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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.56 by root, Sun Oct 22 00:53:47 2006 UTC vs.
Revision 1.80 by root, Thu Oct 26 16:28:33 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 your libc or	57	requests and signal their completion. You don't need thread support
57	perl, and the threads created by this module will not be visible to the	58	in perl, and the threads created by this module will not be visible
58	pthreads library. In the future, this module might make use of the native	59	to perl. In the future, this module might make use of the native aio
59	aio functions available on many operating systems. However, they are often	60	functions available on many operating systems. However, they are often
60	not well-supported (Linux doesn't allow them on normal files currently,	61	not well-supported or restricted (Linux doesn't allow them on normal
61	for example), and they would only support aio_read and aio_write, so the	62	files currently, for example), and they would only support aio_read and
62	remaining 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
…		…
76	use base 'Exporter';	128	use base 'Exporter';
77		129
78	BEGIN {	130	BEGIN {
79	our $VERSION = '2.0';	131	our $VERSION = '2.0';
80		132
81	our @EXPORT = 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);	136	aio_group aio_nop);
85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		139	min_parallel max_parallel nreqs nready npending);
86		140
87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
88		142
89	require XSLoader;	143	require XSLoader;
90	XSLoader::load ("IO::AIO", $VERSION);	144	XSLoader::load ("IO::AIO", $VERSION);
…		…
120	your pathnames to the locale (or other) encoding in effect in the user	174	your pathnames to the locale (or other) encoding in effect in the user
121	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)
122	use something else.	176	use something else.
123		177
124	=over 4	178	=over 4
		179
		180	=item $prev_pri = aioreq_pri [$pri]
		181
		182	Returns the priority value that would be used for the next request and, if
		183	C<$pri> is given, sets the priority for the next aio request.
		184
		185	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		186	and C<4>, respectively. Requests with higher priority will be serviced
		187	first.
		188
		189	The priority will be reset to C<0> after each call to one of the C<aio_*>
		190	functions.
		191
		192	Example: open a file with low priority, then read something from it with
		193	higher priority so the read request is serviced before other low priority
		194	open requests (potentially spamming the cache):
		195
		196	aioreq_pri -3;
		197	aio_open ..., sub {
		198	return unless $_[0];
		199
		200	aioreq_pri -2;
		201	aio_read $_[0], ..., sub {
		202	...
		203	};
		204	};
		205
		206	=item aioreq_nice $pri_adjust
		207
		208	Similar to C<aioreq_pri>, but subtracts the given value from the current
		209	priority, so effects are cumulative.
125		210
126	=item aio_open $pathname, $flags, $mode, $callback->($fh)	211	=item aio_open $pathname, $flags, $mode, $callback->($fh)
127		212
128	Asynchronously open or create a file and call the callback with a newly	213	Asynchronously open or create a file and call the callback with a newly
129	created filehandle for the file.	214	created filehandle for the file.
…		…
201	=cut	286	=cut
202		287
203	sub aio_move($$$) {	288	sub aio_move($$$) {
204	my ($src, $dst, $cb) = @_;	289	my ($src, $dst, $cb) = @_;
205		290
		291	my $pri = aioreq_pri;
206	my $grp = aio_group;	292	my $grp = aio_group $cb;
207		293
		294	aioreq_pri $pri;
208	add $grp aio_rename $src, $dst, sub {	295	add $grp aio_rename $src, $dst, sub {
209	if ($_[0] && $! == EXDEV) {	296	if ($_[0] && $! == EXDEV) {
		297	aioreq_pri $pri;
210	add $grp aio_open $src, O_RDONLY, 0, sub {	298	add $grp aio_open $src, O_RDONLY, 0, sub {
211	if (my $src_fh = $_[0]) {	299	if (my $src_fh = $_[0]) {
212	my @stat = stat $src_fh;	300	my @stat = stat $src_fh;
213		301
		302	aioreq_pri $pri;
214	add $grp aio_open $dst, O_WRONLY, 0200, sub {	303	add $grp aio_open $dst, O_WRONLY, 0200, sub {
215	if (my $dst_fh = $_[0]) {	304	if (my $dst_fh = $_[0]) {
		305	aioreq_pri $pri;
216	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	306	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
217	close $src_fh;	307	close $src_fh;
218		308
219	if ($_[0] == $stat[7]) {	309	if ($_[0] == $stat[7]) {
220	utime $stat[8], $stat[9], $dst;	310	utime $stat[8], $stat[9], $dst;
221	chmod $stat[2] & 07777, $dst_fh;	311	chmod $stat[2] & 07777, $dst_fh;
222	chown $stat[4], $stat[5], $dst_fh;	312	chown $stat[4], $stat[5], $dst_fh;
223	close $dst_fh;	313	close $dst_fh;
224		314
		315	aioreq_pri $pri;
225	add $grp aio_unlink $src, sub {	316	add $grp aio_unlink $src, sub {
226	$cb->($_[0]);	317	$grp->result ($_[0]);
227	};	318	};
228	} else {	319	} else {
229	my $errno = $!;	320	my $errno = $!;
		321	aioreq_pri $pri;
230	add $grp aio_unlink $dst, sub {	322	add $grp aio_unlink $dst, sub {
231	$! = $errno;	323	$! = $errno;
232	$cb->(-1);	324	$grp->result (-1);
233	};	325	};
234	}	326	}
235	};	327	};
236	} else {	328	} else {
237	$cb->(-1);	329	$grp->result (-1);
238	}	330	}
239	},	331	},
240		332
241	} else {	333	} else {
242	$cb->(-1);	334	$grp->result (-1);
243	}	335	}
244	};	336	};
245	} else {	337	} else {
246	$cb->($_[0]);	338	$grp->result ($_[0]);
247	}	339	}
248	};	340	};
249		341
250	$grp	342	$grp
251	}	343	}
…		…
344	with the filenames.	436	with the filenames.
345		437
346	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	438	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
347		439
348	Scans a directory (similar to C<aio_readdir>) but additionally tries to	440	Scans a directory (similar to C<aio_readdir>) but additionally tries to
349	separate the entries of directory C<$path> into two sets of names, ones	441	efficiently separate the entries of directory C<$path> into two sets of
350	you can recurse into (directories or links to them), and ones you cannot	442	names, directories you can recurse into (directories), and ones you cannot
351	recurse into (everything else).	443	recurse into (everything else, including symlinks to directories).
352		444
353	C<aio_scandir> is a composite request that consists of many sub	445	C<aio_scandir> is a composite request that creates of many sub requests_
354	requests. C<$maxreq> specifies the maximum number of outstanding aio	446	C<$maxreq> specifies the maximum number of outstanding aio requests that
355	requests that this function generates. If it is C<< <= 0 >>, then a	447	this function generates. If it is C<< <= 0 >>, then a suitable default
356	suitable default will be chosen (currently 8).	448	will be chosen (currently 6).
357		449
358	On error, the callback is called without arguments, otherwise it receives	450	On error, the callback is called without arguments, otherwise it receives
359	two array-refs with path-relative entry names.	451	two array-refs with path-relative entry names.
360		452
361	Example:	453	Example:
…		…
398	=cut	490	=cut
399		491
400	sub aio_scandir($$$) {	492	sub aio_scandir($$$) {
401	my ($path, $maxreq, $cb) = @_;	493	my ($path, $maxreq, $cb) = @_;
402		494
		495	my $pri = aioreq_pri;
		496
403	my $grp = aio_group;	497	my $grp = aio_group $cb;
404		498
405	$maxreq = 8 if $maxreq <= 0;	499	$maxreq = 6 if $maxreq <= 0;
406		500
407	# stat once	501	# stat once
		502	aioreq_pri $pri;
408	add $grp aio_stat $path, sub {	503	add $grp aio_stat $path, sub {
409	return $cb->() if $_[0];	504	return $grp->result () if $_[0];
410	my $now = time;	505	my $now = time;
411	my $hash1 = join ":", (stat _)[0,1,3,7,9];	506	my $hash1 = join ":", (stat _)[0,1,3,7,9];
412		507
413	# read the directory entries	508	# read the directory entries
		509	aioreq_pri $pri;
414	add $grp aio_readdir $path, sub {	510	add $grp aio_readdir $path, sub {
415	my $entries = shift	511	my $entries = shift
416	or return $cb->();	512	or return $grp->result ();
417		513
418	# stat the dir another time	514	# stat the dir another time
		515	aioreq_pri $pri;
419	add $grp aio_stat $path, sub {	516	add $grp aio_stat $path, sub {
420	my $hash2 = join ":", (stat _)[0,1,3,7,9];	517	my $hash2 = join ":", (stat _)[0,1,3,7,9];
421		518
422	my $ndirs;	519	my $ndirs;
423		520
…		…
426	$ndirs = -1;	523	$ndirs = -1;
427	} else {	524	} else {
428	# if nlink == 2, we are finished	525	# if nlink == 2, we are finished
429	# on non-posix-fs's, we rely on nlink < 2	526	# on non-posix-fs's, we rely on nlink < 2
430	$ndirs = (stat _)[3] - 2	527	$ndirs = (stat _)[3] - 2
431	or return $cb->([], $entries);	528	or return $grp->result ([], $entries);
432	}	529	}
433		530
434	# sort into likely dirs and likely nondirs	531	# sort into likely dirs and likely nondirs
435	# dirs == files without ".", short entries first	532	# dirs == files without ".", short entries first
436	$entries = [map $_->[0],	533	$entries = [map $_->[0],
…		…
438	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	535	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
439	@$entries];	536	@$entries];
440		537
441	my (@dirs, @nondirs);	538	my (@dirs, @nondirs);
442		539
443	my ($statcb, $schedcb);	540	my $statgrp = add $grp aio_group sub {
444	my $nreq = 0;	541	$grp->result (\@dirs, \@nondirs);
		542	};
445		543
446	$schedcb = sub {	544	limit $statgrp $maxreq;
447	if (@$entries) {	545	feed $statgrp sub {
448	if ($nreq < $maxreq) {	546	return unless @$entries;
449	my $ent = pop @$entries;	547	my $entry = pop @$entries;
		548
		549	aioreq_pri $pri;
		550	add $statgrp aio_stat "$path/$entry/.", sub {
		551	if ($_[0] < 0) {
		552	push @nondirs, $entry;
		553	} else {
		554	# need to check for real directory
		555	aioreq_pri $pri;
		556	add $statgrp aio_lstat "$path/$entry", sub {
		557	if (-d _) {
		558	push @dirs, $entry;
		559
		560	unless (--$ndirs) {
		561	push @nondirs, @$entries;
		562	feed $statgrp;
		563	}
		564	} else {
		565	push @nondirs, $entry;
		566	}
450	$nreq++;	567	}
451	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
452	}	568	}
453	} elsif (!$nreq) {
454	# finished
455	undef $statcb;
456	undef $schedcb;
457	$cb->(\@dirs, \@nondirs) if $cb;
458	undef $cb;
459	}	569	};
460	};	570	};
461	$statcb = sub {
462	my ($status, $entry) = @_;
463
464	if ($status < 0) {
465	$nreq--;
466	push @nondirs, $entry;
467	&$schedcb;
468	} else {
469	# need to check for real directory
470	add $grp aio_lstat "$path/$entry", sub {
471	$nreq--;
472
473	if (-d _) {
474	push @dirs, $entry;
475
476	if (!--$ndirs) {
477	push @nondirs, @$entries;
478	$entries = [];
479	}
480	} else {
481	push @nondirs, $entry;
482	}
483
484	&$schedcb;
485	}
486	}
487	};
488
489	&$schedcb while @$entries && $nreq < $maxreq;
490	};	571	};
491	};	572	};
492	};	573	};
493		574
494	$grp	575	$grp
…		…
505	callback with the fdatasync result code.	586	callback with the fdatasync result code.
506		587
507	If this call isn't available because your OS lacks it or it couldn't be	588	If this call isn't available because your OS lacks it or it couldn't be
508	detected, it will be emulated by calling C<fsync> instead.	589	detected, it will be emulated by calling C<fsync> instead.
509		590
510	=item aio_group $callback->()	591	=item aio_group $callback->(...)
511
512	[EXPERIMENTAL]
513		592
514	This is a very special aio request: Instead of doing something, it is a	593	This is a very special aio request: Instead of doing something, it is a
515	container for other aio requests, which is useful if you want to bundle	594	container for other aio requests, which is useful if you want to bundle
516	many requests into a single, composite, request.	595	many requests into a single, composite, request with a definite callback
		596	and the ability to cancel the whole request with its subrequests.
517		597
518	Returns an object of class L<IO::AIO::GRP>. See its documentation below	598	Returns an object of class L<IO::AIO::GRP>. See its documentation below
519	for more info.	599	for more info.
520		600
521	Example:	601	Example:
…		…
527	add $grp	607	add $grp
528	(aio_stat ...),	608	(aio_stat ...),
529	(aio_stat ...),	609	(aio_stat ...),
530	...;	610	...;
531		611
		612	=item aio_nop $callback->()
		613
		614	This is a special request - it does nothing in itself and is only used for
		615	side effects, such as when you want to add a dummy request to a group so
		616	that finishing the requests in the group depends on executing the given
		617	code.
		618
		619	While this request does nothing, it still goes through the execution
		620	phase and still requires a worker thread. Thus, the callback will not
		621	be executed immediately but only after other requests in the queue have
		622	entered their execution phase. This can be used to measure request
		623	latency.
		624
532	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED	625	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
533		626
534	Mainly used for debugging and benchmarking, this aio request puts one of	627	Mainly used for debugging and benchmarking, this aio request puts one of
535	the request workers to sleep for the given time.	628	the request workers to sleep for the given time.
536		629
537	While it is theoretically handy to have simple I/O scheduling requests	630	While it is theoretically handy to have simple I/O scheduling requests
538	like sleep and file handle readable/writable, the overhead this creates	631	like sleep and file handle readable/writable, the overhead this creates is
539	is immense, so do not use this function except to put your application	632	immense (it blocks a thread for a long time) so do not use this function
540	under artificial I/O pressure.	633	except to put your application under artificial I/O pressure.
541		634
542	=back	635	=back
543		636
544	=head2 IO::AIO::REQ CLASS	637	=head2 IO::AIO::REQ CLASS
545		638
546	All non-aggregate C<aio_*> functions return an object of this class when	639	All non-aggregate C<aio_*> functions return an object of this class when
547	called in non-void context.	640	called in non-void context.
548		641
549	A request always moves through the following five states in its lifetime,
550	in order: B<ready> (request has been created, but has not been executed
551	yet), B<execute> (request is currently being executed), B<pending>
552	(request has been executed but callback has not been called yet),
553	B<result> (results are being processed synchronously, includes calling the
554	callback) and B<done> (request has reached the end of its lifetime and
555	holds no resources anymore).
556
557	=over 4	642	=over 4
558		643
559	=item $req->cancel	644	=item cancel $req
560		645
561	Cancels the request, if possible. Has the effect of skipping execution	646	Cancels the request, if possible. Has the effect of skipping execution
562	when entering the B<execute> state and skipping calling the callback when	647	when entering the B<execute> state and skipping calling the callback when
563	entering the the B<result> state, but will leave the request otherwise	648	entering the the B<result> state, but will leave the request otherwise
564	untouched. That means that requests that currently execute will not be	649	untouched. That means that requests that currently execute will not be
565	stopped and resources held by the request will not be freed prematurely.	650	stopped and resources held by the request will not be freed prematurely.
566		651
		652	=item cb $req $callback->(...)
		653
		654	Replace (or simply set) the callback registered to the request.
		655
567	=back	656	=back
568		657
569	=head2 IO::AIO::GRP CLASS	658	=head2 IO::AIO::GRP CLASS
570		659
571	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to	660	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
…		…
585	You add requests by calling the C<add> method with one or more	674	You add requests by calling the C<add> method with one or more
586	C<IO::AIO::REQ> objects:	675	C<IO::AIO::REQ> objects:
587		676
588	$grp->add (aio_unlink "...");	677	$grp->add (aio_unlink "...");
589		678
590	add $grp aio_stat "...", sub { ... };	679	add $grp aio_stat "...", sub {
		680	$_[0] or return $grp->result ("error");
		681
		682	# add another request dynamically, if first succeeded
		683	add $grp aio_open "...", sub {
		684	$grp->result ("ok");
		685	};
		686	};
591		687
592	This makes it very easy to create composite requests (see the source of	688	This makes it very easy to create composite requests (see the source of
593	C<aio_move> for an application) that work and feel like simple requests.	689	C<aio_move> for an application) that work and feel like simple requests.
594		690
		691	=over 4
		692
595	The IO::AIO::GRP objects will be cleaned up during calls to	693	=item * The IO::AIO::GRP objects will be cleaned up during calls to
596	C<IO::AIO::poll_cb>, just like any other request.	694	C<IO::AIO::poll_cb>, just like any other request.
597		695
598	They can be canceled like any other request. Canceling will cancel not	696	=item * They can be canceled like any other request. Canceling will cancel not
599	just the request itself, but also all requests it contains.	697	only the request itself, but also all requests it contains.
600		698
601	They can also can also be added to other IO::AIO::GRP objects.	699	=item * They can also can also be added to other IO::AIO::GRP objects.
		700
		701	=item * You must not add requests to a group from within the group callback (or
		702	any later time).
		703
		704	=back
602		705
603	Their lifetime, simplified, looks like this: when they are empty, they	706	Their lifetime, simplified, looks like this: when they are empty, they
604	will finish very quickly. If they contain only requests that are in the	707	will finish very quickly. If they contain only requests that are in the
605	C<done> state, they will also finish. Otherwise they will continue to	708	C<done> state, they will also finish. Otherwise they will continue to
606	exist.	709	exist.
607		710
		711	That means after creating a group you have some time to add requests. And
		712	in the callbacks of those requests, you can add further requests to the
		713	group. And only when all those requests have finished will the the group
		714	itself finish.
		715
608	=over 4	716	=over 4
609		717
		718	=item add $grp ...
		719
610	=item $grp->add (...)	720	=item $grp->add (...)
611		721
612	=item add $grp ...	722	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		723	be added, including other groups, as long as you do not create circular
		724	dependencies.
613		725
614	Add one or more	726	Returns all its arguments.
615	Cancels the request, if possible. Has the effect of skipping execution	727
616	when entering the B<execute> state and skipping calling the callback when	728	=item $grp->cancel_subs
617	entering the the B<result> state, but will leave the request otherwise	729
618	untouched. That means that requests that currently execute will not be	730	Cancel all subrequests and clears any feeder, but not the group request
619	stopped and resources held by the request will not be freed prematurely.	731	itself. Useful when you queued a lot of events but got a result early.
		732
		733	=item $grp->result (...)
		734
		735	Set the result value(s) that will be passed to the group callback when all
		736	subrequests have finished and set thre groups errno to the current value
		737	of errno (just like calling C<errno> without an error number). By default,
		738	no argument will be passed and errno is zero.
		739
		740	=item $grp->errno ([$errno])
		741
		742	Sets the group errno value to C<$errno>, or the current value of errno
		743	when the argument is missing.
		744
		745	Every aio request has an associated errno value that is restored when
		746	the callback is invoked. This method lets you change this value from its
		747	default (0).
		748
		749	Calling C<result> will also set errno, so make sure you either set C<$!>
		750	before the call to C<result>, or call c<errno> after it.
		751
		752	=item feed $grp $callback->($grp)
		753
		754	Sets a feeder/generator on this group: every group can have an attached
		755	generator that generates requests if idle. The idea behind this is that,
		756	although you could just queue as many requests as you want in a group,
		757	this might starve other requests for a potentially long time. For
		758	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		759	requests, delaying any later requests for a long time.
		760
		761	To avoid this, and allow incremental generation of requests, you can
		762	instead a group and set a feeder on it that generates those requests. The
		763	feed callback will be called whenever there are few enough (see C<limit>,
		764	below) requests active in the group itself and is expected to queue more
		765	requests.
		766
		767	The feed callback can queue as many requests as it likes (i.e. C<add> does
		768	not impose any limits).
		769
		770	If the feed does not queue more requests when called, it will be
		771	automatically removed from the group.
		772
		773	If the feed limit is C<0>, it will be set to C<2> automatically.
		774
		775	Example:
		776
		777	# stat all files in @files, but only ever use four aio requests concurrently:
		778
		779	my $grp = aio_group sub { print "finished\n" };
		780	limit $grp 4;
		781	feed $grp sub {
		782	my $file = pop @files
		783	or return;
		784
		785	add $grp aio_stat $file, sub { ... };
		786	};
		787
		788	=item limit $grp $num
		789
		790	Sets the feeder limit for the group: The feeder will be called whenever
		791	the group contains less than this many requests.
		792
		793	Setting the limit to C<0> will pause the feeding process.
620		794
621	=back	795	=back
622		796
623	=head2 SUPPORT FUNCTIONS	797	=head2 SUPPORT FUNCTIONS
624		798
…		…
637		811
638	Process all outstanding events on the result pipe. You have to call this	812	Process all outstanding events on the result pipe. You have to call this
639	regularly. Returns the number of events processed. Returns immediately	813	regularly. Returns the number of events processed. Returns immediately
640	when no events are outstanding.	814	when no events are outstanding.
641		815
		816	If not all requests were processed for whatever reason, the filehandle
		817	will still be ready when C<poll_cb> returns.
		818
642	Example: Install an Event watcher that automatically calls	819	Example: Install an Event watcher that automatically calls
643	IO::AIO::poll_cb with high priority:	820	IO::AIO::poll_cb with high priority:
644		821
645	Event->io (fd => IO::AIO::poll_fileno,	822	Event->io (fd => IO::AIO::poll_fileno,
646	poll => 'r', async => 1,	823	poll => 'r', async => 1,
647	cb => \&IO::AIO::poll_cb);	824	cb => \&IO::AIO::poll_cb);
648		825
		826	=item IO::AIO::poll_some $max_requests
		827
		828	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests
		829	at a time.
		830
		831	Useful if you want to ensure some level of interactiveness when perl is
		832	not fast enough to process all requests in time.
		833
		834	Example: Install an Event watcher that automatically calls
		835	IO::AIO::poll_some with low priority, to ensure that other parts of the
		836	program get the CPU sometimes even under high AIO load.
		837
		838	Event->io (fd => IO::AIO::poll_fileno,
		839	poll => 'r', nice => 1,
		840	cb => sub { IO::AIO::poll_some 256 });
		841
649	=item IO::AIO::poll_wait	842	=item IO::AIO::poll_wait
650		843
651	Wait till the result filehandle becomes ready for reading (simply does a	844	Wait till the result filehandle becomes ready for reading (simply does a
652	C<select> on the filehandle. This is useful if you want to synchronously wait	845	C<select> on the filehandle. This is useful if you want to synchronously wait
653	for some requests to finish).	846	for some requests to finish).
654		847
655	See C<nreqs> for an example.	848	See C<nreqs> for an example.
656		849
657	=item IO::AIO::nreqs	850	=item IO::AIO::nreqs
658		851
659	Returns the number of requests currently outstanding (i.e. for which their	852	Returns the number of requests currently in the ready, execute or pending
660	callback has not been invoked yet).	853	states (i.e. for which their callback has not been invoked yet).
661		854
662	Example: wait till there are no outstanding requests anymore:	855	Example: wait till there are no outstanding requests anymore:
663		856
664	IO::AIO::poll_wait, IO::AIO::poll_cb	857	IO::AIO::poll_wait, IO::AIO::poll_cb
665	while IO::AIO::nreqs;	858	while IO::AIO::nreqs;
666		859
		860	=item IO::AIO::nready
		861
		862	Returns the number of requests currently in the ready state (not yet
		863	executed).
		864
		865	=item IO::AIO::npending
		866
		867	Returns the number of requests currently in the pending state (executed,
		868	but not yet processed by poll_cb).
		869
667	=item IO::AIO::flush	870	=item IO::AIO::flush
668		871
669	Wait till all outstanding AIO requests have been handled.	872	Wait till all outstanding AIO requests have been handled.
670		873
671	Strictly equivalent to:	874	Strictly equivalent to:
…		…
682	IO::AIO::poll_wait, IO::AIO::poll_cb	885	IO::AIO::poll_wait, IO::AIO::poll_cb
683	if IO::AIO::nreqs;	886	if IO::AIO::nreqs;
684		887
685	=item IO::AIO::min_parallel $nthreads	888	=item IO::AIO::min_parallel $nthreads
686		889
687	Set the minimum number of AIO threads to C<$nthreads>. The current default	890	Set the minimum number of AIO threads to C<$nthreads>. The current
688	is C<4>, which means four asynchronous operations can be done at one time	891	default is C<8>, which means eight asynchronous operations can execute
689	(the number of outstanding operations, however, is unlimited).	892	concurrently at any one time (the number of outstanding requests,
		893	however, is unlimited).
690		894
691	IO::AIO starts threads only on demand, when an AIO request is queued and	895	IO::AIO starts threads only on demand, when an AIO request is queued and
692	no free thread exists.	896	no free thread exists.
693		897
694	It is recommended to keep the number of threads low, as some Linux	898	It is recommended to keep the number of threads relatively low, as some
695	kernel versions will scale negatively with the number of threads (higher	899	Linux kernel versions will scale negatively with the number of threads
696	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	900	(higher parallelity => MUCH higher latency). With current Linux 2.6
697	threads should be fine.	901	versions, 4-32 threads should be fine.
698		902
699	Under most circumstances you don't need to call this function, as the	903	Under most circumstances you don't need to call this function, as the
700	module selects a default that is suitable for low to moderate load.	904	module selects a default that is suitable for low to moderate load.
701		905
702	=item IO::AIO::max_parallel $nthreads	906	=item IO::AIO::max_parallel $nthreads
…		…
711	This module automatically runs C<max_parallel 0> at program end, to ensure	915	This module automatically runs C<max_parallel 0> at program end, to ensure
712	that all threads are killed and that there are no outstanding requests.	916	that all threads are killed and that there are no outstanding requests.
713		917
714	Under normal circumstances you don't need to call this function.	918	Under normal circumstances you don't need to call this function.
715		919
716	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	920	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		921
		922	This is a very bad function to use in interactive programs because it
		923	blocks, and a bad way to reduce concurrency because it is inexact: Better
		924	use an C<aio_group> together with a feed callback.
717		925
718	Sets the maximum number of outstanding requests to C<$nreqs>. If you	926	Sets the maximum number of outstanding requests to C<$nreqs>. If you
719	try to queue up more than this number of requests, the caller will block until	927	to queue up more than this number of requests, the next call to the
720	some requests have been handled.	928	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		929	function will block until the limit is no longer exceeded.
721		930
722	The default is very large, so normally there is no practical limit. If you	931	The default value is very large, so there is no practical limit on the
723	queue up many requests in a loop it often improves speed if you set	932	number of outstanding requests.
724	this to a relatively low number, such as C<100>.
725		933
726	Under normal circumstances you don't need to call this function.	934	You can still queue as many requests as you want. Therefore,
		935	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		936	as a stop gap to shield against fatal memory overflow (with large values).
727		937
728	=back	938	=back
729		939
730	=cut	940	=cut
731		941
…		…
743	or return undef;	953	or return undef;
744		954
745	*$sym	955	*$sym
746	}	956	}
747		957
748	min_parallel 4;	958	min_parallel 8;
749		959
750	END {	960	END {
751	max_parallel 0;	961	max_parallel 0;
752	}	962	}
753		963
…		…
758	This module should do "the right thing" when the process using it forks:	968	This module should do "the right thing" when the process using it forks:
759		969
760	Before the fork, IO::AIO enters a quiescent state where no requests	970	Before the fork, IO::AIO enters a quiescent state where no requests
761	can be added in other threads and no results will be processed. After	971	can be added in other threads and no results will be processed. After
762	the fork the parent simply leaves the quiescent state and continues	972	the fork the parent simply leaves the quiescent state and continues
763	request/result processing, while the child clears the request/result	973	request/result processing, while the child frees the request/result queue
764	queue (so the requests started before the fork will only be handled in	974	(so that the requests started before the fork will only be handled in the
765	the parent). Threads will be started on demand until the limit ste in the	975	parent). Threads will be started on demand until the limit set in the
766	parent process has been reached again.	976	parent process has been reached again.
767		977
768	In short: the parent will, after a short pause, continue as if fork had	978	In short: the parent will, after a short pause, continue as if fork had
769	not been called, while the child will act as if IO::AIO has not been used	979	not been called, while the child will act as if IO::AIO has not been used
770	yet.	980	yet.
771		981
		982	=head2 MEMORY USAGE
		983
		984	Per-request usage:
		985
		986	Each aio request uses - depending on your architecture - around 100-200
		987	bytes of memory. In addition, stat requests need a stat buffer (possibly
		988	a few hundred bytes), readdir requires a result buffer and so on. Perl
		989	scalars and other data passed into aio requests will also be locked and
		990	will consume memory till the request has entered the done state.
		991
		992	This is now awfully much, so queuing lots of requests is not usually a
		993	problem.
		994
		995	Per-thread usage:
		996
		997	In the execution phase, some aio requests require more memory for
		998	temporary buffers, and each thread requires a stack and other data
		999	structures (usually around 16k-128k, depending on the OS).
		1000
		1001	=head1 KNOWN BUGS
		1002
		1003	Known bugs will be fixed in the next release.
		1004
772	=head1 SEE ALSO	1005	=head1 SEE ALSO
773		1006
774	L<Coro>, L<Linux::AIO> (obsolete).	1007	L<Coro::AIO>.
775		1008
776	=head1 AUTHOR	1009	=head1 AUTHOR
777		1010
778	Marc Lehmann <schmorp@schmorp.de>	1011	Marc Lehmann <schmorp@schmorp.de>
779	http://home.schmorp.de/	1012	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.56 by root, Sun Oct 22 00:53:47 2006 UTC vs. Revision 1.80 by root, Thu Oct 26 16:28:33 2006 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.56 by root, Sun Oct 22 00:53:47 2006 UTC vs.
Revision 1.80 by root, Thu Oct 26 16:28:33 2006 UTC