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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.38 by root, Sun Aug 28 10:51:33 2005 UTC vs.
Revision 1.106 by root, Fri Jun 1 05:51:21 2007 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 = 1.6;	195	our $VERSION = '2.4';
69		196
70	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close stat	197	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71	aio_aio_lstat aio_unlink aio_rmdir aio_readdir aio_symlink	198	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72	aio_fsync aio_fdatasync aio_readahead);	199	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
73	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	200	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
74	max_outstanding nreqs);	201	aio_chown aio_chmod aio_utime);
		202	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		203	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		204	min_parallel max_parallel max_idle
		205	nreqs nready npending nthreads
		206	max_poll_time max_poll_reqs);
		207
		208	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
75		209
76	require XSLoader;	210	require XSLoader;
77	XSLoader::load IO::AIO, $VERSION;	211	XSLoader::load ("IO::AIO", $VERSION);
78	}	212	}
79		213
80	=head1 FUNCTIONS	214	=head1 FUNCTIONS
81		215
82	=head2 AIO FUNCTIONS	216	=head2 AIO REQUEST FUNCTIONS
83		217
84	All the C<aio_*> calls are more or less thin wrappers around the syscall	218	All the C<aio_*> calls are more or less thin wrappers around the syscall
85	with the same name (sans C<aio_>). The arguments are similar or identical,	219	with the same name (sans C<aio_>). The arguments are similar or identical,
86	and they all accept an additional (and optional) C<$callback> argument	220	and they all accept an additional (and optional) C<$callback> argument
87	which must be a code reference. This code reference will get called with	221	which must be a code reference. This code reference will get called with
…		…
90	syscall has been executed asynchronously.	224	syscall has been executed asynchronously.
91		225
92	All functions expecting a filehandle keep a copy of the filehandle	226	All functions expecting a filehandle keep a copy of the filehandle
93	internally until the request has finished.	227	internally until the request has finished.
94		228
		229	All functions return request objects of type L<IO::AIO::REQ> that allow
		230	further manipulation of those requests while they are in-flight.
		231
95	The pathnames you pass to these routines I<must> be absolute and	232	The pathnames you pass to these routines I<must> be absolute and
96	encoded in byte form. The reason for the former is that at the time the	233	encoded as octets. The reason for the former is that at the time the
97	request is being executed, the current working directory could have	234	request is being executed, the current working directory could have
98	changed. Alternatively, you can make sure that you never change the	235	changed. Alternatively, you can make sure that you never change the
99	current working directory.	236	current working directory anywhere in the program and then use relative
		237	paths.
100		238
101	To encode pathnames to byte form, either make sure you either: a)	239	To encode pathnames as octets, either make sure you either: a) always pass
102	always pass in filenames you got from outside (command line, readdir	240	in filenames you got from outside (command line, readdir etc.) without
103	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	241	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
104	your pathnames to the locale (or other) encoding in effect in the user	242	your pathnames to the locale (or other) encoding in effect in the user
105	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	243	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
106	use something else.	244	use something else to ensure your scalar has the correct contents.
		245
		246	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		247	handles correctly wether it is set or not.
107		248
108	=over 4	249	=over 4
109		250
		251	=item $prev_pri = aioreq_pri [$pri]
		252
		253	Returns the priority value that would be used for the next request and, if
		254	C<$pri> is given, sets the priority for the next aio request.
		255
		256	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		257	and C<4>, respectively. Requests with higher priority will be serviced
		258	first.
		259
		260	The priority will be reset to C<0> after each call to one of the C<aio_*>
		261	functions.
		262
		263	Example: open a file with low priority, then read something from it with
		264	higher priority so the read request is serviced before other low priority
		265	open requests (potentially spamming the cache):
		266
		267	aioreq_pri -3;
		268	aio_open ..., sub {
		269	return unless $_[0];
		270
		271	aioreq_pri -2;
		272	aio_read $_[0], ..., sub {
		273	...
		274	};
		275	};
		276
		277
		278	=item aioreq_nice $pri_adjust
		279
		280	Similar to C<aioreq_pri>, but subtracts the given value from the current
		281	priority, so the effect is cumulative.
		282
		283
110	=item aio_open $pathname, $flags, $mode, $callback	284	=item aio_open $pathname, $flags, $mode, $callback->($fh)
111		285
112	Asynchronously open or create a file and call the callback with a newly	286	Asynchronously open or create a file and call the callback with a newly
113	created filehandle for the file.	287	created filehandle for the file.
114		288
115	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	289	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
119	list. They are the same as used by C<sysopen>.	293	list. They are the same as used by C<sysopen>.
120		294
121	Likewise, C<$mode> specifies the mode of the newly created file, if it	295	Likewise, C<$mode> specifies the mode of the newly created file, if it
122	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	296	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
123	except that it is mandatory (i.e. use C<0> if you don't create new files,	297	except that it is mandatory (i.e. use C<0> if you don't create new files,
124	and C<0666> or C<0777> if you do).	298	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		299	by the umask in effect then the request is being executed, so better never
		300	change the umask.
125		301
126	Example:	302	Example:
127		303
128	aio_open "/etc/passwd", O_RDONLY, 0, sub {	304	aio_open "/etc/passwd", O_RDONLY, 0, sub {
129	if ($_[0]) {	305	if ($_[0]) {
…		…
132	} else {	308	} else {
133	die "open failed: $!\n";	309	die "open failed: $!\n";
134	}	310	}
135	};	311	};
136		312
		313
137	=item aio_close $fh, $callback	314	=item aio_close $fh, $callback->($status)
138		315
139	Asynchronously close a file and call the callback with the result	316	Asynchronously close a file and call the callback with the result
140	code. I<WARNING:> although accepted, you should not pass in a perl	317	code. I<WARNING:> although accepted, you should not pass in a perl
141	filehandle here, as perl will likely close the file descriptor another	318	filehandle here, as perl will likely close the file descriptor another
142	time when the filehandle is destroyed. Normally, you can safely call perls	319	time when the filehandle is destroyed. Normally, you can safely call perls
143	C<close> or just let filehandles go out of scope.	320	C<close> or just let filehandles go out of scope.
144		321
145	This is supposed to be a bug in the API, so that might change. It's	322	This is supposed to be a bug in the API, so that might change. It's
146	therefore best to avoid this function.	323	therefore best to avoid this function.
147		324
		325
148	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	326	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149		327
150	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	328	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
151		329
152	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	330	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
153	into the scalar given by C<data> and offset C<dataoffset> and calls the	331	into the scalar given by C<data> and offset C<dataoffset> and calls the
154	callback without the actual number of bytes read (or -1 on error, just	332	callback without the actual number of bytes read (or -1 on error, just
155	like the syscall).	333	like the syscall).
…		…
164	aio_read $fh, 7, 15, $buffer, 0, sub {	342	aio_read $fh, 7, 15, $buffer, 0, sub {
165	$_[0] > 0 or die "read error: $!";	343	$_[0] > 0 or die "read error: $!";
166	print "read $_[0] bytes: <$buffer>\n";	344	print "read $_[0] bytes: <$buffer>\n";
167	};	345	};
168		346
		347
169	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback	348	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
170		349
171	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	350	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
172	reading at byte offset C<$in_offset>, and starts writing at the current	351	reading at byte offset C<$in_offset>, and starts writing at the current
173	file offset of C<$out_fh>. Because of that, it is not safe to issue more	352	file offset of C<$out_fh>. Because of that, it is not safe to issue more
174	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	353	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
…		…
187	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	366	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
188	provides the number of bytes written to C<$out_fh>. Only if the result	367	provides the number of bytes written to C<$out_fh>. Only if the result
189	value equals C<$length> one can assume that C<$length> bytes have been	368	value equals C<$length> one can assume that C<$length> bytes have been
190	read.	369	read.
191		370
		371
192	=item aio_readahead $fh,$offset,$length, $callback	372	=item aio_readahead $fh,$offset,$length, $callback->($retval)
193		373
194	C<aio_readahead> populates the page cache with data from a file so that	374	C<aio_readahead> populates the page cache with data from a file so that
195	subsequent reads from that file will not block on disk I/O. The C<$offset>	375	subsequent reads from that file will not block on disk I/O. The C<$offset>
196	argument specifies the starting point from which data is to be read and	376	argument specifies the starting point from which data is to be read and
197	C<$length> specifies the number of bytes to be read. I/O is performed in	377	C<$length> specifies the number of bytes to be read. I/O is performed in
…		…
201	file. The current file offset of the file is left unchanged.	381	file. The current file offset of the file is left unchanged.
202		382
203	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	383	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
204	emulated by simply reading the data, which would have a similar effect.	384	emulated by simply reading the data, which would have a similar effect.
205		385
		386
206	=item aio_stat $fh_or_path, $callback	387	=item aio_stat $fh_or_path, $callback->($status)
207		388
208	=item aio_lstat $fh, $callback	389	=item aio_lstat $fh, $callback->($status)
209		390
210	Works like perl's C<stat> or C<lstat> in void context. The callback will	391	Works like perl's C<stat> or C<lstat> in void context. The callback will
211	be called after the stat and the results will be available using C<stat _>	392	be called after the stat and the results will be available using C<stat _>
212	or C<-s _> etc...	393	or C<-s _> etc...
213		394
…		…
223	aio_stat "/etc/passwd", sub {	404	aio_stat "/etc/passwd", sub {
224	$_[0] and die "stat failed: $!";	405	$_[0] and die "stat failed: $!";
225	print "size is ", -s _, "\n";	406	print "size is ", -s _, "\n";
226	};	407	};
227		408
		409
		410	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		411
		412	Works like perl's C<utime> function (including the special case of $atime
		413	and $mtime being undef). Fractional times are supported if the underlying
		414	syscalls support them.
		415
		416	When called with a pathname, uses utimes(2) if available, otherwise
		417	utime(2). If called on a file descriptor, uses futimes(2) if available,
		418	otherwise returns ENOSYS, so this is not portable.
		419
		420	Examples:
		421
		422	# set atime and mtime to current time:
		423	aio_utime "path", undef, undef;
		424	# set atime to current time and mtime to beginning of the epoch:
		425	aio_utime "path", time, undef; # undef==0
		426
		427
		428	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		429
		430	Works like perl's C<chown> function, except that C<undef> for either $uid
		431	or $gid is being interpreted as "do not change" (but -1 can also be used).
		432
		433	Examples:
		434
		435	# same as "chown root path" in the shell:
		436	aio_chown "path", 0, -1;
		437	# same as above:
		438	aio_chown "path", 0, undef;
		439
		440
		441	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		442
		443	Works like perl's C<chmod> function.
		444
		445
228	=item aio_unlink $pathname, $callback	446	=item aio_unlink $pathname, $callback->($status)
229		447
230	Asynchronously unlink (delete) a file and call the callback with the	448	Asynchronously unlink (delete) a file and call the callback with the
231	result code.	449	result code.
232		450
		451
		452	=item aio_mknod $path, $mode, $dev, $callback->($status)
		453
		454	[EXPERIMENTAL]
		455
		456	Asynchronously create a device node (or fifo). See mknod(2).
		457
		458	The only (POSIX-) portable way of calling this function is:
		459
		460	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		461
		462
		463	=item aio_link $srcpath, $dstpath, $callback->($status)
		464
		465	Asynchronously create a new link to the existing object at C<$srcpath> at
		466	the path C<$dstpath> and call the callback with the result code.
		467
		468
		469	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		470
		471	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		472	the path C<$dstpath> and call the callback with the result code.
		473
		474
		475	=item aio_readlink $path, $callback->($link)
		476
		477	Asynchronously read the symlink specified by C<$path> and pass it to
		478	the callback. If an error occurs, nothing or undef gets passed to the
		479	callback.
		480
		481
		482	=item aio_rename $srcpath, $dstpath, $callback->($status)
		483
		484	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		485	rename(2) and call the callback with the result code.
		486
		487
		488	=item aio_mkdir $pathname, $mode, $callback->($status)
		489
		490	Asynchronously mkdir (create) a directory and call the callback with
		491	the result code. C<$mode> will be modified by the umask at the time the
		492	request is executed, so do not change your umask.
		493
		494
233	=item aio_rmdir $pathname, $callback	495	=item aio_rmdir $pathname, $callback->($status)
234		496
235	Asynchronously rmdir (delete) a directory and call the callback with the	497	Asynchronously rmdir (delete) a directory and call the callback with the
236	result code.	498	result code.
237		499
		500
238	=item aio_readdir $pathname $callback	501	=item aio_readdir $pathname, $callback->($entries)
239		502
240	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	503	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
241	directory (i.e. opendir + readdir + closedir). The entries will not be	504	directory (i.e. opendir + readdir + closedir). The entries will not be
242	sorted, and will B<NOT> include the C<.> and C<..> entries.	505	sorted, and will B<NOT> include the C<.> and C<..> entries.
243		506
244	The callback a single argument which is either C<undef> or an array-ref	507	The callback a single argument which is either C<undef> or an array-ref
245	with the filenames.	508	with the filenames.
246		509
		510
		511	=item aio_load $path, $data, $callback->($status)
		512
		513	This is a composite request that tries to fully load the given file into
		514	memory. Status is the same as with aio_read.
		515
		516	=cut
		517
		518	sub aio_load($$;$) {
		519	aio_block {
		520	my ($path, undef, $cb) = @_;
		521	my $data = \$_[1];
		522
		523	my $pri = aioreq_pri;
		524	my $grp = aio_group $cb;
		525
		526	aioreq_pri $pri;
		527	add $grp aio_open $path, O_RDONLY, 0, sub {
		528	my $fh = shift
		529	or return $grp->result (-1);
		530
		531	aioreq_pri $pri;
		532	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		533	$grp->result ($_[0]);
		534	};
		535	};
		536
		537	$grp
		538	}
		539	}
		540
		541	=item aio_copy $srcpath, $dstpath, $callback->($status)
		542
		543	Try to copy the I<file> (directories not supported as either source or
		544	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		545	the C<0> (error) or C<-1> ok.
		546
		547	This is a composite request that it creates the destination file with
		548	mode 0200 and copies the contents of the source file into it using
		549	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		550	uid/gid, in that order.
		551
		552	If an error occurs, the partial destination file will be unlinked, if
		553	possible, except when setting atime, mtime, access mode and uid/gid, where
		554	errors are being ignored.
		555
		556	=cut
		557
		558	sub aio_copy($$;$) {
		559	aio_block {
		560	my ($src, $dst, $cb) = @_;
		561
		562	my $pri = aioreq_pri;
		563	my $grp = aio_group $cb;
		564
		565	aioreq_pri $pri;
		566	add $grp aio_open $src, O_RDONLY, 0, sub {
		567	if (my $src_fh = $_[0]) {
		568	my @stat = stat $src_fh;
		569
		570	aioreq_pri $pri;
		571	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		572	if (my $dst_fh = $_[0]) {
		573	aioreq_pri $pri;
		574	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		575	if ($_[0] == $stat[7]) {
		576	$grp->result (0);
		577	close $src_fh;
		578
		579	# those should not normally block. should. should.
		580	utime $stat[8], $stat[9], $dst;
		581	chmod $stat[2] & 07777, $dst_fh;
		582	chown $stat[4], $stat[5], $dst_fh;
		583	close $dst_fh;
		584	} else {
		585	$grp->result (-1);
		586	close $src_fh;
		587	close $dst_fh;
		588
		589	aioreq $pri;
		590	add $grp aio_unlink $dst;
		591	}
		592	};
		593	} else {
		594	$grp->result (-1);
		595	}
		596	},
		597
		598	} else {
		599	$grp->result (-1);
		600	}
		601	};
		602
		603	$grp
		604	}
		605	}
		606
		607	=item aio_move $srcpath, $dstpath, $callback->($status)
		608
		609	Try to move the I<file> (directories not supported as either source or
		610	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		611	the C<0> (error) or C<-1> ok.
		612
		613	This is a composite request that tries to rename(2) the file first. If
		614	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		615	that is successful, unlinking the C<$srcpath>.
		616
		617	=cut
		618
		619	sub aio_move($$;$) {
		620	aio_block {
		621	my ($src, $dst, $cb) = @_;
		622
		623	my $pri = aioreq_pri;
		624	my $grp = aio_group $cb;
		625
		626	aioreq_pri $pri;
		627	add $grp aio_rename $src, $dst, sub {
		628	if ($_[0] && $! == EXDEV) {
		629	aioreq_pri $pri;
		630	add $grp aio_copy $src, $dst, sub {
		631	$grp->result ($_[0]);
		632
		633	if (!$_[0]) {
		634	aioreq_pri $pri;
		635	add $grp aio_unlink $src;
		636	}
		637	};
		638	} else {
		639	$grp->result ($_[0]);
		640	}
		641	};
		642
		643	$grp
		644	}
		645	}
		646
		647	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		648
		649	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		650	efficiently separate the entries of directory C<$path> into two sets of
		651	names, directories you can recurse into (directories), and ones you cannot
		652	recurse into (everything else, including symlinks to directories).
		653
		654	C<aio_scandir> is a composite request that creates of many sub requests_
		655	C<$maxreq> specifies the maximum number of outstanding aio requests that
		656	this function generates. If it is C<< <= 0 >>, then a suitable default
		657	will be chosen (currently 4).
		658
		659	On error, the callback is called without arguments, otherwise it receives
		660	two array-refs with path-relative entry names.
		661
		662	Example:
		663
		664	aio_scandir $dir, 0, sub {
		665	my ($dirs, $nondirs) = @_;
		666	print "real directories: @$dirs\n";
		667	print "everything else: @$nondirs\n";
		668	};
		669
		670	Implementation notes.
		671
		672	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		673
		674	After reading the directory, the modification time, size etc. of the
		675	directory before and after the readdir is checked, and if they match (and
		676	isn't the current time), the link count will be used to decide how many
		677	entries are directories (if >= 2). Otherwise, no knowledge of the number
		678	of subdirectories will be assumed.
		679
		680	Then entries will be sorted into likely directories (everything without
		681	a non-initial dot currently) and likely non-directories (everything
		682	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		683	likely directories first. If that succeeds, it assumes that the entry
		684	is a directory or a symlink to directory (which will be checked
		685	seperately). This is often faster than stat'ing the entry itself because
		686	filesystems might detect the type of the entry without reading the inode
		687	data (e.g. ext2fs filetype feature).
		688
		689	If the known number of directories (link count - 2) has been reached, the
		690	rest of the entries is assumed to be non-directories.
		691
		692	This only works with certainty on POSIX (= UNIX) filesystems, which
		693	fortunately are the vast majority of filesystems around.
		694
		695	It will also likely work on non-POSIX filesystems with reduced efficiency
		696	as those tend to return 0 or 1 as link counts, which disables the
		697	directory counting heuristic.
		698
		699	=cut
		700
		701	sub aio_scandir($$;$) {
		702	aio_block {
		703	my ($path, $maxreq, $cb) = @_;
		704
		705	my $pri = aioreq_pri;
		706
		707	my $grp = aio_group $cb;
		708
		709	$maxreq = 4 if $maxreq <= 0;
		710
		711	# stat once
		712	aioreq_pri $pri;
		713	add $grp aio_stat $path, sub {
		714	return $grp->result () if $_[0];
		715	my $now = time;
		716	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		717
		718	# read the directory entries
		719	aioreq_pri $pri;
		720	add $grp aio_readdir $path, sub {
		721	my $entries = shift
		722	or return $grp->result ();
		723
		724	# stat the dir another time
		725	aioreq_pri $pri;
		726	add $grp aio_stat $path, sub {
		727	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		728
		729	my $ndirs;
		730
		731	# take the slow route if anything looks fishy
		732	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		733	$ndirs = -1;
		734	} else {
		735	# if nlink == 2, we are finished
		736	# on non-posix-fs's, we rely on nlink < 2
		737	$ndirs = (stat _)[3] - 2
		738	or return $grp->result ([], $entries);
		739	}
		740
		741	# sort into likely dirs and likely nondirs
		742	# dirs == files without ".", short entries first
		743	$entries = [map $_->[0],
		744	sort { $b->[1] cmp $a->[1] }
		745	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		746	@$entries];
		747
		748	my (@dirs, @nondirs);
		749
		750	my $statgrp = add $grp aio_group sub {
		751	$grp->result (\@dirs, \@nondirs);
		752	};
		753
		754	limit $statgrp $maxreq;
		755	feed $statgrp sub {
		756	return unless @$entries;
		757	my $entry = pop @$entries;
		758
		759	aioreq_pri $pri;
		760	add $statgrp aio_stat "$path/$entry/.", sub {
		761	if ($_[0] < 0) {
		762	push @nondirs, $entry;
		763	} else {
		764	# need to check for real directory
		765	aioreq_pri $pri;
		766	add $statgrp aio_lstat "$path/$entry", sub {
		767	if (-d _) {
		768	push @dirs, $entry;
		769
		770	unless (--$ndirs) {
		771	push @nondirs, @$entries;
		772	feed $statgrp;
		773	}
		774	} else {
		775	push @nondirs, $entry;
		776	}
		777	}
		778	}
		779	};
		780	};
		781	};
		782	};
		783	};
		784
		785	$grp
		786	}
		787	}
		788
		789	=item aio_rmtree $path, $callback->($status)
		790
		791	Delete a directory tree starting (and including) C<$path>, return the
		792	status of the final C<rmdir> only. This is a composite request that
		793	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		794	everything else.
		795
		796	=cut
		797
		798	sub aio_rmtree;
		799	sub aio_rmtree($;$) {
		800	aio_block {
		801	my ($path, $cb) = @_;
		802
		803	my $pri = aioreq_pri;
		804	my $grp = aio_group $cb;
		805
		806	aioreq_pri $pri;
		807	add $grp aio_scandir $path, 0, sub {
		808	my ($dirs, $nondirs) = @_;
		809
		810	my $dirgrp = aio_group sub {
		811	add $grp aio_rmdir $path, sub {
		812	$grp->result ($_[0]);
		813	};
		814	};
		815
		816	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		817	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		818
		819	add $grp $dirgrp;
		820	};
		821
		822	$grp
		823	}
		824	}
		825
247	=item aio_fsync $fh, $callback	826	=item aio_fsync $fh, $callback->($status)
248		827
249	Asynchronously call fsync on the given filehandle and call the callback	828	Asynchronously call fsync on the given filehandle and call the callback
250	with the fsync result code.	829	with the fsync result code.
251		830
252	=item aio_fdatasync $fh, $callback	831	=item aio_fdatasync $fh, $callback->($status)
253		832
254	Asynchronously call fdatasync on the given filehandle and call the	833	Asynchronously call fdatasync on the given filehandle and call the
255	callback with the fdatasync result code.	834	callback with the fdatasync result code.
256		835
257	If this call isn't available because your OS lacks it or it couldn't be	836	If this call isn't available because your OS lacks it or it couldn't be
258	detected, it will be emulated by calling C<fsync> instead.	837	detected, it will be emulated by calling C<fsync> instead.
259		838
		839	=item aio_group $callback->(...)
		840
		841	This is a very special aio request: Instead of doing something, it is a
		842	container for other aio requests, which is useful if you want to bundle
		843	many requests into a single, composite, request with a definite callback
		844	and the ability to cancel the whole request with its subrequests.
		845
		846	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		847	for more info.
		848
		849	Example:
		850
		851	my $grp = aio_group sub {
		852	print "all stats done\n";
		853	};
		854
		855	add $grp
		856	(aio_stat ...),
		857	(aio_stat ...),
		858	...;
		859
		860	=item aio_nop $callback->()
		861
		862	This is a special request - it does nothing in itself and is only used for
		863	side effects, such as when you want to add a dummy request to a group so
		864	that finishing the requests in the group depends on executing the given
		865	code.
		866
		867	While this request does nothing, it still goes through the execution
		868	phase and still requires a worker thread. Thus, the callback will not
		869	be executed immediately but only after other requests in the queue have
		870	entered their execution phase. This can be used to measure request
		871	latency.
		872
		873	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		874
		875	Mainly used for debugging and benchmarking, this aio request puts one of
		876	the request workers to sleep for the given time.
		877
		878	While it is theoretically handy to have simple I/O scheduling requests
		879	like sleep and file handle readable/writable, the overhead this creates is
		880	immense (it blocks a thread for a long time) so do not use this function
		881	except to put your application under artificial I/O pressure.
		882
260	=back	883	=back
261		884
		885	=head2 IO::AIO::REQ CLASS
		886
		887	All non-aggregate C<aio_*> functions return an object of this class when
		888	called in non-void context.
		889
		890	=over 4
		891
		892	=item cancel $req
		893
		894	Cancels the request, if possible. Has the effect of skipping execution
		895	when entering the B<execute> state and skipping calling the callback when
		896	entering the the B<result> state, but will leave the request otherwise
		897	untouched. That means that requests that currently execute will not be
		898	stopped and resources held by the request will not be freed prematurely.
		899
		900	=item cb $req $callback->(...)
		901
		902	Replace (or simply set) the callback registered to the request.
		903
		904	=back
		905
		906	=head2 IO::AIO::GRP CLASS
		907
		908	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		909	objects of this class, too.
		910
		911	A IO::AIO::GRP object is a special request that can contain multiple other
		912	aio requests.
		913
		914	You create one by calling the C<aio_group> constructing function with a
		915	callback that will be called when all contained requests have entered the
		916	C<done> state:
		917
		918	my $grp = aio_group sub {
		919	print "all requests are done\n";
		920	};
		921
		922	You add requests by calling the C<add> method with one or more
		923	C<IO::AIO::REQ> objects:
		924
		925	$grp->add (aio_unlink "...");
		926
		927	add $grp aio_stat "...", sub {
		928	$_[0] or return $grp->result ("error");
		929
		930	# add another request dynamically, if first succeeded
		931	add $grp aio_open "...", sub {
		932	$grp->result ("ok");
		933	};
		934	};
		935
		936	This makes it very easy to create composite requests (see the source of
		937	C<aio_move> for an application) that work and feel like simple requests.
		938
		939	=over 4
		940
		941	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		942	C<IO::AIO::poll_cb>, just like any other request.
		943
		944	=item * They can be canceled like any other request. Canceling will cancel not
		945	only the request itself, but also all requests it contains.
		946
		947	=item * They can also can also be added to other IO::AIO::GRP objects.
		948
		949	=item * You must not add requests to a group from within the group callback (or
		950	any later time).
		951
		952	=back
		953
		954	Their lifetime, simplified, looks like this: when they are empty, they
		955	will finish very quickly. If they contain only requests that are in the
		956	C<done> state, they will also finish. Otherwise they will continue to
		957	exist.
		958
		959	That means after creating a group you have some time to add requests. And
		960	in the callbacks of those requests, you can add further requests to the
		961	group. And only when all those requests have finished will the the group
		962	itself finish.
		963
		964	=over 4
		965
		966	=item add $grp ...
		967
		968	=item $grp->add (...)
		969
		970	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		971	be added, including other groups, as long as you do not create circular
		972	dependencies.
		973
		974	Returns all its arguments.
		975
		976	=item $grp->cancel_subs
		977
		978	Cancel all subrequests and clears any feeder, but not the group request
		979	itself. Useful when you queued a lot of events but got a result early.
		980
		981	=item $grp->result (...)
		982
		983	Set the result value(s) that will be passed to the group callback when all
		984	subrequests have finished and set thre groups errno to the current value
		985	of errno (just like calling C<errno> without an error number). By default,
		986	no argument will be passed and errno is zero.
		987
		988	=item $grp->errno ([$errno])
		989
		990	Sets the group errno value to C<$errno>, or the current value of errno
		991	when the argument is missing.
		992
		993	Every aio request has an associated errno value that is restored when
		994	the callback is invoked. This method lets you change this value from its
		995	default (0).
		996
		997	Calling C<result> will also set errno, so make sure you either set C<$!>
		998	before the call to C<result>, or call c<errno> after it.
		999
		1000	=item feed $grp $callback->($grp)
		1001
		1002	Sets a feeder/generator on this group: every group can have an attached
		1003	generator that generates requests if idle. The idea behind this is that,
		1004	although you could just queue as many requests as you want in a group,
		1005	this might starve other requests for a potentially long time. For
		1006	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1007	requests, delaying any later requests for a long time.
		1008
		1009	To avoid this, and allow incremental generation of requests, you can
		1010	instead a group and set a feeder on it that generates those requests. The
		1011	feed callback will be called whenever there are few enough (see C<limit>,
		1012	below) requests active in the group itself and is expected to queue more
		1013	requests.
		1014
		1015	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1016	not impose any limits).
		1017
		1018	If the feed does not queue more requests when called, it will be
		1019	automatically removed from the group.
		1020
		1021	If the feed limit is C<0>, it will be set to C<2> automatically.
		1022
		1023	Example:
		1024
		1025	# stat all files in @files, but only ever use four aio requests concurrently:
		1026
		1027	my $grp = aio_group sub { print "finished\n" };
		1028	limit $grp 4;
		1029	feed $grp sub {
		1030	my $file = pop @files
		1031	or return;
		1032
		1033	add $grp aio_stat $file, sub { ... };
		1034	};
		1035
		1036	=item limit $grp $num
		1037
		1038	Sets the feeder limit for the group: The feeder will be called whenever
		1039	the group contains less than this many requests.
		1040
		1041	Setting the limit to C<0> will pause the feeding process.
		1042
		1043	=back
		1044
262	=head2 SUPPORT FUNCTIONS	1045	=head2 SUPPORT FUNCTIONS
		1046
		1047	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
263		1048
264	=over 4	1049	=over 4
265		1050
266	=item $fileno = IO::AIO::poll_fileno	1051	=item $fileno = IO::AIO::poll_fileno
267		1052
…		…
272		1057
273	See C<poll_cb> for an example.	1058	See C<poll_cb> for an example.
274		1059
275	=item IO::AIO::poll_cb	1060	=item IO::AIO::poll_cb
276		1061
277	Process all outstanding events on the result pipe. You have to call this	1062	Process some outstanding events on the result pipe. You have to call this
278	regularly. Returns the number of events processed. Returns immediately	1063	regularly. Returns the number of events processed. Returns immediately
279	when no events are outstanding.	1064	when no events are outstanding. The amount of events processed depends on
		1065	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1066
		1067	If not all requests were processed for whatever reason, the filehandle
		1068	will still be ready when C<poll_cb> returns.
280		1069
281	Example: Install an Event watcher that automatically calls	1070	Example: Install an Event watcher that automatically calls
282	IO::AIO::poll_cb with high priority:	1071	IO::AIO::poll_cb with high priority:
283		1072
284	Event->io (fd => IO::AIO::poll_fileno,	1073	Event->io (fd => IO::AIO::poll_fileno,
285	poll => 'r', async => 1,	1074	poll => 'r', async => 1,
286	cb => \&IO::AIO::poll_cb);	1075	cb => \&IO::AIO::poll_cb);
287		1076
		1077	=item IO::AIO::max_poll_reqs $nreqs
		1078
		1079	=item IO::AIO::max_poll_time $seconds
		1080
		1081	These set the maximum number of requests (default C<0>, meaning infinity)
		1082	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1083	the maximum amount of time (default C<0>, meaning infinity) spent in
		1084	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1085	of time C<poll_cb> is allowed to use).
		1086
		1087	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1088	syscall per request processed, which is not normally a problem unless your
		1089	callbacks are really really fast or your OS is really really slow (I am
		1090	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1091
		1092	Setting these is useful if you want to ensure some level of
		1093	interactiveness when perl is not fast enough to process all requests in
		1094	time.
		1095
		1096	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1097
		1098	Example: Install an Event watcher that automatically calls
		1099	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1100	program get the CPU sometimes even under high AIO load.
		1101
		1102	# try not to spend much more than 0.1s in poll_cb
		1103	IO::AIO::max_poll_time 0.1;
		1104
		1105	# use a low priority so other tasks have priority
		1106	Event->io (fd => IO::AIO::poll_fileno,
		1107	poll => 'r', nice => 1,
		1108	cb => &IO::AIO::poll_cb);
		1109
288	=item IO::AIO::poll_wait	1110	=item IO::AIO::poll_wait
289		1111
		1112	If there are any outstanding requests and none of them in the result
290	Wait till the result filehandle becomes ready for reading (simply does a	1113	phase, wait till the result filehandle becomes ready for reading (simply
291	C<select> on the filehandle. This is useful if you want to synchronously wait	1114	does a C<select> on the filehandle. This is useful if you want to
292	for some requests to finish).	1115	synchronously wait for some requests to finish).
293		1116
294	See C<nreqs> for an example.	1117	See C<nreqs> for an example.
295		1118
		1119	=item IO::AIO::poll
		1120
		1121	Waits until some requests have been handled.
		1122
		1123	Returns the number of requests processed, but is otherwise strictly
		1124	equivalent to:
		1125
		1126	IO::AIO::poll_wait, IO::AIO::poll_cb
		1127
296	=item IO::AIO::nreqs	1128	=item IO::AIO::flush
297		1129
298	Returns the number of requests currently outstanding (i.e. for which their	1130	Wait till all outstanding AIO requests have been handled.
299	callback has not been invoked yet).
300		1131
301	Example: wait till there are no outstanding requests anymore:	1132	Strictly equivalent to:
302		1133
303	IO::AIO::poll_wait, IO::AIO::poll_cb	1134	IO::AIO::poll_wait, IO::AIO::poll_cb
304	while IO::AIO::nreqs;	1135	while IO::AIO::nreqs;
305		1136
306	=item IO::AIO::flush	1137	=back
307		1138
308	Wait till all outstanding AIO requests have been handled.	1139	=head3 CONTROLLING THE NUMBER OF THREADS
309		1140
310	Strictly equivalent to:	1141	=over
311
312	IO::AIO::poll_wait, IO::AIO::poll_cb
313	while IO::AIO::nreqs;
314
315	=item IO::AIO::poll
316
317	Waits until some requests have been handled.
318
319	Strictly equivalent to:
320
321	IO::AIO::poll_wait, IO::AIO::poll_cb
322	if IO::AIO::nreqs;
323		1142
324	=item IO::AIO::min_parallel $nthreads	1143	=item IO::AIO::min_parallel $nthreads
325		1144
326	Set the minimum number of AIO threads to C<$nthreads>. The current default	1145	Set the minimum number of AIO threads to C<$nthreads>. The current
327	is C<4>, which means four asynchronous operations can be done at one time	1146	default is C<8>, which means eight asynchronous operations can execute
328	(the number of outstanding operations, however, is unlimited).	1147	concurrently at any one time (the number of outstanding requests,
		1148	however, is unlimited).
329		1149
330	IO::AIO starts threads only on demand, when an AIO request is queued and	1150	IO::AIO starts threads only on demand, when an AIO request is queued and
331	no free thread exists.	1151	no free thread exists. Please note that queueing up a hundred requests can
		1152	create demand for a hundred threads, even if it turns out that everything
		1153	is in the cache and could have been processed faster by a single thread.
332		1154
333	It is recommended to keep the number of threads low, as some Linux	1155	It is recommended to keep the number of threads relatively low, as some
334	kernel versions will scale negatively with the number of threads (higher	1156	Linux kernel versions will scale negatively with the number of threads
335	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1157	(higher parallelity => MUCH higher latency). With current Linux 2.6
336	threads should be fine.	1158	versions, 4-32 threads should be fine.
337		1159
338	Under most circumstances you don't need to call this function, as the	1160	Under most circumstances you don't need to call this function, as the
339	module selects a default that is suitable for low to moderate load.	1161	module selects a default that is suitable for low to moderate load.
340		1162
341	=item IO::AIO::max_parallel $nthreads	1163	=item IO::AIO::max_parallel $nthreads
…		…
350	This module automatically runs C<max_parallel 0> at program end, to ensure	1172	This module automatically runs C<max_parallel 0> at program end, to ensure
351	that all threads are killed and that there are no outstanding requests.	1173	that all threads are killed and that there are no outstanding requests.
352		1174
353	Under normal circumstances you don't need to call this function.	1175	Under normal circumstances you don't need to call this function.
354		1176
		1177	=item IO::AIO::max_idle $nthreads
		1178
		1179	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1180	threads that did not get a request to process within 10 seconds). That
		1181	means if a thread becomes idle while C<$nthreads> other threads are also
		1182	idle, it will free its resources and exit.
		1183
		1184	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1185	to allow for extremely high load situations, but want to free resources
		1186	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1187
		1188	The default is probably ok in most situations, especially if thread
		1189	creation is fast. If thread creation is very slow on your system you might
		1190	want to use larger values.
		1191
355	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1192	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1193
		1194	This is a very bad function to use in interactive programs because it
		1195	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1196	use an C<aio_group> together with a feed callback.
356		1197
357	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1198	Sets the maximum number of outstanding requests to C<$nreqs>. If you
358	try to queue up more than this number of requests, the caller will block until	1199	to queue up more than this number of requests, the next call to the
359	some requests have been handled.	1200	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1201	function will block until the limit is no longer exceeded.
360		1202
361	The default is very large, so normally there is no practical limit. If you	1203	The default value is very large, so there is no practical limit on the
362	queue up many requests in a loop it often improves speed if you set	1204	number of outstanding requests.
363	this to a relatively low number, such as C<100>.
364		1205
365	Under normal circumstances you don't need to call this function.	1206	You can still queue as many requests as you want. Therefore,
		1207	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1208	as a stop gap to shield against fatal memory overflow (with large values).
		1209
		1210	=back
		1211
		1212	=head3 STATISTICAL INFORMATION
		1213
		1214	=over
		1215
		1216	=item IO::AIO::nreqs
		1217
		1218	Returns the number of requests currently in the ready, execute or pending
		1219	states (i.e. for which their callback has not been invoked yet).
		1220
		1221	Example: wait till there are no outstanding requests anymore:
		1222
		1223	IO::AIO::poll_wait, IO::AIO::poll_cb
		1224	while IO::AIO::nreqs;
		1225
		1226	=item IO::AIO::nready
		1227
		1228	Returns the number of requests currently in the ready state (not yet
		1229	executed).
		1230
		1231	=item IO::AIO::npending
		1232
		1233	Returns the number of requests currently in the pending state (executed,
		1234	but not yet processed by poll_cb).
366		1235
367	=back	1236	=back
368		1237
369	=cut	1238	=cut
370		1239
…		…
382	or return undef;	1251	or return undef;
383		1252
384	*$sym	1253	*$sym
385	}	1254	}
386		1255
387	min_parallel 4;	1256	min_parallel 8;
388		1257
389	END {	1258	END { flush }
390	max_parallel 0;
391	}
392		1259
393	1;	1260	1;
394		1261
395	=head2 FORK BEHAVIOUR	1262	=head2 FORK BEHAVIOUR
		1263
		1264	This module should do "the right thing" when the process using it forks:
396		1265
397	Before the fork, IO::AIO enters a quiescent state where no requests	1266	Before the fork, IO::AIO enters a quiescent state where no requests
398	can be added in other threads and no results will be processed. After	1267	can be added in other threads and no results will be processed. After
399	the fork the parent simply leaves the quiescent state and continues	1268	the fork the parent simply leaves the quiescent state and continues
400	request/result processing, while the child clears the request/result	1269	request/result processing, while the child frees the request/result queue
401	queue (so the requests started before the fork will only be handled in	1270	(so that the requests started before the fork will only be handled in the
402	the parent). Threats will be started on demand until the limit ste in the	1271	parent). Threads will be started on demand until the limit set in the
403	parent process has been reached again.	1272	parent process has been reached again.
404		1273
		1274	In short: the parent will, after a short pause, continue as if fork had
		1275	not been called, while the child will act as if IO::AIO has not been used
		1276	yet.
		1277
		1278	=head2 MEMORY USAGE
		1279
		1280	Per-request usage:
		1281
		1282	Each aio request uses - depending on your architecture - around 100-200
		1283	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1284	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1285	scalars and other data passed into aio requests will also be locked and
		1286	will consume memory till the request has entered the done state.
		1287
		1288	This is now awfully much, so queuing lots of requests is not usually a
		1289	problem.
		1290
		1291	Per-thread usage:
		1292
		1293	In the execution phase, some aio requests require more memory for
		1294	temporary buffers, and each thread requires a stack and other data
		1295	structures (usually around 16k-128k, depending on the OS).
		1296
		1297	=head1 KNOWN BUGS
		1298
		1299	Known bugs will be fixed in the next release.
		1300
405	=head1 SEE ALSO	1301	=head1 SEE ALSO
406		1302
407	L<Coro>, L<Linux::AIO>.	1303	L<Coro::AIO>.
408		1304
409	=head1 AUTHOR	1305	=head1 AUTHOR
410		1306
411	Marc Lehmann <schmorp@schmorp.de>	1307	Marc Lehmann <schmorp@schmorp.de>
412	http://home.schmorp.de/	1308	http://home.schmorp.de/

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing IO-AIO/AIO.pm (file contents): Revision 1.38 by root, Sun Aug 28 10:51:33 2005 UTC vs. Revision 1.106 by root, Fri Jun 1 05:51:21 2007 UTC

Diff Legend

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.38 by root, Sun Aug 28 10:51:33 2005 UTC vs.
Revision 1.106 by root, Fri Jun 1 05:51:21 2007 UTC