[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 1.34 by root, Thu Aug 18 16:32:10 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 = 1.5;
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,$callback
173		149
174	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	150	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
175	into the scalar given by C<data> and offset C<dataoffset> and calls the	151	into the scalar given by C<data> and offset C<dataoffset> and calls the
176	callback without the actual number of bytes read (or -1 on error, just	152	callback without the actual number of bytes read (or -1 on error, just
177	like the syscall).	153	like the syscall).
178		154
		155	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		156	is outstanding. Modifying it can result in segfaults or WW3 (if the
		157	necessary/optional hardware is installed).
		158
179	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	159	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
180	offset C<0> within the scalar:	160	offset C<0> within the scalar:
181		161
182	aio_read $fh, 7, 15, $buffer, 0, sub {	162	aio_read $fh, 7, 15, $buffer, 0, sub {
183	$_[0] >= 0 or die "read error: $!";	163	$_[0] > 0 or die "read error: $!";
184	print "read <$buffer>\n";	164	print "read $_[0] bytes: <$buffer>\n";
185	};	165	};
186		166
187	=item aio_readahead $fh,$offset,$length, $callback	167	=item aio_readahead $fh,$offset,$length, $callback
188		168
189	Asynchronously reads the specified byte range into the page cache, using
190	the C<readahead> syscall. If that syscall doesn't exist the status will be
191	C<-1> and C<$!> is set to ENOSYS.
192
193	readahead() populates the page cache with data from a file so that	169	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<$offset>	170	subsequent reads from that file will not block on disk I/O. The C<$offset>
195	argument specifies the starting point from which data is to be read and	171	argument specifies the starting point from which data is to be read and
196	C<$length> specifies the number of bytes to be read. I/O is performed in	172	C<$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	173	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	174	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	175	(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.	176	file. The current file offset of the file is left unchanged.
		177
		178	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		179	emulated by simply reading the data, which would have a similar effect.
201		180
202	=item aio_stat $fh_or_path, $callback	181	=item aio_stat $fh_or_path, $callback
203		182
204	=item aio_lstat $fh, $callback	183	=item aio_lstat $fh, $callback
205		184
…		…
224	=item aio_unlink $pathname, $callback	203	=item aio_unlink $pathname, $callback
225		204
226	Asynchronously unlink (delete) a file and call the callback with the	205	Asynchronously unlink (delete) a file and call the callback with the
227	result code.	206	result code.
228		207
		208	=item aio_rmdir $pathname, $callback
		209
		210	Asynchronously rmdir (delete) a directory and call the callback with the
		211	result code.
		212
229	=item aio_fsync $fh, $callback	213	=item aio_fsync $fh, $callback
230		214
231	Asynchronously call fsync on the given filehandle and call the callback	215	Asynchronously call fsync on the given filehandle and call the callback
232	with the fsync result code.	216	with the fsync result code.
233		217
234	=item aio_fdatasync $fh, $callback	218	=item aio_fdatasync $fh, $callback
235		219
236	Asynchronously call fdatasync on the given filehandle and call the	220	Asynchronously call fdatasync on the given filehandle and call the
237	callback with the fdatasync result code.	221	callback with the fdatasync result code.
		222
		223	If this call isn't available because your OS lacks it or it couldn't be
		224	detected, it will be emulated by calling C<fsync> instead.
		225
		226	=back
		227
		228	=head2 SUPPORT FUNCTIONS
		229
		230	=over 4
		231
		232	=item $fileno = IO::AIO::poll_fileno
		233
		234	Return the I<request result pipe file descriptor>. This filehandle must be
		235	polled for reading by some mechanism outside this module (e.g. Event or
		236	select, see below or the SYNOPSIS). If the pipe becomes readable you have
		237	to call C<poll_cb> to check the results.
		238
		239	See C<poll_cb> for an example.
		240
		241	=item IO::AIO::poll_cb
		242
		243	Process all outstanding events on the result pipe. You have to call this
		244	regularly. Returns the number of events processed. Returns immediately
		245	when no events are outstanding.
		246
		247	Example: Install an Event watcher that automatically calls
		248	IO::AIO::poll_cb with high priority:
		249
		250	Event->io (fd => IO::AIO::poll_fileno,
		251	poll => 'r', async => 1,
		252	cb => \&IO::AIO::poll_cb);
		253
		254	=item IO::AIO::poll_wait
		255
		256	Wait till the result filehandle becomes ready for reading (simply does a
		257	C<select> on the filehandle. This is useful if you want to synchronously wait
		258	for some requests to finish).
		259
		260	See C<nreqs> for an example.
		261
		262	=item IO::AIO::nreqs
		263
		264	Returns the number of requests currently outstanding (i.e. for which their
		265	callback has not been invoked yet).
		266
		267	Example: wait till there are no outstanding requests anymore:
		268
		269	IO::AIO::poll_wait, IO::AIO::poll_cb
		270	while IO::AIO::nreqs;
		271
		272	=item IO::AIO::flush
		273
		274	Wait till all outstanding AIO requests have been handled.
		275
		276	Strictly equivalent to:
		277
		278	IO::AIO::poll_wait, IO::AIO::poll_cb
		279	while IO::AIO::nreqs;
		280
		281	=item IO::AIO::poll
		282
		283	Waits until some requests have been handled.
		284
		285	Strictly equivalent to:
		286
		287	IO::AIO::poll_wait, IO::AIO::poll_cb
		288	if IO::AIO::nreqs;
		289
		290	=item IO::AIO::min_parallel $nthreads
		291
		292	Set the minimum number of AIO threads to C<$nthreads>. The current default
		293	is C<4>, which means four asynchronous operations can be done at one time
		294	(the number of outstanding operations, however, is unlimited).
		295
		296	IO::AIO starts threads only on demand, when an AIO request is queued and
		297	no free thread exists.
		298
		299	It is recommended to keep the number of threads low, as some Linux
		300	kernel versions will scale negatively with the number of threads (higher
		301	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
		302	threads should be fine.
		303
		304	Under most circumstances you don't need to call this function, as the
		305	module selects a default that is suitable for low to moderate load.
		306
		307	=item IO::AIO::max_parallel $nthreads
		308
		309	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		310	specified number of threads are currently running, this function kills
		311	them. This function blocks until the limit is reached.
		312
		313	While C<$nthreads> are zero, aio requests get queued but not executed
		314	until the number of threads has been increased again.
		315
		316	This module automatically runs C<max_parallel 0> at program end, to ensure
		317	that all threads are killed and that there are no outstanding requests.
		318
		319	Under normal circumstances you don't need to call this function.
		320
		321	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		322
		323	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		324	try to queue up more than this number of requests, the caller will block until
		325	some requests have been handled.
		326
		327	The default is very large, so normally there is no practical limit. If you
		328	queue up many requests in a loop it often improves speed if you set
		329	this to a relatively low number, such as C<100>.
		330
		331	Under normal circumstances you don't need to call this function.
		332
		333	=back
238		334
239	=cut	335	=cut
240		336
241	# support function to convert a fd into a perl filehandle	337	# support function to convert a fd into a perl filehandle
242	sub _fd2fh {	338	sub _fd2fh {
243	return undef if $_[0] < 0;	339	return undef if $_[0] < 0;
244		340
245	# try to be perl5.6-compatible	341	# try to generate nice filehandles
246	local *AIO_FH;	342	my $sym = "IO::AIO::fd#$_[0]";
247	open AIO_FH, "+<&=$_[0]"	343	local *$sym;
		344
		345	open *$sym, "+<&=$_[0]" # usually works under any unix
		346	or open *$sym, "<&=$_[0]" # cygwin needs this
		347	or open *$sym, ">&=$_[0]" # or this
248	or return undef;	348	or return undef;
249		349
250	*AIO_FH	350	*$sym
251	}	351	}
252		352
253	min_parallel 4;	353	min_parallel 4;
254		354
255	END {	355	END {
256	max_parallel 0;	356	max_parallel 0;
257	}	357	}
258		358
259	1;	359	1;
260		360
261	=back	361	=head2 FORK BEHAVIOUR
262		362
263	=head1 BUGS	363	Before the fork, IO::AIO enters a quiescent state where no requests
264		364	can be added in other threads and no results will be processed. After
265	- could be optimized to use more semaphores instead of filehandles.	365	the fork the parent simply leaves the quiescent state and continues
		366	request/result processing, while the child clears the request/result
		367	queue (so the requests started before the fork will only be handled in
		368	the parent). Threats will be started on demand until the limit ste in the
		369	parent process has been reached again.
266		370
267	=head1 SEE ALSO	371	=head1 SEE ALSO
268		372
269	L<Coro>, L<Linux::AIO>.	373	L<Coro>, L<Linux::AIO>.
270		374

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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 1.34 by root, Thu Aug 18 16:32:10 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 1.34 by root, Thu Aug 18 16:32:10 2005 UTC