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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.64 by root, Mon Oct 23 00:50:10 2006 UTC vs.
Revision 1.115 by root, Mon Sep 24 18:14:00 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
…		…
18	};	19	};
19		20
20	# version 2+ has request and group objects	21	# version 2+ has request and group objects
21	use IO::AIO 2;	22	use IO::AIO 2;
22		23
		24	aioreq_pri 4; # give next request a very high priority
23	my $req = aio_unlink "/tmp/file", sub { };	25	my $req = aio_unlink "/tmp/file", sub { };
24	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
25		27
26	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
27	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
…		…
50	=head1 DESCRIPTION	52	=head1 DESCRIPTION
51		53
52	This module implements asynchronous I/O using whatever means your	54	This module implements asynchronous I/O using whatever means your
53	operating system supports.	55	operating system supports.
54		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
		68	example sockets), using these functions on file descriptors that
		69	support nonblocking operation (again, sockets, pipes etc.) is very
		70	inefficient. Use an event loop for that (such as the L<Event\|Event>
		71	module): IO::AIO will naturally fit into such an event loop itself.
		72
55	Currently, a number of threads are started that execute your read/writes	73	In this version, a number of threads are started that execute your
56	and signal their completion. You don't need thread support in your libc or	74	requests and signal their completion. You don't need thread support
57	perl, and the threads created by this module will not be visible to the	75	in perl, and the threads created by this module will not be visible
58	pthreads library. In the future, this module might make use of the native	76	to perl. In the future, this module might make use of the native aio
59	aio functions available on many operating systems. However, they are often	77	functions available on many operating systems. However, they are often
60	not well-supported (Linux doesn't allow them on normal files currently,	78	not well-supported or restricted (GNU/Linux doesn't allow them on normal
61	for example), and they would only support aio_read and aio_write, so the	79	files currently, for example), and they would only support aio_read and
62	remaining functionality would have to be implemented using threads anyway.	80	aio_write, so the remaining functionality would have to be implemented
		81	using threads anyway.
63		82
64	Although the module will work with in the presence of other threads, it is	83	Although the module will work in the presence of other (Perl-) threads,
65	currently not reentrant, so use appropriate locking yourself, always call	84	it is currently not reentrant in any way, so use appropriate locking
66	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	85	yourself, always call C<poll_cb> from within the same thread, or never
67	C<aio_> functions) recursively.	86	call C<poll_cb> (or other C<aio_> functions) recursively.
		87
		88	=head2 EXAMPLE
		89
		90	This is a simple example that uses the Event module and loads
		91	F</etc/passwd> asynchronously:
		92
		93	use Fcntl;
		94	use Event;
		95	use IO::AIO;
		96
		97	# register the IO::AIO callback with Event
		98	Event->io (fd => IO::AIO::poll_fileno,
		99	poll => 'r',
		100	cb => \&IO::AIO::poll_cb);
		101
		102	# queue the request to open /etc/passwd
		103	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		104	my $fh = shift
		105	or die "error while opening: $!";
		106
		107	# stat'ing filehandles is generally non-blocking
		108	my $size = -s $fh;
		109
		110	# queue a request to read the file
		111	my $contents;
		112	aio_read $fh, 0, $size, $contents, 0, sub {
		113	$_[0] == $size
		114	or die "short read: $!";
		115
		116	close $fh;
		117
		118	# file contents now in $contents
		119	print $contents;
		120
		121	# exit event loop and program
		122	Event::unloop;
		123	};
		124	};
		125
		126	# possibly queue up other requests, or open GUI windows,
		127	# check for sockets etc. etc.
		128
		129	# process events as long as there are some:
		130	Event::loop;
		131
		132	=head1 REQUEST ANATOMY AND LIFETIME
		133
		134	Every C<aio_*> function creates a request. which is a C data structure not
		135	directly visible to Perl.
		136
		137	If called in non-void context, every request function returns a Perl
		138	object representing the request. In void context, nothing is returned,
		139	which saves a bit of memory.
		140
		141	The perl object is a fairly standard ref-to-hash object. The hash contents
		142	are not used by IO::AIO so you are free to store anything you like in it.
		143
		144	During their existance, aio requests travel through the following states,
		145	in order:
		146
		147	=over 4
		148
		149	=item ready
		150
		151	Immediately after a request is created it is put into the ready state,
		152	waiting for a thread to execute it.
		153
		154	=item execute
		155
		156	A thread has accepted the request for processing and is currently
		157	executing it (e.g. blocking in read).
		158
		159	=item pending
		160
		161	The request has been executed and is waiting for result processing.
		162
		163	While request submission and execution is fully asynchronous, result
		164	processing is not and relies on the perl interpreter calling C<poll_cb>
		165	(or another function with the same effect).
		166
		167	=item result
		168
		169	The request results are processed synchronously by C<poll_cb>.
		170
		171	The C<poll_cb> function will process all outstanding aio requests by
		172	calling their callbacks, freeing memory associated with them and managing
		173	any groups they are contained in.
		174
		175	=item done
		176
		177	Request has reached the end of its lifetime and holds no resources anymore
		178	(except possibly for the Perl object, but its connection to the actual
		179	aio request is severed and calling its methods will either do nothing or
		180	result in a runtime error).
		181
		182	=back
68		183
69	=cut	184	=cut
70		185
71	package IO::AIO;	186	package IO::AIO;
72		187
…		…
74	use strict 'vars';	189	use strict 'vars';
75		190
76	use base 'Exporter';	191	use base 'Exporter';
77		192
78	BEGIN {	193	BEGIN {
79	our $VERSION = '2.0';	194	our $VERSION = '2.41';
80		195
81	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	196	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
82	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	197	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	198	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
84	aio_group aio_nop);	199	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	200	aio_chown aio_chmod aio_utime aio_truncate);
		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);
86		206
87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
88		208
89	require XSLoader;	209	require XSLoader;
90	XSLoader::load ("IO::AIO", $VERSION);	210	XSLoader::load ("IO::AIO", $VERSION);
91	}	211	}
92		212
93	=head1 FUNCTIONS	213	=head1 FUNCTIONS
94		214
95	=head2 AIO FUNCTIONS	215	=head2 AIO REQUEST FUNCTIONS
96		216
97	All the C<aio_*> calls are more or less thin wrappers around the syscall	217	All the C<aio_*> calls are more or less thin wrappers around the syscall
98	with the same name (sans C<aio_>). The arguments are similar or identical,	218	with the same name (sans C<aio_>). The arguments are similar or identical,
99	and they all accept an additional (and optional) C<$callback> argument	219	and they all accept an additional (and optional) C<$callback> argument
100	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
…		…
103	syscall has been executed asynchronously.	223	syscall has been executed asynchronously.
104		224
105	All functions expecting a filehandle keep a copy of the filehandle	225	All functions expecting a filehandle keep a copy of the filehandle
106	internally until the request has finished.	226	internally until the request has finished.
107		227
108	All requests return objects of type L<IO::AIO::REQ> that allow further	228	All functions return request objects of type L<IO::AIO::REQ> that allow
109	manipulation of those requests while they are in-flight.	229	further manipulation of those requests while they are in-flight.
110		230
111	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
112	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
113	request is being executed, the current working directory could have	233	request is being executed, the current working directory could have
114	changed. Alternatively, you can make sure that you never change the	234	changed. Alternatively, you can make sure that you never change the
115	current working directory.	235	current working directory anywhere in the program and then use relative
		236	paths.
116		237
117	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
118	always pass in filenames you got from outside (command line, readdir	239	in filenames you got from outside (command line, readdir etc.) without
119	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
120	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
121	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)
122	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.
123		247
124	=over 4	248	=over 4
		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
		277	=item aioreq_nice $pri_adjust
		278
		279	Similar to C<aioreq_pri>, but subtracts the given value from the current
		280	priority, so the effect is cumulative.
		281
125		282
126	=item aio_open $pathname, $flags, $mode, $callback->($fh)	283	=item aio_open $pathname, $flags, $mode, $callback->($fh)
127		284
128	Asynchronously open or create a file and call the callback with a newly	285	Asynchronously open or create a file and call the callback with a newly
129	created filehandle for the file.	286	created filehandle for the file.
…		…
135	list. They are the same as used by C<sysopen>.	292	list. They are the same as used by C<sysopen>.
136		293
137	Likewise, C<$mode> specifies the mode of the newly created file, if it	294	Likewise, C<$mode> specifies the mode of the newly created file, if it
138	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	295	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
139	except that it is mandatory (i.e. use C<0> if you don't create new files,	296	except that it is mandatory (i.e. use C<0> if you don't create new files,
140	and C<0666> or C<0777> if you do).	297	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		298	by the umask in effect then the request is being executed, so better never
		299	change the umask.
141		300
142	Example:	301	Example:
143		302
144	aio_open "/etc/passwd", O_RDONLY, 0, sub {	303	aio_open "/etc/passwd", O_RDONLY, 0, sub {
145	if ($_[0]) {	304	if ($_[0]) {
…		…
148	} else {	307	} else {
149	die "open failed: $!\n";	308	die "open failed: $!\n";
150	}	309	}
151	};	310	};
152		311
		312
153	=item aio_close $fh, $callback->($status)	313	=item aio_close $fh, $callback->($status)
154		314
155	Asynchronously close a file and call the callback with the result	315	Asynchronously close a file and call the callback with the result
156	code. I<WARNING:> although accepted, you should not pass in a perl	316	code. I<WARNING:> although accepted, you should not pass in a perl
157	filehandle here, as perl will likely close the file descriptor another	317	filehandle here, as perl will likely close the file descriptor another
…		…
159	C<close> or just let filehandles go out of scope.	319	C<close> or just let filehandles go out of scope.
160		320
161	This is supposed to be a bug in the API, so that might change. It's	321	This is supposed to be a bug in the API, so that might change. It's
162	therefore best to avoid this function.	322	therefore best to avoid this function.
163		323
		324
164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	325	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		326
166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	327	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
167		328
168	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	329	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
169	into the scalar given by C<data> and offset C<dataoffset> and calls the	330	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
170	callback without the actual number of bytes read (or -1 on error, just	331	callback without the actual number of bytes read (or -1 on error, just
171	like the syscall).	332	like the syscall).
172		333
		334	If C<$offset> is undefined, then the current file descriptor offset will
		335	be used (and updated), otherwise the file descriptor offset will not be
		336	changed by these calls.
		337
		338	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		339
		340	If C<$dataoffset> is less than zero, it will be counted from the end of
		341	C<$data>.
		342
173	The C<$data> scalar I<MUST NOT> be modified in any way while the request	343	The C<$data> scalar I<MUST NOT> be modified in any way while the request
174	is outstanding. Modifying it can result in segfaults or WW3 (if the	344	is outstanding. Modifying it can result in segfaults or World War III (if
175	necessary/optional hardware is installed).	345	the necessary/optional hardware is installed).
176		346
177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	347	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
178	offset C<0> within the scalar:	348	offset C<0> within the scalar:
179		349
180	aio_read $fh, 7, 15, $buffer, 0, sub {	350	aio_read $fh, 7, 15, $buffer, 0, sub {
181	$_[0] > 0 or die "read error: $!";	351	$_[0] > 0 or die "read error: $!";
182	print "read $_[0] bytes: <$buffer>\n";	352	print "read $_[0] bytes: <$buffer>\n";
183	};	353	};
184		354
185	=item aio_move $srcpath, $dstpath, $callback->($status)
186
187	[EXPERIMENTAL due to internal aio_group use]
188
189	Try to move the I<file> (directories not supported as either source or
190	destination) from C<$srcpath> to C<$dstpath> and call the callback with
191	the C<0> (error) or C<-1> ok.
192
193	This is a composite request that tries to rename(2) the file first. If
194	rename files with C<EXDEV>, it creates the destination file with mode 0200
195	and copies the contents of the source file into it using C<aio_sendfile>,
196	followed by restoring atime, mtime, access mode and uid/gid, in that
197	order, and unlinking the C<$srcpath>.
198
199	If an error occurs, the partial destination file will be unlinked, if
200	possible, except when setting atime, mtime, access mode and uid/gid, where
201	errors are being ignored.
202
203	=cut
204
205	sub aio_move($$$) {
206	my ($src, $dst, $cb) = @_;
207
208	my $grp = aio_group $cb;
209
210	add $grp aio_rename $src, $dst, sub {
211	if ($_[0] && $! == EXDEV) {
212	add $grp aio_open $src, O_RDONLY, 0, sub {
213	if (my $src_fh = $_[0]) {
214	my @stat = stat $src_fh;
215
216	add $grp aio_open $dst, O_WRONLY, 0200, sub {
217	if (my $dst_fh = $_[0]) {
218	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
219	close $src_fh;
220
221	if ($_[0] == $stat[7]) {
222	utime $stat[8], $stat[9], $dst;
223	chmod $stat[2] & 07777, $dst_fh;
224	chown $stat[4], $stat[5], $dst_fh;
225	close $dst_fh;
226
227	add $grp aio_unlink $src, sub {
228	$grp->result ($_[0]);
229	};
230	} else {
231	my $errno = $!;
232	add $grp aio_unlink $dst, sub {
233	$! = $errno;
234	$grp->result (-1);
235	};
236	}
237	};
238	} else {
239	$grp->result (-1);
240	}
241	},
242
243	} else {
244	$grp->result (-1);
245	}
246	};
247	} else {
248	$grp->result ($_[0]);
249	}
250	};
251
252	$grp
253	}
254		355
255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	356	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
256		357
257	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	358	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
258	reading at byte offset C<$in_offset>, and starts writing at the current	359	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
272	C<$in_fh> than are written, and there is no way to find out how many	373	C<$in_fh> than are written, and there is no way to find out how many
273	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	374	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
274	provides the number of bytes written to C<$out_fh>. Only if the result	375	provides the number of bytes written to C<$out_fh>. Only if the result
275	value equals C<$length> one can assume that C<$length> bytes have been	376	value equals C<$length> one can assume that C<$length> bytes have been
276	read.	377	read.
		378
277		379
278	=item aio_readahead $fh,$offset,$length, $callback->($retval)	380	=item aio_readahead $fh,$offset,$length, $callback->($retval)
279		381
280	C<aio_readahead> populates the page cache with data from a file so that	382	C<aio_readahead> populates the page cache with data from a file so that
281	subsequent reads from that file will not block on disk I/O. The C<$offset>	383	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
287	file. The current file offset of the file is left unchanged.	389	file. The current file offset of the file is left unchanged.
288		390
289	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	391	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
290	emulated by simply reading the data, which would have a similar effect.	392	emulated by simply reading the data, which would have a similar effect.
291		393
		394
292	=item aio_stat $fh_or_path, $callback->($status)	395	=item aio_stat $fh_or_path, $callback->($status)
293		396
294	=item aio_lstat $fh, $callback->($status)	397	=item aio_lstat $fh, $callback->($status)
295		398
296	Works like perl's C<stat> or C<lstat> in void context. The callback will	399	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
309	aio_stat "/etc/passwd", sub {	412	aio_stat "/etc/passwd", sub {
310	$_[0] and die "stat failed: $!";	413	$_[0] and die "stat failed: $!";
311	print "size is ", -s _, "\n";	414	print "size is ", -s _, "\n";
312	};	415	};
313		416
		417
		418	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		419
		420	Works like perl's C<utime> function (including the special case of $atime
		421	and $mtime being undef). Fractional times are supported if the underlying
		422	syscalls support them.
		423
		424	When called with a pathname, uses utimes(2) if available, otherwise
		425	utime(2). If called on a file descriptor, uses futimes(2) if available,
		426	otherwise returns ENOSYS, so this is not portable.
		427
		428	Examples:
		429
		430	# set atime and mtime to current time (basically touch(1)):
		431	aio_utime "path", undef, undef;
		432	# set atime to current time and mtime to beginning of the epoch:
		433	aio_utime "path", time, undef; # undef==0
		434
		435
		436	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		437
		438	Works like perl's C<chown> function, except that C<undef> for either $uid
		439	or $gid is being interpreted as "do not change" (but -1 can also be used).
		440
		441	Examples:
		442
		443	# same as "chown root path" in the shell:
		444	aio_chown "path", 0, -1;
		445	# same as above:
		446	aio_chown "path", 0, undef;
		447
		448
		449	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		450
		451	Works like truncate(2) or ftruncate(2).
		452
		453
		454	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		455
		456	Works like perl's C<chmod> function.
		457
		458
314	=item aio_unlink $pathname, $callback->($status)	459	=item aio_unlink $pathname, $callback->($status)
315		460
316	Asynchronously unlink (delete) a file and call the callback with the	461	Asynchronously unlink (delete) a file and call the callback with the
317	result code.	462	result code.
318		463
		464
		465	=item aio_mknod $path, $mode, $dev, $callback->($status)
		466
		467	[EXPERIMENTAL]
		468
		469	Asynchronously create a device node (or fifo). See mknod(2).
		470
		471	The only (POSIX-) portable way of calling this function is:
		472
		473	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		474
		475
319	=item aio_link $srcpath, $dstpath, $callback->($status)	476	=item aio_link $srcpath, $dstpath, $callback->($status)
320		477
321	Asynchronously create a new link to the existing object at C<$srcpath> at	478	Asynchronously create a new link to the existing object at C<$srcpath> at
322	the path C<$dstpath> and call the callback with the result code.	479	the path C<$dstpath> and call the callback with the result code.
323		480
		481
324	=item aio_symlink $srcpath, $dstpath, $callback->($status)	482	=item aio_symlink $srcpath, $dstpath, $callback->($status)
325		483
326	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	484	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
327	the path C<$dstpath> and call the callback with the result code.	485	the path C<$dstpath> and call the callback with the result code.
328		486
		487
		488	=item aio_readlink $path, $callback->($link)
		489
		490	Asynchronously read the symlink specified by C<$path> and pass it to
		491	the callback. If an error occurs, nothing or undef gets passed to the
		492	callback.
		493
		494
329	=item aio_rename $srcpath, $dstpath, $callback->($status)	495	=item aio_rename $srcpath, $dstpath, $callback->($status)
330		496
331	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	497	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
332	rename(2) and call the callback with the result code.	498	rename(2) and call the callback with the result code.
333		499
		500
		501	=item aio_mkdir $pathname, $mode, $callback->($status)
		502
		503	Asynchronously mkdir (create) a directory and call the callback with
		504	the result code. C<$mode> will be modified by the umask at the time the
		505	request is executed, so do not change your umask.
		506
		507
334	=item aio_rmdir $pathname, $callback->($status)	508	=item aio_rmdir $pathname, $callback->($status)
335		509
336	Asynchronously rmdir (delete) a directory and call the callback with the	510	Asynchronously rmdir (delete) a directory and call the callback with the
337	result code.	511	result code.
		512
338		513
339	=item aio_readdir $pathname, $callback->($entries)	514	=item aio_readdir $pathname, $callback->($entries)
340		515
341	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	516	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
342	directory (i.e. opendir + readdir + closedir). The entries will not be	517	directory (i.e. opendir + readdir + closedir). The entries will not be
343	sorted, and will B<NOT> include the C<.> and C<..> entries.	518	sorted, and will B<NOT> include the C<.> and C<..> entries.
344		519
345	The callback a single argument which is either C<undef> or an array-ref	520	The callback a single argument which is either C<undef> or an array-ref
346	with the filenames.	521	with the filenames.
347		522
		523
		524	=item aio_load $path, $data, $callback->($status)
		525
		526	This is a composite request that tries to fully load the given file into
		527	memory. Status is the same as with aio_read.
		528
		529	=cut
		530
		531	sub aio_load($$;$) {
		532	aio_block {
		533	my ($path, undef, $cb) = @_;
		534	my $data = \$_[1];
		535
		536	my $pri = aioreq_pri;
		537	my $grp = aio_group $cb;
		538
		539	aioreq_pri $pri;
		540	add $grp aio_open $path, O_RDONLY, 0, sub {
		541	my $fh = shift
		542	or return $grp->result (-1);
		543
		544	aioreq_pri $pri;
		545	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		546	$grp->result ($_[0]);
		547	};
		548	};
		549
		550	$grp
		551	}
		552	}
		553
		554	=item aio_copy $srcpath, $dstpath, $callback->($status)
		555
		556	Try to copy the I<file> (directories not supported as either source or
		557	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		558	the C<0> (error) or C<-1> ok.
		559
		560	This is a composite request that it creates the destination file with
		561	mode 0200 and copies the contents of the source file into it using
		562	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		563	uid/gid, in that order.
		564
		565	If an error occurs, the partial destination file will be unlinked, if
		566	possible, except when setting atime, mtime, access mode and uid/gid, where
		567	errors are being ignored.
		568
		569	=cut
		570
		571	sub aio_copy($$;$) {
		572	aio_block {
		573	my ($src, $dst, $cb) = @_;
		574
		575	my $pri = aioreq_pri;
		576	my $grp = aio_group $cb;
		577
		578	aioreq_pri $pri;
		579	add $grp aio_open $src, O_RDONLY, 0, sub {
		580	if (my $src_fh = $_[0]) {
		581	my @stat = stat $src_fh;
		582
		583	aioreq_pri $pri;
		584	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		585	if (my $dst_fh = $_[0]) {
		586	aioreq_pri $pri;
		587	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		588	if ($_[0] == $stat[7]) {
		589	$grp->result (0);
		590	close $src_fh;
		591
		592	# those should not normally block. should. should.
		593	utime $stat[8], $stat[9], $dst;
		594	chmod $stat[2] & 07777, $dst_fh;
		595	chown $stat[4], $stat[5], $dst_fh;
		596	close $dst_fh;
		597	} else {
		598	$grp->result (-1);
		599	close $src_fh;
		600	close $dst_fh;
		601
		602	aioreq $pri;
		603	add $grp aio_unlink $dst;
		604	}
		605	};
		606	} else {
		607	$grp->result (-1);
		608	}
		609	},
		610
		611	} else {
		612	$grp->result (-1);
		613	}
		614	};
		615
		616	$grp
		617	}
		618	}
		619
		620	=item aio_move $srcpath, $dstpath, $callback->($status)
		621
		622	Try to move the I<file> (directories not supported as either source or
		623	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		624	the C<0> (error) or C<-1> ok.
		625
		626	This is a composite request that tries to rename(2) the file first. If
		627	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		628	that is successful, unlinking the C<$srcpath>.
		629
		630	=cut
		631
		632	sub aio_move($$;$) {
		633	aio_block {
		634	my ($src, $dst, $cb) = @_;
		635
		636	my $pri = aioreq_pri;
		637	my $grp = aio_group $cb;
		638
		639	aioreq_pri $pri;
		640	add $grp aio_rename $src, $dst, sub {
		641	if ($_[0] && $! == EXDEV) {
		642	aioreq_pri $pri;
		643	add $grp aio_copy $src, $dst, sub {
		644	$grp->result ($_[0]);
		645
		646	if (!$_[0]) {
		647	aioreq_pri $pri;
		648	add $grp aio_unlink $src;
		649	}
		650	};
		651	} else {
		652	$grp->result ($_[0]);
		653	}
		654	};
		655
		656	$grp
		657	}
		658	}
		659
348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	660	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
349		661
350	[EXPERIMENTAL due to internal aio_group use]
351
352	Scans a directory (similar to C<aio_readdir>) but additionally tries to	662	Scans a directory (similar to C<aio_readdir>) but additionally tries to
353	separate the entries of directory C<$path> into two sets of names, ones	663	efficiently separate the entries of directory C<$path> into two sets of
354	you can recurse into (directories or links to them), and ones you cannot	664	names, directories you can recurse into (directories), and ones you cannot
355	recurse into (everything else).	665	recurse into (everything else, including symlinks to directories).
356		666
357	C<aio_scandir> is a composite request that creates of many sub requests_	667	C<aio_scandir> is a composite request that creates of many sub requests_
358	C<$maxreq> specifies the maximum number of outstanding aio requests that	668	C<$maxreq> specifies the maximum number of outstanding aio requests that
359	this function generates. If it is C<< <= 0 >>, then a suitable default	669	this function generates. If it is C<< <= 0 >>, then a suitable default
360	will be chosen (currently 6).	670	will be chosen (currently 4).
361		671
362	On error, the callback is called without arguments, otherwise it receives	672	On error, the callback is called without arguments, otherwise it receives
363	two array-refs with path-relative entry names.	673	two array-refs with path-relative entry names.
364		674
365	Example:	675	Example:
…		…
399	as those tend to return 0 or 1 as link counts, which disables the	709	as those tend to return 0 or 1 as link counts, which disables the
400	directory counting heuristic.	710	directory counting heuristic.
401		711
402	=cut	712	=cut
403		713
404	sub aio_scandir($$$) {	714	sub aio_scandir($$;$) {
		715	aio_block {
405	my ($path, $maxreq, $cb) = @_;	716	my ($path, $maxreq, $cb) = @_;
406		717
		718	my $pri = aioreq_pri;
		719
407	my $grp = aio_group $cb;	720	my $grp = aio_group $cb;
408		721
409	$maxreq = 6 if $maxreq <= 0;	722	$maxreq = 4 if $maxreq <= 0;
410		723
411	# stat once	724	# stat once
		725	aioreq_pri $pri;
412	add $grp aio_stat $path, sub {	726	add $grp aio_stat $path, sub {
413	return $grp->result () if $_[0];	727	return $grp->result () if $_[0];
414	my $now = time;	728	my $now = time;
415	my $hash1 = join ":", (stat _)[0,1,3,7,9];	729	my $hash1 = join ":", (stat _)[0,1,3,7,9];
416		730
417	# read the directory entries	731	# read the directory entries
		732	aioreq_pri $pri;
418	add $grp aio_readdir $path, sub {	733	add $grp aio_readdir $path, sub {
419	my $entries = shift	734	my $entries = shift
420	or return $grp->result ();	735	or return $grp->result ();
421		736
422	# stat the dir another time	737	# stat the dir another time
		738	aioreq_pri $pri;
423	add $grp aio_stat $path, sub {	739	add $grp aio_stat $path, sub {
424	my $hash2 = join ":", (stat _)[0,1,3,7,9];	740	my $hash2 = join ":", (stat _)[0,1,3,7,9];
425		741
426	my $ndirs;	742	my $ndirs;
427		743
428	# take the slow route if anything looks fishy	744	# take the slow route if anything looks fishy
429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	745	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
430	$ndirs = -1;	746	$ndirs = -1;
431	} else {	747	} else {
432	# if nlink == 2, we are finished	748	# if nlink == 2, we are finished
433	# on non-posix-fs's, we rely on nlink < 2	749	# on non-posix-fs's, we rely on nlink < 2
434	$ndirs = (stat _)[3] - 2	750	$ndirs = (stat _)[3] - 2
435	or return $grp->result ([], $entries);	751	or return $grp->result ([], $entries);
436	}	752	}
437		753
438	# sort into likely dirs and likely nondirs	754	# sort into likely dirs and likely nondirs
439	# dirs == files without ".", short entries first	755	# dirs == files without ".", short entries first
440	$entries = [map $_->[0],	756	$entries = [map $_->[0],
441	sort { $b->[1] cmp $a->[1] }	757	sort { $b->[1] cmp $a->[1] }
442	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	758	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
443	@$entries];	759	@$entries];
444		760
445	my (@dirs, @nondirs);	761	my (@dirs, @nondirs);
446		762
447	my ($statcb, $schedcb);
448	my $nreq = 0;
449
450	my $statgrp = add $grp aio_group;	763	my $statgrp = add $grp aio_group sub {
451
452	$schedcb = sub {
453	if (@$entries) {
454	if ($nreq < $maxreq) {
455	my $ent = pop @$entries;
456	$nreq++;
457	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
458	}
459	} elsif (!$nreq) {
460	# finished
461	$statgrp->cancel;
462	undef $statcb;
463	undef $schedcb;
464	$grp->result (\@dirs, \@nondirs);	764	$grp->result (\@dirs, \@nondirs);
465	}	765	};
		766
		767	limit $statgrp $maxreq;
		768	feed $statgrp sub {
		769	return unless @$entries;
		770	my $entry = pop @$entries;
		771
		772	aioreq_pri $pri;
		773	add $statgrp aio_stat "$path/$entry/.", sub {
		774	if ($_[0] < 0) {
		775	push @nondirs, $entry;
		776	} else {
		777	# need to check for real directory
		778	aioreq_pri $pri;
		779	add $statgrp aio_lstat "$path/$entry", sub {
		780	if (-d _) {
		781	push @dirs, $entry;
		782
		783	unless (--$ndirs) {
		784	push @nondirs, @$entries;
		785	feed $statgrp;
		786	}
		787	} else {
		788	push @nondirs, $entry;
		789	}
		790	}
		791	}
		792	};
		793	};
466	};	794	};
467	$statcb = sub {
468	my ($status, $entry) = @_;
469
470	if ($status < 0) {
471	$nreq--;
472	push @nondirs, $entry;
473	&$schedcb;
474	} else {
475	# need to check for real directory
476	add $grp aio_lstat "$path/$entry", sub {
477	$nreq--;
478
479	if (-d _) {
480	push @dirs, $entry;
481
482	if (!--$ndirs) {
483	push @nondirs, @$entries;
484	$entries = [];
485	}
486	} else {
487	push @nondirs, $entry;
488	}
489
490	&$schedcb;
491	}
492	}
493	};
494
495	&$schedcb while @$entries && $nreq < $maxreq;
496	};	795	};
497	};	796	};
		797
		798	$grp
498	};	799	}
		800	}
499		801
		802	=item aio_rmtree $path, $callback->($status)
		803
		804	Delete a directory tree starting (and including) C<$path>, return the
		805	status of the final C<rmdir> only. This is a composite request that
		806	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		807	everything else.
		808
		809	=cut
		810
		811	sub aio_rmtree;
		812	sub aio_rmtree($;$) {
		813	aio_block {
		814	my ($path, $cb) = @_;
		815
		816	my $pri = aioreq_pri;
		817	my $grp = aio_group $cb;
		818
		819	aioreq_pri $pri;
		820	add $grp aio_scandir $path, 0, sub {
		821	my ($dirs, $nondirs) = @_;
		822
		823	my $dirgrp = aio_group sub {
		824	add $grp aio_rmdir $path, sub {
		825	$grp->result ($_[0]);
		826	};
		827	};
		828
		829	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		830	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		831
		832	add $grp $dirgrp;
		833	};
		834
500	$grp	835	$grp
		836	}
501	}	837	}
502		838
503	=item aio_fsync $fh, $callback->($status)	839	=item aio_fsync $fh, $callback->($status)
504		840
505	Asynchronously call fsync on the given filehandle and call the callback	841	Asynchronously call fsync on the given filehandle and call the callback
…		…
513	If this call isn't available because your OS lacks it or it couldn't be	849	If this call isn't available because your OS lacks it or it couldn't be
514	detected, it will be emulated by calling C<fsync> instead.	850	detected, it will be emulated by calling C<fsync> instead.
515		851
516	=item aio_group $callback->(...)	852	=item aio_group $callback->(...)
517		853
518	[EXPERIMENTAL]
519
520	This is a very special aio request: Instead of doing something, it is a	854	This is a very special aio request: Instead of doing something, it is a
521	container for other aio requests, which is useful if you want to bundle	855	container for other aio requests, which is useful if you want to bundle
522	many requests into a single, composite, request.	856	many requests into a single, composite, request with a definite callback
		857	and the ability to cancel the whole request with its subrequests.
523		858
524	Returns an object of class L<IO::AIO::GRP>. See its documentation below	859	Returns an object of class L<IO::AIO::GRP>. See its documentation below
525	for more info.	860	for more info.
526		861
527	Example:	862	Example:
…		…
546	phase and still requires a worker thread. Thus, the callback will not	881	phase and still requires a worker thread. Thus, the callback will not
547	be executed immediately but only after other requests in the queue have	882	be executed immediately but only after other requests in the queue have
548	entered their execution phase. This can be used to measure request	883	entered their execution phase. This can be used to measure request
549	latency.	884	latency.
550		885
551	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED	886	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
552		887
553	Mainly used for debugging and benchmarking, this aio request puts one of	888	Mainly used for debugging and benchmarking, this aio request puts one of
554	the request workers to sleep for the given time.	889	the request workers to sleep for the given time.
555		890
556	While it is theoretically handy to have simple I/O scheduling requests	891	While it is theoretically handy to have simple I/O scheduling requests
557	like sleep and file handle readable/writable, the overhead this creates	892	like sleep and file handle readable/writable, the overhead this creates is
558	is immense, so do not use this function except to put your application	893	immense (it blocks a thread for a long time) so do not use this function
559	under artificial I/O pressure.	894	except to put your application under artificial I/O pressure.
560		895
561	=back	896	=back
562		897
563	=head2 IO::AIO::REQ CLASS	898	=head2 IO::AIO::REQ CLASS
564		899
565	All non-aggregate C<aio_*> functions return an object of this class when	900	All non-aggregate C<aio_*> functions return an object of this class when
566	called in non-void context.	901	called in non-void context.
567		902
568	A request always moves through the following five states in its lifetime,
569	in order: B<ready> (request has been created, but has not been executed
570	yet), B<execute> (request is currently being executed), B<pending>
571	(request has been executed but callback has not been called yet),
572	B<result> (results are being processed synchronously, includes calling the
573	callback) and B<done> (request has reached the end of its lifetime and
574	holds no resources anymore).
575
576	=over 4	903	=over 4
577		904
578	=item $req->cancel	905	=item cancel $req
579		906
580	Cancels the request, if possible. Has the effect of skipping execution	907	Cancels the request, if possible. Has the effect of skipping execution
581	when entering the B<execute> state and skipping calling the callback when	908	when entering the B<execute> state and skipping calling the callback when
582	entering the the B<result> state, but will leave the request otherwise	909	entering the the B<result> state, but will leave the request otherwise
583	untouched. That means that requests that currently execute will not be	910	untouched. That means that requests that currently execute will not be
584	stopped and resources held by the request will not be freed prematurely.	911	stopped and resources held by the request will not be freed prematurely.
585		912
		913	=item cb $req $callback->(...)
		914
		915	Replace (or simply set) the callback registered to the request.
		916
586	=back	917	=back
587		918
588	=head2 IO::AIO::GRP CLASS	919	=head2 IO::AIO::GRP CLASS
589		920
590	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to	921	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
…		…
629	=item * They can also can also be added to other IO::AIO::GRP objects.	960	=item * They can also can also be added to other IO::AIO::GRP objects.
630		961
631	=item * You must not add requests to a group from within the group callback (or	962	=item * You must not add requests to a group from within the group callback (or
632	any later time).	963	any later time).
633		964
634	=item * This does not harmonise well with C<max_outstanding>, so best do
635	not combine C<aio_group> with it. Groups and feeders are recommended for
636	this kind of concurrency-limiting.
637
638	=back	965	=back
639		966
640	Their lifetime, simplified, looks like this: when they are empty, they	967	Their lifetime, simplified, looks like this: when they are empty, they
641	will finish very quickly. If they contain only requests that are in the	968	will finish very quickly. If they contain only requests that are in the
642	C<done> state, they will also finish. Otherwise they will continue to	969	C<done> state, they will also finish. Otherwise they will continue to
…		…
647	group. And only when all those requests have finished will the the group	974	group. And only when all those requests have finished will the the group
648	itself finish.	975	itself finish.
649		976
650	=over 4	977	=over 4
651		978
		979	=item add $grp ...
		980
652	=item $grp->add (...)	981	=item $grp->add (...)
653
654	=item add $grp ...
655		982
656	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can	983	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
657	be added, including other groups, as long as you do not create circular	984	be added, including other groups, as long as you do not create circular
658	dependencies.	985	dependencies.
659		986
660	Returns all its arguments.	987	Returns all its arguments.
661		988
		989	=item $grp->cancel_subs
		990
		991	Cancel all subrequests and clears any feeder, but not the group request
		992	itself. Useful when you queued a lot of events but got a result early.
		993
662	=item $grp->result (...)	994	=item $grp->result (...)
663		995
664	Set the result value(s) that will be passed to the group callback when all	996	Set the result value(s) that will be passed to the group callback when all
665	subrequests have finished. By default, no argument will be passed.	997	subrequests have finished and set thre groups errno to the current value
		998	of errno (just like calling C<errno> without an error number). By default,
		999	no argument will be passed and errno is zero.
666		1000
667	=item $grp->set_feeder ($callback->($grp))	1001	=item $grp->errno ([$errno])
668		1002
669	[VERY EXPERIMENTAL]	1003	Sets the group errno value to C<$errno>, or the current value of errno
		1004	when the argument is missing.
		1005
		1006	Every aio request has an associated errno value that is restored when
		1007	the callback is invoked. This method lets you change this value from its
		1008	default (0).
		1009
		1010	Calling C<result> will also set errno, so make sure you either set C<$!>
		1011	before the call to C<result>, or call c<errno> after it.
		1012
		1013	=item feed $grp $callback->($grp)
670		1014
671	Sets a feeder/generator on this group: every group can have an attached	1015	Sets a feeder/generator on this group: every group can have an attached
672	generator that generates requests if idle. The idea behind this is that,	1016	generator that generates requests if idle. The idea behind this is that,
673	although you could just queue as many requests as you want in a group,	1017	although you could just queue as many requests as you want in a group,
674	this might starve other requests for a potentially long time. For	1018	this might starve other requests for a potentially long time. For
675	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1019	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
676	requests, delaying any later requests for a long time.	1020	requests, delaying any later requests for a long time.
677		1021
678	To avoid this, and allow incremental generation of requests, you can	1022	To avoid this, and allow incremental generation of requests, you can
679	instead a group and set a feeder on it that generates those requests. The	1023	instead a group and set a feeder on it that generates those requests. The
680	feeder will be called whenever there are few enough (see C<feeder_limit>,	1024	feed callback will be called whenever there are few enough (see C<limit>,
681	below) requests active in the group itself and is expected to queue more	1025	below) requests active in the group itself and is expected to queue more
682	requests.	1026	requests.
683		1027
684	The feeder can queue as many requests as it likes (i.e. C<add> does not	1028	The feed callback can queue as many requests as it likes (i.e. C<add> does
685	impose any limits).	1029	not impose any limits).
686		1030
687	If the feeder does not queue more requests when called, it will be	1031	If the feed does not queue more requests when called, it will be
688	automatically removed from the group.	1032	automatically removed from the group.
689		1033
690	If the feeder limit is C<0>, it will be set to C<2> automatically.	1034	If the feed limit is C<0>, it will be set to C<2> automatically.
691		1035
692	Example:	1036	Example:
693		1037
694	# stat all files in @files, but only ever use four aio requests concurrently:	1038	# stat all files in @files, but only ever use four aio requests concurrently:
695		1039
696	my $grp = aio_group sub { print "finished\n" };	1040	my $grp = aio_group sub { print "finished\n" };
697	$grp->feeder_limit (4);	1041	limit $grp 4;
698	$grp->set_feeder (sub {	1042	feed $grp sub {
699	my $file = pop @files	1043	my $file = pop @files
700	or return;	1044	or return;
701		1045
702	add $grp aio_stat $file, sub { ... };	1046	add $grp aio_stat $file, sub { ... };
703	});	1047	};
704		1048
705	=item $grp->feeder_limit ($num)	1049	=item limit $grp $num
706		1050
707	Sets the feeder limit for the group: The feeder will be called whenever	1051	Sets the feeder limit for the group: The feeder will be called whenever
708	the group contains less than this many requests.	1052	the group contains less than this many requests.
709		1053
710	Setting the limit to C<0> will pause the feeding process.	1054	Setting the limit to C<0> will pause the feeding process.
711		1055
712	=back	1056	=back
713		1057
714	=head2 SUPPORT FUNCTIONS	1058	=head2 SUPPORT FUNCTIONS
		1059
		1060	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
715		1061
716	=over 4	1062	=over 4
717		1063
718	=item $fileno = IO::AIO::poll_fileno	1064	=item $fileno = IO::AIO::poll_fileno
719		1065
…		…
724		1070
725	See C<poll_cb> for an example.	1071	See C<poll_cb> for an example.
726		1072
727	=item IO::AIO::poll_cb	1073	=item IO::AIO::poll_cb
728		1074
729	Process all outstanding events on the result pipe. You have to call this	1075	Process some outstanding events on the result pipe. You have to call this
730	regularly. Returns the number of events processed. Returns immediately	1076	regularly. Returns the number of events processed. Returns immediately
731	when no events are outstanding.	1077	when no events are outstanding. The amount of events processed depends on
		1078	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1079
		1080	If not all requests were processed for whatever reason, the filehandle
		1081	will still be ready when C<poll_cb> returns.
732		1082
733	Example: Install an Event watcher that automatically calls	1083	Example: Install an Event watcher that automatically calls
734	IO::AIO::poll_cb with high priority:	1084	IO::AIO::poll_cb with high priority:
735		1085
736	Event->io (fd => IO::AIO::poll_fileno,	1086	Event->io (fd => IO::AIO::poll_fileno,
737	poll => 'r', async => 1,	1087	poll => 'r', async => 1,
738	cb => \&IO::AIO::poll_cb);	1088	cb => \&IO::AIO::poll_cb);
739		1089
		1090	=item IO::AIO::max_poll_reqs $nreqs
		1091
		1092	=item IO::AIO::max_poll_time $seconds
		1093
		1094	These set the maximum number of requests (default C<0>, meaning infinity)
		1095	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1096	the maximum amount of time (default C<0>, meaning infinity) spent in
		1097	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1098	of time C<poll_cb> is allowed to use).
		1099
		1100	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1101	syscall per request processed, which is not normally a problem unless your
		1102	callbacks are really really fast or your OS is really really slow (I am
		1103	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1104
		1105	Setting these is useful if you want to ensure some level of
		1106	interactiveness when perl is not fast enough to process all requests in
		1107	time.
		1108
		1109	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1110
		1111	Example: Install an Event watcher that automatically calls
		1112	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1113	program get the CPU sometimes even under high AIO load.
		1114
		1115	# try not to spend much more than 0.1s in poll_cb
		1116	IO::AIO::max_poll_time 0.1;
		1117
		1118	# use a low priority so other tasks have priority
		1119	Event->io (fd => IO::AIO::poll_fileno,
		1120	poll => 'r', nice => 1,
		1121	cb => &IO::AIO::poll_cb);
		1122
740	=item IO::AIO::poll_wait	1123	=item IO::AIO::poll_wait
741		1124
		1125	If there are any outstanding requests and none of them in the result
742	Wait till the result filehandle becomes ready for reading (simply does a	1126	phase, wait till the result filehandle becomes ready for reading (simply
743	C<select> on the filehandle. This is useful if you want to synchronously wait	1127	does a C<select> on the filehandle. This is useful if you want to
744	for some requests to finish).	1128	synchronously wait for some requests to finish).
745		1129
746	See C<nreqs> for an example.	1130	See C<nreqs> for an example.
747		1131
		1132	=item IO::AIO::poll
		1133
		1134	Waits until some requests have been handled.
		1135
		1136	Returns the number of requests processed, but is otherwise strictly
		1137	equivalent to:
		1138
		1139	IO::AIO::poll_wait, IO::AIO::poll_cb
		1140
748	=item IO::AIO::nreqs	1141	=item IO::AIO::flush
749		1142
750	Returns the number of requests currently outstanding (i.e. for which their	1143	Wait till all outstanding AIO requests have been handled.
751	callback has not been invoked yet).
752		1144
753	Example: wait till there are no outstanding requests anymore:	1145	Strictly equivalent to:
754		1146
755	IO::AIO::poll_wait, IO::AIO::poll_cb	1147	IO::AIO::poll_wait, IO::AIO::poll_cb
756	while IO::AIO::nreqs;	1148	while IO::AIO::nreqs;
757		1149
758	=item IO::AIO::flush	1150	=back
759		1151
760	Wait till all outstanding AIO requests have been handled.	1152	=head3 CONTROLLING THE NUMBER OF THREADS
761		1153
762	Strictly equivalent to:	1154	=over
763
764	IO::AIO::poll_wait, IO::AIO::poll_cb
765	while IO::AIO::nreqs;
766
767	=item IO::AIO::poll
768
769	Waits until some requests have been handled.
770
771	Strictly equivalent to:
772
773	IO::AIO::poll_wait, IO::AIO::poll_cb
774	if IO::AIO::nreqs;
775		1155
776	=item IO::AIO::min_parallel $nthreads	1156	=item IO::AIO::min_parallel $nthreads
777		1157
778	Set the minimum number of AIO threads to C<$nthreads>. The current	1158	Set the minimum number of AIO threads to C<$nthreads>. The current
779	default is C<8>, which means eight asynchronous operations can execute	1159	default is C<8>, which means eight asynchronous operations can execute
780	concurrently at any one time (the number of outstanding requests,	1160	concurrently at any one time (the number of outstanding requests,
781	however, is unlimited).	1161	however, is unlimited).
782		1162
783	IO::AIO starts threads only on demand, when an AIO request is queued and	1163	IO::AIO starts threads only on demand, when an AIO request is queued and
784	no free thread exists.	1164	no free thread exists. Please note that queueing up a hundred requests can
		1165	create demand for a hundred threads, even if it turns out that everything
		1166	is in the cache and could have been processed faster by a single thread.
785		1167
786	It is recommended to keep the number of threads relatively low, as some	1168	It is recommended to keep the number of threads relatively low, as some
787	Linux kernel versions will scale negatively with the number of threads	1169	Linux kernel versions will scale negatively with the number of threads
788	(higher parallelity => MUCH higher latency). With current Linux 2.6	1170	(higher parallelity => MUCH higher latency). With current Linux 2.6
789	versions, 4-32 threads should be fine.	1171	versions, 4-32 threads should be fine.
…		…
803	This module automatically runs C<max_parallel 0> at program end, to ensure	1185	This module automatically runs C<max_parallel 0> at program end, to ensure
804	that all threads are killed and that there are no outstanding requests.	1186	that all threads are killed and that there are no outstanding requests.
805		1187
806	Under normal circumstances you don't need to call this function.	1188	Under normal circumstances you don't need to call this function.
807		1189
		1190	=item IO::AIO::max_idle $nthreads
		1191
		1192	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1193	threads that did not get a request to process within 10 seconds). That
		1194	means if a thread becomes idle while C<$nthreads> other threads are also
		1195	idle, it will free its resources and exit.
		1196
		1197	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1198	to allow for extremely high load situations, but want to free resources
		1199	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1200
		1201	The default is probably ok in most situations, especially if thread
		1202	creation is fast. If thread creation is very slow on your system you might
		1203	want to use larger values.
		1204
808	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1205	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
809		1206
810	[DEPRECATED]	1207	This is a very bad function to use in interactive programs because it
		1208	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1209	use an C<aio_group> together with a feed callback.
811		1210
812	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1211	Sets the maximum number of outstanding requests to C<$nreqs>. If you
813	try to queue up more than this number of requests, the caller will block until	1212	do queue up more than this number of requests, the next call to the
814	some requests have been handled.	1213	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1214	function will block until the limit is no longer exceeded.
815		1215
816	The default is very large, so normally there is no practical limit. If you	1216	The default value is very large, so there is no practical limit on the
817	queue up many requests in a loop it often improves speed if you set	1217	number of outstanding requests.
818	this to a relatively low number, such as C<100>.
819		1218
820	This function does not work well together with C<aio_group>'s, and their	1219	You can still queue as many requests as you want. Therefore,
821	feeder interface is better suited to limiting concurrency, so do not use	1220	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
822	this function.	1221	as a stop gap to shield against fatal memory overflow (with large values).
823		1222
824	Under normal circumstances you don't need to call this function.	1223	=back
		1224
		1225	=head3 STATISTICAL INFORMATION
		1226
		1227	=over
		1228
		1229	=item IO::AIO::nreqs
		1230
		1231	Returns the number of requests currently in the ready, execute or pending
		1232	states (i.e. for which their callback has not been invoked yet).
		1233
		1234	Example: wait till there are no outstanding requests anymore:
		1235
		1236	IO::AIO::poll_wait, IO::AIO::poll_cb
		1237	while IO::AIO::nreqs;
		1238
		1239	=item IO::AIO::nready
		1240
		1241	Returns the number of requests currently in the ready state (not yet
		1242	executed).
		1243
		1244	=item IO::AIO::npending
		1245
		1246	Returns the number of requests currently in the pending state (executed,
		1247	but not yet processed by poll_cb).
825		1248
826	=back	1249	=back
827		1250
828	=cut	1251	=cut
829		1252
…		…
843	*$sym	1266	*$sym
844	}	1267	}
845		1268
846	min_parallel 8;	1269	min_parallel 8;
847		1270
848	END {	1271	END { flush }
849	max_parallel 0;
850	}
851		1272
852	1;	1273	1;
853		1274
854	=head2 FORK BEHAVIOUR	1275	=head2 FORK BEHAVIOUR
855		1276
856	This module should do "the right thing" when the process using it forks:	1277	This module should do "the right thing" when the process using it forks:
857		1278
858	Before the fork, IO::AIO enters a quiescent state where no requests	1279	Before the fork, IO::AIO enters a quiescent state where no requests
859	can be added in other threads and no results will be processed. After	1280	can be added in other threads and no results will be processed. After
860	the fork the parent simply leaves the quiescent state and continues	1281	the fork the parent simply leaves the quiescent state and continues
861	request/result processing, while the child clears the request/result	1282	request/result processing, while the child frees the request/result queue
862	queue (so the requests started before the fork will only be handled in	1283	(so that the requests started before the fork will only be handled in the
863	the parent). Threads will be started on demand until the limit ste in the	1284	parent). Threads will be started on demand until the limit set in the
864	parent process has been reached again.	1285	parent process has been reached again.
865		1286
866	In short: the parent will, after a short pause, continue as if fork had	1287	In short: the parent will, after a short pause, continue as if fork had
867	not been called, while the child will act as if IO::AIO has not been used	1288	not been called, while the child will act as if IO::AIO has not been used
868	yet.	1289	yet.
869		1290
870	=head2 MEMORY USAGE	1291	=head2 MEMORY USAGE
871		1292
		1293	Per-request usage:
		1294
872	Each aio request uses - depending on your architecture - around 128 bytes	1295	Each aio request uses - depending on your architecture - around 100-200
873	of memory. In addition, stat requests need a stat buffer (possibly a few	1296	bytes of memory. In addition, stat requests need a stat buffer (possibly
874	hundred bytes). Perl scalars and other data passed into aio requests will	1297	a few hundred bytes), readdir requires a result buffer and so on. Perl
875	also be locked.	1298	scalars and other data passed into aio requests will also be locked and
		1299	will consume memory till the request has entered the done state.
876		1300
877	This is now awfully much, so queuing lots of requests is not usually a	1301	This is not awfully much, so queuing lots of requests is not usually a
878	problem.	1302	problem.
879		1303
880	Each thread needs a stack area which is usually around 16k, sometimes much	1304	Per-thread usage:
881	larger, depending on the OS.	1305
		1306	In the execution phase, some aio requests require more memory for
		1307	temporary buffers, and each thread requires a stack and other data
		1308	structures (usually around 16k-128k, depending on the OS).
		1309
		1310	=head1 KNOWN BUGS
		1311
		1312	Known bugs will be fixed in the next release.
882		1313
883	=head1 SEE ALSO	1314	=head1 SEE ALSO
884		1315
885	L<Coro>, L<Linux::AIO> (obsolete).	1316	L<Coro::AIO>.
886		1317
887	=head1 AUTHOR	1318	=head1 AUTHOR
888		1319
889	Marc Lehmann <schmorp@schmorp.de>	1320	Marc Lehmann <schmorp@schmorp.de>
890	http://home.schmorp.de/	1321	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.64 by root, Mon Oct 23 00:50:10 2006 UTC vs. Revision 1.115 by root, Mon Sep 24 18:14:00 2007 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.64 by root, Mon Oct 23 00:50:10 2006 UTC vs.
Revision 1.115 by root, Mon Sep 24 18:14:00 2007 UTC