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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.67 by root, Tue Oct 24 02:25:16 2006 UTC vs.
Revision 1.86 by root, Sat Oct 28 23:32:29 2006 UTC

…		…
18	};	18	};
19		19
20	# version 2+ has request and group objects	20	# version 2+ has request and group objects
21	use IO::AIO 2;	21	use IO::AIO 2;
22		22
		23	aioreq_pri 4; # give next request a very high priority
23	my $req = aio_unlink "/tmp/file", sub { };	24	my $req = aio_unlink "/tmp/file", sub { };
24	$req->cancel; # cancel request if still in queue	25	$req->cancel; # cancel request if still in queue
25		26
26	my $grp = aio_group sub { print "all stats done\n" };	27	my $grp = aio_group sub { print "all stats done\n" };
27	add $grp aio_stat "..." for ...;	28	add $grp aio_stat "..." for ...;
…		…
50	=head1 DESCRIPTION	51	=head1 DESCRIPTION
51		52
52	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
53	operating system supports.	54	operating system supports.
54		55
		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
55	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
56	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
57	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
58	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
59	on many operating systems. However, they are often not well-supported	76	functions available on many operating systems. However, they are often
60	(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
61	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
62	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.
63		81
64	Although the module will work with in the presence of other threads, it is	82	Although the module will work with in the presence of other (Perl-)
65	currently not reentrant, so use appropriate locking yourself, always call	83	threads, it is currently not reentrant in any way, so use appropriate
66	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	84	locking yourself, always call C<poll_cb> from within the same thread, or
67	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).
68		180
69	=cut	181	=cut
70		182
71	package IO::AIO;	183	package IO::AIO;
72		184
…		…
74	use strict 'vars';	186	use strict 'vars';
75		187
76	use base 'Exporter';	188	use base 'Exporter';
77		189
78	BEGIN {	190	BEGIN {
79	our $VERSION = '2.0';	191	our $VERSION = '2.1';
80		192
81	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
82	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
83	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
84	aio_group aio_nop);	196	aio_copy aio_group aio_nop aio_mknod);
85	our @EXPORT = (@AIO_REQ, qw(aioreq_pri));	197	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
86	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	198	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
87	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);
88		202
89	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	203	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
90		204
91	require XSLoader;	205	require XSLoader;
92	XSLoader::load ("IO::AIO", $VERSION);	206	XSLoader::load ("IO::AIO", $VERSION);
…		…
123	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)
124	use something else.	238	use something else.
125		239
126	=over 4	240	=over 4
127		241
		242	=item $prev_pri = aioreq_pri [$pri]
		243
		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
		247	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		248	and C<4>, respectively. Requests with higher priority will be serviced
		249	first.
		250
		251	The priority will be reset to C<0> after each call to one of the C<aio_*>
		252	functions.
		253
		254	Example: open a file with low priority, then read something from it with
		255	higher priority so the read request is serviced before other low priority
		256	open requests (potentially spamming the cache):
		257
		258	aioreq_pri -3;
		259	aio_open ..., sub {
		260	return unless $_[0];
		261
		262	aioreq_pri -2;
		263	aio_read $_[0], ..., sub {
		264	...
		265	};
		266	};
		267
		268	=item aioreq_nice $pri_adjust
		269
		270	Similar to C<aioreq_pri>, but subtracts the given value from the current
		271	priority, so effects are cumulative.
		272
128	=item aio_open $pathname, $flags, $mode, $callback->($fh)	273	=item aio_open $pathname, $flags, $mode, $callback->($fh)
129		274
130	Asynchronously open or create a file and call the callback with a newly	275	Asynchronously open or create a file and call the callback with a newly
131	created filehandle for the file.	276	created filehandle for the file.
132		277
…		…
181		326
182	aio_read $fh, 7, 15, $buffer, 0, sub {	327	aio_read $fh, 7, 15, $buffer, 0, sub {
183	$_[0] > 0 or die "read error: $!";	328	$_[0] > 0 or die "read error: $!";
184	print "read $_[0] bytes: <$buffer>\n";	329	print "read $_[0] bytes: <$buffer>\n";
185	};	330	};
186
187	=item aio_move $srcpath, $dstpath, $callback->($status)
188
189	[EXPERIMENTAL due to internal aio_group use]
190
191	Try to move the I<file> (directories not supported as either source or
192	destination) from C<$srcpath> to C<$dstpath> and call the callback with
193	the C<0> (error) or C<-1> ok.
194
195	This is a composite request that tries to rename(2) the file first. If
196	rename files with C<EXDEV>, it creates the destination file with mode 0200
197	and copies the contents of the source file into it using C<aio_sendfile>,
198	followed by restoring atime, mtime, access mode and uid/gid, in that
199	order, and unlinking the C<$srcpath>.
200
201	If an error occurs, the partial destination file will be unlinked, if
202	possible, except when setting atime, mtime, access mode and uid/gid, where
203	errors are being ignored.
204
205	=cut
206
207	sub aio_move($$$) {
208	my ($src, $dst, $cb) = @_;
209
210	my $grp = aio_group $cb;
211
212	add $grp aio_rename $src, $dst, sub {
213	if ($_[0] && $! == EXDEV) {
214	add $grp aio_open $src, O_RDONLY, 0, sub {
215	if (my $src_fh = $_[0]) {
216	my @stat = stat $src_fh;
217
218	add $grp aio_open $dst, O_WRONLY, 0200, sub {
219	if (my $dst_fh = $_[0]) {
220	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
221	close $src_fh;
222
223	if ($_[0] == $stat[7]) {
224	utime $stat[8], $stat[9], $dst;
225	chmod $stat[2] & 07777, $dst_fh;
226	chown $stat[4], $stat[5], $dst_fh;
227	close $dst_fh;
228
229	add $grp aio_unlink $src, sub {
230	$grp->result ($_[0]);
231	};
232	} else {
233	my $errno = $!;
234	add $grp aio_unlink $dst, sub {
235	$! = $errno;
236	$grp->result (-1);
237	};
238	}
239	};
240	} else {
241	$grp->result (-1);
242	}
243	},
244
245	} else {
246	$grp->result (-1);
247	}
248	};
249	} else {
250	$grp->result ($_[0]);
251	}
252	};
253
254	$grp
255	}
256		331
257	=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)
258		333
259	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
260	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
…		…
316	=item aio_unlink $pathname, $callback->($status)	391	=item aio_unlink $pathname, $callback->($status)
317		392
318	Asynchronously unlink (delete) a file and call the callback with the	393	Asynchronously unlink (delete) a file and call the callback with the
319	result code.	394	result code.
320		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
321	=item aio_link $srcpath, $dstpath, $callback->($status)	406	=item aio_link $srcpath, $dstpath, $callback->($status)
322		407
323	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
324	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.
325		410
…		…
345	sorted, and will B<NOT> include the C<.> and C<..> entries.	430	sorted, and will B<NOT> include the C<.> and C<..> entries.
346		431
347	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
348	with the filenames.	433	with the filenames.
349		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
350	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	537	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
351		538
352	[EXPERIMENTAL due to internal aio_group use]
353
354	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
355	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
356	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
357	recurse into (everything else).	542	recurse into (everything else, including symlinks to directories).
358		543
359	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_
360	C<$maxreq> specifies the maximum number of outstanding aio requests that	545	C<$maxreq> specifies the maximum number of outstanding aio requests that
361	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
362	will be chosen (currently 6).	547	will be chosen (currently 4).
363		548
364	On error, the callback is called without arguments, otherwise it receives	549	On error, the callback is called without arguments, otherwise it receives
365	two array-refs with path-relative entry names.	550	two array-refs with path-relative entry names.
366		551
367	Example:	552	Example:
…		…
404	=cut	589	=cut
405		590
406	sub aio_scandir($$$) {	591	sub aio_scandir($$$) {
407	my ($path, $maxreq, $cb) = @_;	592	my ($path, $maxreq, $cb) = @_;
408		593
		594	my $pri = aioreq_pri;
		595
409	my $grp = aio_group $cb;	596	my $grp = aio_group $cb;
410		597
411	$maxreq = 6 if $maxreq <= 0;	598	$maxreq = 4 if $maxreq <= 0;
412		599
413	# stat once	600	# stat once
		601	aioreq_pri $pri;
414	add $grp aio_stat $path, sub {	602	add $grp aio_stat $path, sub {
415	return $grp->result () if $_[0];	603	return $grp->result () if $_[0];
416	my $now = time;	604	my $now = time;
417	my $hash1 = join ":", (stat _)[0,1,3,7,9];	605	my $hash1 = join ":", (stat _)[0,1,3,7,9];
418		606
419	# read the directory entries	607	# read the directory entries
		608	aioreq_pri $pri;
420	add $grp aio_readdir $path, sub {	609	add $grp aio_readdir $path, sub {
421	my $entries = shift	610	my $entries = shift
422	or return $grp->result ();	611	or return $grp->result ();
423		612
424	# stat the dir another time	613	# stat the dir another time
		614	aioreq_pri $pri;
425	add $grp aio_stat $path, sub {	615	add $grp aio_stat $path, sub {
426	my $hash2 = join ":", (stat _)[0,1,3,7,9];	616	my $hash2 = join ":", (stat _)[0,1,3,7,9];
427		617
428	my $ndirs;	618	my $ndirs;
429		619
…		…
444	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	634	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
445	@$entries];	635	@$entries];
446		636
447	my (@dirs, @nondirs);	637	my (@dirs, @nondirs);
448		638
449	my ($statcb, $schedcb);
450	my $nreq = 0;
451
452	my $statgrp = add $grp aio_group;	639	my $statgrp = add $grp aio_group sub {
		640	$grp->result (\@dirs, \@nondirs);
		641	};
453		642
454	$schedcb = sub {	643	limit $statgrp $maxreq;
455	if (@$entries) {	644	feed $statgrp sub {
456	if ($nreq < $maxreq) {	645	return unless @$entries;
457	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	}
458	$nreq++;	666	}
459	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
460	}	667	}
461	} elsif (!$nreq) {
462	# finished
463	$statgrp->cancel;
464	undef $statcb;
465	undef $schedcb;
466	$grp->result (\@dirs, \@nondirs);
467	}	668	};
468	};	669	};
469	$statcb = sub {
470	my ($status, $entry) = @_;
471
472	if ($status < 0) {
473	$nreq--;
474	push @nondirs, $entry;
475	&$schedcb;
476	} else {
477	# need to check for real directory
478	add $grp aio_lstat "$path/$entry", sub {
479	$nreq--;
480
481	if (-d _) {
482	push @dirs, $entry;
483
484	if (!--$ndirs) {
485	push @nondirs, @$entries;
486	$entries = [];
487	}
488	} else {
489	push @nondirs, $entry;
490	}
491
492	&$schedcb;
493	}
494	}
495	};
496
497	&$schedcb while @$entries && $nreq < $maxreq;
498	};	670	};
499	};	671	};
500	};	672	};
501		673
502	$grp	674	$grp
…		…
515	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
516	detected, it will be emulated by calling C<fsync> instead.	688	detected, it will be emulated by calling C<fsync> instead.
517		689
518	=item aio_group $callback->(...)	690	=item aio_group $callback->(...)
519		691
520	[EXPERIMENTAL]
521
522	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
523	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
524	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.
525		696
526	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
527	for more info.	698	for more info.
528		699
529	Example:	700	Example:
…		…
548	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
549	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
550	entered their execution phase. This can be used to measure request	721	entered their execution phase. This can be used to measure request
551	latency.	722	latency.
552		723
553	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED	724	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
554		725
555	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
556	the request workers to sleep for the given time.	727	the request workers to sleep for the given time.
557		728
558	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
559	like sleep and file handle readable/writable, the overhead this creates	730	like sleep and file handle readable/writable, the overhead this creates is
560	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
561	under artificial I/O pressure.	732	except to put your application under artificial I/O pressure.
562		733
563	=back	734	=back
564		735
565	=head2 IO::AIO::REQ CLASS	736	=head2 IO::AIO::REQ CLASS
566		737
567	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
568	called in non-void context.	739	called in non-void context.
569
570	A request always moves through the following five states in its lifetime,
571	in order: B<ready> (request has been created, but has not been executed
572	yet), B<execute> (request is currently being executed), B<pending>
573	(request has been executed but callback has not been called yet),
574	B<result> (results are being processed synchronously, includes calling the
575	callback) and B<done> (request has reached the end of its lifetime and
576	holds no resources anymore).
577		740
578	=over 4	741	=over 4
579		742
580	=item cancel $req	743	=item cancel $req
581		744
…		…
635	=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.
636		799
637	=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
638	any later time).	801	any later time).
639		802
640	=item * This does not harmonise well with C<max_outstanding>, so best do
641	not combine C<aio_group> with it. Groups and feeders are recommended for
642	this kind of concurrency-limiting.
643
644	=back	803	=back
645		804
646	Their lifetime, simplified, looks like this: when they are empty, they	805	Their lifetime, simplified, looks like this: when they are empty, they
647	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
648	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
…		…
663	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
664	dependencies.	823	dependencies.
665		824
666	Returns all its arguments.	825	Returns all its arguments.
667		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
668	=item $grp->result (...)	832	=item $grp->result (...)
669		833
670	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
671	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.
672		850
673	=item feed $grp $callback->($grp)	851	=item feed $grp $callback->($grp)
674
675	[VERY EXPERIMENTAL]
676		852
677	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
678	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,
679	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,
680	this might starve other requests for a potentially long time. For	856	this might starve other requests for a potentially long time. For
681	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	857	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
682	requests, delaying any later requests for a long time.	858	requests, delaying any later requests for a long time.
683		859
684	To avoid this, and allow incremental generation of requests, you can	860	To avoid this, and allow incremental generation of requests, you can
685	instead a group and set a feeder on it that generates those requests. The	861	instead a group and set a feeder on it that generates those requests. The
686	feed callback will be called whenever there are few enough (see C<feed_limit>,	862	feed callback will be called whenever there are few enough (see C<limit>,
687	below) requests active in the group itself and is expected to queue more	863	below) requests active in the group itself and is expected to queue more
688	requests.	864	requests.
689		865
690	The feed can queue as many requests as it likes (i.e. C<add> does not	866	The feed callback can queue as many requests as it likes (i.e. C<add> does
691	impose any limits).	867	not impose any limits).
692		868
693	If the feed does not queue more requests when called, it will be	869	If the feed does not queue more requests when called, it will be
694	automatically removed from the group.	870	automatically removed from the group.
695		871
696	If the feed limit is C<0>, it will be set to C<2> automatically.	872	If the feed limit is C<0>, it will be set to C<2> automatically.
…		…
698	Example:	874	Example:
699		875
700	# stat all files in @files, but only ever use four aio requests concurrently:	876	# stat all files in @files, but only ever use four aio requests concurrently:
701		877
702	my $grp = aio_group sub { print "finished\n" };	878	my $grp = aio_group sub { print "finished\n" };
703	feed_limit $grp 4;	879	limit $grp 4;
704	feed $grp sub {	880	feed $grp sub {
705	my $file = pop @files	881	my $file = pop @files
706	or return;	882	or return;
707		883
708	add $grp aio_stat $file, sub { ... };	884	add $grp aio_stat $file, sub { ... };
709	};	885	};
710		886
711	=item feed_limit $grp $num	887	=item limit $grp $num
712		888
713	Sets the feeder limit for the group: The feeder will be called whenever	889	Sets the feeder limit for the group: The feeder will be called whenever
714	the group contains less than this many requests.	890	the group contains less than this many requests.
715		891
716	Setting the limit to C<0> will pause the feeding process.	892	Setting the limit to C<0> will pause the feeding process.
717		893
718	=back	894	=back
719		895
720	=head2 SUPPORT FUNCTIONS	896	=head2 SUPPORT FUNCTIONS
		897
		898	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
721		899
722	=over 4	900	=over 4
723		901
724	=item $fileno = IO::AIO::poll_fileno	902	=item $fileno = IO::AIO::poll_fileno
725		903
…		…
730		908
731	See C<poll_cb> for an example.	909	See C<poll_cb> for an example.
732		910
733	=item IO::AIO::poll_cb	911	=item IO::AIO::poll_cb
734		912
735	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
736	regularly. Returns the number of events processed. Returns immediately	914	regularly. Returns the number of events processed. Returns immediately
737	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.
738		920
739	Example: Install an Event watcher that automatically calls	921	Example: Install an Event watcher that automatically calls
740	IO::AIO::poll_cb with high priority:	922	IO::AIO::poll_cb with high priority:
741		923
742	Event->io (fd => IO::AIO::poll_fileno,	924	Event->io (fd => IO::AIO::poll_fileno,
743	poll => 'r', async => 1,	925	poll => 'r', async => 1,
744	cb => \&IO::AIO::poll_cb);	926	cb => \&IO::AIO::poll_cb);
745		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
746	=item IO::AIO::poll_wait	956	=item IO::AIO::poll_wait
747		957
748	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
749	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
750	for some requests to finish).	960	wait for some requests to finish).
751		961
752	See C<nreqs> for an example.	962	See C<nreqs> for an example.
753		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
754	=item IO::AIO::nreqs	973	=item IO::AIO::flush
755		974
756	Returns the number of requests currently outstanding (i.e. for which their	975	Wait till all outstanding AIO requests have been handled.
757	callback has not been invoked yet).
758		976
759	Example: wait till there are no outstanding requests anymore:	977	Strictly equivalent to:
760		978
761	IO::AIO::poll_wait, IO::AIO::poll_cb	979	IO::AIO::poll_wait, IO::AIO::poll_cb
762	while IO::AIO::nreqs;	980	while IO::AIO::nreqs;
763		981
764	=item IO::AIO::flush	982	=head3 CONTROLLING THE NUMBER OF THREADS
765
766	Wait till all outstanding AIO requests have been handled.
767
768	Strictly equivalent to:
769
770	IO::AIO::poll_wait, IO::AIO::poll_cb
771	while IO::AIO::nreqs;
772
773	=item IO::AIO::poll
774
775	Waits until some requests have been handled.
776
777	Strictly equivalent to:
778
779	IO::AIO::poll_wait, IO::AIO::poll_cb
780	if IO::AIO::nreqs;
781		983
782	=item IO::AIO::min_parallel $nthreads	984	=item IO::AIO::min_parallel $nthreads
783		985
784	Set the minimum number of AIO threads to C<$nthreads>. The current	986	Set the minimum number of AIO threads to C<$nthreads>. The current
785	default is C<8>, which means eight asynchronous operations can execute	987	default is C<8>, which means eight asynchronous operations can execute
786	concurrently at any one time (the number of outstanding requests,	988	concurrently at any one time (the number of outstanding requests,
787	however, is unlimited).	989	however, is unlimited).
788		990
789	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
790	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.
791		995
792	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
793	Linux kernel versions will scale negatively with the number of threads	997	Linux kernel versions will scale negatively with the number of threads
794	(higher parallelity => MUCH higher latency). With current Linux 2.6	998	(higher parallelity => MUCH higher latency). With current Linux 2.6
795	versions, 4-32 threads should be fine.	999	versions, 4-32 threads should be fine.
…		…
809	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
810	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.
811		1015
812	Under normal circumstances you don't need to call this function.	1016	Under normal circumstances you don't need to call this function.
813		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
814	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1033	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
815		1034
816	[DEPRECATED]	1035	This is a very bad function to use in interactive programs because it
		1036	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1037	use an C<aio_group> together with a feed callback.
817		1038
818	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1039	Sets the maximum number of outstanding requests to C<$nreqs>. If you
819	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
820	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.
821		1043
822	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
823	queue up many requests in a loop it often improves speed if you set	1045	number of outstanding requests.
824	this to a relatively low number, such as C<100>.
825		1046
826	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,
827	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
828	this function.	1049	as a stop gap to shield against fatal memory overflow (with large values).
829		1050
830	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).
831		1072
832	=back	1073	=back
833		1074
834	=cut	1075	=cut
835		1076
…		…
850	}	1091	}
851		1092
852	min_parallel 8;	1093	min_parallel 8;
853		1094
854	END {	1095	END {
855	max_parallel 0;	1096	min_parallel 1;
856	}	1097	flush;
		1098	};
857		1099
858	1;	1100	1;
859		1101
860	=head2 FORK BEHAVIOUR	1102	=head2 FORK BEHAVIOUR
861		1103
862	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:
863		1105
864	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
865	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
866	the fork the parent simply leaves the quiescent state and continues	1108	the fork the parent simply leaves the quiescent state and continues
867	request/result processing, while the child clears the request/result	1109	request/result processing, while the child frees the request/result queue
868	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
869	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
870	parent process has been reached again.	1112	parent process has been reached again.
871		1113
872	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
873	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
874	yet.	1116	yet.
875		1117
876	=head2 MEMORY USAGE	1118	=head2 MEMORY USAGE
877		1119
		1120	Per-request usage:
		1121
878	Each aio request uses - depending on your architecture - around 128 bytes	1122	Each aio request uses - depending on your architecture - around 100-200
879	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
880	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
881	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.
882		1127
883	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
884	problem.	1129	problem.
885		1130
886	Each thread needs a stack area which is usually around 16k, sometimes much	1131	Per-thread usage:
887	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.
888		1140
889	=head1 SEE ALSO	1141	=head1 SEE ALSO
890		1142
891	L<Coro>, L<Linux::AIO> (obsolete).	1143	L<Coro::AIO>.
892		1144
893	=head1 AUTHOR	1145	=head1 AUTHOR
894		1146
895	Marc Lehmann <schmorp@schmorp.de>	1147	Marc Lehmann <schmorp@schmorp.de>
896	http://home.schmorp.de/	1148	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.67 by root, Tue Oct 24 02:25:16 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 1.67 by root, Tue Oct 24 02:25:16 2006 UTC vs.
Revision 1.86 by root, Sat Oct 28 23:32:29 2006 UTC