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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.67 by root, Tue Oct 24 02:25:16 2006 UTC vs.
Revision 1.72 by root, Tue Oct 24 14:25:53 2006 UTC

…		…
18	};	18	};
19		19
20	# version 2+ has request and group objects	20	# version 2+ has request and group objects
21	use IO::AIO 2;	21	use IO::AIO 2;
22		22
		23	aioreq_pri 4; # give next request a very high priority
23	my $req = aio_unlink "/tmp/file", sub { };	24	my $req = aio_unlink "/tmp/file", sub { };
24	$req->cancel; # cancel request if still in queue	25	$req->cancel; # cancel request if still in queue
25		26
26	my $grp = aio_group sub { print "all stats done\n" };	27	my $grp = aio_group sub { print "all stats done\n" };
27	add $grp aio_stat "..." for ...;	28	add $grp aio_stat "..." for ...;
…		…
50	=head1 DESCRIPTION	51	=head1 DESCRIPTION
51		52
52	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
53	operating system supports.	54	operating system supports.
54		55
55	Currently, a number of threads are started that execute your read/writes	56	In this version, a number of threads are started that execute your
56	and signal their completion. You don't need thread support in perl, and	57	requests and signal their completion. You don't need thread support
57	the threads created by this module will not be visible to perl. In the	58	in perl, and the threads created by this module will not be visible
58	future, this module might make use of the native aio functions available	59	to perl. In the future, this module might make use of the native aio
59	on many operating systems. However, they are often not well-supported	60	functions available on many operating systems. However, they are often
60	(Linux doesn't allow them on normal files currently, for example),	61	not well-supported or restricted (Linux doesn't allow them on normal
61	and they would only support aio_read and aio_write, so the remaining	62	files currently, for example), and they would only support aio_read and
62	functionality would have to be implemented using threads anyway.	63	aio_write, so the remaining functionality would have to be implemented
		64	using threads anyway.
63		65
64	Although the module will work with in the presence of other threads, it is	66	Although the module will work with in the presence of other (Perl-)
65	currently not reentrant, so use appropriate locking yourself, always call	67	threads, it is currently not reentrant in any way, so use appropriate
66	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	68	locking yourself, always call C<poll_cb> from within the same thread, or
67	C<aio_> functions) recursively.	69	never call C<poll_cb> (or other C<aio_> functions) recursively.
		70
		71	=head1 REQUEST ANATOMY AND LIFETIME
		72
		73	Every C<aio_*> function creates a request. which is a C data structure not
		74	directly visible to Perl.
		75
		76	If called in non-void context, every request function returns a Perl
		77	object representing the request. In void context, nothing is returned,
		78	which saves a bit of memory.
		79
		80	The perl object is a fairly standard ref-to-hash object. The hash contents
		81	are not used by IO::AIO so you are free to store anything you like in it.
		82
		83	During their existance, aio requests travel through the following states,
		84	in order:
		85
		86	=over 4
		87
		88	=item ready
		89
		90	Immediately after a request is created it is put into the ready state,
		91	waiting for a thread to execute it.
		92
		93	=item execute
		94
		95	A thread has accepted the request for processing and is currently
		96	executing it (e.g. blocking in read).
		97
		98	=item pending
		99
		100	The request has been executed and is waiting for result processing.
		101
		102	While request submission and execution is fully asynchronous, result
		103	processing is not and relies on the perl interpreter calling C<poll_cb>
		104	(or another function with the same effect).
		105
		106	=item result
		107
		108	The request results are processed synchronously by C<poll_cb>.
		109
		110	The C<poll_cb> function will process all outstanding aio requests by
		111	calling their callbacks, freeing memory associated with them and managing
		112	any groups they are contained in.
		113
		114	=item done
		115
		116	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
		118	aio request is severed and calling its methods will either do nothing or
		119	result in a runtime error).
68		120
69	=cut	121	=cut
70		122
71	package IO::AIO;	123	package IO::AIO;
72		124
…		…
80		132
81	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	133	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
82	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	134	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	135	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
84	aio_group aio_nop);	136	aio_group aio_nop);
85	our @EXPORT = (@AIO_REQ, qw(aioreq_pri));	137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
86	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
87	min_parallel max_parallel max_outstanding nreqs);	139	min_parallel max_parallel max_outstanding nreqs);
88		140
89	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
90		142
…		…
123	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	175	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
124	use something else.	176	use something else.
125		177
126	=over 4	178	=over 4
127		179
		180	=item aioreq_pri $pri
		181
		182	Sets the priority for the next aio request. The default priority
		183	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,
		184	respectively. Requests with higher priority will be serviced first.
		185
		186	The priority will be reset to C<0> after each call to one of the C<aio_>
		187	functions.
		188
		189	Example: open a file with low priority, then read something from it with
		190	higher priority so the read request is serviced before other low priority
		191	open requests (potentially spamming the cache):
		192
		193	aioreq_pri -3;
		194	aio_open ..., sub {
		195	return unless $_[0];
		196
		197	aioreq_pri -2;
		198	aio_read $_[0], ..., sub {
		199	...
		200	};
		201	};
		202
		203	=item aioreq_nice $pri_adjust
		204
		205	Similar to C<aioreq_pri>, but subtracts the given value from the current
		206	priority, so effects are cumulative.
		207
128	=item aio_open $pathname, $flags, $mode, $callback->($fh)	208	=item aio_open $pathname, $flags, $mode, $callback->($fh)
129		209
130	Asynchronously open or create a file and call the callback with a newly	210	Asynchronously open or create a file and call the callback with a newly
131	created filehandle for the file.	211	created filehandle for the file.
132		212
…		…
183	$_[0] > 0 or die "read error: $!";	263	$_[0] > 0 or die "read error: $!";
184	print "read $_[0] bytes: <$buffer>\n";	264	print "read $_[0] bytes: <$buffer>\n";
185	};	265	};
186		266
187	=item aio_move $srcpath, $dstpath, $callback->($status)	267	=item aio_move $srcpath, $dstpath, $callback->($status)
188
189	[EXPERIMENTAL due to internal aio_group use]
190		268
191	Try to move the I<file> (directories not supported as either source or	269	Try to move the I<file> (directories not supported as either source or
192	destination) from C<$srcpath> to C<$dstpath> and call the callback with	270	destination) from C<$srcpath> to C<$dstpath> and call the callback with
193	the C<0> (error) or C<-1> ok.	271	the C<0> (error) or C<-1> ok.
194		272
…		…
346		424
347	The callback a single argument which is either C<undef> or an array-ref	425	The callback a single argument which is either C<undef> or an array-ref
348	with the filenames.	426	with the filenames.
349		427
350	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	428	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
351
352	[EXPERIMENTAL due to internal aio_group use]
353		429
354	Scans a directory (similar to C<aio_readdir>) but additionally tries to	430	Scans a directory (similar to C<aio_readdir>) but additionally tries to
355	separate the entries of directory C<$path> into two sets of names, ones	431	separate the entries of directory C<$path> into two sets of names, ones
356	you can recurse into (directories or links to them), and ones you cannot	432	you can recurse into (directories or links to them), and ones you cannot
357	recurse into (everything else).	433	recurse into (everything else).
…		…
519		595
520	[EXPERIMENTAL]	596	[EXPERIMENTAL]
521		597
522	This is a very special aio request: Instead of doing something, it is a	598	This is a very special aio request: Instead of doing something, it is a
523	container for other aio requests, which is useful if you want to bundle	599	container for other aio requests, which is useful if you want to bundle
524	many requests into a single, composite, request.	600	many requests into a single, composite, request with a definite callback
		601	and the ability to cancel the whole request with its subrequests.
525		602
526	Returns an object of class L<IO::AIO::GRP>. See its documentation below	603	Returns an object of class L<IO::AIO::GRP>. See its documentation below
527	for more info.	604	for more info.
528		605
529	Example:	606	Example:
…		…
548	phase and still requires a worker thread. Thus, the callback will not	625	phase and still requires a worker thread. Thus, the callback will not
549	be executed immediately but only after other requests in the queue have	626	be executed immediately but only after other requests in the queue have
550	entered their execution phase. This can be used to measure request	627	entered their execution phase. This can be used to measure request
551	latency.	628	latency.
552		629
553	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED	630	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
554		631
555	Mainly used for debugging and benchmarking, this aio request puts one of	632	Mainly used for debugging and benchmarking, this aio request puts one of
556	the request workers to sleep for the given time.	633	the request workers to sleep for the given time.
557		634
558	While it is theoretically handy to have simple I/O scheduling requests	635	While it is theoretically handy to have simple I/O scheduling requests
559	like sleep and file handle readable/writable, the overhead this creates	636	like sleep and file handle readable/writable, the overhead this creates is
560	is immense, so do not use this function except to put your application	637	immense (it blocks a thread for a long time) so do not use this function
561	under artificial I/O pressure.	638	except to put your application under artificial I/O pressure.
562		639
563	=back	640	=back
564		641
565	=head2 IO::AIO::REQ CLASS	642	=head2 IO::AIO::REQ CLASS
566		643
567	All non-aggregate C<aio_*> functions return an object of this class when	644	All non-aggregate C<aio_*> functions return an object of this class when
568	called in non-void context.	645	called in non-void context.
569
570	A request always moves through the following five states in its lifetime,
571	in order: B<ready> (request has been created, but has not been executed
572	yet), B<execute> (request is currently being executed), B<pending>
573	(request has been executed but callback has not been called yet),
574	B<result> (results are being processed synchronously, includes calling the
575	callback) and B<done> (request has reached the end of its lifetime and
576	holds no resources anymore).
577		646
578	=over 4	647	=over 4
579		648
580	=item cancel $req	649	=item cancel $req
581		650
…		…
681	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	750	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
682	requests, delaying any later requests for a long time.	751	requests, delaying any later requests for a long time.
683		752
684	To avoid this, and allow incremental generation of requests, you can	753	To avoid this, and allow incremental generation of requests, you can
685	instead a group and set a feeder on it that generates those requests. The	754	instead a group and set a feeder on it that generates those requests. The
686	feed callback will be called whenever there are few enough (see C<feed_limit>,	755	feed callback will be called whenever there are few enough (see C<limit>,
687	below) requests active in the group itself and is expected to queue more	756	below) requests active in the group itself and is expected to queue more
688	requests.	757	requests.
689		758
690	The feed can queue as many requests as it likes (i.e. C<add> does not	759	The feed callback can queue as many requests as it likes (i.e. C<add> does
691	impose any limits).	760	not impose any limits).
692		761
693	If the feed does not queue more requests when called, it will be	762	If the feed does not queue more requests when called, it will be
694	automatically removed from the group.	763	automatically removed from the group.
695		764
696	If the feed limit is C<0>, it will be set to C<2> automatically.	765	If the feed limit is C<0>, it will be set to C<2> automatically.
…		…
698	Example:	767	Example:
699		768
700	# stat all files in @files, but only ever use four aio requests concurrently:	769	# stat all files in @files, but only ever use four aio requests concurrently:
701		770
702	my $grp = aio_group sub { print "finished\n" };	771	my $grp = aio_group sub { print "finished\n" };
703	feed_limit $grp 4;	772	limit $grp 4;
704	feed $grp sub {	773	feed $grp sub {
705	my $file = pop @files	774	my $file = pop @files
706	or return;	775	or return;
707		776
708	add $grp aio_stat $file, sub { ... };	777	add $grp aio_stat $file, sub { ... };
709	};	778	};
710		779
711	=item feed_limit $grp $num	780	=item limit $grp $num
712		781
713	Sets the feeder limit for the group: The feeder will be called whenever	782	Sets the feeder limit for the group: The feeder will be called whenever
714	the group contains less than this many requests.	783	the group contains less than this many requests.
715		784
716	Setting the limit to C<0> will pause the feeding process.	785	Setting the limit to C<0> will pause the feeding process.
…		…
862	This module should do "the right thing" when the process using it forks:	931	This module should do "the right thing" when the process using it forks:
863		932
864	Before the fork, IO::AIO enters a quiescent state where no requests	933	Before the fork, IO::AIO enters a quiescent state where no requests
865	can be added in other threads and no results will be processed. After	934	can be added in other threads and no results will be processed. After
866	the fork the parent simply leaves the quiescent state and continues	935	the fork the parent simply leaves the quiescent state and continues
867	request/result processing, while the child clears the request/result	936	request/result processing, while the child frees the request/result queue
868	queue (so the requests started before the fork will only be handled in	937	(so that the requests started before the fork will only be handled in the
869	the parent). Threads will be started on demand until the limit ste in the	938	parent). Threads will be started on demand until the limit set in the
870	parent process has been reached again.	939	parent process has been reached again.
		940
		941	Temporary memory that was allocated for request processing is not
		942	reclaimed in the child, however. While this is possible in some cases, it
		943	is almost impossible in others (threads are evil you know), so you will
		944	have to live with it. This is around 64k buffer (for sendfile, readahead
		945	emulation) + the size of the directory being scanned (readdir).
871		946
872	In short: the parent will, after a short pause, continue as if fork had	947	In short: the parent will, after a short pause, continue as if fork had
873	not been called, while the child will act as if IO::AIO has not been used	948	not been called, while the child will act as if IO::AIO has not been used
874	yet.	949	yet.
875		950
876	=head2 MEMORY USAGE	951	=head2 MEMORY USAGE
877		952
		953	Per-request usage:
		954
878	Each aio request uses - depending on your architecture - around 128 bytes	955	Each aio request uses - depending on your architecture - around 100-200
879	of memory. In addition, stat requests need a stat buffer (possibly a few	956	bytes of memory. In addition, stat requests need a stat buffer (possibly
880	hundred bytes). Perl scalars and other data passed into aio requests will	957	a few hundred bytes), readdir requires a result buffer and so on. Perl
881	also be locked.	958	scalars and other data passed into aio requests will also be locked and
		959	will consume memory till the request has entered the done state.
882		960
883	This is now awfully much, so queuing lots of requests is not usually a	961	This is now awfully much, so queuing lots of requests is not usually a
884	problem.	962	problem.
885		963
886	Each thread needs a stack area which is usually around 16k, sometimes much	964	Per-thread usage:
887	larger, depending on the OS.	965
		966	In the execution phase, some aio requests require more memory for
		967	temporary buffers, and each thread requires a stack and other data
		968	structures (usually around 16k-128k, depending on the OS).
		969
		970	=head1 KNOWN BUGS
		971
		972	See FORK BEHAVIOUR, above.
888		973
889	=head1 SEE ALSO	974	=head1 SEE ALSO
890		975
891	L<Coro>, L<Linux::AIO> (obsolete).	976	L<Coro::AIO>.
892		977
893	=head1 AUTHOR	978	=head1 AUTHOR
894		979
895	Marc Lehmann <schmorp@schmorp.de>	980	Marc Lehmann <schmorp@schmorp.de>
896	http://home.schmorp.de/	981	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.67 by root, Tue Oct 24 02:25:16 2006 UTC vs. Revision 1.72 by root, Tue Oct 24 14:25:53 2006 UTC

Diff Legend

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.67 by root, Tue Oct 24 02:25:16 2006 UTC vs.
Revision 1.72 by root, Tue Oct 24 14:25:53 2006 UTC