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

Comparing Linux-AIO/AIO.pm (file contents):
Revision 1.1 by root, Tue Aug 14 03:18:53 2001 UTC vs.
Revision 1.32 by root, Sun Jul 10 15:00:38 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 workign 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
		52	use base 'Exporter';
		53
17	BEGIN {	54	BEGIN {
18	$VERSION = 0.001;	55	$VERSION = 1.71;
		56
		57	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink
		58	aio_fsync aio_fdatasync aio_readahead);
		59	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs);
19		60
20	require XSLoader;	61	require XSLoader;
21	XSLoader::load Linux::AIO, $VERSION;	62	XSLoader::load Linux::AIO, $VERSION;
22	}	63	}
23		64
24	use base 'Exporter';
25
26	=item Linux::AIO::min_parallel($nthreads)	65	=item Linux::AIO::min_parallel $nthreads
27		66
28	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).
29		70
30	=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).
31		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, $callback
		128
		129	Asynchronously open or create a file and call the callback with the
		130	filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this
		131	might change in the future).
		132
		133	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a
		134	list. They are the same as used in C<sysopen>.
		135
		136	Example:
		137
		138	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		139	if ($_[0] >= 0) {
		140	open my $fh, "<&$_[0]"; # create a copy for perl
		141	aio_close $_[0], sub { }; # close the aio handle
		142	print "open successful, fh is $fh\n";
		143	...
		144	} else {
		145	die "open failed: $!\n";
		146	}
		147	};
		148
		149	=item aio_close $fh, $callback
		150
		151	Asynchronously close a file and call the callback with the result code.
		152
32	=item Linux::AIO::read($fh,$offset,$length, $data,$dataoffset,$callback)	153	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback
		154
33	Linux::AIO::write($fh,$offset,$length, $data,$dataoffset,$callback)	155	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback
34		156
35	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	157	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
36	into the scalar given by C<data> and offset C<dataoffset> and calls the	158	into the scalar given by C<data> and offset C<dataoffset> and calls the
37	callback without the actual number of bytes read (or undef on error).	159	callback without the actual number of bytes read (or -1 on error, just
		160	like the syscall).
		161
		162	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at
		163	offset C<0> within the scalar:
		164
		165	aio_read $fh, 7, 15, $buffer, 0, sub {
		166	$_[0] >= 0 or die "read error: $!";
		167	print "read <$buffer>\n";
		168	};
		169
		170	=item aio_readahead $fh,$offset,$length, $callback
		171
		172	Asynchronously reads the specified byte range into the page cache, using
		173	the C<readahead> syscall.
		174
		175	readahead() populates the page cache with data from a file so that
		176	subsequent reads from that file will not block on disk I/O. The C<$offset>
		177	argument specifies the starting point from which data is to be read and
		178	C<$length> specifies the number of bytes to be read. I/O is performed in
		179	whole pages, so that offset is effectively rounded down to a page boundary
		180	and bytes are read up to the next page boundary greater than or equal to
		181	(off-set+length). aio_readahead() does not read beyond the end of the
		182	file. The current file offset of the file is left unchanged.
		183
		184	=item aio_stat $fh_or_path, $callback
		185
		186	=item aio_lstat $fh, $callback
		187
		188	Works like perl's C<stat> or C<lstat> in void context. The callback will
		189	be called after the stat and the results will be available using C<stat _>
		190	or C<-s _> etc...
		191
		192	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
		193	for an explanation.
		194
		195	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
		196	error when stat'ing a large file, the results will be silently truncated
		197	unless perl itself is compiled with large file support.
		198
		199	Example: Print the length of F</etc/passwd>:
		200
		201	aio_stat "/etc/passwd", sub {
		202	$_[0] and die "stat failed: $!";
		203	print "size is ", -s _, "\n";
		204	};
		205
		206	=item aio_unlink $pathname, $callback
		207
		208	Asynchronously unlink (delete) a file and call the callback with the
		209	result code.
		210
		211	=item aio_fsync $fh, $callback
		212
		213	Asynchronously call fsync on the given filehandle and call the callback
		214	with the fsync result code.
		215
		216	=item aio_fdatasync $fh, $callback
		217
		218	Asynchronously call fdatasync on the given filehandle and call the
		219	callback with the fdatasync result code.
38		220
39	=cut	221	=cut
40		222
		223	min_parallel 1;
		224
		225	END {
		226	max_parallel 0;
		227	}
		228
41	1;	229	1;
42		230
43	=back	231	=back
44		232
45	=head1 BUGS	233	=head1 BUGS
46		234
47	This module has not yet been extensively tested. Watch out!	235	This module has been extensively tested in a large and very busy webserver
		236	for many years now.
48		237
49	This module does not use the aio_* posix functions because a) linux does	238	- aio_open gives a fd, but all other functions expect a perl filehandle.
50	not have aio, b) the existing aio_* functions use pthreads, which are too
51	buggy for my usage.
52		239
53	=head1 SEE ALSO	240	=head1 SEE ALSO
54		241
55	L<Coro>.	242	L<Coro>.
56		243
57	=head1 AUTHOR	244	=head1 AUTHOR
58		245
59	Marc Lehmann <pcg@goof.com>	246	Marc Lehmann <schmorp@schmorp.de>
60	http://www.goof.com/pcg/marc/	247	http://home.schmorp.de/
61		248
62	=cut	249	=cut
63		250

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Comparing Linux-AIO/AIO.pm (file contents): Revision 1.1 by root, Tue Aug 14 03:18:53 2001 UTC vs. Revision 1.32 by root, Sun Jul 10 15:00:38 2005 UTC

Diff Legend

Comparing Linux-AIO/AIO.pm (file contents):
Revision 1.1 by root, Tue Aug 14 03:18:53 2001 UTC vs.
Revision 1.32 by root, Sun Jul 10 15:00:38 2005 UTC