1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | AnyEvent - provide framework for multiple event loops |
3 | AnyEvent - provide framework for multiple event loops |
4 | |
4 | |
5 | EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt - various supported event loops |
5 | EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops |
6 | |
6 | |
7 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
8 | |
8 | |
9 | use AnyEvent; |
9 | use AnyEvent; |
10 | |
10 | |
… | |
… | |
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>. The first one found is used. If none are found, |
85 | L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>, |
86 | the module tries to load these modules in the stated order. The first one |
86 | L<POE>. The first one found is used. If none are found, the module tries |
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87 | to load these modules (excluding Event::Lib, Qt and POE as the pure perl |
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88 | adaptor should always succeed) in the order given. The first one that can |
87 | that can be successfully loaded will be used. If, after this, still none |
89 | be successfully loaded will be used. If, after this, still none could be |
88 | could be found, AnyEvent will fall back to a pure-perl event loop, which |
90 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
89 | is not very efficient, but should work everywhere. |
91 | very efficient, but should work everywhere. |
90 | |
92 | |
91 | Because AnyEvent first checks for modules that are already loaded, loading |
93 | Because AnyEvent first checks for modules that are already loaded, loading |
92 | an event model explicitly before first using AnyEvent will likely make |
94 | an event model explicitly before first using AnyEvent will likely make |
93 | that model the default. For example: |
95 | that model the default. For example: |
94 | |
96 | |
… | |
… | |
206 | |
208 | |
207 | There are two ways to handle timers: based on real time (relative, "fire |
209 | There are two ways to handle timers: based on real time (relative, "fire |
208 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
210 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
209 | o'clock"). |
211 | o'clock"). |
210 | |
212 | |
211 | While most event loops expect timers to specified in a relative way, they use |
213 | While most event loops expect timers to specified in a relative way, they |
212 | absolute time internally. This makes a difference when your clock "jumps", |
214 | use absolute time internally. This makes a difference when your clock |
213 | for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to |
215 | "jumps", for example, when ntp decides to set your clock backwards from |
214 | 2008-01-01, a watcher that you created to fire "after" a second might actually take |
216 | the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to |
215 | six years to finally fire. |
217 | fire "after" a second might actually take six years to finally fire. |
216 | |
218 | |
217 | AnyEvent cannot compensate for this. The only event loop that is conscious |
219 | AnyEvent cannot compensate for this. The only event loop that is conscious |
218 | about these issues is L<EV>, which offers both relative (ev_timer) and |
220 | about these issues is L<EV>, which offers both relative (ev_timer, based |
219 | absolute (ev_periodic) timers. |
221 | on true relative time) and absolute (ev_periodic, based on wallclock time) |
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222 | timers. |
220 | |
223 | |
221 | AnyEvent always prefers relative timers, if available, matching the |
224 | AnyEvent always prefers relative timers, if available, matching the |
222 | AnyEvent API. |
225 | AnyEvent API. |
223 | |
226 | |
224 | =head2 SIGNAL WATCHERS |
227 | =head2 SIGNAL WATCHERS |
225 | |
228 | |
226 | You can watch for signals using a signal watcher, C<signal> is the signal |
229 | You can watch for signals using a signal watcher, C<signal> is the signal |
227 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
230 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
228 | be invoked whenever a signal occurs. |
231 | be invoked whenever a signal occurs. |
229 | |
232 | |
230 | Multiple signals occurances can be clumped together into one callback |
233 | Multiple signal occurances can be clumped together into one callback |
231 | invocation, and callback invocation will be synchronous. synchronous means |
234 | invocation, and callback invocation will be synchronous. synchronous means |
232 | that it might take a while until the signal gets handled by the process, |
235 | that it might take a while until the signal gets handled by the process, |
233 | but it is guarenteed not to interrupt any other callbacks. |
236 | but it is guarenteed not to interrupt any other callbacks. |
234 | |
237 | |
235 | The main advantage of using these watchers is that you can share a signal |
238 | The main advantage of using these watchers is that you can share a signal |
… | |
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360 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
363 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
361 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
364 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
362 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
365 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
363 | 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). |
364 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
367 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
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368 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
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369 | |
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370 | There is no support for WxWidgets, as WxWidgets has no support for |
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371 | watching file handles. However, you can use WxWidgets through the |
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372 | POE Adaptor, as POE has a Wx backend that simply polls 20 times per |
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373 | second, which was considered to be too horrible to even consider for |
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374 | AnyEvent. Likewise, other POE backends can be used by AnyEvent by using |
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375 | it's adaptor. |
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376 | |
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377 | AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when |
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378 | autodetecting them. |
365 | |
379 | |
366 | =item AnyEvent::detect |
380 | =item AnyEvent::detect |
367 | |
381 | |
368 | Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
382 | Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
369 | if necessary. You should only call this function right before you would |
383 | if necessary. You should only call this function right before you would |
… | |
… | |
420 | no warnings; |
434 | no warnings; |
421 | use strict; |
435 | use strict; |
422 | |
436 | |
423 | use Carp; |
437 | use Carp; |
424 | |
438 | |
425 | our $VERSION = '3.12'; |
439 | our $VERSION = '3.3'; |
426 | our $MODEL; |
440 | our $MODEL; |
427 | |
441 | |
428 | our $AUTOLOAD; |
442 | our $AUTOLOAD; |
429 | our @ISA; |
443 | our @ISA; |
430 | |
444 | |
… | |
… | |
437 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
451 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
438 | [EV:: => AnyEvent::Impl::EV::], |
452 | [EV:: => AnyEvent::Impl::EV::], |
439 | [Event:: => AnyEvent::Impl::Event::], |
453 | [Event:: => AnyEvent::Impl::Event::], |
440 | [Glib:: => AnyEvent::Impl::Glib::], |
454 | [Glib:: => AnyEvent::Impl::Glib::], |
441 | [Tk:: => AnyEvent::Impl::Tk::], |
455 | [Tk:: => AnyEvent::Impl::Tk::], |
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|
456 | [Wx:: => AnyEvent::Impl::POE::], |
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|
457 | [Prima:: => AnyEvent::Impl::POE::], |
442 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
458 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
443 | ); |
459 | # everything below here will not be autoprobed as the pureperl backend should work everywhere |
444 | my @models_detect = ( |
460 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
445 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
461 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
446 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
462 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
447 | ); |
463 | ); |
448 | |
464 | |
449 | our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); |
465 | our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); |
450 | |
466 | |
451 | sub detect() { |
467 | sub detect() { |
… | |
… | |
455 | if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { |
471 | if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { |
456 | my $model = "AnyEvent::Impl::$1"; |
472 | my $model = "AnyEvent::Impl::$1"; |
457 | if (eval "require $model") { |
473 | if (eval "require $model") { |
458 | $MODEL = $model; |
474 | $MODEL = $model; |
459 | warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1; |
475 | warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1; |
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476 | } else { |
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477 | warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose; |
460 | } |
478 | } |
461 | } |
479 | } |
462 | |
480 | |
463 | # check for already loaded models |
481 | # check for already loaded models |
464 | unless ($MODEL) { |
482 | unless ($MODEL) { |
465 | for (@REGISTRY, @models, @models_detect) { |
483 | for (@REGISTRY, @models) { |
466 | my ($package, $model) = @$_; |
484 | my ($package, $model) = @$_; |
467 | if (${"$package\::VERSION"} > 0) { |
485 | if (${"$package\::VERSION"} > 0) { |
468 | if (eval "require $model") { |
486 | if (eval "require $model") { |
469 | $MODEL = $model; |
487 | $MODEL = $model; |
470 | warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1; |
488 | warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1; |
… | |
… | |
657 | |
675 | |
658 | =over 4 |
676 | =over 4 |
659 | |
677 | |
660 | =item C<PERL_ANYEVENT_VERBOSE> |
678 | =item C<PERL_ANYEVENT_VERBOSE> |
661 | |
679 | |
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680 | By default, AnyEvent will be completely silent except in fatal |
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681 | conditions. You can set this environment variable to make AnyEvent more |
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682 | talkative. |
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683 | |
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684 | When set to C<1> or higher, causes AnyEvent to warn about unexpected |
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685 | conditions, such as not being able to load the event model specified by |
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686 | C<PERL_ANYEVENT_MODEL>. |
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687 | |
662 | When set to C<2> or higher, cause AnyEvent to report to STDERR which event |
688 | When set to C<2> or higher, cause AnyEvent to report to STDERR which event |
663 | model it chooses. |
689 | model it chooses. |
664 | |
690 | |
665 | =item C<PERL_ANYEVENT_MODEL> |
691 | =item C<PERL_ANYEVENT_MODEL> |
666 | |
692 | |
… | |
… | |
834 | $quit->broadcast; |
860 | $quit->broadcast; |
835 | }); |
861 | }); |
836 | |
862 | |
837 | $quit->wait; |
863 | $quit->wait; |
838 | |
864 | |
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865 | |
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866 | =head1 BENCHMARK |
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867 | |
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868 | To give you an idea of the performance and overheads that AnyEvent adds |
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869 | over the event loops themselves (and to give you an impression of the |
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870 | speed of various event loops), here is a benchmark of various supported |
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871 | event models natively and with anyevent. The benchmark creates a lot of |
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872 | timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to |
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873 | become writable, which it is), lets them fire exactly once and destroys |
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874 | them again. |
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875 | |
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876 | =head2 Explanation of the columns |
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877 | |
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878 | I<watcher> is the number of event watchers created/destroyed. Since |
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879 | different event models feature vastly different performances, each event |
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880 | loop was given a number of watchers so that overall runtime is acceptable |
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881 | and similar between tested event loop (and keep them from crashing): Glib |
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882 | would probably take thousands of years if asked to process the same number |
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883 | of watchers as EV in this benchmark. |
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884 | |
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885 | I<bytes> is the number of bytes (as measured by the resident set size, |
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886 | RSS) consumed by each watcher. This method of measuring captures both C |
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887 | and Perl-based overheads. |
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888 | |
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889 | I<create> is the time, in microseconds (millionths of seconds), that it |
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890 | takes to create a single watcher. The callback is a closure shared between |
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891 | all watchers, to avoid adding memory overhead. That means closure creation |
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892 | and memory usage is not included in the figures. |
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893 | |
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894 | I<invoke> is the time, in microseconds, used to invoke a simple |
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895 | callback. The callback simply counts down a Perl variable and after it was |
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896 | invoked "watcher" times, it would C<< ->broadcast >> a condvar once to |
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897 | signal the end of this phase. |
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898 | |
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899 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
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900 | watcher. |
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901 | |
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902 | =head2 Results |
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903 | |
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904 | name watchers bytes create invoke destroy comment |
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905 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
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906 | EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers |
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907 | CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal |
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908 | Perl/Any 16000 654 4.64 1.22 0.77 pure perl implementation |
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909 | Event/Event 16000 523 28.05 21.38 0.86 Event native interface |
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910 | Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers |
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911 | Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour |
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912 | Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers |
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913 | POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event |
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914 | POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select |
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915 | |
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916 | =head2 Discussion |
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917 | |
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|
918 | The benchmark does I<not> measure scalability of the event loop very |
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919 | well. For example, a select-based event loop (such as the pure perl one) |
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920 | can never compete with an event loop that uses epoll when the number of |
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921 | file descriptors grows high. In this benchmark, only a single filehandle |
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922 | is used (although some of the AnyEvent adaptors dup() its file descriptor |
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923 | to worka round bugs). |
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924 | |
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925 | C<EV> is the sole leader regarding speed and memory use, which are both |
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926 | maximal/minimal, respectively. Even when going through AnyEvent, there is |
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927 | only one event loop that uses less memory (the C<Event> module natively), and |
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928 | no faster event model, not event C<Event> natively. |
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929 | |
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930 | The pure perl implementation is hit in a few sweet spots (both the |
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931 | zero timeout and the use of a single fd hit optimisations in the perl |
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932 | interpreter and the backend itself). Nevertheless tis shows that it |
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933 | adds very little overhead in itself. Like any select-based backend its |
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934 | performance becomes really bad with lots of file descriptors, of course, |
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935 | but this was not subjetc of this benchmark. |
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936 | |
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937 | The C<Event> module has a relatively high setup and callback invocation cost, |
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938 | but overall scores on the third place. |
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939 | |
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940 | C<Glib>'s memory usage is quite a bit bit higher, but it features a |
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941 | faster callback invocation and overall ends up in the same class as |
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942 | C<Event>. However, Glib scales extremely badly, doubling the number of |
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943 | watchers increases the processing time by more than a factor of four, |
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944 | making it completely unusable when using larger numbers of watchers |
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945 | (note that only a single file descriptor was used in the benchmark, so |
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946 | inefficiencies of C<poll> do not account for this). |
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947 | |
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948 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
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949 | more than 2000 watchers is a big setback, however, as correctness takes |
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950 | precedence over speed. Nevertheless, its performance is surprising, as the |
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951 | file descriptor is dup()ed for each watcher. This shows that the dup() |
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952 | employed by some adaptors is not a big performance issue (it does incur a |
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953 | hidden memory cost inside the kernel, though, that is not reflected in the |
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954 | figures above). |
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955 | |
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956 | C<POE>, regardless of underlying event loop (wether using its pure perl |
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957 | select-based backend or the Event module) shows abysmal performance and |
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958 | memory usage: Watchers use almost 30 times as much memory as EV watchers, |
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959 | and 10 times as much memory as both Event or EV via AnyEvent. Watcher |
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960 | invocation is almost 700 times slower than with AnyEvent's pure perl |
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961 | implementation. The design of the POE adaptor class in AnyEvent can not |
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962 | really account for this, as session creation overhead is small compared |
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963 | to execution of the state machine, which is coded pretty optimally within |
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964 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
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965 | |
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966 | =head2 Summary |
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967 | |
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968 | Using EV through AnyEvent is faster than any other event loop, but most |
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969 | event loops have acceptable performance with or without AnyEvent. |
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970 | |
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971 | The overhead AnyEvent adds is usually much smaller than the overhead of |
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972 | the actual event loop, only with extremely fast event loops such as the EV |
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973 | adds AnyEvent significant overhead. |
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974 | |
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975 | And you should simply avoid POE like the plague if you want performance or |
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976 | reasonable memory usage. |
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977 | |
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978 | |
839 | =head1 FORK |
979 | =head1 FORK |
840 | |
980 | |
841 | Most event libraries are not fork-safe. The ones who are usually are |
981 | Most event libraries are not fork-safe. The ones who are usually are |
842 | because they are so inefficient. Only L<EV> is fully fork-aware. |
982 | because they are so inefficient. Only L<EV> is fully fork-aware. |
843 | |
983 | |
844 | If you have to fork, you must either do so I<before> creating your first |
984 | If you have to fork, you must either do so I<before> creating your first |
845 | watcher OR you must not use AnyEvent at all in the child. |
985 | watcher OR you must not use AnyEvent at all in the child. |
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986 | |
846 | |
987 | |
847 | =head1 SECURITY CONSIDERATIONS |
988 | =head1 SECURITY CONSIDERATIONS |
848 | |
989 | |
849 | AnyEvent can be forced to load any event model via |
990 | AnyEvent can be forced to load any event model via |
850 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
991 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
… | |
… | |
858 | |
999 | |
859 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1000 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
860 | |
1001 | |
861 | use AnyEvent; |
1002 | use AnyEvent; |
862 | |
1003 | |
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1004 | |
863 | =head1 SEE ALSO |
1005 | =head1 SEE ALSO |
864 | |
1006 | |
865 | Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
1007 | Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
866 | L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, |
1008 | L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, |
867 | L<Event::Lib>, L<Qt>. |
1009 | L<Event::Lib>, L<Qt>, L<POE>. |
868 | |
1010 | |
869 | Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, |
1011 | Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, |
870 | L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, |
1012 | L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, |
871 | L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, |
1013 | L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, |
872 | L<AnyEvent::Impl::Qt>. |
1014 | L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. |
873 | |
1015 | |
874 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
1016 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
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1017 | |
875 | |
1018 | |
876 | =head1 AUTHOR |
1019 | =head1 AUTHOR |
877 | |
1020 | |
878 | Marc Lehmann <schmorp@schmorp.de> |
1021 | Marc Lehmann <schmorp@schmorp.de> |
879 | http://home.schmorp.de/ |
1022 | http://home.schmorp.de/ |