[ViewVC] Diff of: cvs/IO-AIO/README

Comparing IO-AIO/README (file contents):
Revision 1.3 by root, Sun Jul 10 20:57:36 2005 UTC vs.
Revision 1.10 by root, Wed Aug 17 05:26:20 2005 UTC

…		…
1	NAME	1	NAME
2	IO::AIO - Asynchronous Input/Output	2	IO::AIO - Asynchronous Input/Output
3		3
4	SYNOPSIS	4	SYNOPSIS
5	use IO::AIO;	5	use IO::AIO;
		6
		7	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		8	my ($fh) = @_;
		9	...
		10	};
		11
		12	aio_unlink "/tmp/file", sub { };
		13
		14	aio_read $fh, 30000, 1024, $buffer, 0, sub {
		15	$_[0] > 0 or die "read error: $!";
		16	};
		17
		18	# Event
		19	Event->io (fd => IO::AIO::poll_fileno,
		20	poll => 'r',
		21	cb => \&IO::AIO::poll_cb);
		22
		23	# Glib/Gtk2
		24	add_watch Glib::IO IO::AIO::poll_fileno,
		25	in => sub { IO::AIO::poll_cb; 1 };
		26
		27	# Tk
		28	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		29	readable => \&IO::AIO::poll_cb);
		30
		31	# Danga::Socket
		32	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		33	\&IO::AIO::poll_cb);
6		34
7	DESCRIPTION	35	DESCRIPTION
8	This module implements asynchronous I/O using whatever means your	36	This module implements asynchronous I/O using whatever means your
9	operating system supports.	37	operating system supports.
10		38
17	currently, for example), and they would only support aio_read and	45	currently, for example), and they would only support aio_read and
18	aio_write, so the remaining functionality would have to be implemented	46	aio_write, so the remaining functionality would have to be implemented
19	using threads anyway.	47	using threads anyway.
20		48
21	Although the module will work with in the presence of other threads, it	49	Although the module will work with in the presence of other threads, it
22	is currently not reentrant, so use appropriate locking yourself.	50	is currently not reentrant, so use appropriate locking yourself, always
		51	call "poll_cb" from within the same thread, or never call "poll_cb" (or
		52	other "aio_" functions) recursively.
23		53
24	API NOTES	54	FUNCTIONS
		55	AIO FUNCTIONS
25	All the "aio_*" calls are more or less thin wrappers around the syscall	56	All the "aio_*" calls are more or less thin wrappers around the syscall
26	with the same name (sans "aio_"). The arguments are similar or	57	with the same name (sans "aio_"). The arguments are similar or
27	identical, and they all accept an additional $callback argument which	58	identical, and they all accept an additional (and optional) $callback
28	must be a code reference. This code reference will get called with the	59	argument which must be a code reference. This code reference will get
29	syscall return code (e.g. most syscalls return -1 on error, unlike perl,	60	called with the syscall return code (e.g. most syscalls return -1 on
30	which usually delivers "false") as it's sole argument when the given	61	error, unlike perl, which usually delivers "false") as it's sole
31	syscall has been executed asynchronously.	62	argument when the given syscall has been executed asynchronously.
32		63
33	All functions that expect a filehandle will also accept a file	64	All functions expecting a filehandle keep a copy of the filehandle
34	descriptor.	65	internally until the request has finished.
35		66
36	The filenames you pass to these routines must be absolute. The reason	67	The pathnames you pass to these routines must be absolute and encoded
37	is that at the time the request is being executed, the current working	68	in byte form. The reason for the former is that at the time the request
38	directory could have changed. Alternatively, you can make sure that you	69	is being executed, the current working directory could have changed.
39	never change the current working directory.	70	Alternatively, you can make sure that you never change the current
		71	working directory.
40		72
41	IO::AIO::min_parallel $nthreads	73	To encode pathnames to byte form, either make sure you either: a) always
42	Set the minimum number of AIO threads to $nthreads. The default is	74	pass in filenames you got from outside (command line, readdir etc.), b)
43	1, which means a single asynchronous operation can be done at one	75	are ASCII or ISO 8859-1, c) use the Encode module and encode your
44	time (the number of outstanding operations, however, is unlimited).	76	pathnames to the locale (or other) encoding in effect in the user
45		77	environment, d) use Glib::filename_from_unicode on unicode filenames or
46	It is recommended to keep the number of threads low, as some Linux	78	e) use something else.
47	kernel versions will scale negatively with the number of threads
48	(higher parallelity => MUCH higher latency). With current Linux 2.6
49	versions, 4-32 threads should be fine.
50
51	Under normal circumstances you don't need to call this function, as
52	this module automatically starts some threads (the exact number
53	might change, and is currently 4).
54
55	IO::AIO::max_parallel $nthreads
56	Sets the maximum number of AIO threads to $nthreads. If more than
57	the specified number of threads are currently running, kill them.
58	This function blocks until the limit is reached.
59
60	This module automatically runs "max_parallel 0" at program end, to
61	ensure that all threads are killed and that there are no outstanding
62	requests.
63
64	Under normal circumstances you don't need to call this function.
65
66	$oldnreqs = IO::AIO::max_outstanding $nreqs
67	Sets the maximum number of outstanding requests to $nreqs. If you
68	try to queue up more than this number of requests, the caller will
69	block until some requests have been handled.
70
71	The default is very large, so normally there is no practical limit.
72	If you queue up many requests in a loop it it often improves speed
73	if you set this to a relatively low number, such as 100.
74
75	Under normal circumstances you don't need to call this function.
76
77	$fileno = IO::AIO::poll_fileno
78	Return the request result pipe filehandle. This filehandle must be
79	polled for reading by some mechanism outside this module (e.g. Event
80	or select, see below). If the pipe becomes readable you have to call
81	"poll_cb" to check the results.
82
83	See "poll_cb" for an example.
84
85	IO::AIO::poll_cb
86	Process all outstanding events on the result pipe. You have to call
87	this regularly. Returns the number of events processed. Returns
88	immediately when no events are outstanding.
89
90	You can use Event to multiplex, e.g.:
91
92	Event->io (fd => IO::AIO::poll_fileno,
93	poll => 'r', async => 1,
94	cb => \&IO::AIO::poll_cb);
95
96	IO::AIO::poll_wait
97	Wait till the result filehandle becomes ready for reading (simply
98	does a select on the filehandle. This is useful if you want to
99	synchronously wait for some requests to finish).
100
101	See "nreqs" for an example.
102
103	IO::AIO::nreqs
104	Returns the number of requests currently outstanding.
105
106	Example: wait till there are no outstanding requests anymore:
107
108	IO::AIO::poll_wait, IO::AIO::poll_cb
109	while IO::AIO::nreqs;
110		79
111	aio_open $pathname, $flags, $mode, $callback	80	aio_open $pathname, $flags, $mode, $callback
112	Asynchronously open or create a file and call the callback with a	81	Asynchronously open or create a file and call the callback with a
113	newly created filehandle for the file.	82	newly created filehandle for the file.
114		83
115	The pathname passed to "aio_open" must be absolute. See API NOTES,	84	The pathname passed to "aio_open" must be absolute. See API NOTES,
116	above, for an explanation.	85	above, for an explanation.
117		86
118	The $mode argument is a bitmask. See the "Fcntl" module for a list.	87	The $flags argument is a bitmask. See the "Fcntl" module for a list.
119	They are the same as used in "sysopen".	88	They are the same as used by "sysopen".
		89
		90	Likewise, $mode specifies the mode of the newly created file, if it
		91	didn't exist and "O_CREAT" has been given, just like perl's
		92	"sysopen", except that it is mandatory (i.e. use 0 if you don't
		93	create new files, and 0666 or 0777 if you do).
120		94
121	Example:	95	Example:
122		96
123	aio_open "/etc/passwd", O_RDONLY, 0, sub {	97	aio_open "/etc/passwd", O_RDONLY, 0, sub {
124	if ($_[0]) {	98	if ($_[0]) {
…		…
131		105
132	aio_close $fh, $callback	106	aio_close $fh, $callback
133	Asynchronously close a file and call the callback with the result	107	Asynchronously close a file and call the callback with the result
134	code. WARNING: although accepted, you should not pass in a perl	108	code. WARNING: although accepted, you should not pass in a perl
135	filehandle here, as perl will likely close the file descriptor	109	filehandle here, as perl will likely close the file descriptor
136	itself when the filehandle is destroyed. Normally, you can safely	110	another time when the filehandle is destroyed. Normally, you can
137	call perls "close" or just let filehandles go out of scope.	111	safely call perls "close" or just let filehandles go out of scope.
		112
		113	This is supposed to be a bug in the API, so that might change. It's
		114	therefore best to avoid this function.
138		115
139	aio_read $fh,$offset,$length, $data,$dataoffset,$callback	116	aio_read $fh,$offset,$length, $data,$dataoffset,$callback
140	aio_write $fh,$offset,$length, $data,$dataoffset,$callback	117	aio_write $fh,$offset,$length, $data,$dataoffset,$callback
141	Reads or writes "length" bytes from the specified "fh" and "offset"	118	Reads or writes "length" bytes from the specified "fh" and "offset"
142	into the scalar given by "data" and offset "dataoffset" and calls	119	into the scalar given by "data" and offset "dataoffset" and calls
143	the callback without the actual number of bytes read (or -1 on	120	the callback without the actual number of bytes read (or -1 on
144	error, just like the syscall).	121	error, just like the syscall).
145		122
		123	The $data scalar MUST NOT be modified in any way while the request
		124	is outstanding. Modifying it can result in segfaults or WW3 (if the
		125	necessary/optional hardware is installed).
		126
146	Example: Read 15 bytes at offset 7 into scalar $buffer, strating at	127	Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
147	offset 0 within the scalar:	128	offset 0 within the scalar:
148		129
149	aio_read $fh, 7, 15, $buffer, 0, sub {	130	aio_read $fh, 7, 15, $buffer, 0, sub {
150	$_[0] >= 0 or die "read error: $!";	131	$_[0] > 0 or die "read error: $!";
151	print "read <$buffer>\n";	132	print "read $_[0] bytes: <$buffer>\n";
152	};	133	};
153		134
154	aio_readahead $fh,$offset,$length, $callback	135	aio_readahead $fh,$offset,$length, $callback
155	Asynchronously reads the specified byte range into the page cache,
156	using the "readahead" syscall. If that syscall doesn't exist the
157	status will be -1 and $! is set to ENOSYS.
158
159	readahead() populates the page cache with data from a file so that	136	"aio_readahead" populates the page cache with data from a file so
160	subsequent reads from that file will not block on disk I/O. The	137	that subsequent reads from that file will not block on disk I/O. The
161	$offset argument specifies the starting point from which data is to	138	$offset argument specifies the starting point from which data is to
162	be read and $length specifies the number of bytes to be read. I/O is	139	be read and $length specifies the number of bytes to be read. I/O is
163	performed in whole pages, so that offset is effectively rounded down	140	performed in whole pages, so that offset is effectively rounded down
164	to a page boundary and bytes are read up to the next page boundary	141	to a page boundary and bytes are read up to the next page boundary
165	greater than or equal to (off-set+length). aio_readahead() does not	142	greater than or equal to (off-set+length). "aio_readahead" does not
166	read beyond the end of the file. The current file offset of the file	143	read beyond the end of the file. The current file offset of the file
167	is left unchanged.	144	is left unchanged.
		145
		146	If that syscall doesn't exist (likely if your OS isn't Linux) it
		147	will be emulated by simply reading the data, which would have a
		148	similar effect.
168		149
169	aio_stat $fh_or_path, $callback	150	aio_stat $fh_or_path, $callback
170	aio_lstat $fh, $callback	151	aio_lstat $fh, $callback
171	Works like perl's "stat" or "lstat" in void context. The callback	152	Works like perl's "stat" or "lstat" in void context. The callback
172	will be called after the stat and the results will be available	153	will be called after the stat and the results will be available
…		…
189		170
190	aio_unlink $pathname, $callback	171	aio_unlink $pathname, $callback
191	Asynchronously unlink (delete) a file and call the callback with the	172	Asynchronously unlink (delete) a file and call the callback with the
192	result code.	173	result code.
193		174
		175	aio_rmdir $pathname, $callback
		176	Asynchronously rmdir (delete) a directory and call the callback with
		177	the result code.
		178
194	aio_fsync $fh, $callback	179	aio_fsync $fh, $callback
195	Asynchronously call fsync on the given filehandle and call the	180	Asynchronously call fsync on the given filehandle and call the
196	callback with the fsync result code.	181	callback with the fsync result code.
197		182
198	aio_fdatasync $fh, $callback	183	aio_fdatasync $fh, $callback
199	Asynchronously call fdatasync on the given filehandle and call the	184	Asynchronously call fdatasync on the given filehandle and call the
200	callback with the fdatasync result code.	185	callback with the fdatasync result code.
201		186
202	BUGS	187	If this call isn't available because your OS lacks it or it couldn't
203	- could be optimized to use more semaphores instead of filehandles.	188	be detected, it will be emulated by calling "fsync" instead.
		189
		190	SUPPORT FUNCTIONS
		191	$fileno = IO::AIO::poll_fileno
		192	Return the request result pipe file descriptor. This filehandle
		193	must be polled for reading by some mechanism outside this module
		194	(e.g. Event or select, see below or the SYNOPSIS). If the pipe
		195	becomes readable you have to call "poll_cb" to check the results.
		196
		197	See "poll_cb" for an example.
		198
		199	IO::AIO::poll_cb
		200	Process all outstanding events on the result pipe. You have to call
		201	this regularly. Returns the number of events processed. Returns
		202	immediately when no events are outstanding.
		203
		204	Example: Install an Event watcher that automatically calls
		205	IO::AIO::poll_cb with high priority:
		206
		207	Event->io (fd => IO::AIO::poll_fileno,
		208	poll => 'r', async => 1,
		209	cb => \&IO::AIO::poll_cb);
		210
		211	IO::AIO::poll_wait
		212	Wait till the result filehandle becomes ready for reading (simply
		213	does a "select" on the filehandle. This is useful if you want to
		214	synchronously wait for some requests to finish).
		215
		216	See "nreqs" for an example.
		217
		218	IO::AIO::nreqs
		219	Returns the number of requests currently outstanding (i.e. for which
		220	their callback has not been invoked yet).
		221
		222	Example: wait till there are no outstanding requests anymore:
		223
		224	IO::AIO::poll_wait, IO::AIO::poll_cb
		225	while IO::AIO::nreqs;
		226
		227	IO::AIO::flush
		228	Wait till all outstanding AIO requests have been handled.
		229
		230	Strictly equivalent to:
		231
		232	IO::AIO::poll_wait, IO::AIO::poll_cb
		233	while IO::AIO::nreqs;
		234
		235	IO::AIO::poll
		236	Waits until some requests have been handled.
		237
		238	Strictly equivalent to:
		239
		240	IO::AIO::poll_wait, IO::AIO::poll_cb
		241	if IO::AIO::nreqs;
		242
		243	IO::AIO::min_parallel $nthreads
		244	Set the minimum number of AIO threads to $nthreads. The default is
		245	1, which means a single asynchronous operation can be done at one
		246	time (the number of outstanding operations, however, is unlimited).
		247
		248	It is recommended to keep the number of threads low, as some Linux
		249	kernel versions will scale negatively with the number of threads
		250	(higher parallelity => MUCH higher latency). With current Linux 2.6
		251	versions, 4-32 threads should be fine.
		252
		253	Under normal circumstances you don't need to call this function, as
		254	this module automatically starts some threads (the exact number
		255	might change, and is currently 4).
		256
		257	IO::AIO::max_parallel $nthreads
		258	Sets the maximum number of AIO threads to $nthreads. If more than
		259	the specified number of threads are currently running, kill them.
		260	This function blocks until the limit is reached.
		261
		262	This module automatically runs "max_parallel 0" at program end, to
		263	ensure that all threads are killed and that there are no outstanding
		264	requests.
		265
		266	Under normal circumstances you don't need to call this function.
		267
		268	$oldnreqs = IO::AIO::max_outstanding $nreqs
		269	Sets the maximum number of outstanding requests to $nreqs. If you
		270	try to queue up more than this number of requests, the caller will
		271	block until some requests have been handled.
		272
		273	The default is very large, so normally there is no practical limit.
		274	If you queue up many requests in a loop it it often improves speed
		275	if you set this to a relatively low number, such as 100.
		276
		277	Under normal circumstances you don't need to call this function.
		278
		279	FORK BEHAVIOUR
		280	Before the fork IO::AIO enters a quiescent state where no requests can
		281	be added in other threads and no results will be processed. After the
		282	fork the parent simply leaves the quiescent state and continues
		283	request/result processing, while the child clears the request/result
		284	queue and starts the same number of threads as were in use by the
		285	parent.
204		286
205	SEE ALSO	287	SEE ALSO
206	Coro, Linux::AIO.	288	Coro, Linux::AIO.
207		289
208	AUTHOR	290	AUTHOR

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Comparing IO-AIO/README (file contents): Revision 1.3 by root, Sun Jul 10 20:57:36 2005 UTC vs. Revision 1.10 by root, Wed Aug 17 05:26:20 2005 UTC

Diff Legend

Comparing IO-AIO/README (file contents):
Revision 1.3 by root, Sun Jul 10 20:57:36 2005 UTC vs.
Revision 1.10 by root, Wed Aug 17 05:26:20 2005 UTC