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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.68 by root, Fri Apr 25 07:14:33 2008 UTC vs.
Revision 1.72 by root, Fri Apr 25 07:43:25 2008 UTC

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864 864
865 865
866=head1 BENCHMARK 866=head1 BENCHMARK
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 directly, here is a benchmark of various supported 870speed of various event loops), here is a benchmark of various supported
870event models natively and with anyevent. The benchmark creates a lot of 871event models natively and with anyevent. The benchmark creates a lot of
871timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to 872timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to
872become writable, which it is), lets them fire exactly once and destroys 873become writable, which it is), lets them fire exactly once and destroys
873them again. 874them again.
874 875
875=head2 Explanation of the fields 876=head2 Explanation of the columns
876 877
877I<watcher> is the number of event watchers created/destroyed. Since 878I<watcher> is the number of event watchers created/destroyed. Since
878different event models feature vastly different performances, each event 879different event models feature vastly different performances, each event
879loop was given a number of watchers so that overall runtime is acceptable 880loop was given a number of watchers so that overall runtime is acceptable
880and similar between tested event loop (and keep them from crashing): Glib 881and similar between tested event loop (and keep them from crashing): Glib
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890all watchers, to avoid adding memory overhead. That means closure creation 891all watchers, to avoid adding memory overhead. That means closure creation
891and memory usage is not included in the figures. 892and memory usage is not included in the figures.
892 893
893I<invoke> is the time, in microseconds, used to invoke a simple 894I<invoke> is the time, in microseconds, used to invoke a simple
894callback. The callback simply counts down a Perl variable and after it was 895callback. The callback simply counts down a Perl variable and after it was
895invoked "watcher" times, it would C<< ->broadcast >> a condvar once. 896invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
897signal the end of this phase.
896 898
897I<destroy> is the time, in microseconds, that it takes destroy a single 899I<destroy> is the time, in microseconds, that it takes to destroy a single
898watcher. 900watcher.
899 901
900=head2 Results 902=head2 Results
901 903
902 name watcher bytes create invoke destroy comment 904 name watcher bytes create invoke destroy comment
903 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 905 EV/EV 400000 244 0.56 0.46 0.31 EV native interface
904 EV/Any 100000 610 3.52 0.91 0.75 906 EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers
905 CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal 907 CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal
906 Perl/Any 10000 654 4.64 1.22 0.77 pure perl implementation 908 Perl/Any 16000 654 4.64 1.22 0.77 pure perl implementation
907 Event/Event 10000 523 28.05 21.38 5.22 Event native interface 909 Event/Event 16000 523 28.05 21.38 0.86 Event native interface
908 Event/Any 10000 943 34.43 20.48 1.39 910 Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers
909 Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour 911 Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour
910 Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers 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
911 POE/Select 2000 6343 94.69 807.65 562.69 POE::Loop::Select 914 POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select
912 POE/Event 2000 6644 108.15 768.19 14.33 POE::Loop::Event
913 915
914=head2 Discussion 916=head2 Discussion
915 917
916The benchmark does I<not> measure scalability of the event loop very 918The benchmark does I<not> measure scalability of the event loop very
917well. For example, a select-based event loop (such as the pure perl one) 919well. For example, a select-based event loop (such as the pure perl one)
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943precedence over speed. Nevertheless, its performance is surprising, as the 945precedence over speed. Nevertheless, its performance is surprising, as the
944file descriptor is dup()ed for each watcher. This shows that the dup() 946file descriptor is dup()ed for each watcher. This shows that the dup()
945employed by some adaptors is not a big performance issue (it does incur a 947employed by some adaptors is not a big performance issue (it does incur a
946hidden memory cost inside the kernel, though). 948hidden memory cost inside the kernel, though).
947 949
948C<POE>, regardless of backend (wether using its pure perl select-based 950C<POE>, regardless of underlying event loop (wether using its pure perl
949backend or the Event backend) shows abysmal performance and memory 951select-based backend or the Event module) shows abysmal performance and
950usage: Watchers use almost 30 times as much memory as EV watchers, and 10 952memory usage: Watchers use almost 30 times as much memory as EV watchers,
951times as much memory as both Event or EV via AnyEvent. Watcher invocation 953and 10 times as much memory as both Event or EV via AnyEvent. Watcher
952is almost 700 times slower as with AnyEvent's pure perl implementation. 954invocation is almost 700 times slower than with AnyEvent's pure perl
955implementation. The design of the POE adaptor class in AnyEvent can not
956really account for this, as session creation overhead is small compared
957to execution of the state machine, which is coded pretty optimally within
958L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
953 959
960=head2 Summary
961
954Summary: using EV through AnyEvent is faster than any other event 962Using EV through AnyEvent is faster than any other event loop, but most
955loop. The overhead AnyEvent adds can be very small, and you should avoid 963event loops have acceptable performance with or without AnyEvent.
956POE like the plague if you want performance or reasonable memory usage. 964
965The overhead AnyEvent adds is usually much smaller than the overhead of
966the actual event loop, only with extremely fast event loops such as the EV
967adds Anyevent significant overhead.
968
969And you should simply avoid POE like the plague if you want performance or
970reasonable memory usage.
957 971
958 972
959=head1 FORK 973=head1 FORK
960 974
961Most event libraries are not fork-safe. The ones who are usually are 975Most event libraries are not fork-safe. The ones who are usually are

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