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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.46 by root, Mon Dec 26 20:17:13 2005 UTC vs.
Revision 1.85 by root, Sat Oct 28 01:40:30 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	# AnyEvent	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
21	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
22	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });	32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
23		33
24	# Event	34	# Event integration
25	Event->io (fd => IO::AIO::poll_fileno,	35	Event->io (fd => IO::AIO::poll_fileno,
26	poll => 'r',	36	poll => 'r',
27	cb => \&IO::AIO::poll_cb);	37	cb => \&IO::AIO::poll_cb);
28		38
29	# Glib/Gtk2	39	# Glib/Gtk2 integration
30	add_watch Glib::IO IO::AIO::poll_fileno,	40	add_watch Glib::IO IO::AIO::poll_fileno,
31	in => sub { IO::AIO::poll_cb; 1 };	41	in => sub { IO::AIO::poll_cb; 1 };
32		42
33	# Tk	43	# Tk integration
34	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
35	readable => \&IO::AIO::poll_cb);	45	readable => \&IO::AIO::poll_cb);
36		46
37	# Danga::Socket	47	# Danga::Socket integration
38	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
39	\&IO::AIO::poll_cb);	49	\&IO::AIO::poll_cb);
40		50
41
42	=head1 DESCRIPTION	51	=head1 DESCRIPTION
43		52
44	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
45	operating system supports.	54	operating system supports.
46		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
47	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
48	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
49	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
50	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
51	aio functions available on many operating systems. However, they are often	76	functions available on many operating systems. However, they are often
52	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
53	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
54	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.
55		81
56	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-)
57	currently not reentrant, so use appropriate locking yourself, always call	83	threads, it is currently not reentrant in any way, so use appropriate
58	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	84	locking yourself, always call C<poll_cb> from within the same thread, or
59	C<aio_> functions) recursively.	85	never call C<poll_cb> (or other C<aio_> functions) recursively.
		86
		87	=head1 REQUEST ANATOMY AND LIFETIME
		88
		89	Every C<aio_*> function creates a request. which is a C data structure not
		90	directly visible to Perl.
		91
		92	If called in non-void context, every request function returns a Perl
		93	object representing the request. In void context, nothing is returned,
		94	which saves a bit of memory.
		95
		96	The perl object is a fairly standard ref-to-hash object. The hash contents
		97	are not used by IO::AIO so you are free to store anything you like in it.
		98
		99	During their existance, aio requests travel through the following states,
		100	in order:
		101
		102	=over 4
		103
		104	=item ready
		105
		106	Immediately after a request is created it is put into the ready state,
		107	waiting for a thread to execute it.
		108
		109	=item execute
		110
		111	A thread has accepted the request for processing and is currently
		112	executing it (e.g. blocking in read).
		113
		114	=item pending
		115
		116	The request has been executed and is waiting for result processing.
		117
		118	While request submission and execution is fully asynchronous, result
		119	processing is not and relies on the perl interpreter calling C<poll_cb>
		120	(or another function with the same effect).
		121
		122	=item result
		123
		124	The request results are processed synchronously by C<poll_cb>.
		125
		126	The C<poll_cb> function will process all outstanding aio requests by
		127	calling their callbacks, freeing memory associated with them and managing
		128	any groups they are contained in.
		129
		130	=item done
		131
		132	Request has reached the end of its lifetime and holds no resources anymore
		133	(except possibly for the Perl object, but its connection to the actual
		134	aio request is severed and calling its methods will either do nothing or
		135	result in a runtime error).
60		136
61	=cut	137	=cut
62		138
63	package IO::AIO;	139	package IO::AIO;
64		140
65	no warnings;	141	no warnings;
		142	use strict 'vars';
66		143
67	use base 'Exporter';	144	use base 'Exporter';
68		145
69	use Fcntl ();
70
71	BEGIN {	146	BEGIN {
72	$VERSION = '1.71';	147	our $VERSION = '2.0';
73		148
74	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	149	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
75	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	150	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
76	aio_fsync aio_fdatasync aio_readahead);	151	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
77	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	152	aio_copy aio_group aio_nop aio_mknod);
78	max_outstanding nreqs);	153	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		154	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		155	min_parallel max_parallel nreqs nready npending);
		156
		157	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
79		158
80	require XSLoader;	159	require XSLoader;
81	XSLoader::load IO::AIO, $VERSION;	160	XSLoader::load ("IO::AIO", $VERSION);
82	}	161	}
83		162
84	=head1 FUNCTIONS	163	=head1 FUNCTIONS
85		164
86	=head2 AIO FUNCTIONS	165	=head2 AIO FUNCTIONS
…		…
94	syscall has been executed asynchronously.	173	syscall has been executed asynchronously.
95		174
96	All functions expecting a filehandle keep a copy of the filehandle	175	All functions expecting a filehandle keep a copy of the filehandle
97	internally until the request has finished.	176	internally until the request has finished.
98		177
		178	All requests return objects of type L<IO::AIO::REQ> that allow further
		179	manipulation of those requests while they are in-flight.
		180
99	The pathnames you pass to these routines I<must> be absolute and	181	The pathnames you pass to these routines I<must> be absolute and
100	encoded in byte form. The reason for the former is that at the time the	182	encoded in byte form. The reason for the former is that at the time the
101	request is being executed, the current working directory could have	183	request is being executed, the current working directory could have
102	changed. Alternatively, you can make sure that you never change the	184	changed. Alternatively, you can make sure that you never change the
103	current working directory.	185	current working directory.
…		…
108	your pathnames to the locale (or other) encoding in effect in the user	190	your pathnames to the locale (or other) encoding in effect in the user
109	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	191	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
110	use something else.	192	use something else.
111		193
112	=over 4	194	=over 4
		195
		196	=item $prev_pri = aioreq_pri [$pri]
		197
		198	Returns the priority value that would be used for the next request and, if
		199	C<$pri> is given, sets the priority for the next aio request.
		200
		201	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		202	and C<4>, respectively. Requests with higher priority will be serviced
		203	first.
		204
		205	The priority will be reset to C<0> after each call to one of the C<aio_*>
		206	functions.
		207
		208	Example: open a file with low priority, then read something from it with
		209	higher priority so the read request is serviced before other low priority
		210	open requests (potentially spamming the cache):
		211
		212	aioreq_pri -3;
		213	aio_open ..., sub {
		214	return unless $_[0];
		215
		216	aioreq_pri -2;
		217	aio_read $_[0], ..., sub {
		218	...
		219	};
		220	};
		221
		222	=item aioreq_nice $pri_adjust
		223
		224	Similar to C<aioreq_pri>, but subtracts the given value from the current
		225	priority, so effects are cumulative.
113		226
114	=item aio_open $pathname, $flags, $mode, $callback->($fh)	227	=item aio_open $pathname, $flags, $mode, $callback->($fh)
115		228
116	Asynchronously open or create a file and call the callback with a newly	229	Asynchronously open or create a file and call the callback with a newly
117	created filehandle for the file.	230	created filehandle for the file.
…		…
232	=item aio_unlink $pathname, $callback->($status)	345	=item aio_unlink $pathname, $callback->($status)
233		346
234	Asynchronously unlink (delete) a file and call the callback with the	347	Asynchronously unlink (delete) a file and call the callback with the
235	result code.	348	result code.
236		349
		350	=item aio_mknod $path, $mode, $dev, $callback->($status)
		351
		352	Asynchronously create a device node (or fifo). See mknod(2).
		353
		354	The only portable (POSIX) way of calling this function is:
		355
		356	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		357
		358	=item aio_link $srcpath, $dstpath, $callback->($status)
		359
		360	Asynchronously create a new link to the existing object at C<$srcpath> at
		361	the path C<$dstpath> and call the callback with the result code.
		362
		363	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		364
		365	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		366	the path C<$dstpath> and call the callback with the result code.
		367
		368	=item aio_rename $srcpath, $dstpath, $callback->($status)
		369
		370	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		371	rename(2) and call the callback with the result code.
		372
237	=item aio_rmdir $pathname, $callback->($status)	373	=item aio_rmdir $pathname, $callback->($status)
238		374
239	Asynchronously rmdir (delete) a directory and call the callback with the	375	Asynchronously rmdir (delete) a directory and call the callback with the
240	result code.	376	result code.
241		377
…		…
246	sorted, and will B<NOT> include the C<.> and C<..> entries.	382	sorted, and will B<NOT> include the C<.> and C<..> entries.
247		383
248	The callback a single argument which is either C<undef> or an array-ref	384	The callback a single argument which is either C<undef> or an array-ref
249	with the filenames.	385	with the filenames.
250		386
		387	=item aio_copy $srcpath, $dstpath, $callback->($status)
		388
		389	Try to copy the I<file> (directories not supported as either source or
		390	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		391	the C<0> (error) or C<-1> ok.
		392
		393	This is a composite request that it creates the destination file with
		394	mode 0200 and copies the contents of the source file into it using
		395	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		396	uid/gid, in that order.
		397
		398	If an error occurs, the partial destination file will be unlinked, if
		399	possible, except when setting atime, mtime, access mode and uid/gid, where
		400	errors are being ignored.
		401
		402	=cut
		403
		404	sub aio_copy($$;$) {
		405	my ($src, $dst, $cb) = @_;
		406
		407	my $pri = aioreq_pri;
		408	my $grp = aio_group $cb;
		409
		410	aioreq_pri $pri;
		411	add $grp aio_open $src, O_RDONLY, 0, sub {
		412	if (my $src_fh = $_[0]) {
		413	my @stat = stat $src_fh;
		414
		415	aioreq_pri $pri;
		416	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		417	if (my $dst_fh = $_[0]) {
		418	aioreq_pri $pri;
		419	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		420	if ($_[0] == $stat[7]) {
		421	$grp->result (0);
		422	close $src_fh;
		423
		424	# those should not normally block. should. should.
		425	utime $stat[8], $stat[9], $dst;
		426	chmod $stat[2] & 07777, $dst_fh;
		427	chown $stat[4], $stat[5], $dst_fh;
		428	close $dst_fh;
		429	} else {
		430	$grp->result (-1);
		431	close $src_fh;
		432	close $dst_fh;
		433
		434	aioreq $pri;
		435	add $grp aio_unlink $dst;
		436	}
		437	};
		438	} else {
		439	$grp->result (-1);
		440	}
		441	},
		442
		443	} else {
		444	$grp->result (-1);
		445	}
		446	};
		447
		448	$grp
		449	}
		450
		451	=item aio_move $srcpath, $dstpath, $callback->($status)
		452
		453	Try to move the I<file> (directories not supported as either source or
		454	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		455	the C<0> (error) or C<-1> ok.
		456
		457	This is a composite request that tries to rename(2) the file first. If
		458	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		459	that is successful, unlinking the C<$srcpath>.
		460
		461	=cut
		462
		463	sub aio_move($$;$) {
		464	my ($src, $dst, $cb) = @_;
		465
		466	my $pri = aioreq_pri;
		467	my $grp = aio_group $cb;
		468
		469	aioreq_pri $pri;
		470	add $grp aio_rename $src, $dst, sub {
		471	if ($_[0] && $! == EXDEV) {
		472	aioreq_pri $pri;
		473	add $grp aio_copy $src, $dst, sub {
		474	$grp->result ($_[0]);
		475
		476	if (!$_[0]) {
		477	aioreq_pri $pri;
		478	add $grp aio_unlink $src;
		479	}
		480	};
		481	} else {
		482	$grp->result ($_[0]);
		483	}
		484	};
		485
		486	$grp
		487	}
		488
251	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	489	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
252		490
253	Scans a directory (similar to C<aio_readdir>) and tries to separate the	491	Scans a directory (similar to C<aio_readdir>) but additionally tries to
254	entries of directory C<$path> into two sets of names, ones you can recurse	492	efficiently separate the entries of directory C<$path> into two sets of
255	into (directories), and ones you cannot recurse into (everything else).	493	names, directories you can recurse into (directories), and ones you cannot
		494	recurse into (everything else, including symlinks to directories).
256		495
257	C<aio_scandir> is a composite request that consists of many	496	C<aio_scandir> is a composite request that creates of many sub requests_
258	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	497	C<$maxreq> specifies the maximum number of outstanding aio requests that
259	aio requests that this function generates. If it is C<< <= 0 >>, then a	498	this function generates. If it is C<< <= 0 >>, then a suitable default
260	suitable default will be chosen (currently 8).	499	will be chosen (currently 4).
261		500
262	On error, the callback is called without arguments, otherwise it receives	501	On error, the callback is called without arguments, otherwise it receives
263	two array-refs with path-relative entry names.	502	two array-refs with path-relative entry names.
264		503
265	Example:	504	Example:
…		…
273	Implementation notes.	512	Implementation notes.
274		513
275	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	514	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
276		515
277	After reading the directory, the modification time, size etc. of the	516	After reading the directory, the modification time, size etc. of the
278	directory before and after the readdir is checked, and if they match, the	517	directory before and after the readdir is checked, and if they match (and
279	link count will be used to decide how many entries are directories (if	518	isn't the current time), the link count will be used to decide how many
280	>= 2). Otherwise, no knowledge of the number of subdirectories will be	519	entries are directories (if >= 2). Otherwise, no knowledge of the number
281	assumed.	520	of subdirectories will be assumed.
282		521
283	Then entires will be sorted into likely directories (everything without a	522	Then entries will be sorted into likely directories (everything without
284	non-initial dot) and likely non-directories (everything else). Then every	523	a non-initial dot currently) and likely non-directories (everything
285	entry + C</.> will be C<stat>'ed, likely directories first. This is often	524	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		525	likely directories first. If that succeeds, it assumes that the entry
		526	is a directory or a symlink to directory (which will be checked
		527	seperately). This is often faster than stat'ing the entry itself because
286	faster because filesystems might detect the type of the entry without	528	filesystems might detect the type of the entry without reading the inode
287	reading the inode data (e.g. ext2s filetype feature). If that succeeds,	529	data (e.g. ext2fs filetype feature).
288	it assumes that the entry is a directory or a symlink to directory (which
289	will be checked seperately).
290		530
291	If the known number of directories has been reached, the rest of the	531	If the known number of directories (link count - 2) has been reached, the
292	entries is assumed to be non-directories.	532	rest of the entries is assumed to be non-directories.
		533
		534	This only works with certainty on POSIX (= UNIX) filesystems, which
		535	fortunately are the vast majority of filesystems around.
		536
		537	It will also likely work on non-POSIX filesystems with reduced efficiency
		538	as those tend to return 0 or 1 as link counts, which disables the
		539	directory counting heuristic.
293		540
294	=cut	541	=cut
295		542
296	sub aio_scandir($$$) {	543	sub aio_scandir($$$) {
297	my ($path, $maxreq, $cb) = @_;	544	my ($path, $maxreq, $cb) = @_;
298		545
		546	my $pri = aioreq_pri;
		547
		548	my $grp = aio_group $cb;
		549
299	$maxreq = 8 if $maxreq <= 0;	550	$maxreq = 4 if $maxreq <= 0;
300		551
301	# stat once	552	# stat once
		553	aioreq_pri $pri;
302	aio_stat $path, sub {	554	add $grp aio_stat $path, sub {
303	$cb->() if $_[0];	555	return $grp->result () if $_[0];
		556	my $now = time;
304	my $hash1 = join ":", (stat _)[0,1,3,7,9];	557	my $hash1 = join ":", (stat _)[0,1,3,7,9];
305		558
306	# read the directory entries	559	# read the directory entries
		560	aioreq_pri $pri;
307	aio_readdir $path, sub {	561	add $grp aio_readdir $path, sub {
308	my $entries = shift	562	my $entries = shift
309	or return $cb->();	563	or return $grp->result ();
310		564
311	# stat the dir another time	565	# stat the dir another time
		566	aioreq_pri $pri;
312	aio_stat $path, sub {	567	add $grp aio_stat $path, sub {
313	my $hash2 = join ":", (stat _)[0,1,3,7,9];	568	my $hash2 = join ":", (stat _)[0,1,3,7,9];
314		569
315	my $ndirs;	570	my $ndirs;
316		571
317	# take the slow route if anything looks fishy	572	# take the slow route if anything looks fishy
318	if ($hash1 ne $hash2) {	573	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
319	$ndirs = -1;	574	$ndirs = -1;
320	} else {	575	} else {
321	# if nlink == 2, we are finished	576	# if nlink == 2, we are finished
322	# on non-posix-fs's, we rely on nlink < 2	577	# on non-posix-fs's, we rely on nlink < 2
323	$ndirs = (stat _)[3] - 2	578	$ndirs = (stat _)[3] - 2
324	or return $cb->([], $entries);	579	or return $grp->result ([], $entries);
325	}	580	}
326		581
327	# sort into likely dirs and likely nondirs	582	# sort into likely dirs and likely nondirs
328	# dirs == files without ".", short entries first	583	# dirs == files without ".", short entries first
329	$entries = [map $_->[0],	584	$entries = [map $_->[0],
…		…
331	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	586	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
332	@$entries];	587	@$entries];
333		588
334	my (@dirs, @nondirs);	589	my (@dirs, @nondirs);
335		590
336	my ($statcb, $schedcb);	591	my $statgrp = add $grp aio_group sub {
337	my $nreq = 0;	592	$grp->result (\@dirs, \@nondirs);
		593	};
338		594
339	$schedcb = sub {	595	limit $statgrp $maxreq;
340	if (@$entries) {	596	feed $statgrp sub {
341	if ($nreq < $maxreq) {	597	return unless @$entries;
342	my $ent = pop @$entries;	598	my $entry = pop @$entries;
		599
		600	aioreq_pri $pri;
		601	add $statgrp aio_stat "$path/$entry/.", sub {
		602	if ($_[0] < 0) {
		603	push @nondirs, $entry;
		604	} else {
		605	# need to check for real directory
		606	aioreq_pri $pri;
		607	add $statgrp aio_lstat "$path/$entry", sub {
		608	if (-d _) {
		609	push @dirs, $entry;
		610
		611	unless (--$ndirs) {
		612	push @nondirs, @$entries;
		613	feed $statgrp;
		614	}
		615	} else {
		616	push @nondirs, $entry;
		617	}
343	$nreq++;	618	}
344	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
345	}	619	}
346	} elsif (!$nreq) {
347	# finished
348	undef $statcb;
349	undef $schedcb;
350	$cb->(\@dirs, \@nondirs) if $cb;
351	undef $cb;
352	}	620	};
353	};	621	};
354	$statcb = sub {
355	my ($status, $entry) = @_;
356
357	if ($status < 0) {
358	$nreq--;
359	push @nondirs, $entry;
360	&$schedcb;
361	} else {
362	# need to check for real directory
363	aio_lstat "$path/$entry", sub {
364	$nreq--;
365
366	if (-d _) {
367	push @dirs, $entry;
368
369	if (!--$ndirs) {
370	push @nondirs, @$entries;
371	$entries = [];
372	}
373	} else {
374	push @nondirs, $entry;
375	}
376
377	&$schedcb;
378	}
379	}
380	};
381
382	&$schedcb while @$entries && $nreq < $maxreq;
383	};	622	};
384	};	623	};
385	};	624	};
		625
		626	$grp
386	}	627	}
387		628
388	=item aio_fsync $fh, $callback->($status)	629	=item aio_fsync $fh, $callback->($status)
389		630
390	Asynchronously call fsync on the given filehandle and call the callback	631	Asynchronously call fsync on the given filehandle and call the callback
…		…
395	Asynchronously call fdatasync on the given filehandle and call the	636	Asynchronously call fdatasync on the given filehandle and call the
396	callback with the fdatasync result code.	637	callback with the fdatasync result code.
397		638
398	If this call isn't available because your OS lacks it or it couldn't be	639	If this call isn't available because your OS lacks it or it couldn't be
399	detected, it will be emulated by calling C<fsync> instead.	640	detected, it will be emulated by calling C<fsync> instead.
		641
		642	=item aio_group $callback->(...)
		643
		644	This is a very special aio request: Instead of doing something, it is a
		645	container for other aio requests, which is useful if you want to bundle
		646	many requests into a single, composite, request with a definite callback
		647	and the ability to cancel the whole request with its subrequests.
		648
		649	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		650	for more info.
		651
		652	Example:
		653
		654	my $grp = aio_group sub {
		655	print "all stats done\n";
		656	};
		657
		658	add $grp
		659	(aio_stat ...),
		660	(aio_stat ...),
		661	...;
		662
		663	=item aio_nop $callback->()
		664
		665	This is a special request - it does nothing in itself and is only used for
		666	side effects, such as when you want to add a dummy request to a group so
		667	that finishing the requests in the group depends on executing the given
		668	code.
		669
		670	While this request does nothing, it still goes through the execution
		671	phase and still requires a worker thread. Thus, the callback will not
		672	be executed immediately but only after other requests in the queue have
		673	entered their execution phase. This can be used to measure request
		674	latency.
		675
		676	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		677
		678	Mainly used for debugging and benchmarking, this aio request puts one of
		679	the request workers to sleep for the given time.
		680
		681	While it is theoretically handy to have simple I/O scheduling requests
		682	like sleep and file handle readable/writable, the overhead this creates is
		683	immense (it blocks a thread for a long time) so do not use this function
		684	except to put your application under artificial I/O pressure.
		685
		686	=back
		687
		688	=head2 IO::AIO::REQ CLASS
		689
		690	All non-aggregate C<aio_*> functions return an object of this class when
		691	called in non-void context.
		692
		693	=over 4
		694
		695	=item cancel $req
		696
		697	Cancels the request, if possible. Has the effect of skipping execution
		698	when entering the B<execute> state and skipping calling the callback when
		699	entering the the B<result> state, but will leave the request otherwise
		700	untouched. That means that requests that currently execute will not be
		701	stopped and resources held by the request will not be freed prematurely.
		702
		703	=item cb $req $callback->(...)
		704
		705	Replace (or simply set) the callback registered to the request.
		706
		707	=back
		708
		709	=head2 IO::AIO::GRP CLASS
		710
		711	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		712	objects of this class, too.
		713
		714	A IO::AIO::GRP object is a special request that can contain multiple other
		715	aio requests.
		716
		717	You create one by calling the C<aio_group> constructing function with a
		718	callback that will be called when all contained requests have entered the
		719	C<done> state:
		720
		721	my $grp = aio_group sub {
		722	print "all requests are done\n";
		723	};
		724
		725	You add requests by calling the C<add> method with one or more
		726	C<IO::AIO::REQ> objects:
		727
		728	$grp->add (aio_unlink "...");
		729
		730	add $grp aio_stat "...", sub {
		731	$_[0] or return $grp->result ("error");
		732
		733	# add another request dynamically, if first succeeded
		734	add $grp aio_open "...", sub {
		735	$grp->result ("ok");
		736	};
		737	};
		738
		739	This makes it very easy to create composite requests (see the source of
		740	C<aio_move> for an application) that work and feel like simple requests.
		741
		742	=over 4
		743
		744	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		745	C<IO::AIO::poll_cb>, just like any other request.
		746
		747	=item * They can be canceled like any other request. Canceling will cancel not
		748	only the request itself, but also all requests it contains.
		749
		750	=item * They can also can also be added to other IO::AIO::GRP objects.
		751
		752	=item * You must not add requests to a group from within the group callback (or
		753	any later time).
		754
		755	=back
		756
		757	Their lifetime, simplified, looks like this: when they are empty, they
		758	will finish very quickly. If they contain only requests that are in the
		759	C<done> state, they will also finish. Otherwise they will continue to
		760	exist.
		761
		762	That means after creating a group you have some time to add requests. And
		763	in the callbacks of those requests, you can add further requests to the
		764	group. And only when all those requests have finished will the the group
		765	itself finish.
		766
		767	=over 4
		768
		769	=item add $grp ...
		770
		771	=item $grp->add (...)
		772
		773	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		774	be added, including other groups, as long as you do not create circular
		775	dependencies.
		776
		777	Returns all its arguments.
		778
		779	=item $grp->cancel_subs
		780
		781	Cancel all subrequests and clears any feeder, but not the group request
		782	itself. Useful when you queued a lot of events but got a result early.
		783
		784	=item $grp->result (...)
		785
		786	Set the result value(s) that will be passed to the group callback when all
		787	subrequests have finished and set thre groups errno to the current value
		788	of errno (just like calling C<errno> without an error number). By default,
		789	no argument will be passed and errno is zero.
		790
		791	=item $grp->errno ([$errno])
		792
		793	Sets the group errno value to C<$errno>, or the current value of errno
		794	when the argument is missing.
		795
		796	Every aio request has an associated errno value that is restored when
		797	the callback is invoked. This method lets you change this value from its
		798	default (0).
		799
		800	Calling C<result> will also set errno, so make sure you either set C<$!>
		801	before the call to C<result>, or call c<errno> after it.
		802
		803	=item feed $grp $callback->($grp)
		804
		805	Sets a feeder/generator on this group: every group can have an attached
		806	generator that generates requests if idle. The idea behind this is that,
		807	although you could just queue as many requests as you want in a group,
		808	this might starve other requests for a potentially long time. For
		809	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		810	requests, delaying any later requests for a long time.
		811
		812	To avoid this, and allow incremental generation of requests, you can
		813	instead a group and set a feeder on it that generates those requests. The
		814	feed callback will be called whenever there are few enough (see C<limit>,
		815	below) requests active in the group itself and is expected to queue more
		816	requests.
		817
		818	The feed callback can queue as many requests as it likes (i.e. C<add> does
		819	not impose any limits).
		820
		821	If the feed does not queue more requests when called, it will be
		822	automatically removed from the group.
		823
		824	If the feed limit is C<0>, it will be set to C<2> automatically.
		825
		826	Example:
		827
		828	# stat all files in @files, but only ever use four aio requests concurrently:
		829
		830	my $grp = aio_group sub { print "finished\n" };
		831	limit $grp 4;
		832	feed $grp sub {
		833	my $file = pop @files
		834	or return;
		835
		836	add $grp aio_stat $file, sub { ... };
		837	};
		838
		839	=item limit $grp $num
		840
		841	Sets the feeder limit for the group: The feeder will be called whenever
		842	the group contains less than this many requests.
		843
		844	Setting the limit to C<0> will pause the feeding process.
400		845
401	=back	846	=back
402		847
403	=head2 SUPPORT FUNCTIONS	848	=head2 SUPPORT FUNCTIONS
404		849
…		…
417		862
418	Process all outstanding events on the result pipe. You have to call this	863	Process all outstanding events on the result pipe. You have to call this
419	regularly. Returns the number of events processed. Returns immediately	864	regularly. Returns the number of events processed. Returns immediately
420	when no events are outstanding.	865	when no events are outstanding.
421		866
		867	If not all requests were processed for whatever reason, the filehandle
		868	will still be ready when C<poll_cb> returns.
		869
422	Example: Install an Event watcher that automatically calls	870	Example: Install an Event watcher that automatically calls
423	IO::AIO::poll_cb with high priority:	871	IO::AIO::poll_cb with high priority:
424		872
425	Event->io (fd => IO::AIO::poll_fileno,	873	Event->io (fd => IO::AIO::poll_fileno,
426	poll => 'r', async => 1,	874	poll => 'r', async => 1,
427	cb => \&IO::AIO::poll_cb);	875	cb => \&IO::AIO::poll_cb);
428		876
		877	=item IO::AIO::poll_some $max_requests
		878
		879	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests
		880	at a time.
		881
		882	Useful if you want to ensure some level of interactiveness when perl is
		883	not fast enough to process all requests in time.
		884
		885	Example: Install an Event watcher that automatically calls
		886	IO::AIO::poll_some with low priority, to ensure that other parts of the
		887	program get the CPU sometimes even under high AIO load.
		888
		889	Event->io (fd => IO::AIO::poll_fileno,
		890	poll => 'r', nice => 1,
		891	cb => sub { IO::AIO::poll_some 256 });
		892
429	=item IO::AIO::poll_wait	893	=item IO::AIO::poll_wait
430		894
431	Wait till the result filehandle becomes ready for reading (simply does a	895	Wait till the result filehandle becomes ready for reading (simply does a
432	C<select> on the filehandle. This is useful if you want to synchronously wait	896	C<select> on the filehandle. This is useful if you want to synchronously wait
433	for some requests to finish).	897	for some requests to finish).
434		898
435	See C<nreqs> for an example.	899	See C<nreqs> for an example.
436		900
437	=item IO::AIO::nreqs	901	=item IO::AIO::nreqs
438		902
439	Returns the number of requests currently outstanding (i.e. for which their	903	Returns the number of requests currently in the ready, execute or pending
440	callback has not been invoked yet).	904	states (i.e. for which their callback has not been invoked yet).
441		905
442	Example: wait till there are no outstanding requests anymore:	906	Example: wait till there are no outstanding requests anymore:
443		907
444	IO::AIO::poll_wait, IO::AIO::poll_cb	908	IO::AIO::poll_wait, IO::AIO::poll_cb
445	while IO::AIO::nreqs;	909	while IO::AIO::nreqs;
446		910
		911	=item IO::AIO::nready
		912
		913	Returns the number of requests currently in the ready state (not yet
		914	executed).
		915
		916	=item IO::AIO::npending
		917
		918	Returns the number of requests currently in the pending state (executed,
		919	but not yet processed by poll_cb).
		920
447	=item IO::AIO::flush	921	=item IO::AIO::flush
448		922
449	Wait till all outstanding AIO requests have been handled.	923	Wait till all outstanding AIO requests have been handled.
450		924
451	Strictly equivalent to:	925	Strictly equivalent to:
…		…
462	IO::AIO::poll_wait, IO::AIO::poll_cb	936	IO::AIO::poll_wait, IO::AIO::poll_cb
463	if IO::AIO::nreqs;	937	if IO::AIO::nreqs;
464		938
465	=item IO::AIO::min_parallel $nthreads	939	=item IO::AIO::min_parallel $nthreads
466		940
467	Set the minimum number of AIO threads to C<$nthreads>. The current default	941	Set the minimum number of AIO threads to C<$nthreads>. The current
468	is C<4>, which means four asynchronous operations can be done at one time	942	default is C<8>, which means eight asynchronous operations can execute
469	(the number of outstanding operations, however, is unlimited).	943	concurrently at any one time (the number of outstanding requests,
		944	however, is unlimited).
470		945
471	IO::AIO starts threads only on demand, when an AIO request is queued and	946	IO::AIO starts threads only on demand, when an AIO request is queued and
472	no free thread exists.	947	no free thread exists.
473		948
474	It is recommended to keep the number of threads low, as some Linux	949	It is recommended to keep the number of threads relatively low, as some
475	kernel versions will scale negatively with the number of threads (higher	950	Linux kernel versions will scale negatively with the number of threads
476	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	951	(higher parallelity => MUCH higher latency). With current Linux 2.6
477	threads should be fine.	952	versions, 4-32 threads should be fine.
478		953
479	Under most circumstances you don't need to call this function, as the	954	Under most circumstances you don't need to call this function, as the
480	module selects a default that is suitable for low to moderate load.	955	module selects a default that is suitable for low to moderate load.
481		956
482	=item IO::AIO::max_parallel $nthreads	957	=item IO::AIO::max_parallel $nthreads
…		…
491	This module automatically runs C<max_parallel 0> at program end, to ensure	966	This module automatically runs C<max_parallel 0> at program end, to ensure
492	that all threads are killed and that there are no outstanding requests.	967	that all threads are killed and that there are no outstanding requests.
493		968
494	Under normal circumstances you don't need to call this function.	969	Under normal circumstances you don't need to call this function.
495		970
496	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	971	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		972
		973	This is a very bad function to use in interactive programs because it
		974	blocks, and a bad way to reduce concurrency because it is inexact: Better
		975	use an C<aio_group> together with a feed callback.
497		976
498	Sets the maximum number of outstanding requests to C<$nreqs>. If you	977	Sets the maximum number of outstanding requests to C<$nreqs>. If you
499	try to queue up more than this number of requests, the caller will block until	978	to queue up more than this number of requests, the next call to the
500	some requests have been handled.	979	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		980	function will block until the limit is no longer exceeded.
501		981
502	The default is very large, so normally there is no practical limit. If you	982	The default value is very large, so there is no practical limit on the
503	queue up many requests in a loop it often improves speed if you set	983	number of outstanding requests.
504	this to a relatively low number, such as C<100>.
505		984
506	Under normal circumstances you don't need to call this function.	985	You can still queue as many requests as you want. Therefore,
		986	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		987	as a stop gap to shield against fatal memory overflow (with large values).
507		988
508	=back	989	=back
509		990
510	=cut	991	=cut
511		992
…		…
523	or return undef;	1004	or return undef;
524		1005
525	*$sym	1006	*$sym
526	}	1007	}
527		1008
528	min_parallel 4;	1009	min_parallel 8;
529		1010
530	END {	1011	END {
531	max_parallel 0;	1012	min_parallel 1;
532	}	1013	flush;
		1014	};
533		1015
534	1;	1016	1;
535		1017
536	=head2 FORK BEHAVIOUR	1018	=head2 FORK BEHAVIOUR
		1019
		1020	This module should do "the right thing" when the process using it forks:
537		1021
538	Before the fork, IO::AIO enters a quiescent state where no requests	1022	Before the fork, IO::AIO enters a quiescent state where no requests
539	can be added in other threads and no results will be processed. After	1023	can be added in other threads and no results will be processed. After
540	the fork the parent simply leaves the quiescent state and continues	1024	the fork the parent simply leaves the quiescent state and continues
541	request/result processing, while the child clears the request/result	1025	request/result processing, while the child frees the request/result queue
542	queue (so the requests started before the fork will only be handled in	1026	(so that the requests started before the fork will only be handled in the
543	the parent). Threats will be started on demand until the limit ste in the	1027	parent). Threads will be started on demand until the limit set in the
544	parent process has been reached again.	1028	parent process has been reached again.
545		1029
		1030	In short: the parent will, after a short pause, continue as if fork had
		1031	not been called, while the child will act as if IO::AIO has not been used
		1032	yet.
		1033
		1034	=head2 MEMORY USAGE
		1035
		1036	Per-request usage:
		1037
		1038	Each aio request uses - depending on your architecture - around 100-200
		1039	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1040	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1041	scalars and other data passed into aio requests will also be locked and
		1042	will consume memory till the request has entered the done state.
		1043
		1044	This is now awfully much, so queuing lots of requests is not usually a
		1045	problem.
		1046
		1047	Per-thread usage:
		1048
		1049	In the execution phase, some aio requests require more memory for
		1050	temporary buffers, and each thread requires a stack and other data
		1051	structures (usually around 16k-128k, depending on the OS).
		1052
		1053	=head1 KNOWN BUGS
		1054
		1055	Known bugs will be fixed in the next release.
		1056
546	=head1 SEE ALSO	1057	=head1 SEE ALSO
547		1058
548	L<Coro>, L<Linux::AIO>.	1059	L<Coro::AIO>.
549		1060
550	=head1 AUTHOR	1061	=head1 AUTHOR
551		1062
552	Marc Lehmann <schmorp@schmorp.de>	1063	Marc Lehmann <schmorp@schmorp.de>
553	http://home.schmorp.de/	1064	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.46 by root, Mon Dec 26 20:17:13 2005 UTC vs. Revision 1.85 by root, Sat Oct 28 01:40:30 2006 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.46 by root, Mon Dec 26 20:17:13 2005 UTC vs.
Revision 1.85 by root, Sat Oct 28 01:40:30 2006 UTC