[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 1.72 by root, Tue Oct 24 14:25:53 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	@$entries];
		522
		523	my (@dirs, @nondirs);
		524
		525	my ($statcb, $schedcb);
		526	my $nreq = 0;
		527
		528	my $statgrp = add $grp aio_group;
		529
		530	$schedcb = sub {
		531	if (@$entries) {
		532	if ($nreq < $maxreq) {
		533	my $ent = pop @$entries;
		534	$nreq++;
		535	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		536	}
		537	} elsif (!$nreq) {
		538	# finished
		539	$statgrp->cancel;
		540	undef $statcb;
		541	undef $schedcb;
		542	$grp->result (\@dirs, \@nondirs);
		543	}
		544	};
		545	$statcb = sub {
		546	my ($status, $entry) = @_;
		547
		548	if ($status < 0) {
		549	$nreq--;
		550	push @nondirs, $entry;
		551	&$schedcb;
		552	} else {
		553	# need to check for real directory
		554	add $grp aio_lstat "$path/$entry", sub {
		555	$nreq--;
		556
		557	if (-d _) {
		558	push @dirs, $entry;
		559
		560	if (!--$ndirs) {
		561	push @nondirs, @$entries;
		562	$entries = [];
		563	}
		564	} else {
		565	push @nondirs, $entry;
		566	}
		567
		568	&$schedcb;
		569	}
		570	}
		571	};
		572
		573	&$schedcb while @$entries && $nreq < $maxreq;
		574	};
		575	};
		576	};
		577
		578	$grp
		579	}
		580
247	=item aio_fsync $fh, $callback	581	=item aio_fsync $fh, $callback->($status)
248		582
249	Asynchronously call fsync on the given filehandle and call the callback	583	Asynchronously call fsync on the given filehandle and call the callback
250	with the fsync result code.	584	with the fsync result code.
251		585
252	=item aio_fdatasync $fh, $callback	586	=item aio_fdatasync $fh, $callback->($status)
253		587
254	Asynchronously call fdatasync on the given filehandle and call the	588	Asynchronously call fdatasync on the given filehandle and call the
255	callback with the fdatasync result code.	589	callback with the fdatasync result code.
256		590
257	If this call isn't available because your OS lacks it or it couldn't be	591	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.	592	detected, it will be emulated by calling C<fsync> instead.
		593
		594	=item aio_group $callback->(...)
		595
		596	[EXPERIMENTAL]
		597
		598	This is a very special aio request: Instead of doing something, it is a
		599	container for other aio requests, which is useful if you want to bundle
		600	many requests into a single, composite, request with a definite callback
		601	and the ability to cancel the whole request with its subrequests.
		602
		603	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		604	for more info.
		605
		606	Example:
		607
		608	my $grp = aio_group sub {
		609	print "all stats done\n";
		610	};
		611
		612	add $grp
		613	(aio_stat ...),
		614	(aio_stat ...),
		615	...;
		616
		617	=item aio_nop $callback->()
		618
		619	This is a special request - it does nothing in itself and is only used for
		620	side effects, such as when you want to add a dummy request to a group so
		621	that finishing the requests in the group depends on executing the given
		622	code.
		623
		624	While this request does nothing, it still goes through the execution
		625	phase and still requires a worker thread. Thus, the callback will not
		626	be executed immediately but only after other requests in the queue have
		627	entered their execution phase. This can be used to measure request
		628	latency.
		629
		630	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		631
		632	Mainly used for debugging and benchmarking, this aio request puts one of
		633	the request workers to sleep for the given time.
		634
		635	While it is theoretically handy to have simple I/O scheduling requests
		636	like sleep and file handle readable/writable, the overhead this creates is
		637	immense (it blocks a thread for a long time) so do not use this function
		638	except to put your application under artificial I/O pressure.
		639
		640	=back
		641
		642	=head2 IO::AIO::REQ CLASS
		643
		644	All non-aggregate C<aio_*> functions return an object of this class when
		645	called in non-void context.
		646
		647	=over 4
		648
		649	=item cancel $req
		650
		651	Cancels the request, if possible. Has the effect of skipping execution
		652	when entering the B<execute> state and skipping calling the callback when
		653	entering the the B<result> state, but will leave the request otherwise
		654	untouched. That means that requests that currently execute will not be
		655	stopped and resources held by the request will not be freed prematurely.
		656
		657	=item cb $req $callback->(...)
		658
		659	Replace (or simply set) the callback registered to the request.
		660
		661	=back
		662
		663	=head2 IO::AIO::GRP CLASS
		664
		665	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		666	objects of this class, too.
		667
		668	A IO::AIO::GRP object is a special request that can contain multiple other
		669	aio requests.
		670
		671	You create one by calling the C<aio_group> constructing function with a
		672	callback that will be called when all contained requests have entered the
		673	C<done> state:
		674
		675	my $grp = aio_group sub {
		676	print "all requests are done\n";
		677	};
		678
		679	You add requests by calling the C<add> method with one or more
		680	C<IO::AIO::REQ> objects:
		681
		682	$grp->add (aio_unlink "...");
		683
		684	add $grp aio_stat "...", sub {
		685	$_[0] or return $grp->result ("error");
		686
		687	# add another request dynamically, if first succeeded
		688	add $grp aio_open "...", sub {
		689	$grp->result ("ok");
		690	};
		691	};
		692
		693	This makes it very easy to create composite requests (see the source of
		694	C<aio_move> for an application) that work and feel like simple requests.
		695
		696	=over 4
		697
		698	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		699	C<IO::AIO::poll_cb>, just like any other request.
		700
		701	=item * They can be canceled like any other request. Canceling will cancel not
		702	only the request itself, but also all requests it contains.
		703
		704	=item * They can also can also be added to other IO::AIO::GRP objects.
		705
		706	=item * You must not add requests to a group from within the group callback (or
		707	any later time).
		708
		709	=item * This does not harmonise well with C<max_outstanding>, so best do
		710	not combine C<aio_group> with it. Groups and feeders are recommended for
		711	this kind of concurrency-limiting.
		712
		713	=back
		714
		715	Their lifetime, simplified, looks like this: when they are empty, they
		716	will finish very quickly. If they contain only requests that are in the
		717	C<done> state, they will also finish. Otherwise they will continue to
		718	exist.
		719
		720	That means after creating a group you have some time to add requests. And
		721	in the callbacks of those requests, you can add further requests to the
		722	group. And only when all those requests have finished will the the group
		723	itself finish.
		724
		725	=over 4
		726
		727	=item add $grp ...
		728
		729	=item $grp->add (...)
		730
		731	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		732	be added, including other groups, as long as you do not create circular
		733	dependencies.
		734
		735	Returns all its arguments.
		736
		737	=item $grp->result (...)
		738
		739	Set the result value(s) that will be passed to the group callback when all
		740	subrequests have finished. By default, no argument will be passed.
		741
		742	=item feed $grp $callback->($grp)
		743
		744	[VERY EXPERIMENTAL]
		745
		746	Sets a feeder/generator on this group: every group can have an attached
		747	generator that generates requests if idle. The idea behind this is that,
		748	although you could just queue as many requests as you want in a group,
		749	this might starve other requests for a potentially long time. For
		750	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		751	requests, delaying any later requests for a long time.
		752
		753	To avoid this, and allow incremental generation of requests, you can
		754	instead a group and set a feeder on it that generates those requests. The
		755	feed callback will be called whenever there are few enough (see C<limit>,
		756	below) requests active in the group itself and is expected to queue more
		757	requests.
		758
		759	The feed callback can queue as many requests as it likes (i.e. C<add> does
		760	not impose any limits).
		761
		762	If the feed does not queue more requests when called, it will be
		763	automatically removed from the group.
		764
		765	If the feed limit is C<0>, it will be set to C<2> automatically.
		766
		767	Example:
		768
		769	# stat all files in @files, but only ever use four aio requests concurrently:
		770
		771	my $grp = aio_group sub { print "finished\n" };
		772	limit $grp 4;
		773	feed $grp sub {
		774	my $file = pop @files
		775	or return;
		776
		777	add $grp aio_stat $file, sub { ... };
		778	};
		779
		780	=item limit $grp $num
		781
		782	Sets the feeder limit for the group: The feeder will be called whenever
		783	the group contains less than this many requests.
		784
		785	Setting the limit to C<0> will pause the feeding process.
259		786
260	=back	787	=back
261		788
262	=head2 SUPPORT FUNCTIONS	789	=head2 SUPPORT FUNCTIONS
263		790
…		…
321	IO::AIO::poll_wait, IO::AIO::poll_cb	848	IO::AIO::poll_wait, IO::AIO::poll_cb
322	if IO::AIO::nreqs;	849	if IO::AIO::nreqs;
323		850
324	=item IO::AIO::min_parallel $nthreads	851	=item IO::AIO::min_parallel $nthreads
325		852
326	Set the minimum number of AIO threads to C<$nthreads>. The current default	853	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	854	default is C<8>, which means eight asynchronous operations can execute
328	(the number of outstanding operations, however, is unlimited).	855	concurrently at any one time (the number of outstanding requests,
		856	however, is unlimited).
329		857
330	IO::AIO starts threads only on demand, when an AIO request is queued and	858	IO::AIO starts threads only on demand, when an AIO request is queued and
331	no free thread exists.	859	no free thread exists.
332		860
333	It is recommended to keep the number of threads low, as some Linux	861	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	862	Linux kernel versions will scale negatively with the number of threads
335	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	863	(higher parallelity => MUCH higher latency). With current Linux 2.6
336	threads should be fine.	864	versions, 4-32 threads should be fine.
337		865
338	Under most circumstances you don't need to call this function, as the	866	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.	867	module selects a default that is suitable for low to moderate load.
340		868
341	=item IO::AIO::max_parallel $nthreads	869	=item IO::AIO::max_parallel $nthreads
…		…
352		880
353	Under normal circumstances you don't need to call this function.	881	Under normal circumstances you don't need to call this function.
354		882
355	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	883	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
356		884
		885	[DEPRECATED]
		886
357	Sets the maximum number of outstanding requests to C<$nreqs>. If you	887	Sets the maximum number of outstanding requests to C<$nreqs>. If you
358	try to queue up more than this number of requests, the caller will block until	888	try to queue up more than this number of requests, the caller will block until
359	some requests have been handled.	889	some requests have been handled.
360		890
361	The default is very large, so normally there is no practical limit. If you	891	The default is very large, so normally there is no practical limit. If you
362	queue up many requests in a loop it often improves speed if you set	892	queue up many requests in a loop it often improves speed if you set
363	this to a relatively low number, such as C<100>.	893	this to a relatively low number, such as C<100>.
		894
		895	This function does not work well together with C<aio_group>'s, and their
		896	feeder interface is better suited to limiting concurrency, so do not use
		897	this function.
364		898
365	Under normal circumstances you don't need to call this function.	899	Under normal circumstances you don't need to call this function.
366		900
367	=back	901	=back
368		902
…		…
382	or return undef;	916	or return undef;
383		917
384	*$sym	918	*$sym
385	}	919	}
386		920
387	min_parallel 4;	921	min_parallel 8;
388		922
389	END {	923	END {
390	max_parallel 0;	924	max_parallel 0;
391	}	925	}
392		926
393	1;	927	1;
394		928
395	=head2 FORK BEHAVIOUR	929	=head2 FORK BEHAVIOUR
396		930
		931	This module should do "the right thing" when the process using it forks:
		932
397	Before the fork, IO::AIO enters a quiescent state where no requests	933	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	934	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	935	the fork the parent simply leaves the quiescent state and continues
400	request/result processing, while the child clears the request/result	936	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	937	(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	938	parent). Threads will be started on demand until the limit set in the
403	parent process has been reached again.	939	parent process has been reached again.
404		940
		941	Temporary memory that was allocated for request processing is not
		942	reclaimed in the child, however. While this is possible in some cases, it
		943	is almost impossible in others (threads are evil you know), so you will
		944	have to live with it. This is around 64k buffer (for sendfile, readahead
		945	emulation) + the size of the directory being scanned (readdir).
		946
		947	In short: the parent will, after a short pause, continue as if fork had
		948	not been called, while the child will act as if IO::AIO has not been used
		949	yet.
		950
		951	=head2 MEMORY USAGE
		952
		953	Per-request usage:
		954
		955	Each aio request uses - depending on your architecture - around 100-200
		956	bytes of memory. In addition, stat requests need a stat buffer (possibly
		957	a few hundred bytes), readdir requires a result buffer and so on. Perl
		958	scalars and other data passed into aio requests will also be locked and
		959	will consume memory till the request has entered the done state.
		960
		961	This is now awfully much, so queuing lots of requests is not usually a
		962	problem.
		963
		964	Per-thread usage:
		965
		966	In the execution phase, some aio requests require more memory for
		967	temporary buffers, and each thread requires a stack and other data
		968	structures (usually around 16k-128k, depending on the OS).
		969
		970	=head1 KNOWN BUGS
		971
		972	See FORK BEHAVIOUR, above.
		973
405	=head1 SEE ALSO	974	=head1 SEE ALSO
406		975
407	L<Coro>, L<Linux::AIO>.	976	L<Coro::AIO>.
408		977
409	=head1 AUTHOR	978	=head1 AUTHOR
410		979
411	Marc Lehmann <schmorp@schmorp.de>	980	Marc Lehmann <schmorp@schmorp.de>
412	http://home.schmorp.de/	981	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 1.72 by root, Tue Oct 24 14:25:53 2006 UTC

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Revision 1.72 by root, Tue Oct 24 14:25:53 2006 UTC