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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.28 by root, Tue Aug 16 23:33:34 2005 UTC vs.
Revision 1.55 by root, Sun Oct 22 00:49:29 2006 UTC

…		…
14	aio_unlink "/tmp/file", sub { };	14	aio_unlink "/tmp/file", sub { };
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
		20	use IO::AIO 2; # version has aio objects
		21
		22	my $req = aio_unlink "/tmp/file", sub { };
		23	$req->cancel; # cancel request if still in queue
		24
		25	# AnyEvent
		26	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		27	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
19		28
20	# Event	29	# Event
21	Event->io (fd => IO::AIO::poll_fileno,	30	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	31	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	32	cb => \&IO::AIO::poll_cb);
…		…
57	=cut	66	=cut
58		67
59	package IO::AIO;	68	package IO::AIO;
60		69
61	no warnings;	70	no warnings;
		71	use strict 'vars';
62		72
63	use base 'Exporter';	73	use base 'Exporter';
64		74
65	use Fcntl ();
66
67	BEGIN {	75	BEGIN {
68	$VERSION = 1.2;	76	our $VERSION = '2.0';
69		77
70	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	78	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71	aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead);	79	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
		80	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		81	aio_group);
72	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	82	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
		83
		84	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
73		85
74	require XSLoader;	86	require XSLoader;
75	XSLoader::load IO::AIO, $VERSION;	87	XSLoader::load ("IO::AIO", $VERSION);
76	}	88	}
77		89
78	=head1 FUNCTIONS	90	=head1 FUNCTIONS
79		91
80	=head2 AIO FUNCTIONS	92	=head2 AIO FUNCTIONS
…		…
88	syscall has been executed asynchronously.	100	syscall has been executed asynchronously.
89		101
90	All functions expecting a filehandle keep a copy of the filehandle	102	All functions expecting a filehandle keep a copy of the filehandle
91	internally until the request has finished.	103	internally until the request has finished.
92		104
		105	All requests return objects of type L<IO::AIO::REQ> that allow further
		106	manipulation of those requests while they are in-flight.
		107
93	The pathnames you pass to these routines I<must> be absolute and	108	The pathnames you pass to these routines I<must> be absolute and
94	encoded in byte form. The reason for the former is that at the time the	109	encoded in byte form. The reason for the former is that at the time the
95	request is being executed, the current working directory could have	110	request is being executed, the current working directory could have
96	changed. Alternatively, you can make sure that you never change the	111	changed. Alternatively, you can make sure that you never change the
97	current working directory.	112	current working directory.
…		…
103	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	118	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
104	use something else.	119	use something else.
105		120
106	=over 4	121	=over 4
107		122
108	=item aio_open $pathname, $flags, $mode, $callback	123	=item aio_open $pathname, $flags, $mode, $callback->($fh)
109		124
110	Asynchronously open or create a file and call the callback with a newly	125	Asynchronously open or create a file and call the callback with a newly
111	created filehandle for the file.	126	created filehandle for the file.
112		127
113	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	128	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
130	} else {	145	} else {
131	die "open failed: $!\n";	146	die "open failed: $!\n";
132	}	147	}
133	};	148	};
134		149
135	=item aio_close $fh, $callback	150	=item aio_close $fh, $callback->($status)
136		151
137	Asynchronously close a file and call the callback with the result	152	Asynchronously close a file and call the callback with the result
138	code. I<WARNING:> although accepted, you should not pass in a perl	153	code. I<WARNING:> although accepted, you should not pass in a perl
139	filehandle here, as perl will likely close the file descriptor another	154	filehandle here, as perl will likely close the file descriptor another
140	time when the filehandle is destroyed. Normally, you can safely call perls	155	time when the filehandle is destroyed. Normally, you can safely call perls
141	C<close> or just let filehandles go out of scope.	156	C<close> or just let filehandles go out of scope.
142		157
143	This is supposed to be a bug in the API, so that might change. It's	158	This is supposed to be a bug in the API, so that might change. It's
144	therefore best to avoid this function.	159	therefore best to avoid this function.
145		160
146	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	161	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
147		162
148	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	163	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149		164
150	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	165	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
151	into the scalar given by C<data> and offset C<dataoffset> and calls the	166	into the scalar given by C<data> and offset C<dataoffset> and calls the
152	callback without the actual number of bytes read (or -1 on error, just	167	callback without the actual number of bytes read (or -1 on error, just
153	like the syscall).	168	like the syscall).
154		169
		170	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		171	is outstanding. Modifying it can result in segfaults or WW3 (if the
		172	necessary/optional hardware is installed).
		173
155	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	174	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
156	offset C<0> within the scalar:	175	offset C<0> within the scalar:
157		176
158	aio_read $fh, 7, 15, $buffer, 0, sub {	177	aio_read $fh, 7, 15, $buffer, 0, sub {
159	$_[0] > 0 or die "read error: $!";	178	$_[0] > 0 or die "read error: $!";
160	print "read $_[0] bytes: <$buffer>\n";	179	print "read $_[0] bytes: <$buffer>\n";
161	};	180	};
162		181
		182	=item aio_move $srcpath, $dstpath, $callback->($status)
		183
		184	Try to move the I<file> (directories not supported as either source or
		185	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		186	the C<0> (error) or C<-1> ok.
		187
		188	This is a composite request that tries to rename(2) the file first. If
		189	rename files with C<EXDEV>, it creates the destination file with mode 0200
		190	and copies the contents of the source file into it using C<aio_sendfile>,
		191	followed by restoring atime, mtime, access mode and uid/gid, in that
		192	order, and unlinking the C<$srcpath>.
		193
		194	If an error occurs, the partial destination file will be unlinked, if
		195	possible, except when setting atime, mtime, access mode and uid/gid, where
		196	errors are being ignored.
		197
		198	=cut
		199
		200	sub aio_move($$$) {
		201	my ($src, $dst, $cb) = @_;
		202
		203	my $grp = aio_group;
		204
		205	add $grp aio_rename $src, $dst, sub {
		206	if ($_[0] && $! == EXDEV) {
		207	add $grp aio_open $src, O_RDONLY, 0, sub {
		208	if (my $src_fh = $_[0]) {
		209	my @stat = stat $src_fh;
		210
		211	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		212	if (my $dst_fh = $_[0]) {
		213	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		214	close $src_fh;
		215
		216	if ($_[0] == $stat[7]) {
		217	utime $stat[8], $stat[9], $dst;
		218	chmod $stat[2] & 07777, $dst_fh;
		219	chown $stat[4], $stat[5], $dst_fh;
		220	close $dst_fh;
		221
		222	add $grp aio_unlink $src, sub {
		223	$cb->($_[0]);
		224	};
		225	} else {
		226	my $errno = $!;
		227	add $grp aio_unlink $dst, sub {
		228	$! = $errno;
		229	$cb->(-1);
		230	};
		231	}
		232	};
		233	} else {
		234	$cb->(-1);
		235	}
		236	},
		237
		238	} else {
		239	$cb->(-1);
		240	}
		241	};
		242	} else {
		243	$cb->($_[0]);
		244	}
		245	};
		246
		247	$grp
		248	}
		249
		250	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		251
		252	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		253	reading at byte offset C<$in_offset>, and starts writing at the current
		254	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		255	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		256	other.
		257
		258	This call tries to make use of a native C<sendfile> syscall to provide
		259	zero-copy operation. For this to work, C<$out_fh> should refer to a
		260	socket, and C<$in_fh> should refer to mmap'able file.
		261
		262	If the native sendfile call fails or is not implemented, it will be
		263	emulated, so you can call C<aio_sendfile> on any type of filehandle
		264	regardless of the limitations of the operating system.
		265
		266	Please note, however, that C<aio_sendfile> can read more bytes from
		267	C<$in_fh> than are written, and there is no way to find out how many
		268	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		269	provides the number of bytes written to C<$out_fh>. Only if the result
		270	value equals C<$length> one can assume that C<$length> bytes have been
		271	read.
		272
163	=item aio_readahead $fh,$offset,$length, $callback	273	=item aio_readahead $fh,$offset,$length, $callback->($retval)
164		274
165	C<aio_readahead> populates the page cache with data from a file so that	275	C<aio_readahead> populates the page cache with data from a file so that
166	subsequent reads from that file will not block on disk I/O. The C<$offset>	276	subsequent reads from that file will not block on disk I/O. The C<$offset>
167	argument specifies the starting point from which data is to be read and	277	argument specifies the starting point from which data is to be read and
168	C<$length> specifies the number of bytes to be read. I/O is performed in	278	C<$length> specifies the number of bytes to be read. I/O is performed in
…		…
172	file. The current file offset of the file is left unchanged.	282	file. The current file offset of the file is left unchanged.
173		283
174	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	284	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
175	emulated by simply reading the data, which would have a similar effect.	285	emulated by simply reading the data, which would have a similar effect.
176		286
177	=item aio_stat $fh_or_path, $callback	287	=item aio_stat $fh_or_path, $callback->($status)
178		288
179	=item aio_lstat $fh, $callback	289	=item aio_lstat $fh, $callback->($status)
180		290
181	Works like perl's C<stat> or C<lstat> in void context. The callback will	291	Works like perl's C<stat> or C<lstat> in void context. The callback will
182	be called after the stat and the results will be available using C<stat _>	292	be called after the stat and the results will be available using C<stat _>
183	or C<-s _> etc...	293	or C<-s _> etc...
184		294
…		…
194	aio_stat "/etc/passwd", sub {	304	aio_stat "/etc/passwd", sub {
195	$_[0] and die "stat failed: $!";	305	$_[0] and die "stat failed: $!";
196	print "size is ", -s _, "\n";	306	print "size is ", -s _, "\n";
197	};	307	};
198		308
199	=item aio_unlink $pathname, $callback	309	=item aio_unlink $pathname, $callback->($status)
200		310
201	Asynchronously unlink (delete) a file and call the callback with the	311	Asynchronously unlink (delete) a file and call the callback with the
202	result code.	312	result code.
203		313
		314	=item aio_link $srcpath, $dstpath, $callback->($status)
		315
		316	Asynchronously create a new link to the existing object at C<$srcpath> at
		317	the path C<$dstpath> and call the callback with the result code.
		318
		319	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		320
		321	Asynchronously create a new symbolic 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_rename $srcpath, $dstpath, $callback->($status)
		325
		326	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		327	rename(2) and call the callback with the result code.
		328
204	=item aio_rmdir $pathname, $callback	329	=item aio_rmdir $pathname, $callback->($status)
205		330
206	Asynchronously rmdir (delete) a directory and call the callback with the	331	Asynchronously rmdir (delete) a directory and call the callback with the
207	result code.	332	result code.
208		333
		334	=item aio_readdir $pathname, $callback->($entries)
		335
		336	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		337	directory (i.e. opendir + readdir + closedir). The entries will not be
		338	sorted, and will B<NOT> include the C<.> and C<..> entries.
		339
		340	The callback a single argument which is either C<undef> or an array-ref
		341	with the filenames.
		342
		343	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		344
		345	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		346	separate the entries of directory C<$path> into two sets of names, ones
		347	you can recurse into (directories or links to them), and ones you cannot
		348	recurse into (everything else).
		349
		350	C<aio_scandir> is a composite request that consists of many sub
		351	requests. C<$maxreq> specifies the maximum number of outstanding aio
		352	requests that this function generates. If it is C<< <= 0 >>, then a
		353	suitable default will be chosen (currently 8).
		354
		355	On error, the callback is called without arguments, otherwise it receives
		356	two array-refs with path-relative entry names.
		357
		358	Example:
		359
		360	aio_scandir $dir, 0, sub {
		361	my ($dirs, $nondirs) = @_;
		362	print "real directories: @$dirs\n";
		363	print "everything else: @$nondirs\n";
		364	};
		365
		366	Implementation notes.
		367
		368	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		369
		370	After reading the directory, the modification time, size etc. of the
		371	directory before and after the readdir is checked, and if they match (and
		372	isn't the current time), the link count will be used to decide how many
		373	entries are directories (if >= 2). Otherwise, no knowledge of the number
		374	of subdirectories will be assumed.
		375
		376	Then entries will be sorted into likely directories (everything without
		377	a non-initial dot currently) and likely non-directories (everything
		378	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		379	likely directories first. If that succeeds, it assumes that the entry
		380	is a directory or a symlink to directory (which will be checked
		381	seperately). This is often faster than stat'ing the entry itself because
		382	filesystems might detect the type of the entry without reading the inode
		383	data (e.g. ext2fs filetype feature).
		384
		385	If the known number of directories (link count - 2) has been reached, the
		386	rest of the entries is assumed to be non-directories.
		387
		388	This only works with certainty on POSIX (= UNIX) filesystems, which
		389	fortunately are the vast majority of filesystems around.
		390
		391	It will also likely work on non-POSIX filesystems with reduced efficiency
		392	as those tend to return 0 or 1 as link counts, which disables the
		393	directory counting heuristic.
		394
		395	=cut
		396
		397	sub aio_scandir($$$) {
		398	my ($path, $maxreq, $cb) = @_;
		399
		400	my $grp = aio_group;
		401
		402	$maxreq = 8 if $maxreq <= 0;
		403
		404	# stat once
		405	add $grp aio_stat $path, sub {
		406	return $cb->() if $_[0];
		407	my $now = time;
		408	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		409
		410	# read the directory entries
		411	add $grp aio_readdir $path, sub {
		412	my $entries = shift
		413	or return $cb->();
		414
		415	# stat the dir another time
		416	add $grp aio_stat $path, sub {
		417	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		418
		419	my $ndirs;
		420
		421	# take the slow route if anything looks fishy
		422	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		423	$ndirs = -1;
		424	} else {
		425	# if nlink == 2, we are finished
		426	# on non-posix-fs's, we rely on nlink < 2
		427	$ndirs = (stat _)[3] - 2
		428	or return $cb->([], $entries);
		429	}
		430
		431	# sort into likely dirs and likely nondirs
		432	# dirs == files without ".", short entries first
		433	$entries = [map $_->[0],
		434	sort { $b->[1] cmp $a->[1] }
		435	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		436	@$entries];
		437
		438	my (@dirs, @nondirs);
		439
		440	my ($statcb, $schedcb);
		441	my $nreq = 0;
		442
		443	$schedcb = sub {
		444	if (@$entries) {
		445	if ($nreq < $maxreq) {
		446	my $ent = pop @$entries;
		447	$nreq++;
		448	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		449	}
		450	} elsif (!$nreq) {
		451	# finished
		452	undef $statcb;
		453	undef $schedcb;
		454	$cb->(\@dirs, \@nondirs) if $cb;
		455	undef $cb;
		456	}
		457	};
		458	$statcb = sub {
		459	my ($status, $entry) = @_;
		460
		461	if ($status < 0) {
		462	$nreq--;
		463	push @nondirs, $entry;
		464	&$schedcb;
		465	} else {
		466	# need to check for real directory
		467	add $grp aio_lstat "$path/$entry", sub {
		468	$nreq--;
		469
		470	if (-d _) {
		471	push @dirs, $entry;
		472
		473	if (!--$ndirs) {
		474	push @nondirs, @$entries;
		475	$entries = [];
		476	}
		477	} else {
		478	push @nondirs, $entry;
		479	}
		480
		481	&$schedcb;
		482	}
		483	}
		484	};
		485
		486	&$schedcb while @$entries && $nreq < $maxreq;
		487	};
		488	};
		489	};
		490
		491	$grp
		492	}
		493
209	=item aio_fsync $fh, $callback	494	=item aio_fsync $fh, $callback->($status)
210		495
211	Asynchronously call fsync on the given filehandle and call the callback	496	Asynchronously call fsync on the given filehandle and call the callback
212	with the fsync result code.	497	with the fsync result code.
213		498
214	=item aio_fdatasync $fh, $callback	499	=item aio_fdatasync $fh, $callback->($status)
215		500
216	Asynchronously call fdatasync on the given filehandle and call the	501	Asynchronously call fdatasync on the given filehandle and call the
217	callback with the fdatasync result code.	502	callback with the fdatasync result code.
218		503
219	If this call isn't available because your OS lacks it or it couldn't be	504	If this call isn't available because your OS lacks it or it couldn't be
220	detected, it will be emulated by calling C<fsync> instead.	505	detected, it will be emulated by calling C<fsync> instead.
		506
		507	=item aio_group $callback->()
		508
		509	[EXPERIMENTAL]
		510
		511	This is a very special aio request: Instead of doing something, it is a
		512	container for other aio requests, which is useful if you want to bundle
		513	many requests into a single, composite, request.
		514
		515	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		516	for more info.
		517
		518	Example:
		519
		520	my $grp = aio_group sub {
		521	print "all stats done\n";
		522	};
		523
		524	add $grp
		525	(aio_stat ...),
		526	(aio_stat ...),
		527	...;
		528
		529	=item aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		530
		531	Mainly used for debugging and benchmarking, this aio request puts one of
		532	the request workers to sleep for the given time.
		533
		534	=back
		535
		536	=head2 IO::AIO::REQ CLASS
		537
		538	All non-aggregate C<aio_*> functions return an object of this class when
		539	called in non-void context.
		540
		541	A request always moves through the following five states in its lifetime,
		542	in order: B<ready> (request has been created, but has not been executed
		543	yet), B<execute> (request is currently being executed), B<pending>
		544	(request has been executed but callback has not been called yet),
		545	B<result> (results are being processed synchronously, includes calling the
		546	callback) and B<done> (request has reached the end of its lifetime and
		547	holds no resources anymore).
		548
		549	=over 4
		550
		551	=item $req->cancel
		552
		553	Cancels the request, if possible. Has the effect of skipping execution
		554	when entering the B<execute> state and skipping calling the callback when
		555	entering the the B<result> state, but will leave the request otherwise
		556	untouched. That means that requests that currently execute will not be
		557	stopped and resources held by the request will not be freed prematurely.
		558
		559	=back
		560
		561	=head2 IO::AIO::GRP CLASS
		562
		563	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		564	objects of this class, too.
		565
		566	A IO::AIO::GRP object is a special request that can contain multiple other
		567	aio requests.
		568
		569	You create one by calling the C<aio_group> constructing function with a
		570	callback that will be called when all contained requests have entered the
		571	C<done> state:
		572
		573	my $grp = aio_group sub {
		574	print "all requests are done\n";
		575	};
		576
		577	You add requests by calling the C<add> method with one or more
		578	C<IO::AIO::REQ> objects:
		579
		580	$grp->add (aio_unlink "...");
		581
		582	add $grp aio_stat "...", sub { ... };
		583
		584	This makes it very easy to create composite requests (see the source of
		585	C<aio_move> for an application) that work and feel like simple requests.
		586
		587	The IO::AIO::GRP objects will be cleaned up during calls to
		588	C<IO::AIO::poll_cb>, just like any other request.
		589
		590	They can be canceled like any other request. Canceling will cancel not
		591	just the request itself, but also all requests it contains.
		592
		593	They can also can also be added to other IO::AIO::GRP objects.
		594
		595	Their lifetime, simplified, looks like this: when they are empty, they
		596	will finish very quickly. If they contain only requests that are in the
		597	C<done> state, they will also finish. Otherwise they will continue to
		598	exist.
		599
		600	=over 4
		601
		602	=item $grp->add (...)
		603
		604	=item add $grp ...
		605
		606	Add one or more
		607	Cancels the request, if possible. Has the effect of skipping execution
		608	when entering the B<execute> state and skipping calling the callback when
		609	entering the the B<result> state, but will leave the request otherwise
		610	untouched. That means that requests that currently execute will not be
		611	stopped and resources held by the request will not be freed prematurely.
221		612
222	=back	613	=back
223		614
224	=head2 SUPPORT FUNCTIONS	615	=head2 SUPPORT FUNCTIONS
225		616
…		…
283	IO::AIO::poll_wait, IO::AIO::poll_cb	674	IO::AIO::poll_wait, IO::AIO::poll_cb
284	if IO::AIO::nreqs;	675	if IO::AIO::nreqs;
285		676
286	=item IO::AIO::min_parallel $nthreads	677	=item IO::AIO::min_parallel $nthreads
287		678
288	Set the minimum number of AIO threads to C<$nthreads>. The default is	679	Set the minimum number of AIO threads to C<$nthreads>. The current default
289	C<1>, which means a single asynchronous operation can be done at one time	680	is C<4>, which means four asynchronous operations can be done at one time
290	(the number of outstanding operations, however, is unlimited).	681	(the number of outstanding operations, however, is unlimited).
		682
		683	IO::AIO starts threads only on demand, when an AIO request is queued and
		684	no free thread exists.
291		685
292	It is recommended to keep the number of threads low, as some Linux	686	It is recommended to keep the number of threads low, as some Linux
293	kernel versions will scale negatively with the number of threads (higher	687	kernel versions will scale negatively with the number of threads (higher
294	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	688	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
295	threads should be fine.	689	threads should be fine.
296		690
297	Under normal circumstances you don't need to call this function, as this	691	Under most circumstances you don't need to call this function, as the
298	module automatically starts some threads (the exact number might change,	692	module selects a default that is suitable for low to moderate load.
299	and is currently 4).
300		693
301	=item IO::AIO::max_parallel $nthreads	694	=item IO::AIO::max_parallel $nthreads
302		695
303	Sets the maximum number of AIO threads to C<$nthreads>. If more than	696	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
304	the specified number of threads are currently running, kill them. This	697	specified number of threads are currently running, this function kills
305	function blocks until the limit is reached.	698	them. This function blocks until the limit is reached.
		699
		700	While C<$nthreads> are zero, aio requests get queued but not executed
		701	until the number of threads has been increased again.
306		702
307	This module automatically runs C<max_parallel 0> at program end, to ensure	703	This module automatically runs C<max_parallel 0> at program end, to ensure
308	that all threads are killed and that there are no outstanding requests.	704	that all threads are killed and that there are no outstanding requests.
309		705
310	Under normal circumstances you don't need to call this function.	706	Under normal circumstances you don't need to call this function.
…		…
314	Sets the maximum number of outstanding requests to C<$nreqs>. If you	710	Sets the maximum number of outstanding requests to C<$nreqs>. If you
315	try to queue up more than this number of requests, the caller will block until	711	try to queue up more than this number of requests, the caller will block until
316	some requests have been handled.	712	some requests have been handled.
317		713
318	The default is very large, so normally there is no practical limit. If you	714	The default is very large, so normally there is no practical limit. If you
319	queue up many requests in a loop it it often improves speed if you set	715	queue up many requests in a loop it often improves speed if you set
320	this to a relatively low number, such as C<100>.	716	this to a relatively low number, such as C<100>.
321		717
322	Under normal circumstances you don't need to call this function.	718	Under normal circumstances you don't need to call this function.
323		719
324	=back	720	=back
…		…
349		745
350	1;	746	1;
351		747
352	=head2 FORK BEHAVIOUR	748	=head2 FORK BEHAVIOUR
353		749
354	IO::AIO handles all outstanding AIO requests before the fork, destroys all	750	This module should do "the right thing" when the process using it forks:
355	AIO threads, and recreates them in both the parent and the child after the
356	fork.
357		751
		752	Before the fork, IO::AIO enters a quiescent state where no requests
		753	can be added in other threads and no results will be processed. After
		754	the fork the parent simply leaves the quiescent state and continues
		755	request/result processing, while the child clears the request/result
		756	queue (so the requests started before the fork will only be handled in
		757	the parent). Threads will be started on demand until the limit ste in the
		758	parent process has been reached again.
		759
		760	In short: the parent will, after a short pause, continue as if fork had
		761	not been called, while the child will act as if IO::AIO has not been used
		762	yet.
358		763
359	=head1 SEE ALSO	764	=head1 SEE ALSO
360		765
361	L<Coro>, L<Linux::AIO>.	766	L<Coro>, L<Linux::AIO> (obsolete).
362		767
363	=head1 AUTHOR	768	=head1 AUTHOR
364		769
365	Marc Lehmann <schmorp@schmorp.de>	770	Marc Lehmann <schmorp@schmorp.de>
366	http://home.schmorp.de/	771	http://home.schmorp.de/

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Revision 1.55 by root, Sun Oct 22 00:49:29 2006 UTC