[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 1.90 by root, Mon Oct 30 23:30:00 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 most of this works on all types of file descriptors (for example
		67	sockets), using these functions on file descriptors that support
		68	nonblocking operation (again, sockets, pipes etc.) is very inefficient or
		69	might not work (aio_read fails on sockets/pipes/fifos). Use an event loop
		70	for that (such as the L<Event\|Event> module): IO::AIO will naturally fit
		71	into such an event loop itself.
55		72
56	In this version, a number of threads are started that execute your	73	In this version, a number of threads are started that execute your
57	requests and signal their completion. You don't need thread support	74	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	75	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	76	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	77	functions available on many operating systems. However, they are often
61	not well-supported or restricted (Linux doesn't allow them on normal	78	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	79	files currently, for example), and they would only support aio_read and
63	aio_write, so the remaining functionality would have to be implemented	80	aio_write, so the remaining functionality would have to be implemented
64	using threads anyway.	81	using threads anyway.
65		82
66	Although the module will work with in the presence of other (Perl-)	83	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	84	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	85	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.	86	never call C<poll_cb> (or other C<aio_> functions) recursively.
70		87
		88	=head2 EXAMPLE
		89
		90	This is a simple example that uses the Event module and loads
		91	F</etc/passwd> asynchronously:
		92
		93	use Fcntl;
		94	use Event;
		95	use IO::AIO;
		96
		97	# register the IO::AIO callback with Event
		98	Event->io (fd => IO::AIO::poll_fileno,
		99	poll => 'r',
		100	cb => \&IO::AIO::poll_cb);
		101
		102	# queue the request to open /etc/passwd
		103	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		104	my $fh = $_[0]
		105	or die "error while opening: $!";
		106
		107	# stat'ing filehandles is generally non-blocking
		108	my $size = -s $fh;
		109
		110	# queue a request to read the file
		111	my $contents;
		112	aio_read $fh, 0, $size, $contents, 0, sub {
		113	$_[0] == $size
		114	or die "short read: $!";
		115
		116	close $fh;
		117
		118	# file contents now in $contents
		119	print $contents;
		120
		121	# exit event loop and program
		122	Event::unloop;
		123	};
		124	};
		125
		126	# possibly queue up other requests, or open GUI windows,
		127	# check for sockets etc. etc.
		128
		129	# process events as long as there are some:
		130	Event::loop;
		131
71	=head1 REQUEST ANATOMY AND LIFETIME	132	=head1 REQUEST ANATOMY AND LIFETIME
72		133
73	Every C<aio_*> function creates a request. which is a C data structure not	134	Every C<aio_*> function creates a request. which is a C data structure not
74	directly visible to Perl.	135	directly visible to Perl.
75		136
…		…
116	Request has reached the end of its lifetime and holds no resources anymore	177	Request has reached the end of its lifetime and holds no resources anymore
117	(except possibly for the Perl object, but its connection to the actual	178	(except possibly for the Perl object, but its connection to the actual
118	aio request is severed and calling its methods will either do nothing or	179	aio request is severed and calling its methods will either do nothing or
119	result in a runtime error).	180	result in a runtime error).
120		181
		182	=back
		183
121	=cut	184	=cut
122		185
123	package IO::AIO;	186	package IO::AIO;
124		187
125	no warnings;	188	no warnings;
126	use strict 'vars';	189	use strict 'vars';
127		190
128	use base 'Exporter';	191	use base 'Exporter';
129		192
130	BEGIN {	193	BEGIN {
131	our $VERSION = '2.0';	194	our $VERSION = '2.1';
132		195
133	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	196	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	197	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	198	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
136	aio_copy aio_group aio_nop aio_mknod);	199	aio_move aio_copy aio_group aio_nop aio_mknod);
137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	200	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	201	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
139	min_parallel max_parallel nreqs nready npending);	202	min_parallel max_parallel max_idle
		203	nreqs nready npending nthreads
		204	max_poll_time max_poll_reqs);
140		205
141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	206	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
142		207
143	require XSLoader;	208	require XSLoader;
144	XSLoader::load ("IO::AIO", $VERSION);	209	XSLoader::load ("IO::AIO", $VERSION);
145	}	210	}
146		211
147	=head1 FUNCTIONS	212	=head1 FUNCTIONS
148		213
149	=head2 AIO FUNCTIONS	214	=head2 AIO REQUEST FUNCTIONS
150		215
151	All the C<aio_*> calls are more or less thin wrappers around the syscall	216	All the C<aio_*> calls are more or less thin wrappers around the syscall
152	with the same name (sans C<aio_>). The arguments are similar or identical,	217	with the same name (sans C<aio_>). The arguments are similar or identical,
153	and they all accept an additional (and optional) C<$callback> argument	218	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	219	which must be a code reference. This code reference will get called with
…		…
157	syscall has been executed asynchronously.	222	syscall has been executed asynchronously.
158		223
159	All functions expecting a filehandle keep a copy of the filehandle	224	All functions expecting a filehandle keep a copy of the filehandle
160	internally until the request has finished.	225	internally until the request has finished.
161		226
162	All requests return objects of type L<IO::AIO::REQ> that allow further	227	All functions return request objects of type L<IO::AIO::REQ> that allow
163	manipulation of those requests while they are in-flight.	228	further manipulation of those requests while they are in-flight.
164		229
165	The pathnames you pass to these routines I<must> be absolute and	230	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	231	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	232	request is being executed, the current working directory could have
168	changed. Alternatively, you can make sure that you never change the	233	changed. Alternatively, you can make sure that you never change the
169	current working directory.	234	current working directory anywhere in the program and then use relative
		235	paths.
170		236
171	To encode pathnames to byte form, either make sure you either: a)	237	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	238	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	239	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	240	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)	241	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
176	use something else.	242	use something else to ensure your scalar has the correct contents.
		243
		244	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		245	handles correctly wether it is set or not.
177		246
178	=over 4	247	=over 4
179		248
180	=item $prev_pri = aioreq_pri [$pri]	249	=item $prev_pri = aioreq_pri [$pri]
181		250
…		…
204	};	273	};
205		274
206	=item aioreq_nice $pri_adjust	275	=item aioreq_nice $pri_adjust
207		276
208	Similar to C<aioreq_pri>, but subtracts the given value from the current	277	Similar to C<aioreq_pri>, but subtracts the given value from the current
209	priority, so effects are cumulative.	278	priority, so the effect is cumulative.
210		279
211	=item aio_open $pathname, $flags, $mode, $callback->($fh)	280	=item aio_open $pathname, $flags, $mode, $callback->($fh)
212		281
213	Asynchronously open or create a file and call the callback with a newly	282	Asynchronously open or create a file and call the callback with a newly
214	created filehandle for the file.	283	created filehandle for the file.
…		…
331	Asynchronously unlink (delete) a file and call the callback with the	400	Asynchronously unlink (delete) a file and call the callback with the
332	result code.	401	result code.
333		402
334	=item aio_mknod $path, $mode, $dev, $callback->($status)	403	=item aio_mknod $path, $mode, $dev, $callback->($status)
335		404
		405	[EXPERIMENTAL]
		406
336	Asynchronously create a device node (or fifo). See mknod(2): the only	407	Asynchronously create a device node (or fifo). See mknod(2).
337	portable value for C<$mode> is C<S_IFIFO> ored with permissions, and C<0>	408
338	for C<$dev>.	409	The only (POSIX-) portable way of calling this function is:
		410
		411	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
339		412
340	=item aio_link $srcpath, $dstpath, $callback->($status)	413	=item aio_link $srcpath, $dstpath, $callback->($status)
341		414
342	Asynchronously create a new link to the existing object at C<$srcpath> at	415	Asynchronously create a new link to the existing object at C<$srcpath> at
343	the path C<$dstpath> and call the callback with the result code.	416	the path C<$dstpath> and call the callback with the result code.
344		417
345	=item aio_symlink $srcpath, $dstpath, $callback->($status)	418	=item aio_symlink $srcpath, $dstpath, $callback->($status)
346		419
347	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	420	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
348	the path C<$dstpath> and call the callback with the result code.	421	the path C<$dstpath> and call the callback with the result code.
		422
		423	=item aio_readlink $path, $callback->($link)
		424
		425	Asynchronously read the symlink specified by C<$path> and pass it to
		426	the callback. If an error occurs, nothing or undef gets passed to the
		427	callback.
349		428
350	=item aio_rename $srcpath, $dstpath, $callback->($status)	429	=item aio_rename $srcpath, $dstpath, $callback->($status)
351		430
352	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	431	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
353	rename(2) and call the callback with the result code.	432	rename(2) and call the callback with the result code.
…		…
827		906
828	=back	907	=back
829		908
830	=head2 SUPPORT FUNCTIONS	909	=head2 SUPPORT FUNCTIONS
831		910
		911	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		912
832	=over 4	913	=over 4
833		914
834	=item $fileno = IO::AIO::poll_fileno	915	=item $fileno = IO::AIO::poll_fileno
835		916
836	Return the I<request result pipe file descriptor>. This filehandle must be	917	Return the I<request result pipe file descriptor>. This filehandle must be
…		…
840		921
841	See C<poll_cb> for an example.	922	See C<poll_cb> for an example.
842		923
843	=item IO::AIO::poll_cb	924	=item IO::AIO::poll_cb
844		925
845	Process all outstanding events on the result pipe. You have to call this	926	Process some outstanding events on the result pipe. You have to call this
846	regularly. Returns the number of events processed. Returns immediately	927	regularly. Returns the number of events processed. Returns immediately
847	when no events are outstanding.	928	when no events are outstanding. The amount of events processed depends on
		929	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
848		930
849	If not all requests were processed for whatever reason, the filehandle	931	If not all requests were processed for whatever reason, the filehandle
850	will still be ready when C<poll_cb> returns.	932	will still be ready when C<poll_cb> returns.
851		933
852	Example: Install an Event watcher that automatically calls	934	Example: Install an Event watcher that automatically calls
…		…
854		936
855	Event->io (fd => IO::AIO::poll_fileno,	937	Event->io (fd => IO::AIO::poll_fileno,
856	poll => 'r', async => 1,	938	poll => 'r', async => 1,
857	cb => \&IO::AIO::poll_cb);	939	cb => \&IO::AIO::poll_cb);
858		940
859	=item IO::AIO::poll_some $max_requests	941	=item IO::AIO::max_poll_reqs $nreqs
860		942
861	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests	943	=item IO::AIO::max_poll_time $seconds
862	at a time.
863		944
864	Useful if you want to ensure some level of interactiveness when perl is	945	These set the maximum number of requests (default C<0>, meaning infinity)
865	not fast enough to process all requests in time.	946	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		947	the maximum amount of time (default C<0>, meaning infinity) spent in
		948	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		949	of time C<poll_cb> is allowed to use).
		950
		951	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		952	syscall per request processed, which is not normally a problem unless your
		953	callbacks are really really fast or your OS is really really slow (I am
		954	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		955
		956	Setting these is useful if you want to ensure some level of
		957	interactiveness when perl is not fast enough to process all requests in
		958	time.
		959
		960	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
866		961
867	Example: Install an Event watcher that automatically calls	962	Example: Install an Event watcher that automatically calls
868	IO::AIO::poll_some with low priority, to ensure that other parts of the	963	IO::AIO::poll_cb with low priority, to ensure that other parts of the
869	program get the CPU sometimes even under high AIO load.	964	program get the CPU sometimes even under high AIO load.
870		965
		966	# try not to spend much more than 0.1s in poll_cb
		967	IO::AIO::max_poll_time 0.1;
		968
		969	# use a low priority so other tasks have priority
871	Event->io (fd => IO::AIO::poll_fileno,	970	Event->io (fd => IO::AIO::poll_fileno,
872	poll => 'r', nice => 1,	971	poll => 'r', nice => 1,
873	cb => sub { IO::AIO::poll_some 256 });	972	cb => &IO::AIO::poll_cb);
874		973
875	=item IO::AIO::poll_wait	974	=item IO::AIO::poll_wait
876		975
877	Wait till the result filehandle becomes ready for reading (simply does a	976	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	977	C<select> on the filehandle. This is useful if you want to synchronously
879	for some requests to finish).	978	wait for some requests to finish).
880		979
881	See C<nreqs> for an example.	980	See C<nreqs> for an example.
882		981
		982	=item IO::AIO::poll
		983
		984	Waits until some requests have been handled.
		985
		986	Strictly equivalent to:
		987
		988	IO::AIO::poll_wait, IO::AIO::poll_cb
		989	if IO::AIO::nreqs;
		990
883	=item IO::AIO::nreqs	991	=item IO::AIO::flush
884		992
885	Returns the number of requests currently in the ready, execute or pending	993	Wait till all outstanding AIO requests have been handled.
886	states (i.e. for which their callback has not been invoked yet).
887		994
888	Example: wait till there are no outstanding requests anymore:	995	Strictly equivalent to:
889		996
890	IO::AIO::poll_wait, IO::AIO::poll_cb	997	IO::AIO::poll_wait, IO::AIO::poll_cb
891	while IO::AIO::nreqs;	998	while IO::AIO::nreqs;
892		999
893	=item IO::AIO::nready	1000	=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		1001
921	=item IO::AIO::min_parallel $nthreads	1002	=item IO::AIO::min_parallel $nthreads
922		1003
923	Set the minimum number of AIO threads to C<$nthreads>. The current	1004	Set the minimum number of AIO threads to C<$nthreads>. The current
924	default is C<8>, which means eight asynchronous operations can execute	1005	default is C<8>, which means eight asynchronous operations can execute
925	concurrently at any one time (the number of outstanding requests,	1006	concurrently at any one time (the number of outstanding requests,
926	however, is unlimited).	1007	however, is unlimited).
927		1008
928	IO::AIO starts threads only on demand, when an AIO request is queued and	1009	IO::AIO starts threads only on demand, when an AIO request is queued and
929	no free thread exists.	1010	no free thread exists. Please note that queueing up a hundred requests can
		1011	create demand for a hundred threads, even if it turns out that everything
		1012	is in the cache and could have been processed faster by a single thread.
930		1013
931	It is recommended to keep the number of threads relatively low, as some	1014	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	1015	Linux kernel versions will scale negatively with the number of threads
933	(higher parallelity => MUCH higher latency). With current Linux 2.6	1016	(higher parallelity => MUCH higher latency). With current Linux 2.6
934	versions, 4-32 threads should be fine.	1017	versions, 4-32 threads should be fine.
…		…
948	This module automatically runs C<max_parallel 0> at program end, to ensure	1031	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.	1032	that all threads are killed and that there are no outstanding requests.
950		1033
951	Under normal circumstances you don't need to call this function.	1034	Under normal circumstances you don't need to call this function.
952		1035
		1036	=item IO::AIO::max_idle $nthreads
		1037
		1038	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1039	threads that did not get a request to process within 10 seconds). That
		1040	means if a thread becomes idle while C<$nthreads> other threads are also
		1041	idle, it will free its resources and exit.
		1042
		1043	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1044	to allow for extremely high load situations, but want to free resources
		1045	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1046
		1047	The default is probably ok in most situations, especially if thread
		1048	creation is fast. If thread creation is very slow on your system you might
		1049	want to use larger values.
		1050
953	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1051	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
954		1052
955	This is a very bad function to use in interactive programs because it	1053	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	1054	blocks, and a bad way to reduce concurrency because it is inexact: Better
957	use an C<aio_group> together with a feed callback.	1055	use an C<aio_group> together with a feed callback.
…		…
966		1064
967	You can still queue as many requests as you want. Therefore,	1065	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	1066	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).	1067	as a stop gap to shield against fatal memory overflow (with large values).
970		1068
		1069	=head3 STATISTICAL INFORMATION
		1070
		1071	=item IO::AIO::nreqs
		1072
		1073	Returns the number of requests currently in the ready, execute or pending
		1074	states (i.e. for which their callback has not been invoked yet).
		1075
		1076	Example: wait till there are no outstanding requests anymore:
		1077
		1078	IO::AIO::poll_wait, IO::AIO::poll_cb
		1079	while IO::AIO::nreqs;
		1080
		1081	=item IO::AIO::nready
		1082
		1083	Returns the number of requests currently in the ready state (not yet
		1084	executed).
		1085
		1086	=item IO::AIO::npending
		1087
		1088	Returns the number of requests currently in the pending state (executed,
		1089	but not yet processed by poll_cb).
		1090
971	=back	1091	=back
972		1092
973	=cut	1093	=cut
974		1094
975	# support function to convert a fd into a perl filehandle	1095	# support function to convert a fd into a perl filehandle
…		…
989	}	1109	}
990		1110
991	min_parallel 8;	1111	min_parallel 8;
992		1112
993	END {	1113	END {
		1114	min_parallel 1;
994	flush;	1115	flush;
995	};	1116	};
996		1117
997	1;	1118	1;
998		1119

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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 1.90 by root, Mon Oct 30 23:30:00 2006 UTC

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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 1.90 by root, Mon Oct 30 23:30:00 2006 UTC