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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.5 by root, Sun Jul 10 21:04:24 2005 UTC vs.
Revision 1.40 by root, Tue Aug 30 15:45:10 2005 UTC

…		…
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
		8
		9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		10	my ($fh) = @_;
		11	...
		12	};
		13
		14	aio_unlink "/tmp/file", sub { };
		15
		16	aio_read $fh, 30000, 1024, $buffer, 0, sub {
		17	$_[0] > 0 or die "read error: $!";
		18	};
		19
		20	# Event
		21	Event->io (fd => IO::AIO::poll_fileno,
		22	poll => 'r',
		23	cb => \&IO::AIO::poll_cb);
		24
		25	# Glib/Gtk2
		26	add_watch Glib::IO IO::AIO::poll_fileno,
		27	in => sub { IO::AIO::poll_cb; 1 };
		28
		29	# Tk
		30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		31	readable => \&IO::AIO::poll_cb);
		32
		33	# Danga::Socket
		34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		35	\&IO::AIO::poll_cb);
		36
8		37
9	=head1 DESCRIPTION	38	=head1 DESCRIPTION
10		39
11	This module implements asynchronous I/O using whatever means your	40	This module implements asynchronous I/O using whatever means your
12	operating system supports.	41	operating system supports.
…		…
19	not well-supported (Linux doesn't allow them on normal files currently,	48	not well-supported (Linux doesn't allow them on normal files currently,
20	for example), and they would only support aio_read and aio_write, so the	49	for example), and they would only support aio_read and aio_write, so the
21	remaining functionality would have to be implemented using threads anyway.	50	remaining functionality would have to be implemented using threads anyway.
22		51
23	Although the module will work with in the presence of other threads, it is	52	Although the module will work with in the presence of other threads, it is
24	currently not reentrant, so use appropriate locking yourself.	53	currently not reentrant, so use appropriate locking yourself, always call
		54	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other
		55	C<aio_> functions) recursively.
25		56
26	=cut	57	=cut
27		58
28	package IO::AIO;	59	package IO::AIO;
29		60
		61	no warnings;
		62
30	use base 'Exporter';	63	use base 'Exporter';
31		64
32	use Fcntl ();	65	use Fcntl ();
33		66
34	BEGIN {	67	BEGIN {
35	$VERSION = 0.2;	68	$VERSION = 1.6;
36		69
37	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	70	@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
38	aio_fsync aio_fdatasync aio_readahead);	72	aio_fsync aio_fdatasync aio_readahead);
39	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	73	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel
		74	max_outstanding nreqs);
40		75
41	require XSLoader;	76	require XSLoader;
42	XSLoader::load IO::AIO, $VERSION;	77	XSLoader::load IO::AIO, $VERSION;
43	}	78	}
44		79
…		…
46		81
47	=head2 AIO FUNCTIONS	82	=head2 AIO FUNCTIONS
48		83
49	All the C<aio_*> calls are more or less thin wrappers around the syscall	84	All the C<aio_*> calls are more or less thin wrappers around the syscall
50	with the same name (sans C<aio_>). The arguments are similar or identical,	85	with the same name (sans C<aio_>). The arguments are similar or identical,
51	and they all accept an additional C<$callback> argument which must be	86	and they all accept an additional (and optional) C<$callback> argument
52	a code reference. This code reference will get called with the syscall	87	which must be a code reference. This code reference will get called with
53	return code (e.g. most syscalls return C<-1> on error, unlike perl, which	88	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
54	usually delivers "false") as it's sole argument when the given syscall has	89	perl, which usually delivers "false") as it's sole argument when the given
55	been executed asynchronously.	90	syscall has been executed asynchronously.
56		91
57	All functions that expect a filehandle will also accept a file descriptor.	92	All functions expecting a filehandle keep a copy of the filehandle
		93	internally until the request has finished.
58		94
59	The filenames you pass to these routines I<must> be absolute. The reason	95	The pathnames you pass to these routines I<must> be absolute and
60	is that at the time the request is being executed, the current working	96	encoded in byte form. The reason for the former is that at the time the
61	directory could have changed. Alternatively, you can make sure that you	97	request is being executed, the current working directory could have
		98	changed. Alternatively, you can make sure that you never change the
62	never change the current working directory.	99	current working directory.
		100
		101	To encode pathnames to byte form, either make sure you either: a)
		102	always pass in filenames you got from outside (command line, readdir
		103	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		104	your pathnames to the locale (or other) encoding in effect in the user
		105	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		106	use something else.
63		107
64	=over 4	108	=over 4
65		109
66	=item aio_open $pathname, $flags, $mode, $callback	110	=item aio_open $pathname, $flags, $mode, $callback->($fh)
67		111
68	Asynchronously open or create a file and call the callback with a newly	112	Asynchronously open or create a file and call the callback with a newly
69	created filehandle for the file.	113	created filehandle for the file.
70		114
71	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	115	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
72	for an explanation.	116	for an explanation.
73		117
74	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	118	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
75	list. They are the same as used in C<sysopen>.	119	list. They are the same as used by C<sysopen>.
		120
		121	Likewise, C<$mode> specifies the mode of the newly created file, if it
		122	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		123	except that it is mandatory (i.e. use C<0> if you don't create new files,
		124	and C<0666> or C<0777> if you do).
76		125
77	Example:	126	Example:
78		127
79	aio_open "/etc/passwd", O_RDONLY, 0, sub {	128	aio_open "/etc/passwd", O_RDONLY, 0, sub {
80	if ($_[0]) {	129	if ($_[0]) {
…		…
83	} else {	132	} else {
84	die "open failed: $!\n";	133	die "open failed: $!\n";
85	}	134	}
86	};	135	};
87		136
88	=item aio_close $fh, $callback	137	=item aio_close $fh, $callback->($status)
89		138
90	Asynchronously close a file and call the callback with the result	139	Asynchronously close a file and call the callback with the result
91	code. I<WARNING:> although accepted, you should not pass in a perl	140	code. I<WARNING:> although accepted, you should not pass in a perl
92	filehandle here, as perl will likely close the file descriptor itself when	141	filehandle here, as perl will likely close the file descriptor another
93	the filehandle is destroyed. Normally, you can safely call perls C<close>	142	time when the filehandle is destroyed. Normally, you can safely call perls
94	or just let filehandles go out of scope.	143	C<close> or just let filehandles go out of scope.
95		144
		145	This is supposed to be a bug in the API, so that might change. It's
		146	therefore best to avoid this function.
		147
96	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	148	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
97		149
98	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	150	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
99		151
100	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	152	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
101	into the scalar given by C<data> and offset C<dataoffset> and calls the	153	into the scalar given by C<data> and offset C<dataoffset> and calls the
102	callback without the actual number of bytes read (or -1 on error, just	154	callback without the actual number of bytes read (or -1 on error, just
103	like the syscall).	155	like the syscall).
104		156
		157	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		158	is outstanding. Modifying it can result in segfaults or WW3 (if the
		159	necessary/optional hardware is installed).
		160
105	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	161	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
106	offset C<0> within the scalar:	162	offset C<0> within the scalar:
107		163
108	aio_read $fh, 7, 15, $buffer, 0, sub {	164	aio_read $fh, 7, 15, $buffer, 0, sub {
109	$_[0] >= 0 or die "read error: $!";	165	$_[0] > 0 or die "read error: $!";
110	print "read <$buffer>\n";	166	print "read $_[0] bytes: <$buffer>\n";
111	};	167	};
112		168
		169	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		170
		171	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
		173	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		174	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		175	other.
		176
		177	This call tries to make use of a native C<sendfile> syscall to provide
		178	zero-copy operation. For this to work, C<$out_fh> should refer to a
		179	socket, and C<$in_fh> should refer to mmap'able file.
		180
		181	If the native sendfile call fails or is not implemented, it will be
		182	emulated, so you can call C<aio_sendfile> on any type of filehandle
		183	regardless of the limitations of the operating system.
		184
		185	Please note, however, that C<aio_sendfile> can read more bytes from
		186	C<$in_fh> than are written, and there is no way to find out how many
		187	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		188	provides the number of bytes written to C<$out_fh>. Only if the result
		189	value equals C<$length> one can assume that C<$length> bytes have been
		190	read.
		191
113	=item aio_readahead $fh,$offset,$length, $callback	192	=item aio_readahead $fh,$offset,$length, $callback->($retval)
114		193
115	Asynchronously reads the specified byte range into the page cache, using
116	the C<readahead> syscall. If that syscall doesn't exist the status will be
117	C<-1> and C<$!> is set to ENOSYS.
118
119	readahead() populates the page cache with data from a file so that	194	C<aio_readahead> populates the page cache with data from a file so that
120	subsequent reads from that file will not block on disk I/O. The C<$offset>	195	subsequent reads from that file will not block on disk I/O. The C<$offset>
121	argument specifies the starting point from which data is to be read and	196	argument specifies the starting point from which data is to be read and
122	C<$length> specifies the number of bytes to be read. I/O is performed in	197	C<$length> specifies the number of bytes to be read. I/O is performed in
123	whole pages, so that offset is effectively rounded down to a page boundary	198	whole pages, so that offset is effectively rounded down to a page boundary
124	and bytes are read up to the next page boundary greater than or equal to	199	and bytes are read up to the next page boundary greater than or equal to
125	(off-set+length). aio_readahead() does not read beyond the end of the	200	(off-set+length). C<aio_readahead> does not read beyond the end of the
126	file. The current file offset of the file is left unchanged.	201	file. The current file offset of the file is left unchanged.
127		202
		203	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		204	emulated by simply reading the data, which would have a similar effect.
		205
128	=item aio_stat $fh_or_path, $callback	206	=item aio_stat $fh_or_path, $callback->($status)
129		207
130	=item aio_lstat $fh, $callback	208	=item aio_lstat $fh, $callback->($status)
131		209
132	Works like perl's C<stat> or C<lstat> in void context. The callback will	210	Works like perl's C<stat> or C<lstat> in void context. The callback will
133	be called after the stat and the results will be available using C<stat _>	211	be called after the stat and the results will be available using C<stat _>
134	or C<-s _> etc...	212	or C<-s _> etc...
135		213
…		…
145	aio_stat "/etc/passwd", sub {	223	aio_stat "/etc/passwd", sub {
146	$_[0] and die "stat failed: $!";	224	$_[0] and die "stat failed: $!";
147	print "size is ", -s _, "\n";	225	print "size is ", -s _, "\n";
148	};	226	};
149		227
150	=item aio_unlink $pathname, $callback	228	=item aio_unlink $pathname, $callback->($status)
151		229
152	Asynchronously unlink (delete) a file and call the callback with the	230	Asynchronously unlink (delete) a file and call the callback with the
153	result code.	231	result code.
154		232
		233	=item aio_rmdir $pathname, $callback->($status)
		234
		235	Asynchronously rmdir (delete) a directory and call the callback with the
		236	result code.
		237
		238	=item aio_readdir $pathname $callback->($entries)
		239
		240	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
		242	sorted, and will B<NOT> include the C<.> and C<..> entries.
		243
		244	The callback a single argument which is either C<undef> or an array-ref
		245	with the filenames.
		246
		247	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		248
		249	Scans a directory (similar to C<aio_readdir>) and tries to separate the
		250	entries of directory C<$path> into two sets of names, ones you can recurse
		251	into (directories), and ones you cannot recurse into (everything else).
		252
		253	C<aio_scandir> is a composite request that consists of many
		254	aio-primitives. C<$maxreq> specifies the maximum number of outstanding
		255	aio requests that this function generates. If it is C<< <= 0 >>, then a
		256	suitable default will be chosen (currently 8).
		257
		258	On error, the callback is called without arguments, otherwise it receives
		259	two array-refs with path-relative entry names.
		260
		261	Example:
		262
		263	aio_scandir $dir, 0, sub {
		264	my ($dirs, $nondirs) = @_;
		265	print "real directories: @$dirs\n";
		266	print "everything else: @$nondirs\n";
		267	};
		268
		269	Implementation notes.
		270
		271	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		272
		273	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
		275	link count will be used to decide how many entries are directories (if
		276	>= 2). Otherwise, no knowledge of the number of subdirectories will be
		277	assumed.
		278
		279	Then entires will be sorted into likely directories (everything without a
		280	non-initial dot) and likely non-directories (everything else). Then every
		281	entry + C</.> will be C<stat>'ed, likely directories first. This is often
		282	faster because filesystems might detect the type of the entry without
		283	reading the inode data (e.g. ext2s filetype feature). If that succeeds,
		284	it assumes that the entry is a directory or a symlink to directory (which
		285	will be checked seperately).
		286
		287	If the known number of directories has been reached, the rest of the
		288	entries is assumed to be non-directories.
		289
		290	=cut
		291
		292	sub aio_scandir($$$) {
		293	my ($path, $maxreq, $cb) = @_;
		294
		295	$maxreq = 8 if $maxreq <= 0;
		296
		297	# stat once
		298	aio_stat $path, sub {
		299	$cb->() if $_[0];
		300	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		301
		302	# read the directory entries
		303	aio_readdir $path, sub {
		304	my $entries = shift
		305	or return $cb->();
		306
		307	# stat the dir another time
		308	aio_stat $path, sub {
		309	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		310
		311	my $ndirs;
		312
		313	# take the slow route if anything looks fishy
		314	if ($hash1 ne $hash2) {
		315	$ndirs = -1;
		316	} else {
		317	# if nlink == 2, we are finished
		318	# on non-posix-fs's, we rely on nlink < 2
		319	$ndirs = (stat _)[3] - 2
		320	or $cb->([], $entries);
		321	}
		322
		323	# sort into likely dirs and likely nondirs
		324	# dirs == files without ".", short entries first
		325	$entries = [map $_->[0],
		326	sort { $b->[1] cmp $a->[1] }
		327	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		328	@$entries];
		329
		330	my (@dirs, @nondirs);
		331
		332	my ($statcb, $schedcb);
		333	my $nreq = 0;
		334
		335	$schedcb = sub {
		336	if (@$entries) {
		337	if ($nreq < $maxreq) {
		338	my $ent = pop @$entries;
		339	$nreq++;
		340	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		341	}
		342	} elsif (!$nreq) {
		343	# finished
		344	undef $statcb;
		345	undef $schedcb;
		346	$cb->(\@dirs, \@nondirs);
		347	undef $cb;
		348	}
		349	};
		350	$statcb = sub {
		351	my ($status, $entry) = @_;
		352
		353	if ($status < 0) {
		354	$nreq--;
		355	push @nondirs, $entry;
		356	&$schedcb;
		357	} else {
		358	# need to check for real directory
		359	aio_lstat "$path/$entry", sub {
		360	$nreq--;
		361
		362	if (-d _) {
		363	push @dirs, $entry;
		364
		365	if (!--$ndirs) {
		366	push @nondirs, @$entries;
		367	$entries = [];
		368	}
		369	} else {
		370	push @nondirs, $entry;
		371	}
		372
		373	&$schedcb;
		374	}
		375	}
		376	};
		377
		378	&$schedcb while @$entries && $nreq < $maxreq;
		379	};
		380	};
		381	};
		382	}
		383
155	=item aio_fsync $fh, $callback	384	=item aio_fsync $fh, $callback->($status)
156		385
157	Asynchronously call fsync on the given filehandle and call the callback	386	Asynchronously call fsync on the given filehandle and call the callback
158	with the fsync result code.	387	with the fsync result code.
159		388
160	=item aio_fdatasync $fh, $callback	389	=item aio_fdatasync $fh, $callback->($status)
161		390
162	Asynchronously call fdatasync on the given filehandle and call the	391	Asynchronously call fdatasync on the given filehandle and call the
163	callback with the fdatasync result code.	392	callback with the fdatasync result code.
164		393
		394	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.
		396
165	=back	397	=back
166		398
167	=head2 SUPPORT FUNCTIONS	399	=head2 SUPPORT FUNCTIONS
168		400
169	=over 4	401	=over 4
170		402
171	=item $fileno = IO::AIO::poll_fileno	403	=item $fileno = IO::AIO::poll_fileno
172		404
173	Return the I<request result pipe filehandle>. This filehandle must be	405	Return the I<request result pipe file descriptor>. This filehandle must be
174	polled for reading by some mechanism outside this module (e.g. Event	406	polled for reading by some mechanism outside this module (e.g. Event or
175	or select, see below). If the pipe becomes readable you have to call	407	select, see below or the SYNOPSIS). If the pipe becomes readable you have
176	C<poll_cb> to check the results.	408	to call C<poll_cb> to check the results.
177		409
178	See C<poll_cb> for an example.	410	See C<poll_cb> for an example.
179		411
180	=item IO::AIO::poll_cb	412	=item IO::AIO::poll_cb
181		413
182	Process all outstanding events on the result pipe. You have to call this	414	Process all outstanding events on the result pipe. You have to call this
183	regularly. Returns the number of events processed. Returns immediately	415	regularly. Returns the number of events processed. Returns immediately
184	when no events are outstanding.	416	when no events are outstanding.
185		417
186	You can use Event to multiplex, e.g.:	418	Example: Install an Event watcher that automatically calls
		419	IO::AIO::poll_cb with high priority:
187		420
188	Event->io (fd => IO::AIO::poll_fileno,	421	Event->io (fd => IO::AIO::poll_fileno,
189	poll => 'r', async => 1,	422	poll => 'r', async => 1,
190	cb => \&IO::AIO::poll_cb);	423	cb => \&IO::AIO::poll_cb);
191		424
192	=item IO::AIO::poll_wait	425	=item IO::AIO::poll_wait
193		426
194	Wait till the result filehandle becomes ready for reading (simply does a	427	Wait till the result filehandle becomes ready for reading (simply does a
195	select on the filehandle. This is useful if you want to synchronously wait	428	C<select> on the filehandle. This is useful if you want to synchronously wait
196	for some requests to finish).	429	for some requests to finish).
197		430
198	See C<nreqs> for an example.	431	See C<nreqs> for an example.
199		432
200	=item IO::AIO::nreqs	433	=item IO::AIO::nreqs
201		434
202	Returns the number of requests currently outstanding.	435	Returns the number of requests currently outstanding (i.e. for which their
		436	callback has not been invoked yet).
203		437
204	Example: wait till there are no outstanding requests anymore:	438	Example: wait till there are no outstanding requests anymore:
205		439
206	IO::AIO::poll_wait, IO::AIO::poll_cb	440	IO::AIO::poll_wait, IO::AIO::poll_cb
207	while IO::AIO::nreqs;	441	while IO::AIO::nreqs;
208		442
		443	=item IO::AIO::flush
		444
		445	Wait till all outstanding AIO requests have been handled.
		446
		447	Strictly equivalent to:
		448
		449	IO::AIO::poll_wait, IO::AIO::poll_cb
		450	while IO::AIO::nreqs;
		451
		452	=item IO::AIO::poll
		453
		454	Waits until some requests have been handled.
		455
		456	Strictly equivalent to:
		457
		458	IO::AIO::poll_wait, IO::AIO::poll_cb
		459	if IO::AIO::nreqs;
		460
209	=item IO::AIO::min_parallel $nthreads	461	=item IO::AIO::min_parallel $nthreads
210		462
211	Set the minimum number of AIO threads to C<$nthreads>. The default is	463	Set the minimum number of AIO threads to C<$nthreads>. The current default
212	C<1>, which means a single asynchronous operation can be done at one time	464	is C<4>, which means four asynchronous operations can be done at one time
213	(the number of outstanding operations, however, is unlimited).	465	(the number of outstanding operations, however, is unlimited).
		466
		467	IO::AIO starts threads only on demand, when an AIO request is queued and
		468	no free thread exists.
214		469
215	It is recommended to keep the number of threads low, as some Linux	470	It is recommended to keep the number of threads low, as some Linux
216	kernel versions will scale negatively with the number of threads (higher	471	kernel versions will scale negatively with the number of threads (higher
217	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	472	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
218	threads should be fine.	473	threads should be fine.
219		474
220	Under normal circumstances you don't need to call this function, as this	475	Under most circumstances you don't need to call this function, as the
221	module automatically starts some threads (the exact number might change,	476	module selects a default that is suitable for low to moderate load.
222	and is currently 4).
223		477
224	=item IO::AIO::max_parallel $nthreads	478	=item IO::AIO::max_parallel $nthreads
225		479
226	Sets the maximum number of AIO threads to C<$nthreads>. If more than	480	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
227	the specified number of threads are currently running, kill them. This	481	specified number of threads are currently running, this function kills
228	function blocks until the limit is reached.	482	them. This function blocks until the limit is reached.
		483
		484	While C<$nthreads> are zero, aio requests get queued but not executed
		485	until the number of threads has been increased again.
229		486
230	This module automatically runs C<max_parallel 0> at program end, to ensure	487	This module automatically runs C<max_parallel 0> at program end, to ensure
231	that all threads are killed and that there are no outstanding requests.	488	that all threads are killed and that there are no outstanding requests.
232		489
233	Under normal circumstances you don't need to call this function.	490	Under normal circumstances you don't need to call this function.
…		…
237	Sets the maximum number of outstanding requests to C<$nreqs>. If you	494	Sets the maximum number of outstanding requests to C<$nreqs>. If you
238	try to queue up more than this number of requests, the caller will block until	495	try to queue up more than this number of requests, the caller will block until
239	some requests have been handled.	496	some requests have been handled.
240		497
241	The default is very large, so normally there is no practical limit. If you	498	The default is very large, so normally there is no practical limit. If you
242	queue up many requests in a loop it it often improves speed if you set	499	queue up many requests in a loop it often improves speed if you set
243	this to a relatively low number, such as C<100>.	500	this to a relatively low number, such as C<100>.
244		501
245	Under normal circumstances you don't need to call this function.	502	Under normal circumstances you don't need to call this function.
246		503
247	=back	504	=back
…		…
250		507
251	# support function to convert a fd into a perl filehandle	508	# support function to convert a fd into a perl filehandle
252	sub _fd2fh {	509	sub _fd2fh {
253	return undef if $_[0] < 0;	510	return undef if $_[0] < 0;
254		511
255	# try to be perl5.6-compatible	512	# try to generate nice filehandles
256	local *AIO_FH;	513	my $sym = "IO::AIO::fd#$_[0]";
257	open AIO_FH, "+<&=$_[0]"	514	local *$sym;
		515
		516	open *$sym, "+<&=$_[0]" # usually works under any unix
		517	or open *$sym, "<&=$_[0]" # cygwin needs this
		518	or open *$sym, ">&=$_[0]" # or this
258	or return undef;	519	or return undef;
259		520
260	*AIO_FH	521	*$sym
261	}	522	}
262		523
263	min_parallel 4;	524	min_parallel 4;
264		525
265	END {	526	END {
266	max_parallel 0;	527	max_parallel 0;
267	}	528	}
268		529
269	1;	530	1;
270		531
		532	=head2 FORK BEHAVIOUR
		533
		534	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
		536	the fork the parent simply leaves the quiescent state and continues
		537	request/result processing, while the child clears the request/result
		538	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
		540	parent process has been reached again.
		541
271	=head1 SEE ALSO	542	=head1 SEE ALSO
272		543
273	L<Coro>, L<Linux::AIO>.	544	L<Coro>, L<Linux::AIO>.
274		545
275	=head1 AUTHOR	546	=head1 AUTHOR

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Revision 1.40 by root, Tue Aug 30 15:45:10 2005 UTC