--- AnyEvent/lib/AnyEvent.pm 2008/04/26 11:06:45 1.95 +++ AnyEvent/lib/AnyEvent.pm 2008/05/25 03:44:03 1.133 @@ -1,8 +1,8 @@ -=head1 NAME +=head1 => NAME AnyEvent - provide framework for multiple event loops -EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops +EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops =head1 SYNOPSIS @@ -17,8 +17,8 @@ }); my $w = AnyEvent->condvar; # stores whether a condition was flagged - $w->wait; # enters "main loop" till $condvar gets ->broadcast - $w->broadcast; # wake up current and all future wait's + $w->send; # wake up current and all future recv's + $w->recv; # enters "main loop" till $condvar gets ->send =head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) @@ -59,7 +59,7 @@ In addition to being free of having to use I, AnyEvent also is free of bloat and policy: with POE or similar -modules, you get an enourmous amount of code and strict rules you have to +modules, you get an enormous amount of code and strict rules you have to follow. AnyEvent, on the other hand, is lean and up to the point, by only offering the functionality that is necessary, in as thin as a wrapper as technically possible. @@ -68,7 +68,6 @@ useful) and you want to force your users to use the one and only event model, you should I use this module. - =head1 DESCRIPTION L provides an identical interface to multiple event loops. This @@ -81,7 +80,7 @@ During the first call of any watcher-creation method, the module tries to detect the currently loaded event loop by probing whether one of the -following modules is already loaded: L, L, L, +following modules is already loaded: L, L, L, L, L, L, L, L. The first one found is used. If none are found, the module tries to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl @@ -111,7 +110,7 @@ AnyEvent has the central concept of a I, which is an object that stores relevant data for each kind of event you are waiting for, such as -the callback to call, the filehandle to watch, etc. +the callback to call, the file handle to watch, etc. These watchers are normal Perl objects with normal Perl lifetime. After creating a watcher it will immediately "watch" for events and invoke the @@ -240,10 +239,10 @@ presence is undefined and you cannot rely on them. Portable AnyEvent callbacks cannot use arguments passed to signal watcher callbacks. -Multiple signal occurances can be clumped together into one callback -invocation, and callback invocation will be synchronous. synchronous means +Multiple signal occurrences can be clumped together into one callback +invocation, and callback invocation will be synchronous. Synchronous means that it might take a while until the signal gets handled by the process, -but it is guarenteed not to interrupt any other callbacks. +but it is guaranteed not to interrupt any other callbacks. The main advantage of using these watchers is that you can share a signal between multiple watchers. @@ -282,8 +281,6 @@ my $done = AnyEvent->condvar; - AnyEvent::detect; # force event module to be initialised - my $pid = fork or exit 5; my $w = AnyEvent->child ( @@ -291,48 +288,199 @@ cb => sub { my ($pid, $status) = @_; warn "pid $pid exited with status $status"; - $done->broadcast; + $done->send; }, ); # do something else, then wait for process exit - $done->wait; + $done->recv; =head2 CONDITION VARIABLES -Condition variables can be created by calling the C<< AnyEvent->condvar >> -method without any arguments. - -A condition variable waits for a condition - precisely that the C<< -->broadcast >> method has been called. +If you are familiar with some event loops you will know that all of them +require you to run some blocking "loop", "run" or similar function that +will actively watch for new events and call your callbacks. + +AnyEvent is different, it expects somebody else to run the event loop and +will only block when necessary (usually when told by the user). + +The instrument to do that is called a "condition variable", so called +because they represent a condition that must become true. + +Condition variables can be created by calling the C<< AnyEvent->condvar +>> method, usually without arguments. The only argument pair allowed is +C, which specifies a callback to be called when the condition variable +becomes true. + +After creation, the condition variable is "false" until it becomes "true" +by calling the C method (or calling the condition variable as if it +were a callback). + +Condition variables are similar to callbacks, except that you can +optionally wait for them. They can also be called merge points - points +in time where multiple outstanding events have been processed. And yet +another way to call them is transactions - each condition variable can be +used to represent a transaction, which finishes at some point and delivers +a result. -They are very useful to signal that a condition has been fulfilled, for -example, if you write a module that does asynchronous http requests, +Condition variables are very useful to signal that something has finished, +for example, if you write a module that does asynchronous http requests, then a condition variable would be the ideal candidate to signal the -availability of results. +availability of results. The user can either act when the callback is +called or can synchronously C<< ->recv >> for the results. -You can also use condition variables to block your main program until -an event occurs - for example, you could C<< ->wait >> in your main -program until the user clicks the Quit button in your app, which would C<< -->broadcast >> the "quit" event. +You can also use them to simulate traditional event loops - for example, +you can block your main program until an event occurs - for example, you +could C<< ->recv >> in your main program until the user clicks the Quit +button of your app, which would C<< ->send >> the "quit" event. Note that condition variables recurse into the event loop - if you have -two pirces of code that call C<< ->wait >> in a round-robbin fashion, you +two pieces of code that call C<< ->recv >> in a round-robin fashion, you lose. Therefore, condition variables are good to export to your caller, but you should avoid making a blocking wait yourself, at least in callbacks, as this asks for trouble. -This object has two methods: +Condition variables are represented by hash refs in perl, and the keys +used by AnyEvent itself are all named C<_ae_XXX> to make subclassing +easy (it is often useful to build your own transaction class on top of +AnyEvent). To subclass, use C as base class and call +it's C method in your own C method. + +There are two "sides" to a condition variable - the "producer side" which +eventually calls C<< -> send >>, and the "consumer side", which waits +for the send to occur. + +Example: wait for a timer. + + # wait till the result is ready + my $result_ready = AnyEvent->condvar; + + # do something such as adding a timer + # or socket watcher the calls $result_ready->send + # when the "result" is ready. + # in this case, we simply use a timer: + my $w = AnyEvent->timer ( + after => 1, + cb => sub { $result_ready->send }, + ); + + # this "blocks" (while handling events) till the callback + # calls send + $result_ready->recv; + +Example: wait for a timer, but take advantage of the fact that +condition variables are also code references. + + my $done = AnyEvent->condvar; + my $delay = AnyEvent->timer (after => 5, cb => $done); + $done->recv; + +=head3 METHODS FOR PRODUCERS + +These methods should only be used by the producing side, i.e. the +code/module that eventually sends the signal. Note that it is also +the producer side which creates the condvar in most cases, but it isn't +uncommon for the consumer to create it as well. + +=over 4 + +=item $cv->send (...) + +Flag the condition as ready - a running C<< ->recv >> and all further +calls to C will (eventually) return after this method has been +called. If nobody is waiting the send will be remembered. + +If a callback has been set on the condition variable, it is called +immediately from within send. + +Any arguments passed to the C call will be returned by all +future C<< ->recv >> calls. + +Condition variables are overloaded so one can call them directly (as a +code reference). Calling them directly is the same as calling C. + +=item $cv->croak ($error) + +Similar to send, but causes all call's to C<< ->recv >> to invoke +C with the given error message/object/scalar. + +This can be used to signal any errors to the condition variable +user/consumer. + +=item $cv->begin ([group callback]) + +=item $cv->end + +These two methods are EXPERIMENTAL and MIGHT CHANGE. + +These two methods can be used to combine many transactions/events into +one. For example, a function that pings many hosts in parallel might want +to use a condition variable for the whole process. + +Every call to C<< ->begin >> will increment a counter, and every call to +C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end +>>, the (last) callback passed to C will be executed. That callback +is I to call C<< ->send >>, but that is not required. If no +callback was set, C will be called without any arguments. + +Let's clarify this with the ping example: + + my $cv = AnyEvent->condvar; + + my %result; + $cv->begin (sub { $cv->send (\%result) }); + + for my $host (@list_of_hosts) { + $cv->begin; + ping_host_then_call_callback $host, sub { + $result{$host} = ...; + $cv->end; + }; + } + + $cv->end; + +This code fragment supposedly pings a number of hosts and calls +C after results for all then have have been gathered - in any +order. To achieve this, the code issues a call to C when it starts +each ping request and calls C when it has received some result for +it. Since C and C only maintain a counter, the order in which +results arrive is not relevant. + +There is an additional bracketing call to C and C outside the +loop, which serves two important purposes: first, it sets the callback +to be called once the counter reaches C<0>, and second, it ensures that +C is called even when C hosts are being pinged (the loop +doesn't execute once). + +This is the general pattern when you "fan out" into multiple subrequests: +use an outer C/C pair to set the callback and ensure C +is called at least once, and then, for each subrequest you start, call +C and for each subrequest you finish, call C. + +=back + +=head3 METHODS FOR CONSUMERS + +These methods should only be used by the consuming side, i.e. the +code awaits the condition. =over 4 -=item $cv->wait +=item $cv->recv + +Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak +>> methods have been called on c<$cv>, while servicing other watchers +normally. -Wait (blocking if necessary) until the C<< ->broadcast >> method has been -called on c<$cv>, while servicing other watchers normally. +You can only wait once on a condition - additional calls are valid but +will return immediately. -You can only wait once on a condition - additional calls will return -immediately. +If an error condition has been set by calling C<< ->croak >>, then this +function will call C. + +In list context, all parameters passed to C will be returned, +in scalar context only the first one will be returned. Not all event models support a blocking wait - some die in that case (programs might want to do that to stay interactive), so I to C<< ->wait >> in a module is that you cannot -sensibly have two C<< ->wait >>'s in parallel, as that would require +Another reason I to C<< ->recv >> in a module is that you cannot +sensibly have two C<< ->recv >>'s in parallel, as that would require multiple interpreters or coroutines/threads, none of which C -can supply (the coroutine-aware backends L and -L explicitly support concurrent C<< ->wait >>'s -from different coroutines, however). - -=item $cv->broadcast - -Flag the condition as ready - a running C<< ->wait >> and all further -calls to C will (eventually) return after this method has been -called. If nobody is waiting the broadcast will be remembered.. +can supply. + +The L module, however, I and I supply coroutines and, in +fact, L replaces AnyEvent's condvars by coroutine-safe +versions and also integrates coroutines into AnyEvent, making blocking +C<< ->recv >> calls perfectly safe as long as they are done from another +coroutine (one that doesn't run the event loop). + +You can ensure that C<< -recv >> never blocks by setting a callback and +only calling C<< ->recv >> from within that callback (or at a later +time). This will work even when the event loop does not support blocking +waits otherwise. + +=item $bool = $cv->ready + +Returns true when the condition is "true", i.e. whether C or +C have been called. + +=item $cb = $cv->cb ([new callback]) + +This is a mutator function that returns the callback set and optionally +replaces it before doing so. + +The callback will be called when the condition becomes "true", i.e. when +C or C are called. Calling C inside the callback +or at any later time is guaranteed not to block. =back -Example: +=head3 MAINLOOP EMULATION - # wait till the result is ready - my $result_ready = AnyEvent->condvar; +Sometimes (often for short test scripts, or even standalone programs +who only want to use AnyEvent), you I want your program to block +indefinitely in some event loop. - # do something such as adding a timer - # or socket watcher the calls $result_ready->broadcast - # when the "result" is ready. - # in this case, we simply use a timer: - my $w = AnyEvent->timer ( - after => 1, - cb => sub { $result_ready->broadcast }, - ); +In that case, you cna use a condition variable like this: + + AnyEvent->condvar->recv; + +This has the effect of entering the event loop and looping forever. + +Note that usually your program has some exit condition, in which case +it is better to use the "traditional" approach of storing a condition +variable, waiting for it, and sending it when the program should exit +cleanly. - # this "blocks" (while handling events) till the watcher - # calls broadcast - $result_ready->wait; =head1 GLOBAL VARIABLES AND FUNCTIONS @@ -389,12 +554,10 @@ The known classes so far are: - AnyEvent::Impl::CoroEV based on Coro::EV, best choice. - AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. AnyEvent::Impl::EV based on EV (an interface to libev, best choice). AnyEvent::Impl::Event based on Event, second best choice. + AnyEvent::Impl::Perl pure-perl implementation, fast and portable. AnyEvent::Impl::Glib based on Glib, third-best choice. - AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. AnyEvent::Impl::Tk based on Tk, very bad choice. AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. @@ -417,6 +580,27 @@ have created an AnyEvent watcher anyway, that is, as late as possible at runtime. +=item $guard = AnyEvent::post_detect { BLOCK } + +Arranges for the code block to be executed as soon as the event model is +autodetected (or immediately if this has already happened). + +If called in scalar or list context, then it creates and returns an object +that automatically removes the callback again when it is destroyed. See +L for a case where this is useful. + +=item @AnyEvent::post_detect + +If there are any code references in this array (you can C to it +before or after loading AnyEvent), then they will called directly after +the event loop has been chosen. + +You should check C<$AnyEvent::MODEL> before adding to this array, though: +if it contains a true value then the event loop has already been detected, +and the array will be ignored. + +Best use C instead. + =back =head1 WHAT TO DO IN A MODULE @@ -429,14 +613,14 @@ by calling AnyEvent in your module body you force the user of your module to load the event module first. -Never call C<< ->wait >> on a condition variable unless you I that -the C<< ->broadcast >> method has been called on it already. This is +Never call C<< ->recv >> on a condition variable unless you I that +the C<< ->send >> method has been called on it already. This is because it will stall the whole program, and the whole point of using events is to stay interactive. -It is fine, however, to call C<< ->wait >> when the user of your module +It is fine, however, to call C<< ->recv >> when the user of your module requests it (i.e. if you create a http request object ad have a method -called C that returns the results, it should call C<< ->wait >> +called C that returns the results, it should call C<< ->recv >> freely, as the user of your module knows what she is doing. always). =head1 WHAT TO DO IN THE MAIN PROGRAM @@ -460,6 +644,80 @@ loading the C module, which gives you similar behaviour everywhere, but letting AnyEvent chose is generally better. +=head1 OTHER MODULES + +The following is a non-exhaustive list of additional modules that use +AnyEvent and can therefore be mixed easily with other AnyEvent modules +in the same program. Some of the modules come with AnyEvent, some are +available via CPAN. + +=over 4 + +=item L + +Contains various utility functions that replace often-used but blocking +functions such as C by event-/callback-based versions. + +=item L + +Provide read and write buffers and manages watchers for reads and writes. + +=item L + +Provides various utility functions for (internet protocol) sockets, +addresses and name resolution. Also functions to create non-blocking tcp +connections or tcp servers, with IPv6 and SRV record support and more. + +=item L + +Provides a simple web application server framework. + +=item L + +Provides rich asynchronous DNS resolver capabilities. + +=item L + +The fastest ping in the west. + +=item L + +AnyEvent based IRC client module family. + +=item L + +AnyEvent based XMPP (Jabber protocol) module family. + +=item L + +AnyEvent-based implementation of the Freenet Client Protocol, birthplace +of AnyEvent. + +=item L + +High level API for event-based execution flow control. + +=item L + +Has special support for AnyEvent via L. + +=item L, L + +Truly asynchronous I/O, should be in the toolbox of every event +programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent +together. + +=item L, L + +Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses +IO::AIO and AnyEvent together. + +=item L + +The lambda approach to I/O - don't ask, look there. Can use AnyEvent. + +=back + =cut package AnyEvent; @@ -469,7 +727,7 @@ use Carp; -our $VERSION = '3.3'; +our $VERSION = '4.03'; our $MODEL; our $AUTOLOAD; @@ -479,23 +737,51 @@ our @REGISTRY; +our %PROTOCOL; # (ipv4|ipv6) => (1|2) + +{ + my $idx; + $PROTOCOL{$_} = ++$idx + for split /\s*,\s*/, $ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6"; +} + my @models = ( - [Coro::EV:: => AnyEvent::Impl::CoroEV::], - [Coro::Event:: => AnyEvent::Impl::CoroEvent::], [EV:: => AnyEvent::Impl::EV::], [Event:: => AnyEvent::Impl::Event::], - [Glib:: => AnyEvent::Impl::Glib::], [Tk:: => AnyEvent::Impl::Tk::], [Wx:: => AnyEvent::Impl::POE::], [Prima:: => AnyEvent::Impl::POE::], [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], # everything below here will not be autoprobed as the pureperl backend should work everywhere + [Glib:: => AnyEvent::Impl::Glib::], [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy [Qt:: => AnyEvent::Impl::Qt::], # requires special main program [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza ); -our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); +our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY); + +our @post_detect; + +sub post_detect(&) { + my ($cb) = @_; + + if ($MODEL) { + $cb->(); + + 1 + } else { + push @post_detect, $cb; + + defined wantarray + ? bless \$cb, "AnyEvent::Util::PostDetect" + : () + } +} + +sub AnyEvent::Util::PostDetect::DESTROY { + @post_detect = grep $_ != ${$_[0]}, @post_detect; +} sub detect() { unless ($MODEL) { @@ -539,12 +825,14 @@ } $MODEL - or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib."; + or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib."; } } unshift @ISA, $MODEL; push @{"$MODEL\::ISA"}, "AnyEvent::Base"; + + (shift @post_detect)->() while @post_detect; } $MODEL @@ -564,18 +852,10 @@ package AnyEvent::Base; -# default implementation for ->condvar, ->wait, ->broadcast +# default implementation for ->condvar sub condvar { - bless \my $flag, "AnyEvent::Base::CondVar" -} - -sub AnyEvent::Base::CondVar::broadcast { - ${$_[0]}++; -} - -sub AnyEvent::Base::CondVar::wait { - AnyEvent->one_event while !${$_[0]}; + bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar:: } # default implementation for ->signal @@ -659,6 +939,66 @@ undef $CHLD_W unless keys %PID_CB; } +package AnyEvent::CondVar; + +our @ISA = AnyEvent::CondVar::Base::; + +package AnyEvent::CondVar::Base; + +use overload + '&{}' => sub { my $self = shift; sub { $self->send (@_) } }, + fallback => 1; + +sub _send { + # nop +} + +sub send { + my $cv = shift; + $cv->{_ae_sent} = [@_]; + (delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb}; + $cv->_send; +} + +sub croak { + $_[0]{_ae_croak} = $_[1]; + $_[0]->send; +} + +sub ready { + $_[0]{_ae_sent} +} + +sub _wait { + AnyEvent->one_event while !$_[0]{_ae_sent}; +} + +sub recv { + $_[0]->_wait; + + Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak}; + wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0] +} + +sub cb { + $_[0]{_ae_cb} = $_[1] if @_ > 1; + $_[0]{_ae_cb} +} + +sub begin { + ++$_[0]{_ae_counter}; + $_[0]{_ae_end_cb} = $_[1] if @_ > 1; +} + +sub end { + return if --$_[0]{_ae_counter}; + &{ $_[0]{_ae_end_cb} || sub { $_[0]->send } }; +} + +# undocumented/compatibility with pre-3.4 +*broadcast = \&send; +*wait = \&_wait; + =head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE This is an advanced topic that you do not normally need to use AnyEvent in @@ -724,11 +1064,11 @@ =item C This can be used to specify the event model to be used by AnyEvent, before -autodetection and -probing kicks in. It must be a string consisting +auto detection and -probing kicks in. It must be a string consisting entirely of ASCII letters. The string C gets prepended and the resulting module name is loaded and if the load was successful, used as event model. If it fails to load AnyEvent will proceed with -autodetection and -probing. +auto detection and -probing. This functionality might change in future versions. @@ -737,6 +1077,37 @@ PERL_ANYEVENT_MODEL=Perl perl ... +=item C + +Used by both L and L to determine preferences +for IPv4 or IPv6. The default is unspecified (and might change, or be the result +of auto probing). + +Must be set to a comma-separated list of protocols or address families, +current supported: C and C. Only protocols mentioned will be +used, and preference will be given to protocols mentioned earlier in the +list. + +This variable can effectively be used for denial-of-service attacks +against local programs (e.g. when setuid), although the impact is likely +small, as the program has to handle connection errors already- + +Examples: C - prefer IPv4 over IPv6, +but support both and try to use both. C +- only support IPv4, never try to resolve or contact IPv6 +addresses. C support either IPv4 or +IPv6, but prefer IPv6 over IPv4. + +=item C + +Used by L to decide whether to use the EDNS0 extension +for DNS. This extension is generally useful to reduce DNS traffic, but +some (broken) firewalls drop such DNS packets, which is why it is off by +default. + +Setting this variable to C<1> will cause L to announce +EDNS0 in its DNS requests. + =back =head1 EXAMPLE PROGRAM @@ -756,7 +1127,7 @@ warn "io event <$_[0]>\n"; # will always output chomp (my $input = ); # read a line warn "read: $input\n"; # output what has been read - $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i + $cv->send if $input =~ /^q/i; # quit program if /^q/i }, ); @@ -771,7 +1142,7 @@ new_timer; # create first timer - $cv->wait; # wait until user enters /^q/i + $cv->recv; # wait until user enters /^q/i =head1 REAL-WORLD EXAMPLE @@ -831,13 +1202,13 @@ $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); Again, C waits till all data has arrived, and then stores the -result and signals any possible waiters that the request ahs finished: +result and signals any possible waiters that the request has finished: sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; if (end-of-file or data complete) { $txn->{result} = $txn->{buf}; - $txn->{finished}->broadcast; + $txn->{finished}->send; $txb->{cb}->($txn) of $txn->{cb}; # also call callback } @@ -845,11 +1216,11 @@ request was already finished, it doesn't wait, of course, and returns the data: - $txn->{finished}->wait; + $txn->{finished}->recv; return $txn->{result}; The actual code goes further and collects all errors (Cs, exceptions) -that occured during request processing. The C method detects +that occurred during request processing. The C method detects whether an exception as thrown (it is stored inside the $txn object) and just throws the exception, which means connection errors and other problems get reported tot he code that tries to use the result, not in a @@ -890,10 +1261,10 @@ $fcp->txn_client_get ($url)->cb (sub { ... - $quit->broadcast; + $quit->send; }); - $quit->wait; + $quit->recv; =head1 BENCHMARKS @@ -905,7 +1276,7 @@ =head2 BENCHMARKING ANYEVENT OVERHEAD Here is a benchmark of various supported event models used natively and -through anyevent. The benchmark creates a lot of timers (with a zero +through AnyEvent. The benchmark creates a lot of timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to become writable, which it is), lets them fire exactly once and destroys them again. @@ -932,7 +1303,7 @@ I is the time, in microseconds, used to invoke a simple callback. The callback simply counts down a Perl variable and after it was -invoked "watcher" times, it would C<< ->broadcast >> a condvar once to +invoked "watcher" times, it would C<< ->send >> a condvar once to signal the end of this phase. I is the time, in microseconds, that it takes to destroy a single @@ -946,7 +1317,7 @@ CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation Event/Event 16000 516 31.88 31.30 0.85 Event native interface - Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers + Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event @@ -966,6 +1337,11 @@ the time - usually it takes longer. This puts event loops tested with a higher number of watchers at a disadvantage. +To put the range of results into perspective, consider that on the +benchmark machine, handling an event takes roughly 1600 CPU cycles with +EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU +cycles with POE. + C is the sole leader regarding speed and memory use, which are both maximal/minimal, respectively. Even when going through AnyEvent, it uses far less memory than any other event loop and is still faster than Event @@ -997,17 +1373,22 @@ hidden memory cost inside the kernel which is not reflected in the figures above). -C, regardless of underlying event loop (whether using its pure -perl select-based backend or the Event module, the POE-EV backend -couldn't be tested because it wasn't working) shows abysmal performance -and memory usage: Watchers use almost 30 times as much memory as -EV watchers, and 10 times as much memory as Event (the high memory +C, regardless of underlying event loop (whether using its pure perl +select-based backend or the Event module, the POE-EV backend couldn't +be tested because it wasn't working) shows abysmal performance and +memory usage with AnyEvent: Watchers use almost 30 times as much memory +as EV watchers, and 10 times as much memory as Event (the high memory requirements are caused by requiring a session for each watcher). Watcher invocation speed is almost 900 times slower than with AnyEvent's pure perl -implementation. The design of the POE adaptor class in AnyEvent can not -really account for this, as session creation overhead is small compared -to execution of the state machine, which is coded pretty optimally within -L. POE simply seems to be abysmally slow. +implementation. + +The design of the POE adaptor class in AnyEvent can not really account +for the performance issues, though, as session creation overhead is +small compared to execution of the state machine, which is coded pretty +optimally within L (and while everybody agrees that +using multiple sessions is not a good approach, especially regarding +memory usage, even the author of POE could not come up with a faster +design). =head3 Summary @@ -1028,19 +1409,19 @@ =head2 BENCHMARKING THE LARGE SERVER CASE -This benchmark atcually benchmarks the event loop itself. It works by -creating a number of "servers": each server consists of a socketpair, a +This benchmark actually benchmarks the event loop itself. It works by +creating a number of "servers": each server consists of a socket pair, a timeout watcher that gets reset on activity (but never fires), and an I/O watcher waiting for input on one side of the socket. Each time the socket watcher reads a byte it will write that byte to a random other "server". The effect is that there will be a lot of I/O watchers, only part of which are active at any one point (so there is a constant number of active -fds for each loop iterstaion, but which fds these are is random). The +fds for each loop iteration, but which fds these are is random). The timeout is reset each time something is read because that reflects how most timeouts work (and puts extra pressure on the event loops). -In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100 +In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100 (1%) are active. This mirrors the activity of large servers with many connections, most of which are idle at any one point in time. @@ -1052,7 +1433,7 @@ I is the number of sockets, and twice the number of "servers" (as each server has a read and write socket end). -I is the time it takes to create a socketpair (which is +I is the time it takes to create a socket pair (which is nontrivial) and two watchers: an I/O watcher and a timeout watcher. I, the most important value, is the time it takes to handle a @@ -1064,7 +1445,7 @@ name sockets create request EV 20000 69.01 11.16 - Perl 20000 75.28 112.76 + Perl 20000 73.32 35.87 Event 20000 212.62 257.32 Glib 20000 651.16 1896.30 POE 20000 349.67 12317.24 uses POE::Loop::Event @@ -1096,8 +1477,7 @@ =over 4 -=item * The pure perl implementation performs extremely well, considering -that it uses select. +=item * The pure perl implementation performs extremely well. =item * Avoid Glib or POE in large projects where performance matters. @@ -1120,9 +1500,9 @@ name sockets create request EV 16 20.00 6.54 + Perl 16 25.75 12.62 Event 16 81.27 35.86 Glib 16 32.63 15.48 - Perl 16 24.62 162.37 POE 16 261.87 276.28 uses POE::Loop::Event =head3 Discussion @@ -1130,18 +1510,17 @@ The benchmark tries to test the performance of a typical small server. While knowing how various event loops perform is interesting, keep in mind that their overhead in this case is usually not as important, due -to the small absolute number of watchers. +to the small absolute number of watchers (that is, you need efficiency and +speed most when you have lots of watchers, not when you only have a few of +them). EV is again fastest. -The C-based event loops Event and Glib come in second this time, as the -overhead of running an iteration is much smaller in C than in Perl (little -code to execute in the inner loop, and perl's function calling overhead is -high, and updating all the data structures is costly). - -The pure perl event loop is much slower, but still competitive. +Perl again comes second. It is noticeably faster than the C-based event +loops Event and Glib, although the difference is too small to really +matter. -POE also performs much better in this case, but is is stillf ar behind the +POE also performs much better in this case, but is is still far behind the others. =head3 Summary @@ -1157,7 +1536,8 @@ =head1 FORK Most event libraries are not fork-safe. The ones who are usually are -because they are so inefficient. Only L is fully fork-aware. +because they rely on inefficient but fork-safe C