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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.62 by root, Sun Oct 22 21:13:47 2006 UTC vs.
Revision 1.116 by root, Wed Oct 3 21:27:51 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 = '2.5';
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);	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.
157	filehandle here, as perl will likely close the file descriptor another
158	time when the filehandle is destroyed. Normally, you can safely call perls
159	C<close> or just let filehandles go out of scope.
160		317
161	This is supposed to be a bug in the API, so that might change. It's	318	Unlike the other functions operating on files, this function uses the
162	therefore best to avoid this function.	319	PerlIO layer to close the filehandle. The reason is that the PerlIO API
		320	insists on closing the underlying fd itself, no matter what, and doesn't
		321	allow modifications to the fd. Unfortunately, it is not clear that you can
		322	call PerlIO from different threads (actually, its quite clear that this
		323	won't work in some cases), so while it likely works perfectly with simple
		324	file handles (such as the ones created by C<aio_open>) it might fail in
		325	interesting ways for others.
		326
		327	Having said that, aio_close tries to clean up the filehandle as much as
		328	possible before handing it to an io thread, and generally does work.
		329
163		330
164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	331	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		332
166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	333	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
167		334
168	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	335	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
169	into the scalar given by C<data> and offset C<dataoffset> and calls the	336	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
170	callback without the actual number of bytes read (or -1 on error, just	337	callback without the actual number of bytes read (or -1 on error, just
171	like the syscall).	338	like the syscall).
172		339
		340	If C<$offset> is undefined, then the current file descriptor offset will
		341	be used (and updated), otherwise the file descriptor offset will not be
		342	changed by these calls.
		343
		344	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		345
		346	If C<$dataoffset> is less than zero, it will be counted from the end of
		347	C<$data>.
		348
173	The C<$data> scalar I<MUST NOT> be modified in any way while the request	349	The C<$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	350	is outstanding. Modifying it can result in segfaults or World War III (if
175	necessary/optional hardware is installed).	351	the necessary/optional hardware is installed).
176		352
177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	353	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
178	offset C<0> within the scalar:	354	offset C<0> within the scalar:
179		355
180	aio_read $fh, 7, 15, $buffer, 0, sub {	356	aio_read $fh, 7, 15, $buffer, 0, sub {
181	$_[0] > 0 or die "read error: $!";	357	$_[0] > 0 or die "read error: $!";
182	print "read $_[0] bytes: <$buffer>\n";	358	print "read $_[0] bytes: <$buffer>\n";
183	};	359	};
184		360
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		361
255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	362	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
256		363
257	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	364	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	365	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	379	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	380	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	381	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	382	value equals C<$length> one can assume that C<$length> bytes have been
276	read.	383	read.
		384
277		385
278	=item aio_readahead $fh,$offset,$length, $callback->($retval)	386	=item aio_readahead $fh,$offset,$length, $callback->($retval)
279		387
280	C<aio_readahead> populates the page cache with data from a file so that	388	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>	389	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.	395	file. The current file offset of the file is left unchanged.
288		396
289	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	397	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.	398	emulated by simply reading the data, which would have a similar effect.
291		399
		400
292	=item aio_stat $fh_or_path, $callback->($status)	401	=item aio_stat $fh_or_path, $callback->($status)
293		402
294	=item aio_lstat $fh, $callback->($status)	403	=item aio_lstat $fh, $callback->($status)
295		404
296	Works like perl's C<stat> or C<lstat> in void context. The callback will	405	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
309	aio_stat "/etc/passwd", sub {	418	aio_stat "/etc/passwd", sub {
310	$_[0] and die "stat failed: $!";	419	$_[0] and die "stat failed: $!";
311	print "size is ", -s _, "\n";	420	print "size is ", -s _, "\n";
312	};	421	};
313		422
		423
		424	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		425
		426	Works like perl's C<utime> function (including the special case of $atime
		427	and $mtime being undef). Fractional times are supported if the underlying
		428	syscalls support them.
		429
		430	When called with a pathname, uses utimes(2) if available, otherwise
		431	utime(2). If called on a file descriptor, uses futimes(2) if available,
		432	otherwise returns ENOSYS, so this is not portable.
		433
		434	Examples:
		435
		436	# set atime and mtime to current time (basically touch(1)):
		437	aio_utime "path", undef, undef;
		438	# set atime to current time and mtime to beginning of the epoch:
		439	aio_utime "path", time, undef; # undef==0
		440
		441
		442	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		443
		444	Works like perl's C<chown> function, except that C<undef> for either $uid
		445	or $gid is being interpreted as "do not change" (but -1 can also be used).
		446
		447	Examples:
		448
		449	# same as "chown root path" in the shell:
		450	aio_chown "path", 0, -1;
		451	# same as above:
		452	aio_chown "path", 0, undef;
		453
		454
		455	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		456
		457	Works like truncate(2) or ftruncate(2).
		458
		459
		460	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		461
		462	Works like perl's C<chmod> function.
		463
		464
314	=item aio_unlink $pathname, $callback->($status)	465	=item aio_unlink $pathname, $callback->($status)
315		466
316	Asynchronously unlink (delete) a file and call the callback with the	467	Asynchronously unlink (delete) a file and call the callback with the
317	result code.	468	result code.
318		469
		470
		471	=item aio_mknod $path, $mode, $dev, $callback->($status)
		472
		473	[EXPERIMENTAL]
		474
		475	Asynchronously create a device node (or fifo). See mknod(2).
		476
		477	The only (POSIX-) portable way of calling this function is:
		478
		479	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		480
		481
319	=item aio_link $srcpath, $dstpath, $callback->($status)	482	=item aio_link $srcpath, $dstpath, $callback->($status)
320		483
321	Asynchronously create a new link to the existing object at C<$srcpath> at	484	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.	485	the path C<$dstpath> and call the callback with the result code.
323		486
		487
324	=item aio_symlink $srcpath, $dstpath, $callback->($status)	488	=item aio_symlink $srcpath, $dstpath, $callback->($status)
325		489
326	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	490	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.	491	the path C<$dstpath> and call the callback with the result code.
328		492
		493
		494	=item aio_readlink $path, $callback->($link)
		495
		496	Asynchronously read the symlink specified by C<$path> and pass it to
		497	the callback. If an error occurs, nothing or undef gets passed to the
		498	callback.
		499
		500
329	=item aio_rename $srcpath, $dstpath, $callback->($status)	501	=item aio_rename $srcpath, $dstpath, $callback->($status)
330		502
331	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	503	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
332	rename(2) and call the callback with the result code.	504	rename(2) and call the callback with the result code.
333		505
		506
		507	=item aio_mkdir $pathname, $mode, $callback->($status)
		508
		509	Asynchronously mkdir (create) a directory and call the callback with
		510	the result code. C<$mode> will be modified by the umask at the time the
		511	request is executed, so do not change your umask.
		512
		513
334	=item aio_rmdir $pathname, $callback->($status)	514	=item aio_rmdir $pathname, $callback->($status)
335		515
336	Asynchronously rmdir (delete) a directory and call the callback with the	516	Asynchronously rmdir (delete) a directory and call the callback with the
337	result code.	517	result code.
		518
338		519
339	=item aio_readdir $pathname, $callback->($entries)	520	=item aio_readdir $pathname, $callback->($entries)
340		521
341	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	522	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	523	directory (i.e. opendir + readdir + closedir). The entries will not be
343	sorted, and will B<NOT> include the C<.> and C<..> entries.	524	sorted, and will B<NOT> include the C<.> and C<..> entries.
344		525
345	The callback a single argument which is either C<undef> or an array-ref	526	The callback a single argument which is either C<undef> or an array-ref
346	with the filenames.	527	with the filenames.
347		528
		529
		530	=item aio_load $path, $data, $callback->($status)
		531
		532	This is a composite request that tries to fully load the given file into
		533	memory. Status is the same as with aio_read.
		534
		535	=cut
		536
		537	sub aio_load($$;$) {
		538	aio_block {
		539	my ($path, undef, $cb) = @_;
		540	my $data = \$_[1];
		541
		542	my $pri = aioreq_pri;
		543	my $grp = aio_group $cb;
		544
		545	aioreq_pri $pri;
		546	add $grp aio_open $path, O_RDONLY, 0, sub {
		547	my $fh = shift
		548	or return $grp->result (-1);
		549
		550	aioreq_pri $pri;
		551	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		552	$grp->result ($_[0]);
		553	};
		554	};
		555
		556	$grp
		557	}
		558	}
		559
		560	=item aio_copy $srcpath, $dstpath, $callback->($status)
		561
		562	Try to copy the I<file> (directories not supported as either source or
		563	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		564	the C<0> (error) or C<-1> ok.
		565
		566	This is a composite request that it creates the destination file with
		567	mode 0200 and copies the contents of the source file into it using
		568	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		569	uid/gid, in that order.
		570
		571	If an error occurs, the partial destination file will be unlinked, if
		572	possible, except when setting atime, mtime, access mode and uid/gid, where
		573	errors are being ignored.
		574
		575	=cut
		576
		577	sub aio_copy($$;$) {
		578	aio_block {
		579	my ($src, $dst, $cb) = @_;
		580
		581	my $pri = aioreq_pri;
		582	my $grp = aio_group $cb;
		583
		584	aioreq_pri $pri;
		585	add $grp aio_open $src, O_RDONLY, 0, sub {
		586	if (my $src_fh = $_[0]) {
		587	my @stat = stat $src_fh;
		588
		589	aioreq_pri $pri;
		590	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		591	if (my $dst_fh = $_[0]) {
		592	aioreq_pri $pri;
		593	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		594	if ($_[0] == $stat[7]) {
		595	$grp->result (0);
		596	close $src_fh;
		597
		598	# those should not normally block. should. should.
		599	utime $stat[8], $stat[9], $dst;
		600	chmod $stat[2] & 07777, $dst_fh;
		601	chown $stat[4], $stat[5], $dst_fh;
		602	close $dst_fh;
		603	} else {
		604	$grp->result (-1);
		605	close $src_fh;
		606	close $dst_fh;
		607
		608	aioreq $pri;
		609	add $grp aio_unlink $dst;
		610	}
		611	};
		612	} else {
		613	$grp->result (-1);
		614	}
		615	},
		616
		617	} else {
		618	$grp->result (-1);
		619	}
		620	};
		621
		622	$grp
		623	}
		624	}
		625
		626	=item aio_move $srcpath, $dstpath, $callback->($status)
		627
		628	Try to move the I<file> (directories not supported as either source or
		629	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		630	the C<0> (error) or C<-1> ok.
		631
		632	This is a composite request that tries to rename(2) the file first. If
		633	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		634	that is successful, unlinking the C<$srcpath>.
		635
		636	=cut
		637
		638	sub aio_move($$;$) {
		639	aio_block {
		640	my ($src, $dst, $cb) = @_;
		641
		642	my $pri = aioreq_pri;
		643	my $grp = aio_group $cb;
		644
		645	aioreq_pri $pri;
		646	add $grp aio_rename $src, $dst, sub {
		647	if ($_[0] && $! == EXDEV) {
		648	aioreq_pri $pri;
		649	add $grp aio_copy $src, $dst, sub {
		650	$grp->result ($_[0]);
		651
		652	if (!$_[0]) {
		653	aioreq_pri $pri;
		654	add $grp aio_unlink $src;
		655	}
		656	};
		657	} else {
		658	$grp->result ($_[0]);
		659	}
		660	};
		661
		662	$grp
		663	}
		664	}
		665
348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	666	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
349		667
350	[EXPERIMENTAL due to internal aio_group use]
351
352	Scans a directory (similar to C<aio_readdir>) but additionally tries to	668	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	669	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	670	names, directories you can recurse into (directories), and ones you cannot
355	recurse into (everything else).	671	recurse into (everything else, including symlinks to directories).
356		672
357	C<aio_scandir> is a composite request that creates of many sub requests_	673	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	674	C<$maxreq> specifies the maximum number of outstanding aio requests that
359	this function generates. If it is C<< <= 0 >>, then a suitable default	675	this function generates. If it is C<< <= 0 >>, then a suitable default
360	will be chosen (currently 6).	676	will be chosen (currently 4).
361		677
362	On error, the callback is called without arguments, otherwise it receives	678	On error, the callback is called without arguments, otherwise it receives
363	two array-refs with path-relative entry names.	679	two array-refs with path-relative entry names.
364		680
365	Example:	681	Example:
…		…
399	as those tend to return 0 or 1 as link counts, which disables the	715	as those tend to return 0 or 1 as link counts, which disables the
400	directory counting heuristic.	716	directory counting heuristic.
401		717
402	=cut	718	=cut
403		719
404	sub aio_scandir($$$) {	720	sub aio_scandir($$;$) {
		721	aio_block {
405	my ($path, $maxreq, $cb) = @_;	722	my ($path, $maxreq, $cb) = @_;
406		723
		724	my $pri = aioreq_pri;
		725
407	my $grp = aio_group $cb;	726	my $grp = aio_group $cb;
408		727
409	$maxreq = 6 if $maxreq <= 0;	728	$maxreq = 4 if $maxreq <= 0;
410		729
411	# stat once	730	# stat once
		731	aioreq_pri $pri;
412	add $grp aio_stat $path, sub {	732	add $grp aio_stat $path, sub {
413	return $grp->result () if $_[0];	733	return $grp->result () if $_[0];
414	my $now = time;	734	my $now = time;
415	my $hash1 = join ":", (stat _)[0,1,3,7,9];	735	my $hash1 = join ":", (stat _)[0,1,3,7,9];
416		736
417	# read the directory entries	737	# read the directory entries
		738	aioreq_pri $pri;
418	add $grp aio_readdir $path, sub {	739	add $grp aio_readdir $path, sub {
419	my $entries = shift	740	my $entries = shift
420	or return $grp->result ();	741	or return $grp->result ();
421		742
422	# stat the dir another time	743	# stat the dir another time
		744	aioreq_pri $pri;
423	add $grp aio_stat $path, sub {	745	add $grp aio_stat $path, sub {
424	my $hash2 = join ":", (stat _)[0,1,3,7,9];	746	my $hash2 = join ":", (stat _)[0,1,3,7,9];
425		747
426	my $ndirs;	748	my $ndirs;
427		749
428	# take the slow route if anything looks fishy	750	# take the slow route if anything looks fishy
429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	751	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
430	$ndirs = -1;	752	$ndirs = -1;
431	} else {	753	} else {
432	# if nlink == 2, we are finished	754	# if nlink == 2, we are finished
433	# on non-posix-fs's, we rely on nlink < 2	755	# on non-posix-fs's, we rely on nlink < 2
434	$ndirs = (stat _)[3] - 2	756	$ndirs = (stat _)[3] - 2
435	or return $grp->result ([], $entries);	757	or return $grp->result ([], $entries);
436	}	758	}
437		759
438	# sort into likely dirs and likely nondirs	760	# sort into likely dirs and likely nondirs
439	# dirs == files without ".", short entries first	761	# dirs == files without ".", short entries first
440	$entries = [map $_->[0],	762	$entries = [map $_->[0],
441	sort { $b->[1] cmp $a->[1] }	763	sort { $b->[1] cmp $a->[1] }
442	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	764	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
443	@$entries];	765	@$entries];
444		766
445	my (@dirs, @nondirs);	767	my (@dirs, @nondirs);
446		768
447	my ($statcb, $schedcb);
448	my $nreq = 0;
449
450	my $statgrp = add $grp aio_group;	769	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);	770	$grp->result (\@dirs, \@nondirs);
465	}	771	};
		772
		773	limit $statgrp $maxreq;
		774	feed $statgrp sub {
		775	return unless @$entries;
		776	my $entry = pop @$entries;
		777
		778	aioreq_pri $pri;
		779	add $statgrp aio_stat "$path/$entry/.", sub {
		780	if ($_[0] < 0) {
		781	push @nondirs, $entry;
		782	} else {
		783	# need to check for real directory
		784	aioreq_pri $pri;
		785	add $statgrp aio_lstat "$path/$entry", sub {
		786	if (-d _) {
		787	push @dirs, $entry;
		788
		789	unless (--$ndirs) {
		790	push @nondirs, @$entries;
		791	feed $statgrp;
		792	}
		793	} else {
		794	push @nondirs, $entry;
		795	}
		796	}
		797	}
		798	};
		799	};
466	};	800	};
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	};	801	};
497	};	802	};
		803
		804	$grp
498	};	805	}
		806	}
499		807
		808	=item aio_rmtree $path, $callback->($status)
		809
		810	Delete a directory tree starting (and including) C<$path>, return the
		811	status of the final C<rmdir> only. This is a composite request that
		812	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		813	everything else.
		814
		815	=cut
		816
		817	sub aio_rmtree;
		818	sub aio_rmtree($;$) {
		819	aio_block {
		820	my ($path, $cb) = @_;
		821
		822	my $pri = aioreq_pri;
		823	my $grp = aio_group $cb;
		824
		825	aioreq_pri $pri;
		826	add $grp aio_scandir $path, 0, sub {
		827	my ($dirs, $nondirs) = @_;
		828
		829	my $dirgrp = aio_group sub {
		830	add $grp aio_rmdir $path, sub {
		831	$grp->result ($_[0]);
		832	};
		833	};
		834
		835	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		836	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		837
		838	add $grp $dirgrp;
		839	};
		840
500	$grp	841	$grp
		842	}
501	}	843	}
502		844
503	=item aio_fsync $fh, $callback->($status)	845	=item aio_fsync $fh, $callback->($status)
504		846
505	Asynchronously call fsync on the given filehandle and call the callback	847	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	855	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.	856	detected, it will be emulated by calling C<fsync> instead.
515		857
516	=item aio_group $callback->(...)	858	=item aio_group $callback->(...)
517		859
518	[EXPERIMENTAL]
519
520	This is a very special aio request: Instead of doing something, it is a	860	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	861	container for other aio requests, which is useful if you want to bundle
522	many requests into a single, composite, request.	862	many requests into a single, composite, request with a definite callback
		863	and the ability to cancel the whole request with its subrequests.
523		864
524	Returns an object of class L<IO::AIO::GRP>. See its documentation below	865	Returns an object of class L<IO::AIO::GRP>. See its documentation below
525	for more info.	866	for more info.
526		867
527	Example:	868	Example:
…		…
533	add $grp	874	add $grp
534	(aio_stat ...),	875	(aio_stat ...),
535	(aio_stat ...),	876	(aio_stat ...),
536	...;	877	...;
537		878
		879	=item aio_nop $callback->()
		880
		881	This is a special request - it does nothing in itself and is only used for
		882	side effects, such as when you want to add a dummy request to a group so
		883	that finishing the requests in the group depends on executing the given
		884	code.
		885
		886	While this request does nothing, it still goes through the execution
		887	phase and still requires a worker thread. Thus, the callback will not
		888	be executed immediately but only after other requests in the queue have
		889	entered their execution phase. This can be used to measure request
		890	latency.
		891
538	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED	892	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
539		893
540	Mainly used for debugging and benchmarking, this aio request puts one of	894	Mainly used for debugging and benchmarking, this aio request puts one of
541	the request workers to sleep for the given time.	895	the request workers to sleep for the given time.
542		896
543	While it is theoretically handy to have simple I/O scheduling requests	897	While it is theoretically handy to have simple I/O scheduling requests
544	like sleep and file handle readable/writable, the overhead this creates	898	like sleep and file handle readable/writable, the overhead this creates is
545	is immense, so do not use this function except to put your application	899	immense (it blocks a thread for a long time) so do not use this function
546	under artificial I/O pressure.	900	except to put your application under artificial I/O pressure.
547		901
548	=back	902	=back
549		903
550	=head2 IO::AIO::REQ CLASS	904	=head2 IO::AIO::REQ CLASS
551		905
552	All non-aggregate C<aio_*> functions return an object of this class when	906	All non-aggregate C<aio_*> functions return an object of this class when
553	called in non-void context.	907	called in non-void context.
554		908
555	A request always moves through the following five states in its lifetime,
556	in order: B<ready> (request has been created, but has not been executed
557	yet), B<execute> (request is currently being executed), B<pending>
558	(request has been executed but callback has not been called yet),
559	B<result> (results are being processed synchronously, includes calling the
560	callback) and B<done> (request has reached the end of its lifetime and
561	holds no resources anymore).
562
563	=over 4	909	=over 4
564		910
565	=item $req->cancel	911	=item cancel $req
566		912
567	Cancels the request, if possible. Has the effect of skipping execution	913	Cancels the request, if possible. Has the effect of skipping execution
568	when entering the B<execute> state and skipping calling the callback when	914	when entering the B<execute> state and skipping calling the callback when
569	entering the the B<result> state, but will leave the request otherwise	915	entering the the B<result> state, but will leave the request otherwise
570	untouched. That means that requests that currently execute will not be	916	untouched. That means that requests that currently execute will not be
571	stopped and resources held by the request will not be freed prematurely.	917	stopped and resources held by the request will not be freed prematurely.
572		918
		919	=item cb $req $callback->(...)
		920
		921	Replace (or simply set) the callback registered to the request.
		922
573	=back	923	=back
574		924
575	=head2 IO::AIO::GRP CLASS	925	=head2 IO::AIO::GRP CLASS
576		926
577	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to	927	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
…		…
616	=item * They can also can also be added to other IO::AIO::GRP objects.	966	=item * They can also can also be added to other IO::AIO::GRP objects.
617		967
618	=item * You must not add requests to a group from within the group callback (or	968	=item * You must not add requests to a group from within the group callback (or
619	any later time).	969	any later time).
620		970
621	=item * This does not harmonise well with C<max_outstanding>, so best do
622	not combine C<aio_group> with it. Groups and feeders are recommended for
623	this kind of concurrency-limiting.
624
625	=back	971	=back
626		972
627	Their lifetime, simplified, looks like this: when they are empty, they	973	Their lifetime, simplified, looks like this: when they are empty, they
628	will finish very quickly. If they contain only requests that are in the	974	will finish very quickly. If they contain only requests that are in the
629	C<done> state, they will also finish. Otherwise they will continue to	975	C<done> state, they will also finish. Otherwise they will continue to
…		…
634	group. And only when all those requests have finished will the the group	980	group. And only when all those requests have finished will the the group
635	itself finish.	981	itself finish.
636		982
637	=over 4	983	=over 4
638		984
		985	=item add $grp ...
		986
639	=item $grp->add (...)	987	=item $grp->add (...)
640
641	=item add $grp ...
642		988
643	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can	989	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
644	be added, including other groups, as long as you do not create circular	990	be added, including other groups, as long as you do not create circular
645	dependencies.	991	dependencies.
646		992
647	Returns all its arguments.	993	Returns all its arguments.
648		994
		995	=item $grp->cancel_subs
		996
		997	Cancel all subrequests and clears any feeder, but not the group request
		998	itself. Useful when you queued a lot of events but got a result early.
		999
649	=item $grp->result (...)	1000	=item $grp->result (...)
650		1001
651	Set the result value(s) that will be passed to the group callback when all	1002	Set the result value(s) that will be passed to the group callback when all
652	subrequests have finished. By default, no argument will be passed.	1003	subrequests have finished and set thre groups errno to the current value
		1004	of errno (just like calling C<errno> without an error number). By default,
		1005	no argument will be passed and errno is zero.
653		1006
654	=item $grp->set_feeder ($callback->($grp))	1007	=item $grp->errno ([$errno])
655		1008
656	[VERY EXPERIMENTAL]	1009	Sets the group errno value to C<$errno>, or the current value of errno
		1010	when the argument is missing.
		1011
		1012	Every aio request has an associated errno value that is restored when
		1013	the callback is invoked. This method lets you change this value from its
		1014	default (0).
		1015
		1016	Calling C<result> will also set errno, so make sure you either set C<$!>
		1017	before the call to C<result>, or call c<errno> after it.
		1018
		1019	=item feed $grp $callback->($grp)
657		1020
658	Sets a feeder/generator on this group: every group can have an attached	1021	Sets a feeder/generator on this group: every group can have an attached
659	generator that generates requests if idle. The idea behind this is that,	1022	generator that generates requests if idle. The idea behind this is that,
660	although you could just queue as many requests as you want in a group,	1023	although you could just queue as many requests as you want in a group,
661	this might starve other requests for a potentially long time. For	1024	this might starve other requests for a potentially long time. For
662	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1025	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
663	requests, delaying any later requests for a long time.	1026	requests, delaying any later requests for a long time.
664		1027
665	To avoid this, and allow incremental generation of requests, you can	1028	To avoid this, and allow incremental generation of requests, you can
666	instead a group and set a feeder on it that generates those requests. The	1029	instead a group and set a feeder on it that generates those requests. The
667	feeder will be called whenever there are few enough (see C<feeder_limit>,	1030	feed callback will be called whenever there are few enough (see C<limit>,
668	below) requests active in the group itself and is expected to queue more	1031	below) requests active in the group itself and is expected to queue more
669	requests.	1032	requests.
670		1033
671	The feeder can queue as many requests as it likes (i.e. C<add> does not	1034	The feed callback can queue as many requests as it likes (i.e. C<add> does
672	impose any limits).	1035	not impose any limits).
673		1036
674	If the feeder does not queue more requests when called, it will be	1037	If the feed does not queue more requests when called, it will be
675	automatically removed from the group.	1038	automatically removed from the group.
676		1039
677	If the feeder limit is C<0>, it will be set to C<2> automatically.	1040	If the feed limit is C<0>, it will be set to C<2> automatically.
678		1041
679	Example:	1042	Example:
680		1043
681	# stat all files in @files, but only ever use four aio requests concurrently:	1044	# stat all files in @files, but only ever use four aio requests concurrently:
682		1045
683	my $grp = aio_group sub { print "finished\n" };	1046	my $grp = aio_group sub { print "finished\n" };
684	$grp->feeder_limit (4);	1047	limit $grp 4;
685	$grp->set_feeder (sub {	1048	feed $grp sub {
686	my $file = pop @files	1049	my $file = pop @files
687	or return;	1050	or return;
688		1051
689	add $grp aio_stat $file, sub { ... };	1052	add $grp aio_stat $file, sub { ... };
690	});	1053	};
691		1054
692	=item $grp->feeder_limit ($num)	1055	=item limit $grp $num
693		1056
694	Sets the feeder limit for the group: The feeder will be called whenever	1057	Sets the feeder limit for the group: The feeder will be called whenever
695	the group contains less than this many requests.	1058	the group contains less than this many requests.
696		1059
697	Setting the limit to C<0> will pause the feeding process.	1060	Setting the limit to C<0> will pause the feeding process.
698		1061
699	=back	1062	=back
700		1063
701	=head2 SUPPORT FUNCTIONS	1064	=head2 SUPPORT FUNCTIONS
		1065
		1066	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
702		1067
703	=over 4	1068	=over 4
704		1069
705	=item $fileno = IO::AIO::poll_fileno	1070	=item $fileno = IO::AIO::poll_fileno
706		1071
…		…
711		1076
712	See C<poll_cb> for an example.	1077	See C<poll_cb> for an example.
713		1078
714	=item IO::AIO::poll_cb	1079	=item IO::AIO::poll_cb
715		1080
716	Process all outstanding events on the result pipe. You have to call this	1081	Process some outstanding events on the result pipe. You have to call this
717	regularly. Returns the number of events processed. Returns immediately	1082	regularly. Returns the number of events processed. Returns immediately
718	when no events are outstanding.	1083	when no events are outstanding. The amount of events processed depends on
		1084	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1085
		1086	If not all requests were processed for whatever reason, the filehandle
		1087	will still be ready when C<poll_cb> returns.
719		1088
720	Example: Install an Event watcher that automatically calls	1089	Example: Install an Event watcher that automatically calls
721	IO::AIO::poll_cb with high priority:	1090	IO::AIO::poll_cb with high priority:
722		1091
723	Event->io (fd => IO::AIO::poll_fileno,	1092	Event->io (fd => IO::AIO::poll_fileno,
724	poll => 'r', async => 1,	1093	poll => 'r', async => 1,
725	cb => \&IO::AIO::poll_cb);	1094	cb => \&IO::AIO::poll_cb);
726		1095
		1096	=item IO::AIO::max_poll_reqs $nreqs
		1097
		1098	=item IO::AIO::max_poll_time $seconds
		1099
		1100	These set the maximum number of requests (default C<0>, meaning infinity)
		1101	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1102	the maximum amount of time (default C<0>, meaning infinity) spent in
		1103	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1104	of time C<poll_cb> is allowed to use).
		1105
		1106	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1107	syscall per request processed, which is not normally a problem unless your
		1108	callbacks are really really fast or your OS is really really slow (I am
		1109	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1110
		1111	Setting these is useful if you want to ensure some level of
		1112	interactiveness when perl is not fast enough to process all requests in
		1113	time.
		1114
		1115	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1116
		1117	Example: Install an Event watcher that automatically calls
		1118	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1119	program get the CPU sometimes even under high AIO load.
		1120
		1121	# try not to spend much more than 0.1s in poll_cb
		1122	IO::AIO::max_poll_time 0.1;
		1123
		1124	# use a low priority so other tasks have priority
		1125	Event->io (fd => IO::AIO::poll_fileno,
		1126	poll => 'r', nice => 1,
		1127	cb => &IO::AIO::poll_cb);
		1128
727	=item IO::AIO::poll_wait	1129	=item IO::AIO::poll_wait
728		1130
		1131	If there are any outstanding requests and none of them in the result
729	Wait till the result filehandle becomes ready for reading (simply does a	1132	phase, wait till the result filehandle becomes ready for reading (simply
730	C<select> on the filehandle. This is useful if you want to synchronously wait	1133	does a C<select> on the filehandle. This is useful if you want to
731	for some requests to finish).	1134	synchronously wait for some requests to finish).
732		1135
733	See C<nreqs> for an example.	1136	See C<nreqs> for an example.
734		1137
		1138	=item IO::AIO::poll
		1139
		1140	Waits until some requests have been handled.
		1141
		1142	Returns the number of requests processed, but is otherwise strictly
		1143	equivalent to:
		1144
		1145	IO::AIO::poll_wait, IO::AIO::poll_cb
		1146
735	=item IO::AIO::nreqs	1147	=item IO::AIO::flush
736		1148
737	Returns the number of requests currently outstanding (i.e. for which their	1149	Wait till all outstanding AIO requests have been handled.
738	callback has not been invoked yet).
739		1150
740	Example: wait till there are no outstanding requests anymore:	1151	Strictly equivalent to:
741		1152
742	IO::AIO::poll_wait, IO::AIO::poll_cb	1153	IO::AIO::poll_wait, IO::AIO::poll_cb
743	while IO::AIO::nreqs;	1154	while IO::AIO::nreqs;
744		1155
745	=item IO::AIO::flush	1156	=back
746		1157
747	Wait till all outstanding AIO requests have been handled.	1158	=head3 CONTROLLING THE NUMBER OF THREADS
748		1159
749	Strictly equivalent to:	1160	=over
750
751	IO::AIO::poll_wait, IO::AIO::poll_cb
752	while IO::AIO::nreqs;
753
754	=item IO::AIO::poll
755
756	Waits until some requests have been handled.
757
758	Strictly equivalent to:
759
760	IO::AIO::poll_wait, IO::AIO::poll_cb
761	if IO::AIO::nreqs;
762		1161
763	=item IO::AIO::min_parallel $nthreads	1162	=item IO::AIO::min_parallel $nthreads
764		1163
765	Set the minimum number of AIO threads to C<$nthreads>. The current	1164	Set the minimum number of AIO threads to C<$nthreads>. The current
766	default is C<8>, which means eight asynchronous operations can execute	1165	default is C<8>, which means eight asynchronous operations can execute
767	concurrently at any one time (the number of outstanding requests,	1166	concurrently at any one time (the number of outstanding requests,
768	however, is unlimited).	1167	however, is unlimited).
769		1168
770	IO::AIO starts threads only on demand, when an AIO request is queued and	1169	IO::AIO starts threads only on demand, when an AIO request is queued and
771	no free thread exists.	1170	no free thread exists. Please note that queueing up a hundred requests can
		1171	create demand for a hundred threads, even if it turns out that everything
		1172	is in the cache and could have been processed faster by a single thread.
772		1173
773	It is recommended to keep the number of threads relatively low, as some	1174	It is recommended to keep the number of threads relatively low, as some
774	Linux kernel versions will scale negatively with the number of threads	1175	Linux kernel versions will scale negatively with the number of threads
775	(higher parallelity => MUCH higher latency). With current Linux 2.6	1176	(higher parallelity => MUCH higher latency). With current Linux 2.6
776	versions, 4-32 threads should be fine.	1177	versions, 4-32 threads should be fine.
…		…
790	This module automatically runs C<max_parallel 0> at program end, to ensure	1191	This module automatically runs C<max_parallel 0> at program end, to ensure
791	that all threads are killed and that there are no outstanding requests.	1192	that all threads are killed and that there are no outstanding requests.
792		1193
793	Under normal circumstances you don't need to call this function.	1194	Under normal circumstances you don't need to call this function.
794		1195
		1196	=item IO::AIO::max_idle $nthreads
		1197
		1198	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1199	threads that did not get a request to process within 10 seconds). That
		1200	means if a thread becomes idle while C<$nthreads> other threads are also
		1201	idle, it will free its resources and exit.
		1202
		1203	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1204	to allow for extremely high load situations, but want to free resources
		1205	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1206
		1207	The default is probably ok in most situations, especially if thread
		1208	creation is fast. If thread creation is very slow on your system you might
		1209	want to use larger values.
		1210
795	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1211	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
796		1212
797	[DEPRECATED]	1213	This is a very bad function to use in interactive programs because it
		1214	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1215	use an C<aio_group> together with a feed callback.
798		1216
799	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1217	Sets the maximum number of outstanding requests to C<$nreqs>. If you
800	try to queue up more than this number of requests, the caller will block until	1218	do queue up more than this number of requests, the next call to the
801	some requests have been handled.	1219	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1220	function will block until the limit is no longer exceeded.
802		1221
803	The default is very large, so normally there is no practical limit. If you	1222	The default value is very large, so there is no practical limit on the
804	queue up many requests in a loop it often improves speed if you set	1223	number of outstanding requests.
805	this to a relatively low number, such as C<100>.
806		1224
807	This function does not work well together with C<aio_group>'s, and their	1225	You can still queue as many requests as you want. Therefore,
808	feeder interface is better suited to limiting concurrency, so do not use	1226	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
809	this function.	1227	as a stop gap to shield against fatal memory overflow (with large values).
810
811	Under normal circumstances you don't need to call this function.
812		1228
813	=back	1229	=back
814		1230
		1231	=head3 STATISTICAL INFORMATION
		1232
		1233	=over
		1234
		1235	=item IO::AIO::nreqs
		1236
		1237	Returns the number of requests currently in the ready, execute or pending
		1238	states (i.e. for which their callback has not been invoked yet).
		1239
		1240	Example: wait till there are no outstanding requests anymore:
		1241
		1242	IO::AIO::poll_wait, IO::AIO::poll_cb
		1243	while IO::AIO::nreqs;
		1244
		1245	=item IO::AIO::nready
		1246
		1247	Returns the number of requests currently in the ready state (not yet
		1248	executed).
		1249
		1250	=item IO::AIO::npending
		1251
		1252	Returns the number of requests currently in the pending state (executed,
		1253	but not yet processed by poll_cb).
		1254
		1255	=back
		1256
815	=cut	1257	=cut
816		1258
817	# support function to convert a fd into a perl filehandle
818	sub _fd2fh {
819	return undef if $_[0] < 0;
820
821	# try to generate nice filehandles
822	my $sym = "IO::AIO::fd#$_[0]";
823	local *$sym;
824
825	open *$sym, "+<&=$_[0]" # usually works under any unix
826	or open *$sym, "<&=$_[0]" # cygwin needs this
827	or open *$sym, ">&=$_[0]" # or this
828	or return undef;
829
830	*$sym
831	}
832
833	min_parallel 8;	1259	min_parallel 8;
834		1260
835	END {	1261	END { flush }
836	max_parallel 0;
837	}
838		1262
839	1;	1263	1;
840		1264
841	=head2 FORK BEHAVIOUR	1265	=head2 FORK BEHAVIOUR
842		1266
843	This module should do "the right thing" when the process using it forks:	1267	This module should do "the right thing" when the process using it forks:
844		1268
845	Before the fork, IO::AIO enters a quiescent state where no requests	1269	Before the fork, IO::AIO enters a quiescent state where no requests
846	can be added in other threads and no results will be processed. After	1270	can be added in other threads and no results will be processed. After
847	the fork the parent simply leaves the quiescent state and continues	1271	the fork the parent simply leaves the quiescent state and continues
848	request/result processing, while the child clears the request/result	1272	request/result processing, while the child frees the request/result queue
849	queue (so the requests started before the fork will only be handled in	1273	(so that the requests started before the fork will only be handled in the
850	the parent). Threads will be started on demand until the limit ste in the	1274	parent). Threads will be started on demand until the limit set in the
851	parent process has been reached again.	1275	parent process has been reached again.
852		1276
853	In short: the parent will, after a short pause, continue as if fork had	1277	In short: the parent will, after a short pause, continue as if fork had
854	not been called, while the child will act as if IO::AIO has not been used	1278	not been called, while the child will act as if IO::AIO has not been used
855	yet.	1279	yet.
856		1280
857	=head2 MEMORY USAGE	1281	=head2 MEMORY USAGE
858		1282
		1283	Per-request usage:
		1284
859	Each aio request uses - depending on your architecture - around 128 bytes	1285	Each aio request uses - depending on your architecture - around 100-200
860	of memory. In addition, stat requests need a stat buffer (possibly a few	1286	bytes of memory. In addition, stat requests need a stat buffer (possibly
861	hundred bytes). Perl scalars and other data passed into aio requests will	1287	a few hundred bytes), readdir requires a result buffer and so on. Perl
862	also be locked.	1288	scalars and other data passed into aio requests will also be locked and
		1289	will consume memory till the request has entered the done state.
863		1290
864	This is now awfully much, so queuing lots of requests is not usually a	1291	This is not awfully much, so queuing lots of requests is not usually a
865	problem.	1292	problem.
866		1293
867	Each thread needs a stack area which is usually around 16k, sometimes much	1294	Per-thread usage:
868	larger, depending on the OS.	1295
		1296	In the execution phase, some aio requests require more memory for
		1297	temporary buffers, and each thread requires a stack and other data
		1298	structures (usually around 16k-128k, depending on the OS).
		1299
		1300	=head1 KNOWN BUGS
		1301
		1302	Known bugs will be fixed in the next release.
869		1303
870	=head1 SEE ALSO	1304	=head1 SEE ALSO
871		1305
872	L<Coro>, L<Linux::AIO> (obsolete).	1306	L<Coro::AIO>.
873		1307
874	=head1 AUTHOR	1308	=head1 AUTHOR
875		1309
876	Marc Lehmann <schmorp@schmorp.de>	1310	Marc Lehmann <schmorp@schmorp.de>
877	http://home.schmorp.de/	1311	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.62 by root, Sun Oct 22 21:13:47 2006 UTC vs. Revision 1.116 by root, Wed Oct 3 21:27:51 2007 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.62 by root, Sun Oct 22 21:13:47 2006 UTC vs.
Revision 1.116 by root, Wed Oct 3 21:27:51 2007 UTC