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Revision 1.56 by root, Thu Apr 24 03:10:03 2008 UTC vs.
Revision 1.64 by root, Fri Apr 25 06:54:08 2008 UTC

1=head1 NAME 1=head1 NAME
2 2
3AnyEvent - provide framework for multiple event loops 3AnyEvent - provide framework for multiple event loops
4 4
5EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt - various supported event loops 5EV, 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
… …
80module. 80module.
81 81
82During the first call of any watcher-creation method, the module tries 82During the first call of any watcher-creation method, the module tries
83to detect the currently loaded event loop by probing whether one of the 83to detect the currently loaded event loop by probing whether one of the
84following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, 84following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
85L<Event>, L<Glib>, L<Tk>. The first one found is used. If none are found, 85L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,
86the module tries to load these modules in the stated order. The first one 86L<POE>. The first one found is used. If none are found, the module tries
87to load these modules (excluding Event::Lib, Qt and POE as the pure perl
88adaptor should always succeed) in the order given. The first one that can
87that can be successfully loaded will be used. If, after this, still none 89be successfully loaded will be used. If, after this, still none could be
88could be found, AnyEvent will fall back to a pure-perl event loop, which 90found, AnyEvent will fall back to a pure-perl event loop, which is not
89is not very efficient, but should work everywhere. 91very efficient, but should work everywhere.
90 92
91Because AnyEvent first checks for modules that are already loaded, loading 93Because AnyEvent first checks for modules that are already loaded, loading
92an event model explicitly before first using AnyEvent will likely make 94an event model explicitly before first using AnyEvent will likely make
93that model the default. For example: 95that model the default. For example:
94 96
… …
206 208
207There are two ways to handle timers: based on real time (relative, "fire 209There are two ways to handle timers: based on real time (relative, "fire
208in 10 seconds") and based on wallclock time (absolute, "fire at 12 210in 10 seconds") and based on wallclock time (absolute, "fire at 12
209o'clock"). 211o'clock").
210 212
211While most event loops expect timers to specified in a relative way, they use 213While most event loops expect timers to specified in a relative way, they
212absolute time internally. This makes a difference when your clock "jumps", 214use absolute time internally. This makes a difference when your clock
213for 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
2142008-01-01, a watcher that you created to fire "after" a second might actually take 216the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215six years to finally fire. 217fire "after" a second might actually take six years to finally fire.
216 218
217AnyEvent cannot compensate for this. The only event loop that is conscious 219AnyEvent cannot compensate for this. The only event loop that is conscious
218about these issues is L<EV>, which offers both relative (ev_timer) and 220about these issues is L<EV>, which offers both relative (ev_timer, based
219absolute (ev_periodic) timers. 221on true relative time) and absolute (ev_periodic, based on wallclock time)
222timers.
220 223
221AnyEvent always prefers relative timers, if available, matching the 224AnyEvent always prefers relative timers, if available, matching the
222AnyEvent API. 225AnyEvent API.
223 226
224=head2 SIGNAL WATCHERS 227=head2 SIGNAL WATCHERS
225 228
226You can watch for signals using a signal watcher, C<signal> is the signal 229You can watch for signals using a signal watcher, C<signal> is the signal
227I<name> without any C<SIG> prefix, C<cb> is the Perl callback to 230I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
228be invoked whenever a signal occurs. 231be invoked whenever a signal occurs.
229 232
230Multiple signals occurances can be clumped together into one callback 233Multiple signal occurances can be clumped together into one callback
231invocation, and callback invocation will be synchronous. synchronous means 234invocation, and callback invocation will be synchronous. synchronous means
232that it might take a while until the signal gets handled by the process, 235that it might take a while until the signal gets handled by the process,
233but it is guarenteed not to interrupt any other callbacks. 236but it is guarenteed not to interrupt any other callbacks.
234 237
235The main advantage of using these watchers is that you can share a signal 238The main advantage of using these watchers is that you can share a signal
… …
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.
368 AnyEvent::Impl::POE based on POE, not generic enough for full support.
369
370There is no support for WxWidgets, as WxWidgets has no support for
371watching file handles. However, you can use WxWidgets through the
372POE Adaptor, as POE has a Wx backend that simply polls 20 times per
373second, which was considered to be too horrible to even consider for
374AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
375it's adaptor.
376
377AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
378autodetecting them.
365 379
366=item AnyEvent::detect 380=item AnyEvent::detect
367 381
368Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model 382Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
369if necessary. You should only call this function right before you would 383if necessary. You should only call this function right before you would
… …
420no warnings; 434no warnings;
421use strict; 435use strict;
422 436
423use Carp; 437use Carp;
424 438
425our $VERSION = '3.12'; 439our $VERSION = '3.3';
426our $MODEL; 440our $MODEL;
427 441
428our $AUTOLOAD; 442our $AUTOLOAD;
429our @ISA; 443our @ISA;
430 444
… …
437 [Coro::Event:: => AnyEvent::Impl::CoroEvent::], 451 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
438 [EV:: => AnyEvent::Impl::EV::], 452 [EV:: => AnyEvent::Impl::EV::],
439 [Event:: => AnyEvent::Impl::Event::], 453 [Event:: => AnyEvent::Impl::Event::],
440 [Glib:: => AnyEvent::Impl::Glib::], 454 [Glib:: => AnyEvent::Impl::Glib::],
441 [Tk:: => AnyEvent::Impl::Tk::], 455 [Tk:: => AnyEvent::Impl::Tk::],
456 [Wx:: => AnyEvent::Impl::POE::],
457 [Prima:: => AnyEvent::Impl::POE::],
442 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 458 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
443); 459 # everything below here will not be autoprobed as the pureperl backend should work everywhere
444my @models_detect = ( 460 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
445 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program 461 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
446 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy 462 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
447); 463);
448 464
449our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); 465our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
450 466
451sub detect() { 467sub detect() {
… …
455 if ($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 $verbose > 1;
476 } else {
477 warn "AnyEvent: unable to load model '$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
680By default, AnyEvent will be completely silent except in fatal
681conditions. You can set this environment variable to make AnyEvent more
682talkative.
683
684When set to C<1> or higher, causes AnyEvent to warn about unexpected
685conditions, such as not being able to load the event model specified by
686C<PERL_ANYEVENT_MODEL>.
687
662When set to C<2> or higher, cause AnyEvent to report to STDERR which event 688When set to C<2> or higher, cause AnyEvent to report to STDERR which event
663model it chooses. 689model 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
865
866=head1 BENCHMARK
867
868To give you an idea of the performance an doverheads that AnyEvent adds
869over the backends, here is a benchmark of various supported backends. The
870benchmark creates a lot of timers (with zero timeout) and io events
871(watching STDOUT, a pty, to become writable).
872
873Explanation of the fields:
874
875I<watcher> is the number of event watchers created/destroyed. Sicne
876different event models have vastly different performance each backend was
877handed a number of watchers so that overall runtime is acceptable and
878similar to all backends (and keep them from crashing).
879
880I<bytes> is the number of bytes (as measured by resident set size) used by
881each watcher.
882
883I<create> is the time, in microseconds, to create a single watcher.
884
885I<invoke> is the time, in microseconds, used to invoke a simple callback
886that simply counts down.
887
888I<destroy> is the time, in microseconds, to destroy a single watcher.
889
890 name watcher bytes create invoke destroy comment
891 EV/EV 400000 244 0.56 0.46 0.31 EV native interface
892 EV/Any 100000 610 3.52 0.91 0.75
893 CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal
894 Perl/Any 10000 654 4.64 1.22 0.77 pure perl implementation
895 Event/Event 10000 523 28.05 21.38 5.22 Event native interface
896 Event/Any 10000 943 34.43 20.48 1.39
897 Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour
898 Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers
899 POE/Select 2000 6343 94.69 807.65 562.69 POE::Loop::Select
900 POE/Event 2000 6644 108.15 768.19 14.33 POE::Loop::Event
901
902Discussion: The benchmark does I<not> bench scalability of the
903backend. For example a select-based backend (such as the pureperl one) can
904never compete with a backend using epoll. In this benchmark, only a single
905filehandle is used.
906
907EV is the sole leader regarding speed and memory use, which are both
908maximal/minimal. Even when going through AnyEvent, there is only one event
909loop that uses less memory (the Event module natively), and no faster
910event model.
911
912The pure perl implementation is hit in a few sweet spots (both the
913zero timeout and the use of a single fd hit optimisations in the perl
914interpreter and the backend itself), but it shows that it adds very little
915overhead in itself. Like any select-based backend it's performance becomes
916really bad with lots of file descriptors.
917
918The Event module has a relatively high setup and callback invocation cost,
919but overall scores on the third place.
920
921Glib has a little higher memory cost, a bit fster callback invocation and
922has a similar speed as Event.
923
924The Tk backend works relatively well, the fact that it crashes with
925more than 2000 watchers is a big setback, however, as correctness takes
926precedence over speed.
927
928POE, regardless of backend (wether it's pure perl select backend or the
929Event backend) shows abysmal performance and memory usage: Watchers use
930almost 30 times as much memory as EV watchers, and 10 times as much memory
931as both Event or EV via AnyEvent.
932
933Summary: using EV through AnyEvent is faster than any other event
934loop. The overhead AnyEvent adds can be very small, and you should avoid
935POE like the plague if you want performance or reasonable memory usage.
936
937
839=head1 FORK 938=head1 FORK
840 939
841Most event libraries are not fork-safe. The ones who are usually are 940Most event libraries are not fork-safe. The ones who are usually are
842because they are so inefficient. Only L<EV> is fully fork-aware. 941because they are so inefficient. Only L<EV> is fully fork-aware.
843 942
844If you have to fork, you must either do so I<before> creating your first 943If you have to fork, you must either do so I<before> creating your first
845watcher OR you must not use AnyEvent at all in the child. 944watcher OR you must not use AnyEvent at all in the child.
945
846 946
847=head1 SECURITY CONSIDERATIONS 947=head1 SECURITY CONSIDERATIONS
848 948
849AnyEvent can be forced to load any event model via 949AnyEvent can be forced to load any event model via
850$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to 950$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
… …
858 958
859 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 959 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
860 960
861 use AnyEvent; 961 use AnyEvent;
862 962
963
863=head1 SEE ALSO 964=head1 SEE ALSO
864 965
865Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, 966Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
866L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, 967L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
867L<Event::Lib>, L<Qt>. 968L<Event::Lib>, L<Qt>, L<POE>.
868 969
869Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, 970Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
870L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, 971L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
871L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, 972L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
872L<AnyEvent::Impl::Qt>. 973L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
873 974
874Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. 975Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
976
875 977
876=head1 AUTHOR 978=head1 AUTHOR
877 979
878 Marc Lehmann <schmorp@schmorp.de> 980 Marc Lehmann <schmorp@schmorp.de>
879 http://home.schmorp.de/ 981 http://home.schmorp.de/

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