… | |
… | |
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 |
… | |
… | |
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 | |
… | |
… | |
864 | |
864 | |
865 | |
865 | |
866 | =head1 BENCHMARK |
866 | =head1 BENCHMARK |
867 | |
867 | |
868 | To give you an idea of the performance and overheads that AnyEvent adds |
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 |
869 | over the event loops directly, here is a benchmark of various supported |
870 | speed of various event loops), here is a benchmark of various supported |
870 | event models natively and with anyevent. The benchmark creates a lot of |
871 | event models natively and with anyevent. The benchmark creates a lot of |
871 | timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to |
872 | timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to |
872 | become writable, which it is), lets them fire exactly once and destroys |
873 | become writable, which it is), lets them fire exactly once and destroys |
873 | them again. |
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. |
874 | |
880 | |
875 | =head2 Explanation of the columns |
881 | =head2 Explanation of the columns |
876 | |
882 | |
877 | I<watcher> is the number of event watchers created/destroyed. Since |
883 | I<watcher> is the number of event watchers created/destroyed. Since |
878 | different event models feature vastly different performances, each event |
884 | different event models feature vastly different performances, each event |
… | |
… | |
893 | I<invoke> is the time, in microseconds, used to invoke a simple |
899 | I<invoke> is the time, in microseconds, used to invoke a simple |
894 | callback. The callback simply counts down a Perl variable and after it was |
900 | callback. The callback simply counts down a Perl variable and after it was |
895 | invoked "watcher" times, it would C<< ->broadcast >> a condvar once to |
901 | invoked "watcher" times, it would C<< ->broadcast >> a condvar once to |
896 | signal the end of this phase. |
902 | signal the end of this phase. |
897 | |
903 | |
898 | I<destroy> is the time, in microseconds, that it takes destroy a single |
904 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
899 | watcher. |
905 | watcher. |
900 | |
906 | |
901 | =head2 Results |
907 | =head2 Results |
902 | |
908 | |
903 | name watcher bytes create invoke destroy comment |
909 | name watchers bytes create invoke destroy comment |
904 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
910 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
905 | EV/Any 100000 610 3.52 0.91 0.75 |
911 | EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers |
906 | CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal |
912 | CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal |
907 | Perl/Any 10000 654 4.64 1.22 0.77 pure perl implementation |
913 | Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation |
908 | Event/Event 10000 523 28.05 21.38 5.22 Event native interface |
914 | Event/Event 16000 523 28.05 21.38 0.86 Event native interface |
909 | Event/Any 10000 943 34.43 20.48 1.39 |
915 | Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers |
910 | Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour |
916 | Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour |
911 | Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers |
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 |
912 | POE/Select 2000 6343 94.69 807.65 562.69 POE::Loop::Select |
919 | POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select |
913 | POE/Event 2000 6644 108.15 768.19 14.33 POE::Loop::Event |
|
|
914 | |
920 | |
915 | =head2 Discussion |
921 | =head2 Discussion |
916 | |
922 | |
917 | The benchmark does I<not> measure scalability of the event loop very |
923 | The benchmark does I<not> measure scalability of the event loop very |
918 | well. For example, a select-based event loop (such as the pure perl one) |
924 | well. For example, a select-based event loop (such as the pure perl one) |
919 | can never compete with an event loop that uses epoll when the number of |
925 | can never compete with an event loop that uses epoll when the number of |
920 | file descriptors grows high. In this benchmark, only a single filehandle |
926 | file descriptors grows high. In this benchmark, all events become ready at |
921 | is used (although some of the AnyEvent adaptors dup() its file descriptor |
927 | the same time, so select/poll-based implementations get an unnatural speed |
922 | to worka round bugs). |
928 | boost. |
923 | |
929 | |
924 | C<EV> is the sole leader regarding speed and memory use, which are both |
930 | C<EV> is the sole leader regarding speed and memory use, which are both |
925 | maximal/minimal, respectively. Even when going through AnyEvent, there is |
931 | maximal/minimal, respectively. Even when going through AnyEvent, there are |
926 | only one event loop that uses less memory (the C<Event> module natively), and |
932 | only two event loops that use slightly less memory (the C<Event> module |
927 | no faster event model, not event C<Event> natively. |
933 | natively and the pure perl backend), and no faster event models, not even |
|
|
934 | C<Event> natively. |
928 | |
935 | |
929 | The pure perl implementation is hit in a few sweet spots (both the |
936 | The pure perl implementation is hit in a few sweet spots (both the |
930 | zero timeout and the use of a single fd hit optimisations in the perl |
937 | zero timeout and the use of a single fd hit optimisations in the perl |
931 | interpreter and the backend itself). Nevertheless tis shows that it |
938 | interpreter and the backend itself, and all watchers become ready at the |
932 | adds very little overhead in itself. Like any select-based backend its |
939 | same time). Nevertheless this shows that it adds very little overhead in |
933 | performance becomes really bad with lots of file descriptors, of course, |
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 |
934 | but this was not subjetc of this benchmark. |
942 | this was not subject of this benchmark. |
935 | |
943 | |
936 | The C<Event> module has a relatively high setup and callback invocation cost, |
944 | The C<Event> module has a relatively high setup and callback invocation cost, |
937 | but overall scores on the third place. |
945 | but overall scores on the third place. |
938 | |
946 | |
939 | C<Glib>'s memory usage is quite a bit bit higher, features a faster |
947 | C<Glib>'s memory usage is quite a bit bit higher, but it features a |
940 | callback invocation and overall lands in the same class as C<Event>. |
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). |
941 | |
954 | |
942 | The C<Tk> adaptor works relatively well, the fact that it crashes with |
955 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
943 | more than 2000 watchers is a big setback, however, as correctness takes |
956 | more than 2000 watchers is a big setback, however, as correctness takes |
944 | precedence over speed. Nevertheless, its performance is surprising, as the |
957 | precedence over speed. Nevertheless, its performance is surprising, as the |
945 | file descriptor is dup()ed for each watcher. This shows that the dup() |
958 | file descriptor is dup()ed for each watcher. This shows that the dup() |
946 | employed by some adaptors is not a big performance issue (it does incur a |
959 | employed by some adaptors is not a big performance issue (it does incur a |
947 | hidden memory cost inside the kernel, though). |
960 | hidden memory cost inside the kernel, though, that is not reflected in the |
|
|
961 | figures above). |
948 | |
962 | |
949 | C<POE>, regardless of backend (wether using its pure perl select-based |
963 | C<POE>, regardless of underlying event loop (wether using its pure perl |
950 | backend or the Event backend) shows abysmal performance and memory |
964 | select-based backend or the Event module) shows abysmal performance and |
951 | usage: Watchers use almost 30 times as much memory as EV watchers, and 10 |
965 | memory usage: Watchers use almost 30 times as much memory as EV watchers, |
952 | times as much memory as both Event or EV via AnyEvent. Watcher invocation |
966 | and 10 times as much memory as both Event or EV via AnyEvent. Watcher |
953 | is almost 700 times slower as with AnyEvent's pure perl implementation. |
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. |
954 | |
972 | |
|
|
973 | =head2 Summary |
|
|
974 | |
955 | Summary: using EV through AnyEvent is faster than any other event |
975 | Using EV through AnyEvent is faster than any other event loop, but most |
956 | loop. The overhead AnyEvent adds can be very small, and you should avoid |
976 | event loops have acceptable performance with or without AnyEvent. |
957 | POE like the plague if you want performance or reasonable memory usage. |
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. |
958 | |
984 | |
959 | |
985 | |
960 | =head1 FORK |
986 | =head1 FORK |
961 | |
987 | |
962 | 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 |