[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 1.83 by root, Fri Oct 27 20:11:58 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_copy aio_group aio_nop aio_mknod);
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.
…		…
228	=item aio_unlink $pathname, $callback->($status)	329	=item aio_unlink $pathname, $callback->($status)
229		330
230	Asynchronously unlink (delete) a file and call the callback with the	331	Asynchronously unlink (delete) a file and call the callback with the
231	result code.	332	result code.
232		333
		334	=item aio_mknod $path, $mode, $dev, $callback->($status)
		335
		336	Asynchronously create a device node (or fifo). See mknod(2).
		337
		338	The only portable (POSIX) way of calling this function is:
		339
		340	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		341
		342	=item aio_link $srcpath, $dstpath, $callback->($status)
		343
		344	Asynchronously create a new link to the existing object at C<$srcpath> at
		345	the path C<$dstpath> and call the callback with the result code.
		346
		347	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		348
		349	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		350	the path C<$dstpath> and call the callback with the result code.
		351
		352	=item aio_rename $srcpath, $dstpath, $callback->($status)
		353
		354	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		355	rename(2) and call the callback with the result code.
		356
233	=item aio_rmdir $pathname, $callback->($status)	357	=item aio_rmdir $pathname, $callback->($status)
234		358
235	Asynchronously rmdir (delete) a directory and call the callback with the	359	Asynchronously rmdir (delete) a directory and call the callback with the
236	result code.	360	result code.
237		361
238	=item aio_readdir $pathname $callback->($entries)	362	=item aio_readdir $pathname, $callback->($entries)
239		363
240	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	364	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	365	directory (i.e. opendir + readdir + closedir). The entries will not be
242	sorted, and will B<NOT> include the C<.> and C<..> entries.	366	sorted, and will B<NOT> include the C<.> and C<..> entries.
243		367
244	The callback a single argument which is either C<undef> or an array-ref	368	The callback a single argument which is either C<undef> or an array-ref
245	with the filenames.	369	with the filenames.
246		370
		371	=item aio_copy $srcpath, $dstpath, $callback->($status)
		372
		373	Try to copy the I<file> (directories not supported as either source or
		374	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		375	the C<0> (error) or C<-1> ok.
		376
		377	This is a composite request that it creates the destination file with
		378	mode 0200 and copies the contents of the source file into it using
		379	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		380	uid/gid, in that order.
		381
		382	If an error occurs, the partial destination file will be unlinked, if
		383	possible, except when setting atime, mtime, access mode and uid/gid, where
		384	errors are being ignored.
		385
		386	=cut
		387
		388	sub aio_copy($$;$) {
		389	my ($src, $dst, $cb) = @_;
		390
		391	my $pri = aioreq_pri;
		392	my $grp = aio_group $cb;
		393
		394	aioreq_pri $pri;
		395	add $grp aio_open $src, O_RDONLY, 0, sub {
		396	if (my $src_fh = $_[0]) {
		397	my @stat = stat $src_fh;
		398
		399	aioreq_pri $pri;
		400	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		401	if (my $dst_fh = $_[0]) {
		402	aioreq_pri $pri;
		403	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		404	if ($_[0] == $stat[7]) {
		405	$grp->result (0);
		406	close $src_fh;
		407
		408	# those should not normally block. should. should.
		409	utime $stat[8], $stat[9], $dst;
		410	chmod $stat[2] & 07777, $dst_fh;
		411	chown $stat[4], $stat[5], $dst_fh;
		412	close $dst_fh;
		413	} else {
		414	$grp->result (-1);
		415	close $src_fh;
		416	close $dst_fh;
		417
		418	aioreq $pri;
		419	add $grp aio_unlink $dst;
		420	}
		421	};
		422	} else {
		423	$grp->result (-1);
		424	}
		425	},
		426
		427	} else {
		428	$grp->result (-1);
		429	}
		430	};
		431
		432	$grp
		433	}
		434
		435	=item aio_move $srcpath, $dstpath, $callback->($status)
		436
		437	Try to move the I<file> (directories not supported as either source or
		438	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		439	the C<0> (error) or C<-1> ok.
		440
		441	This is a composite request that tries to rename(2) the file first. If
		442	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		443	that is successful, unlinking the C<$srcpath>.
		444
		445	=cut
		446
		447	sub aio_move($$;$) {
		448	my ($src, $dst, $cb) = @_;
		449
		450	my $pri = aioreq_pri;
		451	my $grp = aio_group $cb;
		452
		453	aioreq_pri $pri;
		454	add $grp aio_rename $src, $dst, sub {
		455	if ($_[0] && $! == EXDEV) {
		456	aioreq_pri $pri;
		457	add $grp aio_copy $src, $dst, sub {
		458	$grp->result ($_[0]);
		459
		460	if (!$_[0]) {
		461	aioreq_pri $pri;
		462	add $grp aio_unlink $src;
		463	}
		464	};
		465	} else {
		466	$grp->result ($_[0]);
		467	}
		468	};
		469
		470	$grp
		471	}
		472
247	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	473	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
248		474
249	Scans a directory (similar to C<aio_readdir>) and tries to separate the	475	Scans a directory (similar to C<aio_readdir>) but additionally tries to
250	entries of directory C<$path> into two sets of names, ones you can recurse	476	efficiently separate the entries of directory C<$path> into two sets of
251	into (directories), and ones you cannot recurse into (everything else).	477	names, directories you can recurse into (directories), and ones you cannot
		478	recurse into (everything else, including symlinks to directories).
252		479
253	C<aio_scandir> is a composite request that consists of many	480	C<aio_scandir> is a composite request that creates of many sub requests_
254	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	481	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	482	this function generates. If it is C<< <= 0 >>, then a suitable default
256	suitable default will be chosen (currently 8).	483	will be chosen (currently 4).
257		484
258	On error, the callback is called without arguments, otherwise it receives	485	On error, the callback is called without arguments, otherwise it receives
259	two array-refs with path-relative entry names.	486	two array-refs with path-relative entry names.
260		487
261	Example:	488	Example:
…		…
269	Implementation notes.	496	Implementation notes.
270		497
271	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	498	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
272		499
273	After reading the directory, the modification time, size etc. of the	500	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	501	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	502	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	503	entries are directories (if >= 2). Otherwise, no knowledge of the number
277	assumed.	504	of subdirectories will be assumed.
278		505
279	Then entires will be sorted into likely directories (everything without a	506	Then entries will be sorted into likely directories (everything without
280	non-initial dot) and likely non-directories (everything else). Then every	507	a non-initial dot currently) and likely non-directories (everything
281	entry + C</.> will be C<stat>'ed, likely directories first. This is often	508	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		509	likely directories first. If that succeeds, it assumes that the entry
		510	is a directory or a symlink to directory (which will be checked
		511	seperately). This is often faster than stat'ing the entry itself because
282	faster because filesystems might detect the type of the entry without	512	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,	513	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		514
287	If the known number of directories has been reached, the rest of the	515	If the known number of directories (link count - 2) has been reached, the
288	entries is assumed to be non-directories.	516	rest of the entries is assumed to be non-directories.
		517
		518	This only works with certainty on POSIX (= UNIX) filesystems, which
		519	fortunately are the vast majority of filesystems around.
		520
		521	It will also likely work on non-POSIX filesystems with reduced efficiency
		522	as those tend to return 0 or 1 as link counts, which disables the
		523	directory counting heuristic.
289		524
290	=cut	525	=cut
291		526
292	sub aio_scandir($$$) {	527	sub aio_scandir($$$) {
293	my ($path, $maxreq, $cb) = @_;	528	my ($path, $maxreq, $cb) = @_;
294		529
		530	my $pri = aioreq_pri;
		531
		532	my $grp = aio_group $cb;
		533
295	$maxreq = 8 if $maxreq <= 0;	534	$maxreq = 4 if $maxreq <= 0;
296		535
297	# stat once	536	# stat once
		537	aioreq_pri $pri;
298	aio_stat $path, sub {	538	add $grp aio_stat $path, sub {
299	$cb->() if $_[0];	539	return $grp->result () if $_[0];
		540	my $now = time;
300	my $hash1 = join ":", (stat _)[0,1,3,7,9];	541	my $hash1 = join ":", (stat _)[0,1,3,7,9];
301		542
302	# read the directory entries	543	# read the directory entries
		544	aioreq_pri $pri;
303	aio_readdir $path, sub {	545	add $grp aio_readdir $path, sub {
304	my $entries = shift	546	my $entries = shift
305	or return $cb->();	547	or return $grp->result ();
306		548
307	# stat the dir another time	549	# stat the dir another time
		550	aioreq_pri $pri;
308	aio_stat $path, sub {	551	add $grp aio_stat $path, sub {
309	my $hash2 = join ":", (stat _)[0,1,3,7,9];	552	my $hash2 = join ":", (stat _)[0,1,3,7,9];
310		553
311	my $ndirs;	554	my $ndirs;
312		555
313	# take the slow route if anything looks fishy	556	# take the slow route if anything looks fishy
314	if ($hash1 ne $hash2) {	557	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
315	$ndirs = -1;	558	$ndirs = -1;
316	} else {	559	} else {
317	# if nlink == 2, we are finished	560	# if nlink == 2, we are finished
318	# on non-posix-fs's, we rely on nlink < 2	561	# on non-posix-fs's, we rely on nlink < 2
319	$ndirs = (stat _)[3] - 2	562	$ndirs = (stat _)[3] - 2
320	or $cb->([], $entries);	563	or return $grp->result ([], $entries);
321	}	564	}
322		565
323	# sort into likely dirs and likely nondirs	566	# sort into likely dirs and likely nondirs
324	# dirs == files without ".", short entries first	567	# dirs == files without ".", short entries first
325	$entries = [map $_->[0],	568	$entries = [map $_->[0],
…		…
327	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	570	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
328	@$entries];	571	@$entries];
329		572
330	my (@dirs, @nondirs);	573	my (@dirs, @nondirs);
331		574
332	my ($statcb, $schedcb);	575	my $statgrp = add $grp aio_group sub {
333	my $nreq = 0;	576	$grp->result (\@dirs, \@nondirs);
		577	};
334		578
335	$schedcb = sub {	579	limit $statgrp $maxreq;
336	if (@$entries) {	580	feed $statgrp sub {
337	if ($nreq < $maxreq) {	581	return unless @$entries;
338	my $ent = pop @$entries;	582	my $entry = pop @$entries;
		583
		584	aioreq_pri $pri;
		585	add $statgrp aio_stat "$path/$entry/.", sub {
		586	if ($_[0] < 0) {
		587	push @nondirs, $entry;
		588	} else {
		589	# need to check for real directory
		590	aioreq_pri $pri;
		591	add $statgrp aio_lstat "$path/$entry", sub {
		592	if (-d _) {
		593	push @dirs, $entry;
		594
		595	unless (--$ndirs) {
		596	push @nondirs, @$entries;
		597	feed $statgrp;
		598	}
		599	} else {
		600	push @nondirs, $entry;
		601	}
339	$nreq++;	602	}
340	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
341	}	603	}
342	} elsif (!$nreq) {
343	# finished
344	undef $statcb;
345	undef $schedcb;
346	$cb->(\@dirs, \@nondirs);
347	undef $cb;
348	}	604	};
349	};	605	};
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	};	606	};
380	};	607	};
381	};	608	};
		609
		610	$grp
382	}	611	}
383		612
384	=item aio_fsync $fh, $callback->($status)	613	=item aio_fsync $fh, $callback->($status)
385		614
386	Asynchronously call fsync on the given filehandle and call the callback	615	Asynchronously call fsync on the given filehandle and call the callback
…		…
391	Asynchronously call fdatasync on the given filehandle and call the	620	Asynchronously call fdatasync on the given filehandle and call the
392	callback with the fdatasync result code.	621	callback with the fdatasync result code.
393		622
394	If this call isn't available because your OS lacks it or it couldn't be	623	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.	624	detected, it will be emulated by calling C<fsync> instead.
		625
		626	=item aio_group $callback->(...)
		627
		628	This is a very special aio request: Instead of doing something, it is a
		629	container for other aio requests, which is useful if you want to bundle
		630	many requests into a single, composite, request with a definite callback
		631	and the ability to cancel the whole request with its subrequests.
		632
		633	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		634	for more info.
		635
		636	Example:
		637
		638	my $grp = aio_group sub {
		639	print "all stats done\n";
		640	};
		641
		642	add $grp
		643	(aio_stat ...),
		644	(aio_stat ...),
		645	...;
		646
		647	=item aio_nop $callback->()
		648
		649	This is a special request - it does nothing in itself and is only used for
		650	side effects, such as when you want to add a dummy request to a group so
		651	that finishing the requests in the group depends on executing the given
		652	code.
		653
		654	While this request does nothing, it still goes through the execution
		655	phase and still requires a worker thread. Thus, the callback will not
		656	be executed immediately but only after other requests in the queue have
		657	entered their execution phase. This can be used to measure request
		658	latency.
		659
		660	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		661
		662	Mainly used for debugging and benchmarking, this aio request puts one of
		663	the request workers to sleep for the given time.
		664
		665	While it is theoretically handy to have simple I/O scheduling requests
		666	like sleep and file handle readable/writable, the overhead this creates is
		667	immense (it blocks a thread for a long time) so do not use this function
		668	except to put your application under artificial I/O pressure.
		669
		670	=back
		671
		672	=head2 IO::AIO::REQ CLASS
		673
		674	All non-aggregate C<aio_*> functions return an object of this class when
		675	called in non-void context.
		676
		677	=over 4
		678
		679	=item cancel $req
		680
		681	Cancels the request, if possible. Has the effect of skipping execution
		682	when entering the B<execute> state and skipping calling the callback when
		683	entering the the B<result> state, but will leave the request otherwise
		684	untouched. That means that requests that currently execute will not be
		685	stopped and resources held by the request will not be freed prematurely.
		686
		687	=item cb $req $callback->(...)
		688
		689	Replace (or simply set) the callback registered to the request.
		690
		691	=back
		692
		693	=head2 IO::AIO::GRP CLASS
		694
		695	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		696	objects of this class, too.
		697
		698	A IO::AIO::GRP object is a special request that can contain multiple other
		699	aio requests.
		700
		701	You create one by calling the C<aio_group> constructing function with a
		702	callback that will be called when all contained requests have entered the
		703	C<done> state:
		704
		705	my $grp = aio_group sub {
		706	print "all requests are done\n";
		707	};
		708
		709	You add requests by calling the C<add> method with one or more
		710	C<IO::AIO::REQ> objects:
		711
		712	$grp->add (aio_unlink "...");
		713
		714	add $grp aio_stat "...", sub {
		715	$_[0] or return $grp->result ("error");
		716
		717	# add another request dynamically, if first succeeded
		718	add $grp aio_open "...", sub {
		719	$grp->result ("ok");
		720	};
		721	};
		722
		723	This makes it very easy to create composite requests (see the source of
		724	C<aio_move> for an application) that work and feel like simple requests.
		725
		726	=over 4
		727
		728	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		729	C<IO::AIO::poll_cb>, just like any other request.
		730
		731	=item * They can be canceled like any other request. Canceling will cancel not
		732	only the request itself, but also all requests it contains.
		733
		734	=item * They can also can also be added to other IO::AIO::GRP objects.
		735
		736	=item * You must not add requests to a group from within the group callback (or
		737	any later time).
		738
		739	=back
		740
		741	Their lifetime, simplified, looks like this: when they are empty, they
		742	will finish very quickly. If they contain only requests that are in the
		743	C<done> state, they will also finish. Otherwise they will continue to
		744	exist.
		745
		746	That means after creating a group you have some time to add requests. And
		747	in the callbacks of those requests, you can add further requests to the
		748	group. And only when all those requests have finished will the the group
		749	itself finish.
		750
		751	=over 4
		752
		753	=item add $grp ...
		754
		755	=item $grp->add (...)
		756
		757	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		758	be added, including other groups, as long as you do not create circular
		759	dependencies.
		760
		761	Returns all its arguments.
		762
		763	=item $grp->cancel_subs
		764
		765	Cancel all subrequests and clears any feeder, but not the group request
		766	itself. Useful when you queued a lot of events but got a result early.
		767
		768	=item $grp->result (...)
		769
		770	Set the result value(s) that will be passed to the group callback when all
		771	subrequests have finished and set thre groups errno to the current value
		772	of errno (just like calling C<errno> without an error number). By default,
		773	no argument will be passed and errno is zero.
		774
		775	=item $grp->errno ([$errno])
		776
		777	Sets the group errno value to C<$errno>, or the current value of errno
		778	when the argument is missing.
		779
		780	Every aio request has an associated errno value that is restored when
		781	the callback is invoked. This method lets you change this value from its
		782	default (0).
		783
		784	Calling C<result> will also set errno, so make sure you either set C<$!>
		785	before the call to C<result>, or call c<errno> after it.
		786
		787	=item feed $grp $callback->($grp)
		788
		789	Sets a feeder/generator on this group: every group can have an attached
		790	generator that generates requests if idle. The idea behind this is that,
		791	although you could just queue as many requests as you want in a group,
		792	this might starve other requests for a potentially long time. For
		793	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		794	requests, delaying any later requests for a long time.
		795
		796	To avoid this, and allow incremental generation of requests, you can
		797	instead a group and set a feeder on it that generates those requests. The
		798	feed callback will be called whenever there are few enough (see C<limit>,
		799	below) requests active in the group itself and is expected to queue more
		800	requests.
		801
		802	The feed callback can queue as many requests as it likes (i.e. C<add> does
		803	not impose any limits).
		804
		805	If the feed does not queue more requests when called, it will be
		806	automatically removed from the group.
		807
		808	If the feed limit is C<0>, it will be set to C<2> automatically.
		809
		810	Example:
		811
		812	# stat all files in @files, but only ever use four aio requests concurrently:
		813
		814	my $grp = aio_group sub { print "finished\n" };
		815	limit $grp 4;
		816	feed $grp sub {
		817	my $file = pop @files
		818	or return;
		819
		820	add $grp aio_stat $file, sub { ... };
		821	};
		822
		823	=item limit $grp $num
		824
		825	Sets the feeder limit for the group: The feeder will be called whenever
		826	the group contains less than this many requests.
		827
		828	Setting the limit to C<0> will pause the feeding process.
396		829
397	=back	830	=back
398		831
399	=head2 SUPPORT FUNCTIONS	832	=head2 SUPPORT FUNCTIONS
400		833
…		…
413		846
414	Process all outstanding events on the result pipe. You have to call this	847	Process all outstanding events on the result pipe. You have to call this
415	regularly. Returns the number of events processed. Returns immediately	848	regularly. Returns the number of events processed. Returns immediately
416	when no events are outstanding.	849	when no events are outstanding.
417		850
		851	If not all requests were processed for whatever reason, the filehandle
		852	will still be ready when C<poll_cb> returns.
		853
418	Example: Install an Event watcher that automatically calls	854	Example: Install an Event watcher that automatically calls
419	IO::AIO::poll_cb with high priority:	855	IO::AIO::poll_cb with high priority:
420		856
421	Event->io (fd => IO::AIO::poll_fileno,	857	Event->io (fd => IO::AIO::poll_fileno,
422	poll => 'r', async => 1,	858	poll => 'r', async => 1,
423	cb => \&IO::AIO::poll_cb);	859	cb => \&IO::AIO::poll_cb);
424		860
		861	=item IO::AIO::poll_some $max_requests
		862
		863	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests
		864	at a time.
		865
		866	Useful if you want to ensure some level of interactiveness when perl is
		867	not fast enough to process all requests in time.
		868
		869	Example: Install an Event watcher that automatically calls
		870	IO::AIO::poll_some with low priority, to ensure that other parts of the
		871	program get the CPU sometimes even under high AIO load.
		872
		873	Event->io (fd => IO::AIO::poll_fileno,
		874	poll => 'r', nice => 1,
		875	cb => sub { IO::AIO::poll_some 256 });
		876
425	=item IO::AIO::poll_wait	877	=item IO::AIO::poll_wait
426		878
427	Wait till the result filehandle becomes ready for reading (simply does a	879	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	880	C<select> on the filehandle. This is useful if you want to synchronously wait
429	for some requests to finish).	881	for some requests to finish).
430		882
431	See C<nreqs> for an example.	883	See C<nreqs> for an example.
432		884
433	=item IO::AIO::nreqs	885	=item IO::AIO::nreqs
434		886
435	Returns the number of requests currently outstanding (i.e. for which their	887	Returns the number of requests currently in the ready, execute or pending
436	callback has not been invoked yet).	888	states (i.e. for which their callback has not been invoked yet).
437		889
438	Example: wait till there are no outstanding requests anymore:	890	Example: wait till there are no outstanding requests anymore:
439		891
440	IO::AIO::poll_wait, IO::AIO::poll_cb	892	IO::AIO::poll_wait, IO::AIO::poll_cb
441	while IO::AIO::nreqs;	893	while IO::AIO::nreqs;
442		894
		895	=item IO::AIO::nready
		896
		897	Returns the number of requests currently in the ready state (not yet
		898	executed).
		899
		900	=item IO::AIO::npending
		901
		902	Returns the number of requests currently in the pending state (executed,
		903	but not yet processed by poll_cb).
		904
443	=item IO::AIO::flush	905	=item IO::AIO::flush
444		906
445	Wait till all outstanding AIO requests have been handled.	907	Wait till all outstanding AIO requests have been handled.
446		908
447	Strictly equivalent to:	909	Strictly equivalent to:
…		…
458	IO::AIO::poll_wait, IO::AIO::poll_cb	920	IO::AIO::poll_wait, IO::AIO::poll_cb
459	if IO::AIO::nreqs;	921	if IO::AIO::nreqs;
460		922
461	=item IO::AIO::min_parallel $nthreads	923	=item IO::AIO::min_parallel $nthreads
462		924
463	Set the minimum number of AIO threads to C<$nthreads>. The current default	925	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	926	default is C<8>, which means eight asynchronous operations can execute
465	(the number of outstanding operations, however, is unlimited).	927	concurrently at any one time (the number of outstanding requests,
		928	however, is unlimited).
466		929
467	IO::AIO starts threads only on demand, when an AIO request is queued and	930	IO::AIO starts threads only on demand, when an AIO request is queued and
468	no free thread exists.	931	no free thread exists.
469		932
470	It is recommended to keep the number of threads low, as some Linux	933	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	934	Linux kernel versions will scale negatively with the number of threads
472	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	935	(higher parallelity => MUCH higher latency). With current Linux 2.6
473	threads should be fine.	936	versions, 4-32 threads should be fine.
474		937
475	Under most circumstances you don't need to call this function, as the	938	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.	939	module selects a default that is suitable for low to moderate load.
477		940
478	=item IO::AIO::max_parallel $nthreads	941	=item IO::AIO::max_parallel $nthreads
…		…
487	This module automatically runs C<max_parallel 0> at program end, to ensure	950	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.	951	that all threads are killed and that there are no outstanding requests.
489		952
490	Under normal circumstances you don't need to call this function.	953	Under normal circumstances you don't need to call this function.
491		954
492	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	955	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		956
		957	This is a very bad function to use in interactive programs because it
		958	blocks, and a bad way to reduce concurrency because it is inexact: Better
		959	use an C<aio_group> together with a feed callback.
493		960
494	Sets the maximum number of outstanding requests to C<$nreqs>. If you	961	Sets the maximum number of outstanding requests to C<$nreqs>. If you
495	try to queue up more than this number of requests, the caller will block until	962	to queue up more than this number of requests, the next call to the
496	some requests have been handled.	963	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		964	function will block until the limit is no longer exceeded.
497		965
498	The default is very large, so normally there is no practical limit. If you	966	The default value is very large, so there is no practical limit on the
499	queue up many requests in a loop it often improves speed if you set	967	number of outstanding requests.
500	this to a relatively low number, such as C<100>.
501		968
502	Under normal circumstances you don't need to call this function.	969	You can still queue as many requests as you want. Therefore,
		970	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		971	as a stop gap to shield against fatal memory overflow (with large values).
503		972
504	=back	973	=back
505		974
506	=cut	975	=cut
507		976
…		…
519	or return undef;	988	or return undef;
520		989
521	*$sym	990	*$sym
522	}	991	}
523		992
524	min_parallel 4;	993	min_parallel 8;
525		994
526	END {	995	END {
527	max_parallel 0;	996	flush;
528	}	997	};
529		998
530	1;	999	1;
531		1000
532	=head2 FORK BEHAVIOUR	1001	=head2 FORK BEHAVIOUR
		1002
		1003	This module should do "the right thing" when the process using it forks:
533		1004
534	Before the fork, IO::AIO enters a quiescent state where no requests	1005	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	1006	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	1007	the fork the parent simply leaves the quiescent state and continues
537	request/result processing, while the child clears the request/result	1008	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	1009	(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	1010	parent). Threads will be started on demand until the limit set in the
540	parent process has been reached again.	1011	parent process has been reached again.
541		1012
		1013	In short: the parent will, after a short pause, continue as if fork had
		1014	not been called, while the child will act as if IO::AIO has not been used
		1015	yet.
		1016
		1017	=head2 MEMORY USAGE
		1018
		1019	Per-request usage:
		1020
		1021	Each aio request uses - depending on your architecture - around 100-200
		1022	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1023	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1024	scalars and other data passed into aio requests will also be locked and
		1025	will consume memory till the request has entered the done state.
		1026
		1027	This is now awfully much, so queuing lots of requests is not usually a
		1028	problem.
		1029
		1030	Per-thread usage:
		1031
		1032	In the execution phase, some aio requests require more memory for
		1033	temporary buffers, and each thread requires a stack and other data
		1034	structures (usually around 16k-128k, depending on the OS).
		1035
		1036	=head1 KNOWN BUGS
		1037
		1038	Known bugs will be fixed in the next release.
		1039
542	=head1 SEE ALSO	1040	=head1 SEE ALSO
543		1041
544	L<Coro>, L<Linux::AIO>.	1042	L<Coro::AIO>.
545		1043
546	=head1 AUTHOR	1044	=head1 AUTHOR
547		1045
548	Marc Lehmann <schmorp@schmorp.de>	1046	Marc Lehmann <schmorp@schmorp.de>
549	http://home.schmorp.de/	1047	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.41 by root, Wed Sep 7 17:41:17 2005 UTC vs. Revision 1.83 by root, Fri Oct 27 20:11:58 2006 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.41 by root, Wed Sep 7 17:41:17 2005 UTC vs.
Revision 1.83 by root, Fri Oct 27 20:11:58 2006 UTC