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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.70 by root, Tue Oct 24 03:40:38 2006 UTC vs.
Revision 1.86 by root, Sat Oct 28 23:32:29 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	Asynchronous means that operations that can normally block your program
		57	(e.g. reading from disk) will be done asynchronously: the operation
		58	will still block, but you can do something else in the meantime. This
		59	is extremely useful for programs that need to stay interactive even
		60	when doing heavy I/O (GUI programs, high performance network servers
		61	etc.), but can also be used to easily do operations in parallel that are
		62	normally done sequentially, e.g. stat'ing many files, which is much faster
		63	on a RAID volume or over NFS when you do a number of stat operations
		64	concurrently.
		65
		66	While this works on all types of file descriptors (for example sockets),
		67	using these functions on file descriptors that support nonblocking
		68	operation (again, sockets, pipes etc.) is very inefficient. Use an event
		69	loop for that (such as the L<Event\|Event> module): IO::AIO will naturally
		70	fit into such an event loop itself.
		71
56	Currently, a number of threads are started that execute your read/writes	72	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	73	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	74	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	75	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	76	functions available on many operating systems. However, they are often
61	(Linux doesn't allow them on normal files currently, for example),	77	not well-supported or restricted (GNU/Linux doesn't allow them on normal
62	and they would only support aio_read and aio_write, so the remaining	78	files currently, for example), and they would only support aio_read and
63	functionality would have to be implemented using threads anyway.	79	aio_write, so the remaining functionality would have to be implemented
		80	using threads anyway.
64		81
65	Although the module will work with in the presence of other threads,	82	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	83	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	84	locking yourself, always call C<poll_cb> from within the same thread, or
68	call C<poll_cb> (or other C<aio_> functions) recursively.	85	never call C<poll_cb> (or other C<aio_> functions) recursively.
		86
		87	=head2 EXAMPLE
		88
		89	This is a simple example that uses the Event module and loads
		90	F</etc/passwd> asynchronously:
		91
		92	use Fcntl;
		93	use Event;
		94	use IO::AIO;
		95
		96	# register the IO::AIO callback with Event
		97	Event->io (fd => IO::AIO::poll_fileno,
		98	poll => 'r',
		99	cb => \&IO::AIO::poll_cb);
		100
		101	# queue the request to open /etc/passwd
		102	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		103	my $fh = $_[0]
		104	or die "error while opening: $!";
		105
		106	# stat'ing filehandles is generally non-blocking
		107	my $size = -s $fh;
		108
		109	# queue a request to read the file
		110	my $contents;
		111	aio_read $fh, 0, $size, $contents, 0, sub {
		112	$_[0] == $size
		113	or die "short read: $!";
		114
		115	close $fh;
		116
		117	# file contents now in $contents
		118	print $contents;
		119
		120	# exit event loop and program
		121	Event::unloop;
		122	};
		123	};
		124
		125	# possibly queue up other requests, or open GUI windows,
		126	# check for sockets etc. etc.
		127
		128	# process events as long as there are some:
		129	Event::loop;
		130
		131	=head1 REQUEST ANATOMY AND LIFETIME
		132
		133	Every C<aio_*> function creates a request. which is a C data structure not
		134	directly visible to Perl.
		135
		136	If called in non-void context, every request function returns a Perl
		137	object representing the request. In void context, nothing is returned,
		138	which saves a bit of memory.
		139
		140	The perl object is a fairly standard ref-to-hash object. The hash contents
		141	are not used by IO::AIO so you are free to store anything you like in it.
		142
		143	During their existance, aio requests travel through the following states,
		144	in order:
		145
		146	=over 4
		147
		148	=item ready
		149
		150	Immediately after a request is created it is put into the ready state,
		151	waiting for a thread to execute it.
		152
		153	=item execute
		154
		155	A thread has accepted the request for processing and is currently
		156	executing it (e.g. blocking in read).
		157
		158	=item pending
		159
		160	The request has been executed and is waiting for result processing.
		161
		162	While request submission and execution is fully asynchronous, result
		163	processing is not and relies on the perl interpreter calling C<poll_cb>
		164	(or another function with the same effect).
		165
		166	=item result
		167
		168	The request results are processed synchronously by C<poll_cb>.
		169
		170	The C<poll_cb> function will process all outstanding aio requests by
		171	calling their callbacks, freeing memory associated with them and managing
		172	any groups they are contained in.
		173
		174	=item done
		175
		176	Request has reached the end of its lifetime and holds no resources anymore
		177	(except possibly for the Perl object, but its connection to the actual
		178	aio request is severed and calling its methods will either do nothing or
		179	result in a runtime error).
69		180
70	=cut	181	=cut
71		182
72	package IO::AIO;	183	package IO::AIO;
73		184
…		…
75	use strict 'vars';	186	use strict 'vars';
76		187
77	use base 'Exporter';	188	use base 'Exporter';
78		189
79	BEGIN {	190	BEGIN {
80	our $VERSION = '2.0';	191	our $VERSION = '2.1';
81		192
82	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	193	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	194	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	195	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
85	aio_group aio_nop);	196	aio_copy aio_group aio_nop aio_mknod);
86	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	197	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
87	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	198	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
88	min_parallel max_parallel max_outstanding nreqs);	199	min_parallel max_parallel max_idle
		200	nreqs nready npending nthreads
		201	max_poll_time max_poll_reqs);
89		202
90	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	203	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
91		204
92	require XSLoader;	205	require XSLoader;
93	XSLoader::load ("IO::AIO", $VERSION);	206	XSLoader::load ("IO::AIO", $VERSION);
…		…
124	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	237	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
125	use something else.	238	use something else.
126		239
127	=over 4	240	=over 4
128		241
129	=item aioreq_pri $pri	242	=item $prev_pri = aioreq_pri [$pri]
130		243
131	Sets the priority for the next aio request. The default priority	244	Returns the priority value that would be used for the next request and, if
		245	C<$pri> is given, sets the priority for the next aio request.
		246
132	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,	247	The default priority is C<0>, the minimum and maximum priorities are C<-4>
133	respectively. Requests with higher priority will be serviced first.	248	and C<4>, respectively. Requests with higher priority will be serviced
		249	first.
134		250
135	The priority will be reset to C<0> after each call to one of the C<aio_>	251	The priority will be reset to C<0> after each call to one of the C<aio_*>
136	functions.	252	functions.
137		253
138	Example: open a file with low priority, then read something from it with	254	Example: open a file with low priority, then read something from it with
139	higher priority so the read request is serviced before other low priority	255	higher priority so the read request is serviced before other low priority
140	open requests (potentially spamming the cache):	256	open requests (potentially spamming the cache):
…		…
210		326
211	aio_read $fh, 7, 15, $buffer, 0, sub {	327	aio_read $fh, 7, 15, $buffer, 0, sub {
212	$_[0] > 0 or die "read error: $!";	328	$_[0] > 0 or die "read error: $!";
213	print "read $_[0] bytes: <$buffer>\n";	329	print "read $_[0] bytes: <$buffer>\n";
214	};	330	};
215
216	=item aio_move $srcpath, $dstpath, $callback->($status)
217
218	[EXPERIMENTAL due to internal aio_group use]
219
220	Try to move the I<file> (directories not supported as either source or
221	destination) from C<$srcpath> to C<$dstpath> and call the callback with
222	the C<0> (error) or C<-1> ok.
223
224	This is a composite request that tries to rename(2) the file first. If
225	rename files with C<EXDEV>, it creates the destination file with mode 0200
226	and copies the contents of the source file into it using C<aio_sendfile>,
227	followed by restoring atime, mtime, access mode and uid/gid, in that
228	order, and unlinking the C<$srcpath>.
229
230	If an error occurs, the partial destination file will be unlinked, if
231	possible, except when setting atime, mtime, access mode and uid/gid, where
232	errors are being ignored.
233
234	=cut
235
236	sub aio_move($$$) {
237	my ($src, $dst, $cb) = @_;
238
239	my $grp = aio_group $cb;
240
241	add $grp aio_rename $src, $dst, sub {
242	if ($_[0] && $! == EXDEV) {
243	add $grp aio_open $src, O_RDONLY, 0, sub {
244	if (my $src_fh = $_[0]) {
245	my @stat = stat $src_fh;
246
247	add $grp aio_open $dst, O_WRONLY, 0200, sub {
248	if (my $dst_fh = $_[0]) {
249	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
250	close $src_fh;
251
252	if ($_[0] == $stat[7]) {
253	utime $stat[8], $stat[9], $dst;
254	chmod $stat[2] & 07777, $dst_fh;
255	chown $stat[4], $stat[5], $dst_fh;
256	close $dst_fh;
257
258	add $grp aio_unlink $src, sub {
259	$grp->result ($_[0]);
260	};
261	} else {
262	my $errno = $!;
263	add $grp aio_unlink $dst, sub {
264	$! = $errno;
265	$grp->result (-1);
266	};
267	}
268	};
269	} else {
270	$grp->result (-1);
271	}
272	},
273
274	} else {
275	$grp->result (-1);
276	}
277	};
278	} else {
279	$grp->result ($_[0]);
280	}
281	};
282
283	$grp
284	}
285		331
286	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	332	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
287		333
288	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	334	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
289	reading at byte offset C<$in_offset>, and starts writing at the current	335	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
345	=item aio_unlink $pathname, $callback->($status)	391	=item aio_unlink $pathname, $callback->($status)
346		392
347	Asynchronously unlink (delete) a file and call the callback with the	393	Asynchronously unlink (delete) a file and call the callback with the
348	result code.	394	result code.
349		395
		396	=item aio_mknod $path, $mode, $dev, $callback->($status)
		397
		398	[EXPERIMENTAL]
		399
		400	Asynchronously create a device node (or fifo). See mknod(2).
		401
		402	The only (POSIX-) portable way of calling this function is:
		403
		404	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		405
350	=item aio_link $srcpath, $dstpath, $callback->($status)	406	=item aio_link $srcpath, $dstpath, $callback->($status)
351		407
352	Asynchronously create a new link to the existing object at C<$srcpath> at	408	Asynchronously create a new link to the existing object at C<$srcpath> at
353	the path C<$dstpath> and call the callback with the result code.	409	the path C<$dstpath> and call the callback with the result code.
354		410
…		…
374	sorted, and will B<NOT> include the C<.> and C<..> entries.	430	sorted, and will B<NOT> include the C<.> and C<..> entries.
375		431
376	The callback a single argument which is either C<undef> or an array-ref	432	The callback a single argument which is either C<undef> or an array-ref
377	with the filenames.	433	with the filenames.
378		434
		435	=item aio_copy $srcpath, $dstpath, $callback->($status)
		436
		437	Try to copy the I<file> (directories not supported as either source or
		438	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		439	the C<0> (error) or C<-1> ok.
		440
		441	This is a composite request that it creates the destination file with
		442	mode 0200 and copies the contents of the source file into it using
		443	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		444	uid/gid, in that order.
		445
		446	If an error occurs, the partial destination file will be unlinked, if
		447	possible, except when setting atime, mtime, access mode and uid/gid, where
		448	errors are being ignored.
		449
		450	=cut
		451
		452	sub aio_copy($$;$) {
		453	my ($src, $dst, $cb) = @_;
		454
		455	my $pri = aioreq_pri;
		456	my $grp = aio_group $cb;
		457
		458	aioreq_pri $pri;
		459	add $grp aio_open $src, O_RDONLY, 0, sub {
		460	if (my $src_fh = $_[0]) {
		461	my @stat = stat $src_fh;
		462
		463	aioreq_pri $pri;
		464	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		465	if (my $dst_fh = $_[0]) {
		466	aioreq_pri $pri;
		467	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		468	if ($_[0] == $stat[7]) {
		469	$grp->result (0);
		470	close $src_fh;
		471
		472	# those should not normally block. should. should.
		473	utime $stat[8], $stat[9], $dst;
		474	chmod $stat[2] & 07777, $dst_fh;
		475	chown $stat[4], $stat[5], $dst_fh;
		476	close $dst_fh;
		477	} else {
		478	$grp->result (-1);
		479	close $src_fh;
		480	close $dst_fh;
		481
		482	aioreq $pri;
		483	add $grp aio_unlink $dst;
		484	}
		485	};
		486	} else {
		487	$grp->result (-1);
		488	}
		489	},
		490
		491	} else {
		492	$grp->result (-1);
		493	}
		494	};
		495
		496	$grp
		497	}
		498
		499	=item aio_move $srcpath, $dstpath, $callback->($status)
		500
		501	Try to move the I<file> (directories not supported as either source or
		502	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		503	the C<0> (error) or C<-1> ok.
		504
		505	This is a composite request that tries to rename(2) the file first. If
		506	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		507	that is successful, unlinking the C<$srcpath>.
		508
		509	=cut
		510
		511	sub aio_move($$;$) {
		512	my ($src, $dst, $cb) = @_;
		513
		514	my $pri = aioreq_pri;
		515	my $grp = aio_group $cb;
		516
		517	aioreq_pri $pri;
		518	add $grp aio_rename $src, $dst, sub {
		519	if ($_[0] && $! == EXDEV) {
		520	aioreq_pri $pri;
		521	add $grp aio_copy $src, $dst, sub {
		522	$grp->result ($_[0]);
		523
		524	if (!$_[0]) {
		525	aioreq_pri $pri;
		526	add $grp aio_unlink $src;
		527	}
		528	};
		529	} else {
		530	$grp->result ($_[0]);
		531	}
		532	};
		533
		534	$grp
		535	}
		536
379	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	537	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
380		538
381	[EXPERIMENTAL due to internal aio_group use]
382
383	Scans a directory (similar to C<aio_readdir>) but additionally tries to	539	Scans a directory (similar to C<aio_readdir>) but additionally tries to
384	separate the entries of directory C<$path> into two sets of names, ones	540	efficiently separate the entries of directory C<$path> into two sets of
385	you can recurse into (directories or links to them), and ones you cannot	541	names, directories you can recurse into (directories), and ones you cannot
386	recurse into (everything else).	542	recurse into (everything else, including symlinks to directories).
387		543
388	C<aio_scandir> is a composite request that creates of many sub requests_	544	C<aio_scandir> is a composite request that creates of many sub requests_
389	C<$maxreq> specifies the maximum number of outstanding aio requests that	545	C<$maxreq> specifies the maximum number of outstanding aio requests that
390	this function generates. If it is C<< <= 0 >>, then a suitable default	546	this function generates. If it is C<< <= 0 >>, then a suitable default
391	will be chosen (currently 6).	547	will be chosen (currently 4).
392		548
393	On error, the callback is called without arguments, otherwise it receives	549	On error, the callback is called without arguments, otherwise it receives
394	two array-refs with path-relative entry names.	550	two array-refs with path-relative entry names.
395		551
396	Example:	552	Example:
…		…
433	=cut	589	=cut
434		590
435	sub aio_scandir($$$) {	591	sub aio_scandir($$$) {
436	my ($path, $maxreq, $cb) = @_;	592	my ($path, $maxreq, $cb) = @_;
437		593
		594	my $pri = aioreq_pri;
		595
438	my $grp = aio_group $cb;	596	my $grp = aio_group $cb;
439		597
440	$maxreq = 6 if $maxreq <= 0;	598	$maxreq = 4 if $maxreq <= 0;
441		599
442	# stat once	600	# stat once
		601	aioreq_pri $pri;
443	add $grp aio_stat $path, sub {	602	add $grp aio_stat $path, sub {
444	return $grp->result () if $_[0];	603	return $grp->result () if $_[0];
445	my $now = time;	604	my $now = time;
446	my $hash1 = join ":", (stat _)[0,1,3,7,9];	605	my $hash1 = join ":", (stat _)[0,1,3,7,9];
447		606
448	# read the directory entries	607	# read the directory entries
		608	aioreq_pri $pri;
449	add $grp aio_readdir $path, sub {	609	add $grp aio_readdir $path, sub {
450	my $entries = shift	610	my $entries = shift
451	or return $grp->result ();	611	or return $grp->result ();
452		612
453	# stat the dir another time	613	# stat the dir another time
		614	aioreq_pri $pri;
454	add $grp aio_stat $path, sub {	615	add $grp aio_stat $path, sub {
455	my $hash2 = join ":", (stat _)[0,1,3,7,9];	616	my $hash2 = join ":", (stat _)[0,1,3,7,9];
456		617
457	my $ndirs;	618	my $ndirs;
458		619
…		…
473	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	634	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
474	@$entries];	635	@$entries];
475		636
476	my (@dirs, @nondirs);	637	my (@dirs, @nondirs);
477		638
478	my ($statcb, $schedcb);
479	my $nreq = 0;
480
481	my $statgrp = add $grp aio_group;	639	my $statgrp = add $grp aio_group sub {
		640	$grp->result (\@dirs, \@nondirs);
		641	};
482		642
483	$schedcb = sub {	643	limit $statgrp $maxreq;
484	if (@$entries) {	644	feed $statgrp sub {
485	if ($nreq < $maxreq) {	645	return unless @$entries;
486	my $ent = pop @$entries;	646	my $entry = pop @$entries;
		647
		648	aioreq_pri $pri;
		649	add $statgrp aio_stat "$path/$entry/.", sub {
		650	if ($_[0] < 0) {
		651	push @nondirs, $entry;
		652	} else {
		653	# need to check for real directory
		654	aioreq_pri $pri;
		655	add $statgrp aio_lstat "$path/$entry", sub {
		656	if (-d _) {
		657	push @dirs, $entry;
		658
		659	unless (--$ndirs) {
		660	push @nondirs, @$entries;
		661	feed $statgrp;
		662	}
		663	} else {
		664	push @nondirs, $entry;
		665	}
487	$nreq++;	666	}
488	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
489	}	667	}
490	} elsif (!$nreq) {
491	# finished
492	$statgrp->cancel;
493	undef $statcb;
494	undef $schedcb;
495	$grp->result (\@dirs, \@nondirs);
496	}	668	};
497	};	669	};
498	$statcb = sub {
499	my ($status, $entry) = @_;
500
501	if ($status < 0) {
502	$nreq--;
503	push @nondirs, $entry;
504	&$schedcb;
505	} else {
506	# need to check for real directory
507	add $grp aio_lstat "$path/$entry", sub {
508	$nreq--;
509
510	if (-d _) {
511	push @dirs, $entry;
512
513	if (!--$ndirs) {
514	push @nondirs, @$entries;
515	$entries = [];
516	}
517	} else {
518	push @nondirs, $entry;
519	}
520
521	&$schedcb;
522	}
523	}
524	};
525
526	&$schedcb while @$entries && $nreq < $maxreq;
527	};	670	};
528	};	671	};
529	};	672	};
530		673
531	$grp	674	$grp
…		…
544	If this call isn't available because your OS lacks it or it couldn't be	687	If this call isn't available because your OS lacks it or it couldn't be
545	detected, it will be emulated by calling C<fsync> instead.	688	detected, it will be emulated by calling C<fsync> instead.
546		689
547	=item aio_group $callback->(...)	690	=item aio_group $callback->(...)
548		691
549	[EXPERIMENTAL]
550
551	This is a very special aio request: Instead of doing something, it is a	692	This is a very special aio request: Instead of doing something, it is a
552	container for other aio requests, which is useful if you want to bundle	693	container for other aio requests, which is useful if you want to bundle
553	many requests into a single, composite, request.	694	many requests into a single, composite, request with a definite callback
		695	and the ability to cancel the whole request with its subrequests.
554		696
555	Returns an object of class L<IO::AIO::GRP>. See its documentation below	697	Returns an object of class L<IO::AIO::GRP>. See its documentation below
556	for more info.	698	for more info.
557		699
558	Example:	700	Example:
…		…
577	phase and still requires a worker thread. Thus, the callback will not	719	phase and still requires a worker thread. Thus, the callback will not
578	be executed immediately but only after other requests in the queue have	720	be executed immediately but only after other requests in the queue have
579	entered their execution phase. This can be used to measure request	721	entered their execution phase. This can be used to measure request
580	latency.	722	latency.
581		723
582	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED	724	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
583		725
584	Mainly used for debugging and benchmarking, this aio request puts one of	726	Mainly used for debugging and benchmarking, this aio request puts one of
585	the request workers to sleep for the given time.	727	the request workers to sleep for the given time.
586		728
587	While it is theoretically handy to have simple I/O scheduling requests	729	While it is theoretically handy to have simple I/O scheduling requests
588	like sleep and file handle readable/writable, the overhead this creates	730	like sleep and file handle readable/writable, the overhead this creates is
589	is immense, so do not use this function except to put your application	731	immense (it blocks a thread for a long time) so do not use this function
590	under artificial I/O pressure.	732	except to put your application under artificial I/O pressure.
591		733
592	=back	734	=back
593		735
594	=head2 IO::AIO::REQ CLASS	736	=head2 IO::AIO::REQ CLASS
595		737
596	All non-aggregate C<aio_*> functions return an object of this class when	738	All non-aggregate C<aio_*> functions return an object of this class when
597	called in non-void context.	739	called in non-void context.
598
599	A request always moves through the following five states in its lifetime,
600	in order: B<ready> (request has been created, but has not been executed
601	yet), B<execute> (request is currently being executed), B<pending>
602	(request has been executed but callback has not been called yet),
603	B<result> (results are being processed synchronously, includes calling the
604	callback) and B<done> (request has reached the end of its lifetime and
605	holds no resources anymore).
606		740
607	=over 4	741	=over 4
608		742
609	=item cancel $req	743	=item cancel $req
610		744
…		…
664	=item * They can also can also be added to other IO::AIO::GRP objects.	798	=item * They can also can also be added to other IO::AIO::GRP objects.
665		799
666	=item * You must not add requests to a group from within the group callback (or	800	=item * You must not add requests to a group from within the group callback (or
667	any later time).	801	any later time).
668		802
669	=item * This does not harmonise well with C<max_outstanding>, so best do
670	not combine C<aio_group> with it. Groups and feeders are recommended for
671	this kind of concurrency-limiting.
672
673	=back	803	=back
674		804
675	Their lifetime, simplified, looks like this: when they are empty, they	805	Their lifetime, simplified, looks like this: when they are empty, they
676	will finish very quickly. If they contain only requests that are in the	806	will finish very quickly. If they contain only requests that are in the
677	C<done> state, they will also finish. Otherwise they will continue to	807	C<done> state, they will also finish. Otherwise they will continue to
…		…
692	be added, including other groups, as long as you do not create circular	822	be added, including other groups, as long as you do not create circular
693	dependencies.	823	dependencies.
694		824
695	Returns all its arguments.	825	Returns all its arguments.
696		826
		827	=item $grp->cancel_subs
		828
		829	Cancel all subrequests and clears any feeder, but not the group request
		830	itself. Useful when you queued a lot of events but got a result early.
		831
697	=item $grp->result (...)	832	=item $grp->result (...)
698		833
699	Set the result value(s) that will be passed to the group callback when all	834	Set the result value(s) that will be passed to the group callback when all
700	subrequests have finished. By default, no argument will be passed.	835	subrequests have finished and set thre groups errno to the current value
		836	of errno (just like calling C<errno> without an error number). By default,
		837	no argument will be passed and errno is zero.
		838
		839	=item $grp->errno ([$errno])
		840
		841	Sets the group errno value to C<$errno>, or the current value of errno
		842	when the argument is missing.
		843
		844	Every aio request has an associated errno value that is restored when
		845	the callback is invoked. This method lets you change this value from its
		846	default (0).
		847
		848	Calling C<result> will also set errno, so make sure you either set C<$!>
		849	before the call to C<result>, or call c<errno> after it.
701		850
702	=item feed $grp $callback->($grp)	851	=item feed $grp $callback->($grp)
703
704	[VERY EXPERIMENTAL]
705		852
706	Sets a feeder/generator on this group: every group can have an attached	853	Sets a feeder/generator on this group: every group can have an attached
707	generator that generates requests if idle. The idea behind this is that,	854	generator that generates requests if idle. The idea behind this is that,
708	although you could just queue as many requests as you want in a group,	855	although you could just queue as many requests as you want in a group,
709	this might starve other requests for a potentially long time. For	856	this might starve other requests for a potentially long time. For
…		…
746		893
747	=back	894	=back
748		895
749	=head2 SUPPORT FUNCTIONS	896	=head2 SUPPORT FUNCTIONS
750		897
		898	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		899
751	=over 4	900	=over 4
752		901
753	=item $fileno = IO::AIO::poll_fileno	902	=item $fileno = IO::AIO::poll_fileno
754		903
755	Return the I<request result pipe file descriptor>. This filehandle must be	904	Return the I<request result pipe file descriptor>. This filehandle must be
…		…
759		908
760	See C<poll_cb> for an example.	909	See C<poll_cb> for an example.
761		910
762	=item IO::AIO::poll_cb	911	=item IO::AIO::poll_cb
763		912
764	Process all outstanding events on the result pipe. You have to call this	913	Process some outstanding events on the result pipe. You have to call this
765	regularly. Returns the number of events processed. Returns immediately	914	regularly. Returns the number of events processed. Returns immediately
766	when no events are outstanding.	915	when no events are outstanding. The amount of events processed depends on
		916	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		917
		918	If not all requests were processed for whatever reason, the filehandle
		919	will still be ready when C<poll_cb> returns.
767		920
768	Example: Install an Event watcher that automatically calls	921	Example: Install an Event watcher that automatically calls
769	IO::AIO::poll_cb with high priority:	922	IO::AIO::poll_cb with high priority:
770		923
771	Event->io (fd => IO::AIO::poll_fileno,	924	Event->io (fd => IO::AIO::poll_fileno,
772	poll => 'r', async => 1,	925	poll => 'r', async => 1,
773	cb => \&IO::AIO::poll_cb);	926	cb => \&IO::AIO::poll_cb);
774		927
		928	=item IO::AIO::max_poll_reqs $nreqs
		929
		930	=item IO::AIO::max_poll_time $seconds
		931
		932	These set the maximum number of requests (default C<0>, meaning infinity)
		933	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		934	the maximum amount of time (default C<0>, meaning infinity) spent in
		935	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		936	of time C<poll_cb> is allowed to use).
		937
		938	Setting these is useful if you want to ensure some level of
		939	interactiveness when perl is not fast enough to process all requests in
		940	time.
		941
		942	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		943
		944	Example: Install an Event watcher that automatically calls
		945	IO::AIO::poll_some with low priority, to ensure that other parts of the
		946	program get the CPU sometimes even under high AIO load.
		947
		948	# try not to spend much more than 0.1s in poll_cb
		949	IO::AIO::max_poll_time 0.1;
		950
		951	# use a low priority so other tasks have priority
		952	Event->io (fd => IO::AIO::poll_fileno,
		953	poll => 'r', nice => 1,
		954	cb => &IO::AIO::poll_cb);
		955
775	=item IO::AIO::poll_wait	956	=item IO::AIO::poll_wait
776		957
777	Wait till the result filehandle becomes ready for reading (simply does a	958	Wait till the result filehandle becomes ready for reading (simply does a
778	C<select> on the filehandle. This is useful if you want to synchronously wait	959	C<select> on the filehandle. This is useful if you want to synchronously
779	for some requests to finish).	960	wait for some requests to finish).
780		961
781	See C<nreqs> for an example.	962	See C<nreqs> for an example.
782		963
		964	=item IO::AIO::poll
		965
		966	Waits until some requests have been handled.
		967
		968	Strictly equivalent to:
		969
		970	IO::AIO::poll_wait, IO::AIO::poll_cb
		971	if IO::AIO::nreqs;
		972
783	=item IO::AIO::nreqs	973	=item IO::AIO::flush
784		974
785	Returns the number of requests currently outstanding (i.e. for which their	975	Wait till all outstanding AIO requests have been handled.
786	callback has not been invoked yet).
787		976
788	Example: wait till there are no outstanding requests anymore:	977	Strictly equivalent to:
789		978
790	IO::AIO::poll_wait, IO::AIO::poll_cb	979	IO::AIO::poll_wait, IO::AIO::poll_cb
791	while IO::AIO::nreqs;	980	while IO::AIO::nreqs;
792		981
793	=item IO::AIO::flush	982	=head3 CONTROLLING THE NUMBER OF THREADS
794
795	Wait till all outstanding AIO requests have been handled.
796
797	Strictly equivalent to:
798
799	IO::AIO::poll_wait, IO::AIO::poll_cb
800	while IO::AIO::nreqs;
801
802	=item IO::AIO::poll
803
804	Waits until some requests have been handled.
805
806	Strictly equivalent to:
807
808	IO::AIO::poll_wait, IO::AIO::poll_cb
809	if IO::AIO::nreqs;
810		983
811	=item IO::AIO::min_parallel $nthreads	984	=item IO::AIO::min_parallel $nthreads
812		985
813	Set the minimum number of AIO threads to C<$nthreads>. The current	986	Set the minimum number of AIO threads to C<$nthreads>. The current
814	default is C<8>, which means eight asynchronous operations can execute	987	default is C<8>, which means eight asynchronous operations can execute
815	concurrently at any one time (the number of outstanding requests,	988	concurrently at any one time (the number of outstanding requests,
816	however, is unlimited).	989	however, is unlimited).
817		990
818	IO::AIO starts threads only on demand, when an AIO request is queued and	991	IO::AIO starts threads only on demand, when an AIO request is queued and
819	no free thread exists.	992	no free thread exists. Please note that queueing up a hundred requests can
		993	create demand for a hundred threads, even if it turns out that everything
		994	is in the cache and could have been processed faster by a single thread.
820		995
821	It is recommended to keep the number of threads relatively low, as some	996	It is recommended to keep the number of threads relatively low, as some
822	Linux kernel versions will scale negatively with the number of threads	997	Linux kernel versions will scale negatively with the number of threads
823	(higher parallelity => MUCH higher latency). With current Linux 2.6	998	(higher parallelity => MUCH higher latency). With current Linux 2.6
824	versions, 4-32 threads should be fine.	999	versions, 4-32 threads should be fine.
…		…
838	This module automatically runs C<max_parallel 0> at program end, to ensure	1013	This module automatically runs C<max_parallel 0> at program end, to ensure
839	that all threads are killed and that there are no outstanding requests.	1014	that all threads are killed and that there are no outstanding requests.
840		1015
841	Under normal circumstances you don't need to call this function.	1016	Under normal circumstances you don't need to call this function.
842		1017
		1018	=item IO::AIO::max_idle $nthreads
		1019
		1020	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1021	threads that did not get a request to process within 10 seconds). That
		1022	means if a thread becomes idle while C<$nthreads> other threads are also
		1023	idle, it will free its resources and exit.
		1024
		1025	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1026	to allow for extremely high load situations, but want to free resources
		1027	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1028
		1029	The default is probably ok in most situations, especially if thread
		1030	creation is fast. If thread creation is very slow on your system you might
		1031	want to use larger values.
		1032
843	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1033	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
844		1034
845	[DEPRECATED]	1035	This is a very bad function to use in interactive programs because it
		1036	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1037	use an C<aio_group> together with a feed callback.
846		1038
847	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1039	Sets the maximum number of outstanding requests to C<$nreqs>. If you
848	try to queue up more than this number of requests, the caller will block until	1040	to queue up more than this number of requests, the next call to the
849	some requests have been handled.	1041	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1042	function will block until the limit is no longer exceeded.
850		1043
851	The default is very large, so normally there is no practical limit. If you	1044	The default value is very large, so there is no practical limit on the
852	queue up many requests in a loop it often improves speed if you set	1045	number of outstanding requests.
853	this to a relatively low number, such as C<100>.
854		1046
855	This function does not work well together with C<aio_group>'s, and their	1047	You can still queue as many requests as you want. Therefore,
856	feeder interface is better suited to limiting concurrency, so do not use	1048	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
857	this function.	1049	as a stop gap to shield against fatal memory overflow (with large values).
858		1050
859	Under normal circumstances you don't need to call this function.	1051	=head3 STATISTICAL INFORMATION
		1052
		1053	=item IO::AIO::nreqs
		1054
		1055	Returns the number of requests currently in the ready, execute or pending
		1056	states (i.e. for which their callback has not been invoked yet).
		1057
		1058	Example: wait till there are no outstanding requests anymore:
		1059
		1060	IO::AIO::poll_wait, IO::AIO::poll_cb
		1061	while IO::AIO::nreqs;
		1062
		1063	=item IO::AIO::nready
		1064
		1065	Returns the number of requests currently in the ready state (not yet
		1066	executed).
		1067
		1068	=item IO::AIO::npending
		1069
		1070	Returns the number of requests currently in the pending state (executed,
		1071	but not yet processed by poll_cb).
860		1072
861	=back	1073	=back
862		1074
863	=cut	1075	=cut
864		1076
…		…
879	}	1091	}
880		1092
881	min_parallel 8;	1093	min_parallel 8;
882		1094
883	END {	1095	END {
884	max_parallel 0;	1096	min_parallel 1;
885	}	1097	flush;
		1098	};
886		1099
887	1;	1100	1;
888		1101
889	=head2 FORK BEHAVIOUR	1102	=head2 FORK BEHAVIOUR
890		1103
891	This module should do "the right thing" when the process using it forks:	1104	This module should do "the right thing" when the process using it forks:
892		1105
893	Before the fork, IO::AIO enters a quiescent state where no requests	1106	Before the fork, IO::AIO enters a quiescent state where no requests
894	can be added in other threads and no results will be processed. After	1107	can be added in other threads and no results will be processed. After
895	the fork the parent simply leaves the quiescent state and continues	1108	the fork the parent simply leaves the quiescent state and continues
896	request/result processing, while the child clears the request/result	1109	request/result processing, while the child frees the request/result queue
897	queue (so the requests started before the fork will only be handled in	1110	(so that the requests started before the fork will only be handled in the
898	the parent). Threads will be started on demand until the limit ste in the	1111	parent). Threads will be started on demand until the limit set in the
899	parent process has been reached again.	1112	parent process has been reached again.
900		1113
901	In short: the parent will, after a short pause, continue as if fork had	1114	In short: the parent will, after a short pause, continue as if fork had
902	not been called, while the child will act as if IO::AIO has not been used	1115	not been called, while the child will act as if IO::AIO has not been used
903	yet.	1116	yet.
904		1117
905	=head2 MEMORY USAGE	1118	=head2 MEMORY USAGE
906		1119
		1120	Per-request usage:
		1121
907	Each aio request uses - depending on your architecture - around 128 bytes	1122	Each aio request uses - depending on your architecture - around 100-200
908	of memory. In addition, stat requests need a stat buffer (possibly a few	1123	bytes of memory. In addition, stat requests need a stat buffer (possibly
909	hundred bytes). Perl scalars and other data passed into aio requests will	1124	a few hundred bytes), readdir requires a result buffer and so on. Perl
910	also be locked.	1125	scalars and other data passed into aio requests will also be locked and
		1126	will consume memory till the request has entered the done state.
911		1127
912	This is now awfully much, so queuing lots of requests is not usually a	1128	This is now awfully much, so queuing lots of requests is not usually a
913	problem.	1129	problem.
914		1130
915	Each thread needs a stack area which is usually around 16k, sometimes much	1131	Per-thread usage:
916	larger, depending on the OS.	1132
		1133	In the execution phase, some aio requests require more memory for
		1134	temporary buffers, and each thread requires a stack and other data
		1135	structures (usually around 16k-128k, depending on the OS).
		1136
		1137	=head1 KNOWN BUGS
		1138
		1139	Known bugs will be fixed in the next release.
917		1140
918	=head1 SEE ALSO	1141	=head1 SEE ALSO
919		1142
920	L<Coro::AIO>.	1143	L<Coro::AIO>.
921		1144

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.70 by root, Tue Oct 24 03:40:38 2006 UTC vs. Revision 1.86 by root, Sat Oct 28 23:32:29 2006 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.70 by root, Tue Oct 24 03:40:38 2006 UTC vs.
Revision 1.86 by root, Sat Oct 28 23:32:29 2006 UTC