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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.68 by root, Tue Oct 24 03:17:39 2006 UTC vs.
Revision 1.73 by root, Tue Oct 24 16:35:04 2006 UTC

…		…
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		55
56	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
57	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
58	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
59	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
60	on many operating systems. However, they are often not well-supported	60	functions available on many operating systems. However, they are often
61	(Linux doesn't allow them on normal files currently, for example),	61	not well-supported or restricted (Linux doesn't allow them on normal
62	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
63	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.
64		65
65	Although the module will work with in the presence of other threads,	66	Although the module will work with in the presence of other (Perl-)
66	it is currently not reentrant in any way, so use appropriate locking	67	threads, it is currently not reentrant in any way, so use appropriate
67	yourself, always call C<poll_cb> from within the same thread, or never	68	locking yourself, always call C<poll_cb> from within the same thread, or
68	call C<poll_cb> (or other 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).
69		120
70	=cut	121	=cut
71		122
72	package IO::AIO;	123	package IO::AIO;
73		124
…		…
81		132
82	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
83	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
84	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
85	aio_group aio_nop);	136	aio_group aio_nop);
86	our @EXPORT = (@AIO_REQ, qw(aioreq_pri));	137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
87	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
88	min_parallel max_parallel max_outstanding nreqs);	139	min_parallel max_parallel max_outstanding nreqs);
89		140
90	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
91		142
…		…
133	respectively. Requests with higher priority will be serviced first.	184	respectively. Requests with higher priority will be serviced first.
134		185
135	The priority will be reset to C<0> after each call to one of the C<aio_>	186	The priority will be reset to C<0> after each call to one of the C<aio_>
136	functions.	187	functions.
137		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
138	=item aio_open $pathname, $flags, $mode, $callback->($fh)	208	=item aio_open $pathname, $flags, $mode, $callback->($fh)
139		209
140	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
141	created filehandle for the file.	211	created filehandle for the file.
142		212
…		…
193	$_[0] > 0 or die "read error: $!";	263	$_[0] > 0 or die "read error: $!";
194	print "read $_[0] bytes: <$buffer>\n";	264	print "read $_[0] bytes: <$buffer>\n";
195	};	265	};
196		266
197	=item aio_move $srcpath, $dstpath, $callback->($status)	267	=item aio_move $srcpath, $dstpath, $callback->($status)
198
199	[EXPERIMENTAL due to internal aio_group use]
200		268
201	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
202	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
203	the C<0> (error) or C<-1> ok.	271	the C<0> (error) or C<-1> ok.
204		272
…		…
356		424
357	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
358	with the filenames.	426	with the filenames.
359		427
360	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	428	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
361
362	[EXPERIMENTAL due to internal aio_group use]
363		429
364	Scans a directory (similar to C<aio_readdir>) but additionally tries to	430	Scans a directory (similar to C<aio_readdir>) but additionally tries to
365	separate the entries of directory C<$path> into two sets of names, ones	431	separate the entries of directory C<$path> into two sets of names, ones
366	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
367	recurse into (everything else).	433	recurse into (everything else).
…		…
529		595
530	[EXPERIMENTAL]	596	[EXPERIMENTAL]
531		597
532	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
533	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
534	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.
535		602
536	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
537	for more info.	604	for more info.
538		605
539	Example:	606	Example:
…		…
558	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
559	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
560	entered their execution phase. This can be used to measure request	627	entered their execution phase. This can be used to measure request
561	latency.	628	latency.
562		629
563	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED	630	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
564		631
565	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
566	the request workers to sleep for the given time.	633	the request workers to sleep for the given time.
567		634
568	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
569	like sleep and file handle readable/writable, the overhead this creates	636	like sleep and file handle readable/writable, the overhead this creates is
570	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
571	under artificial I/O pressure.	638	except to put your application under artificial I/O pressure.
572		639
573	=back	640	=back
574		641
575	=head2 IO::AIO::REQ CLASS	642	=head2 IO::AIO::REQ CLASS
576		643
577	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
578	called in non-void context.	645	called in non-void context.
579
580	A request always moves through the following five states in its lifetime,
581	in order: B<ready> (request has been created, but has not been executed
582	yet), B<execute> (request is currently being executed), B<pending>
583	(request has been executed but callback has not been called yet),
584	B<result> (results are being processed synchronously, includes calling the
585	callback) and B<done> (request has reached the end of its lifetime and
586	holds no resources anymore).
587		646
588	=over 4	647	=over 4
589		648
590	=item cancel $req	649	=item cancel $req
591		650
…		…
872	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:
873		932
874	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
875	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
876	the fork the parent simply leaves the quiescent state and continues	935	the fork the parent simply leaves the quiescent state and continues
877	request/result processing, while the child clears the request/result	936	request/result processing, while the child frees the request/result queue
878	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
879	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
880	parent process has been reached again.	939	parent process has been reached again.
881		940
882	In short: the parent will, after a short pause, continue as if fork had	941	In short: the parent will, after a short pause, continue as if fork had
883	not been called, while the child will act as if IO::AIO has not been used	942	not been called, while the child will act as if IO::AIO has not been used
884	yet.	943	yet.
885		944
886	=head2 MEMORY USAGE	945	=head2 MEMORY USAGE
887		946
		947	Per-request usage:
		948
888	Each aio request uses - depending on your architecture - around 128 bytes	949	Each aio request uses - depending on your architecture - around 100-200
889	of memory. In addition, stat requests need a stat buffer (possibly a few	950	bytes of memory. In addition, stat requests need a stat buffer (possibly
890	hundred bytes). Perl scalars and other data passed into aio requests will	951	a few hundred bytes), readdir requires a result buffer and so on. Perl
891	also be locked.	952	scalars and other data passed into aio requests will also be locked and
		953	will consume memory till the request has entered the done state.
892		954
893	This is now awfully much, so queuing lots of requests is not usually a	955	This is now awfully much, so queuing lots of requests is not usually a
894	problem.	956	problem.
895		957
896	Each thread needs a stack area which is usually around 16k, sometimes much	958	Per-thread usage:
897	larger, depending on the OS.	959
		960	In the execution phase, some aio requests require more memory for
		961	temporary buffers, and each thread requires a stack and other data
		962	structures (usually around 16k-128k, depending on the OS).
		963
		964	=head1 KNOWN BUGS
		965
		966	Known bugs will be fixed in the next release.
898		967
899	=head1 SEE ALSO	968	=head1 SEE ALSO
900		969
901	L<Coro::AIO>.	970	L<Coro::AIO>.
902		971

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing IO-AIO/AIO.pm (file contents): Revision 1.68 by root, Tue Oct 24 03:17:39 2006 UTC vs. Revision 1.73 by root, Tue Oct 24 16:35:04 2006 UTC

Diff Legend

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.68 by root, Tue Oct 24 03:17:39 2006 UTC vs.
Revision 1.73 by root, Tue Oct 24 16:35:04 2006 UTC