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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.71 by root, Tue Oct 24 11:57:30 2006 UTC vs.
Revision 1.72 by root, Tue Oct 24 14:25:53 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
…		…
591	=head2 IO::AIO::REQ CLASS	642	=head2 IO::AIO::REQ CLASS
592		643
593	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
594	called in non-void context.	645	called in non-void context.
595		646
596	A request always moves through the following five states in its lifetime,
597	in order: B<ready> (request has been created, but has not been executed
598	yet), B<execute> (request is currently being executed), B<pending>
599	(request has been executed but callback has not been called yet),
600	B<result> (results are being processed synchronously, includes calling the
601	callback) and B<done> (request has reached the end of its lifetime and
602	holds no resources anymore).
603
604	=over 4	647	=over 4
605		648
606	=item cancel $req	649	=item cancel $req
607		650
608	Cancels the request, if possible. Has the effect of skipping execution	651	Cancels the request, if possible. Has the effect of skipping execution
…		…
888	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:
889		932
890	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
891	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
892	the fork the parent simply leaves the quiescent state and continues	935	the fork the parent simply leaves the quiescent state and continues
893	request/result processing, while the child clears the request/result	936	request/result processing, while the child frees the request/result queue
894	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
895	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
896	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).
897		946
898	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
899	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
900	yet.	949	yet.
901		950
902	=head2 MEMORY USAGE	951	=head2 MEMORY USAGE
903		952
		953	Per-request usage:
		954
904	Each aio request uses - depending on your architecture - around 128 bytes	955	Each aio request uses - depending on your architecture - around 100-200
905	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
906	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
907	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.
908		960
909	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
910	problem.	962	problem.
911		963
912	Each thread needs a stack area which is usually around 16k, sometimes much	964	Per-thread usage:
913	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.
914		973
915	=head1 SEE ALSO	974	=head1 SEE ALSO
916		975
917	L<Coro::AIO>.	976	L<Coro::AIO>.
918		977

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.71 by root, Tue Oct 24 11:57:30 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 1.71 by root, Tue Oct 24 11:57:30 2006 UTC vs.
Revision 1.72 by root, Tue Oct 24 14:25:53 2006 UTC