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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.60 by root, Sun Oct 22 13:33:28 2006 UTC vs.
Revision 1.81 by root, Fri Oct 27 19:17:23 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.
…		…
182	print "read $_[0] bytes: <$buffer>\n";	267	print "read $_[0] bytes: <$buffer>\n";
183	};	268	};
184		269
185	=item aio_move $srcpath, $dstpath, $callback->($status)	270	=item aio_move $srcpath, $dstpath, $callback->($status)
186		271
187	[EXPERIMENTAL due to internal aio_group use]
188
189	Try to move the I<file> (directories not supported as either source or	272	Try to move the I<file> (directories not supported as either source or
190	destination) from C<$srcpath> to C<$dstpath> and call the callback with	273	destination) from C<$srcpath> to C<$dstpath> and call the callback with
191	the C<0> (error) or C<-1> ok.	274	the C<0> (error) or C<-1> ok.
192		275
193	This is a composite request that tries to rename(2) the file first. If	276	This is a composite request that tries to rename(2) the file first. If
…		…
203	=cut	286	=cut
204		287
205	sub aio_move($$$) {	288	sub aio_move($$$) {
206	my ($src, $dst, $cb) = @_;	289	my ($src, $dst, $cb) = @_;
207		290
		291	my $pri = aioreq_pri;
208	my $grp = aio_group $cb;	292	my $grp = aio_group $cb;
209		293
		294	aioreq_pri $pri;
210	add $grp aio_rename $src, $dst, sub {	295	add $grp aio_rename $src, $dst, sub {
211	if ($_[0] && $! == EXDEV) {	296	if ($_[0] && $! == EXDEV) {
		297	aioreq_pri $pri;
212	add $grp aio_open $src, O_RDONLY, 0, sub {	298	add $grp aio_open $src, O_RDONLY, 0, sub {
213	if (my $src_fh = $_[0]) {	299	if (my $src_fh = $_[0]) {
214	my @stat = stat $src_fh;	300	my @stat = stat $src_fh;
215		301
		302	aioreq_pri $pri;
216	add $grp aio_open $dst, O_WRONLY, 0200, sub {	303	add $grp aio_open $dst, O_WRONLY, 0200, sub {
217	if (my $dst_fh = $_[0]) {	304	if (my $dst_fh = $_[0]) {
		305	aioreq_pri $pri;
218	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 {
219	close $src_fh;	307	close $src_fh;
220		308
221	if ($_[0] == $stat[7]) {	309	if ($_[0] == $stat[7]) {
222	utime $stat[8], $stat[9], $dst;	310	utime $stat[8], $stat[9], $dst;
223	chmod $stat[2] & 07777, $dst_fh;	311	chmod $stat[2] & 07777, $dst_fh;
224	chown $stat[4], $stat[5], $dst_fh;	312	chown $stat[4], $stat[5], $dst_fh;
225	close $dst_fh;	313	close $dst_fh;
226		314
		315	aioreq_pri $pri;
227	add $grp aio_unlink $src, sub {	316	add $grp aio_unlink $src, sub {
228	$grp->result ($_[0]);	317	$grp->result ($_[0]);
229	};	318	};
230	} else {	319	} else {
231	my $errno = $!;	320	my $errno = $!;
		321	aioreq_pri $pri;
232	add $grp aio_unlink $dst, sub {	322	add $grp aio_unlink $dst, sub {
233	$! = $errno;	323	$! = $errno;
234	$grp->result (-1);	324	$grp->result (-1);
235	};	325	};
236	}	326	}
…		…
345	The callback a single argument which is either C<undef> or an array-ref	435	The callback a single argument which is either C<undef> or an array-ref
346	with the filenames.	436	with the filenames.
347		437
348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	438	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
349		439
350	[EXPERIMENTAL due to internal aio_group use]
351
352	Scans a directory (similar to C<aio_readdir>) but additionally tries to	440	Scans a directory (similar to C<aio_readdir>) but additionally tries to
353	separate the entries of directory C<$path> into two sets of names, ones	441	efficiently separate the entries of directory C<$path> into two sets of
354	you can recurse into (directories or links to them), and ones you cannot	442	names, directories you can recurse into (directories), and ones you cannot
355	recurse into (everything else).	443	recurse into (everything else, including symlinks to directories).
356		444
357	C<aio_scandir> is a composite request that consists of many sub	445	C<aio_scandir> is a composite request that creates of many sub requests_
358	requests. C<$maxreq> specifies the maximum number of outstanding aio	446	C<$maxreq> specifies the maximum number of outstanding aio requests that
359	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
360	suitable default will be chosen (currently 8).	448	will be chosen (currently 4).
361		449
362	On error, the callback is called without arguments, otherwise it receives	450	On error, the callback is called without arguments, otherwise it receives
363	two array-refs with path-relative entry names.	451	two array-refs with path-relative entry names.
364		452
365	Example:	453	Example:
…		…
402	=cut	490	=cut
403		491
404	sub aio_scandir($$$) {	492	sub aio_scandir($$$) {
405	my ($path, $maxreq, $cb) = @_;	493	my ($path, $maxreq, $cb) = @_;
406		494
		495	my $pri = aioreq_pri;
		496
407	my $grp = aio_group $cb;	497	my $grp = aio_group $cb;
408		498
409	$maxreq = 8 if $maxreq <= 0;	499	$maxreq = 4 if $maxreq <= 0;
410		500
411	# stat once	501	# stat once
		502	aioreq_pri $pri;
412	add $grp aio_stat $path, sub {	503	add $grp aio_stat $path, sub {
413	return $grp->result () if $_[0];	504	return $grp->result () if $_[0];
414	my $now = time;	505	my $now = time;
415	my $hash1 = join ":", (stat _)[0,1,3,7,9];	506	my $hash1 = join ":", (stat _)[0,1,3,7,9];
416		507
417	# read the directory entries	508	# read the directory entries
		509	aioreq_pri $pri;
418	add $grp aio_readdir $path, sub {	510	add $grp aio_readdir $path, sub {
419	my $entries = shift	511	my $entries = shift
420	or return $grp->result ();	512	or return $grp->result ();
421		513
422	# stat the dir another time	514	# stat the dir another time
		515	aioreq_pri $pri;
423	add $grp aio_stat $path, sub {	516	add $grp aio_stat $path, sub {
424	my $hash2 = join ":", (stat _)[0,1,3,7,9];	517	my $hash2 = join ":", (stat _)[0,1,3,7,9];
425		518
426	my $ndirs;	519	my $ndirs;
427		520
…		…
442	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	535	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
443	@$entries];	536	@$entries];
444		537
445	my (@dirs, @nondirs);	538	my (@dirs, @nondirs);
446		539
447	my ($statcb, $schedcb);
448	my $nreq = 0;
449
450	my $statgrp = add $grp aio_group;	540	my $statgrp = add $grp aio_group sub {
		541	$grp->result (\@dirs, \@nondirs);
		542	};
451		543
452	$schedcb = sub {	544	limit $statgrp $maxreq;
453	if (@$entries) {	545	feed $statgrp sub {
454	if ($nreq < $maxreq) {	546	return unless @$entries;
455	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	}
456	$nreq++;	567	}
457	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
458	}	568	}
459	} elsif (!$nreq) {
460	# finished
461	$statgrp->cancel;
462	undef $statcb;
463	undef $schedcb;
464	$grp->result (\@dirs, \@nondirs);
465	}	569	};
466	};	570	};
467	$statcb = sub {
468	my ($status, $entry) = @_;
469
470	if ($status < 0) {
471	$nreq--;
472	push @nondirs, $entry;
473	&$schedcb;
474	} else {
475	# need to check for real directory
476	add $grp aio_lstat "$path/$entry", sub {
477	$nreq--;
478
479	if (-d _) {
480	push @dirs, $entry;
481
482	if (!--$ndirs) {
483	push @nondirs, @$entries;
484	$entries = [];
485	}
486	} else {
487	push @nondirs, $entry;
488	}
489
490	&$schedcb;
491	}
492	}
493	};
494
495	&$schedcb while @$entries && $nreq < $maxreq;
496	};	571	};
497	};	572	};
498	};	573	};
499		574
500	$grp	575	$grp
…		…
513	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
514	detected, it will be emulated by calling C<fsync> instead.	589	detected, it will be emulated by calling C<fsync> instead.
515		590
516	=item aio_group $callback->(...)	591	=item aio_group $callback->(...)
517		592
518	[EXPERIMENTAL]
519
520	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
521	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
522	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.
523		597
524	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
525	for more info.	599	for more info.
526		600
527	Example:	601	Example:
…		…
533	add $grp	607	add $grp
534	(aio_stat ...),	608	(aio_stat ...),
535	(aio_stat ...),	609	(aio_stat ...),
536	...;	610	...;
537		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
538	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED	625	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
539		626
540	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
541	the request workers to sleep for the given time.	628	the request workers to sleep for the given time.
542		629
543	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
544	like sleep and file handle readable/writable, the overhead this creates	631	like sleep and file handle readable/writable, the overhead this creates is
545	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
546	under artificial I/O pressure.	633	except to put your application under artificial I/O pressure.
547		634
548	=back	635	=back
549		636
550	=head2 IO::AIO::REQ CLASS	637	=head2 IO::AIO::REQ CLASS
551		638
552	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
553	called in non-void context.	640	called in non-void context.
554		641
555	A request always moves through the following five states in its lifetime,
556	in order: B<ready> (request has been created, but has not been executed
557	yet), B<execute> (request is currently being executed), B<pending>
558	(request has been executed but callback has not been called yet),
559	B<result> (results are being processed synchronously, includes calling the
560	callback) and B<done> (request has reached the end of its lifetime and
561	holds no resources anymore).
562
563	=over 4	642	=over 4
564		643
565	=item $req->cancel	644	=item cancel $req
566		645
567	Cancels the request, if possible. Has the effect of skipping execution	646	Cancels the request, if possible. Has the effect of skipping execution
568	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
569	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
570	untouched. That means that requests that currently execute will not be	649	untouched. That means that requests that currently execute will not be
571	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.
572		651
		652	=item cb $req $callback->(...)
		653
		654	Replace (or simply set) the callback registered to the request.
		655
573	=back	656	=back
574		657
575	=head2 IO::AIO::GRP CLASS	658	=head2 IO::AIO::GRP CLASS
576		659
577	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
…		…
603	};	686	};
604		687
605	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
606	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.
607		690
		691	=over 4
		692
608	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
609	C<IO::AIO::poll_cb>, just like any other request.	694	C<IO::AIO::poll_cb>, just like any other request.
610		695
611	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
612	only the request itself, but also all requests it contains.	697	only the request itself, but also all requests it contains.
613		698
614	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.
615		700
616	You must not add requests to a group from within the group callback (or	701	=item * You must not add requests to a group from within the group callback (or
617	any later time).	702	any later time).
		703
		704	=back
618		705
619	Their lifetime, simplified, looks like this: when they are empty, they	706	Their lifetime, simplified, looks like this: when they are empty, they
620	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
621	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
622	exist.	709	exist.
…		…
626	group. And only when all those requests have finished will the the group	713	group. And only when all those requests have finished will the the group
627	itself finish.	714	itself finish.
628		715
629	=over 4	716	=over 4
630		717
		718	=item add $grp ...
		719
631	=item $grp->add (...)	720	=item $grp->add (...)
632
633	=item add $grp ...
634		721
635	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can	722	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
636	be added, including other groups, as long as you do not create circular	723	be added, including other groups, as long as you do not create circular
637	dependencies.	724	dependencies.
638		725
639	Returns all its arguments.	726	Returns all its arguments.
640		727
		728	=item $grp->cancel_subs
		729
		730	Cancel all subrequests and clears any feeder, but not the group request
		731	itself. Useful when you queued a lot of events but got a result early.
		732
641	=item $grp->result (...)	733	=item $grp->result (...)
642		734
643	Set the result value(s) that will be passed to the group callback when all	735	Set the result value(s) that will be passed to the group callback when all
644	subrequests have finished. By default, no argument will be passed.	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.
645		739
646	=item $grp->set_feeder ($callback->($grp))	740	=item $grp->errno ([$errno])
647		741
648	[VERY EXPERIMENTAL]	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)
649		753
650	Sets a feeder/generator on this group: every group can have an attached	754	Sets a feeder/generator on this group: every group can have an attached
651	generator that generates requests if idle. The idea behind this is that,	755	generator that generates requests if idle. The idea behind this is that,
652	although you could just queue as many requests as you want in a group,	756	although you could just queue as many requests as you want in a group,
653	this might starve other requests for a potentially long time. For	757	this might starve other requests for a potentially long time. For
654	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	758	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
655	requests, delaying any later requests for a long time.	759	requests, delaying any later requests for a long time.
656		760
657	To avoid this, and allow incremental generation of requests, you can	761	To avoid this, and allow incremental generation of requests, you can
658	instead a group and set a feeder on it that generates those requests. The	762	instead a group and set a feeder on it that generates those requests. The
659	feeder will be called whenever there are few enough (see C<feeder_limit>,	763	feed callback will be called whenever there are few enough (see C<limit>,
660	below) requests active in the group itself and is expected to queue more	764	below) requests active in the group itself and is expected to queue more
661	requests.	765	requests.
662		766
663	The feeder can queue as many requests as it likes (i.e. C<add> does not	767	The feed callback can queue as many requests as it likes (i.e. C<add> does
664	impose any limits).	768	not impose any limits).
665		769
666	If the feeder does not queue more requests when called, it will be	770	If the feed does not queue more requests when called, it will be
667	automatically removed from the group.	771	automatically removed from the group.
668		772
669	If the feeder limit is C<0>, it will be set to C<2> automatically.	773	If the feed limit is C<0>, it will be set to C<2> automatically.
670		774
671	Example:	775	Example:
672		776
673	# stat all files in @files, but only ever use four aio requests concurrently:	777	# stat all files in @files, but only ever use four aio requests concurrently:
674		778
675	my $grp = aio_group sub { print "finished\n" };	779	my $grp = aio_group sub { print "finished\n" };
676	$grp->feeder_limit (4);	780	limit $grp 4;
677	$grp->set_feeder (sub {	781	feed $grp sub {
678	my $file = pop @files	782	my $file = pop @files
679	or return;	783	or return;
680		784
681	add $grp aio_stat $file, sub { ... };	785	add $grp aio_stat $file, sub { ... };
682	});	786	};
683		787
684	=item $grp->feeder_limit ($num)	788	=item limit $grp $num
685		789
686	Sets the feeder limit for the group: The feeder will be called whenever	790	Sets the feeder limit for the group: The feeder will be called whenever
687	the group contains less than this many requests.	791	the group contains less than this many requests.
688		792
689	Setting the limit to C<0> will pause the feeding process.	793	Setting the limit to C<0> will pause the feeding process.
…		…
707		811
708	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
709	regularly. Returns the number of events processed. Returns immediately	813	regularly. Returns the number of events processed. Returns immediately
710	when no events are outstanding.	814	when no events are outstanding.
711		815
		816	If not all requests were processed for whatever reason, the filehandle
		817	will still be ready when C<poll_cb> returns.
		818
712	Example: Install an Event watcher that automatically calls	819	Example: Install an Event watcher that automatically calls
713	IO::AIO::poll_cb with high priority:	820	IO::AIO::poll_cb with high priority:
714		821
715	Event->io (fd => IO::AIO::poll_fileno,	822	Event->io (fd => IO::AIO::poll_fileno,
716	poll => 'r', async => 1,	823	poll => 'r', async => 1,
717	cb => \&IO::AIO::poll_cb);	824	cb => \&IO::AIO::poll_cb);
718		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
719	=item IO::AIO::poll_wait	842	=item IO::AIO::poll_wait
720		843
721	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
722	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
723	for some requests to finish).	846	for some requests to finish).
724		847
725	See C<nreqs> for an example.	848	See C<nreqs> for an example.
726		849
727	=item IO::AIO::nreqs	850	=item IO::AIO::nreqs
728		851
729	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
730	callback has not been invoked yet).	853	states (i.e. for which their callback has not been invoked yet).
731		854
732	Example: wait till there are no outstanding requests anymore:	855	Example: wait till there are no outstanding requests anymore:
733		856
734	IO::AIO::poll_wait, IO::AIO::poll_cb	857	IO::AIO::poll_wait, IO::AIO::poll_cb
735	while IO::AIO::nreqs;	858	while IO::AIO::nreqs;
736		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
737	=item IO::AIO::flush	870	=item IO::AIO::flush
738		871
739	Wait till all outstanding AIO requests have been handled.	872	Wait till all outstanding AIO requests have been handled.
740		873
741	Strictly equivalent to:	874	Strictly equivalent to:
…		…
752	IO::AIO::poll_wait, IO::AIO::poll_cb	885	IO::AIO::poll_wait, IO::AIO::poll_cb
753	if IO::AIO::nreqs;	886	if IO::AIO::nreqs;
754		887
755	=item IO::AIO::min_parallel $nthreads	888	=item IO::AIO::min_parallel $nthreads
756		889
757	Set the minimum number of AIO threads to C<$nthreads>. The current default	890	Set the minimum number of AIO threads to C<$nthreads>. The current
758	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
759	(the number of outstanding operations, however, is unlimited).	892	concurrently at any one time (the number of outstanding requests,
		893	however, is unlimited).
760		894
761	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
762	no free thread exists.	896	no free thread exists.
763		897
764	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
765	kernel versions will scale negatively with the number of threads (higher	899	Linux kernel versions will scale negatively with the number of threads
766	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	900	(higher parallelity => MUCH higher latency). With current Linux 2.6
767	threads should be fine.	901	versions, 4-32 threads should be fine.
768		902
769	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
770	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.
771		905
772	=item IO::AIO::max_parallel $nthreads	906	=item IO::AIO::max_parallel $nthreads
…		…
781	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
782	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.
783		917
784	Under normal circumstances you don't need to call this function.	918	Under normal circumstances you don't need to call this function.
785		919
786	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	920	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		921
		922	This is a very bad function to use in interactive programs because it
		923	blocks, and a bad way to reduce concurrency because it is inexact: Better
		924	use an C<aio_group> together with a feed callback.
787		925
788	Sets the maximum number of outstanding requests to C<$nreqs>. If you	926	Sets the maximum number of outstanding requests to C<$nreqs>. If you
789	try to queue up more than this number of requests, the caller will block until	927	to queue up more than this number of requests, the next call to the
790	some requests have been handled.	928	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		929	function will block until the limit is no longer exceeded.
791		930
792	The default is very large, so normally there is no practical limit. If you	931	The default value is very large, so there is no practical limit on the
793	queue up many requests in a loop it often improves speed if you set	932	number of outstanding requests.
794	this to a relatively low number, such as C<100>.
795		933
796	Under normal circumstances you don't need to call this function.	934	You can still queue as many requests as you want. Therefore,
		935	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		936	as a stop gap to shield against fatal memory overflow (with large values).
797		937
798	=back	938	=back
799		939
800	=cut	940	=cut
801		941
…		…
813	or return undef;	953	or return undef;
814		954
815	*$sym	955	*$sym
816	}	956	}
817		957
818	min_parallel 4;	958	min_parallel 8;
819
820	END {
821	max_parallel 0;
822	}
823		959
824	1;	960	1;
825		961
826	=head2 FORK BEHAVIOUR	962	=head2 FORK BEHAVIOUR
827		963
828	This module should do "the right thing" when the process using it forks:	964	This module should do "the right thing" when the process using it forks:
829		965
830	Before the fork, IO::AIO enters a quiescent state where no requests	966	Before the fork, IO::AIO enters a quiescent state where no requests
831	can be added in other threads and no results will be processed. After	967	can be added in other threads and no results will be processed. After
832	the fork the parent simply leaves the quiescent state and continues	968	the fork the parent simply leaves the quiescent state and continues
833	request/result processing, while the child clears the request/result	969	request/result processing, while the child frees the request/result queue
834	queue (so the requests started before the fork will only be handled in	970	(so that the requests started before the fork will only be handled in the
835	the parent). Threads will be started on demand until the limit ste in the	971	parent). Threads will be started on demand until the limit set in the
836	parent process has been reached again.	972	parent process has been reached again.
837		973
838	In short: the parent will, after a short pause, continue as if fork had	974	In short: the parent will, after a short pause, continue as if fork had
839	not been called, while the child will act as if IO::AIO has not been used	975	not been called, while the child will act as if IO::AIO has not been used
840	yet.	976	yet.
841		977
842	=head2 MEMORY USAGE	978	=head2 MEMORY USAGE
843		979
		980	Per-request usage:
		981
844	Each aio request uses - depending on your architecture - around 128 bytes	982	Each aio request uses - depending on your architecture - around 100-200
845	of memory. In addition, stat requests need a stat buffer (possibly a few	983	bytes of memory. In addition, stat requests need a stat buffer (possibly
846	hundred bytes). Perl scalars and other data passed into aio requests will	984	a few hundred bytes), readdir requires a result buffer and so on. Perl
847	also be locked.	985	scalars and other data passed into aio requests will also be locked and
		986	will consume memory till the request has entered the done state.
848		987
849	This is now awfully much, so queuing lots of requests is not usually a	988	This is now awfully much, so queuing lots of requests is not usually a
850	problem.	989	problem.
851		990
852	Each thread needs a stack area which is usually around 16k, sometimes much	991	Per-thread usage:
853	larger, depending on the OS.	992
		993	In the execution phase, some aio requests require more memory for
		994	temporary buffers, and each thread requires a stack and other data
		995	structures (usually around 16k-128k, depending on the OS).
		996
		997	=head1 KNOWN BUGS
		998
		999	Known bugs will be fixed in the next release.
854		1000
855	=head1 SEE ALSO	1001	=head1 SEE ALSO
856		1002
857	L<Coro>, L<Linux::AIO> (obsolete).	1003	L<Coro::AIO>.
858		1004
859	=head1 AUTHOR	1005	=head1 AUTHOR
860		1006
861	Marc Lehmann <schmorp@schmorp.de>	1007	Marc Lehmann <schmorp@schmorp.de>
862	http://home.schmorp.de/	1008	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.60 by root, Sun Oct 22 13:33:28 2006 UTC vs. Revision 1.81 by root, Fri Oct 27 19:17:23 2006 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.60 by root, Sun Oct 22 13:33:28 2006 UTC vs.
Revision 1.81 by root, Fri Oct 27 19:17:23 2006 UTC