… | |
… | |
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 |
… | |
… | |
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 | |
… | |
… | |
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 themselves (and to give you an impression of the |
870 | speed of various event loops), here is a benchmark of various supported |
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 |
871 | event models natively and with anyevent. The benchmark creates a lot of |
872 | 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 |
873 | 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 |
874 | 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. |
875 | |
880 | |
876 | =head2 Explanation of the columns |
881 | =head2 Explanation of the columns |
877 | |
882 | |
878 | I<watcher> is the number of event watchers created/destroyed. Since |
883 | I<watcher> is the number of event watchers created/destroyed. Since |
879 | different event models feature vastly different performances, each event |
884 | different event models feature vastly different performances, each event |
… | |
… | |
899 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
904 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
900 | watcher. |
905 | watcher. |
901 | |
906 | |
902 | =head2 Results |
907 | =head2 Results |
903 | |
908 | |
904 | name watcher bytes create invoke destroy comment |
909 | name watchers bytes create invoke destroy comment |
905 | 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 |
906 | EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers |
911 | 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 |
912 | 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 |
913 | Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation |
909 | Event/Event 16000 523 28.05 21.38 0.86 Event native interface |
914 | 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 |
915 | 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 |
916 | 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 |
917 | 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 |
918 | 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 |
919 | POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select |
915 | |
920 | |
916 | =head2 Discussion |
921 | =head2 Discussion |
917 | |
922 | |
918 | 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 |
919 | 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) |
… | |
… | |
921 | file descriptors grows high. In this benchmark, only a single filehandle |
926 | file descriptors grows high. In this benchmark, only a single filehandle |
922 | is used (although some of the AnyEvent adaptors dup() its file descriptor |
927 | is used (although some of the AnyEvent adaptors dup() its file descriptor |
923 | to worka round bugs). |
928 | to worka round bugs). |
924 | |
929 | |
925 | 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 |
926 | maximal/minimal, respectively. Even when going through AnyEvent, there is |
931 | maximal/minimal, respectively. Even when going through AnyEvent, there are |
927 | 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 |
928 | 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. |
929 | |
935 | |
930 | 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 |
931 | 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 |
932 | interpreter and the backend itself). Nevertheless tis shows that it |
938 | interpreter and the backend itself, and all watchers become ready at the |
933 | 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 |
934 | 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 |
935 | but this was not subjetc of this benchmark. |
942 | this was not subject of this benchmark. |
936 | |
943 | |
937 | 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, |
938 | but overall scores on the third place. |
945 | but overall scores on the third place. |
939 | |
946 | |
940 | C<Glib>'s memory usage is quite a bit bit higher, but it features a |
947 | C<Glib>'s memory usage is quite a bit bit higher, but it features a |
… | |
… | |
948 | 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 |
949 | 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 |
950 | precedence over speed. Nevertheless, its performance is surprising, as the |
957 | precedence over speed. Nevertheless, its performance is surprising, as the |
951 | 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() |
952 | 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 |
953 | hidden memory cost inside the kernel, though). |
960 | hidden memory cost inside the kernel, though, that is not reflected in the |
|
|
961 | figures above). |
954 | |
962 | |
955 | C<POE>, regardless of underlying event loop (wether using its pure perl |
963 | C<POE>, regardless of underlying event loop (wether using its pure perl |
956 | select-based backend or the Event module) shows abysmal performance and |
964 | select-based backend or the Event module) shows abysmal performance and |
957 | memory usage: Watchers use almost 30 times as much memory as EV watchers, |
965 | memory usage: Watchers use almost 30 times as much memory as EV watchers, |
958 | and 10 times as much memory as both Event or EV via AnyEvent. Watcher |
966 | and 10 times as much memory as both Event or EV via AnyEvent. Watcher |
959 | invocation is almost 700 times slower than with AnyEvent's pure perl |
967 | invocation is almost 900 times slower than with AnyEvent's pure perl |
960 | implementation. The design of the POE adaptor class in AnyEvent can not |
968 | implementation. The design of the POE adaptor class in AnyEvent can not |
961 | really account for this, as session creation overhead is small compared |
969 | really account for this, as session creation overhead is small compared |
962 | to execution of the state machine, which is coded pretty optimally within |
970 | to execution of the state machine, which is coded pretty optimally within |
963 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
971 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
964 | |
972 | |