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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.51 by root, Sat Jun 24 19:14:04 2006 UTC vs.
Revision 1.76 by root, Wed Oct 25 08:20:14 2006 UTC

…		…
15		15
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	16	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	17	$_[0] > 0 or die "read error: $!";
18	};	18	};
19		19
20	# AnyEvent	20	# version 2+ has request and group objects
		21	use IO::AIO 2;
		22
		23	aioreq_pri 4; # give next request a very high priority
		24	my $req = aio_unlink "/tmp/file", sub { };
		25	$req->cancel; # cancel request if still in queue
		26
		27	my $grp = aio_group sub { print "all stats done\n" };
		28	add $grp aio_stat "..." for ...;
		29
		30	# AnyEvent integration
21	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
22	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });	32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
23		33
24	# Event	34	# Event integration
25	Event->io (fd => IO::AIO::poll_fileno,	35	Event->io (fd => IO::AIO::poll_fileno,
26	poll => 'r',	36	poll => 'r',
27	cb => \&IO::AIO::poll_cb);	37	cb => \&IO::AIO::poll_cb);
28		38
29	# Glib/Gtk2	39	# Glib/Gtk2 integration
30	add_watch Glib::IO IO::AIO::poll_fileno,	40	add_watch Glib::IO IO::AIO::poll_fileno,
31	in => sub { IO::AIO::poll_cb; 1 };	41	in => sub { IO::AIO::poll_cb; 1 };
32		42
33	# Tk	43	# Tk integration
34	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
35	readable => \&IO::AIO::poll_cb);	45	readable => \&IO::AIO::poll_cb);
36		46
37	# Danga::Socket	47	# Danga::Socket integration
38	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
39	\&IO::AIO::poll_cb);	49	\&IO::AIO::poll_cb);
40		50
41
42	=head1 DESCRIPTION	51	=head1 DESCRIPTION
43		52
44	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
45	operating system supports.	54	operating system supports.
46		55
47	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
48	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
49	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
50	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
51	aio functions available on many operating systems. However, they are often	60	functions available on many operating systems. However, they are often
52	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
53	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
54	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.
55		65
56	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-)
57	currently not reentrant, so use appropriate locking yourself, always call	67	threads, it is currently not reentrant in any way, so use appropriate
58	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
59	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).
60		120
61	=cut	121	=cut
62		122
63	package IO::AIO;	123	package IO::AIO;
64		124
…		…
66	use strict 'vars';	126	use strict 'vars';
67		127
68	use base 'Exporter';	128	use base 'Exporter';
69		129
70	BEGIN {	130	BEGIN {
71	our $VERSION = '1.8';	131	our $VERSION = '2.0';
72		132
73	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
74	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
75	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
76	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	136	aio_group aio_nop);
		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 max_outstanding nreqs);
		140
		141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
77		142
78	require XSLoader;	143	require XSLoader;
79	XSLoader::load ("IO::AIO", $VERSION);	144	XSLoader::load ("IO::AIO", $VERSION);
80	}	145	}
81		146
…		…
92	syscall has been executed asynchronously.	157	syscall has been executed asynchronously.
93		158
94	All functions expecting a filehandle keep a copy of the filehandle	159	All functions expecting a filehandle keep a copy of the filehandle
95	internally until the request has finished.	160	internally until the request has finished.
96		161
		162	All requests return objects of type L<IO::AIO::REQ> that allow further
		163	manipulation of those requests while they are in-flight.
		164
97	The pathnames you pass to these routines I<must> be absolute and	165	The pathnames you pass to these routines I<must> be absolute and
98	encoded in byte form. The reason for the former is that at the time the	166	encoded in byte form. The reason for the former is that at the time the
99	request is being executed, the current working directory could have	167	request is being executed, the current working directory could have
100	changed. Alternatively, you can make sure that you never change the	168	changed. Alternatively, you can make sure that you never change the
101	current working directory.	169	current working directory.
…		…
106	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
107	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)
108	use something else.	176	use something else.
109		177
110	=over 4	178	=over 4
		179
		180	=item aioreq_pri $pri
		181
		182	Sets the priority for the next aio request. The default priority
		183	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,
		184	respectively. Requests with higher priority will be serviced first.
		185
		186	The priority will be reset to C<0> after each call to one of the C<aio_>
		187	functions.
		188
		189	Example: open a file with low priority, then read something from it with
		190	higher priority so the read request is serviced before other low priority
		191	open requests (potentially spamming the cache):
		192
		193	aioreq_pri -3;
		194	aio_open ..., sub {
		195	return unless $_[0];
		196
		197	aioreq_pri -2;
		198	aio_read $_[0], ..., sub {
		199	...
		200	};
		201	};
		202
		203	=item aioreq_nice $pri_adjust
		204
		205	Similar to C<aioreq_pri>, but subtracts the given value from the current
		206	priority, so effects are cumulative.
111		207
112	=item aio_open $pathname, $flags, $mode, $callback->($fh)	208	=item aio_open $pathname, $flags, $mode, $callback->($fh)
113		209
114	Asynchronously open or create a file and call the callback with a newly	210	Asynchronously open or create a file and call the callback with a newly
115	created filehandle for the file.	211	created filehandle for the file.
…		…
168	print "read $_[0] bytes: <$buffer>\n";	264	print "read $_[0] bytes: <$buffer>\n";
169	};	265	};
170		266
171	=item aio_move $srcpath, $dstpath, $callback->($status)	267	=item aio_move $srcpath, $dstpath, $callback->($status)
172		268
173	[EXPERIMENTAL]
174
175	Try to move the I<file> (directories not supported as either source or destination)	269	Try to move the I<file> (directories not supported as either source or
176	from C<$srcpath> to C<$dstpath> and call the callback with the C<0> (error) or C<-1> ok.	270	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		271	the C<0> (error) or C<-1> ok.
177		272
178	This is a composite request that tries to rename(2) the file first. If	273	This is a composite request that tries to rename(2) the file first. If
179	rename files with C<EXDEV>, it creates the destination file with mode 0200	274	rename files with C<EXDEV>, it creates the destination file with mode 0200
180	and copies the contents of the source file into it using C<aio_sendfile>,	275	and copies the contents of the source file into it using C<aio_sendfile>,
181	followed by restoring atime, mtime, access mode and uid/gid, in that	276	followed by restoring atime, mtime, access mode and uid/gid, in that
…		…
188	=cut	283	=cut
189		284
190	sub aio_move($$$) {	285	sub aio_move($$$) {
191	my ($src, $dst, $cb) = @_;	286	my ($src, $dst, $cb) = @_;
192		287
		288	my $grp = aio_group $cb;
		289
193	aio_rename $src, $dst, sub {	290	add $grp aio_rename $src, $dst, sub {
194	if ($_[0] && $! == EXDEV) {	291	if ($_[0] && $! == EXDEV) {
195	aio_open $src, O_RDONLY, 0, sub {	292	add $grp aio_open $src, O_RDONLY, 0, sub {
196	if (my $src_fh = $_[0]) {	293	if (my $src_fh = $_[0]) {
197	my @stat = stat $src_fh;	294	my @stat = stat $src_fh;
198		295
199	aio_open $dst, O_WRONLY, 0200, sub {	296	add $grp aio_open $dst, O_WRONLY, 0200, sub {
200	if (my $dst_fh = $_[0]) {	297	if (my $dst_fh = $_[0]) {
201	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	298	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
202	close $src_fh;	299	close $src_fh;
203		300
204	if ($_[0] == $stat[7]) {	301	if ($_[0] == $stat[7]) {
205	utime $stat[8], $stat[9], $dst;	302	utime $stat[8], $stat[9], $dst;
206	chmod $stat[2] & 07777, $dst_fh;	303	chmod $stat[2] & 07777, $dst_fh;
207	chown $stat[4], $stat[5], $dst_fh;	304	chown $stat[4], $stat[5], $dst_fh;
208	close $dst_fh;	305	close $dst_fh;
209		306
210	aio_unlink $src, sub {	307	add $grp aio_unlink $src, sub {
211	$cb->($_[0]);	308	$grp->result ($_[0]);
212	};	309	};
213	} else {	310	} else {
214	my $errno = $!;	311	my $errno = $!;
215	aio_unlink $dst, sub {	312	add $grp aio_unlink $dst, sub {
216	$! = $errno;	313	$! = $errno;
217	$cb->(-1);	314	$grp->result (-1);
218	};	315	};
219	}	316	}
220	};	317	};
221	} else {	318	} else {
222	$cb->(-1);	319	$grp->result (-1);
223	}	320	}
224	},	321	},
225		322
226	} else {	323	} else {
227	$cb->(-1);	324	$grp->result (-1);
228	}	325	}
229	};	326	};
230	} else {	327	} else {
231	$cb->($_[0]);	328	$grp->result ($_[0]);
232	}	329	}
233	};	330	};
		331
		332	$grp
234	}	333	}
235		334
236	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	335	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
237		336
238	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	337	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
…		…
326	The callback a single argument which is either C<undef> or an array-ref	425	The callback a single argument which is either C<undef> or an array-ref
327	with the filenames.	426	with the filenames.
328		427
329	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	428	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
330		429
331	Scans a directory (similar to C<aio_readdir>) and tries to separate the	430	Scans a directory (similar to C<aio_readdir>) but additionally tries to
332	entries of directory C<$path> into two sets of names, ones you can recurse	431	efficiently separate the entries of directory C<$path> into two sets of
333	into (directories), and ones you cannot recurse into (everything else).	432	names, directories you can recurse into (directories), and ones you cannot
		433	recurse into (everything else, including symlinks to directories).
334		434
335	C<aio_scandir> is a composite request that consists of many	435	C<aio_scandir> is a composite request that creates of many sub requests_
336	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	436	C<$maxreq> specifies the maximum number of outstanding aio requests that
337	aio requests that this function generates. If it is C<< <= 0 >>, then a	437	this function generates. If it is C<< <= 0 >>, then a suitable default
338	suitable default will be chosen (currently 8).	438	will be chosen (currently 6).
339		439
340	On error, the callback is called without arguments, otherwise it receives	440	On error, the callback is called without arguments, otherwise it receives
341	two array-refs with path-relative entry names.	441	two array-refs with path-relative entry names.
342		442
343	Example:	443	Example:
…		…
351	Implementation notes.	451	Implementation notes.
352		452
353	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	453	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
354		454
355	After reading the directory, the modification time, size etc. of the	455	After reading the directory, the modification time, size etc. of the
356	directory before and after the readdir is checked, and if they match, the	456	directory before and after the readdir is checked, and if they match (and
357	link count will be used to decide how many entries are directories (if	457	isn't the current time), the link count will be used to decide how many
358	>= 2). Otherwise, no knowledge of the number of subdirectories will be	458	entries are directories (if >= 2). Otherwise, no knowledge of the number
359	assumed.	459	of subdirectories will be assumed.
360		460
361	Then entires will be sorted into likely directories (everything without a	461	Then entries will be sorted into likely directories (everything without
362	non-initial dot) and likely non-directories (everything else). Then every	462	a non-initial dot currently) and likely non-directories (everything
363	entry + C</.> will be C<stat>'ed, likely directories first. This is often	463	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		464	likely directories first. If that succeeds, it assumes that the entry
		465	is a directory or a symlink to directory (which will be checked
		466	seperately). This is often faster than stat'ing the entry itself because
364	faster because filesystems might detect the type of the entry without	467	filesystems might detect the type of the entry without reading the inode
365	reading the inode data (e.g. ext2fs filetype feature). If that succeeds,	468	data (e.g. ext2fs filetype feature).
366	it assumes that the entry is a directory or a symlink to directory (which
367	will be checked seperately).
368		469
369	If the known number of directories has been reached, the rest of the	470	If the known number of directories (link count - 2) has been reached, the
370	entries is assumed to be non-directories.	471	rest of the entries is assumed to be non-directories.
		472
		473	This only works with certainty on POSIX (= UNIX) filesystems, which
		474	fortunately are the vast majority of filesystems around.
		475
		476	It will also likely work on non-POSIX filesystems with reduced efficiency
		477	as those tend to return 0 or 1 as link counts, which disables the
		478	directory counting heuristic.
371		479
372	=cut	480	=cut
373		481
374	sub aio_scandir($$$) {	482	sub aio_scandir($$$) {
375	my ($path, $maxreq, $cb) = @_;	483	my ($path, $maxreq, $cb) = @_;
376		484
		485	my $grp = aio_group $cb;
		486
377	$maxreq = 8 if $maxreq <= 0;	487	$maxreq = 6 if $maxreq <= 0;
378		488
379	# stat once	489	# stat once
380	aio_stat $path, sub {	490	add $grp aio_stat $path, sub {
381	return $cb->() if $_[0];	491	return $grp->result () if $_[0];
		492	my $now = time;
382	my $hash1 = join ":", (stat _)[0,1,3,7,9];	493	my $hash1 = join ":", (stat _)[0,1,3,7,9];
383		494
384	# read the directory entries	495	# read the directory entries
385	aio_readdir $path, sub {	496	add $grp aio_readdir $path, sub {
386	my $entries = shift	497	my $entries = shift
387	or return $cb->();	498	or return $grp->result ();
388		499
389	# stat the dir another time	500	# stat the dir another time
390	aio_stat $path, sub {	501	add $grp aio_stat $path, sub {
391	my $hash2 = join ":", (stat _)[0,1,3,7,9];	502	my $hash2 = join ":", (stat _)[0,1,3,7,9];
392		503
393	my $ndirs;	504	my $ndirs;
394		505
395	# take the slow route if anything looks fishy	506	# take the slow route if anything looks fishy
396	if ($hash1 ne $hash2) {	507	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
397	$ndirs = -1;	508	$ndirs = -1;
398	} else {	509	} else {
399	# if nlink == 2, we are finished	510	# if nlink == 2, we are finished
400	# on non-posix-fs's, we rely on nlink < 2	511	# on non-posix-fs's, we rely on nlink < 2
401	$ndirs = (stat _)[3] - 2	512	$ndirs = (stat _)[3] - 2
402	or return $cb->([], $entries);	513	or return $grp->result ([], $entries);
403	}	514	}
404		515
405	# sort into likely dirs and likely nondirs	516	# sort into likely dirs and likely nondirs
406	# dirs == files without ".", short entries first	517	# dirs == files without ".", short entries first
407	$entries = [map $_->[0],	518	$entries = [map $_->[0],
…		…
409	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	520	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
410	@$entries];	521	@$entries];
411		522
412	my (@dirs, @nondirs);	523	my (@dirs, @nondirs);
413		524
414	my ($statcb, $schedcb);	525	my $statgrp = add $grp aio_group sub {
415	my $nreq = 0;	526	$grp->result (\@dirs, \@nondirs);
		527	};
416		528
417	$schedcb = sub {	529	limit $statgrp $maxreq;
418	if (@$entries) {	530	feed $statgrp sub {
419	if ($nreq < $maxreq) {	531	return unless @$entries;
420	my $ent = pop @$entries;	532	my $entry = pop @$entries;
		533
		534	add $statgrp aio_stat "$path/$entry/.", sub {
		535	if ($_[0] < 0) {
		536	push @nondirs, $entry;
		537	} else {
		538	# need to check for real directory
		539	add $statgrp aio_lstat "$path/$entry", sub {
		540	if (-d _) {
		541	push @dirs, $entry;
		542
		543	unless (--$ndirs) {
		544	push @nondirs, @$entries;
		545	feed $statgrp;
		546	}
		547	} else {
		548	push @nondirs, $entry;
		549	}
421	$nreq++;	550	}
422	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
423	}	551	}
424	} elsif (!$nreq) {
425	# finished
426	undef $statcb;
427	undef $schedcb;
428	$cb->(\@dirs, \@nondirs) if $cb;
429	undef $cb;
430	}	552	};
431	};	553	};
432	$statcb = sub {
433	my ($status, $entry) = @_;
434
435	if ($status < 0) {
436	$nreq--;
437	push @nondirs, $entry;
438	&$schedcb;
439	} else {
440	# need to check for real directory
441	aio_lstat "$path/$entry", sub {
442	$nreq--;
443
444	if (-d _) {
445	push @dirs, $entry;
446
447	if (!--$ndirs) {
448	push @nondirs, @$entries;
449	$entries = [];
450	}
451	} else {
452	push @nondirs, $entry;
453	}
454
455	&$schedcb;
456	}
457	}
458	};
459
460	&$schedcb while @$entries && $nreq < $maxreq;
461	};	554	};
462	};	555	};
463	};	556	};
		557
		558	$grp
464	}	559	}
465		560
466	=item aio_fsync $fh, $callback->($status)	561	=item aio_fsync $fh, $callback->($status)
467		562
468	Asynchronously call fsync on the given filehandle and call the callback	563	Asynchronously call fsync on the given filehandle and call the callback
…		…
473	Asynchronously call fdatasync on the given filehandle and call the	568	Asynchronously call fdatasync on the given filehandle and call the
474	callback with the fdatasync result code.	569	callback with the fdatasync result code.
475		570
476	If this call isn't available because your OS lacks it or it couldn't be	571	If this call isn't available because your OS lacks it or it couldn't be
477	detected, it will be emulated by calling C<fsync> instead.	572	detected, it will be emulated by calling C<fsync> instead.
		573
		574	=item aio_group $callback->(...)
		575
		576	This is a very special aio request: Instead of doing something, it is a
		577	container for other aio requests, which is useful if you want to bundle
		578	many requests into a single, composite, request with a definite callback
		579	and the ability to cancel the whole request with its subrequests.
		580
		581	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		582	for more info.
		583
		584	Example:
		585
		586	my $grp = aio_group sub {
		587	print "all stats done\n";
		588	};
		589
		590	add $grp
		591	(aio_stat ...),
		592	(aio_stat ...),
		593	...;
		594
		595	=item aio_nop $callback->()
		596
		597	This is a special request - it does nothing in itself and is only used for
		598	side effects, such as when you want to add a dummy request to a group so
		599	that finishing the requests in the group depends on executing the given
		600	code.
		601
		602	While this request does nothing, it still goes through the execution
		603	phase and still requires a worker thread. Thus, the callback will not
		604	be executed immediately but only after other requests in the queue have
		605	entered their execution phase. This can be used to measure request
		606	latency.
		607
		608	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		609
		610	Mainly used for debugging and benchmarking, this aio request puts one of
		611	the request workers to sleep for the given time.
		612
		613	While it is theoretically handy to have simple I/O scheduling requests
		614	like sleep and file handle readable/writable, the overhead this creates is
		615	immense (it blocks a thread for a long time) so do not use this function
		616	except to put your application under artificial I/O pressure.
		617
		618	=back
		619
		620	=head2 IO::AIO::REQ CLASS
		621
		622	All non-aggregate C<aio_*> functions return an object of this class when
		623	called in non-void context.
		624
		625	=over 4
		626
		627	=item cancel $req
		628
		629	Cancels the request, if possible. Has the effect of skipping execution
		630	when entering the B<execute> state and skipping calling the callback when
		631	entering the the B<result> state, but will leave the request otherwise
		632	untouched. That means that requests that currently execute will not be
		633	stopped and resources held by the request will not be freed prematurely.
		634
		635	=item cb $req $callback->(...)
		636
		637	Replace (or simply set) the callback registered to the request.
		638
		639	=back
		640
		641	=head2 IO::AIO::GRP CLASS
		642
		643	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		644	objects of this class, too.
		645
		646	A IO::AIO::GRP object is a special request that can contain multiple other
		647	aio requests.
		648
		649	You create one by calling the C<aio_group> constructing function with a
		650	callback that will be called when all contained requests have entered the
		651	C<done> state:
		652
		653	my $grp = aio_group sub {
		654	print "all requests are done\n";
		655	};
		656
		657	You add requests by calling the C<add> method with one or more
		658	C<IO::AIO::REQ> objects:
		659
		660	$grp->add (aio_unlink "...");
		661
		662	add $grp aio_stat "...", sub {
		663	$_[0] or return $grp->result ("error");
		664
		665	# add another request dynamically, if first succeeded
		666	add $grp aio_open "...", sub {
		667	$grp->result ("ok");
		668	};
		669	};
		670
		671	This makes it very easy to create composite requests (see the source of
		672	C<aio_move> for an application) that work and feel like simple requests.
		673
		674	=over 4
		675
		676	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		677	C<IO::AIO::poll_cb>, just like any other request.
		678
		679	=item * They can be canceled like any other request. Canceling will cancel not
		680	only the request itself, but also all requests it contains.
		681
		682	=item * They can also can also be added to other IO::AIO::GRP objects.
		683
		684	=item * You must not add requests to a group from within the group callback (or
		685	any later time).
		686
		687	=item * This does not harmonise well with C<max_outstanding>, so best do
		688	not combine C<aio_group> with it. Groups and feeders are recommended for
		689	this kind of concurrency-limiting.
		690
		691	=back
		692
		693	Their lifetime, simplified, looks like this: when they are empty, they
		694	will finish very quickly. If they contain only requests that are in the
		695	C<done> state, they will also finish. Otherwise they will continue to
		696	exist.
		697
		698	That means after creating a group you have some time to add requests. And
		699	in the callbacks of those requests, you can add further requests to the
		700	group. And only when all those requests have finished will the the group
		701	itself finish.
		702
		703	=over 4
		704
		705	=item add $grp ...
		706
		707	=item $grp->add (...)
		708
		709	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		710	be added, including other groups, as long as you do not create circular
		711	dependencies.
		712
		713	Returns all its arguments.
		714
		715	=item $grp->cancel_subs
		716
		717	Cancel all subrequests and clears any feeder, but not the group request
		718	itself. Useful when you queued a lot of events but got a result early.
		719
		720	=item $grp->result (...)
		721
		722	Set the result value(s) that will be passed to the group callback when all
		723	subrequests have finished. By default, no argument will be passed.
		724
		725	=item feed $grp $callback->($grp)
		726
		727	Sets a feeder/generator on this group: every group can have an attached
		728	generator that generates requests if idle. The idea behind this is that,
		729	although you could just queue as many requests as you want in a group,
		730	this might starve other requests for a potentially long time. For
		731	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		732	requests, delaying any later requests for a long time.
		733
		734	To avoid this, and allow incremental generation of requests, you can
		735	instead a group and set a feeder on it that generates those requests. The
		736	feed callback will be called whenever there are few enough (see C<limit>,
		737	below) requests active in the group itself and is expected to queue more
		738	requests.
		739
		740	The feed callback can queue as many requests as it likes (i.e. C<add> does
		741	not impose any limits).
		742
		743	If the feed does not queue more requests when called, it will be
		744	automatically removed from the group.
		745
		746	If the feed limit is C<0>, it will be set to C<2> automatically.
		747
		748	Example:
		749
		750	# stat all files in @files, but only ever use four aio requests concurrently:
		751
		752	my $grp = aio_group sub { print "finished\n" };
		753	limit $grp 4;
		754	feed $grp sub {
		755	my $file = pop @files
		756	or return;
		757
		758	add $grp aio_stat $file, sub { ... };
		759	};
		760
		761	=item limit $grp $num
		762
		763	Sets the feeder limit for the group: The feeder will be called whenever
		764	the group contains less than this many requests.
		765
		766	Setting the limit to C<0> will pause the feeding process.
478		767
479	=back	768	=back
480		769
481	=head2 SUPPORT FUNCTIONS	770	=head2 SUPPORT FUNCTIONS
482		771
…		…
540	IO::AIO::poll_wait, IO::AIO::poll_cb	829	IO::AIO::poll_wait, IO::AIO::poll_cb
541	if IO::AIO::nreqs;	830	if IO::AIO::nreqs;
542		831
543	=item IO::AIO::min_parallel $nthreads	832	=item IO::AIO::min_parallel $nthreads
544		833
545	Set the minimum number of AIO threads to C<$nthreads>. The current default	834	Set the minimum number of AIO threads to C<$nthreads>. The current
546	is C<4>, which means four asynchronous operations can be done at one time	835	default is C<8>, which means eight asynchronous operations can execute
547	(the number of outstanding operations, however, is unlimited).	836	concurrently at any one time (the number of outstanding requests,
		837	however, is unlimited).
548		838
549	IO::AIO starts threads only on demand, when an AIO request is queued and	839	IO::AIO starts threads only on demand, when an AIO request is queued and
550	no free thread exists.	840	no free thread exists.
551		841
552	It is recommended to keep the number of threads low, as some Linux	842	It is recommended to keep the number of threads relatively low, as some
553	kernel versions will scale negatively with the number of threads (higher	843	Linux kernel versions will scale negatively with the number of threads
554	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	844	(higher parallelity => MUCH higher latency). With current Linux 2.6
555	threads should be fine.	845	versions, 4-32 threads should be fine.
556		846
557	Under most circumstances you don't need to call this function, as the	847	Under most circumstances you don't need to call this function, as the
558	module selects a default that is suitable for low to moderate load.	848	module selects a default that is suitable for low to moderate load.
559		849
560	=item IO::AIO::max_parallel $nthreads	850	=item IO::AIO::max_parallel $nthreads
…		…
571		861
572	Under normal circumstances you don't need to call this function.	862	Under normal circumstances you don't need to call this function.
573		863
574	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	864	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
575		865
		866	[DEPRECATED]
		867
576	Sets the maximum number of outstanding requests to C<$nreqs>. If you	868	Sets the maximum number of outstanding requests to C<$nreqs>. If you
577	try to queue up more than this number of requests, the caller will block until	869	try to queue up more than this number of requests, the caller will block until
578	some requests have been handled.	870	some requests have been handled.
579		871
580	The default is very large, so normally there is no practical limit. If you	872	The default is very large, so normally there is no practical limit. If you
581	queue up many requests in a loop it often improves speed if you set	873	queue up many requests in a loop it often improves speed if you set
582	this to a relatively low number, such as C<100>.	874	this to a relatively low number, such as C<100>.
		875
		876	This function does not work well together with C<aio_group>'s, and their
		877	feeder interface is better suited to limiting concurrency, so do not use
		878	this function.
583		879
584	Under normal circumstances you don't need to call this function.	880	Under normal circumstances you don't need to call this function.
585		881
586	=back	882	=back
587		883
…		…
601	or return undef;	897	or return undef;
602		898
603	*$sym	899	*$sym
604	}	900	}
605		901
606	min_parallel 4;	902	min_parallel 8;
607		903
608	END {	904	END {
609	max_parallel 0;	905	max_parallel 0;
610	}	906	}
611		907
612	1;	908	1;
613		909
614	=head2 FORK BEHAVIOUR	910	=head2 FORK BEHAVIOUR
615		911
		912	This module should do "the right thing" when the process using it forks:
		913
616	Before the fork, IO::AIO enters a quiescent state where no requests	914	Before the fork, IO::AIO enters a quiescent state where no requests
617	can be added in other threads and no results will be processed. After	915	can be added in other threads and no results will be processed. After
618	the fork the parent simply leaves the quiescent state and continues	916	the fork the parent simply leaves the quiescent state and continues
619	request/result processing, while the child clears the request/result	917	request/result processing, while the child frees the request/result queue
620	queue (so the requests started before the fork will only be handled in	918	(so that the requests started before the fork will only be handled in the
621	the parent). Threats will be started on demand until the limit ste in the	919	parent). Threads will be started on demand until the limit set in the
622	parent process has been reached again.	920	parent process has been reached again.
623		921
		922	In short: the parent will, after a short pause, continue as if fork had
		923	not been called, while the child will act as if IO::AIO has not been used
		924	yet.
		925
		926	=head2 MEMORY USAGE
		927
		928	Per-request usage:
		929
		930	Each aio request uses - depending on your architecture - around 100-200
		931	bytes of memory. In addition, stat requests need a stat buffer (possibly
		932	a few hundred bytes), readdir requires a result buffer and so on. Perl
		933	scalars and other data passed into aio requests will also be locked and
		934	will consume memory till the request has entered the done state.
		935
		936	This is now awfully much, so queuing lots of requests is not usually a
		937	problem.
		938
		939	Per-thread usage:
		940
		941	In the execution phase, some aio requests require more memory for
		942	temporary buffers, and each thread requires a stack and other data
		943	structures (usually around 16k-128k, depending on the OS).
		944
		945	=head1 KNOWN BUGS
		946
		947	Known bugs will be fixed in the next release.
		948
624	=head1 SEE ALSO	949	=head1 SEE ALSO
625		950
626	L<Coro>, L<Linux::AIO>.	951	L<Coro::AIO>.
627		952
628	=head1 AUTHOR	953	=head1 AUTHOR
629		954
630	Marc Lehmann <schmorp@schmorp.de>	955	Marc Lehmann <schmorp@schmorp.de>
631	http://home.schmorp.de/	956	http://home.schmorp.de/

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Revision 1.76 by root, Wed Oct 25 08:20:14 2006 UTC