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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.82 by root, Fri Oct 27 20:10:06 2006 UTC vs.
Revision 1.87 by root, Sun Oct 29 00:52:02 2006 UTC

…		…
50		50
51	=head1 DESCRIPTION	51	=head1 DESCRIPTION
52		52
53	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
54	operating system supports.	54	operating system supports.
		55
		56	Asynchronous means that operations that can normally block your program
		57	(e.g. reading from disk) will be done asynchronously: the operation
		58	will still block, but you can do something else in the meantime. This
		59	is extremely useful for programs that need to stay interactive even
		60	when doing heavy I/O (GUI programs, high performance network servers
		61	etc.), but can also be used to easily do operations in parallel that are
		62	normally done sequentially, e.g. stat'ing many files, which is much faster
		63	on a RAID volume or over NFS when you do a number of stat operations
		64	concurrently.
		65
		66	While this works on all types of file descriptors (for example sockets),
		67	using these functions on file descriptors that support nonblocking
		68	operation (again, sockets, pipes etc.) is very inefficient. Use an event
		69	loop for that (such as the L<Event\|Event> module): IO::AIO will naturally
		70	fit into such an event loop itself.
55		71
56	In this version, a number of threads are started that execute your	72	In this version, a number of threads are started that execute your
57	requests and signal their completion. You don't need thread support	73	requests and signal their completion. You don't need thread support
58	in perl, and the threads created by this module will not be visible	74	in perl, and the threads created by this module will not be visible
59	to perl. In the future, this module might make use of the native aio	75	to perl. In the future, this module might make use of the native aio
60	functions available on many operating systems. However, they are often	76	functions available on many operating systems. However, they are often
61	not well-supported or restricted (Linux doesn't allow them on normal	77	not well-supported or restricted (GNU/Linux doesn't allow them on normal
62	files currently, for example), and they would only support aio_read and	78	files currently, for example), and they would only support aio_read and
63	aio_write, so the remaining functionality would have to be implemented	79	aio_write, so the remaining functionality would have to be implemented
64	using threads anyway.	80	using threads anyway.
65		81
66	Although the module will work with in the presence of other (Perl-)	82	Although the module will work with in the presence of other (Perl-)
67	threads, it is currently not reentrant in any way, so use appropriate	83	threads, it is currently not reentrant in any way, so use appropriate
68	locking yourself, always call C<poll_cb> from within the same thread, or	84	locking yourself, always call C<poll_cb> from within the same thread, or
69	never call C<poll_cb> (or other C<aio_> functions) recursively.	85	never call C<poll_cb> (or other C<aio_> functions) recursively.
70		86
		87	=head2 EXAMPLE
		88
		89	This is a simple example that uses the Event module and loads
		90	F</etc/passwd> asynchronously:
		91
		92	use Fcntl;
		93	use Event;
		94	use IO::AIO;
		95
		96	# register the IO::AIO callback with Event
		97	Event->io (fd => IO::AIO::poll_fileno,
		98	poll => 'r',
		99	cb => \&IO::AIO::poll_cb);
		100
		101	# queue the request to open /etc/passwd
		102	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		103	my $fh = $_[0]
		104	or die "error while opening: $!";
		105
		106	# stat'ing filehandles is generally non-blocking
		107	my $size = -s $fh;
		108
		109	# queue a request to read the file
		110	my $contents;
		111	aio_read $fh, 0, $size, $contents, 0, sub {
		112	$_[0] == $size
		113	or die "short read: $!";
		114
		115	close $fh;
		116
		117	# file contents now in $contents
		118	print $contents;
		119
		120	# exit event loop and program
		121	Event::unloop;
		122	};
		123	};
		124
		125	# possibly queue up other requests, or open GUI windows,
		126	# check for sockets etc. etc.
		127
		128	# process events as long as there are some:
		129	Event::loop;
		130
71	=head1 REQUEST ANATOMY AND LIFETIME	131	=head1 REQUEST ANATOMY AND LIFETIME
72		132
73	Every C<aio_*> function creates a request. which is a C data structure not	133	Every C<aio_*> function creates a request. which is a C data structure not
74	directly visible to Perl.	134	directly visible to Perl.
75		135
…		…
126	use strict 'vars';	186	use strict 'vars';
127		187
128	use base 'Exporter';	188	use base 'Exporter';
129		189
130	BEGIN {	190	BEGIN {
131	our $VERSION = '2.0';	191	our $VERSION = '2.1';
132		192
133	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	193	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
134	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	194	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
135	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	195	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
136	aio_copy aio_group aio_nop aio_mknod);	196	aio_copy aio_group aio_nop aio_mknod);
137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	197	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	198	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
139	min_parallel max_parallel nreqs nready npending);	199	min_parallel max_parallel max_idle
		200	nreqs nready npending nthreads
		201	max_poll_time max_poll_reqs);
140		202
141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	203	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
142		204
143	require XSLoader;	205	require XSLoader;
144	XSLoader::load ("IO::AIO", $VERSION);	206	XSLoader::load ("IO::AIO", $VERSION);
145	}	207	}
146		208
147	=head1 FUNCTIONS	209	=head1 FUNCTIONS
148		210
149	=head2 AIO FUNCTIONS	211	=head2 AIO REQUEST FUNCTIONS
150		212
151	All the C<aio_*> calls are more or less thin wrappers around the syscall	213	All the C<aio_*> calls are more or less thin wrappers around the syscall
152	with the same name (sans C<aio_>). The arguments are similar or identical,	214	with the same name (sans C<aio_>). The arguments are similar or identical,
153	and they all accept an additional (and optional) C<$callback> argument	215	and they all accept an additional (and optional) C<$callback> argument
154	which must be a code reference. This code reference will get called with	216	which must be a code reference. This code reference will get called with
…		…
157	syscall has been executed asynchronously.	219	syscall has been executed asynchronously.
158		220
159	All functions expecting a filehandle keep a copy of the filehandle	221	All functions expecting a filehandle keep a copy of the filehandle
160	internally until the request has finished.	222	internally until the request has finished.
161		223
162	All requests return objects of type L<IO::AIO::REQ> that allow further	224	All functions return request objects of type L<IO::AIO::REQ> that allow
163	manipulation of those requests while they are in-flight.	225	further manipulation of those requests while they are in-flight.
164		226
165	The pathnames you pass to these routines I<must> be absolute and	227	The pathnames you pass to these routines I<must> be absolute and
166	encoded in byte form. The reason for the former is that at the time the	228	encoded as octets. The reason for the former is that at the time the
167	request is being executed, the current working directory could have	229	request is being executed, the current working directory could have
168	changed. Alternatively, you can make sure that you never change the	230	changed. Alternatively, you can make sure that you never change the
169	current working directory.	231	current working directory anywhere in the program and then use relative
		232	paths.
170		233
171	To encode pathnames to byte form, either make sure you either: a)	234	To encode pathnames as octets, either make sure you either: a) always pass
172	always pass in filenames you got from outside (command line, readdir	235	in filenames you got from outside (command line, readdir etc.) without
173	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	236	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
174	your pathnames to the locale (or other) encoding in effect in the user	237	your pathnames to the locale (or other) encoding in effect in the user
175	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	238	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
176	use something else.	239	use something else to ensure your scalar has the correct contents.
		240
		241	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		242	handles correctly wether it is set or not.
177		243
178	=over 4	244	=over 4
179		245
180	=item $prev_pri = aioreq_pri [$pri]	246	=item $prev_pri = aioreq_pri [$pri]
181		247
…		…
204	};	270	};
205		271
206	=item aioreq_nice $pri_adjust	272	=item aioreq_nice $pri_adjust
207		273
208	Similar to C<aioreq_pri>, but subtracts the given value from the current	274	Similar to C<aioreq_pri>, but subtracts the given value from the current
209	priority, so effects are cumulative.	275	priority, so the effect is cumulative.
210		276
211	=item aio_open $pathname, $flags, $mode, $callback->($fh)	277	=item aio_open $pathname, $flags, $mode, $callback->($fh)
212		278
213	Asynchronously open or create a file and call the callback with a newly	279	Asynchronously open or create a file and call the callback with a newly
214	created filehandle for the file.	280	created filehandle for the file.
…		…
331	Asynchronously unlink (delete) a file and call the callback with the	397	Asynchronously unlink (delete) a file and call the callback with the
332	result code.	398	result code.
333		399
334	=item aio_mknod $path, $mode, $dev, $callback->($status)	400	=item aio_mknod $path, $mode, $dev, $callback->($status)
335		401
		402	[EXPERIMENTAL]
		403
336	Asynchronously create a device node (or fifo). See mknod(2): the only	404	Asynchronously create a device node (or fifo). See mknod(2).
337	portable value for C<$mode> is C<S_IFIFO> ored with permissions, and C<0>	405
338	for C<$dev>.	406	The only (POSIX-) portable way of calling this function is:
		407
		408	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
339		409
340	=item aio_link $srcpath, $dstpath, $callback->($status)	410	=item aio_link $srcpath, $dstpath, $callback->($status)
341		411
342	Asynchronously create a new link to the existing object at C<$srcpath> at	412	Asynchronously create a new link to the existing object at C<$srcpath> at
343	the path C<$dstpath> and call the callback with the result code.	413	the path C<$dstpath> and call the callback with the result code.
…		…
827		897
828	=back	898	=back
829		899
830	=head2 SUPPORT FUNCTIONS	900	=head2 SUPPORT FUNCTIONS
831		901
		902	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		903
832	=over 4	904	=over 4
833		905
834	=item $fileno = IO::AIO::poll_fileno	906	=item $fileno = IO::AIO::poll_fileno
835		907
836	Return the I<request result pipe file descriptor>. This filehandle must be	908	Return the I<request result pipe file descriptor>. This filehandle must be
…		…
840		912
841	See C<poll_cb> for an example.	913	See C<poll_cb> for an example.
842		914
843	=item IO::AIO::poll_cb	915	=item IO::AIO::poll_cb
844		916
845	Process all outstanding events on the result pipe. You have to call this	917	Process some outstanding events on the result pipe. You have to call this
846	regularly. Returns the number of events processed. Returns immediately	918	regularly. Returns the number of events processed. Returns immediately
847	when no events are outstanding.	919	when no events are outstanding. The amount of events processed depends on
		920	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
848		921
849	If not all requests were processed for whatever reason, the filehandle	922	If not all requests were processed for whatever reason, the filehandle
850	will still be ready when C<poll_cb> returns.	923	will still be ready when C<poll_cb> returns.
851		924
852	Example: Install an Event watcher that automatically calls	925	Example: Install an Event watcher that automatically calls
…		…
854		927
855	Event->io (fd => IO::AIO::poll_fileno,	928	Event->io (fd => IO::AIO::poll_fileno,
856	poll => 'r', async => 1,	929	poll => 'r', async => 1,
857	cb => \&IO::AIO::poll_cb);	930	cb => \&IO::AIO::poll_cb);
858		931
859	=item IO::AIO::poll_some $max_requests	932	=item IO::AIO::max_poll_reqs $nreqs
860		933
861	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests	934	=item IO::AIO::max_poll_time $seconds
862	at a time.
863		935
864	Useful if you want to ensure some level of interactiveness when perl is	936	These set the maximum number of requests (default C<0>, meaning infinity)
865	not fast enough to process all requests in time.	937	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		938	the maximum amount of time (default C<0>, meaning infinity) spent in
		939	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		940	of time C<poll_cb> is allowed to use).
		941
		942	Setting these is useful if you want to ensure some level of
		943	interactiveness when perl is not fast enough to process all requests in
		944	time.
		945
		946	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
866		947
867	Example: Install an Event watcher that automatically calls	948	Example: Install an Event watcher that automatically calls
868	IO::AIO::poll_some with low priority, to ensure that other parts of the	949	IO::AIO::poll_some with low priority, to ensure that other parts of the
869	program get the CPU sometimes even under high AIO load.	950	program get the CPU sometimes even under high AIO load.
870		951
		952	# try not to spend much more than 0.1s in poll_cb
		953	IO::AIO::max_poll_time 0.1;
		954
		955	# use a low priority so other tasks have priority
871	Event->io (fd => IO::AIO::poll_fileno,	956	Event->io (fd => IO::AIO::poll_fileno,
872	poll => 'r', nice => 1,	957	poll => 'r', nice => 1,
873	cb => sub { IO::AIO::poll_some 256 });	958	cb => &IO::AIO::poll_cb);
874		959
875	=item IO::AIO::poll_wait	960	=item IO::AIO::poll_wait
876		961
877	Wait till the result filehandle becomes ready for reading (simply does a	962	Wait till the result filehandle becomes ready for reading (simply does a
878	C<select> on the filehandle. This is useful if you want to synchronously wait	963	C<select> on the filehandle. This is useful if you want to synchronously
879	for some requests to finish).	964	wait for some requests to finish).
880		965
881	See C<nreqs> for an example.	966	See C<nreqs> for an example.
882		967
		968	=item IO::AIO::poll
		969
		970	Waits until some requests have been handled.
		971
		972	Strictly equivalent to:
		973
		974	IO::AIO::poll_wait, IO::AIO::poll_cb
		975	if IO::AIO::nreqs;
		976
883	=item IO::AIO::nreqs	977	=item IO::AIO::flush
884		978
885	Returns the number of requests currently in the ready, execute or pending	979	Wait till all outstanding AIO requests have been handled.
886	states (i.e. for which their callback has not been invoked yet).
887		980
888	Example: wait till there are no outstanding requests anymore:	981	Strictly equivalent to:
889		982
890	IO::AIO::poll_wait, IO::AIO::poll_cb	983	IO::AIO::poll_wait, IO::AIO::poll_cb
891	while IO::AIO::nreqs;	984	while IO::AIO::nreqs;
892		985
893	=item IO::AIO::nready	986	=head3 CONTROLLING THE NUMBER OF THREADS
894
895	Returns the number of requests currently in the ready state (not yet
896	executed).
897
898	=item IO::AIO::npending
899
900	Returns the number of requests currently in the pending state (executed,
901	but not yet processed by poll_cb).
902
903	=item IO::AIO::flush
904
905	Wait till all outstanding AIO requests have been handled.
906
907	Strictly equivalent to:
908
909	IO::AIO::poll_wait, IO::AIO::poll_cb
910	while IO::AIO::nreqs;
911
912	=item IO::AIO::poll
913
914	Waits until some requests have been handled.
915
916	Strictly equivalent to:
917
918	IO::AIO::poll_wait, IO::AIO::poll_cb
919	if IO::AIO::nreqs;
920		987
921	=item IO::AIO::min_parallel $nthreads	988	=item IO::AIO::min_parallel $nthreads
922		989
923	Set the minimum number of AIO threads to C<$nthreads>. The current	990	Set the minimum number of AIO threads to C<$nthreads>. The current
924	default is C<8>, which means eight asynchronous operations can execute	991	default is C<8>, which means eight asynchronous operations can execute
925	concurrently at any one time (the number of outstanding requests,	992	concurrently at any one time (the number of outstanding requests,
926	however, is unlimited).	993	however, is unlimited).
927		994
928	IO::AIO starts threads only on demand, when an AIO request is queued and	995	IO::AIO starts threads only on demand, when an AIO request is queued and
929	no free thread exists.	996	no free thread exists. Please note that queueing up a hundred requests can
		997	create demand for a hundred threads, even if it turns out that everything
		998	is in the cache and could have been processed faster by a single thread.
930		999
931	It is recommended to keep the number of threads relatively low, as some	1000	It is recommended to keep the number of threads relatively low, as some
932	Linux kernel versions will scale negatively with the number of threads	1001	Linux kernel versions will scale negatively with the number of threads
933	(higher parallelity => MUCH higher latency). With current Linux 2.6	1002	(higher parallelity => MUCH higher latency). With current Linux 2.6
934	versions, 4-32 threads should be fine.	1003	versions, 4-32 threads should be fine.
…		…
948	This module automatically runs C<max_parallel 0> at program end, to ensure	1017	This module automatically runs C<max_parallel 0> at program end, to ensure
949	that all threads are killed and that there are no outstanding requests.	1018	that all threads are killed and that there are no outstanding requests.
950		1019
951	Under normal circumstances you don't need to call this function.	1020	Under normal circumstances you don't need to call this function.
952		1021
		1022	=item IO::AIO::max_idle $nthreads
		1023
		1024	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1025	threads that did not get a request to process within 10 seconds). That
		1026	means if a thread becomes idle while C<$nthreads> other threads are also
		1027	idle, it will free its resources and exit.
		1028
		1029	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1030	to allow for extremely high load situations, but want to free resources
		1031	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1032
		1033	The default is probably ok in most situations, especially if thread
		1034	creation is fast. If thread creation is very slow on your system you might
		1035	want to use larger values.
		1036
953	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1037	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
954		1038
955	This is a very bad function to use in interactive programs because it	1039	This is a very bad function to use in interactive programs because it
956	blocks, and a bad way to reduce concurrency because it is inexact: Better	1040	blocks, and a bad way to reduce concurrency because it is inexact: Better
957	use an C<aio_group> together with a feed callback.	1041	use an C<aio_group> together with a feed callback.
…		…
966		1050
967	You can still queue as many requests as you want. Therefore,	1051	You can still queue as many requests as you want. Therefore,
968	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	1052	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
969	as a stop gap to shield against fatal memory overflow (with large values).	1053	as a stop gap to shield against fatal memory overflow (with large values).
970		1054
		1055	=head3 STATISTICAL INFORMATION
		1056
		1057	=item IO::AIO::nreqs
		1058
		1059	Returns the number of requests currently in the ready, execute or pending
		1060	states (i.e. for which their callback has not been invoked yet).
		1061
		1062	Example: wait till there are no outstanding requests anymore:
		1063
		1064	IO::AIO::poll_wait, IO::AIO::poll_cb
		1065	while IO::AIO::nreqs;
		1066
		1067	=item IO::AIO::nready
		1068
		1069	Returns the number of requests currently in the ready state (not yet
		1070	executed).
		1071
		1072	=item IO::AIO::npending
		1073
		1074	Returns the number of requests currently in the pending state (executed,
		1075	but not yet processed by poll_cb).
		1076
971	=back	1077	=back
972		1078
973	=cut	1079	=cut
974		1080
975	# support function to convert a fd into a perl filehandle	1081	# support function to convert a fd into a perl filehandle
…		…
989	}	1095	}
990		1096
991	min_parallel 8;	1097	min_parallel 8;
992		1098
993	END {	1099	END {
		1100	min_parallel 1;
994	flush;	1101	flush;
995	};	1102	};
996		1103
997	1;	1104	1;
998		1105

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.82 by root, Fri Oct 27 20:10:06 2006 UTC vs. Revision 1.87 by root, Sun Oct 29 00:52:02 2006 UTC

Diff Legend

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.82 by root, Fri Oct 27 20:10:06 2006 UTC vs.
Revision 1.87 by root, Sun Oct 29 00:52:02 2006 UTC