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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.39 by root, Sun Aug 28 11:05:50 2005 UTC vs.
Revision 1.81 by root, Fri Oct 27 19:17:23 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	# Event	20	# version 2+ has request and group objects
		21	use IO::AIO 2;
		22
		23	aioreq_pri 4; # give next request a very high priority
		24	my $req = aio_unlink "/tmp/file", sub { };
		25	$req->cancel; # cancel request if still in queue
		26
		27	my $grp = aio_group sub { print "all stats done\n" };
		28	add $grp aio_stat "..." for ...;
		29
		30	# AnyEvent integration
		31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		33
		34	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	35	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	36	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	37	cb => \&IO::AIO::poll_cb);
24		38
25	# Glib/Gtk2	39	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	40	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb; 1 };	41	in => sub { IO::AIO::poll_cb; 1 };
28		42
29	# Tk	43	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	45	readable => \&IO::AIO::poll_cb);
32		46
33	# Danga::Socket	47	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	49	\&IO::AIO::poll_cb);
36		50
37
38	=head1 DESCRIPTION	51	=head1 DESCRIPTION
39		52
40	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
41	operating system supports.	54	operating system supports.
42		55
43	Currently, a number of threads are started that execute your read/writes	56	In this version, a number of threads are started that execute your
44	and signal their completion. You don't need thread support in your libc or	57	requests and signal their completion. You don't need thread support
45	perl, and the threads created by this module will not be visible to the	58	in perl, and the threads created by this module will not be visible
46	pthreads library. In the future, this module might make use of the native	59	to perl. In the future, this module might make use of the native aio
47	aio functions available on many operating systems. However, they are often	60	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	61	not well-supported or restricted (Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	62	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	63	aio_write, so the remaining functionality would have to be implemented
		64	using threads anyway.
51		65
52	Although the module will work with in the presence of other threads, it is	66	Although the module will work with in the presence of other (Perl-)
53	currently not reentrant, so use appropriate locking yourself, always call	67	threads, it is currently not reentrant in any way, so use appropriate
54	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	68	locking yourself, always call C<poll_cb> from within the same thread, or
55	C<aio_> functions) recursively.	69	never call C<poll_cb> (or other C<aio_> functions) recursively.
		70
		71	=head1 REQUEST ANATOMY AND LIFETIME
		72
		73	Every C<aio_*> function creates a request. which is a C data structure not
		74	directly visible to Perl.
		75
		76	If called in non-void context, every request function returns a Perl
		77	object representing the request. In void context, nothing is returned,
		78	which saves a bit of memory.
		79
		80	The perl object is a fairly standard ref-to-hash object. The hash contents
		81	are not used by IO::AIO so you are free to store anything you like in it.
		82
		83	During their existance, aio requests travel through the following states,
		84	in order:
		85
		86	=over 4
		87
		88	=item ready
		89
		90	Immediately after a request is created it is put into the ready state,
		91	waiting for a thread to execute it.
		92
		93	=item execute
		94
		95	A thread has accepted the request for processing and is currently
		96	executing it (e.g. blocking in read).
		97
		98	=item pending
		99
		100	The request has been executed and is waiting for result processing.
		101
		102	While request submission and execution is fully asynchronous, result
		103	processing is not and relies on the perl interpreter calling C<poll_cb>
		104	(or another function with the same effect).
		105
		106	=item result
		107
		108	The request results are processed synchronously by C<poll_cb>.
		109
		110	The C<poll_cb> function will process all outstanding aio requests by
		111	calling their callbacks, freeing memory associated with them and managing
		112	any groups they are contained in.
		113
		114	=item done
		115
		116	Request has reached the end of its lifetime and holds no resources anymore
		117	(except possibly for the Perl object, but its connection to the actual
		118	aio request is severed and calling its methods will either do nothing or
		119	result in a runtime error).
56		120
57	=cut	121	=cut
58		122
59	package IO::AIO;	123	package IO::AIO;
60		124
61	no warnings;	125	no warnings;
		126	use strict 'vars';
62		127
63	use base 'Exporter';	128	use base 'Exporter';
64		129
65	use Fcntl ();
66
67	BEGIN {	130	BEGIN {
68	$VERSION = 1.6;	131	our $VERSION = '2.0';
69		132
70	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	133	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71	aio_lstat aio_unlink aio_rmdir aio_readdir aio_symlink	134	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72	aio_fsync aio_fdatasync aio_readahead);	135	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
73	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	136	aio_group aio_nop);
74	max_outstanding nreqs);	137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		139	min_parallel max_parallel nreqs nready npending);
		140
		141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
75		142
76	require XSLoader;	143	require XSLoader;
77	XSLoader::load IO::AIO, $VERSION;	144	XSLoader::load ("IO::AIO", $VERSION);
78	}	145	}
79		146
80	=head1 FUNCTIONS	147	=head1 FUNCTIONS
81		148
82	=head2 AIO FUNCTIONS	149	=head2 AIO FUNCTIONS
…		…
90	syscall has been executed asynchronously.	157	syscall has been executed asynchronously.
91		158
92	All functions expecting a filehandle keep a copy of the filehandle	159	All functions expecting a filehandle keep a copy of the filehandle
93	internally until the request has finished.	160	internally until the request has finished.
94		161
		162	All requests return objects of type L<IO::AIO::REQ> that allow further
		163	manipulation of those requests while they are in-flight.
		164
95	The pathnames you pass to these routines I<must> be absolute and	165	The pathnames you pass to these routines I<must> be absolute and
96	encoded in byte form. The reason for the former is that at the time the	166	encoded in byte form. The reason for the former is that at the time the
97	request is being executed, the current working directory could have	167	request is being executed, the current working directory could have
98	changed. Alternatively, you can make sure that you never change the	168	changed. Alternatively, you can make sure that you never change the
99	current working directory.	169	current working directory.
…		…
105	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	175	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
106	use something else.	176	use something else.
107		177
108	=over 4	178	=over 4
109		179
		180	=item $prev_pri = aioreq_pri [$pri]
		181
		182	Returns the priority value that would be used for the next request and, if
		183	C<$pri> is given, sets the priority for the next aio request.
		184
		185	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		186	and C<4>, respectively. Requests with higher priority will be serviced
		187	first.
		188
		189	The priority will be reset to C<0> after each call to one of the C<aio_*>
		190	functions.
		191
		192	Example: open a file with low priority, then read something from it with
		193	higher priority so the read request is serviced before other low priority
		194	open requests (potentially spamming the cache):
		195
		196	aioreq_pri -3;
		197	aio_open ..., sub {
		198	return unless $_[0];
		199
		200	aioreq_pri -2;
		201	aio_read $_[0], ..., sub {
		202	...
		203	};
		204	};
		205
		206	=item aioreq_nice $pri_adjust
		207
		208	Similar to C<aioreq_pri>, but subtracts the given value from the current
		209	priority, so effects are cumulative.
		210
110	=item aio_open $pathname, $flags, $mode, $callback	211	=item aio_open $pathname, $flags, $mode, $callback->($fh)
111		212
112	Asynchronously open or create a file and call the callback with a newly	213	Asynchronously open or create a file and call the callback with a newly
113	created filehandle for the file.	214	created filehandle for the file.
114		215
115	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	216	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
132	} else {	233	} else {
133	die "open failed: $!\n";	234	die "open failed: $!\n";
134	}	235	}
135	};	236	};
136		237
137	=item aio_close $fh, $callback	238	=item aio_close $fh, $callback->($status)
138		239
139	Asynchronously close a file and call the callback with the result	240	Asynchronously close a file and call the callback with the result
140	code. I<WARNING:> although accepted, you should not pass in a perl	241	code. I<WARNING:> although accepted, you should not pass in a perl
141	filehandle here, as perl will likely close the file descriptor another	242	filehandle here, as perl will likely close the file descriptor another
142	time when the filehandle is destroyed. Normally, you can safely call perls	243	time when the filehandle is destroyed. Normally, you can safely call perls
143	C<close> or just let filehandles go out of scope.	244	C<close> or just let filehandles go out of scope.
144		245
145	This is supposed to be a bug in the API, so that might change. It's	246	This is supposed to be a bug in the API, so that might change. It's
146	therefore best to avoid this function.	247	therefore best to avoid this function.
147		248
148	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	249	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149		250
150	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	251	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
151		252
152	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	253	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
153	into the scalar given by C<data> and offset C<dataoffset> and calls the	254	into the scalar given by C<data> and offset C<dataoffset> and calls the
154	callback without the actual number of bytes read (or -1 on error, just	255	callback without the actual number of bytes read (or -1 on error, just
155	like the syscall).	256	like the syscall).
…		…
164	aio_read $fh, 7, 15, $buffer, 0, sub {	265	aio_read $fh, 7, 15, $buffer, 0, sub {
165	$_[0] > 0 or die "read error: $!";	266	$_[0] > 0 or die "read error: $!";
166	print "read $_[0] bytes: <$buffer>\n";	267	print "read $_[0] bytes: <$buffer>\n";
167	};	268	};
168		269
		270	=item aio_move $srcpath, $dstpath, $callback->($status)
		271
		272	Try to move the I<file> (directories not supported as either source or
		273	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		274	the C<0> (error) or C<-1> ok.
		275
		276	This is a composite request that tries to rename(2) the file first. If
		277	rename files with C<EXDEV>, it creates the destination file with mode 0200
		278	and copies the contents of the source file into it using C<aio_sendfile>,
		279	followed by restoring atime, mtime, access mode and uid/gid, in that
		280	order, and unlinking the C<$srcpath>.
		281
		282	If an error occurs, the partial destination file will be unlinked, if
		283	possible, except when setting atime, mtime, access mode and uid/gid, where
		284	errors are being ignored.
		285
		286	=cut
		287
		288	sub aio_move($$$) {
		289	my ($src, $dst, $cb) = @_;
		290
		291	my $pri = aioreq_pri;
		292	my $grp = aio_group $cb;
		293
		294	aioreq_pri $pri;
		295	add $grp aio_rename $src, $dst, sub {
		296	if ($_[0] && $! == EXDEV) {
		297	aioreq_pri $pri;
		298	add $grp aio_open $src, O_RDONLY, 0, sub {
		299	if (my $src_fh = $_[0]) {
		300	my @stat = stat $src_fh;
		301
		302	aioreq_pri $pri;
		303	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		304	if (my $dst_fh = $_[0]) {
		305	aioreq_pri $pri;
		306	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		307	close $src_fh;
		308
		309	if ($_[0] == $stat[7]) {
		310	utime $stat[8], $stat[9], $dst;
		311	chmod $stat[2] & 07777, $dst_fh;
		312	chown $stat[4], $stat[5], $dst_fh;
		313	close $dst_fh;
		314
		315	aioreq_pri $pri;
		316	add $grp aio_unlink $src, sub {
		317	$grp->result ($_[0]);
		318	};
		319	} else {
		320	my $errno = $!;
		321	aioreq_pri $pri;
		322	add $grp aio_unlink $dst, sub {
		323	$! = $errno;
		324	$grp->result (-1);
		325	};
		326	}
		327	};
		328	} else {
		329	$grp->result (-1);
		330	}
		331	},
		332
		333	} else {
		334	$grp->result (-1);
		335	}
		336	};
		337	} else {
		338	$grp->result ($_[0]);
		339	}
		340	};
		341
		342	$grp
		343	}
		344
169	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback	345	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
170		346
171	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	347	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	348	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	349	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	350	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
…		…
187	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	363	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	364	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	365	value equals C<$length> one can assume that C<$length> bytes have been
190	read.	366	read.
191		367
192	=item aio_readahead $fh,$offset,$length, $callback	368	=item aio_readahead $fh,$offset,$length, $callback->($retval)
193		369
194	C<aio_readahead> populates the page cache with data from a file so that	370	C<aio_readahead> populates the page cache with data from a file so that
195	subsequent reads from that file will not block on disk I/O. The C<$offset>	371	subsequent reads from that file will not block on disk I/O. The C<$offset>
196	argument specifies the starting point from which data is to be read and	372	argument specifies the starting point from which data is to be read and
197	C<$length> specifies the number of bytes to be read. I/O is performed in	373	C<$length> specifies the number of bytes to be read. I/O is performed in
…		…
201	file. The current file offset of the file is left unchanged.	377	file. The current file offset of the file is left unchanged.
202		378
203	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	379	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.	380	emulated by simply reading the data, which would have a similar effect.
205		381
206	=item aio_stat $fh_or_path, $callback	382	=item aio_stat $fh_or_path, $callback->($status)
207		383
208	=item aio_lstat $fh, $callback	384	=item aio_lstat $fh, $callback->($status)
209		385
210	Works like perl's C<stat> or C<lstat> in void context. The callback will	386	Works like perl's C<stat> or C<lstat> in void context. The callback will
211	be called after the stat and the results will be available using C<stat _>	387	be called after the stat and the results will be available using C<stat _>
212	or C<-s _> etc...	388	or C<-s _> etc...
213		389
…		…
223	aio_stat "/etc/passwd", sub {	399	aio_stat "/etc/passwd", sub {
224	$_[0] and die "stat failed: $!";	400	$_[0] and die "stat failed: $!";
225	print "size is ", -s _, "\n";	401	print "size is ", -s _, "\n";
226	};	402	};
227		403
228	=item aio_unlink $pathname, $callback	404	=item aio_unlink $pathname, $callback->($status)
229		405
230	Asynchronously unlink (delete) a file and call the callback with the	406	Asynchronously unlink (delete) a file and call the callback with the
231	result code.	407	result code.
232		408
		409	=item aio_link $srcpath, $dstpath, $callback->($status)
		410
		411	Asynchronously create a new link to the existing object at C<$srcpath> at
		412	the path C<$dstpath> and call the callback with the result code.
		413
		414	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		415
		416	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		417	the path C<$dstpath> and call the callback with the result code.
		418
		419	=item aio_rename $srcpath, $dstpath, $callback->($status)
		420
		421	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		422	rename(2) and call the callback with the result code.
		423
233	=item aio_rmdir $pathname, $callback	424	=item aio_rmdir $pathname, $callback->($status)
234		425
235	Asynchronously rmdir (delete) a directory and call the callback with the	426	Asynchronously rmdir (delete) a directory and call the callback with the
236	result code.	427	result code.
237		428
238	=item aio_readdir $pathname $callback	429	=item aio_readdir $pathname, $callback->($entries)
239		430
240	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	431	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	432	directory (i.e. opendir + readdir + closedir). The entries will not be
242	sorted, and will B<NOT> include the C<.> and C<..> entries.	433	sorted, and will B<NOT> include the C<.> and C<..> entries.
243		434
244	The callback a single argument which is either C<undef> or an array-ref	435	The callback a single argument which is either C<undef> or an array-ref
245	with the filenames.	436	with the filenames.
246		437
		438	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		439
		440	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		441	efficiently separate the entries of directory C<$path> into two sets of
		442	names, directories you can recurse into (directories), and ones you cannot
		443	recurse into (everything else, including symlinks to directories).
		444
		445	C<aio_scandir> is a composite request that creates of many sub requests_
		446	C<$maxreq> specifies the maximum number of outstanding aio requests that
		447	this function generates. If it is C<< <= 0 >>, then a suitable default
		448	will be chosen (currently 4).
		449
		450	On error, the callback is called without arguments, otherwise it receives
		451	two array-refs with path-relative entry names.
		452
		453	Example:
		454
		455	aio_scandir $dir, 0, sub {
		456	my ($dirs, $nondirs) = @_;
		457	print "real directories: @$dirs\n";
		458	print "everything else: @$nondirs\n";
		459	};
		460
		461	Implementation notes.
		462
		463	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		464
		465	After reading the directory, the modification time, size etc. of the
		466	directory before and after the readdir is checked, and if they match (and
		467	isn't the current time), the link count will be used to decide how many
		468	entries are directories (if >= 2). Otherwise, no knowledge of the number
		469	of subdirectories will be assumed.
		470
		471	Then entries will be sorted into likely directories (everything without
		472	a non-initial dot currently) and likely non-directories (everything
		473	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		474	likely directories first. If that succeeds, it assumes that the entry
		475	is a directory or a symlink to directory (which will be checked
		476	seperately). This is often faster than stat'ing the entry itself because
		477	filesystems might detect the type of the entry without reading the inode
		478	data (e.g. ext2fs filetype feature).
		479
		480	If the known number of directories (link count - 2) has been reached, the
		481	rest of the entries is assumed to be non-directories.
		482
		483	This only works with certainty on POSIX (= UNIX) filesystems, which
		484	fortunately are the vast majority of filesystems around.
		485
		486	It will also likely work on non-POSIX filesystems with reduced efficiency
		487	as those tend to return 0 or 1 as link counts, which disables the
		488	directory counting heuristic.
		489
		490	=cut
		491
		492	sub aio_scandir($$$) {
		493	my ($path, $maxreq, $cb) = @_;
		494
		495	my $pri = aioreq_pri;
		496
		497	my $grp = aio_group $cb;
		498
		499	$maxreq = 4 if $maxreq <= 0;
		500
		501	# stat once
		502	aioreq_pri $pri;
		503	add $grp aio_stat $path, sub {
		504	return $grp->result () if $_[0];
		505	my $now = time;
		506	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		507
		508	# read the directory entries
		509	aioreq_pri $pri;
		510	add $grp aio_readdir $path, sub {
		511	my $entries = shift
		512	or return $grp->result ();
		513
		514	# stat the dir another time
		515	aioreq_pri $pri;
		516	add $grp aio_stat $path, sub {
		517	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		518
		519	my $ndirs;
		520
		521	# take the slow route if anything looks fishy
		522	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		523	$ndirs = -1;
		524	} else {
		525	# if nlink == 2, we are finished
		526	# on non-posix-fs's, we rely on nlink < 2
		527	$ndirs = (stat _)[3] - 2
		528	or return $grp->result ([], $entries);
		529	}
		530
		531	# sort into likely dirs and likely nondirs
		532	# dirs == files without ".", short entries first
		533	$entries = [map $_->[0],
		534	sort { $b->[1] cmp $a->[1] }
		535	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		536	@$entries];
		537
		538	my (@dirs, @nondirs);
		539
		540	my $statgrp = add $grp aio_group sub {
		541	$grp->result (\@dirs, \@nondirs);
		542	};
		543
		544	limit $statgrp $maxreq;
		545	feed $statgrp sub {
		546	return unless @$entries;
		547	my $entry = pop @$entries;
		548
		549	aioreq_pri $pri;
		550	add $statgrp aio_stat "$path/$entry/.", sub {
		551	if ($_[0] < 0) {
		552	push @nondirs, $entry;
		553	} else {
		554	# need to check for real directory
		555	aioreq_pri $pri;
		556	add $statgrp aio_lstat "$path/$entry", sub {
		557	if (-d _) {
		558	push @dirs, $entry;
		559
		560	unless (--$ndirs) {
		561	push @nondirs, @$entries;
		562	feed $statgrp;
		563	}
		564	} else {
		565	push @nondirs, $entry;
		566	}
		567	}
		568	}
		569	};
		570	};
		571	};
		572	};
		573	};
		574
		575	$grp
		576	}
		577
247	=item aio_fsync $fh, $callback	578	=item aio_fsync $fh, $callback->($status)
248		579
249	Asynchronously call fsync on the given filehandle and call the callback	580	Asynchronously call fsync on the given filehandle and call the callback
250	with the fsync result code.	581	with the fsync result code.
251		582
252	=item aio_fdatasync $fh, $callback	583	=item aio_fdatasync $fh, $callback->($status)
253		584
254	Asynchronously call fdatasync on the given filehandle and call the	585	Asynchronously call fdatasync on the given filehandle and call the
255	callback with the fdatasync result code.	586	callback with the fdatasync result code.
256		587
257	If this call isn't available because your OS lacks it or it couldn't be	588	If this call isn't available because your OS lacks it or it couldn't be
258	detected, it will be emulated by calling C<fsync> instead.	589	detected, it will be emulated by calling C<fsync> instead.
		590
		591	=item aio_group $callback->(...)
		592
		593	This is a very special aio request: Instead of doing something, it is a
		594	container for other aio requests, which is useful if you want to bundle
		595	many requests into a single, composite, request with a definite callback
		596	and the ability to cancel the whole request with its subrequests.
		597
		598	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		599	for more info.
		600
		601	Example:
		602
		603	my $grp = aio_group sub {
		604	print "all stats done\n";
		605	};
		606
		607	add $grp
		608	(aio_stat ...),
		609	(aio_stat ...),
		610	...;
		611
		612	=item aio_nop $callback->()
		613
		614	This is a special request - it does nothing in itself and is only used for
		615	side effects, such as when you want to add a dummy request to a group so
		616	that finishing the requests in the group depends on executing the given
		617	code.
		618
		619	While this request does nothing, it still goes through the execution
		620	phase and still requires a worker thread. Thus, the callback will not
		621	be executed immediately but only after other requests in the queue have
		622	entered their execution phase. This can be used to measure request
		623	latency.
		624
		625	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		626
		627	Mainly used for debugging and benchmarking, this aio request puts one of
		628	the request workers to sleep for the given time.
		629
		630	While it is theoretically handy to have simple I/O scheduling requests
		631	like sleep and file handle readable/writable, the overhead this creates is
		632	immense (it blocks a thread for a long time) so do not use this function
		633	except to put your application under artificial I/O pressure.
		634
		635	=back
		636
		637	=head2 IO::AIO::REQ CLASS
		638
		639	All non-aggregate C<aio_*> functions return an object of this class when
		640	called in non-void context.
		641
		642	=over 4
		643
		644	=item cancel $req
		645
		646	Cancels the request, if possible. Has the effect of skipping execution
		647	when entering the B<execute> state and skipping calling the callback when
		648	entering the the B<result> state, but will leave the request otherwise
		649	untouched. That means that requests that currently execute will not be
		650	stopped and resources held by the request will not be freed prematurely.
		651
		652	=item cb $req $callback->(...)
		653
		654	Replace (or simply set) the callback registered to the request.
		655
		656	=back
		657
		658	=head2 IO::AIO::GRP CLASS
		659
		660	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		661	objects of this class, too.
		662
		663	A IO::AIO::GRP object is a special request that can contain multiple other
		664	aio requests.
		665
		666	You create one by calling the C<aio_group> constructing function with a
		667	callback that will be called when all contained requests have entered the
		668	C<done> state:
		669
		670	my $grp = aio_group sub {
		671	print "all requests are done\n";
		672	};
		673
		674	You add requests by calling the C<add> method with one or more
		675	C<IO::AIO::REQ> objects:
		676
		677	$grp->add (aio_unlink "...");
		678
		679	add $grp aio_stat "...", sub {
		680	$_[0] or return $grp->result ("error");
		681
		682	# add another request dynamically, if first succeeded
		683	add $grp aio_open "...", sub {
		684	$grp->result ("ok");
		685	};
		686	};
		687
		688	This makes it very easy to create composite requests (see the source of
		689	C<aio_move> for an application) that work and feel like simple requests.
		690
		691	=over 4
		692
		693	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		694	C<IO::AIO::poll_cb>, just like any other request.
		695
		696	=item * They can be canceled like any other request. Canceling will cancel not
		697	only the request itself, but also all requests it contains.
		698
		699	=item * They can also can also be added to other IO::AIO::GRP objects.
		700
		701	=item * You must not add requests to a group from within the group callback (or
		702	any later time).
		703
		704	=back
		705
		706	Their lifetime, simplified, looks like this: when they are empty, they
		707	will finish very quickly. If they contain only requests that are in the
		708	C<done> state, they will also finish. Otherwise they will continue to
		709	exist.
		710
		711	That means after creating a group you have some time to add requests. And
		712	in the callbacks of those requests, you can add further requests to the
		713	group. And only when all those requests have finished will the the group
		714	itself finish.
		715
		716	=over 4
		717
		718	=item add $grp ...
		719
		720	=item $grp->add (...)
		721
		722	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		723	be added, including other groups, as long as you do not create circular
		724	dependencies.
		725
		726	Returns all its arguments.
		727
		728	=item $grp->cancel_subs
		729
		730	Cancel all subrequests and clears any feeder, but not the group request
		731	itself. Useful when you queued a lot of events but got a result early.
		732
		733	=item $grp->result (...)
		734
		735	Set the result value(s) that will be passed to the group callback when all
		736	subrequests have finished and set thre groups errno to the current value
		737	of errno (just like calling C<errno> without an error number). By default,
		738	no argument will be passed and errno is zero.
		739
		740	=item $grp->errno ([$errno])
		741
		742	Sets the group errno value to C<$errno>, or the current value of errno
		743	when the argument is missing.
		744
		745	Every aio request has an associated errno value that is restored when
		746	the callback is invoked. This method lets you change this value from its
		747	default (0).
		748
		749	Calling C<result> will also set errno, so make sure you either set C<$!>
		750	before the call to C<result>, or call c<errno> after it.
		751
		752	=item feed $grp $callback->($grp)
		753
		754	Sets a feeder/generator on this group: every group can have an attached
		755	generator that generates requests if idle. The idea behind this is that,
		756	although you could just queue as many requests as you want in a group,
		757	this might starve other requests for a potentially long time. For
		758	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		759	requests, delaying any later requests for a long time.
		760
		761	To avoid this, and allow incremental generation of requests, you can
		762	instead a group and set a feeder on it that generates those requests. The
		763	feed callback will be called whenever there are few enough (see C<limit>,
		764	below) requests active in the group itself and is expected to queue more
		765	requests.
		766
		767	The feed callback can queue as many requests as it likes (i.e. C<add> does
		768	not impose any limits).
		769
		770	If the feed does not queue more requests when called, it will be
		771	automatically removed from the group.
		772
		773	If the feed limit is C<0>, it will be set to C<2> automatically.
		774
		775	Example:
		776
		777	# stat all files in @files, but only ever use four aio requests concurrently:
		778
		779	my $grp = aio_group sub { print "finished\n" };
		780	limit $grp 4;
		781	feed $grp sub {
		782	my $file = pop @files
		783	or return;
		784
		785	add $grp aio_stat $file, sub { ... };
		786	};
		787
		788	=item limit $grp $num
		789
		790	Sets the feeder limit for the group: The feeder will be called whenever
		791	the group contains less than this many requests.
		792
		793	Setting the limit to C<0> will pause the feeding process.
259		794
260	=back	795	=back
261		796
262	=head2 SUPPORT FUNCTIONS	797	=head2 SUPPORT FUNCTIONS
263		798
…		…
276		811
277	Process all outstanding events on the result pipe. You have to call this	812	Process all outstanding events on the result pipe. You have to call this
278	regularly. Returns the number of events processed. Returns immediately	813	regularly. Returns the number of events processed. Returns immediately
279	when no events are outstanding.	814	when no events are outstanding.
280		815
		816	If not all requests were processed for whatever reason, the filehandle
		817	will still be ready when C<poll_cb> returns.
		818
281	Example: Install an Event watcher that automatically calls	819	Example: Install an Event watcher that automatically calls
282	IO::AIO::poll_cb with high priority:	820	IO::AIO::poll_cb with high priority:
283		821
284	Event->io (fd => IO::AIO::poll_fileno,	822	Event->io (fd => IO::AIO::poll_fileno,
285	poll => 'r', async => 1,	823	poll => 'r', async => 1,
286	cb => \&IO::AIO::poll_cb);	824	cb => \&IO::AIO::poll_cb);
287		825
		826	=item IO::AIO::poll_some $max_requests
		827
		828	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests
		829	at a time.
		830
		831	Useful if you want to ensure some level of interactiveness when perl is
		832	not fast enough to process all requests in time.
		833
		834	Example: Install an Event watcher that automatically calls
		835	IO::AIO::poll_some with low priority, to ensure that other parts of the
		836	program get the CPU sometimes even under high AIO load.
		837
		838	Event->io (fd => IO::AIO::poll_fileno,
		839	poll => 'r', nice => 1,
		840	cb => sub { IO::AIO::poll_some 256 });
		841
288	=item IO::AIO::poll_wait	842	=item IO::AIO::poll_wait
289		843
290	Wait till the result filehandle becomes ready for reading (simply does a	844	Wait till the result filehandle becomes ready for reading (simply does a
291	C<select> on the filehandle. This is useful if you want to synchronously wait	845	C<select> on the filehandle. This is useful if you want to synchronously wait
292	for some requests to finish).	846	for some requests to finish).
293		847
294	See C<nreqs> for an example.	848	See C<nreqs> for an example.
295		849
296	=item IO::AIO::nreqs	850	=item IO::AIO::nreqs
297		851
298	Returns the number of requests currently outstanding (i.e. for which their	852	Returns the number of requests currently in the ready, execute or pending
299	callback has not been invoked yet).	853	states (i.e. for which their callback has not been invoked yet).
300		854
301	Example: wait till there are no outstanding requests anymore:	855	Example: wait till there are no outstanding requests anymore:
302		856
303	IO::AIO::poll_wait, IO::AIO::poll_cb	857	IO::AIO::poll_wait, IO::AIO::poll_cb
304	while IO::AIO::nreqs;	858	while IO::AIO::nreqs;
305		859
		860	=item IO::AIO::nready
		861
		862	Returns the number of requests currently in the ready state (not yet
		863	executed).
		864
		865	=item IO::AIO::npending
		866
		867	Returns the number of requests currently in the pending state (executed,
		868	but not yet processed by poll_cb).
		869
306	=item IO::AIO::flush	870	=item IO::AIO::flush
307		871
308	Wait till all outstanding AIO requests have been handled.	872	Wait till all outstanding AIO requests have been handled.
309		873
310	Strictly equivalent to:	874	Strictly equivalent to:
…		…
321	IO::AIO::poll_wait, IO::AIO::poll_cb	885	IO::AIO::poll_wait, IO::AIO::poll_cb
322	if IO::AIO::nreqs;	886	if IO::AIO::nreqs;
323		887
324	=item IO::AIO::min_parallel $nthreads	888	=item IO::AIO::min_parallel $nthreads
325		889
326	Set the minimum number of AIO threads to C<$nthreads>. The current default	890	Set the minimum number of AIO threads to C<$nthreads>. The current
327	is C<4>, which means four asynchronous operations can be done at one time	891	default is C<8>, which means eight asynchronous operations can execute
328	(the number of outstanding operations, however, is unlimited).	892	concurrently at any one time (the number of outstanding requests,
		893	however, is unlimited).
329		894
330	IO::AIO starts threads only on demand, when an AIO request is queued and	895	IO::AIO starts threads only on demand, when an AIO request is queued and
331	no free thread exists.	896	no free thread exists.
332		897
333	It is recommended to keep the number of threads low, as some Linux	898	It is recommended to keep the number of threads relatively low, as some
334	kernel versions will scale negatively with the number of threads (higher	899	Linux kernel versions will scale negatively with the number of threads
335	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	900	(higher parallelity => MUCH higher latency). With current Linux 2.6
336	threads should be fine.	901	versions, 4-32 threads should be fine.
337		902
338	Under most circumstances you don't need to call this function, as the	903	Under most circumstances you don't need to call this function, as the
339	module selects a default that is suitable for low to moderate load.	904	module selects a default that is suitable for low to moderate load.
340		905
341	=item IO::AIO::max_parallel $nthreads	906	=item IO::AIO::max_parallel $nthreads
…		…
350	This module automatically runs C<max_parallel 0> at program end, to ensure	915	This module automatically runs C<max_parallel 0> at program end, to ensure
351	that all threads are killed and that there are no outstanding requests.	916	that all threads are killed and that there are no outstanding requests.
352		917
353	Under normal circumstances you don't need to call this function.	918	Under normal circumstances you don't need to call this function.
354		919
355	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	920	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		921
		922	This is a very bad function to use in interactive programs because it
		923	blocks, and a bad way to reduce concurrency because it is inexact: Better
		924	use an C<aio_group> together with a feed callback.
356		925
357	Sets the maximum number of outstanding requests to C<$nreqs>. If you	926	Sets the maximum number of outstanding requests to C<$nreqs>. If you
358	try to queue up more than this number of requests, the caller will block until	927	to queue up more than this number of requests, the next call to the
359	some requests have been handled.	928	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		929	function will block until the limit is no longer exceeded.
360		930
361	The default is very large, so normally there is no practical limit. If you	931	The default value is very large, so there is no practical limit on the
362	queue up many requests in a loop it often improves speed if you set	932	number of outstanding requests.
363	this to a relatively low number, such as C<100>.
364		933
365	Under normal circumstances you don't need to call this function.	934	You can still queue as many requests as you want. Therefore,
		935	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		936	as a stop gap to shield against fatal memory overflow (with large values).
366		937
367	=back	938	=back
368		939
369	=cut	940	=cut
370		941
…		…
382	or return undef;	953	or return undef;
383		954
384	*$sym	955	*$sym
385	}	956	}
386		957
387	min_parallel 4;	958	min_parallel 8;
388
389	END {
390	max_parallel 0;
391	}
392		959
393	1;	960	1;
394		961
395	=head2 FORK BEHAVIOUR	962	=head2 FORK BEHAVIOUR
		963
		964	This module should do "the right thing" when the process using it forks:
396		965
397	Before the fork, IO::AIO enters a quiescent state where no requests	966	Before the fork, IO::AIO enters a quiescent state where no requests
398	can be added in other threads and no results will be processed. After	967	can be added in other threads and no results will be processed. After
399	the fork the parent simply leaves the quiescent state and continues	968	the fork the parent simply leaves the quiescent state and continues
400	request/result processing, while the child clears the request/result	969	request/result processing, while the child frees the request/result queue
401	queue (so the requests started before the fork will only be handled in	970	(so that the requests started before the fork will only be handled in the
402	the parent). Threats will be started on demand until the limit ste in the	971	parent). Threads will be started on demand until the limit set in the
403	parent process has been reached again.	972	parent process has been reached again.
404		973
		974	In short: the parent will, after a short pause, continue as if fork had
		975	not been called, while the child will act as if IO::AIO has not been used
		976	yet.
		977
		978	=head2 MEMORY USAGE
		979
		980	Per-request usage:
		981
		982	Each aio request uses - depending on your architecture - around 100-200
		983	bytes of memory. In addition, stat requests need a stat buffer (possibly
		984	a few hundred bytes), readdir requires a result buffer and so on. Perl
		985	scalars and other data passed into aio requests will also be locked and
		986	will consume memory till the request has entered the done state.
		987
		988	This is now awfully much, so queuing lots of requests is not usually a
		989	problem.
		990
		991	Per-thread usage:
		992
		993	In the execution phase, some aio requests require more memory for
		994	temporary buffers, and each thread requires a stack and other data
		995	structures (usually around 16k-128k, depending on the OS).
		996
		997	=head1 KNOWN BUGS
		998
		999	Known bugs will be fixed in the next release.
		1000
405	=head1 SEE ALSO	1001	=head1 SEE ALSO
406		1002
407	L<Coro>, L<Linux::AIO>.	1003	L<Coro::AIO>.
408		1004
409	=head1 AUTHOR	1005	=head1 AUTHOR
410		1006
411	Marc Lehmann <schmorp@schmorp.de>	1007	Marc Lehmann <schmorp@schmorp.de>
412	http://home.schmorp.de/	1008	http://home.schmorp.de/

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Revision 1.39 by root, Sun Aug 28 11:05:50 2005 UTC vs.
Revision 1.81 by root, Fri Oct 27 19:17:23 2006 UTC