… | |
… | |
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>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>, |
85 | L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>, |
86 | L<POE>. The first one found is used. If none are found, the module tries |
86 | L<POE>. The first one found is used. If none are found, the module tries |
87 | to load these modules (excluding Event::Lib, Qt and POE as the pure perl |
87 | to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl |
88 | adaptor should always succeed) in the order given. The first one that can |
88 | adaptor should always succeed) in the order given. The first one that can |
89 | be successfully loaded will be used. If, after this, still none could be |
89 | be successfully loaded will be used. If, after this, still none could be |
90 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
90 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
91 | very efficient, but should work everywhere. |
91 | very efficient, but should work everywhere. |
92 | |
92 | |
… | |
… | |
136 | |
136 | |
137 | Note that C<my $w; $w => combination. This is necessary because in Perl, |
137 | Note that C<my $w; $w => combination. This is necessary because in Perl, |
138 | my variables are only visible after the statement in which they are |
138 | my variables are only visible after the statement in which they are |
139 | declared. |
139 | declared. |
140 | |
140 | |
141 | =head2 IO WATCHERS |
141 | =head2 I/O WATCHERS |
142 | |
142 | |
143 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
143 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
144 | with the following mandatory key-value pairs as arguments: |
144 | with the following mandatory key-value pairs as arguments: |
145 | |
145 | |
146 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for |
146 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch |
147 | events. C<poll> must be a string that is either C<r> or C<w>, which |
147 | for events. C<poll> must be a string that is either C<r> or C<w>, |
148 | creates a watcher waiting for "r"eadable or "w"ritable events, |
148 | which creates a watcher waiting for "r"eadable or "w"ritable events, |
149 | respectively. C<cb> is the callback to invoke each time the file handle |
149 | respectively. C<cb> is the callback to invoke each time the file handle |
150 | becomes ready. |
150 | becomes ready. |
151 | |
151 | |
152 | As long as the I/O watcher exists it will keep the file descriptor or a |
152 | Although the callback might get passed parameters, their value and |
153 | copy of it alive/open. |
153 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
154 | callbacks cannot use arguments passed to I/O watcher callbacks. |
154 | |
155 | |
|
|
156 | The I/O watcher might use the underlying file descriptor or a copy of it. |
155 | It is not allowed to close a file handle as long as any watcher is active |
157 | You must not close a file handle as long as any watcher is active on the |
156 | on the underlying file descriptor. |
158 | underlying file descriptor. |
157 | |
159 | |
158 | Some event loops issue spurious readyness notifications, so you should |
160 | Some event loops issue spurious readyness notifications, so you should |
159 | always use non-blocking calls when reading/writing from/to your file |
161 | always use non-blocking calls when reading/writing from/to your file |
160 | handles. |
162 | handles. |
161 | |
163 | |
… | |
… | |
172 | |
174 | |
173 | You can create a time watcher by calling the C<< AnyEvent->timer >> |
175 | You can create a time watcher by calling the C<< AnyEvent->timer >> |
174 | method with the following mandatory arguments: |
176 | method with the following mandatory arguments: |
175 | |
177 | |
176 | C<after> specifies after how many seconds (fractional values are |
178 | C<after> specifies after how many seconds (fractional values are |
177 | supported) should the timer activate. C<cb> the callback to invoke in that |
179 | supported) the callback should be invoked. C<cb> is the callback to invoke |
178 | case. |
180 | in that case. |
|
|
181 | |
|
|
182 | Although the callback might get passed parameters, their value and |
|
|
183 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
184 | callbacks cannot use arguments passed to time watcher callbacks. |
179 | |
185 | |
180 | The timer callback will be invoked at most once: if you want a repeating |
186 | The timer callback will be invoked at most once: if you want a repeating |
181 | timer you have to create a new watcher (this is a limitation by both Tk |
187 | timer you have to create a new watcher (this is a limitation by both Tk |
182 | and Glib). |
188 | and Glib). |
183 | |
189 | |
… | |
… | |
228 | |
234 | |
229 | You can watch for signals using a signal watcher, C<signal> is the signal |
235 | You can watch for signals using a signal watcher, C<signal> is the signal |
230 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
236 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
231 | be invoked whenever a signal occurs. |
237 | be invoked whenever a signal occurs. |
232 | |
238 | |
|
|
239 | Although the callback might get passed parameters, their value and |
|
|
240 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
241 | callbacks cannot use arguments passed to signal watcher callbacks. |
|
|
242 | |
233 | Multiple signal occurances can be clumped together into one callback |
243 | Multiple signal occurances can be clumped together into one callback |
234 | invocation, and callback invocation will be synchronous. synchronous means |
244 | invocation, and callback invocation will be synchronous. synchronous means |
235 | that it might take a while until the signal gets handled by the process, |
245 | that it might take a while until the signal gets handled by the process, |
236 | but it is guarenteed not to interrupt any other callbacks. |
246 | but it is guarenteed not to interrupt any other callbacks. |
237 | |
247 | |
… | |
… | |
251 | |
261 | |
252 | The child process is specified by the C<pid> argument (if set to C<0>, it |
262 | The child process is specified by the C<pid> argument (if set to C<0>, it |
253 | watches for any child process exit). The watcher will trigger as often |
263 | watches for any child process exit). The watcher will trigger as often |
254 | as status change for the child are received. This works by installing a |
264 | as status change for the child are received. This works by installing a |
255 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
265 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
256 | and exit status (as returned by waitpid). |
266 | and exit status (as returned by waitpid), so unlike other watcher types, |
|
|
267 | you I<can> rely on child watcher callback arguments. |
257 | |
268 | |
258 | Example: wait for pid 1333 |
269 | There is a slight catch to child watchers, however: you usually start them |
|
|
270 | I<after> the child process was created, and this means the process could |
|
|
271 | have exited already (and no SIGCHLD will be sent anymore). |
|
|
272 | |
|
|
273 | Not all event models handle this correctly (POE doesn't), but even for |
|
|
274 | event models that I<do> handle this correctly, they usually need to be |
|
|
275 | loaded before the process exits (i.e. before you fork in the first place). |
|
|
276 | |
|
|
277 | This means you cannot create a child watcher as the very first thing in an |
|
|
278 | AnyEvent program, you I<have> to create at least one watcher before you |
|
|
279 | C<fork> the child (alternatively, you can call C<AnyEvent::detect>). |
|
|
280 | |
|
|
281 | Example: fork a process and wait for it |
|
|
282 | |
|
|
283 | my $done = AnyEvent->condvar; |
|
|
284 | |
|
|
285 | AnyEvent::detect; # force event module to be initialised |
|
|
286 | |
|
|
287 | my $pid = fork or exit 5; |
259 | |
288 | |
260 | my $w = AnyEvent->child ( |
289 | my $w = AnyEvent->child ( |
261 | pid => 1333, |
290 | pid => $pid, |
262 | cb => sub { |
291 | cb => sub { |
263 | my ($pid, $status) = @_; |
292 | my ($pid, $status) = @_; |
264 | warn "pid $pid exited with status $status"; |
293 | warn "pid $pid exited with status $status"; |
|
|
294 | $done->broadcast; |
265 | }, |
295 | }, |
266 | ); |
296 | ); |
|
|
297 | |
|
|
298 | # do something else, then wait for process exit |
|
|
299 | $done->wait; |
267 | |
300 | |
268 | =head2 CONDITION VARIABLES |
301 | =head2 CONDITION VARIABLES |
269 | |
302 | |
270 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
303 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
271 | method without any arguments. |
304 | method without any arguments. |
… | |
… | |
359 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
392 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
360 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
393 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
361 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
394 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
362 | AnyEvent::Impl::Event based on Event, second best choice. |
395 | AnyEvent::Impl::Event based on Event, second best choice. |
363 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
396 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
|
|
397 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
364 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
398 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
365 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
|
|
366 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
399 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
367 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
400 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
368 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
401 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
369 | |
402 | |
370 | There is no support for WxWidgets, as WxWidgets has no support for |
403 | There is no support for WxWidgets, as WxWidgets has no support for |
… | |
… | |
706 | |
739 | |
707 | =back |
740 | =back |
708 | |
741 | |
709 | =head1 EXAMPLE PROGRAM |
742 | =head1 EXAMPLE PROGRAM |
710 | |
743 | |
711 | The following program uses an IO watcher to read data from STDIN, a timer |
744 | The following program uses an I/O watcher to read data from STDIN, a timer |
712 | to display a message once per second, and a condition variable to quit the |
745 | to display a message once per second, and a condition variable to quit the |
713 | program when the user enters quit: |
746 | program when the user enters quit: |
714 | |
747 | |
715 | use AnyEvent; |
748 | use AnyEvent; |
716 | |
749 | |
… | |
… | |
860 | $quit->broadcast; |
893 | $quit->broadcast; |
861 | }); |
894 | }); |
862 | |
895 | |
863 | $quit->wait; |
896 | $quit->wait; |
864 | |
897 | |
|
|
898 | |
|
|
899 | =head1 BENCHMARK |
|
|
900 | |
|
|
901 | To give you an idea of the performance and overheads that AnyEvent adds |
|
|
902 | over the event loops themselves (and to give you an impression of the |
|
|
903 | speed of various event loops), here is a benchmark of various supported |
|
|
904 | event models natively and with anyevent. The benchmark creates a lot of |
|
|
905 | timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to |
|
|
906 | become writable, which it is), lets them fire exactly once and destroys |
|
|
907 | them again. |
|
|
908 | |
|
|
909 | Rewriting the benchmark to use many different sockets instead of using |
|
|
910 | the same filehandle for all I/O watchers results in a much longer runtime |
|
|
911 | (socket creation is expensive), but qualitatively the same figures, so it |
|
|
912 | was not used. |
|
|
913 | |
|
|
914 | =head2 Explanation of the columns |
|
|
915 | |
|
|
916 | I<watcher> is the number of event watchers created/destroyed. Since |
|
|
917 | different event models feature vastly different performances, each event |
|
|
918 | loop was given a number of watchers so that overall runtime is acceptable |
|
|
919 | and similar between tested event loop (and keep them from crashing): Glib |
|
|
920 | would probably take thousands of years if asked to process the same number |
|
|
921 | of watchers as EV in this benchmark. |
|
|
922 | |
|
|
923 | I<bytes> is the number of bytes (as measured by the resident set size, |
|
|
924 | RSS) consumed by each watcher. This method of measuring captures both C |
|
|
925 | and Perl-based overheads. |
|
|
926 | |
|
|
927 | I<create> is the time, in microseconds (millionths of seconds), that it |
|
|
928 | takes to create a single watcher. The callback is a closure shared between |
|
|
929 | all watchers, to avoid adding memory overhead. That means closure creation |
|
|
930 | and memory usage is not included in the figures. |
|
|
931 | |
|
|
932 | I<invoke> is the time, in microseconds, used to invoke a simple |
|
|
933 | callback. The callback simply counts down a Perl variable and after it was |
|
|
934 | invoked "watcher" times, it would C<< ->broadcast >> a condvar once to |
|
|
935 | signal the end of this phase. |
|
|
936 | |
|
|
937 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
|
|
938 | watcher. |
|
|
939 | |
|
|
940 | =head2 Results |
|
|
941 | |
|
|
942 | name watchers bytes create invoke destroy comment |
|
|
943 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
|
|
944 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
|
|
945 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
|
|
946 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
|
|
947 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
|
|
948 | Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers |
|
|
949 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
|
|
950 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
|
|
951 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
|
|
952 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
|
|
953 | |
|
|
954 | =head2 Discussion |
|
|
955 | |
|
|
956 | The benchmark does I<not> measure scalability of the event loop very |
|
|
957 | well. For example, a select-based event loop (such as the pure perl one) |
|
|
958 | can never compete with an event loop that uses epoll when the number of |
|
|
959 | file descriptors grows high. In this benchmark, all events become ready at |
|
|
960 | the same time, so select/poll-based implementations get an unnatural speed |
|
|
961 | boost. |
|
|
962 | |
|
|
963 | C<EV> is the sole leader regarding speed and memory use, which are both |
|
|
964 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
|
|
965 | far less memory than any other event loop and is still faster than Event |
|
|
966 | natively. |
|
|
967 | |
|
|
968 | The pure perl implementation is hit in a few sweet spots (both the |
|
|
969 | constant timeout and the use of a single fd hit optimisations in the perl |
|
|
970 | interpreter and the backend itself). Nevertheless this shows that it |
|
|
971 | adds very little overhead in itself. Like any select-based backend its |
|
|
972 | performance becomes really bad with lots of file descriptors (and few of |
|
|
973 | them active), of course, but this was not subject of this benchmark. |
|
|
974 | |
|
|
975 | The C<Event> module has a relatively high setup and callback invocation cost, |
|
|
976 | but overall scores on the third place. |
|
|
977 | |
|
|
978 | C<Glib>'s memory usage is quite a bit bit higher, but it features a |
|
|
979 | faster callback invocation and overall ends up in the same class as |
|
|
980 | C<Event>. However, Glib scales extremely badly, doubling the number of |
|
|
981 | watchers increases the processing time by more than a factor of four, |
|
|
982 | making it completely unusable when using larger numbers of watchers |
|
|
983 | (note that only a single file descriptor was used in the benchmark, so |
|
|
984 | inefficiencies of C<poll> do not account for this). |
|
|
985 | |
|
|
986 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
|
|
987 | more than 2000 watchers is a big setback, however, as correctness takes |
|
|
988 | precedence over speed. Nevertheless, its performance is surprising, as the |
|
|
989 | file descriptor is dup()ed for each watcher. This shows that the dup() |
|
|
990 | employed by some adaptors is not a big performance issue (it does incur a |
|
|
991 | hidden memory cost inside the kernel which is not reflected in the figures |
|
|
992 | above). |
|
|
993 | |
|
|
994 | C<POE>, regardless of underlying event loop (whether using its pure |
|
|
995 | perl select-based backend or the Event module, the POE-EV backend |
|
|
996 | couldn't be tested because it wasn't working) shows abysmal performance |
|
|
997 | and memory usage: Watchers use almost 30 times as much memory as |
|
|
998 | EV watchers, and 10 times as much memory as Event (the high memory |
|
|
999 | requirements are caused by requiring a session for each watcher). Watcher |
|
|
1000 | invocation speed is almost 900 times slower than with AnyEvent's pure perl |
|
|
1001 | implementation. The design of the POE adaptor class in AnyEvent can not |
|
|
1002 | really account for this, as session creation overhead is small compared |
|
|
1003 | to execution of the state machine, which is coded pretty optimally within |
|
|
1004 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
|
|
1005 | |
|
|
1006 | =head2 Summary |
|
|
1007 | |
|
|
1008 | =over 4 |
|
|
1009 | |
|
|
1010 | =item * Using EV through AnyEvent is faster than any other event loop, but most |
|
|
1011 | event loops have acceptable performance with or without AnyEvent. |
|
|
1012 | |
|
|
1013 | =item * The overhead AnyEvent adds is usually much smaller than the overhead of |
|
|
1014 | the actual event loop, only with extremely fast event loops such as the EV |
|
|
1015 | adds AnyEvent significant overhead. |
|
|
1016 | |
|
|
1017 | =item * And you should simply avoid POE like the plague if you want performance or |
|
|
1018 | reasonable memory usage. |
|
|
1019 | |
|
|
1020 | =back |
|
|
1021 | |
|
|
1022 | |
865 | =head1 FORK |
1023 | =head1 FORK |
866 | |
1024 | |
867 | Most event libraries are not fork-safe. The ones who are usually are |
1025 | Most event libraries are not fork-safe. The ones who are usually are |
868 | because they are so inefficient. Only L<EV> is fully fork-aware. |
1026 | because they are so inefficient. Only L<EV> is fully fork-aware. |
869 | |
1027 | |
870 | If you have to fork, you must either do so I<before> creating your first |
1028 | If you have to fork, you must either do so I<before> creating your first |
871 | watcher OR you must not use AnyEvent at all in the child. |
1029 | watcher OR you must not use AnyEvent at all in the child. |
|
|
1030 | |
872 | |
1031 | |
873 | =head1 SECURITY CONSIDERATIONS |
1032 | =head1 SECURITY CONSIDERATIONS |
874 | |
1033 | |
875 | AnyEvent can be forced to load any event model via |
1034 | AnyEvent can be forced to load any event model via |
876 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
1035 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
… | |
… | |
884 | |
1043 | |
885 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1044 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
886 | |
1045 | |
887 | use AnyEvent; |
1046 | use AnyEvent; |
888 | |
1047 | |
|
|
1048 | |
889 | =head1 SEE ALSO |
1049 | =head1 SEE ALSO |
890 | |
1050 | |
891 | Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
1051 | Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
892 | L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, |
1052 | L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, |
893 | L<Event::Lib>, L<Qt>, L<POE>. |
1053 | L<Event::Lib>, L<Qt>, L<POE>. |
… | |
… | |
897 | L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, |
1057 | L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, |
898 | L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. |
1058 | L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. |
899 | |
1059 | |
900 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
1060 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
901 | |
1061 | |
|
|
1062 | |
902 | =head1 AUTHOR |
1063 | =head1 AUTHOR |
903 | |
1064 | |
904 | Marc Lehmann <schmorp@schmorp.de> |
1065 | Marc Lehmann <schmorp@schmorp.de> |
905 | http://home.schmorp.de/ |
1066 | http://home.schmorp.de/ |
906 | |
1067 | |