a single argument which is either C<undef> or an array-ref	425	The callback a single argument which is either C<undef> or an array-ref
245	with the filenames.	426	with the filenames.
246		427
		428	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		429
		430	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		431	separate the entries of directory C<$path> into two sets of names, ones
		432	you can recurse into (directories or links to them), and ones you cannot
		433	recurse into (everything else).
		434
		435	C<aio_scandir> is a composite request that creates of many sub requests_
		436	C<$maxreq> specifies the maximum number of outstanding aio requests that
		437	this function generates. If it is C<< <= 0 >>, then a suitable default
		438	will be chosen (currently 6).
		439
		440	On error, the callback is called without arguments, otherwise it receives
		441	two array-refs with path-relative entry names.
		442
		443	Example:
		444
		445	aio_scandir $dir, 0, sub {
		446	my ($dirs, $nondirs) = @_;
		447	print "real directories: @$dirs\n";
		448	print "everything else: @$nondirs\n";
		449	};
		450
		451	Implementation notes.
		452
		453	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		454
		455	After reading the directory, the modification time, size etc. of the
		456	directory before and after the readdir is checked, and if they match (and
		457	isn't the current time), the link count will be used to decide how many
		458	entries are directories (if >= 2). Otherwise, no knowledge of the number
		459	of subdirectories will be assumed.
		460
		461	Then entries will be sorted into likely directories (everything without
		462	a non-initial dot currently) and likely non-directories (everything
		463	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		464	likely directories first. If that succeeds, it assumes that the entry
		465	is a directory or a symlink to directory (which will be checked
		466	seperately). This is often faster than stat'ing the entry itself because
		467	filesystems might detect the type of the entry without reading the inode
		468	data (e.g. ext2fs filetype feature).
		469
		470	If the known number of directories (link count - 2) has been reached, the
		471	rest of the entries is assumed to be non-directories.
		472
		473	This only works with certainty on POSIX (= UNIX) filesystems, which
		474	fortunately are the vast majority of filesystems around.
		475
		476	It will also likely work on non-POSIX filesystems with reduced efficiency
		477	as those tend to return 0 or 1 as link counts, which disables the
		478	directory counting heuristic.
		479
		480	=cut
		481
		482	sub aio_scandir($$$) {
		483	my ($path, $maxreq, $cb) = @_;
		484
		485	my $grp = aio_group $cb;
		486
		487	$maxreq = 6 if $maxreq <= 0;
		488
		489	# stat once
		490	add $grp aio_stat $path, sub {
		491	return $grp->result () if $_[0];
		492	my $now = time;
		493	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		494
		495	# read the directory entries
		496	add $grp aio_readdir $path, sub {
		497	my $entries = shift
		498	or return $grp->result ();
		499
		500	# stat the dir another time
		501	add $grp aio_stat $path, sub {
		502	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		503
		504	my $ndirs;
		505
		506	# take the slow route if anything looks fishy
		507	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		508	$ndirs = -1;
		509	} else {
		510	# if nlink == 2, we are finished
		511	# on non-posix-fs's, we rely on nlink < 2
		512	$ndirs = (stat _)[3] - 2
		513	or return $grp->result ([], $entries);
		514	}
		515
		516	# sort into likely dirs and likely nondirs
		517	# dirs == files without ".", short entries first
		518	$entries = [map $_->[0],
		519	sort { $b->[1] cmp $a->[1] }
		520	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		521	@$entries];
		522
		523	my (@dirs, @nondirs);
		524
		525	my $statgrp = add $grp aio_group sub {
		526	$grp->result (\@dirs, \@nondirs);
		527	};
		528
		529	limit $statgrp $maxreq;
		530	feed $statgrp sub {
		531	return unless @$entries;
		532	my $entry = pop @$entries;
		533
		534	add $statgrp aio_stat "$path/$entry/.", sub {
		535	if ($_[0] < 0) {
		536	push @nondirs, $entry;
		537	} else {
		538	# need to check for real directory
		539	add $statgrp aio_lstat "$path/$entry", sub {
		540	if (-d _) {
		541	push @dirs, $entry;
		542
		543	unless (--$ndirs) {
		544	push @nondirs, @$entries;
		545	feed $statgrp;
		546	}
		547	} else {
		548	push @nondirs, $entry;
		549	}
		550	}
		551	}
		552	};
		553	};
		554	};
		555	};
		556	};
		557
		558	$grp
		559	}
		560
247	=item aio_fsync $fh, $callback	561	=item aio_fsync $fh, $callback->($status)
248		562
249	Asynchronously call fsync on the given filehandle and call the callback	563	Asynchronously call fsync on the given filehandle and call the callback
250	with the fsync result code.	564	with the fsync result code.
251		565
252	=item aio_fdatasync $fh, $callback	566	=item aio_fdatasync $fh, $callback->($status)
253		567
254	Asynchronously call fdatasync on the given filehandle and call the	568	Asynchronously call fdatasync on the given filehandle and call the
255	callback with the fdatasync result code.	569	callback with the fdatasync result code.
256		570
257	If this call isn't available because your OS lacks it or it couldn't be	571	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.	572	detected, it will be emulated by calling C<fsync> instead.
		573
		574	=item aio_group $callback->(...)
		575
		576	This is a very special aio request: Instead of doing something, it is a
		577	container for other aio requests, which is useful if you want to bundle
		578	many requests into a single, composite, request with a definite callback
		579	and the ability to cancel the whole request with its subrequests.
		580
		581	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		582	for more info.
		583
		584	Example:
		585
		586	my $grp = aio_group sub {
		587	print "all stats done\n";
		588	};
		589
		590	add $grp
		591	(aio_stat ...),
		592	(aio_stat ...),
		593	...;
		594
		595	=item aio_nop $callback->()
		596
		597	This is a special request - it does nothing in itself and is only used for
		598	side effects, such as when you want to add a dummy request to a group so
		599	that finishing the requests in the group depends on executing the given
		600	code.
		601
		602	While this request does nothing, it still goes through the execution
		603	phase and still requires a worker thread. Thus, the callback will not
		604	be executed immediately but only after other requests in the queue have
		605	entered their execution phase. This can be used to measure request
		606	latency.
		607
		608	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		609
		610	Mainly used for debugging and benchmarking, this aio request puts one of
		611	the request workers to sleep for the given time.
		612
		613	While it is theoretically handy to have simple I/O scheduling requests
		614	like sleep and file handle readable/writable, the overhead this creates is
		615	immense (it blocks a thread for a long time) so do not use this function
		616	except to put your application under artificial I/O pressure.
		617
		618	=back
		619
		620	=head2 IO::AIO::REQ CLASS
		621
		622	All non-aggregate C<aio_*> functions return an object of this class when
		623	called in non-void context.
		624
		625	=over 4
		626
		627	=item cancel $req
		628
		629	Cancels the request, if possible. Has the effect of skipping execution
		630	when entering the B<execute> state and skipping calling the callback when
		631	entering the the B<result> state, but will leave the request otherwise
		632	untouched. That means that requests that currently execute will not be
		633	stopped and resources held by the request will not be freed prematurely.
		634
		635	=item cb $req $callback->(...)
		636
		637	Replace (or simply set) the callback registered to the request.
		638
		639	=back
		640
		641	=head2 IO::AIO::GRP CLASS
		642
		643	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		644	objects of this class, too.
		645
		646	A IO::AIO::GRP object is a special request that can contain multiple other
		647	aio requests.
		648
		649	You create one by calling the C<aio_group> constructing function with a
		650	callback that will be called when all contained requests have entered the
		651	C<done> state:
		652
		653	my $grp = aio_group sub {
		654	print "all requests are done\n";
		655	};
		656
		657	You add requests by calling the C<add> method with one or more
		658	C<IO::AIO::REQ> objects:
		659
		660	$grp->add (aio_unlink "...");
		661
		662	add $grp aio_stat "...", sub {
		663	$_[0] or return $grp->result ("error");
		664
		665	# add another request dynamically, if first succeeded
		666	add $grp aio_open "...", sub {
		667	$grp->result ("ok");
		668	};
		669	};
		670
		671	This makes it very easy to create composite requests (see the source of
		672	C<aio_move> for an application) that work and feel like simple requests.
		673
		674	=over 4
		675
		676	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		677	C<IO::AIO::poll_cb>, just like any other request.
		678
		679	=item * They can be canceled like any other request. Canceling will cancel not
		680	only the request itself, but also all requests it contains.
		681
		682	=item * They can also can also be added to other IO::AIO::GRP objects.
		683
		684	=item * You must not add requests to a group from within the group callback (or
		685	any later time).
		686
		687	=item * This does not harmonise well with C<max_outstanding>, so best do
		688	not combine C<aio_group> with it. Groups and feeders are recommended for
		689	this kind of concurrency-limiting.
		690
		691	=back
		692
		693	Their lifetime, simplified, looks like this: when they are empty, they
		694	will finish very quickly. If they contain only requests that are in the
		695	C<done> state, they will also finish. Otherwise they will continue to
		696	exist.
		697
		698	That means after creating a group you have some time to add requests. And
		699	in the callbacks of those requests, you can add further requests to the
		700	group. And only when all those requests have finished will the the group
		701	itself finish.
		702
		703	=over 4
		704
		705	=item add $grp ...
		706
		707	=item $grp->add (...)
		708
		709	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		710	be added, including other groups, as long as you do not create circular
		711	dependencies.
		712
		713	Returns all its arguments.
		714
		715	=item $grp->cancel_subs
		716
		717	Cancel all subrequests and clears any feeder, but not the group request
		718	itself. Useful when you queued a lot of events but got a result early.
		719
		720	=item $grp->result (...)
		721
		722	Set the result value(s) that will be passed to the group callback when all
		723	subrequests have finished. By default, no argument will be passed.
		724
		725	=item feed $grp $callback->($grp)
		726
		727	Sets a feeder/generator on this group: every group can have an attached
		728	generator that generates requests if idle. The idea behind this is that,
		729	although you could just queue as many requests as you want in a group,
		730	this might starve other requests for a potentially long time. For
		731	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		732	requests, delaying any later requests for a long time.
		733
		734	To avoid this, and allow incremental generation of requests, you can
		735	instead a group and set a feeder on it that generates those requests. The
		736	feed callback will be called whenever there are few enough (see C<limit>,
		737	below) requests active in the group itself and is expected to queue more
		738	requests.
		739
		740	The feed callback can queue as many requests as it likes (i.e. C<add> does
		741	not impose any limits).
		742
		743	If the feed does not queue more requests when called, it will be
		744	automatically removed from the group.
		745
		746	If the feed limit is C<0>, it will be set to C<2> automatically.
		747
		748	Example:
		749
		750	# stat all files in @files, but only ever use four aio requests concurrently:
		751
		752	my $grp = aio_group sub { print "finished\n" };
		753	limit $grp 4;
		754	feed $grp sub {
		755	my $file = pop @files
		756	or return;
		757
		758	add $grp aio_stat $file, sub { ... };
		759	};
		760
		761	=item limit $grp $num
		762
		763	Sets the feeder limit for the group: The feeder will be called whenever
		764	the group contains less than this many requests.
		765
		766	Setting the limit to C<0> will pause the feeding process.
259		767
260	=back	768	=back
261		769
262	=head2 SUPPORT FUNCTIONS	770	=head2 SUPPORT FUNCTIONS
263		771
…		…
321	IO::AIO::poll_wait, IO::AIO::poll_cb	829	IO::AIO::poll_wait, IO::AIO::poll_cb
322	if IO::AIO::nreqs;	830	if IO::AIO::nreqs;
323		831
324	=item IO::AIO::min_parallel $nthreads	832	=item IO::AIO::min_parallel $nthreads
325		833
326	Set the minimum number of AIO threads to C<$nthreads>. The current default	834	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	835	default is C<8>, which means eight asynchronous operations can execute
328	(the number of outstanding operations, however, is unlimited).	836	concurrently at any one time (the number of outstanding requests,
		837	however, is unlimited).
329		838
330	IO::AIO starts threads only on demand, when an AIO request is queued and	839	IO::AIO starts threads only on demand, when an AIO request is queued and
331	no free thread exists.	840	no free thread exists.
332		841
333	It is recommended to keep the number of threads low, as some Linux	842	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	843	Linux kernel versions will scale negatively with the number of threads
335	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	844	(higher parallelity => MUCH higher latency). With current Linux 2.6
336	threads should be fine.	845	versions, 4-32 threads should be fine.
337		846
338	Under most circumstances you don't need to call this function, as the	847	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.	848	module selects a default that is suitable for low to moderate load.
340		849
341	=item IO::AIO::max_parallel $nthreads	850	=item IO::AIO::max_parallel $nthreads
…		…
352		861
353	Under normal circumstances you don't need to call this function.	862	Under normal circumstances you don't need to call this function.
354		863
355	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	864	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
356		865
		866	[DEPRECATED]
		867
357	Sets the maximum number of outstanding requests to C<$nreqs>. If you	868	Sets the maximum number of outstanding requests to C<$nreqs>. If you
358	try to queue up more than this number of requests, the caller will block until	869	try to queue up more than this number of requests, the caller will block until
359	some requests have been handled.	870	some requests have been handled.
360		871
361	The default is very large, so normally there is no practical limit. If you	872	The default is very large, so normally there is no practical limit. If you
362	queue up many requests in a loop it often improves speed if you set	873	queue up many requests in a loop it often improves speed if you set
363	this to a relatively low number, such as C<100>.	874	this to a relatively low number, such as C<100>.
		875
		876	This function does not work well together with C<aio_group>'s, and their
		877	feeder interface is better suited to limiting concurrency, so do not use
		878	this function.
364		879
365	Under normal circumstances you don't need to call this function.	880	Under normal circumstances you don't need to call this function.
366		881
367	=back	882	=back
368		883
…		…
382	or return undef;	897	or return undef;
383		898
384	*$sym	899	*$sym
385	}	900	}
386		901
387	min_parallel 4;	902	min_parallel 8;
388		903
389	END {	904	END {
390	max_parallel 0;	905	max_parallel 0;
391	}	906	}
392		907
393	1;	908	1;
394		909
395	=head2 FORK BEHAVIOUR	910	=head2 FORK BEHAVIOUR
396		911
		912	This module should do "the right thing" when the process using it forks:
		913
397	Before the fork, IO::AIO enters a quiescent state where no requests	914	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	915	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	916	the fork the parent simply leaves the quiescent state and continues
400	request/result processing, while the child clears the request/result	917	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	918	(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	919	parent). Threads will be started on demand until the limit set in the
403	parent process has been reached again.	920	parent process has been reached again.
404		921
		922	In short: the parent will, after a short pause, continue as if fork had
		923	not been called, while the child will act as if IO::AIO has not been used
		924	yet.
		925
		926	=head2 MEMORY USAGE
		927
		928	Per-request usage:
		929
		930	Each aio request uses - depending on your architecture - around 100-200
		931	bytes of memory. In addition, stat requests need a stat buffer (possibly
		932	a few hundred bytes), readdir requires a result buffer and so on. Perl
		933	scalars and other data passed into aio requests will also be locked and
		934	will consume memory till the request has entered the done state.
		935
		936	This is now awfully much, so queuing lots of requests is not usually a
		937	problem.
		938
		939	Per-thread usage:
		940
		941	In the execution phase, some aio requests require more memory for
		942	temporary buffers, and each thread requires a stack and other data
		943	structures (usually around 16k-128k, depending on the OS).
		944
		945	=head1 KNOWN BUGS
		946
		947	Known bugs will be fixed in the next release.
		948
405	=head1 SEE ALSO	949	=head1 SEE ALSO
406		950
407	L<Coro>, L<Linux::AIO>.	951	L<Coro::AIO>.
408		952
409	=head1 AUTHOR	953	=head1 AUTHOR
410		954
411	Marc Lehmann <schmorp@schmorp.de>	955	Marc Lehmann <schmorp@schmorp.de>
412	http://home.schmorp.de/	956	http://home.schmorp.de/

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Revision 1.75 by root, Tue Oct 24 20:10:26 2006 UTC