[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.59 by root, Thu Apr 24 08:38:13 2008 UTC vs.
Revision 1.72 by root, Fri Apr 25 07:43:25 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt - various supported event loops	5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6		6
7	=head1 SYNOPSIS	7	=head1 SYNOPSIS
8		8
9	use AnyEvent;	9	use AnyEvent;
10		10
78		78
79	The interface itself is vaguely similar, but not identical to the L<Event>	79	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	80	module.
81		81
82	During the first call of any watcher-creation method, the module tries	82	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of	83	to detect the currently loaded event loop by probing whether one of the
84	the following modules is already loaded: L<Coro::EV>, L<Coro::Event>,	84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
85	L<EV>, L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>. The first one	85	L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,
86	found is used. If none are found, the module tries to load these modules	86	L<POE>. The first one found is used. If none are found, the module tries
87	(excluding Event::Lib and Qt) in the order given. The first one that can	87	to load these modules (excluding Event::Lib, Qt and POE as the pure perl
		88	adaptor should always succeed) in the order given. The first one that can
88	be successfully loaded will be used. If, after this, still none could be	89	be successfully loaded will be used. If, after this, still none could be
89	found, AnyEvent will fall back to a pure-perl event loop, which is not	90	found, AnyEvent will fall back to a pure-perl event loop, which is not
90	very efficient, but should work everywhere.	91	very efficient, but should work everywhere.
91		92
92	Because AnyEvent first checks for modules that are already loaded, loading	93	Because AnyEvent first checks for modules that are already loaded, loading
…		…
362	AnyEvent::Impl::Glib based on Glib, third-best choice.	363	AnyEvent::Impl::Glib based on Glib, third-best choice.
363	AnyEvent::Impl::Tk based on Tk, very bad choice.	364	AnyEvent::Impl::Tk based on Tk, very bad choice.
364	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.	365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
365	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
366	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		368	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		369
		370	There is no support for WxWidgets, as WxWidgets has no support for
		371	watching file handles. However, you can use WxWidgets through the
		372	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		373	second, which was considered to be too horrible to even consider for
		374	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		375	it's adaptor.
		376
		377	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		378	autodetecting them.
367		379
368	=item AnyEvent::detect	380	=item AnyEvent::detect
369		381
370	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
371	if necessary. You should only call this function right before you would	383	if necessary. You should only call this function right before you would
…		…
422	no warnings;	434	no warnings;
423	use strict;	435	use strict;
424		436
425	use Carp;	437	use Carp;
426		438
427	our $VERSION = '3.2';	439	our $VERSION = '3.3';
428	our $MODEL;	440	our $MODEL;
429		441
430	our $AUTOLOAD;	442	our $AUTOLOAD;
431	our @ISA;	443	our @ISA;
432		444
…		…
439	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],	451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
440	[EV:: => AnyEvent::Impl::EV::],	452	[EV:: => AnyEvent::Impl::EV::],
441	[Event:: => AnyEvent::Impl::Event::],	453	[Event:: => AnyEvent::Impl::Event::],
442	[Glib:: => AnyEvent::Impl::Glib::],	454	[Glib:: => AnyEvent::Impl::Glib::],
443	[Tk:: => AnyEvent::Impl::Tk::],	455	[Tk:: => AnyEvent::Impl::Tk::],
		456	[Wx:: => AnyEvent::Impl::POE::],
		457	[Prima:: => AnyEvent::Impl::POE::],
444	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
445	);	459	# everything below here will not be autoprobed as the pureperl backend should work everywhere
446	my @models_detect = (	460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
447	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
448	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
449	);	463	);
450		464
451	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	465	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
452		466
453	sub detect() {	467	sub detect() {
…		…
457	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	471	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
458	my $model = "AnyEvent::Impl::$1";	472	my $model = "AnyEvent::Impl::$1";
459	if (eval "require $model") {	473	if (eval "require $model") {
460	$MODEL = $model;	474	$MODEL = $model;
461	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	475	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		476	} else {
		477	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
462	}	478	}
463	}	479	}
464		480
465	# check for already loaded models	481	# check for already loaded models
466	unless ($MODEL) {	482	unless ($MODEL) {
467	for (@REGISTRY, @models, @models_detect) {	483	for (@REGISTRY, @models) {
468	my ($package, $model) = @$_;	484	my ($package, $model) = @$_;
469	if (${"$package\::VERSION"} > 0) {	485	if (${"$package\::VERSION"} > 0) {
470	if (eval "require $model") {	486	if (eval "require $model") {
471	$MODEL = $model;	487	$MODEL = $model;
472	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	488	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
…		…
659		675
660	=over 4	676	=over 4
661		677
662	=item C<PERL_ANYEVENT_VERBOSE>	678	=item C<PERL_ANYEVENT_VERBOSE>
663		679
		680	By default, AnyEvent will be completely silent except in fatal
		681	conditions. You can set this environment variable to make AnyEvent more
		682	talkative.
		683
		684	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		685	conditions, such as not being able to load the event model specified by
		686	C<PERL_ANYEVENT_MODEL>.
		687
664	When set to C<2> or higher, cause AnyEvent to report to STDERR which event	688	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
665	model it chooses.	689	model it chooses.
666		690
667	=item C<PERL_ANYEVENT_MODEL>	691	=item C<PERL_ANYEVENT_MODEL>
668		692
…		…
836	$quit->broadcast;	860	$quit->broadcast;
837	});	861	});
838		862
839	$quit->wait;	863	$quit->wait;
840		864
		865
		866	=head1 BENCHMARK
		867
		868	To give you an idea of the performance and overheads that AnyEvent adds
		869	over the event loops themselves (and to give you an impression of the
		870	speed of various event loops), here is a benchmark of various supported
		871	event models natively and with anyevent. The benchmark creates a lot of
		872	timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to
		873	become writable, which it is), lets them fire exactly once and destroys
		874	them again.
		875
		876	=head2 Explanation of the columns
		877
		878	I<watcher> is the number of event watchers created/destroyed. Since
		879	different event models feature vastly different performances, each event
		880	loop was given a number of watchers so that overall runtime is acceptable
		881	and similar between tested event loop (and keep them from crashing): Glib
		882	would probably take thousands of years if asked to process the same number
		883	of watchers as EV in this benchmark.
		884
		885	I<bytes> is the number of bytes (as measured by the resident set size,
		886	RSS) consumed by each watcher. This method of measuring captures both C
		887	and Perl-based overheads.
		888
		889	I<create> is the time, in microseconds (millionths of seconds), that it
		890	takes to create a single watcher. The callback is a closure shared between
		891	all watchers, to avoid adding memory overhead. That means closure creation
		892	and memory usage is not included in the figures.
		893
		894	I<invoke> is the time, in microseconds, used to invoke a simple
		895	callback. The callback simply counts down a Perl variable and after it was
		896	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		897	signal the end of this phase.
		898
		899	I<destroy> is the time, in microseconds, that it takes to destroy a single
		900	watcher.
		901
		902	=head2 Results
		903
		904	name watcher bytes create invoke destroy comment
		905	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		906	EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers
		907	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal
		908	Perl/Any 16000 654 4.64 1.22 0.77 pure perl implementation
		909	Event/Event 16000 523 28.05 21.38 0.86 Event native interface
		910	Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers
		911	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour
		912	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers
		913	POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event
		914	POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select
		915
		916	=head2 Discussion
		917
		918	The benchmark does I<not> measure scalability of the event loop very
		919	well. For example, a select-based event loop (such as the pure perl one)
		920	can never compete with an event loop that uses epoll when the number of
		921	file descriptors grows high. In this benchmark, only a single filehandle
		922	is used (although some of the AnyEvent adaptors dup() its file descriptor
		923	to worka round bugs).
		924
		925	C<EV> is the sole leader regarding speed and memory use, which are both
		926	maximal/minimal, respectively. Even when going through AnyEvent, there is
		927	only one event loop that uses less memory (the C<Event> module natively), and
		928	no faster event model, not event C<Event> natively.
		929
		930	The pure perl implementation is hit in a few sweet spots (both the
		931	zero timeout and the use of a single fd hit optimisations in the perl
		932	interpreter and the backend itself). Nevertheless tis shows that it
		933	adds very little overhead in itself. Like any select-based backend its
		934	performance becomes really bad with lots of file descriptors, of course,
		935	but this was not subjetc of this benchmark.
		936
		937	The C<Event> module has a relatively high setup and callback invocation cost,
		938	but overall scores on the third place.
		939
		940	C<Glib>'s memory usage is quite a bit bit higher, features a faster
		941	callback invocation and overall lands in the same class as C<Event>.
		942
		943	The C<Tk> adaptor works relatively well, the fact that it crashes with
		944	more than 2000 watchers is a big setback, however, as correctness takes
		945	precedence over speed. Nevertheless, its performance is surprising, as the
		946	file descriptor is dup()ed for each watcher. This shows that the dup()
		947	employed by some adaptors is not a big performance issue (it does incur a
		948	hidden memory cost inside the kernel, though).
		949
		950	C<POE>, regardless of underlying event loop (wether using its pure perl
		951	select-based backend or the Event module) shows abysmal performance and
		952	memory usage: Watchers use almost 30 times as much memory as EV watchers,
		953	and 10 times as much memory as both Event or EV via AnyEvent. Watcher
		954	invocation is almost 700 times slower than with AnyEvent's pure perl
		955	implementation. The design of the POE adaptor class in AnyEvent can not
		956	really account for this, as session creation overhead is small compared
		957	to execution of the state machine, which is coded pretty optimally within
		958	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		959
		960	=head2 Summary
		961
		962	Using EV through AnyEvent is faster than any other event loop, but most
		963	event loops have acceptable performance with or without AnyEvent.
		964
		965	The overhead AnyEvent adds is usually much smaller than the overhead of
		966	the actual event loop, only with extremely fast event loops such as the EV
		967	adds Anyevent significant overhead.
		968
		969	And you should simply avoid POE like the plague if you want performance or
		970	reasonable memory usage.
		971
		972
841	=head1 FORK	973	=head1 FORK
842		974
843	Most event libraries are not fork-safe. The ones who are usually are	975	Most event libraries are not fork-safe. The ones who are usually are
844	because they are so inefficient. Only L<EV> is fully fork-aware.	976	because they are so inefficient. Only L<EV> is fully fork-aware.
845		977
846	If you have to fork, you must either do so I<before> creating your first	978	If you have to fork, you must either do so I<before> creating your first
847	watcher OR you must not use AnyEvent at all in the child.	979	watcher OR you must not use AnyEvent at all in the child.
		980
848		981
849	=head1 SECURITY CONSIDERATIONS	982	=head1 SECURITY CONSIDERATIONS
850		983
851	AnyEvent can be forced to load any event model via	984	AnyEvent can be forced to load any event model via
852	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	985	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
860		993
861	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	994	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
862		995
863	use AnyEvent;	996	use AnyEvent;
864		997
		998
865	=head1 SEE ALSO	999	=head1 SEE ALSO
866		1000
867	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1001	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
868	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1002	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
869	L<Event::Lib>, L<Qt>.	1003	L<Event::Lib>, L<Qt>, L<POE>.
870		1004
871	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1005	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
872	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1006	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
873	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1007	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
874	L<AnyEvent::Impl::Qt>.	1008	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
875		1009
876	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1010	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		1011
877		1012
878	=head1 AUTHOR	1013	=head1 AUTHOR
879		1014
880	Marc Lehmann <schmorp@schmorp.de>	1015	Marc Lehmann <schmorp@schmorp.de>
881	http://home.schmorp.de/	1016	http://home.schmorp.de/

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.59 by root, Thu Apr 24 08:38:13 2008 UTC vs. Revision 1.72 by root, Fri Apr 25 07:43:25 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.59 by root, Thu Apr 24 08:38:13 2008 UTC vs.
Revision 1.72 by root, Fri Apr 25 07:43:25 2008 UTC