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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.48 by root, Thu Feb 16 16:38:57 2006 UTC vs.
Revision 1.65 by root, Mon Oct 23 14:49:51 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
41		49
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.
…		…
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 = '1.72';	79	our $VERSION = '2.0';
73		80
74	@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
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
		84	aio_group aio_nop);
77	@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);
78	max_outstanding nreqs);	86
		87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
79		88
80	require XSLoader;	89	require XSLoader;
81	XSLoader::load IO::AIO, $VERSION;	90	XSLoader::load ("IO::AIO", $VERSION);
82	}	91	}
83		92
84	=head1 FUNCTIONS	93	=head1 FUNCTIONS
85		94
86	=head2 AIO FUNCTIONS	95	=head2 AIO FUNCTIONS
…		…
94	syscall has been executed asynchronously.	103	syscall has been executed asynchronously.
95		104
96	All functions expecting a filehandle keep a copy of the filehandle	105	All functions expecting a filehandle keep a copy of the filehandle
97	internally until the request has finished.	106	internally until the request has finished.
98		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.
		110
99	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
100	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
101	request is being executed, the current working directory could have	113	request is being executed, the current working directory could have
102	changed. Alternatively, you can make sure that you never change the	114	changed. Alternatively, you can make sure that you never change the
103	current working directory.	115	current working directory.
…		…
167		179
168	aio_read $fh, 7, 15, $buffer, 0, sub {	180	aio_read $fh, 7, 15, $buffer, 0, sub {
169	$_[0] > 0 or die "read error: $!";	181	$_[0] > 0 or die "read error: $!";
170	print "read $_[0] bytes: <$buffer>\n";	182	print "read $_[0] bytes: <$buffer>\n";
171	};	183	};
		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	}
172		254
173	=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)
174		256
175	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
176	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
…		…
232	=item aio_unlink $pathname, $callback->($status)	314	=item aio_unlink $pathname, $callback->($status)
233		315
234	Asynchronously unlink (delete) a file and call the callback with the	316	Asynchronously unlink (delete) a file and call the callback with the
235	result code.	317	result code.
236		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
237	=item aio_rmdir $pathname, $callback->($status)	334	=item aio_rmdir $pathname, $callback->($status)
238		335
239	Asynchronously rmdir (delete) a directory and call the callback with the	336	Asynchronously rmdir (delete) a directory and call the callback with the
240	result code.	337	result code.
241		338
…		…
248	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
249	with the filenames.	346	with the filenames.
250		347
251	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
252		349
		350	[EXPERIMENTAL due to internal aio_group use]
		351
253	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
254	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
255	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).
256		356
257	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_
258	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	358	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	359	this function generates. If it is C<< <= 0 >>, then a suitable default
260	suitable default will be chosen (currently 8).	360	will be chosen (currently 6).
261		361
262	On error, the callback is called without arguments, otherwise it receives	362	On error, the callback is called without arguments, otherwise it receives
263	two array-refs with path-relative entry names.	363	two array-refs with path-relative entry names.
264		364
265	Example:	365	Example:
…		…
273	Implementation notes.	373	Implementation notes.
274		374
275	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.
276		376
277	After reading the directory, the modification time, size etc. of the	377	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	378	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	379	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	380	entries are directories (if >= 2). Otherwise, no knowledge of the number
281	assumed.	381	of subdirectories will be assumed.
282		382
283	Then entires will be sorted into likely directories (everything without a	383	Then entries will be sorted into likely directories (everything without
284	non-initial dot) and likely non-directories (everything else). Then every	384	a non-initial dot currently) and likely non-directories (everything
285	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
286	faster because filesystems might detect the type of the entry without	389	filesystems might detect the type of the entry without reading the inode
287	reading the inode data (e.g. ext2fs filetype feature). If that succeeds,	390	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		391
291	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
292	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.
293		401
294	=cut	402	=cut
295		403
296	sub aio_scandir($$$) {	404	sub aio_scandir($$$) {
297	my ($path, $maxreq, $cb) = @_;	405	my ($path, $maxreq, $cb) = @_;
298		406
		407	my $grp = aio_group $cb;
		408
299	$maxreq = 8 if $maxreq <= 0;	409	$maxreq = 6 if $maxreq <= 0;
300		410
301	# stat once	411	# stat once
302	aio_stat $path, sub {	412	add $grp aio_stat $path, sub {
303	return $cb->() if $_[0];	413	return $grp->result () if $_[0];
		414	my $now = time;
304	my $hash1 = join ":", (stat _)[0,1,3,7,9];	415	my $hash1 = join ":", (stat _)[0,1,3,7,9];
305		416
306	# read the directory entries	417	# read the directory entries
307	aio_readdir $path, sub {	418	add $grp aio_readdir $path, sub {
308	my $entries = shift	419	my $entries = shift
309	or return $cb->();	420	or return $grp->result ();
310		421
311	# stat the dir another time	422	# stat the dir another time
312	aio_stat $path, sub {	423	add $grp aio_stat $path, sub {
313	my $hash2 = join ":", (stat _)[0,1,3,7,9];	424	my $hash2 = join ":", (stat _)[0,1,3,7,9];
314		425
315	my $ndirs;	426	my $ndirs;
316		427
317	# take the slow route if anything looks fishy	428	# take the slow route if anything looks fishy
318	if ($hash1 ne $hash2) {	429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
319	$ndirs = -1;	430	$ndirs = -1;
320	} else {	431	} else {
321	# if nlink == 2, we are finished	432	# if nlink == 2, we are finished
322	# on non-posix-fs's, we rely on nlink < 2	433	# on non-posix-fs's, we rely on nlink < 2
323	$ndirs = (stat _)[3] - 2	434	$ndirs = (stat _)[3] - 2
324	or return $cb->([], $entries);	435	or return $grp->result ([], $entries);
325	}	436	}
326		437
327	# sort into likely dirs and likely nondirs	438	# sort into likely dirs and likely nondirs
328	# dirs == files without ".", short entries first	439	# dirs == files without ".", short entries first
329	$entries = [map $_->[0],	440	$entries = [map $_->[0],
…		…
334	my (@dirs, @nondirs);	445	my (@dirs, @nondirs);
335		446
336	my ($statcb, $schedcb);	447	my ($statcb, $schedcb);
337	my $nreq = 0;	448	my $nreq = 0;
338		449
		450	my $statgrp = add $grp aio_group;
		451
339	$schedcb = sub {	452	$schedcb = sub {
340	if (@$entries) {	453	if (@$entries) {
341	if ($nreq < $maxreq) {	454	if ($nreq < $maxreq) {
342	my $ent = pop @$entries;	455	my $ent = pop @$entries;
343	$nreq++;	456	$nreq++;
344	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };	457	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
345	}	458	}
346	} elsif (!$nreq) {	459	} elsif (!$nreq) {
347	# finished	460	# finished
		461	$statgrp->cancel;
348	undef $statcb;	462	undef $statcb;
349	undef $schedcb;	463	undef $schedcb;
350	$cb->(\@dirs, \@nondirs) if $cb;	464	$grp->result (\@dirs, \@nondirs);
351	undef $cb;
352	}	465	}
353	};	466	};
354	$statcb = sub {	467	$statcb = sub {
355	my ($status, $entry) = @_;	468	my ($status, $entry) = @_;
356		469
…		…
358	$nreq--;	471	$nreq--;
359	push @nondirs, $entry;	472	push @nondirs, $entry;
360	&$schedcb;	473	&$schedcb;
361	} else {	474	} else {
362	# need to check for real directory	475	# need to check for real directory
363	aio_lstat "$path/$entry", sub {	476	add $grp aio_lstat "$path/$entry", sub {
364	$nreq--;	477	$nreq--;
365		478
366	if (-d _) {	479	if (-d _) {
367	push @dirs, $entry;	480	push @dirs, $entry;
368		481
…		…
381		494
382	&$schedcb while @$entries && $nreq < $maxreq;	495	&$schedcb while @$entries && $nreq < $maxreq;
383	};	496	};
384	};	497	};
385	};	498	};
		499
		500	$grp
386	}	501	}
387		502
388	=item aio_fsync $fh, $callback->($status)	503	=item aio_fsync $fh, $callback->($status)
389		504
390	Asynchronously call fsync on the given filehandle and call the callback	505	Asynchronously call fsync on the given filehandle and call the callback
…		…
395	Asynchronously call fdatasync on the given filehandle and call the	510	Asynchronously call fdatasync on the given filehandle and call the
396	callback with the fdatasync result code.	511	callback with the fdatasync result code.
397		512
398	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
399	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	While this request does nothing, it still goes through the execution
		546	phase and still requires a worker thread. Thus, the callback will not
		547	be executed immediately but only after other requests in the queue have
		548	entered their execution phase. This can be used to measure request
		549	latency.
		550
		551	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		552
		553	Mainly used for debugging and benchmarking, this aio request puts one of
		554	the request workers to sleep for the given time.
		555
		556	While it is theoretically handy to have simple I/O scheduling requests
		557	like sleep and file handle readable/writable, the overhead this creates
		558	is immense, so do not use this function except to put your application
		559	under artificial I/O pressure.
		560
		561	=back
		562
		563	=head2 IO::AIO::REQ CLASS
		564
		565	All non-aggregate C<aio_*> functions return an object of this class when
		566	called in non-void context.
		567
		568	A request always moves through the following five states in its lifetime,
		569	in order: B<ready> (request has been created, but has not been executed
		570	yet), B<execute> (request is currently being executed), B<pending>
		571	(request has been executed but callback has not been called yet),
		572	B<result> (results are being processed synchronously, includes calling the
		573	callback) and B<done> (request has reached the end of its lifetime and
		574	holds no resources anymore).
		575
		576	=over 4
		577
		578	=item cancel $req
		579
		580	Cancels the request, if possible. Has the effect of skipping execution
		581	when entering the B<execute> state and skipping calling the callback when
		582	entering the the B<result> state, but will leave the request otherwise
		583	untouched. That means that requests that currently execute will not be
		584	stopped and resources held by the request will not be freed prematurely.
		585
		586	=item cb $req $callback->(...)
		587
		588	Replace (or simply set) the callback registered to the request.
		589
		590	=back
		591
		592	=head2 IO::AIO::GRP CLASS
		593
		594	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		595	objects of this class, too.
		596
		597	A IO::AIO::GRP object is a special request that can contain multiple other
		598	aio requests.
		599
		600	You create one by calling the C<aio_group> constructing function with a
		601	callback that will be called when all contained requests have entered the
		602	C<done> state:
		603
		604	my $grp = aio_group sub {
		605	print "all requests are done\n";
		606	};
		607
		608	You add requests by calling the C<add> method with one or more
		609	C<IO::AIO::REQ> objects:
		610
		611	$grp->add (aio_unlink "...");
		612
		613	add $grp aio_stat "...", sub {
		614	$_[0] or return $grp->result ("error");
		615
		616	# add another request dynamically, if first succeeded
		617	add $grp aio_open "...", sub {
		618	$grp->result ("ok");
		619	};
		620	};
		621
		622	This makes it very easy to create composite requests (see the source of
		623	C<aio_move> for an application) that work and feel like simple requests.
		624
		625	=over 4
		626
		627	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		628	C<IO::AIO::poll_cb>, just like any other request.
		629
		630	=item * They can be canceled like any other request. Canceling will cancel not
		631	only the request itself, but also all requests it contains.
		632
		633	=item * They can also can also be added to other IO::AIO::GRP objects.
		634
		635	=item * You must not add requests to a group from within the group callback (or
		636	any later time).
		637
		638	=item * This does not harmonise well with C<max_outstanding>, so best do
		639	not combine C<aio_group> with it. Groups and feeders are recommended for
		640	this kind of concurrency-limiting.
		641
		642	=back
		643
		644	Their lifetime, simplified, looks like this: when they are empty, they
		645	will finish very quickly. If they contain only requests that are in the
		646	C<done> state, they will also finish. Otherwise they will continue to
		647	exist.
		648
		649	That means after creating a group you have some time to add requests. And
		650	in the callbacks of those requests, you can add further requests to the
		651	group. And only when all those requests have finished will the the group
		652	itself finish.
		653
		654	=over 4
		655
		656	=item add $grp ...
		657
		658	=item $grp->add (...)
		659
		660	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		661	be added, including other groups, as long as you do not create circular
		662	dependencies.
		663
		664	Returns all its arguments.
		665
		666	=item $grp->result (...)
		667
		668	Set the result value(s) that will be passed to the group callback when all
		669	subrequests have finished. By default, no argument will be passed.
		670
		671	=item feed $grp $callback->($grp)
		672
		673	[VERY EXPERIMENTAL]
		674
		675	Sets a feeder/generator on this group: every group can have an attached
		676	generator that generates requests if idle. The idea behind this is that,
		677	although you could just queue as many requests as you want in a group,
		678	this might starve other requests for a potentially long time. For
		679	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		680	requests, delaying any later requests for a long time.
		681
		682	To avoid this, and allow incremental generation of requests, you can
		683	instead a group and set a feeder on it that generates those requests. The
		684	feed callback will be called whenever there are few enough (see C<feed_limit>,
		685	below) requests active in the group itself and is expected to queue more
		686	requests.
		687
		688	The feed can queue as many requests as it likes (i.e. C<add> does not
		689	impose any limits).
		690
		691	If the feed does not queue more requests when called, it will be
		692	automatically removed from the group.
		693
		694	If the feed limit is C<0>, it will be set to C<2> automatically.
		695
		696	Example:
		697
		698	# stat all files in @files, but only ever use four aio requests concurrently:
		699
		700	my $grp = aio_group sub { print "finished\n" };
		701	feed_limit $grp 4;
		702	feed $grp sub {
		703	my $file = pop @files
		704	or return;
		705
		706	add $grp aio_stat $file, sub { ... };
		707	};
		708
		709	=item feed_limit $grp $num
		710
		711	Sets the feeder limit for the group: The feeder will be called whenever
		712	the group contains less than this many requests.
		713
		714	Setting the limit to C<0> will pause the feeding process.
400		715
401	=back	716	=back
402		717
403	=head2 SUPPORT FUNCTIONS	718	=head2 SUPPORT FUNCTIONS
404		719
…		…
462	IO::AIO::poll_wait, IO::AIO::poll_cb	777	IO::AIO::poll_wait, IO::AIO::poll_cb
463	if IO::AIO::nreqs;	778	if IO::AIO::nreqs;
464		779
465	=item IO::AIO::min_parallel $nthreads	780	=item IO::AIO::min_parallel $nthreads
466		781
467	Set the minimum number of AIO threads to C<$nthreads>. The current default	782	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	783	default is C<8>, which means eight asynchronous operations can execute
469	(the number of outstanding operations, however, is unlimited).	784	concurrently at any one time (the number of outstanding requests,
		785	however, is unlimited).
470		786
471	IO::AIO starts threads only on demand, when an AIO request is queued and	787	IO::AIO starts threads only on demand, when an AIO request is queued and
472	no free thread exists.	788	no free thread exists.
473		789
474	It is recommended to keep the number of threads low, as some Linux	790	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	791	Linux kernel versions will scale negatively with the number of threads
476	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	792	(higher parallelity => MUCH higher latency). With current Linux 2.6
477	threads should be fine.	793	versions, 4-32 threads should be fine.
478		794
479	Under most circumstances you don't need to call this function, as the	795	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.	796	module selects a default that is suitable for low to moderate load.
481		797
482	=item IO::AIO::max_parallel $nthreads	798	=item IO::AIO::max_parallel $nthreads
…		…
493		809
494	Under normal circumstances you don't need to call this function.	810	Under normal circumstances you don't need to call this function.
495		811
496	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	812	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
497		813
		814	[DEPRECATED]
		815
498	Sets the maximum number of outstanding requests to C<$nreqs>. If you	816	Sets the maximum number of outstanding requests to C<$nreqs>. If you
499	try to queue up more than this number of requests, the caller will block until	817	try to queue up more than this number of requests, the caller will block until
500	some requests have been handled.	818	some requests have been handled.
501		819
502	The default is very large, so normally there is no practical limit. If you	820	The default is very large, so normally there is no practical limit. If you
503	queue up many requests in a loop it often improves speed if you set	821	queue up many requests in a loop it often improves speed if you set
504	this to a relatively low number, such as C<100>.	822	this to a relatively low number, such as C<100>.
		823
		824	This function does not work well together with C<aio_group>'s, and their
		825	feeder interface is better suited to limiting concurrency, so do not use
		826	this function.
505		827
506	Under normal circumstances you don't need to call this function.	828	Under normal circumstances you don't need to call this function.
507		829
508	=back	830	=back
509		831
…		…
523	or return undef;	845	or return undef;
524		846
525	*$sym	847	*$sym
526	}	848	}
527		849
528	min_parallel 4;	850	min_parallel 8;
529		851
530	END {	852	END {
531	max_parallel 0;	853	max_parallel 0;
532	}	854	}
533		855
534	1;	856	1;
535		857
536	=head2 FORK BEHAVIOUR	858	=head2 FORK BEHAVIOUR
		859
		860	This module should do "the right thing" when the process using it forks:
537		861
538	Before the fork, IO::AIO enters a quiescent state where no requests	862	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	863	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	864	the fork the parent simply leaves the quiescent state and continues
541	request/result processing, while the child clears the request/result	865	request/result processing, while the child clears the request/result
542	queue (so the requests started before the fork will only be handled in	866	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	867	the parent). Threads will be started on demand until the limit ste in the
544	parent process has been reached again.	868	parent process has been reached again.
545		869
		870	In short: the parent will, after a short pause, continue as if fork had
		871	not been called, while the child will act as if IO::AIO has not been used
		872	yet.
		873
		874	=head2 MEMORY USAGE
		875
		876	Each aio request uses - depending on your architecture - around 128 bytes
		877	of memory. In addition, stat requests need a stat buffer (possibly a few
		878	hundred bytes). Perl scalars and other data passed into aio requests will
		879	also be locked.
		880
		881	This is now awfully much, so queuing lots of requests is not usually a
		882	problem.
		883
		884	Each thread needs a stack area which is usually around 16k, sometimes much
		885	larger, depending on the OS.
		886
546	=head1 SEE ALSO	887	=head1 SEE ALSO
547		888
548	L<Coro>, L<Linux::AIO>.	889	L<Coro>, L<Linux::AIO> (obsolete).
549		890
550	=head1 AUTHOR	891	=head1 AUTHOR
551		892
552	Marc Lehmann <schmorp@schmorp.de>	893	Marc Lehmann <schmorp@schmorp.de>
553	http://home.schmorp.de/	894	http://home.schmorp.de/

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Revision 1.65 by root, Mon Oct 23 14:49:51 2006 UTC