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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.41 by root, Wed Sep 7 17:41:17 2005 UTC vs.
Revision 1.81 by root, Fri Oct 27 19:17:23 2006 UTC

…		…
15		15
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	16	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	17	$_[0] > 0 or die "read error: $!";
18	};	18	};
19		19
20	# Event	20	# version 2+ has request and group objects
		21	use IO::AIO 2;
		22
		23	aioreq_pri 4; # give next request a very high priority
		24	my $req = aio_unlink "/tmp/file", sub { };
		25	$req->cancel; # cancel request if still in queue
		26
		27	my $grp = aio_group sub { print "all stats done\n" };
		28	add $grp aio_stat "..." for ...;
		29
		30	# AnyEvent integration
		31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		33
		34	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	35	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	36	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	37	cb => \&IO::AIO::poll_cb);
24		38
25	# Glib/Gtk2	39	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	40	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb; 1 };	41	in => sub { IO::AIO::poll_cb; 1 };
28		42
29	# Tk	43	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	45	readable => \&IO::AIO::poll_cb);
32		46
33	# Danga::Socket	47	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	49	\&IO::AIO::poll_cb);
36		50
37
38	=head1 DESCRIPTION	51	=head1 DESCRIPTION
39		52
40	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
41	operating system supports.	54	operating system supports.
42		55
43	Currently, a number of threads are started that execute your read/writes	56	In this version, a number of threads are started that execute your
44	and signal their completion. You don't need thread support in your libc or	57	requests and signal their completion. You don't need thread support
45	perl, and the threads created by this module will not be visible to the	58	in perl, and the threads created by this module will not be visible
46	pthreads library. In the future, this module might make use of the native	59	to perl. In the future, this module might make use of the native aio
47	aio functions available on many operating systems. However, they are often	60	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	61	not well-supported or restricted (Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	62	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	63	aio_write, so the remaining functionality would have to be implemented
		64	using threads anyway.
51		65
52	Although the module will work with in the presence of other threads, it is	66	Although the module will work with in the presence of other (Perl-)
53	currently not reentrant, so use appropriate locking yourself, always call	67	threads, it is currently not reentrant in any way, so use appropriate
54	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	68	locking yourself, always call C<poll_cb> from within the same thread, or
55	C<aio_> functions) recursively.	69	never call C<poll_cb> (or other C<aio_> functions) recursively.
		70
		71	=head1 REQUEST ANATOMY AND LIFETIME
		72
		73	Every C<aio_*> function creates a request. which is a C data structure not
		74	directly visible to Perl.
		75
		76	If called in non-void context, every request function returns a Perl
		77	object representing the request. In void context, nothing is returned,
		78	which saves a bit of memory.
		79
		80	The perl object is a fairly standard ref-to-hash object. The hash contents
		81	are not used by IO::AIO so you are free to store anything you like in it.
		82
		83	During their existance, aio requests travel through the following states,
		84	in order:
		85
		86	=over 4
		87
		88	=item ready
		89
		90	Immediately after a request is created it is put into the ready state,
		91	waiting for a thread to execute it.
		92
		93	=item execute
		94
		95	A thread has accepted the request for processing and is currently
		96	executing it (e.g. blocking in read).
		97
		98	=item pending
		99
		100	The request has been executed and is waiting for result processing.
		101
		102	While request submission and execution is fully asynchronous, result
		103	processing is not and relies on the perl interpreter calling C<poll_cb>
		104	(or another function with the same effect).
		105
		106	=item result
		107
		108	The request results are processed synchronously by C<poll_cb>.
		109
		110	The C<poll_cb> function will process all outstanding aio requests by
		111	calling their callbacks, freeing memory associated with them and managing
		112	any groups they are contained in.
		113
		114	=item done
		115
		116	Request has reached the end of its lifetime and holds no resources anymore
		117	(except possibly for the Perl object, but its connection to the actual
		118	aio request is severed and calling its methods will either do nothing or
		119	result in a runtime error).
56		120
57	=cut	121	=cut
58		122
59	package IO::AIO;	123	package IO::AIO;
60		124
61	no warnings;	125	no warnings;
		126	use strict 'vars';
62		127
63	use base 'Exporter';	128	use base 'Exporter';
64		129
65	use Fcntl ();
66
67	BEGIN {	130	BEGIN {
68	$VERSION = '1.61';	131	our $VERSION = '2.0';
69		132
70	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	133	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	134	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72	aio_fsync aio_fdatasync aio_readahead);	135	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
73	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	136	aio_group aio_nop);
74	max_outstanding nreqs);	137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		139	min_parallel max_parallel nreqs nready npending);
		140
		141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
75		142
76	require XSLoader;	143	require XSLoader;
77	XSLoader::load IO::AIO, $VERSION;	144	XSLoader::load ("IO::AIO", $VERSION);
78	}	145	}
79		146
80	=head1 FUNCTIONS	147	=head1 FUNCTIONS
81		148
82	=head2 AIO FUNCTIONS	149	=head2 AIO FUNCTIONS
…		…
90	syscall has been executed asynchronously.	157	syscall has been executed asynchronously.
91		158
92	All functions expecting a filehandle keep a copy of the filehandle	159	All functions expecting a filehandle keep a copy of the filehandle
93	internally until the request has finished.	160	internally until the request has finished.
94		161
		162	All requests return objects of type L<IO::AIO::REQ> that allow further
		163	manipulation of those requests while they are in-flight.
		164
95	The pathnames you pass to these routines I<must> be absolute and	165	The pathnames you pass to these routines I<must> be absolute and
96	encoded in byte form. The reason for the former is that at the time the	166	encoded in byte form. The reason for the former is that at the time the
97	request is being executed, the current working directory could have	167	request is being executed, the current working directory could have
98	changed. Alternatively, you can make sure that you never change the	168	changed. Alternatively, you can make sure that you never change the
99	current working directory.	169	current working directory.
…		…
104	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
105	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	175	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
106	use something else.	176	use something else.
107		177
108	=over 4	178	=over 4
		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.
109		210
110	=item aio_open $pathname, $flags, $mode, $callback->($fh)	211	=item aio_open $pathname, $flags, $mode, $callback->($fh)
111		212
112	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
113	created filehandle for the file.	214	created filehandle for the file.
…		…
164	aio_read $fh, 7, 15, $buffer, 0, sub {	265	aio_read $fh, 7, 15, $buffer, 0, sub {
165	$_[0] > 0 or die "read error: $!";	266	$_[0] > 0 or die "read error: $!";
166	print "read $_[0] bytes: <$buffer>\n";	267	print "read $_[0] bytes: <$buffer>\n";
167	};	268	};
168		269
		270	=item aio_move $srcpath, $dstpath, $callback->($status)
		271
		272	Try to move the I<file> (directories not supported as either source or
		273	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		274	the C<0> (error) or C<-1> ok.
		275
		276	This is a composite request that tries to rename(2) the file first. If
		277	rename files with C<EXDEV>, it creates the destination file with mode 0200
		278	and copies the contents of the source file into it using C<aio_sendfile>,
		279	followed by restoring atime, mtime, access mode and uid/gid, in that
		280	order, and unlinking the C<$srcpath>.
		281
		282	If an error occurs, the partial destination file will be unlinked, if
		283	possible, except when setting atime, mtime, access mode and uid/gid, where
		284	errors are being ignored.
		285
		286	=cut
		287
		288	sub aio_move($$$) {
		289	my ($src, $dst, $cb) = @_;
		290
		291	my $pri = aioreq_pri;
		292	my $grp = aio_group $cb;
		293
		294	aioreq_pri $pri;
		295	add $grp aio_rename $src, $dst, sub {
		296	if ($_[0] && $! == EXDEV) {
		297	aioreq_pri $pri;
		298	add $grp aio_open $src, O_RDONLY, 0, sub {
		299	if (my $src_fh = $_[0]) {
		300	my @stat = stat $src_fh;
		301
		302	aioreq_pri $pri;
		303	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		304	if (my $dst_fh = $_[0]) {
		305	aioreq_pri $pri;
		306	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		307	close $src_fh;
		308
		309	if ($_[0] == $stat[7]) {
		310	utime $stat[8], $stat[9], $dst;
		311	chmod $stat[2] & 07777, $dst_fh;
		312	chown $stat[4], $stat[5], $dst_fh;
		313	close $dst_fh;
		314
		315	aioreq_pri $pri;
		316	add $grp aio_unlink $src, sub {
		317	$grp->result ($_[0]);
		318	};
		319	} else {
		320	my $errno = $!;
		321	aioreq_pri $pri;
		322	add $grp aio_unlink $dst, sub {
		323	$! = $errno;
		324	$grp->result (-1);
		325	};
		326	}
		327	};
		328	} else {
		329	$grp->result (-1);
		330	}
		331	},
		332
		333	} else {
		334	$grp->result (-1);
		335	}
		336	};
		337	} else {
		338	$grp->result ($_[0]);
		339	}
		340	};
		341
		342	$grp
		343	}
		344
169	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	345	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
170		346
171	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	347	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
172	reading at byte offset C<$in_offset>, and starts writing at the current	348	reading at byte offset C<$in_offset>, and starts writing at the current
173	file offset of C<$out_fh>. Because of that, it is not safe to issue more	349	file offset of C<$out_fh>. Because of that, it is not safe to issue more
…		…
228	=item aio_unlink $pathname, $callback->($status)	404	=item aio_unlink $pathname, $callback->($status)
229		405
230	Asynchronously unlink (delete) a file and call the callback with the	406	Asynchronously unlink (delete) a file and call the callback with the
231	result code.	407	result code.
232		408
		409	=item aio_link $srcpath, $dstpath, $callback->($status)
		410
		411	Asynchronously create a new link to the existing object at C<$srcpath> at
		412	the path C<$dstpath> and call the callback with the result code.
		413
		414	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		415
		416	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		417	the path C<$dstpath> and call the callback with the result code.
		418
		419	=item aio_rename $srcpath, $dstpath, $callback->($status)
		420
		421	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		422	rename(2) and call the callback with the result code.
		423
233	=item aio_rmdir $pathname, $callback->($status)	424	=item aio_rmdir $pathname, $callback->($status)
234		425
235	Asynchronously rmdir (delete) a directory and call the callback with the	426	Asynchronously rmdir (delete) a directory and call the callback with the
236	result code.	427	result code.
237		428
238	=item aio_readdir $pathname $callback->($entries)	429	=item aio_readdir $pathname, $callback->($entries)
239		430
240	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	431	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
241	directory (i.e. opendir + readdir + closedir). The entries will not be	432	directory (i.e. opendir + readdir + closedir). The entries will not be
242	sorted, and will B<NOT> include the C<.> and C<..> entries.	433	sorted, and will B<NOT> include the C<.> and C<..> entries.
243		434
244	The callback a single argument which is either C<undef> or an array-ref	435	The callback a single argument which is either C<undef> or an array-ref
245	with the filenames.	436	with the filenames.
246		437
247	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	438	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
248		439
249	Scans a directory (similar to C<aio_readdir>) and tries to separate the	440	Scans a directory (similar to C<aio_readdir>) but additionally tries to
250	entries of directory C<$path> into two sets of names, ones you can recurse	441	efficiently separate the entries of directory C<$path> into two sets of
251	into (directories), and ones you cannot recurse into (everything else).	442	names, directories you can recurse into (directories), and ones you cannot
		443	recurse into (everything else, including symlinks to directories).
252		444
253	C<aio_scandir> is a composite request that consists of many	445	C<aio_scandir> is a composite request that creates of many sub requests_
254	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	446	C<$maxreq> specifies the maximum number of outstanding aio requests that
255	aio requests that this function generates. If it is C<< <= 0 >>, then a	447	this function generates. If it is C<< <= 0 >>, then a suitable default
256	suitable default will be chosen (currently 8).	448	will be chosen (currently 4).
257		449
258	On error, the callback is called without arguments, otherwise it receives	450	On error, the callback is called without arguments, otherwise it receives
259	two array-refs with path-relative entry names.	451	two array-refs with path-relative entry names.
260		452
261	Example:	453	Example:
…		…
269	Implementation notes.	461	Implementation notes.
270		462
271	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	463	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
272		464
273	After reading the directory, the modification time, size etc. of the	465	After reading the directory, the modification time, size etc. of the
274	directory before and after the readdir is checked, and if they match, the	466	directory before and after the readdir is checked, and if they match (and
275	link count will be used to decide how many entries are directories (if	467	isn't the current time), the link count will be used to decide how many
276	>= 2). Otherwise, no knowledge of the number of subdirectories will be	468	entries are directories (if >= 2). Otherwise, no knowledge of the number
277	assumed.	469	of subdirectories will be assumed.
278		470
279	Then entires will be sorted into likely directories (everything without a	471	Then entries will be sorted into likely directories (everything without
280	non-initial dot) and likely non-directories (everything else). Then every	472	a non-initial dot currently) and likely non-directories (everything
281	entry + C</.> will be C<stat>'ed, likely directories first. This is often	473	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		474	likely directories first. If that succeeds, it assumes that the entry
		475	is a directory or a symlink to directory (which will be checked
		476	seperately). This is often faster than stat'ing the entry itself because
282	faster because filesystems might detect the type of the entry without	477	filesystems might detect the type of the entry without reading the inode
283	reading the inode data (e.g. ext2s filetype feature). If that succeeds,	478	data (e.g. ext2fs filetype feature).
284	it assumes that the entry is a directory or a symlink to directory (which
285	will be checked seperately).
286		479
287	If the known number of directories has been reached, the rest of the	480	If the known number of directories (link count - 2) has been reached, the
288	entries is assumed to be non-directories.	481	rest of the entries is assumed to be non-directories.
		482
		483	This only works with certainty on POSIX (= UNIX) filesystems, which
		484	fortunately are the vast majority of filesystems around.
		485
		486	It will also likely work on non-POSIX filesystems with reduced efficiency
		487	as those tend to return 0 or 1 as link counts, which disables the
		488	directory counting heuristic.
289		489
290	=cut	490	=cut
291		491
292	sub aio_scandir($$$) {	492	sub aio_scandir($$$) {
293	my ($path, $maxreq, $cb) = @_;	493	my ($path, $maxreq, $cb) = @_;
294		494
		495	my $pri = aioreq_pri;
		496
		497	my $grp = aio_group $cb;
		498
295	$maxreq = 8 if $maxreq <= 0;	499	$maxreq = 4 if $maxreq <= 0;
296		500
297	# stat once	501	# stat once
		502	aioreq_pri $pri;
298	aio_stat $path, sub {	503	add $grp aio_stat $path, sub {
299	$cb->() if $_[0];	504	return $grp->result () if $_[0];
		505	my $now = time;
300	my $hash1 = join ":", (stat _)[0,1,3,7,9];	506	my $hash1 = join ":", (stat _)[0,1,3,7,9];
301		507
302	# read the directory entries	508	# read the directory entries
		509	aioreq_pri $pri;
303	aio_readdir $path, sub {	510	add $grp aio_readdir $path, sub {
304	my $entries = shift	511	my $entries = shift
305	or return $cb->();	512	or return $grp->result ();
306		513
307	# stat the dir another time	514	# stat the dir another time
		515	aioreq_pri $pri;
308	aio_stat $path, sub {	516	add $grp aio_stat $path, sub {
309	my $hash2 = join ":", (stat _)[0,1,3,7,9];	517	my $hash2 = join ":", (stat _)[0,1,3,7,9];
310		518
311	my $ndirs;	519	my $ndirs;
312		520
313	# take the slow route if anything looks fishy	521	# take the slow route if anything looks fishy
314	if ($hash1 ne $hash2) {	522	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
315	$ndirs = -1;	523	$ndirs = -1;
316	} else {	524	} else {
317	# if nlink == 2, we are finished	525	# if nlink == 2, we are finished
318	# on non-posix-fs's, we rely on nlink < 2	526	# on non-posix-fs's, we rely on nlink < 2
319	$ndirs = (stat _)[3] - 2	527	$ndirs = (stat _)[3] - 2
320	or $cb->([], $entries);	528	or return $grp->result ([], $entries);
321	}	529	}
322		530
323	# sort into likely dirs and likely nondirs	531	# sort into likely dirs and likely nondirs
324	# dirs == files without ".", short entries first	532	# dirs == files without ".", short entries first
325	$entries = [map $_->[0],	533	$entries = [map $_->[0],
…		…
327	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	535	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
328	@$entries];	536	@$entries];
329		537
330	my (@dirs, @nondirs);	538	my (@dirs, @nondirs);
331		539
332	my ($statcb, $schedcb);	540	my $statgrp = add $grp aio_group sub {
333	my $nreq = 0;	541	$grp->result (\@dirs, \@nondirs);
		542	};
334		543
335	$schedcb = sub {	544	limit $statgrp $maxreq;
336	if (@$entries) {	545	feed $statgrp sub {
337	if ($nreq < $maxreq) {	546	return unless @$entries;
338	my $ent = pop @$entries;	547	my $entry = pop @$entries;
		548
		549	aioreq_pri $pri;
		550	add $statgrp aio_stat "$path/$entry/.", sub {
		551	if ($_[0] < 0) {
		552	push @nondirs, $entry;
		553	} else {
		554	# need to check for real directory
		555	aioreq_pri $pri;
		556	add $statgrp aio_lstat "$path/$entry", sub {
		557	if (-d _) {
		558	push @dirs, $entry;
		559
		560	unless (--$ndirs) {
		561	push @nondirs, @$entries;
		562	feed $statgrp;
		563	}
		564	} else {
		565	push @nondirs, $entry;
		566	}
339	$nreq++;	567	}
340	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
341	}	568	}
342	} elsif (!$nreq) {
343	# finished
344	undef $statcb;
345	undef $schedcb;
346	$cb->(\@dirs, \@nondirs);
347	undef $cb;
348	}	569	};
349	};	570	};
350	$statcb = sub {
351	my ($status, $entry) = @_;
352
353	if ($status < 0) {
354	$nreq--;
355	push @nondirs, $entry;
356	&$schedcb;
357	} else {
358	# need to check for real directory
359	aio_lstat "$path/$entry", sub {
360	$nreq--;
361
362	if (-d _) {
363	push @dirs, $entry;
364
365	if (!--$ndirs) {
366	push @nondirs, @$entries;
367	$entries = [];
368	}
369	} else {
370	push @nondirs, $entry;
371	}
372
373	&$schedcb;
374	}
375	}
376	};
377
378	&$schedcb while @$entries && $nreq < $maxreq;
379	};	571	};
380	};	572	};
381	};	573	};
		574
		575	$grp
382	}	576	}
383		577
384	=item aio_fsync $fh, $callback->($status)	578	=item aio_fsync $fh, $callback->($status)
385		579
386	Asynchronously call fsync on the given filehandle and call the callback	580	Asynchronously call fsync on the given filehandle and call the callback
…		…
391	Asynchronously call fdatasync on the given filehandle and call the	585	Asynchronously call fdatasync on the given filehandle and call the
392	callback with the fdatasync result code.	586	callback with the fdatasync result code.
393		587
394	If this call isn't available because your OS lacks it or it couldn't be	588	If this call isn't available because your OS lacks it or it couldn't be
395	detected, it will be emulated by calling C<fsync> instead.	589	detected, it will be emulated by calling C<fsync> instead.
		590
		591	=item aio_group $callback->(...)
		592
		593	This is a very special aio request: Instead of doing something, it is a
		594	container for other aio requests, which is useful if you want to bundle
		595	many requests into a single, composite, request with a definite callback
		596	and the ability to cancel the whole request with its subrequests.
		597
		598	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		599	for more info.
		600
		601	Example:
		602
		603	my $grp = aio_group sub {
		604	print "all stats done\n";
		605	};
		606
		607	add $grp
		608	(aio_stat ...),
		609	(aio_stat ...),
		610	...;
		611
		612	=item aio_nop $callback->()
		613
		614	This is a special request - it does nothing in itself and is only used for
		615	side effects, such as when you want to add a dummy request to a group so
		616	that finishing the requests in the group depends on executing the given
		617	code.
		618
		619	While this request does nothing, it still goes through the execution
		620	phase and still requires a worker thread. Thus, the callback will not
		621	be executed immediately but only after other requests in the queue have
		622	entered their execution phase. This can be used to measure request
		623	latency.
		624
		625	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		626
		627	Mainly used for debugging and benchmarking, this aio request puts one of
		628	the request workers to sleep for the given time.
		629
		630	While it is theoretically handy to have simple I/O scheduling requests
		631	like sleep and file handle readable/writable, the overhead this creates is
		632	immense (it blocks a thread for a long time) so do not use this function
		633	except to put your application under artificial I/O pressure.
		634
		635	=back
		636
		637	=head2 IO::AIO::REQ CLASS
		638
		639	All non-aggregate C<aio_*> functions return an object of this class when
		640	called in non-void context.
		641
		642	=over 4
		643
		644	=item cancel $req
		645
		646	Cancels the request, if possible. Has the effect of skipping execution
		647	when entering the B<execute> state and skipping calling the callback when
		648	entering the the B<result> state, but will leave the request otherwise
		649	untouched. That means that requests that currently execute will not be
		650	stopped and resources held by the request will not be freed prematurely.
		651
		652	=item cb $req $callback->(...)
		653
		654	Replace (or simply set) the callback registered to the request.
		655
		656	=back
		657
		658	=head2 IO::AIO::GRP CLASS
		659
		660	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		661	objects of this class, too.
		662
		663	A IO::AIO::GRP object is a special request that can contain multiple other
		664	aio requests.
		665
		666	You create one by calling the C<aio_group> constructing function with a
		667	callback that will be called when all contained requests have entered the
		668	C<done> state:
		669
		670	my $grp = aio_group sub {
		671	print "all requests are done\n";
		672	};
		673
		674	You add requests by calling the C<add> method with one or more
		675	C<IO::AIO::REQ> objects:
		676
		677	$grp->add (aio_unlink "...");
		678
		679	add $grp aio_stat "...", sub {
		680	$_[0] or return $grp->result ("error");
		681
		682	# add another request dynamically, if first succeeded
		683	add $grp aio_open "...", sub {
		684	$grp->result ("ok");
		685	};
		686	};
		687
		688	This makes it very easy to create composite requests (see the source of
		689	C<aio_move> for an application) that work and feel like simple requests.
		690
		691	=over 4
		692
		693	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		694	C<IO::AIO::poll_cb>, just like any other request.
		695
		696	=item * They can be canceled like any other request. Canceling will cancel not
		697	only the request itself, but also all requests it contains.
		698
		699	=item * They can also can also be added to other IO::AIO::GRP objects.
		700
		701	=item * You must not add requests to a group from within the group callback (or
		702	any later time).
		703
		704	=back
		705
		706	Their lifetime, simplified, looks like this: when they are empty, they
		707	will finish very quickly. If they contain only requests that are in the
		708	C<done> state, they will also finish. Otherwise they will continue to
		709	exist.
		710
		711	That means after creating a group you have some time to add requests. And
		712	in the callbacks of those requests, you can add further requests to the
		713	group. And only when all those requests have finished will the the group
		714	itself finish.
		715
		716	=over 4
		717
		718	=item add $grp ...
		719
		720	=item $grp->add (...)
		721
		722	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		723	be added, including other groups, as long as you do not create circular
		724	dependencies.
		725
		726	Returns all its arguments.
		727
		728	=item $grp->cancel_subs
		729
		730	Cancel all subrequests and clears any feeder, but not the group request
		731	itself. Useful when you queued a lot of events but got a result early.
		732
		733	=item $grp->result (...)
		734
		735	Set the result value(s) that will be passed to the group callback when all
		736	subrequests have finished and set thre groups errno to the current value
		737	of errno (just like calling C<errno> without an error number). By default,
		738	no argument will be passed and errno is zero.
		739
		740	=item $grp->errno ([$errno])
		741
		742	Sets the group errno value to C<$errno>, or the current value of errno
		743	when the argument is missing.
		744
		745	Every aio request has an associated errno value that is restored when
		746	the callback is invoked. This method lets you change this value from its
		747	default (0).
		748
		749	Calling C<result> will also set errno, so make sure you either set C<$!>
		750	before the call to C<result>, or call c<errno> after it.
		751
		752	=item feed $grp $callback->($grp)
		753
		754	Sets a feeder/generator on this group: every group can have an attached
		755	generator that generates requests if idle. The idea behind this is that,
		756	although you could just queue as many requests as you want in a group,
		757	this might starve other requests for a potentially long time. For
		758	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		759	requests, delaying any later requests for a long time.
		760
		761	To avoid this, and allow incremental generation of requests, you can
		762	instead a group and set a feeder on it that generates those requests. The
		763	feed callback will be called whenever there are few enough (see C<limit>,
		764	below) requests active in the group itself and is expected to queue more
		765	requests.
		766
		767	The feed callback can queue as many requests as it likes (i.e. C<add> does
		768	not impose any limits).
		769
		770	If the feed does not queue more requests when called, it will be
		771	automatically removed from the group.
		772
		773	If the feed limit is C<0>, it will be set to C<2> automatically.
		774
		775	Example:
		776
		777	# stat all files in @files, but only ever use four aio requests concurrently:
		778
		779	my $grp = aio_group sub { print "finished\n" };
		780	limit $grp 4;
		781	feed $grp sub {
		782	my $file = pop @files
		783	or return;
		784
		785	add $grp aio_stat $file, sub { ... };
		786	};
		787
		788	=item limit $grp $num
		789
		790	Sets the feeder limit for the group: The feeder will be called whenever
		791	the group contains less than this many requests.
		792
		793	Setting the limit to C<0> will pause the feeding process.
396		794
397	=back	795	=back
398		796
399	=head2 SUPPORT FUNCTIONS	797	=head2 SUPPORT FUNCTIONS
400		798
…		…
413		811
414	Process all outstanding events on the result pipe. You have to call this	812	Process all outstanding events on the result pipe. You have to call this
415	regularly. Returns the number of events processed. Returns immediately	813	regularly. Returns the number of events processed. Returns immediately
416	when no events are outstanding.	814	when no events are outstanding.
417		815
		816	If not all requests were processed for whatever reason, the filehandle
		817	will still be ready when C<poll_cb> returns.
		818
418	Example: Install an Event watcher that automatically calls	819	Example: Install an Event watcher that automatically calls
419	IO::AIO::poll_cb with high priority:	820	IO::AIO::poll_cb with high priority:
420		821
421	Event->io (fd => IO::AIO::poll_fileno,	822	Event->io (fd => IO::AIO::poll_fileno,
422	poll => 'r', async => 1,	823	poll => 'r', async => 1,
423	cb => \&IO::AIO::poll_cb);	824	cb => \&IO::AIO::poll_cb);
424		825
		826	=item IO::AIO::poll_some $max_requests
		827
		828	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests
		829	at a time.
		830
		831	Useful if you want to ensure some level of interactiveness when perl is
		832	not fast enough to process all requests in time.
		833
		834	Example: Install an Event watcher that automatically calls
		835	IO::AIO::poll_some with low priority, to ensure that other parts of the
		836	program get the CPU sometimes even under high AIO load.
		837
		838	Event->io (fd => IO::AIO::poll_fileno,
		839	poll => 'r', nice => 1,
		840	cb => sub { IO::AIO::poll_some 256 });
		841
425	=item IO::AIO::poll_wait	842	=item IO::AIO::poll_wait
426		843
427	Wait till the result filehandle becomes ready for reading (simply does a	844	Wait till the result filehandle becomes ready for reading (simply does a
428	C<select> on the filehandle. This is useful if you want to synchronously wait	845	C<select> on the filehandle. This is useful if you want to synchronously wait
429	for some requests to finish).	846	for some requests to finish).
430		847
431	See C<nreqs> for an example.	848	See C<nreqs> for an example.
432		849
433	=item IO::AIO::nreqs	850	=item IO::AIO::nreqs
434		851
435	Returns the number of requests currently outstanding (i.e. for which their	852	Returns the number of requests currently in the ready, execute or pending
436	callback has not been invoked yet).	853	states (i.e. for which their callback has not been invoked yet).
437		854
438	Example: wait till there are no outstanding requests anymore:	855	Example: wait till there are no outstanding requests anymore:
439		856
440	IO::AIO::poll_wait, IO::AIO::poll_cb	857	IO::AIO::poll_wait, IO::AIO::poll_cb
441	while IO::AIO::nreqs;	858	while IO::AIO::nreqs;
442		859
		860	=item IO::AIO::nready
		861
		862	Returns the number of requests currently in the ready state (not yet
		863	executed).
		864
		865	=item IO::AIO::npending
		866
		867	Returns the number of requests currently in the pending state (executed,
		868	but not yet processed by poll_cb).
		869
443	=item IO::AIO::flush	870	=item IO::AIO::flush
444		871
445	Wait till all outstanding AIO requests have been handled.	872	Wait till all outstanding AIO requests have been handled.
446		873
447	Strictly equivalent to:	874	Strictly equivalent to:
…		…
458	IO::AIO::poll_wait, IO::AIO::poll_cb	885	IO::AIO::poll_wait, IO::AIO::poll_cb
459	if IO::AIO::nreqs;	886	if IO::AIO::nreqs;
460		887
461	=item IO::AIO::min_parallel $nthreads	888	=item IO::AIO::min_parallel $nthreads
462		889
463	Set the minimum number of AIO threads to C<$nthreads>. The current default	890	Set the minimum number of AIO threads to C<$nthreads>. The current
464	is C<4>, which means four asynchronous operations can be done at one time	891	default is C<8>, which means eight asynchronous operations can execute
465	(the number of outstanding operations, however, is unlimited).	892	concurrently at any one time (the number of outstanding requests,
		893	however, is unlimited).
466		894
467	IO::AIO starts threads only on demand, when an AIO request is queued and	895	IO::AIO starts threads only on demand, when an AIO request is queued and
468	no free thread exists.	896	no free thread exists.
469		897
470	It is recommended to keep the number of threads low, as some Linux	898	It is recommended to keep the number of threads relatively low, as some
471	kernel versions will scale negatively with the number of threads (higher	899	Linux kernel versions will scale negatively with the number of threads
472	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	900	(higher parallelity => MUCH higher latency). With current Linux 2.6
473	threads should be fine.	901	versions, 4-32 threads should be fine.
474		902
475	Under most circumstances you don't need to call this function, as the	903	Under most circumstances you don't need to call this function, as the
476	module selects a default that is suitable for low to moderate load.	904	module selects a default that is suitable for low to moderate load.
477		905
478	=item IO::AIO::max_parallel $nthreads	906	=item IO::AIO::max_parallel $nthreads
…		…
487	This module automatically runs C<max_parallel 0> at program end, to ensure	915	This module automatically runs C<max_parallel 0> at program end, to ensure
488	that all threads are killed and that there are no outstanding requests.	916	that all threads are killed and that there are no outstanding requests.
489		917
490	Under normal circumstances you don't need to call this function.	918	Under normal circumstances you don't need to call this function.
491		919
492	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	920	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		921
		922	This is a very bad function to use in interactive programs because it
		923	blocks, and a bad way to reduce concurrency because it is inexact: Better
		924	use an C<aio_group> together with a feed callback.
493		925
494	Sets the maximum number of outstanding requests to C<$nreqs>. If you	926	Sets the maximum number of outstanding requests to C<$nreqs>. If you
495	try to queue up more than this number of requests, the caller will block until	927	to queue up more than this number of requests, the next call to the
496	some requests have been handled.	928	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		929	function will block until the limit is no longer exceeded.
497		930
498	The default is very large, so normally there is no practical limit. If you	931	The default value is very large, so there is no practical limit on the
499	queue up many requests in a loop it often improves speed if you set	932	number of outstanding requests.
500	this to a relatively low number, such as C<100>.
501		933
502	Under normal circumstances you don't need to call this function.	934	You can still queue as many requests as you want. Therefore,
		935	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		936	as a stop gap to shield against fatal memory overflow (with large values).
503		937
504	=back	938	=back
505		939
506	=cut	940	=cut
507		941
…		…
519	or return undef;	953	or return undef;
520		954
521	*$sym	955	*$sym
522	}	956	}
523		957
524	min_parallel 4;	958	min_parallel 8;
525
526	END {
527	max_parallel 0;
528	}
529		959
530	1;	960	1;
531		961
532	=head2 FORK BEHAVIOUR	962	=head2 FORK BEHAVIOUR
		963
		964	This module should do "the right thing" when the process using it forks:
533		965
534	Before the fork, IO::AIO enters a quiescent state where no requests	966	Before the fork, IO::AIO enters a quiescent state where no requests
535	can be added in other threads and no results will be processed. After	967	can be added in other threads and no results will be processed. After
536	the fork the parent simply leaves the quiescent state and continues	968	the fork the parent simply leaves the quiescent state and continues
537	request/result processing, while the child clears the request/result	969	request/result processing, while the child frees the request/result queue
538	queue (so the requests started before the fork will only be handled in	970	(so that the requests started before the fork will only be handled in the
539	the parent). Threats will be started on demand until the limit ste in the	971	parent). Threads will be started on demand until the limit set in the
540	parent process has been reached again.	972	parent process has been reached again.
541		973
		974	In short: the parent will, after a short pause, continue as if fork had
		975	not been called, while the child will act as if IO::AIO has not been used
		976	yet.
		977
		978	=head2 MEMORY USAGE
		979
		980	Per-request usage:
		981
		982	Each aio request uses - depending on your architecture - around 100-200
		983	bytes of memory. In addition, stat requests need a stat buffer (possibly
		984	a few hundred bytes), readdir requires a result buffer and so on. Perl
		985	scalars and other data passed into aio requests will also be locked and
		986	will consume memory till the request has entered the done state.
		987
		988	This is now awfully much, so queuing lots of requests is not usually a
		989	problem.
		990
		991	Per-thread usage:
		992
		993	In the execution phase, some aio requests require more memory for
		994	temporary buffers, and each thread requires a stack and other data
		995	structures (usually around 16k-128k, depending on the OS).
		996
		997	=head1 KNOWN BUGS
		998
		999	Known bugs will be fixed in the next release.
		1000
542	=head1 SEE ALSO	1001	=head1 SEE ALSO
543		1002
544	L<Coro>, L<Linux::AIO>.	1003	L<Coro::AIO>.
545		1004
546	=head1 AUTHOR	1005	=head1 AUTHOR
547		1006
548	Marc Lehmann <schmorp@schmorp.de>	1007	Marc Lehmann <schmorp@schmorp.de>
549	http://home.schmorp.de/	1008	http://home.schmorp.de/

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Revision 1.81 by root, Fri Oct 27 19:17:23 2006 UTC