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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.20 by root, Tue Jul 12 11:29:40 2005 UTC vs.
Revision 1.96 by root, Fri Dec 22 04:05:50 2006 UTC

…		…
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 {	9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	# Event	21	# version 2+ has request and group objects
		22	use IO::AIO 2;
		23
		24	aioreq_pri 4; # give next request a very high priority
		25	my $req = aio_unlink "/tmp/file", sub { };
		26	$req->cancel; # cancel request if still in queue
		27
		28	my $grp = aio_group sub { print "all stats done\n" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration
		32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		34
		35	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	36	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	37	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	38	cb => \&IO::AIO::poll_cb);
24		39
25	# Glib/Gtk2	40	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	41	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb, 1 };	42	in => sub { IO::AIO::poll_cb; 1 };
28		43
29	# Tk	44	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	46	readable => \&IO::AIO::poll_cb);
32		47
33	# Danga::Socket	48	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	50	\&IO::AIO::poll_cb);
36		51
37
38	=head1 DESCRIPTION	52	=head1 DESCRIPTION
39		53
40	This module implements asynchronous I/O using whatever means your	54	This module implements asynchronous I/O using whatever means your
41	operating system supports.	55	operating system supports.
42		56
		57	Asynchronous means that operations that can normally block your program
		58	(e.g. reading from disk) will be done asynchronously: the operation
		59	will still block, but you can do something else in the meantime. This
		60	is extremely useful for programs that need to stay interactive even
		61	when doing heavy I/O (GUI programs, high performance network servers
		62	etc.), but can also be used to easily do operations in parallel that are
		63	normally done sequentially, e.g. stat'ing many files, which is much faster
		64	on a RAID volume or over NFS when you do a number of stat operations
		65	concurrently.
		66
		67	While most of this works on all types of file descriptors (for example
		68	sockets), using these functions on file descriptors that support
		69	nonblocking operation (again, sockets, pipes etc.) is very inefficient or
		70	might not work (aio_read fails on sockets/pipes/fifos). Use an event loop
		71	for that (such as the L<Event\|Event> module): IO::AIO will naturally fit
		72	into such an event loop itself.
		73
43	Currently, a number of threads are started that execute your read/writes	74	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	75	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	76	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	77	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	78	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	79	not well-supported or restricted (GNU/Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	80	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	81	aio_write, so the remaining functionality would have to be implemented
		82	using threads anyway.
51		83
52	Although the module will work with in the presence of other threads, it is	84	Although the module will work with in the presence of other (Perl-)
53	currently not reentrant, so use appropriate locking yourself.	85	threads, it is currently not reentrant in any way, so use appropriate
		86	locking yourself, always call C<poll_cb> from within the same thread, or
		87	never call C<poll_cb> (or other C<aio_> functions) recursively.
		88
		89	=head2 EXAMPLE
		90
		91	This is a simple example that uses the Event module and loads
		92	F</etc/passwd> asynchronously:
		93
		94	use Fcntl;
		95	use Event;
		96	use IO::AIO;
		97
		98	# register the IO::AIO callback with Event
		99	Event->io (fd => IO::AIO::poll_fileno,
		100	poll => 'r',
		101	cb => \&IO::AIO::poll_cb);
		102
		103	# queue the request to open /etc/passwd
		104	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		105	my $fh = shift
		106	or die "error while opening: $!";
		107
		108	# stat'ing filehandles is generally non-blocking
		109	my $size = -s $fh;
		110
		111	# queue a request to read the file
		112	my $contents;
		113	aio_read $fh, 0, $size, $contents, 0, sub {
		114	$_[0] == $size
		115	or die "short read: $!";
		116
		117	close $fh;
		118
		119	# file contents now in $contents
		120	print $contents;
		121
		122	# exit event loop and program
		123	Event::unloop;
		124	};
		125	};
		126
		127	# possibly queue up other requests, or open GUI windows,
		128	# check for sockets etc. etc.
		129
		130	# process events as long as there are some:
		131	Event::loop;
		132
		133	=head1 REQUEST ANATOMY AND LIFETIME
		134
		135	Every C<aio_*> function creates a request. which is a C data structure not
		136	directly visible to Perl.
		137
		138	If called in non-void context, every request function returns a Perl
		139	object representing the request. In void context, nothing is returned,
		140	which saves a bit of memory.
		141
		142	The perl object is a fairly standard ref-to-hash object. The hash contents
		143	are not used by IO::AIO so you are free to store anything you like in it.
		144
		145	During their existance, aio requests travel through the following states,
		146	in order:
		147
		148	=over 4
		149
		150	=item ready
		151
		152	Immediately after a request is created it is put into the ready state,
		153	waiting for a thread to execute it.
		154
		155	=item execute
		156
		157	A thread has accepted the request for processing and is currently
		158	executing it (e.g. blocking in read).
		159
		160	=item pending
		161
		162	The request has been executed and is waiting for result processing.
		163
		164	While request submission and execution is fully asynchronous, result
		165	processing is not and relies on the perl interpreter calling C<poll_cb>
		166	(or another function with the same effect).
		167
		168	=item result
		169
		170	The request results are processed synchronously by C<poll_cb>.
		171
		172	The C<poll_cb> function will process all outstanding aio requests by
		173	calling their callbacks, freeing memory associated with them and managing
		174	any groups they are contained in.
		175
		176	=item done
		177
		178	Request has reached the end of its lifetime and holds no resources anymore
		179	(except possibly for the Perl object, but its connection to the actual
		180	aio request is severed and calling its methods will either do nothing or
		181	result in a runtime error).
		182
		183	=back
54		184
55	=cut	185	=cut
56		186
57	package IO::AIO;	187	package IO::AIO;
58		188
		189	no warnings;
		190	use strict 'vars';
		191
59	use base 'Exporter';	192	use base 'Exporter';
60		193
61	use Fcntl ();
62
63	BEGIN {	194	BEGIN {
64	$VERSION = 0.5;	195	our $VERSION = '2.21';
65		196
66	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	197	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
67	aio_fsync aio_fdatasync aio_readahead);	198	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
68	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	199	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
		200	aio_move aio_copy aio_group aio_nop aio_mknod);
		201	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		202	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		203	min_parallel max_parallel max_idle
		204	nreqs nready npending nthreads
		205	max_poll_time max_poll_reqs);
		206
		207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
69		208
70	require XSLoader;	209	require XSLoader;
71	XSLoader::load IO::AIO, $VERSION;	210	XSLoader::load ("IO::AIO", $VERSION);
72	}	211	}
73		212
74	=head1 FUNCTIONS	213	=head1 FUNCTIONS
75		214
76	=head2 AIO FUNCTIONS	215	=head2 AIO REQUEST FUNCTIONS
77		216
78	All the C<aio_*> calls are more or less thin wrappers around the syscall	217	All the C<aio_*> calls are more or less thin wrappers around the syscall
79	with the same name (sans C<aio_>). The arguments are similar or identical,	218	with the same name (sans C<aio_>). The arguments are similar or identical,
80	and they all accept an additional (and optional) C<$callback> argument	219	and they all accept an additional (and optional) C<$callback> argument
81	which must be a code reference. This code reference will get called with	220	which must be a code reference. This code reference will get called with
82	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	221	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
83	perl, which usually delivers "false") as it's sole argument when the given	222	perl, which usually delivers "false") as it's sole argument when the given
84	syscall has been executed asynchronously.	223	syscall has been executed asynchronously.
85		224
86	All functions that expect a filehandle will also accept a file descriptor.	225	All functions expecting a filehandle keep a copy of the filehandle
		226	internally until the request has finished.
87		227
		228	All functions return request objects of type L<IO::AIO::REQ> that allow
		229	further manipulation of those requests while they are in-flight.
		230
88	The filenames you pass to these routines I<must> be absolute. The reason	231	The pathnames you pass to these routines I<must> be absolute and
89	for this is that at the time the request is being executed, the current	232	encoded as octets. The reason for the former is that at the time the
90	working directory could have changed. Alternatively, you can make sure	233	request is being executed, the current working directory could have
91	that you never change the current working directory.	234	changed. Alternatively, you can make sure that you never change the
		235	current working directory anywhere in the program and then use relative
		236	paths.
		237
		238	To encode pathnames as octets, either make sure you either: a) always pass
		239	in filenames you got from outside (command line, readdir etc.) without
		240	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		241	your pathnames to the locale (or other) encoding in effect in the user
		242	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		243	use something else to ensure your scalar has the correct contents.
		244
		245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		246	handles correctly wether it is set or not.
92		247
93	=over 4	248	=over 4
94		249
		250	=item $prev_pri = aioreq_pri [$pri]
		251
		252	Returns the priority value that would be used for the next request and, if
		253	C<$pri> is given, sets the priority for the next aio request.
		254
		255	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		256	and C<4>, respectively. Requests with higher priority will be serviced
		257	first.
		258
		259	The priority will be reset to C<0> after each call to one of the C<aio_*>
		260	functions.
		261
		262	Example: open a file with low priority, then read something from it with
		263	higher priority so the read request is serviced before other low priority
		264	open requests (potentially spamming the cache):
		265
		266	aioreq_pri -3;
		267	aio_open ..., sub {
		268	return unless $_[0];
		269
		270	aioreq_pri -2;
		271	aio_read $_[0], ..., sub {
		272	...
		273	};
		274	};
		275
		276	=item aioreq_nice $pri_adjust
		277
		278	Similar to C<aioreq_pri>, but subtracts the given value from the current
		279	priority, so the effect is cumulative.
		280
95	=item aio_open $pathname, $flags, $mode, $callback	281	=item aio_open $pathname, $flags, $mode, $callback->($fh)
96		282
97	Asynchronously open or create a file and call the callback with a newly	283	Asynchronously open or create a file and call the callback with a newly
98	created filehandle for the file.	284	created filehandle for the file.
99		285
100	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	286	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
117	} else {	303	} else {
118	die "open failed: $!\n";	304	die "open failed: $!\n";
119	}	305	}
120	};	306	};
121		307
122	=item aio_close $fh, $callback	308	=item aio_close $fh, $callback->($status)
123		309
124	Asynchronously close a file and call the callback with the result	310	Asynchronously close a file and call the callback with the result
125	code. I<WARNING:> although accepted, you should not pass in a perl	311	code. I<WARNING:> although accepted, you should not pass in a perl
126	filehandle here, as perl will likely close the file descriptor another	312	filehandle here, as perl will likely close the file descriptor another
127	time when the filehandle is destroyed. Normally, you can safely call perls	313	time when the filehandle is destroyed. Normally, you can safely call perls
128	C<close> or just let filehandles go out of scope.	314	C<close> or just let filehandles go out of scope.
129		315
130	This is supposed to be a bug in the API, so that might change. It's	316	This is supposed to be a bug in the API, so that might change. It's
131	therefore best to avoid this function.	317	therefore best to avoid this function.
132		318
133	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	319	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
134		320
135	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	321	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
136		322
137	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	323	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
138	into the scalar given by C<data> and offset C<dataoffset> and calls the	324	into the scalar given by C<data> and offset C<dataoffset> and calls the
139	callback without the actual number of bytes read (or -1 on error, just	325	callback without the actual number of bytes read (or -1 on error, just
140	like the syscall).	326	like the syscall).
141		327
		328	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		329	is outstanding. Modifying it can result in segfaults or WW3 (if the
		330	necessary/optional hardware is installed).
		331
142	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	332	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
143	offset C<0> within the scalar:	333	offset C<0> within the scalar:
144		334
145	aio_read $fh, 7, 15, $buffer, 0, sub {	335	aio_read $fh, 7, 15, $buffer, 0, sub {
146	$_[0] > 0 or die "read error: $!";	336	$_[0] > 0 or die "read error: $!";
147	print "read $_[0] bytes: <$buffer>\n";	337	print "read $_[0] bytes: <$buffer>\n";
148	};	338	};
149		339
		340	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		341
		342	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		343	reading at byte offset C<$in_offset>, and starts writing at the current
		344	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		345	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		346	other.
		347
		348	This call tries to make use of a native C<sendfile> syscall to provide
		349	zero-copy operation. For this to work, C<$out_fh> should refer to a
		350	socket, and C<$in_fh> should refer to mmap'able file.
		351
		352	If the native sendfile call fails or is not implemented, it will be
		353	emulated, so you can call C<aio_sendfile> on any type of filehandle
		354	regardless of the limitations of the operating system.
		355
		356	Please note, however, that C<aio_sendfile> can read more bytes from
		357	C<$in_fh> than are written, and there is no way to find out how many
		358	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		359	provides the number of bytes written to C<$out_fh>. Only if the result
		360	value equals C<$length> one can assume that C<$length> bytes have been
		361	read.
		362
150	=item aio_readahead $fh,$offset,$length, $callback	363	=item aio_readahead $fh,$offset,$length, $callback->($retval)
151
152	Asynchronously reads the specified byte range into the page cache, using
153	the C<readahead> syscall. If that syscall doesn't exist (likely if your OS
154	isn't Linux) the status will be C<-1> and C<$!> is set to C<ENOSYS>.
155		364
156	C<aio_readahead> populates the page cache with data from a file so that	365	C<aio_readahead> populates the page cache with data from a file so that
157	subsequent reads from that file will not block on disk I/O. The C<$offset>	366	subsequent reads from that file will not block on disk I/O. The C<$offset>
158	argument specifies the starting point from which data is to be read and	367	argument specifies the starting point from which data is to be read and
159	C<$length> specifies the number of bytes to be read. I/O is performed in	368	C<$length> specifies the number of bytes to be read. I/O is performed in
160	whole pages, so that offset is effectively rounded down to a page boundary	369	whole pages, so that offset is effectively rounded down to a page boundary
161	and bytes are read up to the next page boundary greater than or equal to	370	and bytes are read up to the next page boundary greater than or equal to
162	(off-set+length). C<aio_readahead> does not read beyond the end of the	371	(off-set+length). C<aio_readahead> does not read beyond the end of the
163	file. The current file offset of the file is left unchanged.	372	file. The current file offset of the file is left unchanged.
164		373
		374	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		375	emulated by simply reading the data, which would have a similar effect.
		376
165	=item aio_stat $fh_or_path, $callback	377	=item aio_stat $fh_or_path, $callback->($status)
166		378
167	=item aio_lstat $fh, $callback	379	=item aio_lstat $fh, $callback->($status)
168		380
169	Works like perl's C<stat> or C<lstat> in void context. The callback will	381	Works like perl's C<stat> or C<lstat> in void context. The callback will
170	be called after the stat and the results will be available using C<stat _>	382	be called after the stat and the results will be available using C<stat _>
171	or C<-s _> etc...	383	or C<-s _> etc...
172		384
…		…
182	aio_stat "/etc/passwd", sub {	394	aio_stat "/etc/passwd", sub {
183	$_[0] and die "stat failed: $!";	395	$_[0] and die "stat failed: $!";
184	print "size is ", -s _, "\n";	396	print "size is ", -s _, "\n";
185	};	397	};
186		398
187	=item aio_unlink $pathname, $callback	399	=item aio_unlink $pathname, $callback->($status)
188		400
189	Asynchronously unlink (delete) a file and call the callback with the	401	Asynchronously unlink (delete) a file and call the callback with the
190	result code.	402	result code.
191		403
		404	=item aio_mknod $path, $mode, $dev, $callback->($status)
		405
		406	[EXPERIMENTAL]
		407
		408	Asynchronously create a device node (or fifo). See mknod(2).
		409
		410	The only (POSIX-) portable way of calling this function is:
		411
		412	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		413
		414	=item aio_link $srcpath, $dstpath, $callback->($status)
		415
		416	Asynchronously create a new 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_symlink $srcpath, $dstpath, $callback->($status)
		420
		421	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		422	the path C<$dstpath> and call the callback with the result code.
		423
		424	=item aio_readlink $path, $callback->($link)
		425
		426	Asynchronously read the symlink specified by C<$path> and pass it to
		427	the callback. If an error occurs, nothing or undef gets passed to the
		428	callback.
		429
		430	=item aio_rename $srcpath, $dstpath, $callback->($status)
		431
		432	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		433	rename(2) and call the callback with the result code.
		434
		435	=item aio_rmdir $pathname, $callback->($status)
		436
		437	Asynchronously rmdir (delete) a directory and call the callback with the
		438	result code.
		439
		440	=item aio_readdir $pathname, $callback->($entries)
		441
		442	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		443	directory (i.e. opendir + readdir + closedir). The entries will not be
		444	sorted, and will B<NOT> include the C<.> and C<..> entries.
		445
		446	The callback a single argument which is either C<undef> or an array-ref
		447	with the filenames.
		448
		449	=item aio_copy $srcpath, $dstpath, $callback->($status)
		450
		451	Try to copy the I<file> (directories not supported as either source or
		452	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		453	the C<0> (error) or C<-1> ok.
		454
		455	This is a composite request that it creates the destination file with
		456	mode 0200 and copies the contents of the source file into it using
		457	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		458	uid/gid, in that order.
		459
		460	If an error occurs, the partial destination file will be unlinked, if
		461	possible, except when setting atime, mtime, access mode and uid/gid, where
		462	errors are being ignored.
		463
		464	=cut
		465
		466	sub aio_copy($$;$) {
		467	aio_block {
		468	my ($src, $dst, $cb) = @_;
		469
		470	my $pri = aioreq_pri;
		471	my $grp = aio_group $cb;
		472
		473	aioreq_pri $pri;
		474	add $grp aio_open $src, O_RDONLY, 0, sub {
		475	if (my $src_fh = $_[0]) {
		476	my @stat = stat $src_fh;
		477
		478	aioreq_pri $pri;
		479	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		480	if (my $dst_fh = $_[0]) {
		481	aioreq_pri $pri;
		482	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		483	if ($_[0] == $stat[7]) {
		484	$grp->result (0);
		485	close $src_fh;
		486
		487	# those should not normally block. should. should.
		488	utime $stat[8], $stat[9], $dst;
		489	chmod $stat[2] & 07777, $dst_fh;
		490	chown $stat[4], $stat[5], $dst_fh;
		491	close $dst_fh;
		492	} else {
		493	$grp->result (-1);
		494	close $src_fh;
		495	close $dst_fh;
		496
		497	aioreq $pri;
		498	add $grp aio_unlink $dst;
		499	}
		500	};
		501	} else {
		502	$grp->result (-1);
		503	}
		504	},
		505
		506	} else {
		507	$grp->result (-1);
		508	}
		509	};
		510
		511	$grp
		512	}
		513	}
		514
		515	=item aio_move $srcpath, $dstpath, $callback->($status)
		516
		517	Try to move the I<file> (directories not supported as either source or
		518	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		519	the C<0> (error) or C<-1> ok.
		520
		521	This is a composite request that tries to rename(2) the file first. If
		522	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		523	that is successful, unlinking the C<$srcpath>.
		524
		525	=cut
		526
		527	sub aio_move($$;$) {
		528	aio_block {
		529	my ($src, $dst, $cb) = @_;
		530
		531	my $pri = aioreq_pri;
		532	my $grp = aio_group $cb;
		533
		534	aioreq_pri $pri;
		535	add $grp aio_rename $src, $dst, sub {
		536	if ($_[0] && $! == EXDEV) {
		537	aioreq_pri $pri;
		538	add $grp aio_copy $src, $dst, sub {
		539	$grp->result ($_[0]);
		540
		541	if (!$_[0]) {
		542	aioreq_pri $pri;
		543	add $grp aio_unlink $src;
		544	}
		545	};
		546	} else {
		547	$grp->result ($_[0]);
		548	}
		549	};
		550
		551	$grp
		552	}
		553	}
		554
		555	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		556
		557	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		558	efficiently separate the entries of directory C<$path> into two sets of
		559	names, directories you can recurse into (directories), and ones you cannot
		560	recurse into (everything else, including symlinks to directories).
		561
		562	C<aio_scandir> is a composite request that creates of many sub requests_
		563	C<$maxreq> specifies the maximum number of outstanding aio requests that
		564	this function generates. If it is C<< <= 0 >>, then a suitable default
		565	will be chosen (currently 4).
		566
		567	On error, the callback is called without arguments, otherwise it receives
		568	two array-refs with path-relative entry names.
		569
		570	Example:
		571
		572	aio_scandir $dir, 0, sub {
		573	my ($dirs, $nondirs) = @_;
		574	print "real directories: @$dirs\n";
		575	print "everything else: @$nondirs\n";
		576	};
		577
		578	Implementation notes.
		579
		580	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		581
		582	After reading the directory, the modification time, size etc. of the
		583	directory before and after the readdir is checked, and if they match (and
		584	isn't the current time), the link count will be used to decide how many
		585	entries are directories (if >= 2). Otherwise, no knowledge of the number
		586	of subdirectories will be assumed.
		587
		588	Then entries will be sorted into likely directories (everything without
		589	a non-initial dot currently) and likely non-directories (everything
		590	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		591	likely directories first. If that succeeds, it assumes that the entry
		592	is a directory or a symlink to directory (which will be checked
		593	seperately). This is often faster than stat'ing the entry itself because
		594	filesystems might detect the type of the entry without reading the inode
		595	data (e.g. ext2fs filetype feature).
		596
		597	If the known number of directories (link count - 2) has been reached, the
		598	rest of the entries is assumed to be non-directories.
		599
		600	This only works with certainty on POSIX (= UNIX) filesystems, which
		601	fortunately are the vast majority of filesystems around.
		602
		603	It will also likely work on non-POSIX filesystems with reduced efficiency
		604	as those tend to return 0 or 1 as link counts, which disables the
		605	directory counting heuristic.
		606
		607	=cut
		608
		609	sub aio_scandir($$$) {
		610	aio_block {
		611	my ($path, $maxreq, $cb) = @_;
		612
		613	my $pri = aioreq_pri;
		614
		615	my $grp = aio_group $cb;
		616
		617	$maxreq = 4 if $maxreq <= 0;
		618
		619	# stat once
		620	aioreq_pri $pri;
		621	add $grp aio_stat $path, sub {
		622	return $grp->result () if $_[0];
		623	my $now = time;
		624	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		625
		626	# read the directory entries
		627	aioreq_pri $pri;
		628	add $grp aio_readdir $path, sub {
		629	my $entries = shift
		630	or return $grp->result ();
		631
		632	# stat the dir another time
		633	aioreq_pri $pri;
		634	add $grp aio_stat $path, sub {
		635	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		636
		637	my $ndirs;
		638
		639	# take the slow route if anything looks fishy
		640	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		641	$ndirs = -1;
		642	} else {
		643	# if nlink == 2, we are finished
		644	# on non-posix-fs's, we rely on nlink < 2
		645	$ndirs = (stat _)[3] - 2
		646	or return $grp->result ([], $entries);
		647	}
		648
		649	# sort into likely dirs and likely nondirs
		650	# dirs == files without ".", short entries first
		651	$entries = [map $_->[0],
		652	sort { $b->[1] cmp $a->[1] }
		653	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		654	@$entries];
		655
		656	my (@dirs, @nondirs);
		657
		658	my $statgrp = add $grp aio_group sub {
		659	$grp->result (\@dirs, \@nondirs);
		660	};
		661
		662	limit $statgrp $maxreq;
		663	feed $statgrp sub {
		664	return unless @$entries;
		665	my $entry = pop @$entries;
		666
		667	aioreq_pri $pri;
		668	add $statgrp aio_stat "$path/$entry/.", sub {
		669	if ($_[0] < 0) {
		670	push @nondirs, $entry;
		671	} else {
		672	# need to check for real directory
		673	aioreq_pri $pri;
		674	add $statgrp aio_lstat "$path/$entry", sub {
		675	if (-d _) {
		676	push @dirs, $entry;
		677
		678	unless (--$ndirs) {
		679	push @nondirs, @$entries;
		680	feed $statgrp;
		681	}
		682	} else {
		683	push @nondirs, $entry;
		684	}
		685	}
		686	}
		687	};
		688	};
		689	};
		690	};
		691	};
		692
		693	$grp
		694	}
		695	}
		696
192	=item aio_fsync $fh, $callback	697	=item aio_fsync $fh, $callback->($status)
193		698
194	Asynchronously call fsync on the given filehandle and call the callback	699	Asynchronously call fsync on the given filehandle and call the callback
195	with the fsync result code.	700	with the fsync result code.
196		701
197	=item aio_fdatasync $fh, $callback	702	=item aio_fdatasync $fh, $callback->($status)
198		703
199	Asynchronously call fdatasync on the given filehandle and call the	704	Asynchronously call fdatasync on the given filehandle and call the
200	callback with the fdatasync result code. Might set C<$!> to C<ENOSYS> if	705	callback with the fdatasync result code.
201	C<fdatasync> is not available.	706
		707	If this call isn't available because your OS lacks it or it couldn't be
		708	detected, it will be emulated by calling C<fsync> instead.
		709
		710	=item aio_group $callback->(...)
		711
		712	This is a very special aio request: Instead of doing something, it is a
		713	container for other aio requests, which is useful if you want to bundle
		714	many requests into a single, composite, request with a definite callback
		715	and the ability to cancel the whole request with its subrequests.
		716
		717	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		718	for more info.
		719
		720	Example:
		721
		722	my $grp = aio_group sub {
		723	print "all stats done\n";
		724	};
		725
		726	add $grp
		727	(aio_stat ...),
		728	(aio_stat ...),
		729	...;
		730
		731	=item aio_nop $callback->()
		732
		733	This is a special request - it does nothing in itself and is only used for
		734	side effects, such as when you want to add a dummy request to a group so
		735	that finishing the requests in the group depends on executing the given
		736	code.
		737
		738	While this request does nothing, it still goes through the execution
		739	phase and still requires a worker thread. Thus, the callback will not
		740	be executed immediately but only after other requests in the queue have
		741	entered their execution phase. This can be used to measure request
		742	latency.
		743
		744	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		745
		746	Mainly used for debugging and benchmarking, this aio request puts one of
		747	the request workers to sleep for the given time.
		748
		749	While it is theoretically handy to have simple I/O scheduling requests
		750	like sleep and file handle readable/writable, the overhead this creates is
		751	immense (it blocks a thread for a long time) so do not use this function
		752	except to put your application under artificial I/O pressure.
202		753
203	=back	754	=back
204		755
		756	=head2 IO::AIO::REQ CLASS
		757
		758	All non-aggregate C<aio_*> functions return an object of this class when
		759	called in non-void context.
		760
		761	=over 4
		762
		763	=item cancel $req
		764
		765	Cancels the request, if possible. Has the effect of skipping execution
		766	when entering the B<execute> state and skipping calling the callback when
		767	entering the the B<result> state, but will leave the request otherwise
		768	untouched. That means that requests that currently execute will not be
		769	stopped and resources held by the request will not be freed prematurely.
		770
		771	=item cb $req $callback->(...)
		772
		773	Replace (or simply set) the callback registered to the request.
		774
		775	=back
		776
		777	=head2 IO::AIO::GRP CLASS
		778
		779	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		780	objects of this class, too.
		781
		782	A IO::AIO::GRP object is a special request that can contain multiple other
		783	aio requests.
		784
		785	You create one by calling the C<aio_group> constructing function with a
		786	callback that will be called when all contained requests have entered the
		787	C<done> state:
		788
		789	my $grp = aio_group sub {
		790	print "all requests are done\n";
		791	};
		792
		793	You add requests by calling the C<add> method with one or more
		794	C<IO::AIO::REQ> objects:
		795
		796	$grp->add (aio_unlink "...");
		797
		798	add $grp aio_stat "...", sub {
		799	$_[0] or return $grp->result ("error");
		800
		801	# add another request dynamically, if first succeeded
		802	add $grp aio_open "...", sub {
		803	$grp->result ("ok");
		804	};
		805	};
		806
		807	This makes it very easy to create composite requests (see the source of
		808	C<aio_move> for an application) that work and feel like simple requests.
		809
		810	=over 4
		811
		812	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		813	C<IO::AIO::poll_cb>, just like any other request.
		814
		815	=item * They can be canceled like any other request. Canceling will cancel not
		816	only the request itself, but also all requests it contains.
		817
		818	=item * They can also can also be added to other IO::AIO::GRP objects.
		819
		820	=item * You must not add requests to a group from within the group callback (or
		821	any later time).
		822
		823	=back
		824
		825	Their lifetime, simplified, looks like this: when they are empty, they
		826	will finish very quickly. If they contain only requests that are in the
		827	C<done> state, they will also finish. Otherwise they will continue to
		828	exist.
		829
		830	That means after creating a group you have some time to add requests. And
		831	in the callbacks of those requests, you can add further requests to the
		832	group. And only when all those requests have finished will the the group
		833	itself finish.
		834
		835	=over 4
		836
		837	=item add $grp ...
		838
		839	=item $grp->add (...)
		840
		841	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		842	be added, including other groups, as long as you do not create circular
		843	dependencies.
		844
		845	Returns all its arguments.
		846
		847	=item $grp->cancel_subs
		848
		849	Cancel all subrequests and clears any feeder, but not the group request
		850	itself. Useful when you queued a lot of events but got a result early.
		851
		852	=item $grp->result (...)
		853
		854	Set the result value(s) that will be passed to the group callback when all
		855	subrequests have finished and set thre groups errno to the current value
		856	of errno (just like calling C<errno> without an error number). By default,
		857	no argument will be passed and errno is zero.
		858
		859	=item $grp->errno ([$errno])
		860
		861	Sets the group errno value to C<$errno>, or the current value of errno
		862	when the argument is missing.
		863
		864	Every aio request has an associated errno value that is restored when
		865	the callback is invoked. This method lets you change this value from its
		866	default (0).
		867
		868	Calling C<result> will also set errno, so make sure you either set C<$!>
		869	before the call to C<result>, or call c<errno> after it.
		870
		871	=item feed $grp $callback->($grp)
		872
		873	Sets a feeder/generator on this group: every group can have an attached
		874	generator that generates requests if idle. The idea behind this is that,
		875	although you could just queue as many requests as you want in a group,
		876	this might starve other requests for a potentially long time. For
		877	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		878	requests, delaying any later requests for a long time.
		879
		880	To avoid this, and allow incremental generation of requests, you can
		881	instead a group and set a feeder on it that generates those requests. The
		882	feed callback will be called whenever there are few enough (see C<limit>,
		883	below) requests active in the group itself and is expected to queue more
		884	requests.
		885
		886	The feed callback can queue as many requests as it likes (i.e. C<add> does
		887	not impose any limits).
		888
		889	If the feed does not queue more requests when called, it will be
		890	automatically removed from the group.
		891
		892	If the feed limit is C<0>, it will be set to C<2> automatically.
		893
		894	Example:
		895
		896	# stat all files in @files, but only ever use four aio requests concurrently:
		897
		898	my $grp = aio_group sub { print "finished\n" };
		899	limit $grp 4;
		900	feed $grp sub {
		901	my $file = pop @files
		902	or return;
		903
		904	add $grp aio_stat $file, sub { ... };
		905	};
		906
		907	=item limit $grp $num
		908
		909	Sets the feeder limit for the group: The feeder will be called whenever
		910	the group contains less than this many requests.
		911
		912	Setting the limit to C<0> will pause the feeding process.
		913
		914	=back
		915
205	=head2 SUPPORT FUNCTIONS	916	=head2 SUPPORT FUNCTIONS
		917
		918	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
206		919
207	=over 4	920	=over 4
208		921
209	=item $fileno = IO::AIO::poll_fileno	922	=item $fileno = IO::AIO::poll_fileno
210		923
…		…
215		928
216	See C<poll_cb> for an example.	929	See C<poll_cb> for an example.
217		930
218	=item IO::AIO::poll_cb	931	=item IO::AIO::poll_cb
219		932
220	Process all outstanding events on the result pipe. You have to call this	933	Process some outstanding events on the result pipe. You have to call this
221	regularly. Returns the number of events processed. Returns immediately	934	regularly. Returns the number of events processed. Returns immediately
222	when no events are outstanding.	935	when no events are outstanding. The amount of events processed depends on
		936	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		937
		938	If not all requests were processed for whatever reason, the filehandle
		939	will still be ready when C<poll_cb> returns.
223		940
224	Example: Install an Event watcher that automatically calls	941	Example: Install an Event watcher that automatically calls
225	IO::AIO::poll_cb with high priority:	942	IO::AIO::poll_cb with high priority:
226		943
227	Event->io (fd => IO::AIO::poll_fileno,	944	Event->io (fd => IO::AIO::poll_fileno,
228	poll => 'r', async => 1,	945	poll => 'r', async => 1,
229	cb => \&IO::AIO::poll_cb);	946	cb => \&IO::AIO::poll_cb);
230		947
		948	=item IO::AIO::max_poll_reqs $nreqs
		949
		950	=item IO::AIO::max_poll_time $seconds
		951
		952	These set the maximum number of requests (default C<0>, meaning infinity)
		953	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		954	the maximum amount of time (default C<0>, meaning infinity) spent in
		955	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		956	of time C<poll_cb> is allowed to use).
		957
		958	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		959	syscall per request processed, which is not normally a problem unless your
		960	callbacks are really really fast or your OS is really really slow (I am
		961	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		962
		963	Setting these is useful if you want to ensure some level of
		964	interactiveness when perl is not fast enough to process all requests in
		965	time.
		966
		967	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		968
		969	Example: Install an Event watcher that automatically calls
		970	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		971	program get the CPU sometimes even under high AIO load.
		972
		973	# try not to spend much more than 0.1s in poll_cb
		974	IO::AIO::max_poll_time 0.1;
		975
		976	# use a low priority so other tasks have priority
		977	Event->io (fd => IO::AIO::poll_fileno,
		978	poll => 'r', nice => 1,
		979	cb => &IO::AIO::poll_cb);
		980
231	=item IO::AIO::poll_wait	981	=item IO::AIO::poll_wait
232		982
		983	If there are any outstanding requests and none of them in the result
233	Wait till the result filehandle becomes ready for reading (simply does a	984	phase, wait till the result filehandle becomes ready for reading (simply
234	C<select> on the filehandle. This is useful if you want to synchronously wait	985	does a C<select> on the filehandle. This is useful if you want to
235	for some requests to finish).	986	synchronously wait for some requests to finish).
236		987
237	See C<nreqs> for an example.	988	See C<nreqs> for an example.
238		989
		990	=item IO::AIO::poll
		991
		992	Waits until some requests have been handled.
		993
		994	Returns the number of requests processed, but is otherwise strictly
		995	equivalent to:
		996
		997	IO::AIO::poll_wait, IO::AIO::poll_cb
		998
239	=item IO::AIO::nreqs	999	=item IO::AIO::flush
240		1000
241	Returns the number of requests currently outstanding (i.e. for which their	1001	Wait till all outstanding AIO requests have been handled.
242	callback has not been invoked yet).
243		1002
244	Example: wait till there are no outstanding requests anymore:	1003	Strictly equivalent to:
245		1004
246	IO::AIO::poll_wait, IO::AIO::poll_cb	1005	IO::AIO::poll_wait, IO::AIO::poll_cb
247	while IO::AIO::nreqs;	1006	while IO::AIO::nreqs;
248		1007
		1008	=head3 CONTROLLING THE NUMBER OF THREADS
		1009
		1010	=item IO::AIO::min_parallel $nthreads
		1011
		1012	Set the minimum number of AIO threads to C<$nthreads>. The current
		1013	default is C<8>, which means eight asynchronous operations can execute
		1014	concurrently at any one time (the number of outstanding requests,
		1015	however, is unlimited).
		1016
		1017	IO::AIO starts threads only on demand, when an AIO request is queued and
		1018	no free thread exists. Please note that queueing up a hundred requests can
		1019	create demand for a hundred threads, even if it turns out that everything
		1020	is in the cache and could have been processed faster by a single thread.
		1021
		1022	It is recommended to keep the number of threads relatively low, as some
		1023	Linux kernel versions will scale negatively with the number of threads
		1024	(higher parallelity => MUCH higher latency). With current Linux 2.6
		1025	versions, 4-32 threads should be fine.
		1026
		1027	Under most circumstances you don't need to call this function, as the
		1028	module selects a default that is suitable for low to moderate load.
		1029
		1030	=item IO::AIO::max_parallel $nthreads
		1031
		1032	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		1033	specified number of threads are currently running, this function kills
		1034	them. This function blocks until the limit is reached.
		1035
		1036	While C<$nthreads> are zero, aio requests get queued but not executed
		1037	until the number of threads has been increased again.
		1038
		1039	This module automatically runs C<max_parallel 0> at program end, to ensure
		1040	that all threads are killed and that there are no outstanding requests.
		1041
		1042	Under normal circumstances you don't need to call this function.
		1043
		1044	=item IO::AIO::max_idle $nthreads
		1045
		1046	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1047	threads that did not get a request to process within 10 seconds). That
		1048	means if a thread becomes idle while C<$nthreads> other threads are also
		1049	idle, it will free its resources and exit.
		1050
		1051	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1052	to allow for extremely high load situations, but want to free resources
		1053	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1054
		1055	The default is probably ok in most situations, especially if thread
		1056	creation is fast. If thread creation is very slow on your system you might
		1057	want to use larger values.
		1058
		1059	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1060
		1061	This is a very bad function to use in interactive programs because it
		1062	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1063	use an C<aio_group> together with a feed callback.
		1064
		1065	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		1066	to queue up more than this number of requests, the next call to the
		1067	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1068	function will block until the limit is no longer exceeded.
		1069
		1070	The default value is very large, so there is no practical limit on the
		1071	number of outstanding requests.
		1072
		1073	You can still queue as many requests as you want. Therefore,
		1074	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1075	as a stop gap to shield against fatal memory overflow (with large values).
		1076
		1077	=head3 STATISTICAL INFORMATION
		1078
249	=item IO::AIO::flush	1079	=item IO::AIO::nreqs
250		1080
251	Wait till all outstanding AIO requests have been handled.	1081	Returns the number of requests currently in the ready, execute or pending
		1082	states (i.e. for which their callback has not been invoked yet).
252		1083
253	Strictly equivalent to:	1084	Example: wait till there are no outstanding requests anymore:
254		1085
255	IO::AIO::poll_wait, IO::AIO::poll_cb	1086	IO::AIO::poll_wait, IO::AIO::poll_cb
256	while IO::AIO::nreqs;	1087	while IO::AIO::nreqs;
257		1088
		1089	=item IO::AIO::nready
		1090
		1091	Returns the number of requests currently in the ready state (not yet
		1092	executed).
		1093
258	=item IO::AIO::poll	1094	=item IO::AIO::npending
259		1095
260	Waits until some requests have been handled.	1096	Returns the number of requests currently in the pending state (executed,
261		1097	but not yet processed by poll_cb).
262	Strictly equivalent to:
263
264	IO::AIO::poll_wait, IO::AIO::poll_cb
265	if IO::AIO::nreqs;
266
267	=item IO::AIO::min_parallel $nthreads
268
269	Set the minimum number of AIO threads to C<$nthreads>. The default is
270	C<1>, which means a single asynchronous operation can be done at one time
271	(the number of outstanding operations, however, is unlimited).
272
273	It is recommended to keep the number of threads low, as some Linux
274	kernel versions will scale negatively with the number of threads (higher
275	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
276	threads should be fine.
277
278	Under normal circumstances you don't need to call this function, as this
279	module automatically starts some threads (the exact number might change,
280	and is currently 4).
281
282	=item IO::AIO::max_parallel $nthreads
283
284	Sets the maximum number of AIO threads to C<$nthreads>. If more than
285	the specified number of threads are currently running, kill them. This
286	function blocks until the limit is reached.
287
288	This module automatically runs C<max_parallel 0> at program end, to ensure
289	that all threads are killed and that there are no outstanding requests.
290
291	Under normal circumstances you don't need to call this function.
292
293	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
294
295	Sets the maximum number of outstanding requests to C<$nreqs>. If you
296	try to queue up more than this number of requests, the caller will block until
297	some requests have been handled.
298
299	The default is very large, so normally there is no practical limit. If you
300	queue up many requests in a loop it it often improves speed if you set
301	this to a relatively low number, such as C<100>.
302
303	Under normal circumstances you don't need to call this function.
304		1098
305	=back	1099	=back
306		1100
307	=cut	1101	=cut
308		1102
309	# support function to convert a fd into a perl filehandle	1103	# support function to convert a fd into a perl filehandle
310	sub _fd2fh {	1104	sub _fd2fh {
311	return undef if $_[0] < 0;	1105	return undef if $_[0] < 0;
312		1106
313	# try to be perl5.6-compatible	1107	# try to generate nice filehandles
314	local *AIO_FH;	1108	my $sym = "IO::AIO::fd#$_[0]";
315	open AIO_FH, "+<&=$_[0]"	1109	local *$sym;
		1110
		1111	open *$sym, "+<&=$_[0]" # usually works under any unix
		1112	or open *$sym, "<&=$_[0]" # cygwin needs this
		1113	or open *$sym, ">&=$_[0]" # or this
316	or return undef;	1114	or return undef;
317		1115
318	*AIO_FH	1116	*$sym
319	}	1117	}
320		1118
321	min_parallel 4;	1119	min_parallel 8;
322		1120
323	END {	1121	END { flush }
324	max_parallel 0;
325	}
326		1122
327	1;	1123	1;
328		1124
		1125	=head2 FORK BEHAVIOUR
		1126
		1127	This module should do "the right thing" when the process using it forks:
		1128
		1129	Before the fork, IO::AIO enters a quiescent state where no requests
		1130	can be added in other threads and no results will be processed. After
		1131	the fork the parent simply leaves the quiescent state and continues
		1132	request/result processing, while the child frees the request/result queue
		1133	(so that the requests started before the fork will only be handled in the
		1134	parent). Threads will be started on demand until the limit set in the
		1135	parent process has been reached again.
		1136
		1137	In short: the parent will, after a short pause, continue as if fork had
		1138	not been called, while the child will act as if IO::AIO has not been used
		1139	yet.
		1140
		1141	=head2 MEMORY USAGE
		1142
		1143	Per-request usage:
		1144
		1145	Each aio request uses - depending on your architecture - around 100-200
		1146	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1147	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1148	scalars and other data passed into aio requests will also be locked and
		1149	will consume memory till the request has entered the done state.
		1150
		1151	This is now awfully much, so queuing lots of requests is not usually a
		1152	problem.
		1153
		1154	Per-thread usage:
		1155
		1156	In the execution phase, some aio requests require more memory for
		1157	temporary buffers, and each thread requires a stack and other data
		1158	structures (usually around 16k-128k, depending on the OS).
		1159
		1160	=head1 KNOWN BUGS
		1161
		1162	Known bugs will be fixed in the next release.
		1163
329	=head1 SEE ALSO	1164	=head1 SEE ALSO
330		1165
331	L<Coro>, L<Linux::AIO>.	1166	L<Coro::AIO>.
332		1167
333	=head1 AUTHOR	1168	=head1 AUTHOR
334		1169
335	Marc Lehmann <schmorp@schmorp.de>	1170	Marc Lehmann <schmorp@schmorp.de>
336	http://home.schmorp.de/	1171	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.20 by root, Tue Jul 12 11:29:40 2005 UTC vs. Revision 1.96 by root, Fri Dec 22 04:05:50 2006 UTC

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Revision 1.20 by root, Tue Jul 12 11:29:40 2005 UTC vs.
Revision 1.96 by root, Fri Dec 22 04:05:50 2006 UTC