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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.44 by root, Mon Dec 26 18:31:12 2005 UTC vs.
Revision 1.67 by root, Tue Oct 24 02:25:16 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	my $req = aio_unlink "/tmp/file", sub { };
		24	$req->cancel; # cancel request if still in queue
		25
		26	my $grp = aio_group sub { print "all stats done\n" };
		27	add $grp aio_stat "..." for ...;
		28
		29	# AnyEvent integration
21	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	30	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
22	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });	31	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
23		32
24	# Event	33	# Event integration
25	Event->io (fd => IO::AIO::poll_fileno,	34	Event->io (fd => IO::AIO::poll_fileno,
26	poll => 'r',	35	poll => 'r',
27	cb => \&IO::AIO::poll_cb);	36	cb => \&IO::AIO::poll_cb);
28		37
29	# Glib/Gtk2	38	# Glib/Gtk2 integration
30	add_watch Glib::IO IO::AIO::poll_fileno,	39	add_watch Glib::IO IO::AIO::poll_fileno,
31	in => sub { IO::AIO::poll_cb; 1 };	40	in => sub { IO::AIO::poll_cb; 1 };
32		41
33	# Tk	42	# Tk integration
34	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	43	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
35	readable => \&IO::AIO::poll_cb);	44	readable => \&IO::AIO::poll_cb);
36		45
37	# Danga::Socket	46	# Danga::Socket integration
38	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	47	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
39	\&IO::AIO::poll_cb);	48	\&IO::AIO::poll_cb);
40		49
41
42	=head1 DESCRIPTION	50	=head1 DESCRIPTION
43		51
44	This module implements asynchronous I/O using whatever means your	52	This module implements asynchronous I/O using whatever means your
45	operating system supports.	53	operating system supports.
46		54
47	Currently, a number of threads are started that execute your read/writes	55	Currently, a number of threads are started that execute your read/writes
48	and signal their completion. You don't need thread support in your libc or	56	and signal their completion. You don't need thread support in perl, and
49	perl, and the threads created by this module will not be visible to the	57	the threads created by this module will not be visible to perl. In the
50	pthreads library. In the future, this module might make use of the native	58	future, this module might make use of the native aio functions available
51	aio functions available on many operating systems. However, they are often	59	on many operating systems. However, they are often not well-supported
52	not well-supported (Linux doesn't allow them on normal files currently,	60	(Linux doesn't allow them on normal files currently, for example),
53	for example), and they would only support aio_read and aio_write, so the	61	and they would only support aio_read and aio_write, so the remaining
54	remaining functionality would have to be implemented using threads anyway.	62	functionality would have to be implemented using threads anyway.
55		63
56	Although the module will work with in the presence of other threads, it is	64	Although the module will work with in the presence of other threads, it is
57	currently not reentrant, so use appropriate locking yourself, always call	65	currently not reentrant, so use appropriate locking yourself, always call
58	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	66	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other
59	C<aio_> functions) recursively.	67	C<aio_> functions) recursively.
…		…
61	=cut	69	=cut
62		70
63	package IO::AIO;	71	package IO::AIO;
64		72
65	no warnings;	73	no warnings;
		74	use strict 'vars';
66		75
67	use base 'Exporter';	76	use base 'Exporter';
68		77
69	use Fcntl ();
70
71	BEGIN {	78	BEGIN {
72	$VERSION = '1.7';	79	our $VERSION = '2.0';
73		80
74	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	81	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	82	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
76	aio_fsync aio_fdatasync aio_readahead);	83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
77	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	84	aio_group aio_nop);
78	max_outstanding nreqs);	85	our @EXPORT = (@AIO_REQ, qw(aioreq_pri));
		86	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		87	min_parallel max_parallel max_outstanding nreqs);
		88
		89	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
79		90
80	require XSLoader;	91	require XSLoader;
81	XSLoader::load IO::AIO, $VERSION;	92	XSLoader::load ("IO::AIO", $VERSION);
82	}	93	}
83		94
84	=head1 FUNCTIONS	95	=head1 FUNCTIONS
85		96
86	=head2 AIO FUNCTIONS	97	=head2 AIO FUNCTIONS
…		…
94	syscall has been executed asynchronously.	105	syscall has been executed asynchronously.
95		106
96	All functions expecting a filehandle keep a copy of the filehandle	107	All functions expecting a filehandle keep a copy of the filehandle
97	internally until the request has finished.	108	internally until the request has finished.
98		109
		110	All requests return objects of type L<IO::AIO::REQ> that allow further
		111	manipulation of those requests while they are in-flight.
		112
99	The pathnames you pass to these routines I<must> be absolute and	113	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	114	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	115	request is being executed, the current working directory could have
102	changed. Alternatively, you can make sure that you never change the	116	changed. Alternatively, you can make sure that you never change the
103	current working directory.	117	current working directory.
…		…
167		181
168	aio_read $fh, 7, 15, $buffer, 0, sub {	182	aio_read $fh, 7, 15, $buffer, 0, sub {
169	$_[0] > 0 or die "read error: $!";	183	$_[0] > 0 or die "read error: $!";
170	print "read $_[0] bytes: <$buffer>\n";	184	print "read $_[0] bytes: <$buffer>\n";
171	};	185	};
		186
		187	=item aio_move $srcpath, $dstpath, $callback->($status)
		188
		189	[EXPERIMENTAL due to internal aio_group use]
		190
		191	Try to move the I<file> (directories not supported as either source or
		192	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		193	the C<0> (error) or C<-1> ok.
		194
		195	This is a composite request that tries to rename(2) the file first. If
		196	rename files with C<EXDEV>, it creates the destination file with mode 0200
		197	and copies the contents of the source file into it using C<aio_sendfile>,
		198	followed by restoring atime, mtime, access mode and uid/gid, in that
		199	order, and unlinking the C<$srcpath>.
		200
		201	If an error occurs, the partial destination file will be unlinked, if
		202	possible, except when setting atime, mtime, access mode and uid/gid, where
		203	errors are being ignored.
		204
		205	=cut
		206
		207	sub aio_move($$$) {
		208	my ($src, $dst, $cb) = @_;
		209
		210	my $grp = aio_group $cb;
		211
		212	add $grp aio_rename $src, $dst, sub {
		213	if ($_[0] && $! == EXDEV) {
		214	add $grp aio_open $src, O_RDONLY, 0, sub {
		215	if (my $src_fh = $_[0]) {
		216	my @stat = stat $src_fh;
		217
		218	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		219	if (my $dst_fh = $_[0]) {
		220	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		221	close $src_fh;
		222
		223	if ($_[0] == $stat[7]) {
		224	utime $stat[8], $stat[9], $dst;
		225	chmod $stat[2] & 07777, $dst_fh;
		226	chown $stat[4], $stat[5], $dst_fh;
		227	close $dst_fh;
		228
		229	add $grp aio_unlink $src, sub {
		230	$grp->result ($_[0]);
		231	};
		232	} else {
		233	my $errno = $!;
		234	add $grp aio_unlink $dst, sub {
		235	$! = $errno;
		236	$grp->result (-1);
		237	};
		238	}
		239	};
		240	} else {
		241	$grp->result (-1);
		242	}
		243	},
		244
		245	} else {
		246	$grp->result (-1);
		247	}
		248	};
		249	} else {
		250	$grp->result ($_[0]);
		251	}
		252	};
		253
		254	$grp
		255	}
172		256
173	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	257	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
174		258
175	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	259	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	260	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
232	=item aio_unlink $pathname, $callback->($status)	316	=item aio_unlink $pathname, $callback->($status)
233		317
234	Asynchronously unlink (delete) a file and call the callback with the	318	Asynchronously unlink (delete) a file and call the callback with the
235	result code.	319	result code.
236		320
		321	=item aio_link $srcpath, $dstpath, $callback->($status)
		322
		323	Asynchronously create a new link to the existing object at C<$srcpath> at
		324	the path C<$dstpath> and call the callback with the result code.
		325
		326	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		327
		328	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		329	the path C<$dstpath> and call the callback with the result code.
		330
		331	=item aio_rename $srcpath, $dstpath, $callback->($status)
		332
		333	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		334	rename(2) and call the callback with the result code.
		335
237	=item aio_rmdir $pathname, $callback->($status)	336	=item aio_rmdir $pathname, $callback->($status)
238		337
239	Asynchronously rmdir (delete) a directory and call the callback with the	338	Asynchronously rmdir (delete) a directory and call the callback with the
240	result code.	339	result code.
241		340
242	=item aio_readdir $pathname $callback->($entries)	341	=item aio_readdir $pathname, $callback->($entries)
243		342
244	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	343	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	344	directory (i.e. opendir + readdir + closedir). The entries will not be
246	sorted, and will B<NOT> include the C<.> and C<..> entries.	345	sorted, and will B<NOT> include the C<.> and C<..> entries.
247		346
248	The callback a single argument which is either C<undef> or an array-ref	347	The callback a single argument which is either C<undef> or an array-ref
249	with the filenames.	348	with the filenames.
250		349
251	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	350	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
252		351
		352	[EXPERIMENTAL due to internal aio_group use]
		353
253	Scans a directory (similar to C<aio_readdir>) and tries to separate the	354	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	355	separate the entries of directory C<$path> into two sets of names, ones
255	into (directories), and ones you cannot recurse into (everything else).	356	you can recurse into (directories or links to them), and ones you cannot
		357	recurse into (everything else).
256		358
257	C<aio_scandir> is a composite request that consists of many	359	C<aio_scandir> is a composite request that creates of many sub requests_
258	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	360	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	361	this function generates. If it is C<< <= 0 >>, then a suitable default
260	suitable default will be chosen (currently 8).	362	will be chosen (currently 6).
261		363
262	On error, the callback is called without arguments, otherwise it receives	364	On error, the callback is called without arguments, otherwise it receives
263	two array-refs with path-relative entry names.	365	two array-refs with path-relative entry names.
264		366
265	Example:	367	Example:
…		…
273	Implementation notes.	375	Implementation notes.
274		376
275	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	377	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
276		378
277	After reading the directory, the modification time, size etc. of the	379	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	380	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	381	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	382	entries are directories (if >= 2). Otherwise, no knowledge of the number
281	assumed.	383	of subdirectories will be assumed.
282		384
283	Then entires will be sorted into likely directories (everything without a	385	Then entries will be sorted into likely directories (everything without
284	non-initial dot) and likely non-directories (everything else). Then every	386	a non-initial dot currently) and likely non-directories (everything
285	entry + C</.> will be C<stat>'ed, likely directories first. This is often	387	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		388	likely directories first. If that succeeds, it assumes that the entry
		389	is a directory or a symlink to directory (which will be checked
		390	seperately). This is often faster than stat'ing the entry itself because
286	faster because filesystems might detect the type of the entry without	391	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,	392	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		393
291	If the known number of directories has been reached, the rest of the	394	If the known number of directories (link count - 2) has been reached, the
292	entries is assumed to be non-directories.	395	rest of the entries is assumed to be non-directories.
		396
		397	This only works with certainty on POSIX (= UNIX) filesystems, which
		398	fortunately are the vast majority of filesystems around.
		399
		400	It will also likely work on non-POSIX filesystems with reduced efficiency
		401	as those tend to return 0 or 1 as link counts, which disables the
		402	directory counting heuristic.
293		403
294	=cut	404	=cut
295		405
296	sub aio_scandir($$$) {	406	sub aio_scandir($$$) {
297	my ($path, $maxreq, $cb) = @_;	407	my ($path, $maxreq, $cb) = @_;
298		408
		409	my $grp = aio_group $cb;
		410
299	$maxreq = 8 if $maxreq <= 0;	411	$maxreq = 6 if $maxreq <= 0;
300		412
301	# stat once	413	# stat once
302	aio_stat $path, sub {	414	add $grp aio_stat $path, sub {
303	$cb->() if $_[0];	415	return $grp->result () if $_[0];
		416	my $now = time;
304	my $hash1 = join ":", (stat _)[0,1,3,7,9];	417	my $hash1 = join ":", (stat _)[0,1,3,7,9];
305		418
306	# read the directory entries	419	# read the directory entries
307	aio_readdir $path, sub {	420	add $grp aio_readdir $path, sub {
308	my $entries = shift	421	my $entries = shift
309	or return $cb->();	422	or return $grp->result ();
310		423
311	# stat the dir another time	424	# stat the dir another time
312	aio_stat $path, sub {	425	add $grp aio_stat $path, sub {
313	my $hash2 = join ":", (stat _)[0,1,3,7,9];	426	my $hash2 = join ":", (stat _)[0,1,3,7,9];
314		427
315	my $ndirs;	428	my $ndirs;
316		429
317	# take the slow route if anything looks fishy	430	# take the slow route if anything looks fishy
318	if ($hash1 ne $hash2) {	431	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
319	$ndirs = -1;	432	$ndirs = -1;
320	} else {	433	} else {
321	# if nlink == 2, we are finished	434	# if nlink == 2, we are finished
322	# on non-posix-fs's, we rely on nlink < 2	435	# on non-posix-fs's, we rely on nlink < 2
323	$ndirs = (stat _)[3] - 2	436	$ndirs = (stat _)[3] - 2
324	or return $cb->([], $entries);	437	or return $grp->result ([], $entries);
325	}	438	}
326		439
327	# sort into likely dirs and likely nondirs	440	# sort into likely dirs and likely nondirs
328	# dirs == files without ".", short entries first	441	# dirs == files without ".", short entries first
329	$entries = [map $_->[0],	442	$entries = [map $_->[0],
…		…
334	my (@dirs, @nondirs);	447	my (@dirs, @nondirs);
335		448
336	my ($statcb, $schedcb);	449	my ($statcb, $schedcb);
337	my $nreq = 0;	450	my $nreq = 0;
338		451
		452	my $statgrp = add $grp aio_group;
		453
339	$schedcb = sub {	454	$schedcb = sub {
340	if (@$entries) {	455	if (@$entries) {
341	if ($nreq < $maxreq) {	456	if ($nreq < $maxreq) {
342	my $ent = pop @$entries;	457	my $ent = pop @$entries;
343	$nreq++;	458	$nreq++;
344	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };	459	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
345	}	460	}
346	} elsif (!$nreq) {	461	} elsif (!$nreq) {
347	# finished	462	# finished
		463	$statgrp->cancel;
348	undef $statcb;	464	undef $statcb;
349	undef $schedcb;	465	undef $schedcb;
350	$cb->(\@dirs, \@nondirs);	466	$grp->result (\@dirs, \@nondirs);
351	undef $cb;
352	}	467	}
353	};	468	};
354	$statcb = sub {	469	$statcb = sub {
355	my ($status, $entry) = @_;	470	my ($status, $entry) = @_;
356		471
…		…
358	$nreq--;	473	$nreq--;
359	push @nondirs, $entry;	474	push @nondirs, $entry;
360	&$schedcb;	475	&$schedcb;
361	} else {	476	} else {
362	# need to check for real directory	477	# need to check for real directory
363	aio_lstat "$path/$entry", sub {	478	add $grp aio_lstat "$path/$entry", sub {
364	$nreq--;	479	$nreq--;
365		480
366	if (-d _) {	481	if (-d _) {
367	push @dirs, $entry;	482	push @dirs, $entry;
368		483
…		…
381		496
382	&$schedcb while @$entries && $nreq < $maxreq;	497	&$schedcb while @$entries && $nreq < $maxreq;
383	};	498	};
384	};	499	};
385	};	500	};
		501
		502	$grp
386	}	503	}
387		504
388	=item aio_fsync $fh, $callback->($status)	505	=item aio_fsync $fh, $callback->($status)
389		506
390	Asynchronously call fsync on the given filehandle and call the callback	507	Asynchronously call fsync on the given filehandle and call the callback
…		…
395	Asynchronously call fdatasync on the given filehandle and call the	512	Asynchronously call fdatasync on the given filehandle and call the
396	callback with the fdatasync result code.	513	callback with the fdatasync result code.
397		514
398	If this call isn't available because your OS lacks it or it couldn't be	515	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.	516	detected, it will be emulated by calling C<fsync> instead.
		517
		518	=item aio_group $callback->(...)
		519
		520	[EXPERIMENTAL]
		521
		522	This is a very special aio request: Instead of doing something, it is a
		523	container for other aio requests, which is useful if you want to bundle
		524	many requests into a single, composite, request.
		525
		526	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		527	for more info.
		528
		529	Example:
		530
		531	my $grp = aio_group sub {
		532	print "all stats done\n";
		533	};
		534
		535	add $grp
		536	(aio_stat ...),
		537	(aio_stat ...),
		538	...;
		539
		540	=item aio_nop $callback->()
		541
		542	This is a special request - it does nothing in itself and is only used for
		543	side effects, such as when you want to add a dummy request to a group so
		544	that finishing the requests in the group depends on executing the given
		545	code.
		546
		547	While this request does nothing, it still goes through the execution
		548	phase and still requires a worker thread. Thus, the callback will not
		549	be executed immediately but only after other requests in the queue have
		550	entered their execution phase. This can be used to measure request
		551	latency.
		552
		553	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		554
		555	Mainly used for debugging and benchmarking, this aio request puts one of
		556	the request workers to sleep for the given time.
		557
		558	While it is theoretically handy to have simple I/O scheduling requests
		559	like sleep and file handle readable/writable, the overhead this creates
		560	is immense, so do not use this function except to put your application
		561	under artificial I/O pressure.
		562
		563	=back
		564
		565	=head2 IO::AIO::REQ CLASS
		566
		567	All non-aggregate C<aio_*> functions return an object of this class when
		568	called in non-void context.
		569
		570	A request always moves through the following five states in its lifetime,
		571	in order: B<ready> (request has been created, but has not been executed
		572	yet), B<execute> (request is currently being executed), B<pending>
		573	(request has been executed but callback has not been called yet),
		574	B<result> (results are being processed synchronously, includes calling the
		575	callback) and B<done> (request has reached the end of its lifetime and
		576	holds no resources anymore).
		577
		578	=over 4
		579
		580	=item cancel $req
		581
		582	Cancels the request, if possible. Has the effect of skipping execution
		583	when entering the B<execute> state and skipping calling the callback when
		584	entering the the B<result> state, but will leave the request otherwise
		585	untouched. That means that requests that currently execute will not be
		586	stopped and resources held by the request will not be freed prematurely.
		587
		588	=item cb $req $callback->(...)
		589
		590	Replace (or simply set) the callback registered to the request.
		591
		592	=back
		593
		594	=head2 IO::AIO::GRP CLASS
		595
		596	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		597	objects of this class, too.
		598
		599	A IO::AIO::GRP object is a special request that can contain multiple other
		600	aio requests.
		601
		602	You create one by calling the C<aio_group> constructing function with a
		603	callback that will be called when all contained requests have entered the
		604	C<done> state:
		605
		606	my $grp = aio_group sub {
		607	print "all requests are done\n";
		608	};
		609
		610	You add requests by calling the C<add> method with one or more
		611	C<IO::AIO::REQ> objects:
		612
		613	$grp->add (aio_unlink "...");
		614
		615	add $grp aio_stat "...", sub {
		616	$_[0] or return $grp->result ("error");
		617
		618	# add another request dynamically, if first succeeded
		619	add $grp aio_open "...", sub {
		620	$grp->result ("ok");
		621	};
		622	};
		623
		624	This makes it very easy to create composite requests (see the source of
		625	C<aio_move> for an application) that work and feel like simple requests.
		626
		627	=over 4
		628
		629	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		630	C<IO::AIO::poll_cb>, just like any other request.
		631
		632	=item * They can be canceled like any other request. Canceling will cancel not
		633	only the request itself, but also all requests it contains.
		634
		635	=item * They can also can also be added to other IO::AIO::GRP objects.
		636
		637	=item * You must not add requests to a group from within the group callback (or
		638	any later time).
		639
		640	=item * This does not harmonise well with C<max_outstanding>, so best do
		641	not combine C<aio_group> with it. Groups and feeders are recommended for
		642	this kind of concurrency-limiting.
		643
		644	=back
		645
		646	Their lifetime, simplified, looks like this: when they are empty, they
		647	will finish very quickly. If they contain only requests that are in the
		648	C<done> state, they will also finish. Otherwise they will continue to
		649	exist.
		650
		651	That means after creating a group you have some time to add requests. And
		652	in the callbacks of those requests, you can add further requests to the
		653	group. And only when all those requests have finished will the the group
		654	itself finish.
		655
		656	=over 4
		657
		658	=item add $grp ...
		659
		660	=item $grp->add (...)
		661
		662	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		663	be added, including other groups, as long as you do not create circular
		664	dependencies.
		665
		666	Returns all its arguments.
		667
		668	=item $grp->result (...)
		669
		670	Set the result value(s) that will be passed to the group callback when all
		671	subrequests have finished. By default, no argument will be passed.
		672
		673	=item feed $grp $callback->($grp)
		674
		675	[VERY EXPERIMENTAL]
		676
		677	Sets a feeder/generator on this group: every group can have an attached
		678	generator that generates requests if idle. The idea behind this is that,
		679	although you could just queue as many requests as you want in a group,
		680	this might starve other requests for a potentially long time. For
		681	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		682	requests, delaying any later requests for a long time.
		683
		684	To avoid this, and allow incremental generation of requests, you can
		685	instead a group and set a feeder on it that generates those requests. The
		686	feed callback will be called whenever there are few enough (see C<feed_limit>,
		687	below) requests active in the group itself and is expected to queue more
		688	requests.
		689
		690	The feed can queue as many requests as it likes (i.e. C<add> does not
		691	impose any limits).
		692
		693	If the feed does not queue more requests when called, it will be
		694	automatically removed from the group.
		695
		696	If the feed limit is C<0>, it will be set to C<2> automatically.
		697
		698	Example:
		699
		700	# stat all files in @files, but only ever use four aio requests concurrently:
		701
		702	my $grp = aio_group sub { print "finished\n" };
		703	feed_limit $grp 4;
		704	feed $grp sub {
		705	my $file = pop @files
		706	or return;
		707
		708	add $grp aio_stat $file, sub { ... };
		709	};
		710
		711	=item feed_limit $grp $num
		712
		713	Sets the feeder limit for the group: The feeder will be called whenever
		714	the group contains less than this many requests.
		715
		716	Setting the limit to C<0> will pause the feeding process.
400		717
401	=back	718	=back
402		719
403	=head2 SUPPORT FUNCTIONS	720	=head2 SUPPORT FUNCTIONS
404		721
…		…
462	IO::AIO::poll_wait, IO::AIO::poll_cb	779	IO::AIO::poll_wait, IO::AIO::poll_cb
463	if IO::AIO::nreqs;	780	if IO::AIO::nreqs;
464		781
465	=item IO::AIO::min_parallel $nthreads	782	=item IO::AIO::min_parallel $nthreads
466		783
467	Set the minimum number of AIO threads to C<$nthreads>. The current default	784	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	785	default is C<8>, which means eight asynchronous operations can execute
469	(the number of outstanding operations, however, is unlimited).	786	concurrently at any one time (the number of outstanding requests,
		787	however, is unlimited).
470		788
471	IO::AIO starts threads only on demand, when an AIO request is queued and	789	IO::AIO starts threads only on demand, when an AIO request is queued and
472	no free thread exists.	790	no free thread exists.
473		791
474	It is recommended to keep the number of threads low, as some Linux	792	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	793	Linux kernel versions will scale negatively with the number of threads
476	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	794	(higher parallelity => MUCH higher latency). With current Linux 2.6
477	threads should be fine.	795	versions, 4-32 threads should be fine.
478		796
479	Under most circumstances you don't need to call this function, as the	797	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.	798	module selects a default that is suitable for low to moderate load.
481		799
482	=item IO::AIO::max_parallel $nthreads	800	=item IO::AIO::max_parallel $nthreads
…		…
493		811
494	Under normal circumstances you don't need to call this function.	812	Under normal circumstances you don't need to call this function.
495		813
496	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	814	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
497		815
		816	[DEPRECATED]
		817
498	Sets the maximum number of outstanding requests to C<$nreqs>. If you	818	Sets the maximum number of outstanding requests to C<$nreqs>. If you
499	try to queue up more than this number of requests, the caller will block until	819	try to queue up more than this number of requests, the caller will block until
500	some requests have been handled.	820	some requests have been handled.
501		821
502	The default is very large, so normally there is no practical limit. If you	822	The default is very large, so normally there is no practical limit. If you
503	queue up many requests in a loop it often improves speed if you set	823	queue up many requests in a loop it often improves speed if you set
504	this to a relatively low number, such as C<100>.	824	this to a relatively low number, such as C<100>.
		825
		826	This function does not work well together with C<aio_group>'s, and their
		827	feeder interface is better suited to limiting concurrency, so do not use
		828	this function.
505		829
506	Under normal circumstances you don't need to call this function.	830	Under normal circumstances you don't need to call this function.
507		831
508	=back	832	=back
509		833
…		…
523	or return undef;	847	or return undef;
524		848
525	*$sym	849	*$sym
526	}	850	}
527		851
528	min_parallel 4;	852	min_parallel 8;
529		853
530	END {	854	END {
531	max_parallel 0;	855	max_parallel 0;
532	}	856	}
533		857
534	1;	858	1;
535		859
536	=head2 FORK BEHAVIOUR	860	=head2 FORK BEHAVIOUR
		861
		862	This module should do "the right thing" when the process using it forks:
537		863
538	Before the fork, IO::AIO enters a quiescent state where no requests	864	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	865	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	866	the fork the parent simply leaves the quiescent state and continues
541	request/result processing, while the child clears the request/result	867	request/result processing, while the child clears the request/result
542	queue (so the requests started before the fork will only be handled in	868	queue (so the requests started before the fork will only be handled in
543	the parent). Threats will be started on demand until the limit ste in the	869	the parent). Threads will be started on demand until the limit ste in the
544	parent process has been reached again.	870	parent process has been reached again.
545		871
		872	In short: the parent will, after a short pause, continue as if fork had
		873	not been called, while the child will act as if IO::AIO has not been used
		874	yet.
		875
		876	=head2 MEMORY USAGE
		877
		878	Each aio request uses - depending on your architecture - around 128 bytes
		879	of memory. In addition, stat requests need a stat buffer (possibly a few
		880	hundred bytes). Perl scalars and other data passed into aio requests will
		881	also be locked.
		882
		883	This is now awfully much, so queuing lots of requests is not usually a
		884	problem.
		885
		886	Each thread needs a stack area which is usually around 16k, sometimes much
		887	larger, depending on the OS.
		888
546	=head1 SEE ALSO	889	=head1 SEE ALSO
547		890
548	L<Coro>, L<Linux::AIO>.	891	L<Coro>, L<Linux::AIO> (obsolete).
549		892
550	=head1 AUTHOR	893	=head1 AUTHOR
551		894
552	Marc Lehmann <schmorp@schmorp.de>	895	Marc Lehmann <schmorp@schmorp.de>
553	http://home.schmorp.de/	896	http://home.schmorp.de/

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Revision 1.67 by root, Tue Oct 24 02:25:16 2006 UTC