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Revision 1.59 by root, Thu Apr 24 08:38:13 2008 UTC vs.
Revision 1.68 by root, Fri Apr 25 07:14:33 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
… …
78 78
79The interface itself is vaguely similar, but not identical to the L<Event> 79The interface itself is vaguely similar, but not identical to the L<Event>
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 83to detect the currently loaded event loop by probing whether one of the
84the following modules is already loaded: L<Coro::EV>, L<Coro::Event>, 84following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
85L<EV>, L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>. The first one 85L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,
86found is used. If none are found, the module tries to load these modules 86L<POE>. The first one found is used. If none are found, the module tries
87(excluding Event::Lib and Qt) in the order given. The first one that can 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
88be successfully loaded will be used. If, after this, still none could be 89be successfully loaded will be used. If, after this, still none could be
89found, AnyEvent will fall back to a pure-perl event loop, which is not 90found, AnyEvent will fall back to a pure-perl event loop, which is not
90very efficient, but should work everywhere. 91very efficient, but should work everywhere.
91 92
92Because AnyEvent first checks for modules that are already loaded, loading 93Because AnyEvent first checks for modules that are already loaded, loading
… …
362 AnyEvent::Impl::Glib based on Glib, third-best choice. 363 AnyEvent::Impl::Glib based on Glib, third-best choice.
363 AnyEvent::Impl::Tk based on Tk, very bad choice. 364 AnyEvent::Impl::Tk based on Tk, very bad choice.
364 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. 365 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
365 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).
366 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.
367 379
368=item AnyEvent::detect 380=item AnyEvent::detect
369 381
370Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model 382Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
371if necessary. You should only call this function right before you would 383if necessary. You should only call this function right before you would
… …
422no warnings; 434no warnings;
423use strict; 435use strict;
424 436
425use Carp; 437use Carp;
426 438
427our $VERSION = '3.2'; 439our $VERSION = '3.3';
428our $MODEL; 440our $MODEL;
429 441
430our $AUTOLOAD; 442our $AUTOLOAD;
431our @ISA; 443our @ISA;
432 444
… …
439 [Coro::Event:: => AnyEvent::Impl::CoroEvent::], 451 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
440 [EV:: => AnyEvent::Impl::EV::], 452 [EV:: => AnyEvent::Impl::EV::],
441 [Event:: => AnyEvent::Impl::Event::], 453 [Event:: => AnyEvent::Impl::Event::],
442 [Glib:: => AnyEvent::Impl::Glib::], 454 [Glib:: => AnyEvent::Impl::Glib::],
443 [Tk:: => AnyEvent::Impl::Tk::], 455 [Tk:: => AnyEvent::Impl::Tk::],
456 [Wx:: => AnyEvent::Impl::POE::],
457 [Prima:: => AnyEvent::Impl::POE::],
444 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 458 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
445); 459 # everything below here will not be autoprobed as the pureperl backend should work everywhere
446my @models_detect = ( 460 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
447 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program 461 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
448 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy 462 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
449); 463);
450 464
451our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); 465our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
452 466
453sub detect() { 467sub detect() {
… …
457 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { 471 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
458 my $model = "AnyEvent::Impl::$1"; 472 my $model = "AnyEvent::Impl::$1";
459 if (eval "require $model") { 473 if (eval "require $model") {
460 $MODEL = $model; 474 $MODEL = $model;
461 warn "AnyEvent: loaded model '$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 $verbose;
462 } 478 }
463 } 479 }
464 480
465 # check for already loaded models 481 # check for already loaded models
466 unless ($MODEL) { 482 unless ($MODEL) {
467 for (@REGISTRY, @models, @models_detect) { 483 for (@REGISTRY, @models) {
468 my ($package, $model) = @$_; 484 my ($package, $model) = @$_;
469 if (${"$package\::VERSION"} > 0) { 485 if (${"$package\::VERSION"} > 0) {
470 if (eval "require $model") { 486 if (eval "require $model") {
471 $MODEL = $model; 487 $MODEL = $model;
472 warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1; 488 warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
… …
659 675
660=over 4 676=over 4
661 677
662=item C<PERL_ANYEVENT_VERBOSE> 678=item C<PERL_ANYEVENT_VERBOSE>
663 679
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
664When 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
665model it chooses. 689model it chooses.
666 690
667=item C<PERL_ANYEVENT_MODEL> 691=item C<PERL_ANYEVENT_MODEL>
668 692
… …
836 $quit->broadcast; 860 $quit->broadcast;
837 }); 861 });
838 862
839 $quit->wait; 863 $quit->wait;
840 864
865
866=head1 BENCHMARK
867
868To give you an idea of the performance and overheads that AnyEvent adds
869over the event loops directly, here is a benchmark of various supported
870event models natively and with anyevent. The benchmark creates a lot of
871timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to
872become writable, which it is), lets them fire exactly once and destroys
873them again.
874
875=head2 Explanation of the fields
876
877I<watcher> is the number of event watchers created/destroyed. Since
878different event models feature vastly different performances, each event
879loop was given a number of watchers so that overall runtime is acceptable
880and similar between tested event loop (and keep them from crashing): Glib
881would probably take thousands of years if asked to process the same number
882of watchers as EV in this benchmark.
883
884I<bytes> is the number of bytes (as measured by the resident set size,
885RSS) consumed by each watcher. This method of measuring captures both C
886and Perl-based overheads.
887
888I<create> is the time, in microseconds (millionths of seconds), that it
889takes to create a single watcher. The callback is a closure shared between
890all watchers, to avoid adding memory overhead. That means closure creation
891and memory usage is not included in the figures.
892
893I<invoke> is the time, in microseconds, used to invoke a simple
894callback. The callback simply counts down a Perl variable and after it was
895invoked "watcher" times, it would C<< ->broadcast >> a condvar once.
896
897I<destroy> is the time, in microseconds, that it takes destroy a single
898watcher.
899
900=head2 Results
901
902 name watcher bytes create invoke destroy comment
903 EV/EV 400000 244 0.56 0.46 0.31 EV native interface
904 EV/Any 100000 610 3.52 0.91 0.75
905 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
907 Event/Event 10000 523 28.05 21.38 5.22 Event native interface
908 Event/Any 10000 943 34.43 20.48 1.39
909 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
911 POE/Select 2000 6343 94.69 807.65 562.69 POE::Loop::Select
912 POE/Event 2000 6644 108.15 768.19 14.33 POE::Loop::Event
913
914=head2 Discussion
915
916The 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)
918can never compete with an event loop that uses epoll when the number of
919file descriptors grows high. In this benchmark, only a single filehandle
920is used (although some of the AnyEvent adaptors dup() its file descriptor
921to worka round bugs).
922
923C<EV> is the sole leader regarding speed and memory use, which are both
924maximal/minimal, respectively. Even when going through AnyEvent, there is
925only one event loop that uses less memory (the C<Event> module natively), and
926no faster event model, not event C<Event> natively.
927
928The pure perl implementation is hit in a few sweet spots (both the
929zero timeout and the use of a single fd hit optimisations in the perl
930interpreter and the backend itself). Nevertheless tis shows that it
931adds very little overhead in itself. Like any select-based backend its
932performance becomes really bad with lots of file descriptors, of course,
933but this was not subjetc of this benchmark.
934
935The C<Event> module has a relatively high setup and callback invocation cost,
936but overall scores on the third place.
937
938C<Glib>'s memory usage is quite a bit bit higher, features a faster
939callback invocation and overall lands in the same class as C<Event>.
940
941The C<Tk> adaptor works relatively well, the fact that it crashes with
942more than 2000 watchers is a big setback, however, as correctness takes
943precedence over speed. Nevertheless, its performance is surprising, as the
944file 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
946hidden memory cost inside the kernel, though).
947
948C<POE>, regardless of backend (wether using its pure perl select-based
949backend or the Event backend) shows abysmal performance and memory
950usage: Watchers use almost 30 times as much memory as EV watchers, and 10
951times as much memory as both Event or EV via AnyEvent. Watcher invocation
952is almost 700 times slower as with AnyEvent's pure perl implementation.
953
954Summary: using EV through AnyEvent is faster than any other event
955loop. The overhead AnyEvent adds can be very small, and you should avoid
956POE like the plague if you want performance or reasonable memory usage.
957
958
841=head1 FORK 959=head1 FORK
842 960
843Most event libraries are not fork-safe. The ones who are usually are 961Most event libraries are not fork-safe. The ones who are usually are
844because they are so inefficient. Only L<EV> is fully fork-aware. 962because they are so inefficient. Only L<EV> is fully fork-aware.
845 963
846If you have to fork, you must either do so I<before> creating your first 964If you have to fork, you must either do so I<before> creating your first
847watcher OR you must not use AnyEvent at all in the child. 965watcher OR you must not use AnyEvent at all in the child.
966
848 967
849=head1 SECURITY CONSIDERATIONS 968=head1 SECURITY CONSIDERATIONS
850 969
851AnyEvent can be forced to load any event model via 970AnyEvent can be forced to load any event model via
852$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to 971$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
… …
860 979
861 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 980 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
862 981
863 use AnyEvent; 982 use AnyEvent;
864 983
984
865=head1 SEE ALSO 985=head1 SEE ALSO
866 986
867Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, 987Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
868L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, 988L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
869L<Event::Lib>, L<Qt>. 989L<Event::Lib>, L<Qt>, L<POE>.
870 990
871Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, 991Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
872L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, 992L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
873L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, 993L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
874L<AnyEvent::Impl::Qt>. 994L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
875 995
876Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. 996Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
997
877 998
878=head1 AUTHOR 999=head1 AUTHOR
879 1000
880 Marc Lehmann <schmorp@schmorp.de> 1001 Marc Lehmann <schmorp@schmorp.de>
881 http://home.schmorp.de/ 1002 http://home.schmorp.de/

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