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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.4 by root, Sun Jul 10 20:57:00 2005 UTC vs.
Revision 1.30 by root, Wed Aug 17 04:47:38 2005 UTC

…		…
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
		8
		9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		10	my ($fh) = @_;
		11	...
		12	};
		13
		14	aio_unlink "/tmp/file", sub { };
		15
		16	aio_read $fh, 30000, 1024, $buffer, 0, sub {
		17	$_[0] > 0 or die "read error: $!";
		18	};
		19
		20	# Event
		21	Event->io (fd => IO::AIO::poll_fileno,
		22	poll => 'r',
		23	cb => \&IO::AIO::poll_cb);
		24
		25	# Glib/Gtk2
		26	add_watch Glib::IO IO::AIO::poll_fileno,
		27	in => sub { IO::AIO::poll_cb; 1 };
		28
		29	# Tk
		30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		31	readable => \&IO::AIO::poll_cb);
		32
		33	# Danga::Socket
		34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		35	\&IO::AIO::poll_cb);
		36
8		37
9	=head1 DESCRIPTION	38	=head1 DESCRIPTION
10		39
11	This module implements asynchronous I/O using whatever means your	40	This module implements asynchronous I/O using whatever means your
12	operating system supports.	41	operating system supports.
…		…
19	not well-supported (Linux doesn't allow them on normal files currently,	48	not well-supported (Linux doesn't allow them on normal files currently,
20	for example), and they would only support aio_read and aio_write, so the	49	for example), and they would only support aio_read and aio_write, so the
21	remaining functionality would have to be implemented using threads anyway.	50	remaining functionality would have to be implemented using threads anyway.
22		51
23	Although the module will work with in the presence of other threads, it is	52	Although the module will work with in the presence of other threads, it is
24	currently not reentrant, so use appropriate locking yourself.	53	currently not reentrant, so use appropriate locking yourself, always call
25		54	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other
26	=head2 API NOTES	55	C<aio_> functions) recursively.
27
28	All the C<aio_*> calls are more or less thin wrappers around the syscall
29	with the same name (sans C<aio_>). The arguments are similar or identical,
30	and they all accept an additional C<$callback> argument which must be
31	a code reference. This code reference will get called with the syscall
32	return code (e.g. most syscalls return C<-1> on error, unlike perl, which
33	usually delivers "false") as it's sole argument when the given syscall has
34	been executed asynchronously.
35
36	All functions that expect a filehandle will also accept a file descriptor.
37
38	The filenames you pass to these routines I<must> be absolute. The reason
39	is that at the time the request is being executed, the current working
40	directory could have changed. Alternatively, you can make sure that you
41	never change the current working directory.
42
43	=over 4
44		56
45	=cut	57	=cut
46		58
47	package IO::AIO;	59	package IO::AIO;
48		60
		61	no warnings;
		62
49	use base 'Exporter';	63	use base 'Exporter';
50		64
51	use Fcntl ();	65	use Fcntl ();
52		66
53	BEGIN {	67	BEGIN {
54	$VERSION = 0.2;	68	$VERSION = 1.2;
55		69
56	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	70	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink
57	aio_fsync aio_fdatasync aio_readahead);	71	aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead);
58	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	72	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
59		73
60	require XSLoader;	74	require XSLoader;
61	XSLoader::load IO::AIO, $VERSION;	75	XSLoader::load IO::AIO, $VERSION;
62	}	76	}
63		77
64	=item IO::AIO::min_parallel $nthreads	78	=head1 FUNCTIONS
65		79
66	Set the minimum number of AIO threads to C<$nthreads>. The default is	80	=head2 AIO FUNCTIONS
67	C<1>, which means a single asynchronous operation can be done at one time
68	(the number of outstanding operations, however, is unlimited).
69		81
70	It is recommended to keep the number of threads low, as some Linux	82	All the C<aio_*> calls are more or less thin wrappers around the syscall
71	kernel versions will scale negatively with the number of threads (higher	83	with the same name (sans C<aio_>). The arguments are similar or identical,
72	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	84	and they all accept an additional (and optional) C<$callback> argument
73	threads should be fine.	85	which must be a code reference. This code reference will get called with
		86	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
		87	perl, which usually delivers "false") as it's sole argument when the given
		88	syscall has been executed asynchronously.
74		89
75	Under normal circumstances you don't need to call this function, as this	90	All functions expecting a filehandle keep a copy of the filehandle
76	module automatically starts some threads (the exact number might change,	91	internally until the request has finished.
77	and is currently 4).
78		92
79	=item IO::AIO::max_parallel $nthreads	93	The pathnames you pass to these routines I<must> be absolute and
		94	encoded in byte form. The reason for the former is that at the time the
		95	request is being executed, the current working directory could have
		96	changed. Alternatively, you can make sure that you never change the
		97	current working directory.
80		98
81	Sets the maximum number of AIO threads to C<$nthreads>. If more than	99	To encode pathnames to byte form, either make sure you either: a)
82	the specified number of threads are currently running, kill them. This	100	always pass in filenames you got from outside (command line, readdir
83	function blocks until the limit is reached.	101	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		102	your pathnames to the locale (or other) encoding in effect in the user
		103	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		104	use something else.
84		105
85	This module automatically runs C<max_parallel 0> at program end, to ensure	106	=over 4
86	that all threads are killed and that there are no outstanding requests.
87
88	Under normal circumstances you don't need to call this function.
89
90	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
91
92	Sets the maximum number of outstanding requests to C<$nreqs>. If you
93	try to queue up more than this number of requests, the caller will block until
94	some requests have been handled.
95
96	The default is very large, so normally there is no practical limit. If you
97	queue up many requests in a loop it it often improves speed if you set
98	this to a relatively low number, such as C<100>.
99
100	Under normal circumstances you don't need to call this function.
101
102	=item $fileno = IO::AIO::poll_fileno
103
104	Return the I<request result pipe filehandle>. This filehandle must be
105	polled for reading by some mechanism outside this module (e.g. Event
106	or select, see below). If the pipe becomes readable you have to call
107	C<poll_cb> to check the results.
108
109	See C<poll_cb> for an example.
110
111	=item IO::AIO::poll_cb
112
113	Process all outstanding events on the result pipe. You have to call this
114	regularly. Returns the number of events processed. Returns immediately
115	when no events are outstanding.
116
117	You can use Event to multiplex, e.g.:
118
119	Event->io (fd => IO::AIO::poll_fileno,
120	poll => 'r', async => 1,
121	cb => \&IO::AIO::poll_cb);
122
123	=item IO::AIO::poll_wait
124
125	Wait till the result filehandle becomes ready for reading (simply does a
126	select on the filehandle. This is useful if you want to synchronously wait
127	for some requests to finish).
128
129	See C<nreqs> for an example.
130
131	=item IO::AIO::nreqs
132
133	Returns the number of requests currently outstanding.
134
135	Example: wait till there are no outstanding requests anymore:
136
137	IO::AIO::poll_wait, IO::AIO::poll_cb
138	while IO::AIO::nreqs;
139		107
140	=item aio_open $pathname, $flags, $mode, $callback	108	=item aio_open $pathname, $flags, $mode, $callback
141		109
142	Asynchronously open or create a file and call the callback with a newly	110	Asynchronously open or create a file and call the callback with a newly
143	created filehandle for the file.	111	created filehandle for the file.
144		112
145	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	113	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
146	for an explanation.	114	for an explanation.
147		115
148	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	116	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
149	list. They are the same as used in C<sysopen>.	117	list. They are the same as used by C<sysopen>.
		118
		119	Likewise, C<$mode> specifies the mode of the newly created file, if it
		120	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		121	except that it is mandatory (i.e. use C<0> if you don't create new files,
		122	and C<0666> or C<0777> if you do).
150		123
151	Example:	124	Example:
152		125
153	aio_open "/etc/passwd", O_RDONLY, 0, sub {	126	aio_open "/etc/passwd", O_RDONLY, 0, sub {
154	if ($_[0]) {	127	if ($_[0]) {
…		…
161		134
162	=item aio_close $fh, $callback	135	=item aio_close $fh, $callback
163		136
164	Asynchronously close a file and call the callback with the result	137	Asynchronously close a file and call the callback with the result
165	code. I<WARNING:> although accepted, you should not pass in a perl	138	code. I<WARNING:> although accepted, you should not pass in a perl
166	filehandle here, as perl will likely close the file descriptor itself when	139	filehandle here, as perl will likely close the file descriptor another
167	the filehandle is destroyed. Normally, you can safely call perls C<close>	140	time when the filehandle is destroyed. Normally, you can safely call perls
168	or just let filehandles go out of scope.	141	C<close> or just let filehandles go out of scope.
		142
		143	This is supposed to be a bug in the API, so that might change. It's
		144	therefore best to avoid this function.
169		145
170	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	146	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback
171		147
172	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	148	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback
173		149
174	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	150	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
175	into the scalar given by C<data> and offset C<dataoffset> and calls the	151	into the scalar given by C<data> and offset C<dataoffset> and calls the
176	callback without the actual number of bytes read (or -1 on error, just	152	callback without the actual number of bytes read (or -1 on error, just
177	like the syscall).	153	like the syscall).
178		154
179	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	155	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
180	offset C<0> within the scalar:	156	offset C<0> within the scalar:
181		157
182	aio_read $fh, 7, 15, $buffer, 0, sub {	158	aio_read $fh, 7, 15, $buffer, 0, sub {
183	$_[0] >= 0 or die "read error: $!";	159	$_[0] > 0 or die "read error: $!";
184	print "read <$buffer>\n";	160	print "read $_[0] bytes: <$buffer>\n";
185	};	161	};
186		162
187	=item aio_readahead $fh,$offset,$length, $callback	163	=item aio_readahead $fh,$offset,$length, $callback
188		164
189	Asynchronously reads the specified byte range into the page cache, using
190	the C<readahead> syscall. If that syscall doesn't exist the status will be
191	C<-1> and C<$!> is set to ENOSYS.
192
193	readahead() populates the page cache with data from a file so that	165	C<aio_readahead> populates the page cache with data from a file so that
194	subsequent reads from that file will not block on disk I/O. The C<$offset>	166	subsequent reads from that file will not block on disk I/O. The C<$offset>
195	argument specifies the starting point from which data is to be read and	167	argument specifies the starting point from which data is to be read and
196	C<$length> specifies the number of bytes to be read. I/O is performed in	168	C<$length> specifies the number of bytes to be read. I/O is performed in
197	whole pages, so that offset is effectively rounded down to a page boundary	169	whole pages, so that offset is effectively rounded down to a page boundary
198	and bytes are read up to the next page boundary greater than or equal to	170	and bytes are read up to the next page boundary greater than or equal to
199	(off-set+length). aio_readahead() does not read beyond the end of the	171	(off-set+length). C<aio_readahead> does not read beyond the end of the
200	file. The current file offset of the file is left unchanged.	172	file. The current file offset of the file is left unchanged.
		173
		174	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		175	emulated by simply reading the data, which would have a similar effect.
201		176
202	=item aio_stat $fh_or_path, $callback	177	=item aio_stat $fh_or_path, $callback
203		178
204	=item aio_lstat $fh, $callback	179	=item aio_lstat $fh, $callback
205		180
…		…
224	=item aio_unlink $pathname, $callback	199	=item aio_unlink $pathname, $callback
225		200
226	Asynchronously unlink (delete) a file and call the callback with the	201	Asynchronously unlink (delete) a file and call the callback with the
227	result code.	202	result code.
228		203
		204	=item aio_rmdir $pathname, $callback
		205
		206	Asynchronously rmdir (delete) a directory and call the callback with the
		207	result code.
		208
229	=item aio_fsync $fh, $callback	209	=item aio_fsync $fh, $callback
230		210
231	Asynchronously call fsync on the given filehandle and call the callback	211	Asynchronously call fsync on the given filehandle and call the callback
232	with the fsync result code.	212	with the fsync result code.
233		213
234	=item aio_fdatasync $fh, $callback	214	=item aio_fdatasync $fh, $callback
235		215
236	Asynchronously call fdatasync on the given filehandle and call the	216	Asynchronously call fdatasync on the given filehandle and call the
237	callback with the fdatasync result code.	217	callback with the fdatasync result code.
		218
		219	If this call isn't available because your OS lacks it or it couldn't be
		220	detected, it will be emulated by calling C<fsync> instead.
		221
		222	=back
		223
		224	=head2 SUPPORT FUNCTIONS
		225
		226	=over 4
		227
		228	=item $fileno = IO::AIO::poll_fileno
		229
		230	Return the I<request result pipe file descriptor>. This filehandle must be
		231	polled for reading by some mechanism outside this module (e.g. Event or
		232	select, see below or the SYNOPSIS). If the pipe becomes readable you have
		233	to call C<poll_cb> to check the results.
		234
		235	See C<poll_cb> for an example.
		236
		237	=item IO::AIO::poll_cb
		238
		239	Process all outstanding events on the result pipe. You have to call this
		240	regularly. Returns the number of events processed. Returns immediately
		241	when no events are outstanding.
		242
		243	Example: Install an Event watcher that automatically calls
		244	IO::AIO::poll_cb with high priority:
		245
		246	Event->io (fd => IO::AIO::poll_fileno,
		247	poll => 'r', async => 1,
		248	cb => \&IO::AIO::poll_cb);
		249
		250	=item IO::AIO::poll_wait
		251
		252	Wait till the result filehandle becomes ready for reading (simply does a
		253	C<select> on the filehandle. This is useful if you want to synchronously wait
		254	for some requests to finish).
		255
		256	See C<nreqs> for an example.
		257
		258	=item IO::AIO::nreqs
		259
		260	Returns the number of requests currently outstanding (i.e. for which their
		261	callback has not been invoked yet).
		262
		263	Example: wait till there are no outstanding requests anymore:
		264
		265	IO::AIO::poll_wait, IO::AIO::poll_cb
		266	while IO::AIO::nreqs;
		267
		268	=item IO::AIO::flush
		269
		270	Wait till all outstanding AIO requests have been handled.
		271
		272	Strictly equivalent to:
		273
		274	IO::AIO::poll_wait, IO::AIO::poll_cb
		275	while IO::AIO::nreqs;
		276
		277	=item IO::AIO::poll
		278
		279	Waits until some requests have been handled.
		280
		281	Strictly equivalent to:
		282
		283	IO::AIO::poll_wait, IO::AIO::poll_cb
		284	if IO::AIO::nreqs;
		285
		286	=item IO::AIO::min_parallel $nthreads
		287
		288	Set the minimum number of AIO threads to C<$nthreads>. The default is
		289	C<1>, which means a single asynchronous operation can be done at one time
		290	(the number of outstanding operations, however, is unlimited).
		291
		292	It is recommended to keep the number of threads low, as some Linux
		293	kernel versions will scale negatively with the number of threads (higher
		294	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
		295	threads should be fine.
		296
		297	Under normal circumstances you don't need to call this function, as this
		298	module automatically starts some threads (the exact number might change,
		299	and is currently 4).
		300
		301	=item IO::AIO::max_parallel $nthreads
		302
		303	Sets the maximum number of AIO threads to C<$nthreads>. If more than
		304	the specified number of threads are currently running, kill them. This
		305	function blocks until the limit is reached.
		306
		307	This module automatically runs C<max_parallel 0> at program end, to ensure
		308	that all threads are killed and that there are no outstanding requests.
		309
		310	Under normal circumstances you don't need to call this function.
		311
		312	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		313
		314	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		315	try to queue up more than this number of requests, the caller will block until
		316	some requests have been handled.
		317
		318	The default is very large, so normally there is no practical limit. If you
		319	queue up many requests in a loop it it often improves speed if you set
		320	this to a relatively low number, such as C<100>.
		321
		322	Under normal circumstances you don't need to call this function.
		323
		324	=back
238		325
239	=cut	326	=cut
240		327
241	# support function to convert a fd into a perl filehandle	328	# support function to convert a fd into a perl filehandle
242	sub _fd2fh {	329	sub _fd2fh {
243	return undef if $_[0] < 0;	330	return undef if $_[0] < 0;
244		331
245	# try to be perl5.6-compatible	332	# try to generate nice filehandles
246	local *AIO_FH;	333	my $sym = "IO::AIO::fd#$_[0]";
247	open AIO_FH, "+<&=$_[0]"	334	local *$sym;
		335
		336	open *$sym, "+<&=$_[0]" # usually works under any unix
		337	or open *$sym, "<&=$_[0]" # cygwin needs this
		338	or open *$sym, ">&=$_[0]" # or this
248	or return undef;	339	or return undef;
249		340
250	*AIO_FH	341	*$sym
251	}	342	}
252		343
253	min_parallel 4;	344	min_parallel 4;
254		345
255	END {	346	END {
256	max_parallel 0;	347	max_parallel 0;
257	}	348	}
258		349
259	1;	350	1;
260		351
261	=back	352	=head2 FORK BEHAVIOUR
262		353
263	=head1 BUGS	354	Before the fork IO::AIO first handles all outstanding requests - if other
264		355	threads add requests during this period, this time is prolonged. It then
265	- could be optimized to use more semaphores instead of filehandles.	356	enters a quiescent state where no requests can be added in other threads
		357	and no results will be processed. After the fork the parent simply leaves
		358	the quiescent state and continues request processing, while the child
		359	starts the same number of threads as were in use by the parent.
266		360
267	=head1 SEE ALSO	361	=head1 SEE ALSO
268		362
269	L<Coro>, L<Linux::AIO>.	363	L<Coro>, L<Linux::AIO>.
270		364

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.4 by root, Sun Jul 10 20:57:00 2005 UTC vs. Revision 1.30 by root, Wed Aug 17 04:47:38 2005 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.4 by root, Sun Jul 10 20:57:00 2005 UTC vs.
Revision 1.30 by root, Wed Aug 17 04:47:38 2005 UTC