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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.44 by root, Mon Dec 26 18:31:12 2005 UTC vs.
Revision 1.82 by root, Fri Oct 27 20:10:06 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
47	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
48	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
49	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
50	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
51	aio functions available on many operating systems. However, they are often	60	functions available on many operating systems. However, they are often
52	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
53	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
54	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.
55		65
56	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-)
57	currently not reentrant, so use appropriate locking yourself, always call	67	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	68	locking yourself, always call C<poll_cb> from within the same thread, or
59	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).
60		120
61	=cut	121	=cut
62		122
63	package IO::AIO;	123	package IO::AIO;
64		124
65	no warnings;	125	no warnings;
		126	use strict 'vars';
66		127
67	use base 'Exporter';	128	use base 'Exporter';
68		129
69	use Fcntl ();
70
71	BEGIN {	130	BEGIN {
72	$VERSION = '1.7';	131	our $VERSION = '2.0';
73		132
74	@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
75	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	134	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
76	aio_fsync aio_fdatasync aio_readahead);	135	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
77	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	136	aio_copy aio_group aio_nop aio_mknod);
78	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 nreqs nready npending);
		140
		141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
79		142
80	require XSLoader;	143	require XSLoader;
81	XSLoader::load IO::AIO, $VERSION;	144	XSLoader::load ("IO::AIO", $VERSION);
82	}	145	}
83		146
84	=head1 FUNCTIONS	147	=head1 FUNCTIONS
85		148
86	=head2 AIO FUNCTIONS	149	=head2 AIO FUNCTIONS
…		…
94	syscall has been executed asynchronously.	157	syscall has been executed asynchronously.
95		158
96	All functions expecting a filehandle keep a copy of the filehandle	159	All functions expecting a filehandle keep a copy of the filehandle
97	internally until the request has finished.	160	internally until the request has finished.
98		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
99	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
100	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
101	request is being executed, the current working directory could have	167	request is being executed, the current working directory could have
102	changed. Alternatively, you can make sure that you never change the	168	changed. Alternatively, you can make sure that you never change the
103	current working directory.	169	current working directory.
…		…
108	your pathnames to the locale (or other) encoding in effect in the user	174	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)	175	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
110	use something else.	176	use something else.
111		177
112	=over 4	178	=over 4
		179
		180	=item $prev_pri = aioreq_pri [$pri]
		181
		182	Returns the priority value that would be used for the next request and, if
		183	C<$pri> is given, sets the priority for the next aio request.
		184
		185	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		186	and C<4>, respectively. Requests with higher priority will be serviced
		187	first.
		188
		189	The priority will be reset to C<0> after each call to one of the C<aio_*>
		190	functions.
		191
		192	Example: open a file with low priority, then read something from it with
		193	higher priority so the read request is serviced before other low priority
		194	open requests (potentially spamming the cache):
		195
		196	aioreq_pri -3;
		197	aio_open ..., sub {
		198	return unless $_[0];
		199
		200	aioreq_pri -2;
		201	aio_read $_[0], ..., sub {
		202	...
		203	};
		204	};
		205
		206	=item aioreq_nice $pri_adjust
		207
		208	Similar to C<aioreq_pri>, but subtracts the given value from the current
		209	priority, so effects are cumulative.
113		210
114	=item aio_open $pathname, $flags, $mode, $callback->($fh)	211	=item aio_open $pathname, $flags, $mode, $callback->($fh)
115		212
116	Asynchronously open or create a file and call the callback with a newly	213	Asynchronously open or create a file and call the callback with a newly
117	created filehandle for the file.	214	created filehandle for the file.
…		…
232	=item aio_unlink $pathname, $callback->($status)	329	=item aio_unlink $pathname, $callback->($status)
233		330
234	Asynchronously unlink (delete) a file and call the callback with the	331	Asynchronously unlink (delete) a file and call the callback with the
235	result code.	332	result code.
236		333
		334	=item aio_mknod $path, $mode, $dev, $callback->($status)
		335
		336	Asynchronously create a device node (or fifo). See mknod(2): the only
		337	portable value for C<$mode> is C<S_IFIFO> ored with permissions, and C<0>
		338	for C<$dev>.
		339
		340	=item aio_link $srcpath, $dstpath, $callback->($status)
		341
		342	Asynchronously create a new link to the existing object at C<$srcpath> at
		343	the path C<$dstpath> and call the callback with the result code.
		344
		345	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		346
		347	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		348	the path C<$dstpath> and call the callback with the result code.
		349
		350	=item aio_rename $srcpath, $dstpath, $callback->($status)
		351
		352	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		353	rename(2) and call the callback with the result code.
		354
237	=item aio_rmdir $pathname, $callback->($status)	355	=item aio_rmdir $pathname, $callback->($status)
238		356
239	Asynchronously rmdir (delete) a directory and call the callback with the	357	Asynchronously rmdir (delete) a directory and call the callback with the
240	result code.	358	result code.
241		359
242	=item aio_readdir $pathname $callback->($entries)	360	=item aio_readdir $pathname, $callback->($entries)
243		361
244	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	362	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
245	directory (i.e. opendir + readdir + closedir). The entries will not be	363	directory (i.e. opendir + readdir + closedir). The entries will not be
246	sorted, and will B<NOT> include the C<.> and C<..> entries.	364	sorted, and will B<NOT> include the C<.> and C<..> entries.
247		365
248	The callback a single argument which is either C<undef> or an array-ref	366	The callback a single argument which is either C<undef> or an array-ref
249	with the filenames.	367	with the filenames.
250		368
		369	=item aio_copy $srcpath, $dstpath, $callback->($status)
		370
		371	Try to copy the I<file> (directories not supported as either source or
		372	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		373	the C<0> (error) or C<-1> ok.
		374
		375	This is a composite request that it creates the destination file with
		376	mode 0200 and copies the contents of the source file into it using
		377	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		378	uid/gid, in that order.
		379
		380	If an error occurs, the partial destination file will be unlinked, if
		381	possible, except when setting atime, mtime, access mode and uid/gid, where
		382	errors are being ignored.
		383
		384	=cut
		385
		386	sub aio_copy($$;$) {
		387	my ($src, $dst, $cb) = @_;
		388
		389	my $pri = aioreq_pri;
		390	my $grp = aio_group $cb;
		391
		392	aioreq_pri $pri;
		393	add $grp aio_open $src, O_RDONLY, 0, sub {
		394	if (my $src_fh = $_[0]) {
		395	my @stat = stat $src_fh;
		396
		397	aioreq_pri $pri;
		398	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		399	if (my $dst_fh = $_[0]) {
		400	aioreq_pri $pri;
		401	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		402	if ($_[0] == $stat[7]) {
		403	$grp->result (0);
		404	close $src_fh;
		405
		406	# those should not normally block. should. should.
		407	utime $stat[8], $stat[9], $dst;
		408	chmod $stat[2] & 07777, $dst_fh;
		409	chown $stat[4], $stat[5], $dst_fh;
		410	close $dst_fh;
		411	} else {
		412	$grp->result (-1);
		413	close $src_fh;
		414	close $dst_fh;
		415
		416	aioreq $pri;
		417	add $grp aio_unlink $dst;
		418	}
		419	};
		420	} else {
		421	$grp->result (-1);
		422	}
		423	},
		424
		425	} else {
		426	$grp->result (-1);
		427	}
		428	};
		429
		430	$grp
		431	}
		432
		433	=item aio_move $srcpath, $dstpath, $callback->($status)
		434
		435	Try to move the I<file> (directories not supported as either source or
		436	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		437	the C<0> (error) or C<-1> ok.
		438
		439	This is a composite request that tries to rename(2) the file first. If
		440	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		441	that is successful, unlinking the C<$srcpath>.
		442
		443	=cut
		444
		445	sub aio_move($$;$) {
		446	my ($src, $dst, $cb) = @_;
		447
		448	my $pri = aioreq_pri;
		449	my $grp = aio_group $cb;
		450
		451	aioreq_pri $pri;
		452	add $grp aio_rename $src, $dst, sub {
		453	if ($_[0] && $! == EXDEV) {
		454	aioreq_pri $pri;
		455	add $grp aio_copy $src, $dst, sub {
		456	$grp->result ($_[0]);
		457
		458	if (!$_[0]) {
		459	aioreq_pri $pri;
		460	add $grp aio_unlink $src;
		461	}
		462	};
		463	} else {
		464	$grp->result ($_[0]);
		465	}
		466	};
		467
		468	$grp
		469	}
		470
251	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	471	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
252		472
253	Scans a directory (similar to C<aio_readdir>) and tries to separate the	473	Scans a directory (similar to C<aio_readdir>) but additionally tries to
254	entries of directory C<$path> into two sets of names, ones you can recurse	474	efficiently separate the entries of directory C<$path> into two sets of
255	into (directories), and ones you cannot recurse into (everything else).	475	names, directories you can recurse into (directories), and ones you cannot
		476	recurse into (everything else, including symlinks to directories).
256		477
257	C<aio_scandir> is a composite request that consists of many	478	C<aio_scandir> is a composite request that creates of many sub requests_
258	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	479	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	480	this function generates. If it is C<< <= 0 >>, then a suitable default
260	suitable default will be chosen (currently 8).	481	will be chosen (currently 4).
261		482
262	On error, the callback is called without arguments, otherwise it receives	483	On error, the callback is called without arguments, otherwise it receives
263	two array-refs with path-relative entry names.	484	two array-refs with path-relative entry names.
264		485
265	Example:	486	Example:
…		…
273	Implementation notes.	494	Implementation notes.
274		495
275	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	496	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
276		497
277	After reading the directory, the modification time, size etc. of the	498	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	499	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	500	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	501	entries are directories (if >= 2). Otherwise, no knowledge of the number
281	assumed.	502	of subdirectories will be assumed.
282		503
283	Then entires will be sorted into likely directories (everything without a	504	Then entries will be sorted into likely directories (everything without
284	non-initial dot) and likely non-directories (everything else). Then every	505	a non-initial dot currently) and likely non-directories (everything
285	entry + C</.> will be C<stat>'ed, likely directories first. This is often	506	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		507	likely directories first. If that succeeds, it assumes that the entry
		508	is a directory or a symlink to directory (which will be checked
		509	seperately). This is often faster than stat'ing the entry itself because
286	faster because filesystems might detect the type of the entry without	510	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,	511	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		512
291	If the known number of directories has been reached, the rest of the	513	If the known number of directories (link count - 2) has been reached, the
292	entries is assumed to be non-directories.	514	rest of the entries is assumed to be non-directories.
		515
		516	This only works with certainty on POSIX (= UNIX) filesystems, which
		517	fortunately are the vast majority of filesystems around.
		518
		519	It will also likely work on non-POSIX filesystems with reduced efficiency
		520	as those tend to return 0 or 1 as link counts, which disables the
		521	directory counting heuristic.
293		522
294	=cut	523	=cut
295		524
296	sub aio_scandir($$$) {	525	sub aio_scandir($$$) {
297	my ($path, $maxreq, $cb) = @_;	526	my ($path, $maxreq, $cb) = @_;
298		527
		528	my $pri = aioreq_pri;
		529
		530	my $grp = aio_group $cb;
		531
299	$maxreq = 8 if $maxreq <= 0;	532	$maxreq = 4 if $maxreq <= 0;
300		533
301	# stat once	534	# stat once
		535	aioreq_pri $pri;
302	aio_stat $path, sub {	536	add $grp aio_stat $path, sub {
303	$cb->() if $_[0];	537	return $grp->result () if $_[0];
		538	my $now = time;
304	my $hash1 = join ":", (stat _)[0,1,3,7,9];	539	my $hash1 = join ":", (stat _)[0,1,3,7,9];
305		540
306	# read the directory entries	541	# read the directory entries
		542	aioreq_pri $pri;
307	aio_readdir $path, sub {	543	add $grp aio_readdir $path, sub {
308	my $entries = shift	544	my $entries = shift
309	or return $cb->();	545	or return $grp->result ();
310		546
311	# stat the dir another time	547	# stat the dir another time
		548	aioreq_pri $pri;
312	aio_stat $path, sub {	549	add $grp aio_stat $path, sub {
313	my $hash2 = join ":", (stat _)[0,1,3,7,9];	550	my $hash2 = join ":", (stat _)[0,1,3,7,9];
314		551
315	my $ndirs;	552	my $ndirs;
316		553
317	# take the slow route if anything looks fishy	554	# take the slow route if anything looks fishy
318	if ($hash1 ne $hash2) {	555	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
319	$ndirs = -1;	556	$ndirs = -1;
320	} else {	557	} else {
321	# if nlink == 2, we are finished	558	# if nlink == 2, we are finished
322	# on non-posix-fs's, we rely on nlink < 2	559	# on non-posix-fs's, we rely on nlink < 2
323	$ndirs = (stat _)[3] - 2	560	$ndirs = (stat _)[3] - 2
324	or return $cb->([], $entries);	561	or return $grp->result ([], $entries);
325	}	562	}
326		563
327	# sort into likely dirs and likely nondirs	564	# sort into likely dirs and likely nondirs
328	# dirs == files without ".", short entries first	565	# dirs == files without ".", short entries first
329	$entries = [map $_->[0],	566	$entries = [map $_->[0],
…		…
331	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	568	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
332	@$entries];	569	@$entries];
333		570
334	my (@dirs, @nondirs);	571	my (@dirs, @nondirs);
335		572
336	my ($statcb, $schedcb);	573	my $statgrp = add $grp aio_group sub {
337	my $nreq = 0;	574	$grp->result (\@dirs, \@nondirs);
		575	};
338		576
339	$schedcb = sub {	577	limit $statgrp $maxreq;
340	if (@$entries) {	578	feed $statgrp sub {
341	if ($nreq < $maxreq) {	579	return unless @$entries;
342	my $ent = pop @$entries;	580	my $entry = pop @$entries;
		581
		582	aioreq_pri $pri;
		583	add $statgrp aio_stat "$path/$entry/.", sub {
		584	if ($_[0] < 0) {
		585	push @nondirs, $entry;
		586	} else {
		587	# need to check for real directory
		588	aioreq_pri $pri;
		589	add $statgrp aio_lstat "$path/$entry", sub {
		590	if (-d _) {
		591	push @dirs, $entry;
		592
		593	unless (--$ndirs) {
		594	push @nondirs, @$entries;
		595	feed $statgrp;
		596	}
		597	} else {
		598	push @nondirs, $entry;
		599	}
343	$nreq++;	600	}
344	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
345	}	601	}
346	} elsif (!$nreq) {
347	# finished
348	undef $statcb;
349	undef $schedcb;
350	$cb->(\@dirs, \@nondirs);
351	undef $cb;
352	}	602	};
353	};	603	};
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	};	604	};
384	};	605	};
385	};	606	};
		607
		608	$grp
386	}	609	}
387		610
388	=item aio_fsync $fh, $callback->($status)	611	=item aio_fsync $fh, $callback->($status)
389		612
390	Asynchronously call fsync on the given filehandle and call the callback	613	Asynchronously call fsync on the given filehandle and call the callback
…		…
395	Asynchronously call fdatasync on the given filehandle and call the	618	Asynchronously call fdatasync on the given filehandle and call the
396	callback with the fdatasync result code.	619	callback with the fdatasync result code.
397		620
398	If this call isn't available because your OS lacks it or it couldn't be	621	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.	622	detected, it will be emulated by calling C<fsync> instead.
		623
		624	=item aio_group $callback->(...)
		625
		626	This is a very special aio request: Instead of doing something, it is a
		627	container for other aio requests, which is useful if you want to bundle
		628	many requests into a single, composite, request with a definite callback
		629	and the ability to cancel the whole request with its subrequests.
		630
		631	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		632	for more info.
		633
		634	Example:
		635
		636	my $grp = aio_group sub {
		637	print "all stats done\n";
		638	};
		639
		640	add $grp
		641	(aio_stat ...),
		642	(aio_stat ...),
		643	...;
		644
		645	=item aio_nop $callback->()
		646
		647	This is a special request - it does nothing in itself and is only used for
		648	side effects, such as when you want to add a dummy request to a group so
		649	that finishing the requests in the group depends on executing the given
		650	code.
		651
		652	While this request does nothing, it still goes through the execution
		653	phase and still requires a worker thread. Thus, the callback will not
		654	be executed immediately but only after other requests in the queue have
		655	entered their execution phase. This can be used to measure request
		656	latency.
		657
		658	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		659
		660	Mainly used for debugging and benchmarking, this aio request puts one of
		661	the request workers to sleep for the given time.
		662
		663	While it is theoretically handy to have simple I/O scheduling requests
		664	like sleep and file handle readable/writable, the overhead this creates is
		665	immense (it blocks a thread for a long time) so do not use this function
		666	except to put your application under artificial I/O pressure.
		667
		668	=back
		669
		670	=head2 IO::AIO::REQ CLASS
		671
		672	All non-aggregate C<aio_*> functions return an object of this class when
		673	called in non-void context.
		674
		675	=over 4
		676
		677	=item cancel $req
		678
		679	Cancels the request, if possible. Has the effect of skipping execution
		680	when entering the B<execute> state and skipping calling the callback when
		681	entering the the B<result> state, but will leave the request otherwise
		682	untouched. That means that requests that currently execute will not be
		683	stopped and resources held by the request will not be freed prematurely.
		684
		685	=item cb $req $callback->(...)
		686
		687	Replace (or simply set) the callback registered to the request.
		688
		689	=back
		690
		691	=head2 IO::AIO::GRP CLASS
		692
		693	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		694	objects of this class, too.
		695
		696	A IO::AIO::GRP object is a special request that can contain multiple other
		697	aio requests.
		698
		699	You create one by calling the C<aio_group> constructing function with a
		700	callback that will be called when all contained requests have entered the
		701	C<done> state:
		702
		703	my $grp = aio_group sub {
		704	print "all requests are done\n";
		705	};
		706
		707	You add requests by calling the C<add> method with one or more
		708	C<IO::AIO::REQ> objects:
		709
		710	$grp->add (aio_unlink "...");
		711
		712	add $grp aio_stat "...", sub {
		713	$_[0] or return $grp->result ("error");
		714
		715	# add another request dynamically, if first succeeded
		716	add $grp aio_open "...", sub {
		717	$grp->result ("ok");
		718	};
		719	};
		720
		721	This makes it very easy to create composite requests (see the source of
		722	C<aio_move> for an application) that work and feel like simple requests.
		723
		724	=over 4
		725
		726	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		727	C<IO::AIO::poll_cb>, just like any other request.
		728
		729	=item * They can be canceled like any other request. Canceling will cancel not
		730	only the request itself, but also all requests it contains.
		731
		732	=item * They can also can also be added to other IO::AIO::GRP objects.
		733
		734	=item * You must not add requests to a group from within the group callback (or
		735	any later time).
		736
		737	=back
		738
		739	Their lifetime, simplified, looks like this: when they are empty, they
		740	will finish very quickly. If they contain only requests that are in the
		741	C<done> state, they will also finish. Otherwise they will continue to
		742	exist.
		743
		744	That means after creating a group you have some time to add requests. And
		745	in the callbacks of those requests, you can add further requests to the
		746	group. And only when all those requests have finished will the the group
		747	itself finish.
		748
		749	=over 4
		750
		751	=item add $grp ...
		752
		753	=item $grp->add (...)
		754
		755	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		756	be added, including other groups, as long as you do not create circular
		757	dependencies.
		758
		759	Returns all its arguments.
		760
		761	=item $grp->cancel_subs
		762
		763	Cancel all subrequests and clears any feeder, but not the group request
		764	itself. Useful when you queued a lot of events but got a result early.
		765
		766	=item $grp->result (...)
		767
		768	Set the result value(s) that will be passed to the group callback when all
		769	subrequests have finished and set thre groups errno to the current value
		770	of errno (just like calling C<errno> without an error number). By default,
		771	no argument will be passed and errno is zero.
		772
		773	=item $grp->errno ([$errno])
		774
		775	Sets the group errno value to C<$errno>, or the current value of errno
		776	when the argument is missing.
		777
		778	Every aio request has an associated errno value that is restored when
		779	the callback is invoked. This method lets you change this value from its
		780	default (0).
		781
		782	Calling C<result> will also set errno, so make sure you either set C<$!>
		783	before the call to C<result>, or call c<errno> after it.
		784
		785	=item feed $grp $callback->($grp)
		786
		787	Sets a feeder/generator on this group: every group can have an attached
		788	generator that generates requests if idle. The idea behind this is that,
		789	although you could just queue as many requests as you want in a group,
		790	this might starve other requests for a potentially long time. For
		791	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		792	requests, delaying any later requests for a long time.
		793
		794	To avoid this, and allow incremental generation of requests, you can
		795	instead a group and set a feeder on it that generates those requests. The
		796	feed callback will be called whenever there are few enough (see C<limit>,
		797	below) requests active in the group itself and is expected to queue more
		798	requests.
		799
		800	The feed callback can queue as many requests as it likes (i.e. C<add> does
		801	not impose any limits).
		802
		803	If the feed does not queue more requests when called, it will be
		804	automatically removed from the group.
		805
		806	If the feed limit is C<0>, it will be set to C<2> automatically.
		807
		808	Example:
		809
		810	# stat all files in @files, but only ever use four aio requests concurrently:
		811
		812	my $grp = aio_group sub { print "finished\n" };
		813	limit $grp 4;
		814	feed $grp sub {
		815	my $file = pop @files
		816	or return;
		817
		818	add $grp aio_stat $file, sub { ... };
		819	};
		820
		821	=item limit $grp $num
		822
		823	Sets the feeder limit for the group: The feeder will be called whenever
		824	the group contains less than this many requests.
		825
		826	Setting the limit to C<0> will pause the feeding process.
400		827
401	=back	828	=back
402		829
403	=head2 SUPPORT FUNCTIONS	830	=head2 SUPPORT FUNCTIONS
404		831
…		…
417		844
418	Process all outstanding events on the result pipe. You have to call this	845	Process all outstanding events on the result pipe. You have to call this
419	regularly. Returns the number of events processed. Returns immediately	846	regularly. Returns the number of events processed. Returns immediately
420	when no events are outstanding.	847	when no events are outstanding.
421		848
		849	If not all requests were processed for whatever reason, the filehandle
		850	will still be ready when C<poll_cb> returns.
		851
422	Example: Install an Event watcher that automatically calls	852	Example: Install an Event watcher that automatically calls
423	IO::AIO::poll_cb with high priority:	853	IO::AIO::poll_cb with high priority:
424		854
425	Event->io (fd => IO::AIO::poll_fileno,	855	Event->io (fd => IO::AIO::poll_fileno,
426	poll => 'r', async => 1,	856	poll => 'r', async => 1,
427	cb => \&IO::AIO::poll_cb);	857	cb => \&IO::AIO::poll_cb);
428		858
		859	=item IO::AIO::poll_some $max_requests
		860
		861	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests
		862	at a time.
		863
		864	Useful if you want to ensure some level of interactiveness when perl is
		865	not fast enough to process all requests in time.
		866
		867	Example: Install an Event watcher that automatically calls
		868	IO::AIO::poll_some with low priority, to ensure that other parts of the
		869	program get the CPU sometimes even under high AIO load.
		870
		871	Event->io (fd => IO::AIO::poll_fileno,
		872	poll => 'r', nice => 1,
		873	cb => sub { IO::AIO::poll_some 256 });
		874
429	=item IO::AIO::poll_wait	875	=item IO::AIO::poll_wait
430		876
431	Wait till the result filehandle becomes ready for reading (simply does a	877	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	878	C<select> on the filehandle. This is useful if you want to synchronously wait
433	for some requests to finish).	879	for some requests to finish).
434		880
435	See C<nreqs> for an example.	881	See C<nreqs> for an example.
436		882
437	=item IO::AIO::nreqs	883	=item IO::AIO::nreqs
438		884
439	Returns the number of requests currently outstanding (i.e. for which their	885	Returns the number of requests currently in the ready, execute or pending
440	callback has not been invoked yet).	886	states (i.e. for which their callback has not been invoked yet).
441		887
442	Example: wait till there are no outstanding requests anymore:	888	Example: wait till there are no outstanding requests anymore:
443		889
444	IO::AIO::poll_wait, IO::AIO::poll_cb	890	IO::AIO::poll_wait, IO::AIO::poll_cb
445	while IO::AIO::nreqs;	891	while IO::AIO::nreqs;
446		892
		893	=item IO::AIO::nready
		894
		895	Returns the number of requests currently in the ready state (not yet
		896	executed).
		897
		898	=item IO::AIO::npending
		899
		900	Returns the number of requests currently in the pending state (executed,
		901	but not yet processed by poll_cb).
		902
447	=item IO::AIO::flush	903	=item IO::AIO::flush
448		904
449	Wait till all outstanding AIO requests have been handled.	905	Wait till all outstanding AIO requests have been handled.
450		906
451	Strictly equivalent to:	907	Strictly equivalent to:
…		…
462	IO::AIO::poll_wait, IO::AIO::poll_cb	918	IO::AIO::poll_wait, IO::AIO::poll_cb
463	if IO::AIO::nreqs;	919	if IO::AIO::nreqs;
464		920
465	=item IO::AIO::min_parallel $nthreads	921	=item IO::AIO::min_parallel $nthreads
466		922
467	Set the minimum number of AIO threads to C<$nthreads>. The current default	923	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	924	default is C<8>, which means eight asynchronous operations can execute
469	(the number of outstanding operations, however, is unlimited).	925	concurrently at any one time (the number of outstanding requests,
		926	however, is unlimited).
470		927
471	IO::AIO starts threads only on demand, when an AIO request is queued and	928	IO::AIO starts threads only on demand, when an AIO request is queued and
472	no free thread exists.	929	no free thread exists.
473		930
474	It is recommended to keep the number of threads low, as some Linux	931	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	932	Linux kernel versions will scale negatively with the number of threads
476	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	933	(higher parallelity => MUCH higher latency). With current Linux 2.6
477	threads should be fine.	934	versions, 4-32 threads should be fine.
478		935
479	Under most circumstances you don't need to call this function, as the	936	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.	937	module selects a default that is suitable for low to moderate load.
481		938
482	=item IO::AIO::max_parallel $nthreads	939	=item IO::AIO::max_parallel $nthreads
…		…
491	This module automatically runs C<max_parallel 0> at program end, to ensure	948	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.	949	that all threads are killed and that there are no outstanding requests.
493		950
494	Under normal circumstances you don't need to call this function.	951	Under normal circumstances you don't need to call this function.
495		952
496	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	953	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		954
		955	This is a very bad function to use in interactive programs because it
		956	blocks, and a bad way to reduce concurrency because it is inexact: Better
		957	use an C<aio_group> together with a feed callback.
497		958
498	Sets the maximum number of outstanding requests to C<$nreqs>. If you	959	Sets the maximum number of outstanding requests to C<$nreqs>. If you
499	try to queue up more than this number of requests, the caller will block until	960	to queue up more than this number of requests, the next call to the
500	some requests have been handled.	961	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		962	function will block until the limit is no longer exceeded.
501		963
502	The default is very large, so normally there is no practical limit. If you	964	The default value is very large, so there is no practical limit on the
503	queue up many requests in a loop it often improves speed if you set	965	number of outstanding requests.
504	this to a relatively low number, such as C<100>.
505		966
506	Under normal circumstances you don't need to call this function.	967	You can still queue as many requests as you want. Therefore,
		968	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		969	as a stop gap to shield against fatal memory overflow (with large values).
507		970
508	=back	971	=back
509		972
510	=cut	973	=cut
511		974
…		…
523	or return undef;	986	or return undef;
524		987
525	*$sym	988	*$sym
526	}	989	}
527		990
528	min_parallel 4;	991	min_parallel 8;
529		992
530	END {	993	END {
531	max_parallel 0;	994	flush;
532	}	995	};
533		996
534	1;	997	1;
535		998
536	=head2 FORK BEHAVIOUR	999	=head2 FORK BEHAVIOUR
		1000
		1001	This module should do "the right thing" when the process using it forks:
537		1002
538	Before the fork, IO::AIO enters a quiescent state where no requests	1003	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	1004	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	1005	the fork the parent simply leaves the quiescent state and continues
541	request/result processing, while the child clears the request/result	1006	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	1007	(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	1008	parent). Threads will be started on demand until the limit set in the
544	parent process has been reached again.	1009	parent process has been reached again.
545		1010
		1011	In short: the parent will, after a short pause, continue as if fork had
		1012	not been called, while the child will act as if IO::AIO has not been used
		1013	yet.
		1014
		1015	=head2 MEMORY USAGE
		1016
		1017	Per-request usage:
		1018
		1019	Each aio request uses - depending on your architecture - around 100-200
		1020	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1021	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1022	scalars and other data passed into aio requests will also be locked and
		1023	will consume memory till the request has entered the done state.
		1024
		1025	This is now awfully much, so queuing lots of requests is not usually a
		1026	problem.
		1027
		1028	Per-thread usage:
		1029
		1030	In the execution phase, some aio requests require more memory for
		1031	temporary buffers, and each thread requires a stack and other data
		1032	structures (usually around 16k-128k, depending on the OS).
		1033
		1034	=head1 KNOWN BUGS
		1035
		1036	Known bugs will be fixed in the next release.
		1037
546	=head1 SEE ALSO	1038	=head1 SEE ALSO
547		1039
548	L<Coro>, L<Linux::AIO>.	1040	L<Coro::AIO>.
549		1041
550	=head1 AUTHOR	1042	=head1 AUTHOR
551		1043
552	Marc Lehmann <schmorp@schmorp.de>	1044	Marc Lehmann <schmorp@schmorp.de>
553	http://home.schmorp.de/	1045	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.44 by root, Mon Dec 26 18:31:12 2005 UTC vs. Revision 1.82 by root, Fri Oct 27 20:10:06 2006 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.44 by root, Mon Dec 26 18:31:12 2005 UTC vs.
Revision 1.82 by root, Fri Oct 27 20:10:06 2006 UTC