[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 1.78 by root, Fri Apr 25 09:06:27 2008 UTC

…		…
136		136
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	137	Note that C<my $w; $w => combination. This is necessary because in Perl,
138	my variables are only visible after the statement in which they are	138	my variables are only visible after the statement in which they are
139	declared.	139	declared.
140		140
141	=head2 IO WATCHERS	141	=head2 I/O WATCHERS
142		142
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	144	with the following mandatory key-value pairs as arguments:
145		145
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for
…		…
369		369
370	There is no support for WxWidgets, as WxWidgets has no support for	370	There is no support for WxWidgets, as WxWidgets has no support for
371	watching file handles. However, you can use WxWidgets through the	371	watching file handles. However, you can use WxWidgets through the
372	POE Adaptor, as POE has a Wx backend that simply polls 20 times per	372	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
373	second, which was considered to be too horrible to even consider for	373	second, which was considered to be too horrible to even consider for
374	AnyEvent. Likewise, other POE backends can be used by Anyevent by using	374	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
375	it's adaptor.	375	it's adaptor.
		376
		377	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		378	autodetecting them.
376		379
377	=item AnyEvent::detect	380	=item AnyEvent::detect
378		381
379	Returns C<$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
…		…
701		706
702	=back	707	=back
703		708
704	=head1 EXAMPLE PROGRAM	709	=head1 EXAMPLE PROGRAM
705		710
706	The following program uses an IO watcher to read data from STDIN, a timer	711	The following program uses an I/O watcher to read data from STDIN, a timer
707	to display a message once per second, and a condition variable to quit the	712	to display a message once per second, and a condition variable to quit the
708	program when the user enters quit:	713	program when the user enters quit:
709		714
710	use AnyEvent;	715	use AnyEvent;
711		716
…		…
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 I/O watchers (watching STDOUT, a pty, to
		873	become writable, which it is), lets them fire exactly once and destroys
		874	them again.
		875
		876	Rewriting the benchmark to use many different sockets instead of using
		877	the same filehandle for all I/O watchers results in a much longer runtime
		878	(socket creation is expensive), but qualitatively the same figures, so it
		879	was not used.
		880
		881	=head2 Explanation of the columns
		882
		883	I<watcher> is the number of event watchers created/destroyed. Since
		884	different event models feature vastly different performances, each event
		885	loop was given a number of watchers so that overall runtime is acceptable
		886	and similar between tested event loop (and keep them from crashing): Glib
		887	would probably take thousands of years if asked to process the same number
		888	of watchers as EV in this benchmark.
		889
		890	I<bytes> is the number of bytes (as measured by the resident set size,
		891	RSS) consumed by each watcher. This method of measuring captures both C
		892	and Perl-based overheads.
		893
		894	I<create> is the time, in microseconds (millionths of seconds), that it
		895	takes to create a single watcher. The callback is a closure shared between
		896	all watchers, to avoid adding memory overhead. That means closure creation
		897	and memory usage is not included in the figures.
		898
		899	I<invoke> is the time, in microseconds, used to invoke a simple
		900	callback. The callback simply counts down a Perl variable and after it was
		901	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		902	signal the end of this phase.
		903
		904	I<destroy> is the time, in microseconds, that it takes to destroy a single
		905	watcher.
		906
		907	=head2 Results
		908
		909	name watchers bytes create invoke destroy comment
		910	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		911	EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers
		912	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal
		913	Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation
		914	Event/Event 16000 523 28.05 21.38 0.86 Event native interface
		915	Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers
		916	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour
		917	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers
		918	POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event
		919	POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select
		920
		921	=head2 Discussion
		922
		923	The benchmark does I<not> measure scalability of the event loop very
		924	well. For example, a select-based event loop (such as the pure perl one)
		925	can never compete with an event loop that uses epoll when the number of
		926	file descriptors grows high. In this benchmark, only a single filehandle
		927	is used (although some of the AnyEvent adaptors dup() its file descriptor
		928	to worka round bugs).
		929
		930	C<EV> is the sole leader regarding speed and memory use, which are both
		931	maximal/minimal, respectively. Even when going through AnyEvent, there are
		932	only two event loops that use slightly less memory (the C<Event> module
		933	natively and the pure perl backend), and no faster event models, not even
		934	C<Event> natively.
		935
		936	The pure perl implementation is hit in a few sweet spots (both the
		937	zero timeout and the use of a single fd hit optimisations in the perl
		938	interpreter and the backend itself, and all watchers become ready at the
		939	same time). Nevertheless this shows that it adds very little overhead in
		940	itself. Like any select-based backend its performance becomes really bad
		941	with lots of file descriptors (and few of them active), of course, but
		942	this was not subject of this benchmark.
		943
		944	The C<Event> module has a relatively high setup and callback invocation cost,
		945	but overall scores on the third place.
		946
		947	C<Glib>'s memory usage is quite a bit bit higher, but it features a
		948	faster callback invocation and overall ends up in the same class as
		949	C<Event>. However, Glib scales extremely badly, doubling the number of
		950	watchers increases the processing time by more than a factor of four,
		951	making it completely unusable when using larger numbers of watchers
		952	(note that only a single file descriptor was used in the benchmark, so
		953	inefficiencies of C<poll> do not account for this).
		954
		955	The C<Tk> adaptor works relatively well. The fact that it crashes with
		956	more than 2000 watchers is a big setback, however, as correctness takes
		957	precedence over speed. Nevertheless, its performance is surprising, as the
		958	file descriptor is dup()ed for each watcher. This shows that the dup()
		959	employed by some adaptors is not a big performance issue (it does incur a
		960	hidden memory cost inside the kernel, though, that is not reflected in the
		961	figures above).
		962
		963	C<POE>, regardless of underlying event loop (wether using its pure perl
		964	select-based backend or the Event module) shows abysmal performance and
		965	memory usage: Watchers use almost 30 times as much memory as EV watchers,
		966	and 10 times as much memory as both Event or EV via AnyEvent. Watcher
		967	invocation is almost 700 times slower than with AnyEvent's pure perl
		968	implementation. The design of the POE adaptor class in AnyEvent can not
		969	really account for this, as session creation overhead is small compared
		970	to execution of the state machine, which is coded pretty optimally within
		971	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		972
		973	=head2 Summary
		974
		975	Using EV through AnyEvent is faster than any other event loop, but most
		976	event loops have acceptable performance with or without AnyEvent.
		977
		978	The overhead AnyEvent adds is usually much smaller than the overhead of
		979	the actual event loop, only with extremely fast event loops such as the EV
		980	adds AnyEvent significant overhead.
		981
		982	And you should simply avoid POE like the plague if you want performance or
		983	reasonable memory usage.
		984
		985
860	=head1 FORK	986	=head1 FORK
861		987
862	Most event libraries are not fork-safe. The ones who are usually are	988	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.	989	because they are so inefficient. Only L<EV> is fully fork-aware.
864		990
865	If you have to fork, you must either do so I<before> creating your first	991	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.	992	watcher OR you must not use AnyEvent at all in the child.
		993
867		994
868	=head1 SECURITY CONSIDERATIONS	995	=head1 SECURITY CONSIDERATIONS
869		996
870	AnyEvent can be forced to load any event model via	997	AnyEvent can be forced to load any event model via
871	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	998	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
879		1006
880	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1007	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
881		1008
882	use AnyEvent;	1009	use AnyEvent;
883		1010
		1011
884	=head1 SEE ALSO	1012	=head1 SEE ALSO
885		1013
886	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1014	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>,	1015	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
888	L<Event::Lib>, L<Qt>, L<POE>.	1016	L<Event::Lib>, L<Qt>, L<POE>.
…		…
892	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1020	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
893	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1021	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
894		1022
895	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1023	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
896		1024
		1025
897	=head1 AUTHOR	1026	=head1 AUTHOR
898		1027
899	Marc Lehmann <schmorp@schmorp.de>	1028	Marc Lehmann <schmorp@schmorp.de>
900	http://home.schmorp.de/	1029	http://home.schmorp.de/
901		1030

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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 1.78 by root, Fri Apr 25 09:06:27 2008 UTC

Diff Legend

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.61 by root, Fri Apr 25 01:55:25 2008 UTC vs.
Revision 1.78 by root, Fri Apr 25 09:06:27 2008 UTC