[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 1.73 by root, Tue Oct 24 16:35:04 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	separate the entries of directory C<$path> into two sets of names, ones
333	into (directories), and ones you cannot recurse into (everything else).	432	you can recurse into (directories or links to them), and ones you cannot
		433	recurse into (everything else).
334		434
335	C<aio_scandir> is a composite request that consists of many	435	C<aio_scandir> is a composite request that creates of many sub requests_
336	aio-primitives. C<$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 $_->[0],
…		…
412	my (@dirs, @nondirs);	523	my (@dirs, @nondirs);
413		524
414	my ($statcb, $schedcb);	525	my ($statcb, $schedcb);
415	my $nreq = 0;	526	my $nreq = 0;
416		527
		528	my $statgrp = add $grp aio_group;
		529
417	$schedcb = sub {	530	$schedcb = sub {
418	if (@$entries) {	531	if (@$entries) {
419	if ($nreq < $maxreq) {	532	if ($nreq < $maxreq) {
420	my $ent = pop @$entries;	533	my $ent = pop @$entries;
421	$nreq++;	534	$nreq++;
422	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };	535	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
423	}	536	}
424	} elsif (!$nreq) {	537	} elsif (!$nreq) {
425	# finished	538	# finished
		539	$statgrp->cancel;
426	undef $statcb;	540	undef $statcb;
427	undef $schedcb;	541	undef $schedcb;
428	$cb->(\@dirs, \@nondirs) if $cb;	542	$grp->result (\@dirs, \@nondirs);
429	undef $cb;
430	}	543	}
431	};	544	};
432	$statcb = sub {	545	$statcb = sub {
433	my ($status, $entry) = @_;	546	my ($status, $entry) = @_;
434		547
…		…
436	$nreq--;	549	$nreq--;
437	push @nondirs, $entry;	550	push @nondirs, $entry;
438	&$schedcb;	551	&$schedcb;
439	} else {	552	} else {
440	# need to check for real directory	553	# need to check for real directory
441	aio_lstat "$path/$entry", sub {	554	add $grp aio_lstat "$path/$entry", sub {
442	$nreq--;	555	$nreq--;
443		556
444	if (-d _) {	557	if (-d _) {
445	push @dirs, $entry;	558	push @dirs, $entry;
446		559
…		…
459		572
460	&$schedcb while @$entries && $nreq < $maxreq;	573	&$schedcb while @$entries && $nreq < $maxreq;
461	};	574	};
462	};	575	};
463	};	576	};
		577
		578	$grp
464	}	579	}
465		580
466	=item aio_fsync $fh, $callback->($status)	581	=item aio_fsync $fh, $callback->($status)
467		582
468	Asynchronously call fsync on the given filehandle and call the callback	583	Asynchronously call fsync on the given filehandle and call the callback
…		…
473	Asynchronously call fdatasync on the given filehandle and call the	588	Asynchronously call fdatasync on the given filehandle and call the
474	callback with the fdatasync result code.	589	callback with the fdatasync result code.
475		590
476	If this call isn't available because your OS lacks it or it couldn't be	591	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.	592	detected, it will be emulated by calling C<fsync> instead.
		593
		594	=item aio_group $callback->(...)
		595
		596	[EXPERIMENTAL]
		597
		598	This is a very special aio request: Instead of doing something, it is a
		599	container for other aio requests, which is useful if you want to bundle
		600	many requests into a single, composite, request with a definite callback
		601	and the ability to cancel the whole request with its subrequests.
		602
		603	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		604	for more info.
		605
		606	Example:
		607
		608	my $grp = aio_group sub {
		609	print "all stats done\n";
		610	};
		611
		612	add $grp
		613	(aio_stat ...),
		614	(aio_stat ...),
		615	...;
		616
		617	=item aio_nop $callback->()
		618
		619	This is a special request - it does nothing in itself and is only used for
		620	side effects, such as when you want to add a dummy request to a group so
		621	that finishing the requests in the group depends on executing the given
		622	code.
		623
		624	While this request does nothing, it still goes through the execution
		625	phase and still requires a worker thread. Thus, the callback will not
		626	be executed immediately but only after other requests in the queue have
		627	entered their execution phase. This can be used to measure request
		628	latency.
		629
		630	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		631
		632	Mainly used for debugging and benchmarking, this aio request puts one of
		633	the request workers to sleep for the given time.
		634
		635	While it is theoretically handy to have simple I/O scheduling requests
		636	like sleep and file handle readable/writable, the overhead this creates is
		637	immense (it blocks a thread for a long time) so do not use this function
		638	except to put your application under artificial I/O pressure.
		639
		640	=back
		641
		642	=head2 IO::AIO::REQ CLASS
		643
		644	All non-aggregate C<aio_*> functions return an object of this class when
		645	called in non-void context.
		646
		647	=over 4
		648
		649	=item cancel $req
		650
		651	Cancels the request, if possible. Has the effect of skipping execution
		652	when entering the B<execute> state and skipping calling the callback when
		653	entering the the B<result> state, but will leave the request otherwise
		654	untouched. That means that requests that currently execute will not be
		655	stopped and resources held by the request will not be freed prematurely.
		656
		657	=item cb $req $callback->(...)
		658
		659	Replace (or simply set) the callback registered to the request.
		660
		661	=back
		662
		663	=head2 IO::AIO::GRP CLASS
		664
		665	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		666	objects of this class, too.
		667
		668	A IO::AIO::GRP object is a special request that can contain multiple other
		669	aio requests.
		670
		671	You create one by calling the C<aio_group> constructing function with a
		672	callback that will be called when all contained requests have entered the
		673	C<done> state:
		674
		675	my $grp = aio_group sub {
		676	print "all requests are done\n";
		677	};
		678
		679	You add requests by calling the C<add> method with one or more
		680	C<IO::AIO::REQ> objects:
		681
		682	$grp->add (aio_unlink "...");
		683
		684	add $grp aio_stat "...", sub {
		685	$_[0] or return $grp->result ("error");
		686
		687	# add another request dynamically, if first succeeded
		688	add $grp aio_open "...", sub {
		689	$grp->result ("ok");
		690	};
		691	};
		692
		693	This makes it very easy to create composite requests (see the source of
		694	C<aio_move> for an application) that work and feel like simple requests.
		695
		696	=over 4
		697
		698	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		699	C<IO::AIO::poll_cb>, just like any other request.
		700
		701	=item * They can be canceled like any other request. Canceling will cancel not
		702	only the request itself, but also all requests it contains.
		703
		704	=item * They can also can also be added to other IO::AIO::GRP objects.
		705
		706	=item * You must not add requests to a group from within the group callback (or
		707	any later time).
		708
		709	=item * This does not harmonise well with C<max_outstanding>, so best do
		710	not combine C<aio_group> with it. Groups and feeders are recommended for
		711	this kind of concurrency-limiting.
		712
		713	=back
		714
		715	Their lifetime, simplified, looks like this: when they are empty, they
		716	will finish very quickly. If they contain only requests that are in the
		717	C<done> state, they will also finish. Otherwise they will continue to
		718	exist.
		719
		720	That means after creating a group you have some time to add requests. And
		721	in the callbacks of those requests, you can add further requests to the
		722	group. And only when all those requests have finished will the the group
		723	itself finish.
		724
		725	=over 4
		726
		727	=item add $grp ...
		728
		729	=item $grp->add (...)
		730
		731	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		732	be added, including other groups, as long as you do not create circular
		733	dependencies.
		734
		735	Returns all its arguments.
		736
		737	=item $grp->result (...)
		738
		739	Set the result value(s) that will be passed to the group callback when all
		740	subrequests have finished. By default, no argument will be passed.
		741
		742	=item feed $grp $callback->($grp)
		743
		744	[VERY EXPERIMENTAL]
		745
		746	Sets a feeder/generator on this group: every group can have an attached
		747	generator that generates requests if idle. The idea behind this is that,
		748	although you could just queue as many requests as you want in a group,
		749	this might starve other requests for a potentially long time. For
		750	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		751	requests, delaying any later requests for a long time.
		752
		753	To avoid this, and allow incremental generation of requests, you can
		754	instead a group and set a feeder on it that generates those requests. The
		755	feed callback will be called whenever there are few enough (see C<limit>,
		756	below) requests active in the group itself and is expected to queue more
		757	requests.
		758
		759	The feed callback can queue as many requests as it likes (i.e. C<add> does
		760	not impose any limits).
		761
		762	If the feed does not queue more requests when called, it will be
		763	automatically removed from the group.
		764
		765	If the feed limit is C<0>, it will be set to C<2> automatically.
		766
		767	Example:
		768
		769	# stat all files in @files, but only ever use four aio requests concurrently:
		770
		771	my $grp = aio_group sub { print "finished\n" };
		772	limit $grp 4;
		773	feed $grp sub {
		774	my $file = pop @files
		775	or return;
		776
		777	add $grp aio_stat $file, sub { ... };
		778	};
		779
		780	=item limit $grp $num
		781
		782	Sets the feeder limit for the group: The feeder will be called whenever
		783	the group contains less than this many requests.
		784
		785	Setting the limit to C<0> will pause the feeding process.
478		786
479	=back	787	=back
480		788
481	=head2 SUPPORT FUNCTIONS	789	=head2 SUPPORT FUNCTIONS
482		790
…		…
540	IO::AIO::poll_wait, IO::AIO::poll_cb	848	IO::AIO::poll_wait, IO::AIO::poll_cb
541	if IO::AIO::nreqs;	849	if IO::AIO::nreqs;
542		850
543	=item IO::AIO::min_parallel $nthreads	851	=item IO::AIO::min_parallel $nthreads
544		852
545	Set the minimum number of AIO threads to C<$nthreads>. The current default	853	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	854	default is C<8>, which means eight asynchronous operations can execute
547	(the number of outstanding operations, however, is unlimited).	855	concurrently at any one time (the number of outstanding requests,
		856	however, is unlimited).
548		857
549	IO::AIO starts threads only on demand, when an AIO request is queued and	858	IO::AIO starts threads only on demand, when an AIO request is queued and
550	no free thread exists.	859	no free thread exists.
551		860
552	It is recommended to keep the number of threads low, as some Linux	861	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	862	Linux kernel versions will scale negatively with the number of threads
554	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	863	(higher parallelity => MUCH higher latency). With current Linux 2.6
555	threads should be fine.	864	versions, 4-32 threads should be fine.
556		865
557	Under most circumstances you don't need to call this function, as the	866	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.	867	module selects a default that is suitable for low to moderate load.
559		868
560	=item IO::AIO::max_parallel $nthreads	869	=item IO::AIO::max_parallel $nthreads
…		…
571		880
572	Under normal circumstances you don't need to call this function.	881	Under normal circumstances you don't need to call this function.
573		882
574	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	883	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
575		884
		885	[DEPRECATED]
		886
576	Sets the maximum number of outstanding requests to C<$nreqs>. If you	887	Sets the maximum number of outstanding requests to C<$nreqs>. If you
577	try to queue up more than this number of requests, the caller will block until	888	try to queue up more than this number of requests, the caller will block until
578	some requests have been handled.	889	some requests have been handled.
579		890
580	The default is very large, so normally there is no practical limit. If you	891	The default is very large, so normally there is no practical limit. If you
581	queue up many requests in a loop it often improves speed if you set	892	queue up many requests in a loop it often improves speed if you set
582	this to a relatively low number, such as C<100>.	893	this to a relatively low number, such as C<100>.
		894
		895	This function does not work well together with C<aio_group>'s, and their
		896	feeder interface is better suited to limiting concurrency, so do not use
		897	this function.
583		898
584	Under normal circumstances you don't need to call this function.	899	Under normal circumstances you don't need to call this function.
585		900
586	=back	901	=back
587		902
…		…
601	or return undef;	916	or return undef;
602		917
603	*$sym	918	*$sym
604	}	919	}
605		920
606	min_parallel 4;	921	min_parallel 8;
607		922
608	END {	923	END {
609	max_parallel 0;	924	max_parallel 0;
610	}	925	}
611		926
612	1;	927	1;
613		928
614	=head2 FORK BEHAVIOUR	929	=head2 FORK BEHAVIOUR
615		930
		931	This module should do "the right thing" when the process using it forks:
		932
616	Before the fork, IO::AIO enters a quiescent state where no requests	933	Before the fork, IO::AIO enters a quiescent state where no requests
617	can be added in other threads and no results will be processed. After	934	can be added in other threads and no results will be processed. After
618	the fork the parent simply leaves the quiescent state and continues	935	the fork the parent simply leaves the quiescent state and continues
619	request/result processing, while the child clears the request/result	936	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	937	(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	938	parent). Threads will be started on demand until the limit set in the
622	parent process has been reached again.	939	parent process has been reached again.
623		940
		941	In short: the parent will, after a short pause, continue as if fork had
		942	not been called, while the child will act as if IO::AIO has not been used
		943	yet.
		944
		945	=head2 MEMORY USAGE
		946
		947	Per-request usage:
		948
		949	Each aio request uses - depending on your architecture - around 100-200
		950	bytes of memory. In addition, stat requests need a stat buffer (possibly
		951	a few hundred bytes), readdir requires a result buffer and so on. Perl
		952	scalars and other data passed into aio requests will also be locked and
		953	will consume memory till the request has entered the done state.
		954
		955	This is now awfully much, so queuing lots of requests is not usually a
		956	problem.
		957
		958	Per-thread usage:
		959
		960	In the execution phase, some aio requests require more memory for
		961	temporary buffers, and each thread requires a stack and other data
		962	structures (usually around 16k-128k, depending on the OS).
		963
		964	=head1 KNOWN BUGS
		965
		966	Known bugs will be fixed in the next release.
		967
624	=head1 SEE ALSO	968	=head1 SEE ALSO
625		969
626	L<Coro>, L<Linux::AIO>.	970	L<Coro::AIO>.
627		971
628	=head1 AUTHOR	972	=head1 AUTHOR
629		973
630	Marc Lehmann <schmorp@schmorp.de>	974	Marc Lehmann <schmorp@schmorp.de>
631	http://home.schmorp.de/	975	http://home.schmorp.de/

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Revision 1.73 by root, Tue Oct 24 16:35:04 2006 UTC