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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.30 by root, Wed Aug 17 04:47:38 2005 UTC vs.
Revision 1.98 by root, Sun Dec 31 17:07:32 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, always call	85	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	86	locking yourself, always call C<poll_cb> from within the same thread, or
55	C<aio_> functions) recursively.	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
56		184
57	=cut	185	=cut
58		186
59	package IO::AIO;	187	package IO::AIO;
60		188
61	no warnings;	189	no warnings;
		190	use strict 'vars';
62		191
63	use base 'Exporter';	192	use base 'Exporter';
64		193
65	use Fcntl ();
66
67	BEGIN {	194	BEGIN {
68	$VERSION = 1.2;	195	our $VERSION = '2.31';
69		196
70	@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
		198	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
71	aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead);	199	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
72	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	200	aio_move aio_copy aio_group aio_nop aio_mknod aio_load);
		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';
73		208
74	require XSLoader;	209	require XSLoader;
75	XSLoader::load IO::AIO, $VERSION;	210	XSLoader::load ("IO::AIO", $VERSION);
76	}	211	}
77		212
78	=head1 FUNCTIONS	213	=head1 FUNCTIONS
79		214
80	=head2 AIO FUNCTIONS	215	=head2 AIO REQUEST FUNCTIONS
81		216
82	All the C<aio_*> calls are more or less thin wrappers around the syscall	217	All the C<aio_*> calls are more or less thin wrappers around the syscall
83	with the same name (sans C<aio_>). The arguments are similar or identical,	218	with the same name (sans C<aio_>). The arguments are similar or identical,
84	and they all accept an additional (and optional) C<$callback> argument	219	and they all accept an additional (and optional) C<$callback> argument
85	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
…		…
88	syscall has been executed asynchronously.	223	syscall has been executed asynchronously.
89		224
90	All functions expecting a filehandle keep a copy of the filehandle	225	All functions expecting a filehandle keep a copy of the filehandle
91	internally until the request has finished.	226	internally until the request has finished.
92		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
93	The pathnames you pass to these routines I<must> be absolute and	231	The pathnames you pass to these routines I<must> be absolute and
94	encoded in byte form. The reason for the former is that at the time the	232	encoded as octets. The reason for the former is that at the time the
95	request is being executed, the current working directory could have	233	request is being executed, the current working directory could have
96	changed. Alternatively, you can make sure that you never change the	234	changed. Alternatively, you can make sure that you never change the
97	current working directory.	235	current working directory anywhere in the program and then use relative
		236	paths.
98		237
99	To encode pathnames to byte form, either make sure you either: a)	238	To encode pathnames as octets, either make sure you either: a) always pass
100	always pass in filenames you got from outside (command line, readdir	239	in filenames you got from outside (command line, readdir etc.) without
101	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	240	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
102	your pathnames to the locale (or other) encoding in effect in the user	241	your pathnames to the locale (or other) encoding in effect in the user
103	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	242	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
104	use something else.	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.
105		247
106	=over 4	248	=over 4
107		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
108	=item aio_open $pathname, $flags, $mode, $callback	281	=item aio_open $pathname, $flags, $mode, $callback->($fh)
109		282
110	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
111	created filehandle for the file.	284	created filehandle for the file.
112		285
113	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,
…		…
130	} else {	303	} else {
131	die "open failed: $!\n";	304	die "open failed: $!\n";
132	}	305	}
133	};	306	};
134		307
135	=item aio_close $fh, $callback	308	=item aio_close $fh, $callback->($status)
136		309
137	Asynchronously close a file and call the callback with the result	310	Asynchronously close a file and call the callback with the result
138	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
139	filehandle here, as perl will likely close the file descriptor another	312	filehandle here, as perl will likely close the file descriptor another
140	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
141	C<close> or just let filehandles go out of scope.	314	C<close> or just let filehandles go out of scope.
142		315
143	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
144	therefore best to avoid this function.	317	therefore best to avoid this function.
145		318
146	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	319	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
147		320
148	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	321	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149		322
150	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>
151	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
152	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
153	like the syscall).	326	like the syscall).
154		327
		328	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		329	is outstanding. Modifying it can result in segfaults or WW3 (if the
		330	necessary/optional hardware is installed).
		331
155	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	332	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
156	offset C<0> within the scalar:	333	offset C<0> within the scalar:
157		334
158	aio_read $fh, 7, 15, $buffer, 0, sub {	335	aio_read $fh, 7, 15, $buffer, 0, sub {
159	$_[0] > 0 or die "read error: $!";	336	$_[0] > 0 or die "read error: $!";
160	print "read $_[0] bytes: <$buffer>\n";	337	print "read $_[0] bytes: <$buffer>\n";
161	};	338	};
162		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
163	=item aio_readahead $fh,$offset,$length, $callback	363	=item aio_readahead $fh,$offset,$length, $callback->($retval)
164		364
165	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
166	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>
167	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
168	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
…		…
172	file. The current file offset of the file is left unchanged.	372	file. The current file offset of the file is left unchanged.
173		373
174	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	374	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
175	emulated by simply reading the data, which would have a similar effect.	375	emulated by simply reading the data, which would have a similar effect.
176		376
177	=item aio_stat $fh_or_path, $callback	377	=item aio_stat $fh_or_path, $callback->($status)
178		378
179	=item aio_lstat $fh, $callback	379	=item aio_lstat $fh, $callback->($status)
180		380
181	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
182	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 _>
183	or C<-s _> etc...	383	or C<-s _> etc...
184		384
…		…
194	aio_stat "/etc/passwd", sub {	394	aio_stat "/etc/passwd", sub {
195	$_[0] and die "stat failed: $!";	395	$_[0] and die "stat failed: $!";
196	print "size is ", -s _, "\n";	396	print "size is ", -s _, "\n";
197	};	397	};
198		398
199	=item aio_unlink $pathname, $callback	399	=item aio_unlink $pathname, $callback->($status)
200		400
201	Asynchronously unlink (delete) a file and call the callback with the	401	Asynchronously unlink (delete) a file and call the callback with the
202	result code.	402	result code.
203		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
204	=item aio_rmdir $pathname, $callback	435	=item aio_rmdir $pathname, $callback->($status)
205		436
206	Asynchronously rmdir (delete) a directory and call the callback with the	437	Asynchronously rmdir (delete) a directory and call the callback with the
207	result code.	438	result code.
208		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_load $path, $data, $callback->($status)
		450
		451	This is a composite request that tries to fully load the given file into
		452	memory. Status is the same as with aio_read.
		453
		454	=cut
		455
		456	sub aio_load($$;$) {
		457	aio_block {
		458	my ($path, undef, $cb) = @_;
		459	my $data = \$_[1];
		460
		461	my $pri = aioreq_pri;
		462	my $grp = aio_group $cb;
		463
		464	aioreq_pri $pri;
		465	add $grp aio_open $path, O_RDONLY, 0, sub {
		466	my ($fh) = @_
		467	or return $grp->result (-1);
		468
		469	aioreq_pri $pri;
		470	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		471	$grp->result ($_[0]);
		472	};
		473	};
		474
		475	$grp
		476	}
		477	}
		478
		479	=item aio_copy $srcpath, $dstpath, $callback->($status)
		480
		481	Try to copy the I<file> (directories not supported as either source or
		482	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		483	the C<0> (error) or C<-1> ok.
		484
		485	This is a composite request that it creates the destination file with
		486	mode 0200 and copies the contents of the source file into it using
		487	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		488	uid/gid, in that order.
		489
		490	If an error occurs, the partial destination file will be unlinked, if
		491	possible, except when setting atime, mtime, access mode and uid/gid, where
		492	errors are being ignored.
		493
		494	=cut
		495
		496	sub aio_copy($$;$) {
		497	aio_block {
		498	my ($src, $dst, $cb) = @_;
		499
		500	my $pri = aioreq_pri;
		501	my $grp = aio_group $cb;
		502
		503	aioreq_pri $pri;
		504	add $grp aio_open $src, O_RDONLY, 0, sub {
		505	if (my $src_fh = $_[0]) {
		506	my @stat = stat $src_fh;
		507
		508	aioreq_pri $pri;
		509	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		510	if (my $dst_fh = $_[0]) {
		511	aioreq_pri $pri;
		512	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		513	if ($_[0] == $stat[7]) {
		514	$grp->result (0);
		515	close $src_fh;
		516
		517	# those should not normally block. should. should.
		518	utime $stat[8], $stat[9], $dst;
		519	chmod $stat[2] & 07777, $dst_fh;
		520	chown $stat[4], $stat[5], $dst_fh;
		521	close $dst_fh;
		522	} else {
		523	$grp->result (-1);
		524	close $src_fh;
		525	close $dst_fh;
		526
		527	aioreq $pri;
		528	add $grp aio_unlink $dst;
		529	}
		530	};
		531	} else {
		532	$grp->result (-1);
		533	}
		534	},
		535
		536	} else {
		537	$grp->result (-1);
		538	}
		539	};
		540
		541	$grp
		542	}
		543	}
		544
		545	=item aio_move $srcpath, $dstpath, $callback->($status)
		546
		547	Try to move the I<file> (directories not supported as either source or
		548	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		549	the C<0> (error) or C<-1> ok.
		550
		551	This is a composite request that tries to rename(2) the file first. If
		552	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		553	that is successful, unlinking the C<$srcpath>.
		554
		555	=cut
		556
		557	sub aio_move($$;$) {
		558	aio_block {
		559	my ($src, $dst, $cb) = @_;
		560
		561	my $pri = aioreq_pri;
		562	my $grp = aio_group $cb;
		563
		564	aioreq_pri $pri;
		565	add $grp aio_rename $src, $dst, sub {
		566	if ($_[0] && $! == EXDEV) {
		567	aioreq_pri $pri;
		568	add $grp aio_copy $src, $dst, sub {
		569	$grp->result ($_[0]);
		570
		571	if (!$_[0]) {
		572	aioreq_pri $pri;
		573	add $grp aio_unlink $src;
		574	}
		575	};
		576	} else {
		577	$grp->result ($_[0]);
		578	}
		579	};
		580
		581	$grp
		582	}
		583	}
		584
		585	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		586
		587	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		588	efficiently separate the entries of directory C<$path> into two sets of
		589	names, directories you can recurse into (directories), and ones you cannot
		590	recurse into (everything else, including symlinks to directories).
		591
		592	C<aio_scandir> is a composite request that creates of many sub requests_
		593	C<$maxreq> specifies the maximum number of outstanding aio requests that
		594	this function generates. If it is C<< <= 0 >>, then a suitable default
		595	will be chosen (currently 4).
		596
		597	On error, the callback is called without arguments, otherwise it receives
		598	two array-refs with path-relative entry names.
		599
		600	Example:
		601
		602	aio_scandir $dir, 0, sub {
		603	my ($dirs, $nondirs) = @_;
		604	print "real directories: @$dirs\n";
		605	print "everything else: @$nondirs\n";
		606	};
		607
		608	Implementation notes.
		609
		610	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		611
		612	After reading the directory, the modification time, size etc. of the
		613	directory before and after the readdir is checked, and if they match (and
		614	isn't the current time), the link count will be used to decide how many
		615	entries are directories (if >= 2). Otherwise, no knowledge of the number
		616	of subdirectories will be assumed.
		617
		618	Then entries will be sorted into likely directories (everything without
		619	a non-initial dot currently) and likely non-directories (everything
		620	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		621	likely directories first. If that succeeds, it assumes that the entry
		622	is a directory or a symlink to directory (which will be checked
		623	seperately). This is often faster than stat'ing the entry itself because
		624	filesystems might detect the type of the entry without reading the inode
		625	data (e.g. ext2fs filetype feature).
		626
		627	If the known number of directories (link count - 2) has been reached, the
		628	rest of the entries is assumed to be non-directories.
		629
		630	This only works with certainty on POSIX (= UNIX) filesystems, which
		631	fortunately are the vast majority of filesystems around.
		632
		633	It will also likely work on non-POSIX filesystems with reduced efficiency
		634	as those tend to return 0 or 1 as link counts, which disables the
		635	directory counting heuristic.
		636
		637	=cut
		638
		639	sub aio_scandir($$$) {
		640	aio_block {
		641	my ($path, $maxreq, $cb) = @_;
		642
		643	my $pri = aioreq_pri;
		644
		645	my $grp = aio_group $cb;
		646
		647	$maxreq = 4 if $maxreq <= 0;
		648
		649	# stat once
		650	aioreq_pri $pri;
		651	add $grp aio_stat $path, sub {
		652	return $grp->result () if $_[0];
		653	my $now = time;
		654	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		655
		656	# read the directory entries
		657	aioreq_pri $pri;
		658	add $grp aio_readdir $path, sub {
		659	my $entries = shift
		660	or return $grp->result ();
		661
		662	# stat the dir another time
		663	aioreq_pri $pri;
		664	add $grp aio_stat $path, sub {
		665	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		666
		667	my $ndirs;
		668
		669	# take the slow route if anything looks fishy
		670	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		671	$ndirs = -1;
		672	} else {
		673	# if nlink == 2, we are finished
		674	# on non-posix-fs's, we rely on nlink < 2
		675	$ndirs = (stat _)[3] - 2
		676	or return $grp->result ([], $entries);
		677	}
		678
		679	# sort into likely dirs and likely nondirs
		680	# dirs == files without ".", short entries first
		681	$entries = [map $_->[0],
		682	sort { $b->[1] cmp $a->[1] }
		683	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		684	@$entries];
		685
		686	my (@dirs, @nondirs);
		687
		688	my $statgrp = add $grp aio_group sub {
		689	$grp->result (\@dirs, \@nondirs);
		690	};
		691
		692	limit $statgrp $maxreq;
		693	feed $statgrp sub {
		694	return unless @$entries;
		695	my $entry = pop @$entries;
		696
		697	aioreq_pri $pri;
		698	add $statgrp aio_stat "$path/$entry/.", sub {
		699	if ($_[0] < 0) {
		700	push @nondirs, $entry;
		701	} else {
		702	# need to check for real directory
		703	aioreq_pri $pri;
		704	add $statgrp aio_lstat "$path/$entry", sub {
		705	if (-d _) {
		706	push @dirs, $entry;
		707
		708	unless (--$ndirs) {
		709	push @nondirs, @$entries;
		710	feed $statgrp;
		711	}
		712	} else {
		713	push @nondirs, $entry;
		714	}
		715	}
		716	}
		717	};
		718	};
		719	};
		720	};
		721	};
		722
		723	$grp
		724	}
		725	}
		726
209	=item aio_fsync $fh, $callback	727	=item aio_fsync $fh, $callback->($status)
210		728
211	Asynchronously call fsync on the given filehandle and call the callback	729	Asynchronously call fsync on the given filehandle and call the callback
212	with the fsync result code.	730	with the fsync result code.
213		731
214	=item aio_fdatasync $fh, $callback	732	=item aio_fdatasync $fh, $callback->($status)
215		733
216	Asynchronously call fdatasync on the given filehandle and call the	734	Asynchronously call fdatasync on the given filehandle and call the
217	callback with the fdatasync result code.	735	callback with the fdatasync result code.
218		736
219	If this call isn't available because your OS lacks it or it couldn't be	737	If this call isn't available because your OS lacks it or it couldn't be
220	detected, it will be emulated by calling C<fsync> instead.	738	detected, it will be emulated by calling C<fsync> instead.
221		739
		740	=item aio_group $callback->(...)
		741
		742	This is a very special aio request: Instead of doing something, it is a
		743	container for other aio requests, which is useful if you want to bundle
		744	many requests into a single, composite, request with a definite callback
		745	and the ability to cancel the whole request with its subrequests.
		746
		747	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		748	for more info.
		749
		750	Example:
		751
		752	my $grp = aio_group sub {
		753	print "all stats done\n";
		754	};
		755
		756	add $grp
		757	(aio_stat ...),
		758	(aio_stat ...),
		759	...;
		760
		761	=item aio_nop $callback->()
		762
		763	This is a special request - it does nothing in itself and is only used for
		764	side effects, such as when you want to add a dummy request to a group so
		765	that finishing the requests in the group depends on executing the given
		766	code.
		767
		768	While this request does nothing, it still goes through the execution
		769	phase and still requires a worker thread. Thus, the callback will not
		770	be executed immediately but only after other requests in the queue have
		771	entered their execution phase. This can be used to measure request
		772	latency.
		773
		774	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		775
		776	Mainly used for debugging and benchmarking, this aio request puts one of
		777	the request workers to sleep for the given time.
		778
		779	While it is theoretically handy to have simple I/O scheduling requests
		780	like sleep and file handle readable/writable, the overhead this creates is
		781	immense (it blocks a thread for a long time) so do not use this function
		782	except to put your application under artificial I/O pressure.
		783
222	=back	784	=back
223		785
		786	=head2 IO::AIO::REQ CLASS
		787
		788	All non-aggregate C<aio_*> functions return an object of this class when
		789	called in non-void context.
		790
		791	=over 4
		792
		793	=item cancel $req
		794
		795	Cancels the request, if possible. Has the effect of skipping execution
		796	when entering the B<execute> state and skipping calling the callback when
		797	entering the the B<result> state, but will leave the request otherwise
		798	untouched. That means that requests that currently execute will not be
		799	stopped and resources held by the request will not be freed prematurely.
		800
		801	=item cb $req $callback->(...)
		802
		803	Replace (or simply set) the callback registered to the request.
		804
		805	=back
		806
		807	=head2 IO::AIO::GRP CLASS
		808
		809	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		810	objects of this class, too.
		811
		812	A IO::AIO::GRP object is a special request that can contain multiple other
		813	aio requests.
		814
		815	You create one by calling the C<aio_group> constructing function with a
		816	callback that will be called when all contained requests have entered the
		817	C<done> state:
		818
		819	my $grp = aio_group sub {
		820	print "all requests are done\n";
		821	};
		822
		823	You add requests by calling the C<add> method with one or more
		824	C<IO::AIO::REQ> objects:
		825
		826	$grp->add (aio_unlink "...");
		827
		828	add $grp aio_stat "...", sub {
		829	$_[0] or return $grp->result ("error");
		830
		831	# add another request dynamically, if first succeeded
		832	add $grp aio_open "...", sub {
		833	$grp->result ("ok");
		834	};
		835	};
		836
		837	This makes it very easy to create composite requests (see the source of
		838	C<aio_move> for an application) that work and feel like simple requests.
		839
		840	=over 4
		841
		842	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		843	C<IO::AIO::poll_cb>, just like any other request.
		844
		845	=item * They can be canceled like any other request. Canceling will cancel not
		846	only the request itself, but also all requests it contains.
		847
		848	=item * They can also can also be added to other IO::AIO::GRP objects.
		849
		850	=item * You must not add requests to a group from within the group callback (or
		851	any later time).
		852
		853	=back
		854
		855	Their lifetime, simplified, looks like this: when they are empty, they
		856	will finish very quickly. If they contain only requests that are in the
		857	C<done> state, they will also finish. Otherwise they will continue to
		858	exist.
		859
		860	That means after creating a group you have some time to add requests. And
		861	in the callbacks of those requests, you can add further requests to the
		862	group. And only when all those requests have finished will the the group
		863	itself finish.
		864
		865	=over 4
		866
		867	=item add $grp ...
		868
		869	=item $grp->add (...)
		870
		871	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		872	be added, including other groups, as long as you do not create circular
		873	dependencies.
		874
		875	Returns all its arguments.
		876
		877	=item $grp->cancel_subs
		878
		879	Cancel all subrequests and clears any feeder, but not the group request
		880	itself. Useful when you queued a lot of events but got a result early.
		881
		882	=item $grp->result (...)
		883
		884	Set the result value(s) that will be passed to the group callback when all
		885	subrequests have finished and set thre groups errno to the current value
		886	of errno (just like calling C<errno> without an error number). By default,
		887	no argument will be passed and errno is zero.
		888
		889	=item $grp->errno ([$errno])
		890
		891	Sets the group errno value to C<$errno>, or the current value of errno
		892	when the argument is missing.
		893
		894	Every aio request has an associated errno value that is restored when
		895	the callback is invoked. This method lets you change this value from its
		896	default (0).
		897
		898	Calling C<result> will also set errno, so make sure you either set C<$!>
		899	before the call to C<result>, or call c<errno> after it.
		900
		901	=item feed $grp $callback->($grp)
		902
		903	Sets a feeder/generator on this group: every group can have an attached
		904	generator that generates requests if idle. The idea behind this is that,
		905	although you could just queue as many requests as you want in a group,
		906	this might starve other requests for a potentially long time. For
		907	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		908	requests, delaying any later requests for a long time.
		909
		910	To avoid this, and allow incremental generation of requests, you can
		911	instead a group and set a feeder on it that generates those requests. The
		912	feed callback will be called whenever there are few enough (see C<limit>,
		913	below) requests active in the group itself and is expected to queue more
		914	requests.
		915
		916	The feed callback can queue as many requests as it likes (i.e. C<add> does
		917	not impose any limits).
		918
		919	If the feed does not queue more requests when called, it will be
		920	automatically removed from the group.
		921
		922	If the feed limit is C<0>, it will be set to C<2> automatically.
		923
		924	Example:
		925
		926	# stat all files in @files, but only ever use four aio requests concurrently:
		927
		928	my $grp = aio_group sub { print "finished\n" };
		929	limit $grp 4;
		930	feed $grp sub {
		931	my $file = pop @files
		932	or return;
		933
		934	add $grp aio_stat $file, sub { ... };
		935	};
		936
		937	=item limit $grp $num
		938
		939	Sets the feeder limit for the group: The feeder will be called whenever
		940	the group contains less than this many requests.
		941
		942	Setting the limit to C<0> will pause the feeding process.
		943
		944	=back
		945
224	=head2 SUPPORT FUNCTIONS	946	=head2 SUPPORT FUNCTIONS
		947
		948	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
225		949
226	=over 4	950	=over 4
227		951
228	=item $fileno = IO::AIO::poll_fileno	952	=item $fileno = IO::AIO::poll_fileno
229		953
…		…
234		958
235	See C<poll_cb> for an example.	959	See C<poll_cb> for an example.
236		960
237	=item IO::AIO::poll_cb	961	=item IO::AIO::poll_cb
238		962
239	Process all outstanding events on the result pipe. You have to call this	963	Process some outstanding events on the result pipe. You have to call this
240	regularly. Returns the number of events processed. Returns immediately	964	regularly. Returns the number of events processed. Returns immediately
241	when no events are outstanding.	965	when no events are outstanding. The amount of events processed depends on
		966	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		967
		968	If not all requests were processed for whatever reason, the filehandle
		969	will still be ready when C<poll_cb> returns.
242		970
243	Example: Install an Event watcher that automatically calls	971	Example: Install an Event watcher that automatically calls
244	IO::AIO::poll_cb with high priority:	972	IO::AIO::poll_cb with high priority:
245		973
246	Event->io (fd => IO::AIO::poll_fileno,	974	Event->io (fd => IO::AIO::poll_fileno,
247	poll => 'r', async => 1,	975	poll => 'r', async => 1,
248	cb => \&IO::AIO::poll_cb);	976	cb => \&IO::AIO::poll_cb);
249		977
		978	=item IO::AIO::max_poll_reqs $nreqs
		979
		980	=item IO::AIO::max_poll_time $seconds
		981
		982	These set the maximum number of requests (default C<0>, meaning infinity)
		983	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		984	the maximum amount of time (default C<0>, meaning infinity) spent in
		985	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		986	of time C<poll_cb> is allowed to use).
		987
		988	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		989	syscall per request processed, which is not normally a problem unless your
		990	callbacks are really really fast or your OS is really really slow (I am
		991	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		992
		993	Setting these is useful if you want to ensure some level of
		994	interactiveness when perl is not fast enough to process all requests in
		995	time.
		996
		997	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		998
		999	Example: Install an Event watcher that automatically calls
		1000	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1001	program get the CPU sometimes even under high AIO load.
		1002
		1003	# try not to spend much more than 0.1s in poll_cb
		1004	IO::AIO::max_poll_time 0.1;
		1005
		1006	# use a low priority so other tasks have priority
		1007	Event->io (fd => IO::AIO::poll_fileno,
		1008	poll => 'r', nice => 1,
		1009	cb => &IO::AIO::poll_cb);
		1010
250	=item IO::AIO::poll_wait	1011	=item IO::AIO::poll_wait
251		1012
		1013	If there are any outstanding requests and none of them in the result
252	Wait till the result filehandle becomes ready for reading (simply does a	1014	phase, wait till the result filehandle becomes ready for reading (simply
253	C<select> on the filehandle. This is useful if you want to synchronously wait	1015	does a C<select> on the filehandle. This is useful if you want to
254	for some requests to finish).	1016	synchronously wait for some requests to finish).
255		1017
256	See C<nreqs> for an example.	1018	See C<nreqs> for an example.
257		1019
		1020	=item IO::AIO::poll
		1021
		1022	Waits until some requests have been handled.
		1023
		1024	Returns the number of requests processed, but is otherwise strictly
		1025	equivalent to:
		1026
		1027	IO::AIO::poll_wait, IO::AIO::poll_cb
		1028
258	=item IO::AIO::nreqs	1029	=item IO::AIO::flush
259		1030
260	Returns the number of requests currently outstanding (i.e. for which their	1031	Wait till all outstanding AIO requests have been handled.
261	callback has not been invoked yet).
262		1032
263	Example: wait till there are no outstanding requests anymore:	1033	Strictly equivalent to:
264		1034
265	IO::AIO::poll_wait, IO::AIO::poll_cb	1035	IO::AIO::poll_wait, IO::AIO::poll_cb
266	while IO::AIO::nreqs;	1036	while IO::AIO::nreqs;
267		1037
		1038	=head3 CONTROLLING THE NUMBER OF THREADS
		1039
		1040	=item IO::AIO::min_parallel $nthreads
		1041
		1042	Set the minimum number of AIO threads to C<$nthreads>. The current
		1043	default is C<8>, which means eight asynchronous operations can execute
		1044	concurrently at any one time (the number of outstanding requests,
		1045	however, is unlimited).
		1046
		1047	IO::AIO starts threads only on demand, when an AIO request is queued and
		1048	no free thread exists. Please note that queueing up a hundred requests can
		1049	create demand for a hundred threads, even if it turns out that everything
		1050	is in the cache and could have been processed faster by a single thread.
		1051
		1052	It is recommended to keep the number of threads relatively low, as some
		1053	Linux kernel versions will scale negatively with the number of threads
		1054	(higher parallelity => MUCH higher latency). With current Linux 2.6
		1055	versions, 4-32 threads should be fine.
		1056
		1057	Under most circumstances you don't need to call this function, as the
		1058	module selects a default that is suitable for low to moderate load.
		1059
		1060	=item IO::AIO::max_parallel $nthreads
		1061
		1062	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		1063	specified number of threads are currently running, this function kills
		1064	them. This function blocks until the limit is reached.
		1065
		1066	While C<$nthreads> are zero, aio requests get queued but not executed
		1067	until the number of threads has been increased again.
		1068
		1069	This module automatically runs C<max_parallel 0> at program end, to ensure
		1070	that all threads are killed and that there are no outstanding requests.
		1071
		1072	Under normal circumstances you don't need to call this function.
		1073
		1074	=item IO::AIO::max_idle $nthreads
		1075
		1076	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1077	threads that did not get a request to process within 10 seconds). That
		1078	means if a thread becomes idle while C<$nthreads> other threads are also
		1079	idle, it will free its resources and exit.
		1080
		1081	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1082	to allow for extremely high load situations, but want to free resources
		1083	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1084
		1085	The default is probably ok in most situations, especially if thread
		1086	creation is fast. If thread creation is very slow on your system you might
		1087	want to use larger values.
		1088
		1089	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1090
		1091	This is a very bad function to use in interactive programs because it
		1092	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1093	use an C<aio_group> together with a feed callback.
		1094
		1095	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		1096	to queue up more than this number of requests, the next call to the
		1097	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1098	function will block until the limit is no longer exceeded.
		1099
		1100	The default value is very large, so there is no practical limit on the
		1101	number of outstanding requests.
		1102
		1103	You can still queue as many requests as you want. Therefore,
		1104	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1105	as a stop gap to shield against fatal memory overflow (with large values).
		1106
		1107	=head3 STATISTICAL INFORMATION
		1108
268	=item IO::AIO::flush	1109	=item IO::AIO::nreqs
269		1110
270	Wait till all outstanding AIO requests have been handled.	1111	Returns the number of requests currently in the ready, execute or pending
		1112	states (i.e. for which their callback has not been invoked yet).
271		1113
272	Strictly equivalent to:	1114	Example: wait till there are no outstanding requests anymore:
273		1115
274	IO::AIO::poll_wait, IO::AIO::poll_cb	1116	IO::AIO::poll_wait, IO::AIO::poll_cb
275	while IO::AIO::nreqs;	1117	while IO::AIO::nreqs;
276		1118
		1119	=item IO::AIO::nready
		1120
		1121	Returns the number of requests currently in the ready state (not yet
		1122	executed).
		1123
277	=item IO::AIO::poll	1124	=item IO::AIO::npending
278		1125
279	Waits until some requests have been handled.	1126	Returns the number of requests currently in the pending state (executed,
280		1127	but not yet processed by poll_cb).
281	Strictly equivalent to:
282
283	IO::AIO::poll_wait, IO::AIO::poll_cb
284	if IO::AIO::nreqs;
285
286	=item IO::AIO::min_parallel $nthreads
287
288	Set the minimum number of AIO threads to C<$nthreads>. The default is
289	C<1>, which means a single asynchronous operation can be done at one time
290	(the number of outstanding operations, however, is unlimited).
291
292	It is recommended to keep the number of threads low, as some Linux
293	kernel versions will scale negatively with the number of threads (higher
294	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
295	threads should be fine.
296
297	Under normal circumstances you don't need to call this function, as this
298	module automatically starts some threads (the exact number might change,
299	and is currently 4).
300
301	=item IO::AIO::max_parallel $nthreads
302
303	Sets the maximum number of AIO threads to C<$nthreads>. If more than
304	the specified number of threads are currently running, kill them. This
305	function blocks until the limit is reached.
306
307	This module automatically runs C<max_parallel 0> at program end, to ensure
308	that all threads are killed and that there are no outstanding requests.
309
310	Under normal circumstances you don't need to call this function.
311
312	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
313
314	Sets the maximum number of outstanding requests to C<$nreqs>. If you
315	try to queue up more than this number of requests, the caller will block until
316	some requests have been handled.
317
318	The default is very large, so normally there is no practical limit. If you
319	queue up many requests in a loop it it often improves speed if you set
320	this to a relatively low number, such as C<100>.
321
322	Under normal circumstances you don't need to call this function.
323		1128
324	=back	1129	=back
325		1130
326	=cut	1131	=cut
327		1132
…		…
339	or return undef;	1144	or return undef;
340		1145
341	*$sym	1146	*$sym
342	}	1147	}
343		1148
344	min_parallel 4;	1149	min_parallel 8;
345		1150
346	END {	1151	END { flush }
347	max_parallel 0;
348	}
349		1152
350	1;	1153	1;
351		1154
352	=head2 FORK BEHAVIOUR	1155	=head2 FORK BEHAVIOUR
353		1156
354	Before the fork IO::AIO first handles all outstanding requests - if other	1157	This module should do "the right thing" when the process using it forks:
355	threads add requests during this period, this time is prolonged. It then	1158
356	enters a quiescent state where no requests can be added in other threads	1159	Before the fork, IO::AIO enters a quiescent state where no requests
357	and no results will be processed. After the fork the parent simply leaves	1160	can be added in other threads and no results will be processed. After
358	the quiescent state and continues request processing, while the child	1161	the fork the parent simply leaves the quiescent state and continues
359	starts the same number of threads as were in use by the parent.	1162	request/result processing, while the child frees the request/result queue
		1163	(so that the requests started before the fork will only be handled in the
		1164	parent). Threads will be started on demand until the limit set in the
		1165	parent process has been reached again.
		1166
		1167	In short: the parent will, after a short pause, continue as if fork had
		1168	not been called, while the child will act as if IO::AIO has not been used
		1169	yet.
		1170
		1171	=head2 MEMORY USAGE
		1172
		1173	Per-request usage:
		1174
		1175	Each aio request uses - depending on your architecture - around 100-200
		1176	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1177	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1178	scalars and other data passed into aio requests will also be locked and
		1179	will consume memory till the request has entered the done state.
		1180
		1181	This is now awfully much, so queuing lots of requests is not usually a
		1182	problem.
		1183
		1184	Per-thread usage:
		1185
		1186	In the execution phase, some aio requests require more memory for
		1187	temporary buffers, and each thread requires a stack and other data
		1188	structures (usually around 16k-128k, depending on the OS).
		1189
		1190	=head1 KNOWN BUGS
		1191
		1192	Known bugs will be fixed in the next release.
360		1193
361	=head1 SEE ALSO	1194	=head1 SEE ALSO
362		1195
363	L<Coro>, L<Linux::AIO>.	1196	L<Coro::AIO>.
364		1197
365	=head1 AUTHOR	1198	=head1 AUTHOR
366		1199
367	Marc Lehmann <schmorp@schmorp.de>	1200	Marc Lehmann <schmorp@schmorp.de>
368	http://home.schmorp.de/	1201	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.30 by root, Wed Aug 17 04:47:38 2005 UTC vs. Revision 1.98 by root, Sun Dec 31 17:07:32 2006 UTC

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Revision 1.30 by root, Wed Aug 17 04:47:38 2005 UTC vs.
Revision 1.98 by root, Sun Dec 31 17:07:32 2006 UTC