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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.3 by root, Sun Jul 10 20:07:11 2005 UTC vs.
Revision 1.39 by root, Sun Aug 28 11:05:50 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 = 1.6;
55		69
56	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	70	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
		71	aio_lstat aio_unlink aio_rmdir aio_readdir aio_symlink
57	aio_fsync aio_fdatasync aio_readahead);	72	aio_fsync aio_fdatasync aio_readahead);
58	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs);	73	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel
		74	max_outstanding nreqs);
59		75
60	require XSLoader;	76	require XSLoader;
61	XSLoader::load IO::AIO, $VERSION;	77	XSLoader::load IO::AIO, $VERSION;
62	}	78	}
63		79
64	=item IO::AIO::min_parallel $nthreads	80	=head1 FUNCTIONS
65		81
66	Set the minimum number of AIO threads to C<$nthreads>. The default is	82	=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		83
70	It is recommended to keep the number of threads low, as some linux	84	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	85	with the same name (sans C<aio_>). The arguments are similar or identical,
72	parallelity => MUCH higher latency).	86	and they all accept an additional (and optional) C<$callback> argument
		87	which must be a code reference. This code reference will get called with
		88	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
		89	perl, which usually delivers "false") as it's sole argument when the given
		90	syscall has been executed asynchronously.
73		91
74	Under normal circumstances you don't need to call this function, as this	92	All functions expecting a filehandle keep a copy of the filehandle
75	module automatically starts a single async thread.	93	internally until the request has finished.
76		94
77	=item IO::AIO::max_parallel $nthreads	95	The pathnames you pass to these routines I<must> be absolute and
		96	encoded in byte form. The reason for the former is that at the time the
		97	request is being executed, the current working directory could have
		98	changed. Alternatively, you can make sure that you never change the
		99	current working directory.
78		100
79	Sets the maximum number of AIO threads to C<$nthreads>. If more than	101	To encode pathnames to byte form, either make sure you either: a)
80	the specified number of threads are currently running, kill them. This	102	always pass in filenames you got from outside (command line, readdir
81	function blocks until the limit is reached.	103	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		104	your pathnames to the locale (or other) encoding in effect in the user
		105	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		106	use something else.
82		107
83	This module automatically runs C<max_parallel 0> at program end, to ensure	108	=over 4
84	that all threads are killed and that there are no outstanding requests.
85
86	Under normal circumstances you don't need to call this function.
87
88	=item $fileno = IO::AIO::poll_fileno
89
90	Return the I<request result pipe filehandle>. This filehandle must be
91	polled for reading by some mechanism outside this module (e.g. Event
92	or select, see below). If the pipe becomes readable you have to call
93	C<poll_cb> to check the results.
94
95	See C<poll_cb> for an example.
96
97	=item IO::AIO::poll_cb
98
99	Process all outstanding events on the result pipe. You have to call this
100	regularly. Returns the number of events processed. Returns immediately
101	when no events are outstanding.
102
103	You can use Event to multiplex, e.g.:
104
105	Event->io (fd => IO::AIO::poll_fileno,
106	poll => 'r', async => 1,
107	cb => \&IO::AIO::poll_cb);
108
109	=item IO::AIO::poll_wait
110
111	Wait till the result filehandle becomes ready for reading (simply does a
112	select on the filehandle. This is useful if you want to synchronously wait
113	for some requests to finish).
114
115	See C<nreqs> for an example.
116
117	=item IO::AIO::nreqs
118
119	Returns the number of requests currently outstanding.
120
121	Example: wait till there are no outstanding requests anymore:
122
123	IO::AIO::poll_wait, IO::AIO::poll_cb
124	while IO::AIO::nreqs;
125		109
126	=item aio_open $pathname, $flags, $mode, $callback	110	=item aio_open $pathname, $flags, $mode, $callback
127		111
128	Asynchronously open or create a file and call the callback with a newly	112	Asynchronously open or create a file and call the callback with a newly
129	created filehandle for the file.	113	created filehandle for the file.
130		114
131	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	115	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
132	for an explanation.	116	for an explanation.
133		117
134	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	118	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
135	list. They are the same as used in C<sysopen>.	119	list. They are the same as used by C<sysopen>.
		120
		121	Likewise, C<$mode> specifies the mode of the newly created file, if it
		122	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		123	except that it is mandatory (i.e. use C<0> if you don't create new files,
		124	and C<0666> or C<0777> if you do).
136		125
137	Example:	126	Example:
138		127
139	aio_open "/etc/passwd", O_RDONLY, 0, sub {	128	aio_open "/etc/passwd", O_RDONLY, 0, sub {
140	if ($_[0]) {	129	if ($_[0]) {
…		…
147		136
148	=item aio_close $fh, $callback	137	=item aio_close $fh, $callback
149		138
150	Asynchronously close a file and call the callback with the result	139	Asynchronously close a file and call the callback with the result
151	code. I<WARNING:> although accepted, you should not pass in a perl	140	code. I<WARNING:> although accepted, you should not pass in a perl
152	filehandle here, as perl will likely close the file descriptor itself when	141	filehandle here, as perl will likely close the file descriptor another
153	the filehandle is destroyed. Normally, you can safely call perls C<close>	142	time when the filehandle is destroyed. Normally, you can safely call perls
154	or just let filehandles go out of scope.	143	C<close> or just let filehandles go out of scope.
		144
		145	This is supposed to be a bug in the API, so that might change. It's
		146	therefore best to avoid this function.
155		147
156	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	148	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback
157		149
158	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	150	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback
159		151
160	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	152	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
161	into the scalar given by C<data> and offset C<dataoffset> and calls the	153	into the scalar given by C<data> and offset C<dataoffset> and calls the
162	callback without the actual number of bytes read (or -1 on error, just	154	callback without the actual number of bytes read (or -1 on error, just
163	like the syscall).	155	like the syscall).
164		156
		157	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		158	is outstanding. Modifying it can result in segfaults or WW3 (if the
		159	necessary/optional hardware is installed).
		160
165	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	161	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
166	offset C<0> within the scalar:	162	offset C<0> within the scalar:
167		163
168	aio_read $fh, 7, 15, $buffer, 0, sub {	164	aio_read $fh, 7, 15, $buffer, 0, sub {
169	$_[0] >= 0 or die "read error: $!";	165	$_[0] > 0 or die "read error: $!";
170	print "read <$buffer>\n";	166	print "read $_[0] bytes: <$buffer>\n";
171	};	167	};
172		168
		169	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback
		170
		171	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		172	reading at byte offset C<$in_offset>, and starts writing at the current
		173	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		174	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		175	other.
		176
		177	This call tries to make use of a native C<sendfile> syscall to provide
		178	zero-copy operation. For this to work, C<$out_fh> should refer to a
		179	socket, and C<$in_fh> should refer to mmap'able file.
		180
		181	If the native sendfile call fails or is not implemented, it will be
		182	emulated, so you can call C<aio_sendfile> on any type of filehandle
		183	regardless of the limitations of the operating system.
		184
		185	Please note, however, that C<aio_sendfile> can read more bytes from
		186	C<$in_fh> than are written, and there is no way to find out how many
		187	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		188	provides the number of bytes written to C<$out_fh>. Only if the result
		189	value equals C<$length> one can assume that C<$length> bytes have been
		190	read.
		191
173	=item aio_readahead $fh,$offset,$length, $callback	192	=item aio_readahead $fh,$offset,$length, $callback
174		193
175	Asynchronously reads the specified byte range into the page cache, using
176	the C<readahead> syscall. If that syscall doesn't exist the status will be
177	C<-1> and C<$!> is set to ENOSYS.
178
179	readahead() populates the page cache with data from a file so that	194	C<aio_readahead> populates the page cache with data from a file so that
180	subsequent reads from that file will not block on disk I/O. The C<$offset>	195	subsequent reads from that file will not block on disk I/O. The C<$offset>
181	argument specifies the starting point from which data is to be read and	196	argument specifies the starting point from which data is to be read and
182	C<$length> specifies the number of bytes to be read. I/O is performed in	197	C<$length> specifies the number of bytes to be read. I/O is performed in
183	whole pages, so that offset is effectively rounded down to a page boundary	198	whole pages, so that offset is effectively rounded down to a page boundary
184	and bytes are read up to the next page boundary greater than or equal to	199	and bytes are read up to the next page boundary greater than or equal to
185	(off-set+length). aio_readahead() does not read beyond the end of the	200	(off-set+length). C<aio_readahead> does not read beyond the end of the
186	file. The current file offset of the file is left unchanged.	201	file. The current file offset of the file is left unchanged.
		202
		203	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		204	emulated by simply reading the data, which would have a similar effect.
187		205
188	=item aio_stat $fh_or_path, $callback	206	=item aio_stat $fh_or_path, $callback
189		207
190	=item aio_lstat $fh, $callback	208	=item aio_lstat $fh, $callback
191		209
…		…
210	=item aio_unlink $pathname, $callback	228	=item aio_unlink $pathname, $callback
211		229
212	Asynchronously unlink (delete) a file and call the callback with the	230	Asynchronously unlink (delete) a file and call the callback with the
213	result code.	231	result code.
214		232
		233	=item aio_rmdir $pathname, $callback
		234
		235	Asynchronously rmdir (delete) a directory and call the callback with the
		236	result code.
		237
		238	=item aio_readdir $pathname $callback
		239
		240	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		241	directory (i.e. opendir + readdir + closedir). The entries will not be
		242	sorted, and will B<NOT> include the C<.> and C<..> entries.
		243
		244	The callback a single argument which is either C<undef> or an array-ref
		245	with the filenames.
		246
215	=item aio_fsync $fh, $callback	247	=item aio_fsync $fh, $callback
216		248
217	Asynchronously call fsync on the given filehandle and call the callback	249	Asynchronously call fsync on the given filehandle and call the callback
218	with the fsync result code.	250	with the fsync result code.
219		251
220	=item aio_fdatasync $fh, $callback	252	=item aio_fdatasync $fh, $callback
221		253
222	Asynchronously call fdatasync on the given filehandle and call the	254	Asynchronously call fdatasync on the given filehandle and call the
223	callback with the fdatasync result code.	255	callback with the fdatasync result code.
		256
		257	If this call isn't available because your OS lacks it or it couldn't be
		258	detected, it will be emulated by calling C<fsync> instead.
		259
		260	=back
		261
		262	=head2 SUPPORT FUNCTIONS
		263
		264	=over 4
		265
		266	=item $fileno = IO::AIO::poll_fileno
		267
		268	Return the I<request result pipe file descriptor>. This filehandle must be
		269	polled for reading by some mechanism outside this module (e.g. Event or
		270	select, see below or the SYNOPSIS). If the pipe becomes readable you have
		271	to call C<poll_cb> to check the results.
		272
		273	See C<poll_cb> for an example.
		274
		275	=item IO::AIO::poll_cb
		276
		277	Process all outstanding events on the result pipe. You have to call this
		278	regularly. Returns the number of events processed. Returns immediately
		279	when no events are outstanding.
		280
		281	Example: Install an Event watcher that automatically calls
		282	IO::AIO::poll_cb with high priority:
		283
		284	Event->io (fd => IO::AIO::poll_fileno,
		285	poll => 'r', async => 1,
		286	cb => \&IO::AIO::poll_cb);
		287
		288	=item IO::AIO::poll_wait
		289
		290	Wait till the result filehandle becomes ready for reading (simply does a
		291	C<select> on the filehandle. This is useful if you want to synchronously wait
		292	for some requests to finish).
		293
		294	See C<nreqs> for an example.
		295
		296	=item IO::AIO::nreqs
		297
		298	Returns the number of requests currently outstanding (i.e. for which their
		299	callback has not been invoked yet).
		300
		301	Example: wait till there are no outstanding requests anymore:
		302
		303	IO::AIO::poll_wait, IO::AIO::poll_cb
		304	while IO::AIO::nreqs;
		305
		306	=item IO::AIO::flush
		307
		308	Wait till all outstanding AIO requests have been handled.
		309
		310	Strictly equivalent to:
		311
		312	IO::AIO::poll_wait, IO::AIO::poll_cb
		313	while IO::AIO::nreqs;
		314
		315	=item IO::AIO::poll
		316
		317	Waits until some requests have been handled.
		318
		319	Strictly equivalent to:
		320
		321	IO::AIO::poll_wait, IO::AIO::poll_cb
		322	if IO::AIO::nreqs;
		323
		324	=item IO::AIO::min_parallel $nthreads
		325
		326	Set the minimum number of AIO threads to C<$nthreads>. The current default
		327	is C<4>, which means four asynchronous operations can be done at one time
		328	(the number of outstanding operations, however, is unlimited).
		329
		330	IO::AIO starts threads only on demand, when an AIO request is queued and
		331	no free thread exists.
		332
		333	It is recommended to keep the number of threads low, as some Linux
		334	kernel versions will scale negatively with the number of threads (higher
		335	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
		336	threads should be fine.
		337
		338	Under most circumstances you don't need to call this function, as the
		339	module selects a default that is suitable for low to moderate load.
		340
		341	=item IO::AIO::max_parallel $nthreads
		342
		343	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		344	specified number of threads are currently running, this function kills
		345	them. This function blocks until the limit is reached.
		346
		347	While C<$nthreads> are zero, aio requests get queued but not executed
		348	until the number of threads has been increased again.
		349
		350	This module automatically runs C<max_parallel 0> at program end, to ensure
		351	that all threads are killed and that there are no outstanding requests.
		352
		353	Under normal circumstances you don't need to call this function.
		354
		355	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		356
		357	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		358	try to queue up more than this number of requests, the caller will block until
		359	some requests have been handled.
		360
		361	The default is very large, so normally there is no practical limit. If you
		362	queue up many requests in a loop it often improves speed if you set
		363	this to a relatively low number, such as C<100>.
		364
		365	Under normal circumstances you don't need to call this function.
		366
		367	=back
224		368
225	=cut	369	=cut
226		370
227	# support function to convert a fd into a perl filehandle	371	# support function to convert a fd into a perl filehandle
228	sub _fd2fh {	372	sub _fd2fh {
229	return undef if $_[0] < 0;	373	return undef if $_[0] < 0;
230		374
231	# try to be perl5.6-compatible	375	# try to generate nice filehandles
232	local *AIO_FH;	376	my $sym = "IO::AIO::fd#$_[0]";
233	open AIO_FH, "+<&=$_[0]"	377	local *$sym;
		378
		379	open *$sym, "+<&=$_[0]" # usually works under any unix
		380	or open *$sym, "<&=$_[0]" # cygwin needs this
		381	or open *$sym, ">&=$_[0]" # or this
234	or return undef;	382	or return undef;
235		383
236	*AIO_FH	384	*$sym
237	}	385	}
238		386
239	min_parallel 4;	387	min_parallel 4;
240		388
241	END {	389	END {
242	max_parallel 0;	390	max_parallel 0;
243	}	391	}
244		392
245	1;	393	1;
246		394
247	=back	395	=head2 FORK BEHAVIOUR
248		396
249	=head1 BUGS	397	Before the fork, IO::AIO enters a quiescent state where no requests
250		398	can be added in other threads and no results will be processed. After
251	- could be optimized to use more semaphores instead of filehandles.	399	the fork the parent simply leaves the quiescent state and continues
		400	request/result processing, while the child clears the request/result
		401	queue (so the requests started before the fork will only be handled in
		402	the parent). Threats will be started on demand until the limit ste in the
		403	parent process has been reached again.
252		404
253	=head1 SEE ALSO	405	=head1 SEE ALSO
254		406
255	L<Coro>, L<Linux::AIO>.	407	L<Coro>, L<Linux::AIO>.
256		408

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.3 by root, Sun Jul 10 20:07:11 2005 UTC vs. Revision 1.39 by root, Sun Aug 28 11:05:50 2005 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.3 by root, Sun Jul 10 20:07:11 2005 UTC vs.
Revision 1.39 by root, Sun Aug 28 11:05:50 2005 UTC