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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.42 by root, Mon Dec 26 18:15:23 2005 UTC vs.
Revision 1.77 by root, Wed Oct 25 17:57:30 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
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 = '1.61';	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_group aio_nop);
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);
		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 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.
113		207
114	=item aio_open $pathname, $flags, $mode, $callback->($fh)	208	=item aio_open $pathname, $flags, $mode, $callback->($fh)
115		209
116	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
117	created filehandle for the file.	211	created filehandle for the file.
…		…
167		261
168	aio_read $fh, 7, 15, $buffer, 0, sub {	262	aio_read $fh, 7, 15, $buffer, 0, sub {
169	$_[0] > 0 or die "read error: $!";	263	$_[0] > 0 or die "read error: $!";
170	print "read $_[0] bytes: <$buffer>\n";	264	print "read $_[0] bytes: <$buffer>\n";
171	};	265	};
		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	}
172		334
173	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	335	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
174		336
175	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
176	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
…		…
232	=item aio_unlink $pathname, $callback->($status)	394	=item aio_unlink $pathname, $callback->($status)
233		395
234	Asynchronously unlink (delete) a file and call the callback with the	396	Asynchronously unlink (delete) a file and call the callback with the
235	result code.	397	result code.
236		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
237	=item aio_rmdir $pathname, $callback->($status)	414	=item aio_rmdir $pathname, $callback->($status)
238		415
239	Asynchronously rmdir (delete) a directory and call the callback with the	416	Asynchronously rmdir (delete) a directory and call the callback with the
240	result code.	417	result code.
241		418
242	=item aio_readdir $pathname $callback->($entries)	419	=item aio_readdir $pathname, $callback->($entries)
243		420
244	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
245	directory (i.e. opendir + readdir + closedir). The entries will not be	422	directory (i.e. opendir + readdir + closedir). The entries will not be
246	sorted, and will B<NOT> include the C<.> and C<..> entries.	423	sorted, and will B<NOT> include the C<.> and C<..> entries.
247		424
248	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
249	with the filenames.	426	with the filenames.
250		427
251	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	428	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
252		429
253	Scans a directory (similar to C<aio_readdir>) and tries to separate the	430	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	431	efficiently separate the entries of directory C<$path> into two sets of
255	into (directories), and ones you cannot recurse into (everything else).	432	names, directories you can recurse into (directories), and ones you cannot
		433	recurse into (everything else, including symlinks to directories).
256		434
257	C<aio_scandir> is a composite request that consists of many	435	C<aio_scandir> is a composite request that creates of many sub requests_
258	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	436	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	437	this function generates. If it is C<< <= 0 >>, then a suitable default
260	suitable default will be chosen (currently 8).	438	will be chosen (currently 6).
261		439
262	On error, the callback is called without arguments, otherwise it receives	440	On error, the callback is called without arguments, otherwise it receives
263	two array-refs with path-relative entry names.	441	two array-refs with path-relative entry names.
264		442
265	Example:	443	Example:
…		…
273	Implementation notes.	451	Implementation notes.
274		452
275	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	453	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
276		454
277	After reading the directory, the modification time, size etc. of the	455	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	456	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	457	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	458	entries are directories (if >= 2). Otherwise, no knowledge of the number
281	assumed.	459	of subdirectories will be assumed.
282		460
283	Then entires will be sorted into likely directories (everything without a	461	Then entries will be sorted into likely directories (everything without
284	non-initial dot) and likely non-directories (everything else). Then every	462	a non-initial dot currently) and likely non-directories (everything
285	entry + C</.> will be C<stat>'ed, likely directories first. This is often	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
286	faster because filesystems might detect the type of the entry without	467	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,	468	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		469
291	If the known number of directories has been reached, the rest of the	470	If the known number of directories (link count - 2) has been reached, the
292	entries is assumed to be non-directories.	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.
293		479
294	=cut	480	=cut
295		481
296	sub aio_scandir($$$) {	482	sub aio_scandir($$$) {
297	my ($path, $maxreq, $cb) = @_;	483	my ($path, $maxreq, $cb) = @_;
298		484
		485	my $grp = aio_group $cb;
		486
299	$maxreq = 8 if $maxreq <= 0;	487	$maxreq = 6 if $maxreq <= 0;
300		488
301	# stat once	489	# stat once
302	aio_stat $path, sub {	490	add $grp aio_stat $path, sub {
303	$cb->() if $_[0];	491	return $grp->result () if $_[0];
		492	my $now = time;
304	my $hash1 = join ":", (stat _)[0,1,3,7,9];	493	my $hash1 = join ":", (stat _)[0,1,3,7,9];
305		494
306	# read the directory entries	495	# read the directory entries
307	aio_readdir $path, sub {	496	add $grp aio_readdir $path, sub {
308	my $entries = shift	497	my $entries = shift
309	or return $cb->();	498	or return $grp->result ();
310		499
311	# stat the dir another time	500	# stat the dir another time
312	aio_stat $path, sub {	501	add $grp aio_stat $path, sub {
313	my $hash2 = join ":", (stat _)[0,1,3,7,9];	502	my $hash2 = join ":", (stat _)[0,1,3,7,9];
314		503
315	my $ndirs;	504	my $ndirs;
316		505
317	# take the slow route if anything looks fishy	506	# take the slow route if anything looks fishy
318	if ($hash1 ne $hash2) {	507	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
319	$ndirs = -1;	508	$ndirs = -1;
320	} else {	509	} else {
321	# if nlink == 2, we are finished	510	# if nlink == 2, we are finished
322	# on non-posix-fs's, we rely on nlink < 2	511	# on non-posix-fs's, we rely on nlink < 2
323	$ndirs = (stat _)[3] - 2	512	$ndirs = (stat _)[3] - 2
324	or $cb->([], $entries);	513	or return $grp->result ([], $entries);
325	}	514	}
326		515
327	# sort into likely dirs and likely nondirs	516	# sort into likely dirs and likely nondirs
328	# dirs == files without ".", short entries first	517	# dirs == files without ".", short entries first
329	$entries = [map $_->[0],	518	$entries = [map $_->[0],
…		…
331	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	520	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
332	@$entries];	521	@$entries];
333		522
334	my (@dirs, @nondirs);	523	my (@dirs, @nondirs);
335		524
336	my ($statcb, $schedcb);	525	my $statgrp = add $grp aio_group sub {
337	my $nreq = 0;	526	$grp->result (\@dirs, \@nondirs);
		527	};
338		528
339	$schedcb = sub {	529	limit $statgrp $maxreq;
340	if (@$entries) {	530	feed $statgrp sub {
341	if ($nreq < $maxreq) {	531	return unless @$entries;
342	my $ent = pop @$entries;	532	my $entry = pop @$entries;
		533
		534	add $statgrp aio_stat "$path/$entry/.", sub {
		535	if ($_[0] < 0) {
		536	push @nondirs, $entry;
		537	} else {
		538	# need to check for real directory
		539	add $statgrp aio_lstat "$path/$entry", sub {
		540	if (-d _) {
		541	push @dirs, $entry;
		542
		543	unless (--$ndirs) {
		544	push @nondirs, @$entries;
		545	feed $statgrp;
		546	}
		547	} else {
		548	push @nondirs, $entry;
		549	}
343	$nreq++;	550	}
344	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
345	}	551	}
346	} elsif (!$nreq) {
347	# finished
348	undef $statcb;
349	undef $schedcb;
350	$cb->(\@dirs, \@nondirs);
351	undef $cb;
352	}	552	};
353	};	553	};
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	};	554	};
384	};	555	};
385	};	556	};
		557
		558	$grp
386	}	559	}
387		560
388	=item aio_fsync $fh, $callback->($status)	561	=item aio_fsync $fh, $callback->($status)
389		562
390	Asynchronously call fsync on the given filehandle and call the callback	563	Asynchronously call fsync on the given filehandle and call the callback
…		…
395	Asynchronously call fdatasync on the given filehandle and call the	568	Asynchronously call fdatasync on the given filehandle and call the
396	callback with the fdatasync result code.	569	callback with the fdatasync result code.
397		570
398	If this call isn't available because your OS lacks it or it couldn't be	571	If this call isn't available because your OS lacks it or it couldn't be
399	detected, it will be emulated by calling C<fsync> instead.	572	detected, it will be emulated by calling C<fsync> instead.
		573
		574	=item aio_group $callback->(...)
		575
		576	This is a very special aio request: Instead of doing something, it is a
		577	container for other aio requests, which is useful if you want to bundle
		578	many requests into a single, composite, request with a definite callback
		579	and the ability to cancel the whole request with its subrequests.
		580
		581	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		582	for more info.
		583
		584	Example:
		585
		586	my $grp = aio_group sub {
		587	print "all stats done\n";
		588	};
		589
		590	add $grp
		591	(aio_stat ...),
		592	(aio_stat ...),
		593	...;
		594
		595	=item aio_nop $callback->()
		596
		597	This is a special request - it does nothing in itself and is only used for
		598	side effects, such as when you want to add a dummy request to a group so
		599	that finishing the requests in the group depends on executing the given
		600	code.
		601
		602	While this request does nothing, it still goes through the execution
		603	phase and still requires a worker thread. Thus, the callback will not
		604	be executed immediately but only after other requests in the queue have
		605	entered their execution phase. This can be used to measure request
		606	latency.
		607
		608	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		609
		610	Mainly used for debugging and benchmarking, this aio request puts one of
		611	the request workers to sleep for the given time.
		612
		613	While it is theoretically handy to have simple I/O scheduling requests
		614	like sleep and file handle readable/writable, the overhead this creates is
		615	immense (it blocks a thread for a long time) so do not use this function
		616	except to put your application under artificial I/O pressure.
		617
		618	=back
		619
		620	=head2 IO::AIO::REQ CLASS
		621
		622	All non-aggregate C<aio_*> functions return an object of this class when
		623	called in non-void context.
		624
		625	=over 4
		626
		627	=item cancel $req
		628
		629	Cancels the request, if possible. Has the effect of skipping execution
		630	when entering the B<execute> state and skipping calling the callback when
		631	entering the the B<result> state, but will leave the request otherwise
		632	untouched. That means that requests that currently execute will not be
		633	stopped and resources held by the request will not be freed prematurely.
		634
		635	=item cb $req $callback->(...)
		636
		637	Replace (or simply set) the callback registered to the request.
		638
		639	=back
		640
		641	=head2 IO::AIO::GRP CLASS
		642
		643	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		644	objects of this class, too.
		645
		646	A IO::AIO::GRP object is a special request that can contain multiple other
		647	aio requests.
		648
		649	You create one by calling the C<aio_group> constructing function with a
		650	callback that will be called when all contained requests have entered the
		651	C<done> state:
		652
		653	my $grp = aio_group sub {
		654	print "all requests are done\n";
		655	};
		656
		657	You add requests by calling the C<add> method with one or more
		658	C<IO::AIO::REQ> objects:
		659
		660	$grp->add (aio_unlink "...");
		661
		662	add $grp aio_stat "...", sub {
		663	$_[0] or return $grp->result ("error");
		664
		665	# add another request dynamically, if first succeeded
		666	add $grp aio_open "...", sub {
		667	$grp->result ("ok");
		668	};
		669	};
		670
		671	This makes it very easy to create composite requests (see the source of
		672	C<aio_move> for an application) that work and feel like simple requests.
		673
		674	=over 4
		675
		676	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		677	C<IO::AIO::poll_cb>, just like any other request.
		678
		679	=item * They can be canceled like any other request. Canceling will cancel not
		680	only the request itself, but also all requests it contains.
		681
		682	=item * They can also can also be added to other IO::AIO::GRP objects.
		683
		684	=item * You must not add requests to a group from within the group callback (or
		685	any later time).
		686
		687	=back
		688
		689	Their lifetime, simplified, looks like this: when they are empty, they
		690	will finish very quickly. If they contain only requests that are in the
		691	C<done> state, they will also finish. Otherwise they will continue to
		692	exist.
		693
		694	That means after creating a group you have some time to add requests. And
		695	in the callbacks of those requests, you can add further requests to the
		696	group. And only when all those requests have finished will the the group
		697	itself finish.
		698
		699	=over 4
		700
		701	=item add $grp ...
		702
		703	=item $grp->add (...)
		704
		705	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		706	be added, including other groups, as long as you do not create circular
		707	dependencies.
		708
		709	Returns all its arguments.
		710
		711	=item $grp->cancel_subs
		712
		713	Cancel all subrequests and clears any feeder, but not the group request
		714	itself. Useful when you queued a lot of events but got a result early.
		715
		716	=item $grp->result (...)
		717
		718	Set the result value(s) that will be passed to the group callback when all
		719	subrequests have finished. By default, no argument will be passed.
		720
		721	=item feed $grp $callback->($grp)
		722
		723	Sets a feeder/generator on this group: every group can have an attached
		724	generator that generates requests if idle. The idea behind this is that,
		725	although you could just queue as many requests as you want in a group,
		726	this might starve other requests for a potentially long time. For
		727	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		728	requests, delaying any later requests for a long time.
		729
		730	To avoid this, and allow incremental generation of requests, you can
		731	instead a group and set a feeder on it that generates those requests. The
		732	feed callback will be called whenever there are few enough (see C<limit>,
		733	below) requests active in the group itself and is expected to queue more
		734	requests.
		735
		736	The feed callback can queue as many requests as it likes (i.e. C<add> does
		737	not impose any limits).
		738
		739	If the feed does not queue more requests when called, it will be
		740	automatically removed from the group.
		741
		742	If the feed limit is C<0>, it will be set to C<2> automatically.
		743
		744	Example:
		745
		746	# stat all files in @files, but only ever use four aio requests concurrently:
		747
		748	my $grp = aio_group sub { print "finished\n" };
		749	limit $grp 4;
		750	feed $grp sub {
		751	my $file = pop @files
		752	or return;
		753
		754	add $grp aio_stat $file, sub { ... };
		755	};
		756
		757	=item limit $grp $num
		758
		759	Sets the feeder limit for the group: The feeder will be called whenever
		760	the group contains less than this many requests.
		761
		762	Setting the limit to C<0> will pause the feeding process.
400		763
401	=back	764	=back
402		765
403	=head2 SUPPORT FUNCTIONS	766	=head2 SUPPORT FUNCTIONS
404		767
…		…
462	IO::AIO::poll_wait, IO::AIO::poll_cb	825	IO::AIO::poll_wait, IO::AIO::poll_cb
463	if IO::AIO::nreqs;	826	if IO::AIO::nreqs;
464		827
465	=item IO::AIO::min_parallel $nthreads	828	=item IO::AIO::min_parallel $nthreads
466		829
467	Set the minimum number of AIO threads to C<$nthreads>. The current default	830	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	831	default is C<8>, which means eight asynchronous operations can execute
469	(the number of outstanding operations, however, is unlimited).	832	concurrently at any one time (the number of outstanding requests,
		833	however, is unlimited).
470		834
471	IO::AIO starts threads only on demand, when an AIO request is queued and	835	IO::AIO starts threads only on demand, when an AIO request is queued and
472	no free thread exists.	836	no free thread exists.
473		837
474	It is recommended to keep the number of threads low, as some Linux	838	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	839	Linux kernel versions will scale negatively with the number of threads
476	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	840	(higher parallelity => MUCH higher latency). With current Linux 2.6
477	threads should be fine.	841	versions, 4-32 threads should be fine.
478		842
479	Under most circumstances you don't need to call this function, as the	843	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.	844	module selects a default that is suitable for low to moderate load.
481		845
482	=item IO::AIO::max_parallel $nthreads	846	=item IO::AIO::max_parallel $nthreads
…		…
493		857
494	Under normal circumstances you don't need to call this function.	858	Under normal circumstances you don't need to call this function.
495		859
496	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	860	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
497		861
		862	[REMOVED]
		863
		864	Pre-2.x versions used max_outstanding for a crude request queue length limit.
		865
		866	In 2.x+ you are advised to use a group and a feeder to limit
		867	concurrency. The max_outstanding feature ran very unstable (endless
		868	recursions causing segfaults, bad interaction with groups etc.) and was
		869	removed.
		870
		871	I am deeply sorry, but I am still on the hunt for a good limiting interface.
		872
		873	Original description was as follows:
		874
498	Sets the maximum number of outstanding requests to C<$nreqs>. If you	875	Sets the maximum number of outstanding requests to C<$nreqs>. If you try
499	try to queue up more than this number of requests, the caller will block until	876	to queue up more than this number of requests, the caller will block until
500	some requests have been handled.	877	some requests have been handled.
501
502	The default is very large, so normally there is no practical limit. If you
503	queue up many requests in a loop it often improves speed if you set
504	this to a relatively low number, such as C<100>.
505
506	Under normal circumstances you don't need to call this function.
507		878
508	=back	879	=back
509		880
510	=cut	881	=cut
511		882
…		…
523	or return undef;	894	or return undef;
524		895
525	*$sym	896	*$sym
526	}	897	}
527		898
528	min_parallel 4;	899	min_parallel 8;
529		900
530	END {	901	END {
531	max_parallel 0;	902	max_parallel 0;
532	}	903	}
533		904
534	1;	905	1;
535		906
536	=head2 FORK BEHAVIOUR	907	=head2 FORK BEHAVIOUR
537		908
		909	This module should do "the right thing" when the process using it forks:
		910
538	Before the fork, IO::AIO enters a quiescent state where no requests	911	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	912	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	913	the fork the parent simply leaves the quiescent state and continues
541	request/result processing, while the child clears the request/result	914	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	915	(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	916	parent). Threads will be started on demand until the limit set in the
544	parent process has been reached again.	917	parent process has been reached again.
545		918
		919	In short: the parent will, after a short pause, continue as if fork had
		920	not been called, while the child will act as if IO::AIO has not been used
		921	yet.
		922
		923	=head2 MEMORY USAGE
		924
		925	Per-request usage:
		926
		927	Each aio request uses - depending on your architecture - around 100-200
		928	bytes of memory. In addition, stat requests need a stat buffer (possibly
		929	a few hundred bytes), readdir requires a result buffer and so on. Perl
		930	scalars and other data passed into aio requests will also be locked and
		931	will consume memory till the request has entered the done state.
		932
		933	This is now awfully much, so queuing lots of requests is not usually a
		934	problem.
		935
		936	Per-thread usage:
		937
		938	In the execution phase, some aio requests require more memory for
		939	temporary buffers, and each thread requires a stack and other data
		940	structures (usually around 16k-128k, depending on the OS).
		941
		942	=head1 KNOWN BUGS
		943
		944	Known bugs will be fixed in the next release.
		945
546	=head1 SEE ALSO	946	=head1 SEE ALSO
547		947
548	L<Coro>, L<Linux::AIO>.	948	L<Coro::AIO>.
549		949
550	=head1 AUTHOR	950	=head1 AUTHOR
551		951
552	Marc Lehmann <schmorp@schmorp.de>	952	Marc Lehmann <schmorp@schmorp.de>
553	http://home.schmorp.de/	953	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.42 by root, Mon Dec 26 18:15:23 2005 UTC vs. Revision 1.77 by root, Wed Oct 25 17:57:30 2006 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.42 by root, Mon Dec 26 18:15:23 2005 UTC vs.
Revision 1.77 by root, Wed Oct 25 17:57:30 2006 UTC