… | |
… | |
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 the |
83 | to detect the currently loaded event loop by probing whether one of the |
84 | following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, |
84 | following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, |
85 | L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>, |
85 | L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>, |
86 | L<POE>. The first one found is used. If none are found, the module tries |
86 | L<POE>. The first one found is used. If none are found, the module tries |
87 | to load these modules (excluding Event::Lib, Qt and POE as the pure perl |
87 | to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl |
88 | adaptor should always succeed) in the order given. The first one that can |
88 | adaptor should always succeed) in the order given. The first one that can |
89 | 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 |
90 | 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 |
91 | very efficient, but should work everywhere. |
91 | very efficient, but should work everywhere. |
92 | |
92 | |
… | |
… | |
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 |
… | |
… | |
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 | |
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 |
… | |
… | |
434 | no warnings; |
434 | no warnings; |
435 | use strict; |
435 | use strict; |
436 | |
436 | |
437 | use Carp; |
437 | use Carp; |
438 | |
438 | |
439 | our $VERSION = '3.2'; |
439 | our $VERSION = '3.3'; |
440 | our $MODEL; |
440 | our $MODEL; |
441 | |
441 | |
442 | our $AUTOLOAD; |
442 | our $AUTOLOAD; |
443 | our @ISA; |
443 | our @ISA; |
444 | |
444 | |
… | |
… | |
706 | |
706 | |
707 | =back |
707 | =back |
708 | |
708 | |
709 | =head1 EXAMPLE PROGRAM |
709 | =head1 EXAMPLE PROGRAM |
710 | |
710 | |
711 | 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 |
712 | 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 |
713 | program when the user enters quit: |
713 | program when the user enters quit: |
714 | |
714 | |
715 | use AnyEvent; |
715 | use AnyEvent; |
716 | |
716 | |
… | |
… | |
860 | $quit->broadcast; |
860 | $quit->broadcast; |
861 | }); |
861 | }); |
862 | |
862 | |
863 | $quit->wait; |
863 | $quit->wait; |
864 | |
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, all events become ready at |
|
|
927 | the same time, so select/poll-based implementations get an unnatural speed |
|
|
928 | boost. |
|
|
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 900 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 | |
865 | =head1 FORK |
986 | =head1 FORK |
866 | |
987 | |
867 | 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 |
868 | 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. |
869 | |
990 | |
870 | 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 |
871 | 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 | |
872 | |
994 | |
873 | =head1 SECURITY CONSIDERATIONS |
995 | =head1 SECURITY CONSIDERATIONS |
874 | |
996 | |
875 | AnyEvent can be forced to load any event model via |
997 | AnyEvent can be forced to load any event model via |
876 | $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 |
… | |
… | |
884 | |
1006 | |
885 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1007 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
886 | |
1008 | |
887 | use AnyEvent; |
1009 | use AnyEvent; |
888 | |
1010 | |
|
|
1011 | |
889 | =head1 SEE ALSO |
1012 | =head1 SEE ALSO |
890 | |
1013 | |
891 | 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>, |
892 | 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>, |
893 | L<Event::Lib>, L<Qt>, L<POE>. |
1016 | L<Event::Lib>, L<Qt>, L<POE>. |
… | |
… | |
897 | 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>, |
898 | L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. |
1021 | L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. |
899 | |
1022 | |
900 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
1023 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
901 | |
1024 | |
|
|
1025 | |
902 | =head1 AUTHOR |
1026 | =head1 AUTHOR |
903 | |
1027 | |
904 | Marc Lehmann <schmorp@schmorp.de> |
1028 | Marc Lehmann <schmorp@schmorp.de> |
905 | http://home.schmorp.de/ |
1029 | http://home.schmorp.de/ |
906 | |
1030 | |