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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.77 by root, Fri Apr 25 09:00:37 2008 UTC vs.
Revision 1.81 by root, Fri Apr 25 13:05:17 2008 UTC

80module. 80module.
81 81
82During the first call of any watcher-creation method, the module tries 82During the first call of any watcher-creation method, the module tries
83to detect the currently loaded event loop by probing whether one of the 83to detect the currently loaded event loop by probing whether one of the
84following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, 84following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
85L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>, 85L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86L<POE>. The first one found is used. If none are found, the module tries 86L<POE>. The first one found is used. If none are found, the module tries
87to load these modules (excluding Event::Lib, Qt and POE as the pure perl 87to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
88adaptor should always succeed) in the order given. The first one that can 88adaptor should always succeed) in the order given. The first one that can
89be successfully loaded will be used. If, after this, still none could be 89be successfully loaded will be used. If, after this, still none could be
90found, AnyEvent will fall back to a pure-perl event loop, which is not 90found, AnyEvent will fall back to a pure-perl event loop, which is not
91very efficient, but should work everywhere. 91very efficient, but should work everywhere.
92 92
136 136
137Note that C<my $w; $w => combination. This is necessary because in Perl, 137Note that C<my $w; $w => combination. This is necessary because in Perl,
138my variables are only visible after the statement in which they are 138my variables are only visible after the statement in which they are
139declared. 139declared.
140 140
141=head2 IO WATCHERS 141=head2 I/O WATCHERS
142 142
143You can create an I/O watcher by calling the C<< AnyEvent->io >> method 143You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144with the following mandatory key-value pairs as arguments: 144with the following mandatory key-value pairs as arguments:
145 145
146C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for 146C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for
359 AnyEvent::Impl::CoroEV based on Coro::EV, best choice. 359 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
360 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. 360 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
361 AnyEvent::Impl::EV based on EV (an interface to libev, best choice). 361 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
362 AnyEvent::Impl::Event based on Event, second best choice. 362 AnyEvent::Impl::Event based on Event, second best choice.
363 AnyEvent::Impl::Glib based on Glib, third-best choice. 363 AnyEvent::Impl::Glib based on Glib, third-best choice.
364 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
364 AnyEvent::Impl::Tk based on Tk, very bad choice. 365 AnyEvent::Impl::Tk based on Tk, very bad choice.
365 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
366 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).
367 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. 368 AnyEvent::Impl::POE based on POE, not generic enough for full support.
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
706 706
707=back 707=back
708 708
709=head1 EXAMPLE PROGRAM 709=head1 EXAMPLE PROGRAM
710 710
711The following program uses an IO watcher to read data from STDIN, a timer 711The following program uses an I/O watcher to read data from STDIN, a timer
712to display a message once per second, and a condition variable to quit the 712to display a message once per second, and a condition variable to quit the
713program when the user enters quit: 713program when the user enters quit:
714 714
715 use AnyEvent; 715 use AnyEvent;
716 716
867 867
868To give you an idea of the performance and overheads that AnyEvent adds 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 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 870speed of various event loops), here is a benchmark of various supported
871event models natively and with anyevent. The benchmark creates a lot of 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 872timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to
873become writable, which it is), lets them fire exactly once and destroys 873become writable, which it is), lets them fire exactly once and destroys
874them again. 874them again.
875 875
876Rewriting the benchmark to use many different sockets instead of using 876Rewriting the benchmark to use many different sockets instead of using
877the same filehandle for all io watchers results in a much longer runtime 877the 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 878(socket creation is expensive), but qualitatively the same figures, so it
879was not used. 879was not used.
880 880
881=head2 Explanation of the columns 881=head2 Explanation of the columns
882 882
921=head2 Discussion 921=head2 Discussion
922 922
923The benchmark does I<not> measure scalability of the event loop very 923The benchmark does I<not> measure scalability of the event loop very
924well. For example, a select-based event loop (such as the pure perl one) 924well. For example, a select-based event loop (such as the pure perl one)
925can never compete with an event loop that uses epoll when the number of 925can never compete with an event loop that uses epoll when the number of
926file descriptors grows high. In this benchmark, only a single filehandle 926file descriptors grows high. In this benchmark, all events become ready at
927is used (although some of the AnyEvent adaptors dup() its file descriptor 927the same time, so select/poll-based implementations get an unnatural speed
928to worka round bugs). 928boost.
929 929
930C<EV> is the sole leader regarding speed and memory use, which are both 930C<EV> is the sole leader regarding speed and memory use, which are both
931maximal/minimal, respectively. Even when going through AnyEvent, there are 931maximal/minimal, respectively. Even when going through AnyEvent, there are
932only two event loops that use slightly less memory (the C<Event> module 932only two event loops that use slightly less memory (the C<Event> module
933natively and the pure perl backend), and no faster event models, not even 933natively and the pure perl backend), and no faster event models, not even
962 962
963C<POE>, regardless of underlying event loop (wether using its pure perl 963C<POE>, regardless of underlying event loop (wether using its pure perl
964select-based backend or the Event module) shows abysmal performance and 964select-based backend or the Event module) shows abysmal performance and
965memory usage: Watchers use almost 30 times as much memory as EV watchers, 965memory usage: Watchers use almost 30 times as much memory as EV watchers,
966and 10 times as much memory as both Event or EV via AnyEvent. Watcher 966and 10 times as much memory as both Event or EV via AnyEvent. Watcher
967invocation is almost 700 times slower than with AnyEvent's pure perl 967invocation is almost 900 times slower than with AnyEvent's pure perl
968implementation. The design of the POE adaptor class in AnyEvent can not 968implementation. The design of the POE adaptor class in AnyEvent can not
969really account for this, as session creation overhead is small compared 969really account for this, as session creation overhead is small compared
970to execution of the state machine, which is coded pretty optimally within 970to execution of the state machine, which is coded pretty optimally within
971L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. 971L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
972 972

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