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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.58 by root, Sun Oct 22 10:33:19 2006 UTC vs.
Revision 1.104 by root, Sat Mar 24 19:19:11 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 example
		68	sockets), using these functions on file descriptors that support
		69	nonblocking operation (again, sockets, pipes etc.) is very inefficient or
		70	might not work (aio_read fails on sockets/pipes/fifos). Use an event loop
		71	for that (such as the L<Event\|Event> module): IO::AIO will naturally fit
		72	into such an event loop itself.
		73
55	Currently, a number of threads are started that execute your read/writes	74	In this version, a number of threads are started that execute your
56	and signal their completion. You don't need thread support in your libc or	75	requests and signal their completion. You don't need thread support
57	perl, and the threads created by this module will not be visible to the	76	in perl, and the threads created by this module will not be visible
58	pthreads library. In the future, this module might make use of the native	77	to perl. In the future, this module might make use of the native aio
59	aio functions available on many operating systems. However, they are often	78	functions available on many operating systems. However, they are often
60	not well-supported (Linux doesn't allow them on normal files currently,	79	not well-supported or restricted (GNU/Linux doesn't allow them on normal
61	for example), and they would only support aio_read and aio_write, so the	80	files currently, for example), and they would only support aio_read and
62	remaining functionality would have to be implemented using threads anyway.	81	aio_write, so the remaining functionality would have to be implemented
		82	using threads anyway.
63		83
64	Although the module will work with in the presence of other threads, it is	84	Although the module will work with in the presence of other (Perl-)
65	currently not reentrant, so use appropriate locking yourself, always call	85	threads, it is currently not reentrant in any way, so use appropriate
66	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	86	locking yourself, always call C<poll_cb> from within the same thread, or
67	C<aio_> functions) recursively.	87	never call C<poll_cb> (or other C<aio_> functions) recursively.
		88
		89	=head2 EXAMPLE
		90
		91	This is a simple example that uses the Event module and loads
		92	F</etc/passwd> asynchronously:
		93
		94	use Fcntl;
		95	use Event;
		96	use IO::AIO;
		97
		98	# register the IO::AIO callback with Event
		99	Event->io (fd => IO::AIO::poll_fileno,
		100	poll => 'r',
		101	cb => \&IO::AIO::poll_cb);
		102
		103	# queue the request to open /etc/passwd
		104	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		105	my $fh = shift
		106	or die "error while opening: $!";
		107
		108	# stat'ing filehandles is generally non-blocking
		109	my $size = -s $fh;
		110
		111	# queue a request to read the file
		112	my $contents;
		113	aio_read $fh, 0, $size, $contents, 0, sub {
		114	$_[0] == $size
		115	or die "short read: $!";
		116
		117	close $fh;
		118
		119	# file contents now in $contents
		120	print $contents;
		121
		122	# exit event loop and program
		123	Event::unloop;
		124	};
		125	};
		126
		127	# possibly queue up other requests, or open GUI windows,
		128	# check for sockets etc. etc.
		129
		130	# process events as long as there are some:
		131	Event::loop;
		132
		133	=head1 REQUEST ANATOMY AND LIFETIME
		134
		135	Every C<aio_*> function creates a request. which is a C data structure not
		136	directly visible to Perl.
		137
		138	If called in non-void context, every request function returns a Perl
		139	object representing the request. In void context, nothing is returned,
		140	which saves a bit of memory.
		141
		142	The perl object is a fairly standard ref-to-hash object. The hash contents
		143	are not used by IO::AIO so you are free to store anything you like in it.
		144
		145	During their existance, aio requests travel through the following states,
		146	in order:
		147
		148	=over 4
		149
		150	=item ready
		151
		152	Immediately after a request is created it is put into the ready state,
		153	waiting for a thread to execute it.
		154
		155	=item execute
		156
		157	A thread has accepted the request for processing and is currently
		158	executing it (e.g. blocking in read).
		159
		160	=item pending
		161
		162	The request has been executed and is waiting for result processing.
		163
		164	While request submission and execution is fully asynchronous, result
		165	processing is not and relies on the perl interpreter calling C<poll_cb>
		166	(or another function with the same effect).
		167
		168	=item result
		169
		170	The request results are processed synchronously by C<poll_cb>.
		171
		172	The C<poll_cb> function will process all outstanding aio requests by
		173	calling their callbacks, freeing memory associated with them and managing
		174	any groups they are contained in.
		175
		176	=item done
		177
		178	Request has reached the end of its lifetime and holds no resources anymore
		179	(except possibly for the Perl object, but its connection to the actual
		180	aio request is severed and calling its methods will either do nothing or
		181	result in a runtime error).
		182
		183	=back
68		184
69	=cut	185	=cut
70		186
71	package IO::AIO;	187	package IO::AIO;
72		188
…		…
74	use strict 'vars';	190	use strict 'vars';
75		191
76	use base 'Exporter';	192	use base 'Exporter';
77		193
78	BEGIN {	194	BEGIN {
79	our $VERSION = '2.0';	195	our $VERSION = '2.33';
80		196
81	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	197	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	198	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	199	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
84	aio_group);	200	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);	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	=item aioreq_nice $pri_adjust
		277
		278	Similar to C<aioreq_pri>, but subtracts the given value from the current
		279	priority, so the effect is cumulative.
125		280
126	=item aio_open $pathname, $flags, $mode, $callback->($fh)	281	=item aio_open $pathname, $flags, $mode, $callback->($fh)
127		282
128	Asynchronously open or create a file and call the callback with a newly	283	Asynchronously open or create a file and call the callback with a newly
129	created filehandle for the file.	284	created filehandle for the file.
…		…
135	list. They are the same as used by C<sysopen>.	290	list. They are the same as used by C<sysopen>.
136		291
137	Likewise, C<$mode> specifies the mode of the newly created file, if it	292	Likewise, C<$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>,	293	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,	294	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).	295	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		296	by the umask in effect then the request is being executed, so better never
		297	change the umask.
141		298
142	Example:	299	Example:
143		300
144	aio_open "/etc/passwd", O_RDONLY, 0, sub {	301	aio_open "/etc/passwd", O_RDONLY, 0, sub {
145	if ($_[0]) {	302	if ($_[0]) {
…		…
180	aio_read $fh, 7, 15, $buffer, 0, sub {	337	aio_read $fh, 7, 15, $buffer, 0, sub {
181	$_[0] > 0 or die "read error: $!";	338	$_[0] > 0 or die "read error: $!";
182	print "read $_[0] bytes: <$buffer>\n";	339	print "read $_[0] bytes: <$buffer>\n";
183	};	340	};
184		341
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
255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	342	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
256		343
257	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	344	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	345	reading at byte offset C<$in_offset>, and starts writing at the current
259	file offset of C<$out_fh>. Because of that, it is not safe to issue more	346	file offset of C<$out_fh>. Because of that, it is not safe to issue more
…		…
314	=item aio_unlink $pathname, $callback->($status)	401	=item aio_unlink $pathname, $callback->($status)
315		402
316	Asynchronously unlink (delete) a file and call the callback with the	403	Asynchronously unlink (delete) a file and call the callback with the
317	result code.	404	result code.
318		405
		406	=item aio_mknod $path, $mode, $dev, $callback->($status)
		407
		408	[EXPERIMENTAL]
		409
		410	Asynchronously create a device node (or fifo). See mknod(2).
		411
		412	The only (POSIX-) portable way of calling this function is:
		413
		414	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		415
319	=item aio_link $srcpath, $dstpath, $callback->($status)	416	=item aio_link $srcpath, $dstpath, $callback->($status)
320		417
321	Asynchronously create a new link to the existing object at C<$srcpath> at	418	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.	419	the path C<$dstpath> and call the callback with the result code.
323		420
324	=item aio_symlink $srcpath, $dstpath, $callback->($status)	421	=item aio_symlink $srcpath, $dstpath, $callback->($status)
325		422
326	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	423	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.	424	the path C<$dstpath> and call the callback with the result code.
328		425
		426	=item aio_readlink $path, $callback->($link)
		427
		428	Asynchronously read the symlink specified by C<$path> and pass it to
		429	the callback. If an error occurs, nothing or undef gets passed to the
		430	callback.
		431
329	=item aio_rename $srcpath, $dstpath, $callback->($status)	432	=item aio_rename $srcpath, $dstpath, $callback->($status)
330		433
331	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	434	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
332	rename(2) and call the callback with the result code.	435	rename(2) and call the callback with the result code.
		436
		437	=item aio_mkdir $pathname, $mode, $callback->($status)
		438
		439	Asynchronously mkdir (create) a directory and call the callback with
		440	the result code. C<$mode> will be modified by the umask at the time the
		441	request is executed, so do not change your umask.
333		442
334	=item aio_rmdir $pathname, $callback->($status)	443	=item aio_rmdir $pathname, $callback->($status)
335		444
336	Asynchronously rmdir (delete) a directory and call the callback with the	445	Asynchronously rmdir (delete) a directory and call the callback with the
337	result code.	446	result code.
…		…
343	sorted, and will B<NOT> include the C<.> and C<..> entries.	452	sorted, and will B<NOT> include the C<.> and C<..> entries.
344		453
345	The callback a single argument which is either C<undef> or an array-ref	454	The callback a single argument which is either C<undef> or an array-ref
346	with the filenames.	455	with the filenames.
347		456
		457	=item aio_load $path, $data, $callback->($status)
		458
		459	This is a composite request that tries to fully load the given file into
		460	memory. Status is the same as with aio_read.
		461
		462	=cut
		463
		464	sub aio_load($$;$) {
		465	aio_block {
		466	my ($path, undef, $cb) = @_;
		467	my $data = \$_[1];
		468
		469	my $pri = aioreq_pri;
		470	my $grp = aio_group $cb;
		471
		472	aioreq_pri $pri;
		473	add $grp aio_open $path, O_RDONLY, 0, sub {
		474	my $fh = shift
		475	or return $grp->result (-1);
		476
		477	aioreq_pri $pri;
		478	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		479	$grp->result ($_[0]);
		480	};
		481	};
		482
		483	$grp
		484	}
		485	}
		486
		487	=item aio_copy $srcpath, $dstpath, $callback->($status)
		488
		489	Try to copy the I<file> (directories not supported as either source or
		490	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		491	the C<0> (error) or C<-1> ok.
		492
		493	This is a composite request that it creates the destination file with
		494	mode 0200 and copies the contents of the source file into it using
		495	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		496	uid/gid, in that order.
		497
		498	If an error occurs, the partial destination file will be unlinked, if
		499	possible, except when setting atime, mtime, access mode and uid/gid, where
		500	errors are being ignored.
		501
		502	=cut
		503
		504	sub aio_copy($$;$) {
		505	aio_block {
		506	my ($src, $dst, $cb) = @_;
		507
		508	my $pri = aioreq_pri;
		509	my $grp = aio_group $cb;
		510
		511	aioreq_pri $pri;
		512	add $grp aio_open $src, O_RDONLY, 0, sub {
		513	if (my $src_fh = $_[0]) {
		514	my @stat = stat $src_fh;
		515
		516	aioreq_pri $pri;
		517	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		518	if (my $dst_fh = $_[0]) {
		519	aioreq_pri $pri;
		520	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		521	if ($_[0] == $stat[7]) {
		522	$grp->result (0);
		523	close $src_fh;
		524
		525	# those should not normally block. should. should.
		526	utime $stat[8], $stat[9], $dst;
		527	chmod $stat[2] & 07777, $dst_fh;
		528	chown $stat[4], $stat[5], $dst_fh;
		529	close $dst_fh;
		530	} else {
		531	$grp->result (-1);
		532	close $src_fh;
		533	close $dst_fh;
		534
		535	aioreq $pri;
		536	add $grp aio_unlink $dst;
		537	}
		538	};
		539	} else {
		540	$grp->result (-1);
		541	}
		542	},
		543
		544	} else {
		545	$grp->result (-1);
		546	}
		547	};
		548
		549	$grp
		550	}
		551	}
		552
		553	=item aio_move $srcpath, $dstpath, $callback->($status)
		554
		555	Try to move the I<file> (directories not supported as either source or
		556	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		557	the C<0> (error) or C<-1> ok.
		558
		559	This is a composite request that tries to rename(2) the file first. If
		560	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		561	that is successful, unlinking the C<$srcpath>.
		562
		563	=cut
		564
		565	sub aio_move($$;$) {
		566	aio_block {
		567	my ($src, $dst, $cb) = @_;
		568
		569	my $pri = aioreq_pri;
		570	my $grp = aio_group $cb;
		571
		572	aioreq_pri $pri;
		573	add $grp aio_rename $src, $dst, sub {
		574	if ($_[0] && $! == EXDEV) {
		575	aioreq_pri $pri;
		576	add $grp aio_copy $src, $dst, sub {
		577	$grp->result ($_[0]);
		578
		579	if (!$_[0]) {
		580	aioreq_pri $pri;
		581	add $grp aio_unlink $src;
		582	}
		583	};
		584	} else {
		585	$grp->result ($_[0]);
		586	}
		587	};
		588
		589	$grp
		590	}
		591	}
		592
348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	593	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
349		594
350	[EXPERIMENTAL due to internal aio_group use]
351
352	Scans a directory (similar to C<aio_readdir>) but additionally tries to	595	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	596	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	597	names, directories you can recurse into (directories), and ones you cannot
355	recurse into (everything else).	598	recurse into (everything else, including symlinks to directories).
356		599
357	C<aio_scandir> is a composite request that consists of many sub	600	C<aio_scandir> is a composite request that creates of many sub requests_
358	requests. C<$maxreq> specifies the maximum number of outstanding aio	601	C<$maxreq> specifies the maximum number of outstanding aio requests that
359	requests that this function generates. If it is C<< <= 0 >>, then a	602	this function generates. If it is C<< <= 0 >>, then a suitable default
360	suitable default will be chosen (currently 8).	603	will be chosen (currently 4).
361		604
362	On error, the callback is called without arguments, otherwise it receives	605	On error, the callback is called without arguments, otherwise it receives
363	two array-refs with path-relative entry names.	606	two array-refs with path-relative entry names.
364		607
365	Example:	608	Example:
…		…
399	as those tend to return 0 or 1 as link counts, which disables the	642	as those tend to return 0 or 1 as link counts, which disables the
400	directory counting heuristic.	643	directory counting heuristic.
401		644
402	=cut	645	=cut
403		646
404	sub aio_scandir($$$) {	647	sub aio_scandir($$;$) {
		648	aio_block {
405	my ($path, $maxreq, $cb) = @_;	649	my ($path, $maxreq, $cb) = @_;
406		650
		651	my $pri = aioreq_pri;
		652
407	my $grp = aio_group $cb;	653	my $grp = aio_group $cb;
408		654
409	$maxreq = 8 if $maxreq <= 0;	655	$maxreq = 4 if $maxreq <= 0;
410		656
411	# stat once	657	# stat once
		658	aioreq_pri $pri;
412	add $grp aio_stat $path, sub {	659	add $grp aio_stat $path, sub {
413	return $grp->result () if $_[0];	660	return $grp->result () if $_[0];
414	my $now = time;	661	my $now = time;
415	my $hash1 = join ":", (stat _)[0,1,3,7,9];	662	my $hash1 = join ":", (stat _)[0,1,3,7,9];
416		663
417	# read the directory entries	664	# read the directory entries
		665	aioreq_pri $pri;
418	add $grp aio_readdir $path, sub {	666	add $grp aio_readdir $path, sub {
419	my $entries = shift	667	my $entries = shift
420	or return $grp->result ();	668	or return $grp->result ();
421		669
422	# stat the dir another time	670	# stat the dir another time
		671	aioreq_pri $pri;
423	add $grp aio_stat $path, sub {	672	add $grp aio_stat $path, sub {
424	my $hash2 = join ":", (stat _)[0,1,3,7,9];	673	my $hash2 = join ":", (stat _)[0,1,3,7,9];
425		674
426	my $ndirs;	675	my $ndirs;
427		676
428	# take the slow route if anything looks fishy	677	# take the slow route if anything looks fishy
429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	678	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
430	$ndirs = -1;	679	$ndirs = -1;
431	} else {	680	} else {
432	# if nlink == 2, we are finished	681	# if nlink == 2, we are finished
433	# on non-posix-fs's, we rely on nlink < 2	682	# on non-posix-fs's, we rely on nlink < 2
434	$ndirs = (stat _)[3] - 2	683	$ndirs = (stat _)[3] - 2
435	or return $grp->result ([], $entries);	684	or return $grp->result ([], $entries);
436	}
437
438	# sort into likely dirs and likely nondirs
439	# dirs == files without ".", short entries first
440	$entries = [map $_->[0],
441	sort { $b->[1] cmp $a->[1] }
442	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
443	@$entries];
444
445	my (@dirs, @nondirs);
446
447	my ($statcb, $schedcb);
448	my $nreq = 0;
449
450	$schedcb = sub {
451	if (@$entries) {
452	if ($nreq < $maxreq) {
453	my $ent = pop @$entries;
454	$nreq++;
455	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
456	}
457	} elsif (!$nreq) {
458	# finished
459	undef $statcb;
460	undef $schedcb;
461	$grp->result (\@dirs, \@nondirs) if $cb;
462	undef $cb;
463	}	685	}
		686
		687	# sort into likely dirs and likely nondirs
		688	# dirs == files without ".", short entries first
		689	$entries = [map $_->[0],
		690	sort { $b->[1] cmp $a->[1] }
		691	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		692	@$entries];
		693
		694	my (@dirs, @nondirs);
		695
		696	my $statgrp = add $grp aio_group sub {
		697	$grp->result (\@dirs, \@nondirs);
		698	};
		699
		700	limit $statgrp $maxreq;
		701	feed $statgrp sub {
		702	return unless @$entries;
		703	my $entry = pop @$entries;
		704
		705	aioreq_pri $pri;
		706	add $statgrp aio_stat "$path/$entry/.", sub {
		707	if ($_[0] < 0) {
		708	push @nondirs, $entry;
		709	} else {
		710	# need to check for real directory
		711	aioreq_pri $pri;
		712	add $statgrp aio_lstat "$path/$entry", sub {
		713	if (-d _) {
		714	push @dirs, $entry;
		715
		716	unless (--$ndirs) {
		717	push @nondirs, @$entries;
		718	feed $statgrp;
		719	}
		720	} else {
		721	push @nondirs, $entry;
		722	}
		723	}
		724	}
		725	};
		726	};
464	};	727	};
465	$statcb = sub {
466	my ($status, $entry) = @_;
467
468	if ($status < 0) {
469	$nreq--;
470	push @nondirs, $entry;
471	&$schedcb;
472	} else {
473	# need to check for real directory
474	add $grp aio_lstat "$path/$entry", sub {
475	$nreq--;
476
477	if (-d _) {
478	push @dirs, $entry;
479
480	if (!--$ndirs) {
481	push @nondirs, @$entries;
482	$entries = [];
483	}
484	} else {
485	push @nondirs, $entry;
486	}
487
488	&$schedcb;
489	}
490	}
491	};
492
493	&$schedcb while @$entries && $nreq < $maxreq;
494	};	728	};
495	};	729	};
		730
		731	$grp
496	};	732	}
		733	}
497		734
		735	=item aio_rmtree $path, $callback->($status)
		736
		737	Delete a directory tree starting (and including) C<$path>, return the
		738	status of the final C<rmdir> only. This is a composite request that
		739	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		740	everything else.
		741
		742	=cut
		743
		744	sub aio_rmtree;
		745	sub aio_rmtree($;$) {
		746	aio_block {
		747	my ($path, $cb) = @_;
		748
		749	my $pri = aioreq_pri;
		750	my $grp = aio_group $cb;
		751
		752	aioreq_pri $pri;
		753	add $grp aio_scandir $path, 0, sub {
		754	my ($dirs, $nondirs) = @_;
		755
		756	my $dirgrp = aio_group sub {
		757	add $grp aio_rmdir $path, sub {
		758	$grp->result ($_[0]);
		759	};
		760	};
		761
		762	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		763	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		764
		765	add $grp $dirgrp;
		766	};
		767
498	$grp	768	$grp
		769	}
499	}	770	}
500		771
501	=item aio_fsync $fh, $callback->($status)	772	=item aio_fsync $fh, $callback->($status)
502		773
503	Asynchronously call fsync on the given filehandle and call the callback	774	Asynchronously call fsync on the given filehandle and call the callback
…		…
511	If this call isn't available because your OS lacks it or it couldn't be	782	If this call isn't available because your OS lacks it or it couldn't be
512	detected, it will be emulated by calling C<fsync> instead.	783	detected, it will be emulated by calling C<fsync> instead.
513		784
514	=item aio_group $callback->(...)	785	=item aio_group $callback->(...)
515		786
516	[EXPERIMENTAL]
517
518	This is a very special aio request: Instead of doing something, it is a	787	This is a very special aio request: Instead of doing something, it is a
519	container for other aio requests, which is useful if you want to bundle	788	container for other aio requests, which is useful if you want to bundle
520	many requests into a single, composite, request.	789	many requests into a single, composite, request with a definite callback
		790	and the ability to cancel the whole request with its subrequests.
521		791
522	Returns an object of class L<IO::AIO::GRP>. See its documentation below	792	Returns an object of class L<IO::AIO::GRP>. See its documentation below
523	for more info.	793	for more info.
524		794
525	Example:	795	Example:
…		…
531	add $grp	801	add $grp
532	(aio_stat ...),	802	(aio_stat ...),
533	(aio_stat ...),	803	(aio_stat ...),
534	...;	804	...;
535		805
		806	=item aio_nop $callback->()
		807
		808	This is a special request - it does nothing in itself and is only used for
		809	side effects, such as when you want to add a dummy request to a group so
		810	that finishing the requests in the group depends on executing the given
		811	code.
		812
		813	While this request does nothing, it still goes through the execution
		814	phase and still requires a worker thread. Thus, the callback will not
		815	be executed immediately but only after other requests in the queue have
		816	entered their execution phase. This can be used to measure request
		817	latency.
		818
536	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED	819	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
537		820
538	Mainly used for debugging and benchmarking, this aio request puts one of	821	Mainly used for debugging and benchmarking, this aio request puts one of
539	the request workers to sleep for the given time.	822	the request workers to sleep for the given time.
540		823
541	While it is theoretically handy to have simple I/O scheduling requests	824	While it is theoretically handy to have simple I/O scheduling requests
542	like sleep and file handle readable/writable, the overhead this creates	825	like sleep and file handle readable/writable, the overhead this creates is
543	is immense, so do not use this function except to put your application	826	immense (it blocks a thread for a long time) so do not use this function
544	under artificial I/O pressure.	827	except to put your application under artificial I/O pressure.
545		828
546	=back	829	=back
547		830
548	=head2 IO::AIO::REQ CLASS	831	=head2 IO::AIO::REQ CLASS
549		832
550	All non-aggregate C<aio_*> functions return an object of this class when	833	All non-aggregate C<aio_*> functions return an object of this class when
551	called in non-void context.	834	called in non-void context.
552		835
553	A request always moves through the following five states in its lifetime,
554	in order: B<ready> (request has been created, but has not been executed
555	yet), B<execute> (request is currently being executed), B<pending>
556	(request has been executed but callback has not been called yet),
557	B<result> (results are being processed synchronously, includes calling the
558	callback) and B<done> (request has reached the end of its lifetime and
559	holds no resources anymore).
560
561	=over 4	836	=over 4
562		837
563	=item $req->cancel	838	=item cancel $req
564		839
565	Cancels the request, if possible. Has the effect of skipping execution	840	Cancels the request, if possible. Has the effect of skipping execution
566	when entering the B<execute> state and skipping calling the callback when	841	when entering the B<execute> state and skipping calling the callback when
567	entering the the B<result> state, but will leave the request otherwise	842	entering the the B<result> state, but will leave the request otherwise
568	untouched. That means that requests that currently execute will not be	843	untouched. That means that requests that currently execute will not be
569	stopped and resources held by the request will not be freed prematurely.	844	stopped and resources held by the request will not be freed prematurely.
570		845
		846	=item cb $req $callback->(...)
		847
		848	Replace (or simply set) the callback registered to the request.
		849
571	=back	850	=back
572		851
573	=head2 IO::AIO::GRP CLASS	852	=head2 IO::AIO::GRP CLASS
574		853
575	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to	854	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
…		…
601	};	880	};
602		881
603	This makes it very easy to create composite requests (see the source of	882	This makes it very easy to create composite requests (see the source of
604	C<aio_move> for an application) that work and feel like simple requests.	883	C<aio_move> for an application) that work and feel like simple requests.
605		884
		885	=over 4
		886
606	The IO::AIO::GRP objects will be cleaned up during calls to	887	=item * The IO::AIO::GRP objects will be cleaned up during calls to
607	C<IO::AIO::poll_cb>, just like any other request.	888	C<IO::AIO::poll_cb>, just like any other request.
608		889
609	They can be canceled like any other request. Canceling will cancel not	890	=item * They can be canceled like any other request. Canceling will cancel not
610	just the request itself, but also all requests it contains.	891	only the request itself, but also all requests it contains.
611		892
612	They can also can also be added to other IO::AIO::GRP objects.	893	=item * They can also can also be added to other IO::AIO::GRP objects.
		894
		895	=item * You must not add requests to a group from within the group callback (or
		896	any later time).
		897
		898	=back
613		899
614	Their lifetime, simplified, looks like this: when they are empty, they	900	Their lifetime, simplified, looks like this: when they are empty, they
615	will finish very quickly. If they contain only requests that are in the	901	will finish very quickly. If they contain only requests that are in the
616	C<done> state, they will also finish. Otherwise they will continue to	902	C<done> state, they will also finish. Otherwise they will continue to
617	exist.	903	exist.
…		…
621	group. And only when all those requests have finished will the the group	907	group. And only when all those requests have finished will the the group
622	itself finish.	908	itself finish.
623		909
624	=over 4	910	=over 4
625		911
		912	=item add $grp ...
		913
626	=item $grp->add (...)	914	=item $grp->add (...)
627
628	=item add $grp ...
629		915
630	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can	916	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
631	be added, including other groups, as long as you do not create circular	917	be added, including other groups, as long as you do not create circular
632	dependencies.	918	dependencies.
633		919
634	Returns all its arguments.	920	Returns all its arguments.
635		921
		922	=item $grp->cancel_subs
		923
		924	Cancel all subrequests and clears any feeder, but not the group request
		925	itself. Useful when you queued a lot of events but got a result early.
		926
636	=item $grp->result (...)	927	=item $grp->result (...)
637		928
638	Set the result value(s) that will be passed to the group callback when all	929	Set the result value(s) that will be passed to the group callback when all
639	subrequests have finished. By default, no argument will be passed.	930	subrequests have finished and set thre groups errno to the current value
		931	of errno (just like calling C<errno> without an error number). By default,
		932	no argument will be passed and errno is zero.
		933
		934	=item $grp->errno ([$errno])
		935
		936	Sets the group errno value to C<$errno>, or the current value of errno
		937	when the argument is missing.
		938
		939	Every aio request has an associated errno value that is restored when
		940	the callback is invoked. This method lets you change this value from its
		941	default (0).
		942
		943	Calling C<result> will also set errno, so make sure you either set C<$!>
		944	before the call to C<result>, or call c<errno> after it.
		945
		946	=item feed $grp $callback->($grp)
		947
		948	Sets a feeder/generator on this group: every group can have an attached
		949	generator that generates requests if idle. The idea behind this is that,
		950	although you could just queue as many requests as you want in a group,
		951	this might starve other requests for a potentially long time. For
		952	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		953	requests, delaying any later requests for a long time.
		954
		955	To avoid this, and allow incremental generation of requests, you can
		956	instead a group and set a feeder on it that generates those requests. The
		957	feed callback will be called whenever there are few enough (see C<limit>,
		958	below) requests active in the group itself and is expected to queue more
		959	requests.
		960
		961	The feed callback can queue as many requests as it likes (i.e. C<add> does
		962	not impose any limits).
		963
		964	If the feed does not queue more requests when called, it will be
		965	automatically removed from the group.
		966
		967	If the feed limit is C<0>, it will be set to C<2> automatically.
		968
		969	Example:
		970
		971	# stat all files in @files, but only ever use four aio requests concurrently:
		972
		973	my $grp = aio_group sub { print "finished\n" };
		974	limit $grp 4;
		975	feed $grp sub {
		976	my $file = pop @files
		977	or return;
		978
		979	add $grp aio_stat $file, sub { ... };
		980	};
		981
		982	=item limit $grp $num
		983
		984	Sets the feeder limit for the group: The feeder will be called whenever
		985	the group contains less than this many requests.
		986
		987	Setting the limit to C<0> will pause the feeding process.
640		988
641	=back	989	=back
642		990
643	=head2 SUPPORT FUNCTIONS	991	=head2 SUPPORT FUNCTIONS
		992
		993	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
644		994
645	=over 4	995	=over 4
646		996
647	=item $fileno = IO::AIO::poll_fileno	997	=item $fileno = IO::AIO::poll_fileno
648		998
…		…
653		1003
654	See C<poll_cb> for an example.	1004	See C<poll_cb> for an example.
655		1005
656	=item IO::AIO::poll_cb	1006	=item IO::AIO::poll_cb
657		1007
658	Process all outstanding events on the result pipe. You have to call this	1008	Process some outstanding events on the result pipe. You have to call this
659	regularly. Returns the number of events processed. Returns immediately	1009	regularly. Returns the number of events processed. Returns immediately
660	when no events are outstanding.	1010	when no events are outstanding. The amount of events processed depends on
		1011	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1012
		1013	If not all requests were processed for whatever reason, the filehandle
		1014	will still be ready when C<poll_cb> returns.
661		1015
662	Example: Install an Event watcher that automatically calls	1016	Example: Install an Event watcher that automatically calls
663	IO::AIO::poll_cb with high priority:	1017	IO::AIO::poll_cb with high priority:
664		1018
665	Event->io (fd => IO::AIO::poll_fileno,	1019	Event->io (fd => IO::AIO::poll_fileno,
666	poll => 'r', async => 1,	1020	poll => 'r', async => 1,
667	cb => \&IO::AIO::poll_cb);	1021	cb => \&IO::AIO::poll_cb);
668		1022
		1023	=item IO::AIO::max_poll_reqs $nreqs
		1024
		1025	=item IO::AIO::max_poll_time $seconds
		1026
		1027	These set the maximum number of requests (default C<0>, meaning infinity)
		1028	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1029	the maximum amount of time (default C<0>, meaning infinity) spent in
		1030	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1031	of time C<poll_cb> is allowed to use).
		1032
		1033	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1034	syscall per request processed, which is not normally a problem unless your
		1035	callbacks are really really fast or your OS is really really slow (I am
		1036	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1037
		1038	Setting these is useful if you want to ensure some level of
		1039	interactiveness when perl is not fast enough to process all requests in
		1040	time.
		1041
		1042	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1043
		1044	Example: Install an Event watcher that automatically calls
		1045	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1046	program get the CPU sometimes even under high AIO load.
		1047
		1048	# try not to spend much more than 0.1s in poll_cb
		1049	IO::AIO::max_poll_time 0.1;
		1050
		1051	# use a low priority so other tasks have priority
		1052	Event->io (fd => IO::AIO::poll_fileno,
		1053	poll => 'r', nice => 1,
		1054	cb => &IO::AIO::poll_cb);
		1055
669	=item IO::AIO::poll_wait	1056	=item IO::AIO::poll_wait
670		1057
		1058	If there are any outstanding requests and none of them in the result
671	Wait till the result filehandle becomes ready for reading (simply does a	1059	phase, wait till the result filehandle becomes ready for reading (simply
672	C<select> on the filehandle. This is useful if you want to synchronously wait	1060	does a C<select> on the filehandle. This is useful if you want to
673	for some requests to finish).	1061	synchronously wait for some requests to finish).
674		1062
675	See C<nreqs> for an example.	1063	See C<nreqs> for an example.
676		1064
		1065	=item IO::AIO::poll
		1066
		1067	Waits until some requests have been handled.
		1068
		1069	Returns the number of requests processed, but is otherwise strictly
		1070	equivalent to:
		1071
		1072	IO::AIO::poll_wait, IO::AIO::poll_cb
		1073
677	=item IO::AIO::nreqs	1074	=item IO::AIO::flush
678		1075
679	Returns the number of requests currently outstanding (i.e. for which their	1076	Wait till all outstanding AIO requests have been handled.
680	callback has not been invoked yet).
681		1077
682	Example: wait till there are no outstanding requests anymore:	1078	Strictly equivalent to:
683		1079
684	IO::AIO::poll_wait, IO::AIO::poll_cb	1080	IO::AIO::poll_wait, IO::AIO::poll_cb
685	while IO::AIO::nreqs;	1081	while IO::AIO::nreqs;
686		1082
687	=item IO::AIO::flush	1083	=back
688		1084
689	Wait till all outstanding AIO requests have been handled.	1085	=head3 CONTROLLING THE NUMBER OF THREADS
690
691	Strictly equivalent to:
692
693	IO::AIO::poll_wait, IO::AIO::poll_cb
694	while IO::AIO::nreqs;
695
696	=item IO::AIO::poll
697
698	Waits until some requests have been handled.
699
700	Strictly equivalent to:
701
702	IO::AIO::poll_wait, IO::AIO::poll_cb
703	if IO::AIO::nreqs;
704		1086
705	=item IO::AIO::min_parallel $nthreads	1087	=item IO::AIO::min_parallel $nthreads
706		1088
707	Set the minimum number of AIO threads to C<$nthreads>. The current default	1089	Set the minimum number of AIO threads to C<$nthreads>. The current
708	is C<4>, which means four asynchronous operations can be done at one time	1090	default is C<8>, which means eight asynchronous operations can execute
709	(the number of outstanding operations, however, is unlimited).	1091	concurrently at any one time (the number of outstanding requests,
		1092	however, is unlimited).
710		1093
711	IO::AIO starts threads only on demand, when an AIO request is queued and	1094	IO::AIO starts threads only on demand, when an AIO request is queued and
712	no free thread exists.	1095	no free thread exists. Please note that queueing up a hundred requests can
		1096	create demand for a hundred threads, even if it turns out that everything
		1097	is in the cache and could have been processed faster by a single thread.
713		1098
714	It is recommended to keep the number of threads low, as some Linux	1099	It is recommended to keep the number of threads relatively low, as some
715	kernel versions will scale negatively with the number of threads (higher	1100	Linux kernel versions will scale negatively with the number of threads
716	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1101	(higher parallelity => MUCH higher latency). With current Linux 2.6
717	threads should be fine.	1102	versions, 4-32 threads should be fine.
718		1103
719	Under most circumstances you don't need to call this function, as the	1104	Under most circumstances you don't need to call this function, as the
720	module selects a default that is suitable for low to moderate load.	1105	module selects a default that is suitable for low to moderate load.
721		1106
722	=item IO::AIO::max_parallel $nthreads	1107	=item IO::AIO::max_parallel $nthreads
…		…
731	This module automatically runs C<max_parallel 0> at program end, to ensure	1116	This module automatically runs C<max_parallel 0> at program end, to ensure
732	that all threads are killed and that there are no outstanding requests.	1117	that all threads are killed and that there are no outstanding requests.
733		1118
734	Under normal circumstances you don't need to call this function.	1119	Under normal circumstances you don't need to call this function.
735		1120
		1121	=item IO::AIO::max_idle $nthreads
		1122
		1123	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1124	threads that did not get a request to process within 10 seconds). That
		1125	means if a thread becomes idle while C<$nthreads> other threads are also
		1126	idle, it will free its resources and exit.
		1127
		1128	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1129	to allow for extremely high load situations, but want to free resources
		1130	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1131
		1132	The default is probably ok in most situations, especially if thread
		1133	creation is fast. If thread creation is very slow on your system you might
		1134	want to use larger values.
		1135
736	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1136	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1137
		1138	This is a very bad function to use in interactive programs because it
		1139	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1140	use an C<aio_group> together with a feed callback.
737		1141
738	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1142	Sets the maximum number of outstanding requests to C<$nreqs>. If you
739	try to queue up more than this number of requests, the caller will block until	1143	to queue up more than this number of requests, the next call to the
740	some requests have been handled.	1144	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1145	function will block until the limit is no longer exceeded.
741		1146
742	The default is very large, so normally there is no practical limit. If you	1147	The default value is very large, so there is no practical limit on the
743	queue up many requests in a loop it often improves speed if you set	1148	number of outstanding requests.
744	this to a relatively low number, such as C<100>.
745		1149
746	Under normal circumstances you don't need to call this function.	1150	You can still queue as many requests as you want. Therefore,
		1151	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1152	as a stop gap to shield against fatal memory overflow (with large values).
		1153
		1154	=back
		1155
		1156	=head3 STATISTICAL INFORMATION
		1157
		1158	=over
		1159
		1160	=item IO::AIO::nreqs
		1161
		1162	Returns the number of requests currently in the ready, execute or pending
		1163	states (i.e. for which their callback has not been invoked yet).
		1164
		1165	Example: wait till there are no outstanding requests anymore:
		1166
		1167	IO::AIO::poll_wait, IO::AIO::poll_cb
		1168	while IO::AIO::nreqs;
		1169
		1170	=item IO::AIO::nready
		1171
		1172	Returns the number of requests currently in the ready state (not yet
		1173	executed).
		1174
		1175	=item IO::AIO::npending
		1176
		1177	Returns the number of requests currently in the pending state (executed,
		1178	but not yet processed by poll_cb).
747		1179
748	=back	1180	=back
749		1181
750	=cut	1182	=cut
751		1183
…		…
763	or return undef;	1195	or return undef;
764		1196
765	*$sym	1197	*$sym
766	}	1198	}
767		1199
768	min_parallel 4;	1200	min_parallel 8;
769		1201
770	END {	1202	END { flush }
771	max_parallel 0;
772	}
773		1203
774	1;	1204	1;
775		1205
776	=head2 FORK BEHAVIOUR	1206	=head2 FORK BEHAVIOUR
777		1207
778	This module should do "the right thing" when the process using it forks:	1208	This module should do "the right thing" when the process using it forks:
779		1209
780	Before the fork, IO::AIO enters a quiescent state where no requests	1210	Before the fork, IO::AIO enters a quiescent state where no requests
781	can be added in other threads and no results will be processed. After	1211	can be added in other threads and no results will be processed. After
782	the fork the parent simply leaves the quiescent state and continues	1212	the fork the parent simply leaves the quiescent state and continues
783	request/result processing, while the child clears the request/result	1213	request/result processing, while the child frees the request/result queue
784	queue (so the requests started before the fork will only be handled in	1214	(so that the requests started before the fork will only be handled in the
785	the parent). Threads will be started on demand until the limit ste in the	1215	parent). Threads will be started on demand until the limit set in the
786	parent process has been reached again.	1216	parent process has been reached again.
787		1217
788	In short: the parent will, after a short pause, continue as if fork had	1218	In short: the parent will, after a short pause, continue as if fork had
789	not been called, while the child will act as if IO::AIO has not been used	1219	not been called, while the child will act as if IO::AIO has not been used
790	yet.	1220	yet.
791		1221
		1222	=head2 MEMORY USAGE
		1223
		1224	Per-request usage:
		1225
		1226	Each aio request uses - depending on your architecture - around 100-200
		1227	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1228	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1229	scalars and other data passed into aio requests will also be locked and
		1230	will consume memory till the request has entered the done state.
		1231
		1232	This is now awfully much, so queuing lots of requests is not usually a
		1233	problem.
		1234
		1235	Per-thread usage:
		1236
		1237	In the execution phase, some aio requests require more memory for
		1238	temporary buffers, and each thread requires a stack and other data
		1239	structures (usually around 16k-128k, depending on the OS).
		1240
		1241	=head1 KNOWN BUGS
		1242
		1243	Known bugs will be fixed in the next release.
		1244
792	=head1 SEE ALSO	1245	=head1 SEE ALSO
793		1246
794	L<Coro>, L<Linux::AIO> (obsolete).	1247	L<Coro::AIO>.
795		1248
796	=head1 AUTHOR	1249	=head1 AUTHOR
797		1250
798	Marc Lehmann <schmorp@schmorp.de>	1251	Marc Lehmann <schmorp@schmorp.de>
799	http://home.schmorp.de/	1252	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.58 by root, Sun Oct 22 10:33:19 2006 UTC vs. Revision 1.104 by root, Sat Mar 24 19:19:11 2007 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.58 by root, Sun Oct 22 10:33:19 2006 UTC vs.
Revision 1.104 by root, Sat Mar 24 19:19:11 2007 UTC