[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 1.36 by root, Tue Aug 23 00:03:14 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_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
		167	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback
		168
		169	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		170	reading at byte offset C<$in_offset>, and starts writing at the current
		171	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		172	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		173	other.
		174
		175	This call tries to make use of a native C<sendfile> syscall to provide
		176	zero-copy operation. For this to work, C<$out_fh> should refer to a
		177	socket, and C<$in_fh> should refer to mmap'able file.
		178
		179	If the native sendfile call fails or is not implemented, it will be
		180	emulated, so you can call C<aio_sendfile> on any type of filehandle
		181	regardless of the limitations of the operating system.
		182
		183	Please note, however, that C<aio_sendfile> can read more bytes from
		184	C<$in_fh> than are written, and there is no way to find out how many
		185	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		186	provides the number of bytes written to C<$out_fh>. Only if the result
		187	value equals C<$length> one can assume that C<$length> bytes have been
		188	read.
		189
187	=item aio_readahead $fh,$offset,$length, $callback	190	=item aio_readahead $fh,$offset,$length, $callback
188		191
189	Asynchronously reads the specified byte range into the page cache, using
190	the C<readahead> syscall. If that syscall doesn't exist the status will be
191	C<-1> and C<$!> is set to ENOSYS.
192
193	readahead() populates the page cache with data from a file so that	192	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<$offset>	193	subsequent reads from that file will not block on disk I/O. The C<$offset>
195	argument specifies the starting point from which data is to be read and	194	argument specifies the starting point from which data is to be read and
196	C<$length> specifies the number of bytes to be read. I/O is performed in	195	C<$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	196	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	197	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	198	(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.	199	file. The current file offset of the file is left unchanged.
		200
		201	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		202	emulated by simply reading the data, which would have a similar effect.
201		203
202	=item aio_stat $fh_or_path, $callback	204	=item aio_stat $fh_or_path, $callback
203		205
204	=item aio_lstat $fh, $callback	206	=item aio_lstat $fh, $callback
205		207
…		…
224	=item aio_unlink $pathname, $callback	226	=item aio_unlink $pathname, $callback
225		227
226	Asynchronously unlink (delete) a file and call the callback with the	228	Asynchronously unlink (delete) a file and call the callback with the
227	result code.	229	result code.
228		230
		231	=item aio_rmdir $pathname, $callback
		232
		233	Asynchronously rmdir (delete) a directory and call the callback with the
		234	result code.
		235
229	=item aio_fsync $fh, $callback	236	=item aio_fsync $fh, $callback
230		237
231	Asynchronously call fsync on the given filehandle and call the callback	238	Asynchronously call fsync on the given filehandle and call the callback
232	with the fsync result code.	239	with the fsync result code.
233		240
234	=item aio_fdatasync $fh, $callback	241	=item aio_fdatasync $fh, $callback
235		242
236	Asynchronously call fdatasync on the given filehandle and call the	243	Asynchronously call fdatasync on the given filehandle and call the
237	callback with the fdatasync result code.	244	callback with the fdatasync result code.
		245
		246	If this call isn't available because your OS lacks it or it couldn't be
		247	detected, it will be emulated by calling C<fsync> instead.
		248
		249	=back
		250
		251	=head2 SUPPORT FUNCTIONS
		252
		253	=over 4
		254
		255	=item $fileno = IO::AIO::poll_fileno
		256
		257	Return the I<request result pipe file descriptor>. This filehandle must be
		258	polled for reading by some mechanism outside this module (e.g. Event or
		259	select, see below or the SYNOPSIS). If the pipe becomes readable you have
		260	to call C<poll_cb> to check the results.
		261
		262	See C<poll_cb> for an example.
		263
		264	=item IO::AIO::poll_cb
		265
		266	Process all outstanding events on the result pipe. You have to call this
		267	regularly. Returns the number of events processed. Returns immediately
		268	when no events are outstanding.
		269
		270	Example: Install an Event watcher that automatically calls
		271	IO::AIO::poll_cb with high priority:
		272
		273	Event->io (fd => IO::AIO::poll_fileno,
		274	poll => 'r', async => 1,
		275	cb => \&IO::AIO::poll_cb);
		276
		277	=item IO::AIO::poll_wait
		278
		279	Wait till the result filehandle becomes ready for reading (simply does a
		280	C<select> on the filehandle. This is useful if you want to synchronously wait
		281	for some requests to finish).
		282
		283	See C<nreqs> for an example.
		284
		285	=item IO::AIO::nreqs
		286
		287	Returns the number of requests currently outstanding (i.e. for which their
		288	callback has not been invoked yet).
		289
		290	Example: wait till there are no outstanding requests anymore:
		291
		292	IO::AIO::poll_wait, IO::AIO::poll_cb
		293	while IO::AIO::nreqs;
		294
		295	=item IO::AIO::flush
		296
		297	Wait till all outstanding AIO requests have been handled.
		298
		299	Strictly equivalent to:
		300
		301	IO::AIO::poll_wait, IO::AIO::poll_cb
		302	while IO::AIO::nreqs;
		303
		304	=item IO::AIO::poll
		305
		306	Waits until some requests have been handled.
		307
		308	Strictly equivalent to:
		309
		310	IO::AIO::poll_wait, IO::AIO::poll_cb
		311	if IO::AIO::nreqs;
		312
		313	=item IO::AIO::min_parallel $nthreads
		314
		315	Set the minimum number of AIO threads to C<$nthreads>. The current default
		316	is C<4>, which means four asynchronous operations can be done at one time
		317	(the number of outstanding operations, however, is unlimited).
		318
		319	IO::AIO starts threads only on demand, when an AIO request is queued and
		320	no free thread exists.
		321
		322	It is recommended to keep the number of threads low, as some Linux
		323	kernel versions will scale negatively with the number of threads (higher
		324	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
		325	threads should be fine.
		326
		327	Under most circumstances you don't need to call this function, as the
		328	module selects a default that is suitable for low to moderate load.
		329
		330	=item IO::AIO::max_parallel $nthreads
		331
		332	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		333	specified number of threads are currently running, this function kills
		334	them. This function blocks until the limit is reached.
		335
		336	While C<$nthreads> are zero, aio requests get queued but not executed
		337	until the number of threads has been increased again.
		338
		339	This module automatically runs C<max_parallel 0> at program end, to ensure
		340	that all threads are killed and that there are no outstanding requests.
		341
		342	Under normal circumstances you don't need to call this function.
		343
		344	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		345
		346	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		347	try to queue up more than this number of requests, the caller will block until
		348	some requests have been handled.
		349
		350	The default is very large, so normally there is no practical limit. If you
		351	queue up many requests in a loop it often improves speed if you set
		352	this to a relatively low number, such as C<100>.
		353
		354	Under normal circumstances you don't need to call this function.
		355
		356	=back
238		357
239	=cut	358	=cut
240		359
241	# support function to convert a fd into a perl filehandle	360	# support function to convert a fd into a perl filehandle
242	sub _fd2fh {	361	sub _fd2fh {
243	return undef if $_[0] < 0;	362	return undef if $_[0] < 0;
244		363
245	# try to be perl5.6-compatible	364	# try to generate nice filehandles
246	local *AIO_FH;	365	my $sym = "IO::AIO::fd#$_[0]";
247	open AIO_FH, "+<&=$_[0]"	366	local *$sym;
		367
		368	open *$sym, "+<&=$_[0]" # usually works under any unix
		369	or open *$sym, "<&=$_[0]" # cygwin needs this
		370	or open *$sym, ">&=$_[0]" # or this
248	or return undef;	371	or return undef;
249		372
250	*AIO_FH	373	*$sym
251	}	374	}
252		375
253	min_parallel 4;	376	min_parallel 4;
254		377
255	END {	378	END {
256	max_parallel 0;	379	max_parallel 0;
257	}	380	}
258		381
259	1;	382	1;
260		383
261	=back	384	=head2 FORK BEHAVIOUR
262		385
263	=head1 BUGS	386	Before the fork, IO::AIO enters a quiescent state where no requests
264		387	can be added in other threads and no results will be processed. After
265	- could be optimized to use more semaphores instead of filehandles.	388	the fork the parent simply leaves the quiescent state and continues
		389	request/result processing, while the child clears the request/result
		390	queue (so the requests started before the fork will only be handled in
		391	the parent). Threats will be started on demand until the limit ste in the
		392	parent process has been reached again.
266		393
267	=head1 SEE ALSO	394	=head1 SEE ALSO
268		395
269	L<Coro>, L<Linux::AIO>.	396	L<Coro>, L<Linux::AIO>.
270		397

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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 1.36 by root, Tue Aug 23 00:03:14 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 1.36 by root, Tue Aug 23 00:03:14 2005 UTC