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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.40 by root, Tue Aug 30 15:45:10 2005 UTC vs.
Revision 1.63 by root, Mon Oct 23 00:34:36 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	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
		30	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		31	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		32
		33	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	34	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	35	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	36	cb => \&IO::AIO::poll_cb);
24		37
25	# Glib/Gtk2	38	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	39	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb; 1 };	40	in => sub { IO::AIO::poll_cb; 1 };
28		41
29	# Tk	42	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	43	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	44	readable => \&IO::AIO::poll_cb);
32		45
33	# Danga::Socket	46	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	47	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	48	\&IO::AIO::poll_cb);
36
37		49
38	=head1 DESCRIPTION	50	=head1 DESCRIPTION
39		51
40	This module implements asynchronous I/O using whatever means your	52	This module implements asynchronous I/O using whatever means your
41	operating system supports.	53	operating system supports.
…		…
57	=cut	69	=cut
58		70
59	package IO::AIO;	71	package IO::AIO;
60		72
61	no warnings;	73	no warnings;
		74	use strict 'vars';
62		75
63	use base 'Exporter';	76	use base 'Exporter';
64		77
65	use Fcntl ();
66
67	BEGIN {	78	BEGIN {
68	$VERSION = 1.6;	79	our $VERSION = '2.0';
69		80
70	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	81	our @EXPORT = 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	82	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72	aio_fsync aio_fdatasync aio_readahead);	83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		84	aio_group aio_nop);
73	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
74	max_outstanding nreqs);	86
		87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
75		88
76	require XSLoader;	89	require XSLoader;
77	XSLoader::load IO::AIO, $VERSION;	90	XSLoader::load ("IO::AIO", $VERSION);
78	}	91	}
79		92
80	=head1 FUNCTIONS	93	=head1 FUNCTIONS
81		94
82	=head2 AIO FUNCTIONS	95	=head2 AIO FUNCTIONS
…		…
89	perl, which usually delivers "false") as it's sole argument when the given	102	perl, which usually delivers "false") as it's sole argument when the given
90	syscall has been executed asynchronously.	103	syscall has been executed asynchronously.
91		104
92	All functions expecting a filehandle keep a copy of the filehandle	105	All functions expecting a filehandle keep a copy of the filehandle
93	internally until the request has finished.	106	internally until the request has finished.
		107
		108	All requests return objects of type L<IO::AIO::REQ> that allow further
		109	manipulation of those requests while they are in-flight.
94		110
95	The pathnames you pass to these routines I<must> be absolute and	111	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	112	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	113	request is being executed, the current working directory could have
98	changed. Alternatively, you can make sure that you never change the	114	changed. Alternatively, you can make sure that you never change the
…		…
164	aio_read $fh, 7, 15, $buffer, 0, sub {	180	aio_read $fh, 7, 15, $buffer, 0, sub {
165	$_[0] > 0 or die "read error: $!";	181	$_[0] > 0 or die "read error: $!";
166	print "read $_[0] bytes: <$buffer>\n";	182	print "read $_[0] bytes: <$buffer>\n";
167	};	183	};
168		184
		185	=item aio_move $srcpath, $dstpath, $callback->($status)
		186
		187	[EXPERIMENTAL due to internal aio_group use]
		188
		189	Try to move the I<file> (directories not supported as either source or
		190	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		191	the C<0> (error) or C<-1> ok.
		192
		193	This is a composite request that tries to rename(2) the file first. If
		194	rename files with C<EXDEV>, it creates the destination file with mode 0200
		195	and copies the contents of the source file into it using C<aio_sendfile>,
		196	followed by restoring atime, mtime, access mode and uid/gid, in that
		197	order, and unlinking the C<$srcpath>.
		198
		199	If an error occurs, the partial destination file will be unlinked, if
		200	possible, except when setting atime, mtime, access mode and uid/gid, where
		201	errors are being ignored.
		202
		203	=cut
		204
		205	sub aio_move($$$) {
		206	my ($src, $dst, $cb) = @_;
		207
		208	my $grp = aio_group $cb;
		209
		210	add $grp aio_rename $src, $dst, sub {
		211	if ($_[0] && $! == EXDEV) {
		212	add $grp aio_open $src, O_RDONLY, 0, sub {
		213	if (my $src_fh = $_[0]) {
		214	my @stat = stat $src_fh;
		215
		216	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		217	if (my $dst_fh = $_[0]) {
		218	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		219	close $src_fh;
		220
		221	if ($_[0] == $stat[7]) {
		222	utime $stat[8], $stat[9], $dst;
		223	chmod $stat[2] & 07777, $dst_fh;
		224	chown $stat[4], $stat[5], $dst_fh;
		225	close $dst_fh;
		226
		227	add $grp aio_unlink $src, sub {
		228	$grp->result ($_[0]);
		229	};
		230	} else {
		231	my $errno = $!;
		232	add $grp aio_unlink $dst, sub {
		233	$! = $errno;
		234	$grp->result (-1);
		235	};
		236	}
		237	};
		238	} else {
		239	$grp->result (-1);
		240	}
		241	},
		242
		243	} else {
		244	$grp->result (-1);
		245	}
		246	};
		247	} else {
		248	$grp->result ($_[0]);
		249	}
		250	};
		251
		252	$grp
		253	}
		254
169	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
170		256
171	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	257	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	258	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	259	file offset of C<$out_fh>. Because of that, it is not safe to issue more
…		…
228	=item aio_unlink $pathname, $callback->($status)	314	=item aio_unlink $pathname, $callback->($status)
229		315
230	Asynchronously unlink (delete) a file and call the callback with the	316	Asynchronously unlink (delete) a file and call the callback with the
231	result code.	317	result code.
232		318
		319	=item aio_link $srcpath, $dstpath, $callback->($status)
		320
		321	Asynchronously create a new link to the existing object at C<$srcpath> at
		322	the path C<$dstpath> and call the callback with the result code.
		323
		324	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		325
		326	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		327	the path C<$dstpath> and call the callback with the result code.
		328
		329	=item aio_rename $srcpath, $dstpath, $callback->($status)
		330
		331	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		332	rename(2) and call the callback with the result code.
		333
233	=item aio_rmdir $pathname, $callback->($status)	334	=item aio_rmdir $pathname, $callback->($status)
234		335
235	Asynchronously rmdir (delete) a directory and call the callback with the	336	Asynchronously rmdir (delete) a directory and call the callback with the
236	result code.	337	result code.
237		338
238	=item aio_readdir $pathname $callback->($entries)	339	=item aio_readdir $pathname, $callback->($entries)
239		340
240	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	341	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	342	directory (i.e. opendir + readdir + closedir). The entries will not be
242	sorted, and will B<NOT> include the C<.> and C<..> entries.	343	sorted, and will B<NOT> include the C<.> and C<..> entries.
243		344
244	The callback a single argument which is either C<undef> or an array-ref	345	The callback a single argument which is either C<undef> or an array-ref
245	with the filenames.	346	with the filenames.
246		347
247	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
248		349
		350	[EXPERIMENTAL due to internal aio_group use]
		351
249	Scans a directory (similar to C<aio_readdir>) and tries to separate the	352	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	353	separate the entries of directory C<$path> into two sets of names, ones
251	into (directories), and ones you cannot recurse into (everything else).	354	you can recurse into (directories or links to them), and ones you cannot
		355	recurse into (everything else).
252		356
253	C<aio_scandir> is a composite request that consists of many	357	C<aio_scandir> is a composite request that creates of many sub requests_
254	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	358	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	359	this function generates. If it is C<< <= 0 >>, then a suitable default
256	suitable default will be chosen (currently 8).	360	will be chosen (currently 6).
257		361
258	On error, the callback is called without arguments, otherwise it receives	362	On error, the callback is called without arguments, otherwise it receives
259	two array-refs with path-relative entry names.	363	two array-refs with path-relative entry names.
260		364
261	Example:	365	Example:
…		…
269	Implementation notes.	373	Implementation notes.
270		374
271	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	375	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
272		376
273	After reading the directory, the modification time, size etc. of the	377	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	378	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	379	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	380	entries are directories (if >= 2). Otherwise, no knowledge of the number
277	assumed.	381	of subdirectories will be assumed.
278		382
279	Then entires will be sorted into likely directories (everything without a	383	Then entries will be sorted into likely directories (everything without
280	non-initial dot) and likely non-directories (everything else). Then every	384	a non-initial dot currently) and likely non-directories (everything
281	entry + C</.> will be C<stat>'ed, likely directories first. This is often	385	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		386	likely directories first. If that succeeds, it assumes that the entry
		387	is a directory or a symlink to directory (which will be checked
		388	seperately). This is often faster than stat'ing the entry itself because
282	faster because filesystems might detect the type of the entry without	389	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,	390	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		391
287	If the known number of directories has been reached, the rest of the	392	If the known number of directories (link count - 2) has been reached, the
288	entries is assumed to be non-directories.	393	rest of the entries is assumed to be non-directories.
		394
		395	This only works with certainty on POSIX (= UNIX) filesystems, which
		396	fortunately are the vast majority of filesystems around.
		397
		398	It will also likely work on non-POSIX filesystems with reduced efficiency
		399	as those tend to return 0 or 1 as link counts, which disables the
		400	directory counting heuristic.
289		401
290	=cut	402	=cut
291		403
292	sub aio_scandir($$$) {	404	sub aio_scandir($$$) {
293	my ($path, $maxreq, $cb) = @_;	405	my ($path, $maxreq, $cb) = @_;
294		406
		407	my $grp = aio_group $cb;
		408
295	$maxreq = 8 if $maxreq <= 0;	409	$maxreq = 6 if $maxreq <= 0;
296		410
297	# stat once	411	# stat once
298	aio_stat $path, sub {	412	add $grp aio_stat $path, sub {
299	$cb->() if $_[0];	413	return $grp->result () if $_[0];
		414	my $now = time;
300	my $hash1 = join ":", (stat _)[0,1,3,7,9];	415	my $hash1 = join ":", (stat _)[0,1,3,7,9];
301		416
302	# read the directory entries	417	# read the directory entries
303	aio_readdir $path, sub {	418	add $grp aio_readdir $path, sub {
304	my $entries = shift	419	my $entries = shift
305	or return $cb->();	420	or return $grp->result ();
306		421
307	# stat the dir another time	422	# stat the dir another time
308	aio_stat $path, sub {	423	add $grp aio_stat $path, sub {
309	my $hash2 = join ":", (stat _)[0,1,3,7,9];	424	my $hash2 = join ":", (stat _)[0,1,3,7,9];
310		425
311	my $ndirs;	426	my $ndirs;
312		427
313	# take the slow route if anything looks fishy	428	# take the slow route if anything looks fishy
314	if ($hash1 ne $hash2) {	429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
315	$ndirs = -1;	430	$ndirs = -1;
316	} else {	431	} else {
317	# if nlink == 2, we are finished	432	# if nlink == 2, we are finished
318	# on non-posix-fs's, we rely on nlink < 2	433	# on non-posix-fs's, we rely on nlink < 2
319	$ndirs = (stat _)[3] - 2	434	$ndirs = (stat _)[3] - 2
320	or $cb->([], $entries);	435	or return $grp->result ([], $entries);
321	}	436	}
322		437
323	# sort into likely dirs and likely nondirs	438	# sort into likely dirs and likely nondirs
324	# dirs == files without ".", short entries first	439	# dirs == files without ".", short entries first
325	$entries = [map $_->[0],	440	$entries = [map $_->[0],
…		…
330	my (@dirs, @nondirs);	445	my (@dirs, @nondirs);
331		446
332	my ($statcb, $schedcb);	447	my ($statcb, $schedcb);
333	my $nreq = 0;	448	my $nreq = 0;
334		449
		450	my $statgrp = add $grp aio_group;
		451
335	$schedcb = sub {	452	$schedcb = sub {
336	if (@$entries) {	453	if (@$entries) {
337	if ($nreq < $maxreq) {	454	if ($nreq < $maxreq) {
338	my $ent = pop @$entries;	455	my $ent = pop @$entries;
339	$nreq++;	456	$nreq++;
340	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };	457	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
341	}	458	}
342	} elsif (!$nreq) {	459	} elsif (!$nreq) {
343	# finished	460	# finished
		461	$statgrp->cancel;
344	undef $statcb;	462	undef $statcb;
345	undef $schedcb;	463	undef $schedcb;
346	$cb->(\@dirs, \@nondirs);	464	$grp->result (\@dirs, \@nondirs);
347	undef $cb;
348	}	465	}
349	};	466	};
350	$statcb = sub {	467	$statcb = sub {
351	my ($status, $entry) = @_;	468	my ($status, $entry) = @_;
352		469
…		…
354	$nreq--;	471	$nreq--;
355	push @nondirs, $entry;	472	push @nondirs, $entry;
356	&$schedcb;	473	&$schedcb;
357	} else {	474	} else {
358	# need to check for real directory	475	# need to check for real directory
359	aio_lstat "$path/$entry", sub {	476	add $grp aio_lstat "$path/$entry", sub {
360	$nreq--;	477	$nreq--;
361		478
362	if (-d _) {	479	if (-d _) {
363	push @dirs, $entry;	480	push @dirs, $entry;
364		481
…		…
377		494
378	&$schedcb while @$entries && $nreq < $maxreq;	495	&$schedcb while @$entries && $nreq < $maxreq;
379	};	496	};
380	};	497	};
381	};	498	};
		499
		500	$grp
382	}	501	}
383		502
384	=item aio_fsync $fh, $callback->($status)	503	=item aio_fsync $fh, $callback->($status)
385		504
386	Asynchronously call fsync on the given filehandle and call the callback	505	Asynchronously call fsync on the given filehandle and call the callback
…		…
391	Asynchronously call fdatasync on the given filehandle and call the	510	Asynchronously call fdatasync on the given filehandle and call the
392	callback with the fdatasync result code.	511	callback with the fdatasync result code.
393		512
394	If this call isn't available because your OS lacks it or it couldn't be	513	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.	514	detected, it will be emulated by calling C<fsync> instead.
		515
		516	=item aio_group $callback->(...)
		517
		518	[EXPERIMENTAL]
		519
		520	This is a very special aio request: Instead of doing something, it is a
		521	container for other aio requests, which is useful if you want to bundle
		522	many requests into a single, composite, request.
		523
		524	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		525	for more info.
		526
		527	Example:
		528
		529	my $grp = aio_group sub {
		530	print "all stats done\n";
		531	};
		532
		533	add $grp
		534	(aio_stat ...),
		535	(aio_stat ...),
		536	...;
		537
		538	=item aio_nop $callback->()
		539
		540	This is a special request - it does nothing in itself and is only used for
		541	side effects, such as when you want to add a dummy request to a group so
		542	that finishing the requests in the group depends on executing the given
		543	code.
		544
		545	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		546
		547	Mainly used for debugging and benchmarking, this aio request puts one of
		548	the request workers to sleep for the given time.
		549
		550	While it is theoretically handy to have simple I/O scheduling requests
		551	like sleep and file handle readable/writable, the overhead this creates
		552	is immense, so do not use this function except to put your application
		553	under artificial I/O pressure.
		554
		555	=back
		556
		557	=head2 IO::AIO::REQ CLASS
		558
		559	All non-aggregate C<aio_*> functions return an object of this class when
		560	called in non-void context.
		561
		562	A request always moves through the following five states in its lifetime,
		563	in order: B<ready> (request has been created, but has not been executed
		564	yet), B<execute> (request is currently being executed), B<pending>
		565	(request has been executed but callback has not been called yet),
		566	B<result> (results are being processed synchronously, includes calling the
		567	callback) and B<done> (request has reached the end of its lifetime and
		568	holds no resources anymore).
		569
		570	=over 4
		571
		572	=item $req->cancel
		573
		574	Cancels the request, if possible. Has the effect of skipping execution
		575	when entering the B<execute> state and skipping calling the callback when
		576	entering the the B<result> state, but will leave the request otherwise
		577	untouched. That means that requests that currently execute will not be
		578	stopped and resources held by the request will not be freed prematurely.
		579
		580	=back
		581
		582	=head2 IO::AIO::GRP CLASS
		583
		584	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		585	objects of this class, too.
		586
		587	A IO::AIO::GRP object is a special request that can contain multiple other
		588	aio requests.
		589
		590	You create one by calling the C<aio_group> constructing function with a
		591	callback that will be called when all contained requests have entered the
		592	C<done> state:
		593
		594	my $grp = aio_group sub {
		595	print "all requests are done\n";
		596	};
		597
		598	You add requests by calling the C<add> method with one or more
		599	C<IO::AIO::REQ> objects:
		600
		601	$grp->add (aio_unlink "...");
		602
		603	add $grp aio_stat "...", sub {
		604	$_[0] or return $grp->result ("error");
		605
		606	# add another request dynamically, if first succeeded
		607	add $grp aio_open "...", sub {
		608	$grp->result ("ok");
		609	};
		610	};
		611
		612	This makes it very easy to create composite requests (see the source of
		613	C<aio_move> for an application) that work and feel like simple requests.
		614
		615	=over 4
		616
		617	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		618	C<IO::AIO::poll_cb>, just like any other request.
		619
		620	=item * They can be canceled like any other request. Canceling will cancel not
		621	only the request itself, but also all requests it contains.
		622
		623	=item * They can also can also be added to other IO::AIO::GRP objects.
		624
		625	=item * You must not add requests to a group from within the group callback (or
		626	any later time).
		627
		628	=item * This does not harmonise well with C<max_outstanding>, so best do
		629	not combine C<aio_group> with it. Groups and feeders are recommended for
		630	this kind of concurrency-limiting.
		631
		632	=back
		633
		634	Their lifetime, simplified, looks like this: when they are empty, they
		635	will finish very quickly. If they contain only requests that are in the
		636	C<done> state, they will also finish. Otherwise they will continue to
		637	exist.
		638
		639	That means after creating a group you have some time to add requests. And
		640	in the callbacks of those requests, you can add further requests to the
		641	group. And only when all those requests have finished will the the group
		642	itself finish.
		643
		644	=over 4
		645
		646	=item $grp->add (...)
		647
		648	=item add $grp ...
		649
		650	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		651	be added, including other groups, as long as you do not create circular
		652	dependencies.
		653
		654	Returns all its arguments.
		655
		656	=item $grp->result (...)
		657
		658	Set the result value(s) that will be passed to the group callback when all
		659	subrequests have finished. By default, no argument will be passed.
		660
		661	=item $grp->set_feeder ($callback->($grp))
		662
		663	[VERY EXPERIMENTAL]
		664
		665	Sets a feeder/generator on this group: every group can have an attached
		666	generator that generates requests if idle. The idea behind this is that,
		667	although you could just queue as many requests as you want in a group,
		668	this might starve other requests for a potentially long time. For
		669	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		670	requests, delaying any later requests for a long time.
		671
		672	To avoid this, and allow incremental generation of requests, you can
		673	instead a group and set a feeder on it that generates those requests. The
		674	feeder will be called whenever there are few enough (see C<feeder_limit>,
		675	below) requests active in the group itself and is expected to queue more
		676	requests.
		677
		678	The feeder can queue as many requests as it likes (i.e. C<add> does not
		679	impose any limits).
		680
		681	If the feeder does not queue more requests when called, it will be
		682	automatically removed from the group.
		683
		684	If the feeder limit is C<0>, it will be set to C<2> automatically.
		685
		686	Example:
		687
		688	# stat all files in @files, but only ever use four aio requests concurrently:
		689
		690	my $grp = aio_group sub { print "finished\n" };
		691	$grp->feeder_limit (4);
		692	$grp->set_feeder (sub {
		693	my $file = pop @files
		694	or return;
		695
		696	add $grp aio_stat $file, sub { ... };
		697	});
		698
		699	=item $grp->feeder_limit ($num)
		700
		701	Sets the feeder limit for the group: The feeder will be called whenever
		702	the group contains less than this many requests.
		703
		704	Setting the limit to C<0> will pause the feeding process.
396		705
397	=back	706	=back
398		707
399	=head2 SUPPORT FUNCTIONS	708	=head2 SUPPORT FUNCTIONS
400		709
…		…
458	IO::AIO::poll_wait, IO::AIO::poll_cb	767	IO::AIO::poll_wait, IO::AIO::poll_cb
459	if IO::AIO::nreqs;	768	if IO::AIO::nreqs;
460		769
461	=item IO::AIO::min_parallel $nthreads	770	=item IO::AIO::min_parallel $nthreads
462		771
463	Set the minimum number of AIO threads to C<$nthreads>. The current default	772	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	773	default is C<8>, which means eight asynchronous operations can execute
465	(the number of outstanding operations, however, is unlimited).	774	concurrently at any one time (the number of outstanding requests,
		775	however, is unlimited).
466		776
467	IO::AIO starts threads only on demand, when an AIO request is queued and	777	IO::AIO starts threads only on demand, when an AIO request is queued and
468	no free thread exists.	778	no free thread exists.
469		779
470	It is recommended to keep the number of threads low, as some Linux	780	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	781	Linux kernel versions will scale negatively with the number of threads
472	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	782	(higher parallelity => MUCH higher latency). With current Linux 2.6
473	threads should be fine.	783	versions, 4-32 threads should be fine.
474		784
475	Under most circumstances you don't need to call this function, as the	785	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.	786	module selects a default that is suitable for low to moderate load.
477		787
478	=item IO::AIO::max_parallel $nthreads	788	=item IO::AIO::max_parallel $nthreads
…		…
489		799
490	Under normal circumstances you don't need to call this function.	800	Under normal circumstances you don't need to call this function.
491		801
492	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	802	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
493		803
		804	[DEPRECATED]
		805
494	Sets the maximum number of outstanding requests to C<$nreqs>. If you	806	Sets the maximum number of outstanding requests to C<$nreqs>. If you
495	try to queue up more than this number of requests, the caller will block until	807	try to queue up more than this number of requests, the caller will block until
496	some requests have been handled.	808	some requests have been handled.
497		809
498	The default is very large, so normally there is no practical limit. If you	810	The default is very large, so normally there is no practical limit. If you
499	queue up many requests in a loop it often improves speed if you set	811	queue up many requests in a loop it often improves speed if you set
500	this to a relatively low number, such as C<100>.	812	this to a relatively low number, such as C<100>.
		813
		814	This function does not work well together with C<aio_group>'s, and their
		815	feeder interface is better suited to limiting concurrency, so do not use
		816	this function.
501		817
502	Under normal circumstances you don't need to call this function.	818	Under normal circumstances you don't need to call this function.
503		819
504	=back	820	=back
505		821
…		…
519	or return undef;	835	or return undef;
520		836
521	*$sym	837	*$sym
522	}	838	}
523		839
524	min_parallel 4;	840	min_parallel 8;
525		841
526	END {	842	END {
527	max_parallel 0;	843	max_parallel 0;
528	}	844	}
529		845
530	1;	846	1;
531		847
532	=head2 FORK BEHAVIOUR	848	=head2 FORK BEHAVIOUR
		849
		850	This module should do "the right thing" when the process using it forks:
533		851
534	Before the fork, IO::AIO enters a quiescent state where no requests	852	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	853	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	854	the fork the parent simply leaves the quiescent state and continues
537	request/result processing, while the child clears the request/result	855	request/result processing, while the child clears the request/result
538	queue (so the requests started before the fork will only be handled in	856	queue (so the requests started before the fork will only be handled in
539	the parent). Threats will be started on demand until the limit ste in the	857	the parent). Threads will be started on demand until the limit ste in the
540	parent process has been reached again.	858	parent process has been reached again.
541		859
		860	In short: the parent will, after a short pause, continue as if fork had
		861	not been called, while the child will act as if IO::AIO has not been used
		862	yet.
		863
		864	=head2 MEMORY USAGE
		865
		866	Each aio request uses - depending on your architecture - around 128 bytes
		867	of memory. In addition, stat requests need a stat buffer (possibly a few
		868	hundred bytes). Perl scalars and other data passed into aio requests will
		869	also be locked.
		870
		871	This is now awfully much, so queuing lots of requests is not usually a
		872	problem.
		873
		874	Each thread needs a stack area which is usually around 16k, sometimes much
		875	larger, depending on the OS.
		876
542	=head1 SEE ALSO	877	=head1 SEE ALSO
543		878
544	L<Coro>, L<Linux::AIO>.	879	L<Coro>, L<Linux::AIO> (obsolete).
545		880
546	=head1 AUTHOR	881	=head1 AUTHOR
547		882
548	Marc Lehmann <schmorp@schmorp.de>	883	Marc Lehmann <schmorp@schmorp.de>
549	http://home.schmorp.de/	884	http://home.schmorp.de/

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Revision 1.63 by root, Mon Oct 23 00:34:36 2006 UTC