[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 1.86 by root, Sat Oct 28 23:32:29 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);
…		…
331	Asynchronously unlink (delete) a file and call the callback with the	393	Asynchronously unlink (delete) a file and call the callback with the
332	result code.	394	result code.
333		395
334	=item aio_mknod $path, $mode, $dev, $callback->($status)	396	=item aio_mknod $path, $mode, $dev, $callback->($status)
335		397
		398	[EXPERIMENTAL]
		399
336	Asynchronously create a device node (or fifo). See mknod(2): the only	400	Asynchronously create a device node (or fifo). See mknod(2).
337	portable value for C<$mode> is C<S_IFIFO> ored with permissions, and C<0>	401
338	for C<$dev>.	402	The only (POSIX-) portable way of calling this function is:
		403
		404	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
339		405
340	=item aio_link $srcpath, $dstpath, $callback->($status)	406	=item aio_link $srcpath, $dstpath, $callback->($status)
341		407
342	Asynchronously create a new link to the existing object at C<$srcpath> at	408	Asynchronously create a new link to the existing object at C<$srcpath> at
343	the path C<$dstpath> and call the callback with the result code.	409	the path C<$dstpath> and call the callback with the result code.
…		…
827		893
828	=back	894	=back
829		895
830	=head2 SUPPORT FUNCTIONS	896	=head2 SUPPORT FUNCTIONS
831		897
		898	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		899
832	=over 4	900	=over 4
833		901
834	=item $fileno = IO::AIO::poll_fileno	902	=item $fileno = IO::AIO::poll_fileno
835		903
836	Return the I<request result pipe file descriptor>. This filehandle must be	904	Return the I<request result pipe file descriptor>. This filehandle must be
…		…
840		908
841	See C<poll_cb> for an example.	909	See C<poll_cb> for an example.
842		910
843	=item IO::AIO::poll_cb	911	=item IO::AIO::poll_cb
844		912
845	Process all outstanding events on the result pipe. You have to call this	913	Process some outstanding events on the result pipe. You have to call this
846	regularly. Returns the number of events processed. Returns immediately	914	regularly. Returns the number of events processed. Returns immediately
847	when no events are outstanding.	915	when no events are outstanding. The amount of events processed depends on
		916	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
848		917
849	If not all requests were processed for whatever reason, the filehandle	918	If not all requests were processed for whatever reason, the filehandle
850	will still be ready when C<poll_cb> returns.	919	will still be ready when C<poll_cb> returns.
851		920
852	Example: Install an Event watcher that automatically calls	921	Example: Install an Event watcher that automatically calls
…		…
854		923
855	Event->io (fd => IO::AIO::poll_fileno,	924	Event->io (fd => IO::AIO::poll_fileno,
856	poll => 'r', async => 1,	925	poll => 'r', async => 1,
857	cb => \&IO::AIO::poll_cb);	926	cb => \&IO::AIO::poll_cb);
858		927
859	=item IO::AIO::poll_some $max_requests	928	=item IO::AIO::max_poll_reqs $nreqs
860		929
861	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests	930	=item IO::AIO::max_poll_time $seconds
862	at a time.
863		931
864	Useful if you want to ensure some level of interactiveness when perl is	932	These set the maximum number of requests (default C<0>, meaning infinity)
865	not fast enough to process all requests in time.	933	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		934	the maximum amount of time (default C<0>, meaning infinity) spent in
		935	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		936	of time C<poll_cb> is allowed to use).
		937
		938	Setting these is useful if you want to ensure some level of
		939	interactiveness when perl is not fast enough to process all requests in
		940	time.
		941
		942	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
866		943
867	Example: Install an Event watcher that automatically calls	944	Example: Install an Event watcher that automatically calls
868	IO::AIO::poll_some with low priority, to ensure that other parts of the	945	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.	946	program get the CPU sometimes even under high AIO load.
870		947
		948	# try not to spend much more than 0.1s in poll_cb
		949	IO::AIO::max_poll_time 0.1;
		950
		951	# use a low priority so other tasks have priority
871	Event->io (fd => IO::AIO::poll_fileno,	952	Event->io (fd => IO::AIO::poll_fileno,
872	poll => 'r', nice => 1,	953	poll => 'r', nice => 1,
873	cb => sub { IO::AIO::poll_some 256 });	954	cb => &IO::AIO::poll_cb);
874		955
875	=item IO::AIO::poll_wait	956	=item IO::AIO::poll_wait
876		957
877	Wait till the result filehandle becomes ready for reading (simply does a	958	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	959	C<select> on the filehandle. This is useful if you want to synchronously
879	for some requests to finish).	960	wait for some requests to finish).
880		961
881	See C<nreqs> for an example.	962	See C<nreqs> for an example.
882		963
		964	=item IO::AIO::poll
		965
		966	Waits until some requests have been handled.
		967
		968	Strictly equivalent to:
		969
		970	IO::AIO::poll_wait, IO::AIO::poll_cb
		971	if IO::AIO::nreqs;
		972
883	=item IO::AIO::nreqs	973	=item IO::AIO::flush
884		974
885	Returns the number of requests currently in the ready, execute or pending	975	Wait till all outstanding AIO requests have been handled.
886	states (i.e. for which their callback has not been invoked yet).
887		976
888	Example: wait till there are no outstanding requests anymore:	977	Strictly equivalent to:
889		978
890	IO::AIO::poll_wait, IO::AIO::poll_cb	979	IO::AIO::poll_wait, IO::AIO::poll_cb
891	while IO::AIO::nreqs;	980	while IO::AIO::nreqs;
892		981
893	=item IO::AIO::nready	982	=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		983
921	=item IO::AIO::min_parallel $nthreads	984	=item IO::AIO::min_parallel $nthreads
922		985
923	Set the minimum number of AIO threads to C<$nthreads>. The current	986	Set the minimum number of AIO threads to C<$nthreads>. The current
924	default is C<8>, which means eight asynchronous operations can execute	987	default is C<8>, which means eight asynchronous operations can execute
925	concurrently at any one time (the number of outstanding requests,	988	concurrently at any one time (the number of outstanding requests,
926	however, is unlimited).	989	however, is unlimited).
927		990
928	IO::AIO starts threads only on demand, when an AIO request is queued and	991	IO::AIO starts threads only on demand, when an AIO request is queued and
929	no free thread exists.	992	no free thread exists. Please note that queueing up a hundred requests can
		993	create demand for a hundred threads, even if it turns out that everything
		994	is in the cache and could have been processed faster by a single thread.
930		995
931	It is recommended to keep the number of threads relatively low, as some	996	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	997	Linux kernel versions will scale negatively with the number of threads
933	(higher parallelity => MUCH higher latency). With current Linux 2.6	998	(higher parallelity => MUCH higher latency). With current Linux 2.6
934	versions, 4-32 threads should be fine.	999	versions, 4-32 threads should be fine.
…		…
948	This module automatically runs C<max_parallel 0> at program end, to ensure	1013	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.	1014	that all threads are killed and that there are no outstanding requests.
950		1015
951	Under normal circumstances you don't need to call this function.	1016	Under normal circumstances you don't need to call this function.
952		1017
		1018	=item IO::AIO::max_idle $nthreads
		1019
		1020	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1021	threads that did not get a request to process within 10 seconds). That
		1022	means if a thread becomes idle while C<$nthreads> other threads are also
		1023	idle, it will free its resources and exit.
		1024
		1025	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1026	to allow for extremely high load situations, but want to free resources
		1027	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1028
		1029	The default is probably ok in most situations, especially if thread
		1030	creation is fast. If thread creation is very slow on your system you might
		1031	want to use larger values.
		1032
953	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1033	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
954		1034
955	This is a very bad function to use in interactive programs because it	1035	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	1036	blocks, and a bad way to reduce concurrency because it is inexact: Better
957	use an C<aio_group> together with a feed callback.	1037	use an C<aio_group> together with a feed callback.
…		…
966		1046
967	You can still queue as many requests as you want. Therefore,	1047	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	1048	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).	1049	as a stop gap to shield against fatal memory overflow (with large values).
970		1050
		1051	=head3 STATISTICAL INFORMATION
		1052
		1053	=item IO::AIO::nreqs
		1054
		1055	Returns the number of requests currently in the ready, execute or pending
		1056	states (i.e. for which their callback has not been invoked yet).
		1057
		1058	Example: wait till there are no outstanding requests anymore:
		1059
		1060	IO::AIO::poll_wait, IO::AIO::poll_cb
		1061	while IO::AIO::nreqs;
		1062
		1063	=item IO::AIO::nready
		1064
		1065	Returns the number of requests currently in the ready state (not yet
		1066	executed).
		1067
		1068	=item IO::AIO::npending
		1069
		1070	Returns the number of requests currently in the pending state (executed,
		1071	but not yet processed by poll_cb).
		1072
971	=back	1073	=back
972		1074
973	=cut	1075	=cut
974		1076
975	# support function to convert a fd into a perl filehandle	1077	# support function to convert a fd into a perl filehandle
…		…
989	}	1091	}
990		1092
991	min_parallel 8;	1093	min_parallel 8;
992		1094
993	END {	1095	END {
		1096	min_parallel 1;
994	flush;	1097	flush;
995	};	1098	};
996		1099
997	1;	1100	1;
998		1101

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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 1.86 by root, Sat Oct 28 23:32:29 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 1.86 by root, Sat Oct 28 23:32:29 2006 UTC