… | |
… | |
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 for |
147 | events. C<poll> must be a string that is either C<r> or C<w>, which |
147 | events. C<poll> must be a string that is either C<r> or C<w>, which |
148 | creates a watcher waiting for "r"eadable or "w"ritable events, |
148 | 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 | The I/O watcher might use the underlying file descriptor or a copy of it. |
153 | copy of it alive/open. |
|
|
154 | |
|
|
155 | It is not allowed to close a file handle as long as any watcher is active |
153 | You must not close a file handle as long as any watcher is active on the |
156 | on the underlying file descriptor. |
154 | underlying file descriptor. |
157 | |
155 | |
158 | Some event loops issue spurious readyness notifications, so you should |
156 | Some event loops issue spurious readyness notifications, so you should |
159 | always use non-blocking calls when reading/writing from/to your file |
157 | always use non-blocking calls when reading/writing from/to your file |
160 | handles. |
158 | handles. |
|
|
159 | |
|
|
160 | Although the callback might get passed parameters, their value and |
|
|
161 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
162 | callbacks cannot use arguments passed to I/O watcher callbacks. |
161 | |
163 | |
162 | Example: |
164 | Example: |
163 | |
165 | |
164 | # wait for readability of STDIN, then read a line and disable the watcher |
166 | # wait for readability of STDIN, then read a line and disable the watcher |
165 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
167 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
… | |
… | |
179 | |
181 | |
180 | The timer callback will be invoked at most once: if you want a repeating |
182 | 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 |
183 | timer you have to create a new watcher (this is a limitation by both Tk |
182 | and Glib). |
184 | and Glib). |
183 | |
185 | |
|
|
186 | Although the callback might get passed parameters, their value and |
|
|
187 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
188 | callbacks cannot use arguments passed to time watcher callbacks. |
|
|
189 | |
184 | Example: |
190 | Example: |
185 | |
191 | |
186 | # fire an event after 7.7 seconds |
192 | # fire an event after 7.7 seconds |
187 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
193 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
188 | warn "timeout\n"; |
194 | warn "timeout\n"; |
… | |
… | |
253 | watches for any child process exit). The watcher will trigger as often |
259 | 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 |
260 | 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 |
261 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
256 | and exit status (as returned by waitpid). |
262 | and exit status (as returned by waitpid). |
257 | |
263 | |
258 | Example: wait for pid 1333 |
264 | There is a slight catch to child watchers, however: you usually start them |
|
|
265 | I<after> the child process was created, and this means the process could |
|
|
266 | have exited already (and no SIGCHLD will be sent anymore). |
|
|
267 | |
|
|
268 | Not all event models handle this correctly (POE doesn't), but even for |
|
|
269 | event models that I<do> handle this correctly, they usually need to be |
|
|
270 | loaded before the process exits (i.e. before you fork in the first place). |
|
|
271 | |
|
|
272 | This means you cannot create a child watcher as the very first thing in an |
|
|
273 | AnyEvent program, you I<have> to create at least one watcher before you |
|
|
274 | C<fork> the child (alternatively, you can call C<AnyEvent::detect>). |
|
|
275 | |
|
|
276 | Example: fork a process and wait for it |
|
|
277 | |
|
|
278 | my $done = AnyEvent->condvar; |
|
|
279 | |
|
|
280 | AnyEvent::detect; # force event module to be initialised |
|
|
281 | |
|
|
282 | my $pid = fork or exit 5; |
259 | |
283 | |
260 | my $w = AnyEvent->child ( |
284 | my $w = AnyEvent->child ( |
261 | pid => 1333, |
285 | pid => $pid, |
262 | cb => sub { |
286 | cb => sub { |
263 | my ($pid, $status) = @_; |
287 | my ($pid, $status) = @_; |
264 | warn "pid $pid exited with status $status"; |
288 | warn "pid $pid exited with status $status"; |
|
|
289 | $done->broadcast; |
265 | }, |
290 | }, |
266 | ); |
291 | ); |
|
|
292 | |
|
|
293 | # do something else, then wait for process exit |
|
|
294 | $done->wait; |
267 | |
295 | |
268 | =head2 CONDITION VARIABLES |
296 | =head2 CONDITION VARIABLES |
269 | |
297 | |
270 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
298 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
271 | method without any arguments. |
299 | method without any arguments. |
… | |
… | |
359 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
387 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
360 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
388 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
361 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
389 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
362 | AnyEvent::Impl::Event based on Event, second best choice. |
390 | AnyEvent::Impl::Event based on Event, second best choice. |
363 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
391 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
|
|
392 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
364 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
393 | 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). |
394 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
367 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
395 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
368 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
396 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
369 | |
397 | |
370 | There is no support for WxWidgets, as WxWidgets has no support for |
398 | There is no support for WxWidgets, as WxWidgets has no support for |
… | |
… | |
706 | |
734 | |
707 | =back |
735 | =back |
708 | |
736 | |
709 | =head1 EXAMPLE PROGRAM |
737 | =head1 EXAMPLE PROGRAM |
710 | |
738 | |
711 | The following program uses an IO watcher to read data from STDIN, a timer |
739 | 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 |
740 | to display a message once per second, and a condition variable to quit the |
713 | program when the user enters quit: |
741 | program when the user enters quit: |
714 | |
742 | |
715 | use AnyEvent; |
743 | use AnyEvent; |
716 | |
744 | |
… | |
… | |
864 | |
892 | |
865 | |
893 | |
866 | =head1 BENCHMARK |
894 | =head1 BENCHMARK |
867 | |
895 | |
868 | To give you an idea of the performance and overheads that AnyEvent adds |
896 | To give you an idea of the performance and overheads that AnyEvent adds |
869 | over the backends directly, here is a benchmark of various supported event |
897 | over the event loops themselves (and to give you an impression of the |
|
|
898 | speed of various event loops), here is a benchmark of various supported |
870 | models natively and with anyevent. The benchmark creates a lot of timers |
899 | event models natively and with anyevent. The benchmark creates a lot of |
871 | (with a zero timeout) and io watchers (watching STDOUT, a pty, to become |
900 | timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to |
872 | writable), lets them fire exactly once and destroys them again. |
901 | become writable, which it is), lets them fire exactly once and destroys |
|
|
902 | them again. |
873 | |
903 | |
874 | Explanation of the fields: |
904 | Rewriting the benchmark to use many different sockets instead of using |
|
|
905 | the same filehandle for all I/O watchers results in a much longer runtime |
|
|
906 | (socket creation is expensive), but qualitatively the same figures, so it |
|
|
907 | was not used. |
875 | |
908 | |
|
|
909 | =head2 Explanation of the columns |
|
|
910 | |
876 | I<watcher> is the number of event watchers created/destroyed. Sicne |
911 | I<watcher> is the number of event watchers created/destroyed. Since |
877 | different event models have vastly different performance each backend was |
912 | different event models feature vastly different performances, each event |
878 | handed a number of watchers so that overall runtime is acceptable and |
913 | loop was given a number of watchers so that overall runtime is acceptable |
879 | similar to all backends (and keep them from crashing). |
914 | and similar between tested event loop (and keep them from crashing): Glib |
|
|
915 | would probably take thousands of years if asked to process the same number |
|
|
916 | of watchers as EV in this benchmark. |
880 | |
917 | |
881 | I<bytes> is the number of bytes (as measured by resident set size) used by |
918 | I<bytes> is the number of bytes (as measured by the resident set size, |
882 | each watcher. |
919 | RSS) consumed by each watcher. This method of measuring captures both C |
|
|
920 | and Perl-based overheads. |
883 | |
921 | |
884 | I<create> is the time, in microseconds, to create a single watcher. |
922 | I<create> is the time, in microseconds (millionths of seconds), that it |
|
|
923 | takes to create a single watcher. The callback is a closure shared between |
|
|
924 | all watchers, to avoid adding memory overhead. That means closure creation |
|
|
925 | and memory usage is not included in the figures. |
885 | |
926 | |
886 | I<invoke> is the time, in microseconds, used to invoke a simple callback |
927 | I<invoke> is the time, in microseconds, used to invoke a simple |
887 | that simply counts down. |
928 | callback. The callback simply counts down a Perl variable and after it was |
|
|
929 | invoked "watcher" times, it would C<< ->broadcast >> a condvar once to |
|
|
930 | signal the end of this phase. |
888 | |
931 | |
889 | I<destroy> is the time, in microseconds, to destroy a single watcher. |
932 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
|
|
933 | watcher. |
890 | |
934 | |
|
|
935 | =head2 Results |
|
|
936 | |
891 | name watcher bytes create invoke destroy comment |
937 | name watchers bytes create invoke destroy comment |
892 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
938 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
893 | EV/Any 100000 610 3.52 0.91 0.75 |
939 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
894 | CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal |
940 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
895 | Perl/Any 10000 654 4.64 1.22 0.77 pure perl implementation |
941 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
896 | Event/Event 10000 523 28.05 21.38 5.22 Event native interface |
942 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
897 | Event/Any 10000 943 34.43 20.48 1.39 |
943 | Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers |
898 | Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour |
944 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
899 | Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers |
945 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
900 | POE/Select 2000 6343 94.69 807.65 562.69 POE::Loop::Select |
|
|
901 | POE/Event 2000 6644 108.15 768.19 14.33 POE::Loop::Event |
946 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
|
|
947 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
902 | |
948 | |
903 | Discussion: The benchmark does I<not> bench scalability of the |
949 | =head2 Discussion |
|
|
950 | |
|
|
951 | The benchmark does I<not> measure scalability of the event loop very |
904 | backend. For example a select-based backend (such as the pureperl one) can |
952 | well. For example, a select-based event loop (such as the pure perl one) |
905 | never compete with a backend using epoll. In this benchmark, only a single |
953 | can never compete with an event loop that uses epoll when the number of |
906 | filehandle is used. |
954 | file descriptors grows high. In this benchmark, all events become ready at |
|
|
955 | the same time, so select/poll-based implementations get an unnatural speed |
|
|
956 | boost. |
907 | |
957 | |
908 | EV is the sole leader regarding speed and memory use, which are both |
958 | C<EV> is the sole leader regarding speed and memory use, which are both |
909 | maximal/minimal. Even when going through AnyEvent, there is only one event |
959 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
910 | loop that uses less memory (the Event module natively), and no faster |
960 | far less memory than any other event loop and is still faster than Event |
911 | event model. |
961 | natively. |
912 | |
962 | |
913 | The pure perl implementation is hit in a few sweet spots (both the |
963 | The pure perl implementation is hit in a few sweet spots (both the |
914 | zero timeout and the use of a single fd hit optimisations in the perl |
964 | zero timeout and the use of a single fd hit optimisations in the perl |
915 | interpreter and the backend itself), but it shows that it adds very little |
965 | interpreter and the backend itself, and all watchers become ready at the |
|
|
966 | same time). Nevertheless this shows that it adds very little overhead in |
916 | overhead in itself. Like any select-based backend it's performance becomes |
967 | itself. Like any select-based backend its performance becomes really bad |
917 | really bad with lots of file descriptors. |
968 | with lots of file descriptors (and few of them active), of course, but |
|
|
969 | this was not subject of this benchmark. |
918 | |
970 | |
919 | The Event module has a relatively high setup and callback invocation cost, |
971 | The C<Event> module has a relatively high setup and callback invocation cost, |
920 | but overall scores on the third place. |
972 | but overall scores on the third place. |
921 | |
973 | |
922 | Glib has a little higher memory cost, a bit fster callback invocation and |
974 | C<Glib>'s memory usage is quite a bit bit higher, but it features a |
923 | has a similar speed as Event. |
975 | faster callback invocation and overall ends up in the same class as |
|
|
976 | C<Event>. However, Glib scales extremely badly, doubling the number of |
|
|
977 | watchers increases the processing time by more than a factor of four, |
|
|
978 | making it completely unusable when using larger numbers of watchers |
|
|
979 | (note that only a single file descriptor was used in the benchmark, so |
|
|
980 | inefficiencies of C<poll> do not account for this). |
924 | |
981 | |
925 | The Tk backend works relatively well, the fact that it crashes with |
982 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
926 | more than 2000 watchers is a big setback, however, as correctness takes |
983 | more than 2000 watchers is a big setback, however, as correctness takes |
927 | precedence over speed. |
984 | precedence over speed. Nevertheless, its performance is surprising, as the |
|
|
985 | file descriptor is dup()ed for each watcher. This shows that the dup() |
|
|
986 | employed by some adaptors is not a big performance issue (it does incur a |
|
|
987 | hidden memory cost inside the kernel, though, that is not reflected in the |
|
|
988 | figures above). |
928 | |
989 | |
929 | POE, regardless of backend (wether it's pure perl select backend or the |
990 | C<POE>, regardless of underlying event loop (wether using its pure perl |
930 | Event backend) shows abysmal performance and memory usage: Watchers use |
991 | select-based backend or the Event module) shows abysmal performance and |
931 | almost 30 times as much memory as EV watchers, and 10 times as much memory |
992 | memory usage: Watchers use almost 30 times as much memory as EV watchers, |
932 | as both Event or EV via AnyEvent. |
993 | and 10 times as much memory as both Event or EV via AnyEvent. Watcher |
|
|
994 | invocation is almost 900 times slower than with AnyEvent's pure perl |
|
|
995 | implementation. The design of the POE adaptor class in AnyEvent can not |
|
|
996 | really account for this, as session creation overhead is small compared |
|
|
997 | to execution of the state machine, which is coded pretty optimally within |
|
|
998 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
933 | |
999 | |
|
|
1000 | =head2 Summary |
|
|
1001 | |
934 | Summary: using EV through AnyEvent is faster than any other event |
1002 | Using EV through AnyEvent is faster than any other event loop, but most |
935 | loop. The overhead AnyEvent adds can be very small, and you should avoid |
1003 | event loops have acceptable performance with or without AnyEvent. |
936 | POE like the plague if you want performance or reasonable memory usage. |
1004 | |
|
|
1005 | The overhead AnyEvent adds is usually much smaller than the overhead of |
|
|
1006 | the actual event loop, only with extremely fast event loops such as the EV |
|
|
1007 | adds AnyEvent significant overhead. |
|
|
1008 | |
|
|
1009 | And you should simply avoid POE like the plague if you want performance or |
|
|
1010 | reasonable memory usage. |
937 | |
1011 | |
938 | |
1012 | |
939 | =head1 FORK |
1013 | =head1 FORK |
940 | |
1014 | |
941 | Most event libraries are not fork-safe. The ones who are usually are |
1015 | Most event libraries are not fork-safe. The ones who are usually are |