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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.1 by root, Sun Jul 10 17:07:44 2005 UTC vs.
Revision 1.51 by root, Sat Jun 24 19:14:04 2006 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		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	# AnyEvent
		21	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		22	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		23
		24	# Event
		25	Event->io (fd => IO::AIO::poll_fileno,
		26	poll => 'r',
		27	cb => \&IO::AIO::poll_cb);
		28
		29	# Glib/Gtk2
		30	add_watch Glib::IO IO::AIO::poll_fileno,
		31	in => sub { IO::AIO::poll_cb; 1 };
		32
		33	# Tk
		34	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		35	readable => \&IO::AIO::poll_cb);
		36
		37	# Danga::Socket
		38	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		39	\&IO::AIO::poll_cb);
		40
		41
9	=head1 DESCRIPTION	42	=head1 DESCRIPTION
10		43
11	This module implements asynchronous I/O using whatever means your	44	This module implements asynchronous I/O using whatever means your
12	operating system supports. Currently, it falls back to Linux::AIO if that	45	operating system supports.
13	module is available, or uses pthreads to emulato aio functionality.
14		46
15	Currently, in this module a number of threads are started that execute	47	Currently, a number of threads are started that execute your read/writes
16	your read/writes and signal their completion. You don't need thread	48	and signal their completion. You don't need thread support in your libc or
17	support in your libc or perl, and the threads created by this module will	49	perl, and the threads created by this module will not be visible to the
18	not be visible to the pthreads library.	50	pthreads library. In the future, this module might make use of the native
		51	aio functions available on many operating systems. However, they are often
		52	not well-supported (Linux doesn't allow them on normal files currently,
		53	for example), and they would only support aio_read and aio_write, so the
		54	remaining functionality would have to be implemented using threads anyway.
19		55
20	Although the module will work with in the presence of other threads, it is	56	Although the module will work with in the presence of other threads, it is
21	not reentrant, so use appropriate locking yourself.	57	currently not reentrant, so use appropriate locking yourself, always call
		58	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other
		59	C<aio_> functions) recursively.
22		60
23	=head2 API NOTES	61	=cut
		62
		63	package IO::AIO;
		64
		65	no warnings;
		66	use strict 'vars';
		67
		68	use base 'Exporter';
		69
		70	BEGIN {
		71	our $VERSION = '1.8';
		72
		73	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
		74	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
		75	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move);
		76	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
		77
		78	require XSLoader;
		79	XSLoader::load ("IO::AIO", $VERSION);
		80	}
		81
		82	=head1 FUNCTIONS
		83
		84	=head2 AIO FUNCTIONS
24		85
25	All the C<aio_*> calls are more or less thin wrappers around the syscall	86	All the C<aio_*> calls are more or less thin wrappers around the syscall
26	with the same name (sans C<aio_>). The arguments are similar or identical,	87	with the same name (sans C<aio_>). The arguments are similar or identical,
27	and they all accept an additional C<$callback> argument which must be	88	and they all accept an additional (and optional) C<$callback> argument
28	a code reference. This code reference will get called with the syscall	89	which must be a code reference. This code reference will get called with
29	return code (e.g. most syscalls return C<-1> on error, unlike perl, which	90	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
30	usually delivers "false") as it's sole argument when the given syscall has	91	perl, which usually delivers "false") as it's sole argument when the given
31	been executed asynchronously.	92	syscall has been executed asynchronously.
32		93
33	All functions that expect a filehandle will also accept a file descriptor.	94	All functions expecting a filehandle keep a copy of the filehandle
		95	internally until the request has finished.
34		96
35	The filenames you pass to these routines I<must> be absolute. The reason	97	The pathnames you pass to these routines I<must> be absolute and
36	is that at the time the request is being executed, the current working	98	encoded in byte form. The reason for the former is that at the time the
37	directory could have changed. Alternatively, you can make sure that you	99	request is being executed, the current working directory could have
		100	changed. Alternatively, you can make sure that you never change the
38	never change the current working directory.	101	current working directory.
		102
		103	To encode pathnames to byte form, either make sure you either: a)
		104	always pass in filenames you got from outside (command line, readdir
		105	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		106	your pathnames to the locale (or other) encoding in effect in the user
		107	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		108	use something else.
39		109
40	=over 4	110	=over 4
41		111
42	=cut
43
44	package IO::AIO;
45
46	use base 'Exporter';
47
48	BEGIN {
49	$VERSION = 0.1;
50
51	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink
52	aio_fsync aio_fdatasync aio_readahead);
53	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs);
54
55	require XSLoader;
56	XSLoader::load IO::AIO, $VERSION;
57	}
58
59	=item IO::AIO::min_parallel $nthreads
60
61	Set the minimum number of AIO threads to C<$nthreads>. The default is
62	C<1>, which means a single asynchronous operation can be done at one time
63	(the number of outstanding operations, however, is unlimited).
64
65	It is recommended to keep the number of threads low, as some linux
66	kernel versions will scale negatively with the number of threads (higher
67	parallelity => MUCH higher latency).
68
69	Under normal circumstances you don't need to call this function, as this
70	module automatically starts a single async thread.
71
72	=item IO::AIO::max_parallel $nthreads
73
74	Sets the maximum number of AIO threads to C<$nthreads>. If more than
75	the specified number of threads are currently running, kill them. This
76	function blocks until the limit is reached.
77
78	This module automatically runs C<max_parallel 0> at program end, to ensure
79	that all threads are killed and that there are no outstanding requests.
80
81	Under normal circumstances you don't need to call this function.
82
83	=item $fileno = IO::AIO::poll_fileno
84
85	Return the I<request result pipe filehandle>. This filehandle must be
86	polled for reading by some mechanism outside this module (e.g. Event
87	or select, see below). If the pipe becomes readable you have to call
88	C<poll_cb> to check the results.
89
90	See C<poll_cb> for an example.
91
92	=item IO::AIO::poll_cb
93
94	Process all outstanding events on the result pipe. You have to call this
95	regularly. Returns the number of events processed. Returns immediately
96	when no events are outstanding.
97
98	You can use Event to multiplex, e.g.:
99
100	Event->io (fd => IO::AIO::poll_fileno,
101	poll => 'r', async => 1,
102	cb => \&IO::AIO::poll_cb);
103
104	=item IO::AIO::poll_wait
105
106	Wait till the result filehandle becomes ready for reading (simply does a
107	select on the filehandle. This is useful if you want to synchronously wait
108	for some requests to finish).
109
110	See C<nreqs> for an example.
111
112	=item IO::AIO::nreqs
113
114	Returns the number of requests currently outstanding.
115
116	Example: wait till there are no outstanding requests anymore:
117
118	IO::AIO::poll_wait, IO::AIO::poll_cb
119	while IO::AIO::nreqs;
120
121	=item aio_open $pathname, $flags, $mode, $callback	112	=item aio_open $pathname, $flags, $mode, $callback->($fh)
122		113
123	Asynchronously open or create a file and call the callback with the	114	Asynchronously open or create a file and call the callback with a newly
124	filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this	115	created filehandle for the file.
125	might change in the future).
126		116
127	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	117	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
128	for an explanation.	118	for an explanation.
129		119
130	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	120	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
131	list. They are the same as used in C<sysopen>.	121	list. They are the same as used by C<sysopen>.
		122
		123	Likewise, C<$mode> specifies the mode of the newly created file, if it
		124	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		125	except that it is mandatory (i.e. use C<0> if you don't create new files,
		126	and C<0666> or C<0777> if you do).
132		127
133	Example:	128	Example:
134		129
135	aio_open "/etc/passwd", O_RDONLY, 0, sub {	130	aio_open "/etc/passwd", O_RDONLY, 0, sub {
136	if ($_[0] >= 0) {	131	if ($_[0]) {
137	open my $fh, "<&$_[0]"; # create a copy for perl
138	aio_close $_[0], sub { }; # close the aio handle
139	print "open successful, fh is $fh\n";	132	print "open successful, fh is $_[0]\n";
140	...	133	...
141	} else {	134	} else {
142	die "open failed: $!\n";	135	die "open failed: $!\n";
143	}	136	}
144	};	137	};
145		138
146	=item aio_close $fh, $callback	139	=item aio_close $fh, $callback->($status)
147		140
148	Asynchronously close a file and call the callback with the result code.	141	Asynchronously close a file and call the callback with the result
		142	code. I<WARNING:> although accepted, you should not pass in a perl
		143	filehandle here, as perl will likely close the file descriptor another
		144	time when the filehandle is destroyed. Normally, you can safely call perls
		145	C<close> or just let filehandles go out of scope.
149		146
		147	This is supposed to be a bug in the API, so that might change. It's
		148	therefore best to avoid this function.
		149
150	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	150	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
151		151
152	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	152	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
153		153
154	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	154	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
155	into the scalar given by C<data> and offset C<dataoffset> and calls the	155	into the scalar given by C<data> and offset C<dataoffset> and calls the
156	callback without the actual number of bytes read (or -1 on error, just	156	callback without the actual number of bytes read (or -1 on error, just
157	like the syscall).	157	like the syscall).
158		158
		159	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		160	is outstanding. Modifying it can result in segfaults or WW3 (if the
		161	necessary/optional hardware is installed).
		162
159	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	163	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
160	offset C<0> within the scalar:	164	offset C<0> within the scalar:
161		165
162	aio_read $fh, 7, 15, $buffer, 0, sub {	166	aio_read $fh, 7, 15, $buffer, 0, sub {
163	$_[0] >= 0 or die "read error: $!";	167	$_[0] > 0 or die "read error: $!";
164	print "read <$buffer>\n";	168	print "read $_[0] bytes: <$buffer>\n";
165	};	169	};
166		170
		171	=item aio_move $srcpath, $dstpath, $callback->($status)
		172
		173	[EXPERIMENTAL]
		174
		175	Try to move the I<file> (directories not supported as either source or destination)
		176	from C<$srcpath> to C<$dstpath> and call the callback with the C<0> (error) or C<-1> ok.
		177
		178	This is a composite request that tries to rename(2) the file first. If
		179	rename files with C<EXDEV>, it creates the destination file with mode 0200
		180	and copies the contents of the source file into it using C<aio_sendfile>,
		181	followed by restoring atime, mtime, access mode and uid/gid, in that
		182	order, and unlinking the C<$srcpath>.
		183
		184	If an error occurs, the partial destination file will be unlinked, if
		185	possible, except when setting atime, mtime, access mode and uid/gid, where
		186	errors are being ignored.
		187
		188	=cut
		189
		190	sub aio_move($$$) {
		191	my ($src, $dst, $cb) = @_;
		192
		193	aio_rename $src, $dst, sub {
		194	if ($_[0] && $! == EXDEV) {
		195	aio_open $src, O_RDONLY, 0, sub {
		196	if (my $src_fh = $_[0]) {
		197	my @stat = stat $src_fh;
		198
		199	aio_open $dst, O_WRONLY, 0200, sub {
		200	if (my $dst_fh = $_[0]) {
		201	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		202	close $src_fh;
		203
		204	if ($_[0] == $stat[7]) {
		205	utime $stat[8], $stat[9], $dst;
		206	chmod $stat[2] & 07777, $dst_fh;
		207	chown $stat[4], $stat[5], $dst_fh;
		208	close $dst_fh;
		209
		210	aio_unlink $src, sub {
		211	$cb->($_[0]);
		212	};
		213	} else {
		214	my $errno = $!;
		215	aio_unlink $dst, sub {
		216	$! = $errno;
		217	$cb->(-1);
		218	};
		219	}
		220	};
		221	} else {
		222	$cb->(-1);
		223	}
		224	},
		225
		226	} else {
		227	$cb->(-1);
		228	}
		229	};
		230	} else {
		231	$cb->($_[0]);
		232	}
		233	};
		234	}
		235
		236	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		237
		238	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		239	reading at byte offset C<$in_offset>, and starts writing at the current
		240	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		241	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		242	other.
		243
		244	This call tries to make use of a native C<sendfile> syscall to provide
		245	zero-copy operation. For this to work, C<$out_fh> should refer to a
		246	socket, and C<$in_fh> should refer to mmap'able file.
		247
		248	If the native sendfile call fails or is not implemented, it will be
		249	emulated, so you can call C<aio_sendfile> on any type of filehandle
		250	regardless of the limitations of the operating system.
		251
		252	Please note, however, that C<aio_sendfile> can read more bytes from
		253	C<$in_fh> than are written, and there is no way to find out how many
		254	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		255	provides the number of bytes written to C<$out_fh>. Only if the result
		256	value equals C<$length> one can assume that C<$length> bytes have been
		257	read.
		258
167	=item aio_readahead $fh,$offset,$length, $callback	259	=item aio_readahead $fh,$offset,$length, $callback->($retval)
168		260
169	Asynchronously reads the specified byte range into the page cache, using
170	the C<readahead> syscall. If that syscall doesn't exist the status will be
171	C<-1> and C<$!> is set to ENOSYS.
172
173	readahead() populates the page cache with data from a file so that	261	C<aio_readahead> populates the page cache with data from a file so that
174	subsequent reads from that file will not block on disk I/O. The C<$offset>	262	subsequent reads from that file will not block on disk I/O. The C<$offset>
175	argument specifies the starting point from which data is to be read and	263	argument specifies the starting point from which data is to be read and
176	C<$length> specifies the number of bytes to be read. I/O is performed in	264	C<$length> specifies the number of bytes to be read. I/O is performed in
177	whole pages, so that offset is effectively rounded down to a page boundary	265	whole pages, so that offset is effectively rounded down to a page boundary
178	and bytes are read up to the next page boundary greater than or equal to	266	and bytes are read up to the next page boundary greater than or equal to
179	(off-set+length). aio_readahead() does not read beyond the end of the	267	(off-set+length). C<aio_readahead> does not read beyond the end of the
180	file. The current file offset of the file is left unchanged.	268	file. The current file offset of the file is left unchanged.
181		269
		270	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		271	emulated by simply reading the data, which would have a similar effect.
		272
182	=item aio_stat $fh_or_path, $callback	273	=item aio_stat $fh_or_path, $callback->($status)
183		274
184	=item aio_lstat $fh, $callback	275	=item aio_lstat $fh, $callback->($status)
185		276
186	Works like perl's C<stat> or C<lstat> in void context. The callback will	277	Works like perl's C<stat> or C<lstat> in void context. The callback will
187	be called after the stat and the results will be available using C<stat _>	278	be called after the stat and the results will be available using C<stat _>
188	or C<-s _> etc...	279	or C<-s _> etc...
189		280
…		…
199	aio_stat "/etc/passwd", sub {	290	aio_stat "/etc/passwd", sub {
200	$_[0] and die "stat failed: $!";	291	$_[0] and die "stat failed: $!";
201	print "size is ", -s _, "\n";	292	print "size is ", -s _, "\n";
202	};	293	};
203		294
204	=item aio_unlink $pathname, $callback	295	=item aio_unlink $pathname, $callback->($status)
205		296
206	Asynchronously unlink (delete) a file and call the callback with the	297	Asynchronously unlink (delete) a file and call the callback with the
207	result code.	298	result code.
208		299
		300	=item aio_link $srcpath, $dstpath, $callback->($status)
		301
		302	Asynchronously create a new link to the existing object at C<$srcpath> at
		303	the path C<$dstpath> and call the callback with the result code.
		304
		305	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		306
		307	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		308	the path C<$dstpath> and call the callback with the result code.
		309
		310	=item aio_rename $srcpath, $dstpath, $callback->($status)
		311
		312	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		313	rename(2) and call the callback with the result code.
		314
		315	=item aio_rmdir $pathname, $callback->($status)
		316
		317	Asynchronously rmdir (delete) a directory and call the callback with the
		318	result code.
		319
		320	=item aio_readdir $pathname, $callback->($entries)
		321
		322	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		323	directory (i.e. opendir + readdir + closedir). The entries will not be
		324	sorted, and will B<NOT> include the C<.> and C<..> entries.
		325
		326	The callback a single argument which is either C<undef> or an array-ref
		327	with the filenames.
		328
		329	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		330
		331	Scans a directory (similar to C<aio_readdir>) and tries to separate the
		332	entries of directory C<$path> into two sets of names, ones you can recurse
		333	into (directories), and ones you cannot recurse into (everything else).
		334
		335	C<aio_scandir> is a composite request that consists of many
		336	aio-primitives. C<$maxreq> specifies the maximum number of outstanding
		337	aio requests that this function generates. If it is C<< <= 0 >>, then a
		338	suitable default will be chosen (currently 8).
		339
		340	On error, the callback is called without arguments, otherwise it receives
		341	two array-refs with path-relative entry names.
		342
		343	Example:
		344
		345	aio_scandir $dir, 0, sub {
		346	my ($dirs, $nondirs) = @_;
		347	print "real directories: @$dirs\n";
		348	print "everything else: @$nondirs\n";
		349	};
		350
		351	Implementation notes.
		352
		353	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		354
		355	After reading the directory, the modification time, size etc. of the
		356	directory before and after the readdir is checked, and if they match, the
		357	link count will be used to decide how many entries are directories (if
		358	>= 2). Otherwise, no knowledge of the number of subdirectories will be
		359	assumed.
		360
		361	Then entires will be sorted into likely directories (everything without a
		362	non-initial dot) and likely non-directories (everything else). Then every
		363	entry + C</.> will be C<stat>'ed, likely directories first. This is often
		364	faster because filesystems might detect the type of the entry without
		365	reading the inode data (e.g. ext2fs filetype feature). If that succeeds,
		366	it assumes that the entry is a directory or a symlink to directory (which
		367	will be checked seperately).
		368
		369	If the known number of directories has been reached, the rest of the
		370	entries is assumed to be non-directories.
		371
		372	=cut
		373
		374	sub aio_scandir($$$) {
		375	my ($path, $maxreq, $cb) = @_;
		376
		377	$maxreq = 8 if $maxreq <= 0;
		378
		379	# stat once
		380	aio_stat $path, sub {
		381	return $cb->() if $_[0];
		382	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		383
		384	# read the directory entries
		385	aio_readdir $path, sub {
		386	my $entries = shift
		387	or return $cb->();
		388
		389	# stat the dir another time
		390	aio_stat $path, sub {
		391	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		392
		393	my $ndirs;
		394
		395	# take the slow route if anything looks fishy
		396	if ($hash1 ne $hash2) {
		397	$ndirs = -1;
		398	} else {
		399	# if nlink == 2, we are finished
		400	# on non-posix-fs's, we rely on nlink < 2
		401	$ndirs = (stat _)[3] - 2
		402	or return $cb->([], $entries);
		403	}
		404
		405	# sort into likely dirs and likely nondirs
		406	# dirs == files without ".", short entries first
		407	$entries = [map $_->[0],
		408	sort { $b->[1] cmp $a->[1] }
		409	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		410	@$entries];
		411
		412	my (@dirs, @nondirs);
		413
		414	my ($statcb, $schedcb);
		415	my $nreq = 0;
		416
		417	$schedcb = sub {
		418	if (@$entries) {
		419	if ($nreq < $maxreq) {
		420	my $ent = pop @$entries;
		421	$nreq++;
		422	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		423	}
		424	} elsif (!$nreq) {
		425	# finished
		426	undef $statcb;
		427	undef $schedcb;
		428	$cb->(\@dirs, \@nondirs) if $cb;
		429	undef $cb;
		430	}
		431	};
		432	$statcb = sub {
		433	my ($status, $entry) = @_;
		434
		435	if ($status < 0) {
		436	$nreq--;
		437	push @nondirs, $entry;
		438	&$schedcb;
		439	} else {
		440	# need to check for real directory
		441	aio_lstat "$path/$entry", sub {
		442	$nreq--;
		443
		444	if (-d _) {
		445	push @dirs, $entry;
		446
		447	if (!--$ndirs) {
		448	push @nondirs, @$entries;
		449	$entries = [];
		450	}
		451	} else {
		452	push @nondirs, $entry;
		453	}
		454
		455	&$schedcb;
		456	}
		457	}
		458	};
		459
		460	&$schedcb while @$entries && $nreq < $maxreq;
		461	};
		462	};
		463	};
		464	}
		465
209	=item aio_fsync $fh, $callback	466	=item aio_fsync $fh, $callback->($status)
210		467
211	Asynchronously call fsync on the given filehandle and call the callback	468	Asynchronously call fsync on the given filehandle and call the callback
212	with the fsync result code.	469	with the fsync result code.
213		470
214	=item aio_fdatasync $fh, $callback	471	=item aio_fdatasync $fh, $callback->($status)
215		472
216	Asynchronously call fdatasync on the given filehandle and call the	473	Asynchronously call fdatasync on the given filehandle and call the
217	callback with the fdatasync result code.	474	callback with the fdatasync result code.
218		475
		476	If this call isn't available because your OS lacks it or it couldn't be
		477	detected, it will be emulated by calling C<fsync> instead.
		478
		479	=back
		480
		481	=head2 SUPPORT FUNCTIONS
		482
		483	=over 4
		484
		485	=item $fileno = IO::AIO::poll_fileno
		486
		487	Return the I<request result pipe file descriptor>. This filehandle must be
		488	polled for reading by some mechanism outside this module (e.g. Event or
		489	select, see below or the SYNOPSIS). If the pipe becomes readable you have
		490	to call C<poll_cb> to check the results.
		491
		492	See C<poll_cb> for an example.
		493
		494	=item IO::AIO::poll_cb
		495
		496	Process all outstanding events on the result pipe. You have to call this
		497	regularly. Returns the number of events processed. Returns immediately
		498	when no events are outstanding.
		499
		500	Example: Install an Event watcher that automatically calls
		501	IO::AIO::poll_cb with high priority:
		502
		503	Event->io (fd => IO::AIO::poll_fileno,
		504	poll => 'r', async => 1,
		505	cb => \&IO::AIO::poll_cb);
		506
		507	=item IO::AIO::poll_wait
		508
		509	Wait till the result filehandle becomes ready for reading (simply does a
		510	C<select> on the filehandle. This is useful if you want to synchronously wait
		511	for some requests to finish).
		512
		513	See C<nreqs> for an example.
		514
		515	=item IO::AIO::nreqs
		516
		517	Returns the number of requests currently outstanding (i.e. for which their
		518	callback has not been invoked yet).
		519
		520	Example: wait till there are no outstanding requests anymore:
		521
		522	IO::AIO::poll_wait, IO::AIO::poll_cb
		523	while IO::AIO::nreqs;
		524
		525	=item IO::AIO::flush
		526
		527	Wait till all outstanding AIO requests have been handled.
		528
		529	Strictly equivalent to:
		530
		531	IO::AIO::poll_wait, IO::AIO::poll_cb
		532	while IO::AIO::nreqs;
		533
		534	=item IO::AIO::poll
		535
		536	Waits until some requests have been handled.
		537
		538	Strictly equivalent to:
		539
		540	IO::AIO::poll_wait, IO::AIO::poll_cb
		541	if IO::AIO::nreqs;
		542
		543	=item IO::AIO::min_parallel $nthreads
		544
		545	Set the minimum number of AIO threads to C<$nthreads>. The current default
		546	is C<4>, which means four asynchronous operations can be done at one time
		547	(the number of outstanding operations, however, is unlimited).
		548
		549	IO::AIO starts threads only on demand, when an AIO request is queued and
		550	no free thread exists.
		551
		552	It is recommended to keep the number of threads low, as some Linux
		553	kernel versions will scale negatively with the number of threads (higher
		554	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
		555	threads should be fine.
		556
		557	Under most circumstances you don't need to call this function, as the
		558	module selects a default that is suitable for low to moderate load.
		559
		560	=item IO::AIO::max_parallel $nthreads
		561
		562	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		563	specified number of threads are currently running, this function kills
		564	them. This function blocks until the limit is reached.
		565
		566	While C<$nthreads> are zero, aio requests get queued but not executed
		567	until the number of threads has been increased again.
		568
		569	This module automatically runs C<max_parallel 0> at program end, to ensure
		570	that all threads are killed and that there are no outstanding requests.
		571
		572	Under normal circumstances you don't need to call this function.
		573
		574	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		575
		576	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		577	try to queue up more than this number of requests, the caller will block until
		578	some requests have been handled.
		579
		580	The default is very large, so normally there is no practical limit. If you
		581	queue up many requests in a loop it often improves speed if you set
		582	this to a relatively low number, such as C<100>.
		583
		584	Under normal circumstances you don't need to call this function.
		585
		586	=back
		587
219	=cut	588	=cut
		589
		590	# support function to convert a fd into a perl filehandle
		591	sub _fd2fh {
		592	return undef if $_[0] < 0;
		593
		594	# try to generate nice filehandles
		595	my $sym = "IO::AIO::fd#$_[0]";
		596	local *$sym;
		597
		598	open *$sym, "+<&=$_[0]" # usually works under any unix
		599	or open *$sym, "<&=$_[0]" # cygwin needs this
		600	or open *$sym, ">&=$_[0]" # or this
		601	or return undef;
		602
		603	*$sym
		604	}
220		605
221	min_parallel 4;	606	min_parallel 4;
222		607
223	END {	608	END {
224	max_parallel 0;	609	max_parallel 0;
225	}	610	}
226		611
227	1;	612	1;
228		613
229	=back	614	=head2 FORK BEHAVIOUR
230		615
231	=head1 BUGS	616	Before the fork, IO::AIO enters a quiescent state where no requests
232		617	can be added in other threads and no results will be processed. After
233	- aio_open gives a fd, but all other functions expect a perl filehandle.	618	the fork the parent simply leaves the quiescent state and continues
		619	request/result processing, while the child clears the request/result
		620	queue (so the requests started before the fork will only be handled in
		621	the parent). Threats will be started on demand until the limit ste in the
		622	parent process has been reached again.
234		623
235	=head1 SEE ALSO	624	=head1 SEE ALSO
236		625
237	L<Coro>, L<Linux::AIO>.	626	L<Coro>, L<Linux::AIO>.
238		627

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Revision 1.1 by root, Sun Jul 10 17:07:44 2005 UTC vs.
Revision 1.51 by root, Sat Jun 24 19:14:04 2006 UTC