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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.61 by root, Fri Apr 25 01:55:25 2008 UTC vs.
Revision 1.73 by root, Fri Apr 25 07:47:12 2008 UTC

…		…
369		369
370	There is no support for WxWidgets, as WxWidgets has no support for	370	There is no support for WxWidgets, as WxWidgets has no support for
371	watching file handles. However, you can use WxWidgets through the	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	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	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	374	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
375	it's adaptor.	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.
376		379
377	=item AnyEvent::detect	380	=item AnyEvent::detect
378		381
379	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
380	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
…		…
431	no warnings;	434	no warnings;
432	use strict;	435	use strict;
433		436
434	use Carp;	437	use Carp;
435		438
436	our $VERSION = '3.2';	439	our $VERSION = '3.3';
437	our $MODEL;	440	our $MODEL;
438		441
439	our $AUTOLOAD;	442	our $AUTOLOAD;
440	our @ISA;	443	our @ISA;
441		444
…		…
448	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],	451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
449	[EV:: => AnyEvent::Impl::EV::],	452	[EV:: => AnyEvent::Impl::EV::],
450	[Event:: => AnyEvent::Impl::Event::],	453	[Event:: => AnyEvent::Impl::Event::],
451	[Glib:: => AnyEvent::Impl::Glib::],	454	[Glib:: => AnyEvent::Impl::Glib::],
452	[Tk:: => AnyEvent::Impl::Tk::],	455	[Tk:: => AnyEvent::Impl::Tk::],
		456	[Wx:: => AnyEvent::Impl::POE::],
		457	[Prima:: => AnyEvent::Impl::POE::],
453	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
454	# everything below here will not be autoprobed as the pureperl backend should work everywhere	459	# everything below here will not be autoprobed as the pureperl backend should work everywhere
455	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
456	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
457	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
…		…
855	$quit->broadcast;	860	$quit->broadcast;
856	});	861	});
857		862
858	$quit->wait;	863	$quit->wait;
859		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, but it features a
		941	faster callback invocation and overall ends up in the same class as
		942	C<Event>. However, Glib scales extremely badly, doubling the number of
		943	watchers increases the processing time by more than a factor of four,
		944	making it completely unusable when using larger numbers of watchers
		945	(note that only a single file descriptor was used in the benchmark, so
		946	inefficiencies of C<poll> do not account for this).
		947
		948	The C<Tk> adaptor works relatively well. The fact that it crashes with
		949	more than 2000 watchers is a big setback, however, as correctness takes
		950	precedence over speed. Nevertheless, its performance is surprising, as the
		951	file descriptor is dup()ed for each watcher. This shows that the dup()
		952	employed by some adaptors is not a big performance issue (it does incur a
		953	hidden memory cost inside the kernel, though).
		954
		955	C<POE>, regardless of underlying event loop (wether using its pure perl
		956	select-based backend or the Event module) shows abysmal performance and
		957	memory usage: Watchers use almost 30 times as much memory as EV watchers,
		958	and 10 times as much memory as both Event or EV via AnyEvent. Watcher
		959	invocation is almost 700 times slower than with AnyEvent's pure perl
		960	implementation. The design of the POE adaptor class in AnyEvent can not
		961	really account for this, as session creation overhead is small compared
		962	to execution of the state machine, which is coded pretty optimally within
		963	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		964
		965	=head2 Summary
		966
		967	Using EV through AnyEvent is faster than any other event loop, but most
		968	event loops have acceptable performance with or without AnyEvent.
		969
		970	The overhead AnyEvent adds is usually much smaller than the overhead of
		971	the actual event loop, only with extremely fast event loops such as the EV
		972	adds AnyEvent significant overhead.
		973
		974	And you should simply avoid POE like the plague if you want performance or
		975	reasonable memory usage.
		976
		977
860	=head1 FORK	978	=head1 FORK
861		979
862	Most event libraries are not fork-safe. The ones who are usually are	980	Most event libraries are not fork-safe. The ones who are usually are
863	because they are so inefficient. Only L<EV> is fully fork-aware.	981	because they are so inefficient. Only L<EV> is fully fork-aware.
864		982
865	If you have to fork, you must either do so I<before> creating your first	983	If you have to fork, you must either do so I<before> creating your first
866	watcher OR you must not use AnyEvent at all in the child.	984	watcher OR you must not use AnyEvent at all in the child.
		985
867		986
868	=head1 SECURITY CONSIDERATIONS	987	=head1 SECURITY CONSIDERATIONS
869		988
870	AnyEvent can be forced to load any event model via	989	AnyEvent can be forced to load any event model via
871	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	990	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
879		998
880	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	999	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
881		1000
882	use AnyEvent;	1001	use AnyEvent;
883		1002
		1003
884	=head1 SEE ALSO	1004	=head1 SEE ALSO
885		1005
886	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1006	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
887	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1007	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
888	L<Event::Lib>, L<Qt>, L<POE>.	1008	L<Event::Lib>, L<Qt>, L<POE>.
…		…
892	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1012	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
893	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1013	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
894		1014
895	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1015	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
896		1016
		1017
897	=head1 AUTHOR	1018	=head1 AUTHOR
898		1019
899	Marc Lehmann <schmorp@schmorp.de>	1020	Marc Lehmann <schmorp@schmorp.de>
900	http://home.schmorp.de/	1021	http://home.schmorp.de/
901		1022

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.61 by root, Fri Apr 25 01:55:25 2008 UTC vs. Revision 1.73 by root, Fri Apr 25 07:47:12 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.61 by root, Fri Apr 25 01:55:25 2008 UTC vs.
Revision 1.73 by root, Fri Apr 25 07:47:12 2008 UTC