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Revision 1.61 by root, Fri Apr 25 01:55:25 2008 UTC vs.
Revision 1.71 by root, Fri Apr 25 07:29:42 2008 UTC

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369 369
370There is no support for WxWidgets, as WxWidgets has no support for 370There is no support for WxWidgets, as WxWidgets has no support for
371watching file handles. However, you can use WxWidgets through the 371watching file handles. However, you can use WxWidgets through the
372POE Adaptor, as POE has a Wx backend that simply polls 20 times per 372POE Adaptor, as POE has a Wx backend that simply polls 20 times per
373second, which was considered to be too horrible to even consider for 373second, which was considered to be too horrible to even consider for
374AnyEvent. Likewise, other POE backends can be used by Anyevent by using 374AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
375it's adaptor. 375it's adaptor.
376
377AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
378autodetecting them.
376 379
377=item AnyEvent::detect 380=item AnyEvent::detect
378 381
379Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model 382Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
380if necessary. You should only call this function right before you would 383if necessary. You should only call this function right before you would
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431no warnings; 434no warnings;
432use strict; 435use strict;
433 436
434use Carp; 437use Carp;
435 438
436our $VERSION = '3.2'; 439our $VERSION = '3.3';
437our $MODEL; 440our $MODEL;
438 441
439our $AUTOLOAD; 442our $AUTOLOAD;
440our @ISA; 443our @ISA;
441 444
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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
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855 $quit->broadcast; 860 $quit->broadcast;
856 }); 861 });
857 862
858 $quit->wait; 863 $quit->wait;
859 864
865
866=head1 BENCHMARK
867
868To give you an idea of the performance and overheads that AnyEvent adds
869over the event loops themselves (and to give you an impression of the
870speed of various event loops), here is a benchmark of various supported
871event models natively and with anyevent. The benchmark creates a lot of
872timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to
873become writable, which it is), lets them fire exactly once and destroys
874them again.
875
876=head2 Explanation of the columns
877
878I<watcher> is the number of event watchers created/destroyed. Since
879different event models feature vastly different performances, each event
880loop was given a number of watchers so that overall runtime is acceptable
881and similar between tested event loop (and keep them from crashing): Glib
882would probably take thousands of years if asked to process the same number
883of watchers as EV in this benchmark.
884
885I<bytes> is the number of bytes (as measured by the resident set size,
886RSS) consumed by each watcher. This method of measuring captures both C
887and Perl-based overheads.
888
889I<create> is the time, in microseconds (millionths of seconds), that it
890takes to create a single watcher. The callback is a closure shared between
891all watchers, to avoid adding memory overhead. That means closure creation
892and memory usage is not included in the figures.
893
894I<invoke> is the time, in microseconds, used to invoke a simple
895callback. The callback simply counts down a Perl variable and after it was
896invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
897signal the end of this phase.
898
899I<destroy> is the time, in microseconds, that it takes to destroy a single
900watcher.
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
918The benchmark does I<not> measure scalability of the event loop very
919well. For example, a select-based event loop (such as the pure perl one)
920can never compete with an event loop that uses epoll when the number of
921file descriptors grows high. In this benchmark, only a single filehandle
922is used (although some of the AnyEvent adaptors dup() its file descriptor
923to worka round bugs).
924
925C<EV> is the sole leader regarding speed and memory use, which are both
926maximal/minimal, respectively. Even when going through AnyEvent, there is
927only one event loop that uses less memory (the C<Event> module natively), and
928no faster event model, not event C<Event> natively.
929
930The pure perl implementation is hit in a few sweet spots (both the
931zero timeout and the use of a single fd hit optimisations in the perl
932interpreter and the backend itself). Nevertheless tis shows that it
933adds very little overhead in itself. Like any select-based backend its
934performance becomes really bad with lots of file descriptors, of course,
935but this was not subjetc of this benchmark.
936
937The C<Event> module has a relatively high setup and callback invocation cost,
938but overall scores on the third place.
939
940C<Glib>'s memory usage is quite a bit bit higher, features a faster
941callback invocation and overall lands in the same class as C<Event>.
942
943The C<Tk> adaptor works relatively well, the fact that it crashes with
944more than 2000 watchers is a big setback, however, as correctness takes
945precedence over speed. Nevertheless, its performance is surprising, as the
946file descriptor is dup()ed for each watcher. This shows that the dup()
947employed by some adaptors is not a big performance issue (it does incur a
948hidden memory cost inside the kernel, though).
949
950C<POE>, regardless of backend (wether using its pure perl select-based
951backend or the Event backend) shows abysmal performance and memory
952usage: Watchers use almost 30 times as much memory as EV watchers, and 10
953times as much memory as both Event or EV via AnyEvent. Watcher invocation
954is almost 700 times slower as with AnyEvent's pure perl implementation.
955
956Summary: using EV through AnyEvent is faster than any other event
957loop. The overhead AnyEvent adds can be very small, and you should avoid
958POE like the plague if you want performance or reasonable memory usage.
959
960
860=head1 FORK 961=head1 FORK
861 962
862Most event libraries are not fork-safe. The ones who are usually are 963Most event libraries are not fork-safe. The ones who are usually are
863because they are so inefficient. Only L<EV> is fully fork-aware. 964because they are so inefficient. Only L<EV> is fully fork-aware.
864 965
865If you have to fork, you must either do so I<before> creating your first 966If you have to fork, you must either do so I<before> creating your first
866watcher OR you must not use AnyEvent at all in the child. 967watcher OR you must not use AnyEvent at all in the child.
968
867 969
868=head1 SECURITY CONSIDERATIONS 970=head1 SECURITY CONSIDERATIONS
869 971
870AnyEvent can be forced to load any event model via 972AnyEvent can be forced to load any event model via
871$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to 973$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
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879 981
880 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 982 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
881 983
882 use AnyEvent; 984 use AnyEvent;
883 985
986
884=head1 SEE ALSO 987=head1 SEE ALSO
885 988
886Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, 989Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
887L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, 990L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
888L<Event::Lib>, L<Qt>, L<POE>. 991L<Event::Lib>, L<Qt>, L<POE>.
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892L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, 995L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
893L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. 996L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
894 997
895Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. 998Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
896 999
1000
897=head1 AUTHOR 1001=head1 AUTHOR
898 1002
899 Marc Lehmann <schmorp@schmorp.de> 1003 Marc Lehmann <schmorp@schmorp.de>
900 http://home.schmorp.de/ 1004 http://home.schmorp.de/
901 1005

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