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

Comparing Linux-AIO/AIO.pm (file contents):
Revision 1.2 by root, Tue Aug 14 18:06:37 2001 UTC vs.
Revision 1.35 by root, Tue Jul 12 10:51:09 2005 UTC

…		…
6		6
7	use Linux::AIO;	7	use Linux::AIO;
8		8
9	=head1 DESCRIPTION	9	=head1 DESCRIPTION
10		10
		11	This module implements asynchronous I/O using the means available to Linux
		12	- clone. It does not hook into the POSIX aio_* functions because Linux
		13	does not yet support these in the kernel (even as of 2.6.12, only O_DIRECT
		14	files are supported) and even if, it would only allow aio_read and write,
		15	not open, stat and so on.
		16
		17	Instead, in this module a number of (non-posix) threads are started that
		18	execute your read/writes and signal their completion. You don't need
		19	thread support in your libc or perl, and the threads created by this
		20	module will not be visible to the pthreads library.
		21
		22	NOTICE: the threads created by this module will automatically be killed
		23	when the thread calling min_parallel exits. Make sure you only ever call
		24	min_parallel from the same thread that loaded this module.
		25
		26	Although the module will work with in the presence of other threads, it is
		27	not reentrant, so use appropriate locking yourself.
		28
		29	=head2 API NOTES
		30
		31	All the C<aio_*> calls are more or less thin wrappers around the syscall
		32	with the same name (sans C<aio_>). The arguments are similar or identical,
		33	and they all accept an additional C<$callback> argument which must be
		34	a code reference. This code reference will get called with the syscall
		35	return code (e.g. most syscalls return C<-1> on error, unlike perl, which
		36	usually delivers "false") as it's sole argument when the given syscall has
		37	been executed asynchronously.
		38
		39	All functions that expect a filehandle will also accept a file descriptor.
		40
		41	The filenames you pass to these routines I<must> be absolute. The reason
		42	is that at the time the request is being executed, the current working
		43	directory could have changed. Alternatively, you can make sure that you
		44	never change the current working directory.
		45
11	=over 4	46	=over 4
12		47
13	=cut	48	=cut
14		49
15	package Linux::AIO;	50	package Linux::AIO;
16		51
17	use base 'Exporter';	52	use base 'Exporter';
18		53
19	BEGIN {	54	BEGIN {
20	$VERSION = 0.001;	55	$VERSION = 1.72;
21		56
22	@EXPORT = qw(aio_read aio_write);	57	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink
		58	aio_fsync aio_fdatasync aio_readahead);
23	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs);	59	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs);
24		60
25	require XSLoader;	61	require XSLoader;
26	XSLoader::load Linux::AIO, $VERSION;	62	XSLoader::load Linux::AIO, $VERSION;
27	}	63	}
28		64
29	=item Linux::AIO::min_parallel($nthreads)	65	=item Linux::AIO::min_parallel $nthreads
30		66
31	Set the minimum number of AIO threads to $nthreads.	67	Set the minimum number of AIO threads to C<$nthreads>. The default is
		68	C<1>, which means a single asynchronous operation can be done at one time
		69	(the number of outstanding operations, however, is unlimited).
32		70
33	=cut	71	It is recommended to keep the number of threads low, as some linux
		72	kernel versions will scale negatively with the number of threads (higher
		73	parallelity => MUCH higher latency).
34		74
		75	Under normal circumstances you don't need to call this function, as this
		76	module automatically starts a single async thread.
		77
		78	=item Linux::AIO::max_parallel $nthreads
		79
		80	Sets the maximum number of AIO threads to C<$nthreads>. If more than
		81	the specified number of threads are currently running, kill them. This
		82	function blocks until the limit is reached.
		83
		84	This module automatically runs C<max_parallel 0> at program end, to ensure
		85	that all threads are killed and that there are no outstanding requests.
		86
		87	Under normal circumstances you don't need to call this function.
		88
		89	=item $fileno = Linux::AIO::poll_fileno
		90
		91	Return the I<request result pipe filehandle>. This filehandle must be
		92	polled for reading by some mechanism outside this module (e.g. Event
		93	or select, see below). If the pipe becomes readable you have to call
		94	C<poll_cb> to check the results.
		95
		96	See C<poll_cb> for an example.
		97
		98	=item Linux::AIO::poll_cb
		99
		100	Process all outstanding events on the result pipe. You have to call this
		101	regularly. Returns the number of events processed. Returns immediately
		102	when no events are outstanding.
		103
		104	You can use Event to multiplex, e.g.:
		105
		106	Event->io (fd => Linux::AIO::poll_fileno,
		107	poll => 'r', async => 1,
		108	cb => \&Linux::AIO::poll_cb);
		109
		110	=item Linux::AIO::poll_wait
		111
		112	Wait till the result filehandle becomes ready for reading (simply does a
		113	select on the filehandle. This is useful if you want to synchronously wait
		114	for some requests to finish).
		115
		116	See C<nreqs> for an example.
		117
		118	=item Linux::AIO::nreqs
		119
		120	Returns the number of requests currently outstanding.
		121
		122	Example: wait till there are no outstanding requests anymore:
		123
		124	Linux::AIO::poll_wait, Linux::AIO::poll_cb
		125	while Linux::AIO::nreqs;
		126
		127	=item aio_open $pathname, $flags, $mode, $callback
		128
		129	Asynchronously open or create a file and call the callback with the
		130	filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this
		131	might change in the future).
		132
		133	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
		134	for an explanation.
		135
		136	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a
		137	list. They are the same as used in C<sysopen>.
		138
		139	Example:
		140
		141	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		142	if ($_[0] >= 0) {
		143	open my $fh, "<&=$_[0]";
		144	print "open successful, fh is $fh\n";
		145	...
		146	} else {
		147	die "open failed: $!\n";
		148	}
		149	};
		150
		151	=item aio_close $fh, $callback
		152
		153	Asynchronously close a file and call the callback with the result code.
		154
35	=item aio_read($fh,$offset,$length, $data,$dataoffset,$callback)	155	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback
		156
36	aio_write($fh,$offset,$length, $data,$dataoffset,$callback)	157	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback
37		158
38	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	159	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
39	into the scalar given by C<data> and offset C<dataoffset> and calls the	160	into the scalar given by C<data> and offset C<dataoffset> and calls the
40	callback without the actual number of bytes read (or undef on error).	161	callback without the actual number of bytes read (or -1 on error, just
		162	like the syscall).
41		163
42	=item $fileno = Linux::AIO::poll_fileno	164	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at
		165	offset C<0> within the scalar:
43		166
44	Return the request result pipe filehandle. This filehandle must be polled	167	aio_read $fh, 7, 15, $buffer, 0, sub {
45	for reading. If the pipe becomes readable you have to call C<poll_cb>.	168	$_[0] >= 0 or die "read error: $!";
		169	print "read <$buffer>\n";
		170	};
46		171
47	=item Linux::AIO::poll_cb	172	=item aio_readahead $fh,$offset,$length, $callback
48		173
49	Process all outstanding events on the result pipe. You have to call this	174	Asynchronously reads the specified byte range into the page cache, using
50	regularly. Returns the number of events processed.	175	the C<readahead> syscall.
51		176
52	=item Linux::AIO::nreqs	177	readahead() populates the page cache with data from a file so that
		178	subsequent reads from that file will not block on disk I/O. The C<$offset>
		179	argument specifies the starting point from which data is to be read and
		180	C<$length> specifies the number of bytes to be read. I/O is performed in
		181	whole pages, so that offset is effectively rounded down to a page boundary
		182	and bytes are read up to the next page boundary greater than or equal to
		183	(off-set+length). aio_readahead() does not read beyond the end of the
		184	file. The current file offset of the file is left unchanged.
53		185
54	Returns the number of requests currently outstanding.	186	=item aio_stat $fh_or_path, $callback
		187
		188	=item aio_lstat $fh, $callback
		189
		190	Works like perl's C<stat> or C<lstat> in void context. The callback will
		191	be called after the stat and the results will be available using C<stat _>
		192	or C<-s _> etc...
		193
		194	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
		195	for an explanation.
		196
		197	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
		198	error when stat'ing a large file, the results will be silently truncated
		199	unless perl itself is compiled with large file support.
		200
		201	Example: Print the length of F</etc/passwd>:
		202
		203	aio_stat "/etc/passwd", sub {
		204	$_[0] and die "stat failed: $!";
		205	print "size is ", -s _, "\n";
		206	};
		207
		208	=item aio_unlink $pathname, $callback
		209
		210	Asynchronously unlink (delete) a file and call the callback with the
		211	result code.
		212
		213	=item aio_fsync $fh, $callback
		214
		215	Asynchronously call fsync on the given filehandle and call the callback
		216	with the fsync result code.
		217
		218	=item aio_fdatasync $fh, $callback
		219
		220	Asynchronously call fdatasync on the given filehandle and call the
		221	callback with the fdatasync result code.
55		222
56	=cut	223	=cut
		224
		225	min_parallel 1;
57		226
58	END {	227	END {
59	max_parallel 0;	228	max_parallel 0;
60	}	229	}
61		230
…		…
63		232
64	=back	233	=back
65		234
66	=head1 BUGS	235	=head1 BUGS
67		236
68	This module has not yet been extensively tested. Watch out!	237	This module has been extensively tested in a large and very busy webserver
		238	for many years now.
69		239
70	This module does not use the aio_* posix functions because a) linux does	240	- aio_open gives a fd, but all other functions expect a perl filehandle.
71	not have aio, b) the existing aio_* functions use pthreads, which are too
72	buggy for my usage.
73		241
74	=head1 SEE ALSO	242	=head1 SEE ALSO
75		243
76	L<Coro>.	244	L<Coro>, L<IO::AIO>.
77		245
78	=head1 AUTHOR	246	=head1 AUTHOR
79		247
80	Marc Lehmann <pcg@goof.com>	248	Marc Lehmann <schmorp@schmorp.de>
81	http://www.goof.com/pcg/marc/	249	http://home.schmorp.de/
82		250
83	=cut	251	=cut
84		252

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Comparing Linux-AIO/AIO.pm (file contents): Revision 1.2 by root, Tue Aug 14 18:06:37 2001 UTC vs. Revision 1.35 by root, Tue Jul 12 10:51:09 2005 UTC

Diff Legend

Comparing Linux-AIO/AIO.pm (file contents):
Revision 1.2 by root, Tue Aug 14 18:06:37 2001 UTC vs.
Revision 1.35 by root, Tue Jul 12 10:51:09 2005 UTC