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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.47 by root, Thu Dec 29 15:44:13 2005 UTC vs.
Revision 1.61 by root, Sun Oct 22 13:52:11 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);
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
…		…
93	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
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.
		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.
98		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
…		…
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	};
172		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
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
177	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
…		…
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. ext2s 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 IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		539
		540	Mainly used for debugging and benchmarking, this aio request puts one of
		541	the request workers to sleep for the given time.
		542
		543	While it is theoretically handy to have simple I/O scheduling requests
		544	like sleep and file handle readable/writable, the overhead this creates
		545	is immense, so do not use this function except to put your application
		546	under artificial I/O pressure.
		547
		548	=back
		549
		550	=head2 IO::AIO::REQ CLASS
		551
		552	All non-aggregate C<aio_*> functions return an object of this class when
		553	called in non-void context.
		554
		555	A request always moves through the following five states in its lifetime,
		556	in order: B<ready> (request has been created, but has not been executed
		557	yet), B<execute> (request is currently being executed), B<pending>
		558	(request has been executed but callback has not been called yet),
		559	B<result> (results are being processed synchronously, includes calling the
		560	callback) and B<done> (request has reached the end of its lifetime and
		561	holds no resources anymore).
		562
		563	=over 4
		564
		565	=item $req->cancel
		566
		567	Cancels the request, if possible. Has the effect of skipping execution
		568	when entering the B<execute> state and skipping calling the callback when
		569	entering the the B<result> state, but will leave the request otherwise
		570	untouched. That means that requests that currently execute will not be
		571	stopped and resources held by the request will not be freed prematurely.
		572
		573	=back
		574
		575	=head2 IO::AIO::GRP CLASS
		576
		577	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		578	objects of this class, too.
		579
		580	A IO::AIO::GRP object is a special request that can contain multiple other
		581	aio requests.
		582
		583	You create one by calling the C<aio_group> constructing function with a
		584	callback that will be called when all contained requests have entered the
		585	C<done> state:
		586
		587	my $grp = aio_group sub {
		588	print "all requests are done\n";
		589	};
		590
		591	You add requests by calling the C<add> method with one or more
		592	C<IO::AIO::REQ> objects:
		593
		594	$grp->add (aio_unlink "...");
		595
		596	add $grp aio_stat "...", sub {
		597	$_[0] or return $grp->result ("error");
		598
		599	# add another request dynamically, if first succeeded
		600	add $grp aio_open "...", sub {
		601	$grp->result ("ok");
		602	};
		603	};
		604
		605	This makes it very easy to create composite requests (see the source of
		606	C<aio_move> for an application) that work and feel like simple requests.
		607
		608	The IO::AIO::GRP objects will be cleaned up during calls to
		609	C<IO::AIO::poll_cb>, just like any other request.
		610
		611	They can be canceled like any other request. Canceling will cancel not
		612	only the request itself, but also all requests it contains.
		613
		614	They can also can also be added to other IO::AIO::GRP objects.
		615
		616	You must not add requests to a group from within the group callback (or
		617	any later time).
		618
		619	Their lifetime, simplified, looks like this: when they are empty, they
		620	will finish very quickly. If they contain only requests that are in the
		621	C<done> state, they will also finish. Otherwise they will continue to
		622	exist.
		623
		624	That means after creating a group you have some time to add requests. And
		625	in the callbacks of those requests, you can add further requests to the
		626	group. And only when all those requests have finished will the the group
		627	itself finish.
		628
		629	=over 4
		630
		631	=item $grp->add (...)
		632
		633	=item add $grp ...
		634
		635	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		636	be added, including other groups, as long as you do not create circular
		637	dependencies.
		638
		639	Returns all its arguments.
		640
		641	=item $grp->result (...)
		642
		643	Set the result value(s) that will be passed to the group callback when all
		644	subrequests have finished. By default, no argument will be passed.
		645
		646	=item $grp->set_feeder ($callback->($grp))
		647
		648	[VERY EXPERIMENTAL]
		649
		650	Sets a feeder/generator on this group: every group can have an attached
		651	generator that generates requests if idle. The idea behind this is that,
		652	although you could just queue as many requests as you want in a group,
		653	this might starve other requests for a potentially long time. For
		654	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		655	requests, delaying any later requests for a long time.
		656
		657	To avoid this, and allow incremental generation of requests, you can
		658	instead a group and set a feeder on it that generates those requests. The
		659	feeder will be called whenever there are few enough (see C<feeder_limit>,
		660	below) requests active in the group itself and is expected to queue more
		661	requests.
		662
		663	The feeder can queue as many requests as it likes (i.e. C<add> does not
		664	impose any limits).
		665
		666	If the feeder does not queue more requests when called, it will be
		667	automatically removed from the group.
		668
		669	If the feeder limit is C<0>, it will be set to C<2> automatically.
		670
		671	Example:
		672
		673	# stat all files in @files, but only ever use four aio requests concurrently:
		674
		675	my $grp = aio_group sub { print "finished\n" };
		676	$grp->feeder_limit (4);
		677	$grp->set_feeder (sub {
		678	my $file = pop @files
		679	or return;
		680
		681	add $grp aio_stat $file, sub { ... };
		682	});
		683
		684	=item $grp->feeder_limit ($num)
		685
		686	Sets the feeder limit for the group: The feeder will be called whenever
		687	the group contains less than this many requests.
		688
		689	Setting the limit to C<0> will pause the feeding process.
400		690
401	=back	691	=back
402		692
403	=head2 SUPPORT FUNCTIONS	693	=head2 SUPPORT FUNCTIONS
404		694
…		…
462	IO::AIO::poll_wait, IO::AIO::poll_cb	752	IO::AIO::poll_wait, IO::AIO::poll_cb
463	if IO::AIO::nreqs;	753	if IO::AIO::nreqs;
464		754
465	=item IO::AIO::min_parallel $nthreads	755	=item IO::AIO::min_parallel $nthreads
466		756
467	Set the minimum number of AIO threads to C<$nthreads>. The current default	757	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	758	default is C<8>, which means eight asynchronous operations can execute
469	(the number of outstanding operations, however, is unlimited).	759	concurrently at any one time (the number of outstanding requests,
		760	however, is unlimited).
470		761
471	IO::AIO starts threads only on demand, when an AIO request is queued and	762	IO::AIO starts threads only on demand, when an AIO request is queued and
472	no free thread exists.	763	no free thread exists.
473		764
474	It is recommended to keep the number of threads low, as some Linux	765	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	766	Linux kernel versions will scale negatively with the number of threads
476	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	767	(higher parallelity => MUCH higher latency). With current Linux 2.6
477	threads should be fine.	768	versions, 4-32 threads should be fine.
478		769
479	Under most circumstances you don't need to call this function, as the	770	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.	771	module selects a default that is suitable for low to moderate load.
481		772
482	=item IO::AIO::max_parallel $nthreads	773	=item IO::AIO::max_parallel $nthreads
…		…
523	or return undef;	814	or return undef;
524		815
525	*$sym	816	*$sym
526	}	817	}
527		818
528	min_parallel 4;	819	min_parallel 8;
529		820
530	END {	821	END {
531	max_parallel 0;	822	max_parallel 0;
532	}	823	}
533		824
534	1;	825	1;
535		826
536	=head2 FORK BEHAVIOUR	827	=head2 FORK BEHAVIOUR
		828
		829	This module should do "the right thing" when the process using it forks:
537		830
538	Before the fork, IO::AIO enters a quiescent state where no requests	831	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	832	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	833	the fork the parent simply leaves the quiescent state and continues
541	request/result processing, while the child clears the request/result	834	request/result processing, while the child clears the request/result
542	queue (so the requests started before the fork will only be handled in	835	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	836	the parent). Threads will be started on demand until the limit ste in the
544	parent process has been reached again.	837	parent process has been reached again.
545		838
		839	In short: the parent will, after a short pause, continue as if fork had
		840	not been called, while the child will act as if IO::AIO has not been used
		841	yet.
		842
		843	=head2 MEMORY USAGE
		844
		845	Each aio request uses - depending on your architecture - around 128 bytes
		846	of memory. In addition, stat requests need a stat buffer (possibly a few
		847	hundred bytes). Perl scalars and other data passed into aio requests will
		848	also be locked.
		849
		850	This is now awfully much, so queuing lots of requests is not usually a
		851	problem.
		852
		853	Each thread needs a stack area which is usually around 16k, sometimes much
		854	larger, depending on the OS.
		855
546	=head1 SEE ALSO	856	=head1 SEE ALSO
547		857
548	L<Coro>, L<Linux::AIO>.	858	L<Coro>, L<Linux::AIO> (obsolete).
549		859
550	=head1 AUTHOR	860	=head1 AUTHOR
551		861
552	Marc Lehmann <schmorp@schmorp.de>	862	Marc Lehmann <schmorp@schmorp.de>
553	http://home.schmorp.de/	863	http://home.schmorp.de/

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Revision 1.47 by root, Thu Dec 29 15:44:13 2005 UTC vs.
Revision 1.61 by root, Sun Oct 22 13:52:11 2006 UTC