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141 | =head2 I/O 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 |
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|
154 | callbacks cannot use arguments passed to I/O watcher callbacks. |
154 | |
155 | |
|
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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 | |
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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. |
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181 | |
|
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182 | Although the callback might get passed parameters, their value and |
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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 | |
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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. |
|
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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 |
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|
270 | I<after> the child process was created, and this means the process could |
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|
271 | have exited already (and no SIGCHLD will be sent anymore). |
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272 | |
|
|
273 | Not all event models handle this correctly (POE doesn't), but even for |
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|
274 | event models that I<do> handle this correctly, they usually need to be |
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|
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 |
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|
279 | C<fork> the child (alternatively, you can call C<AnyEvent::detect>). |
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|
280 | |
|
|
281 | Example: fork a process and wait for it |
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|
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 |
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|
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. |
… | |
… | |
906 | |
939 | |
907 | =head2 Results |
940 | =head2 Results |
908 | |
941 | |
909 | name watchers bytes create invoke destroy comment |
942 | name watchers bytes create invoke destroy comment |
910 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
943 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
911 | EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers |
944 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
912 | CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal |
945 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
913 | Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation |
946 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
914 | Event/Event 16000 523 28.05 21.38 0.86 Event native interface |
947 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
915 | Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers |
948 | Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers |
916 | Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour |
949 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
917 | Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers |
950 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
918 | POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event |
951 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
919 | POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select |
952 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
920 | |
953 | |
921 | =head2 Discussion |
954 | =head2 Discussion |
922 | |
955 | |
923 | The benchmark does I<not> measure scalability of the event loop very |
956 | The benchmark does I<not> measure scalability of the event loop very |
924 | well. For example, a select-based event loop (such as the pure perl one) |
957 | well. For example, a select-based event loop (such as the pure perl one) |
… | |
… | |
926 | file descriptors grows high. In this benchmark, all events become ready at |
959 | file descriptors grows high. In this benchmark, all events become ready at |
927 | the same time, so select/poll-based implementations get an unnatural speed |
960 | the same time, so select/poll-based implementations get an unnatural speed |
928 | boost. |
961 | boost. |
929 | |
962 | |
930 | C<EV> is the sole leader regarding speed and memory use, which are both |
963 | C<EV> is the sole leader regarding speed and memory use, which are both |
931 | maximal/minimal, respectively. Even when going through AnyEvent, there are |
964 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
932 | only two event loops that use slightly less memory (the C<Event> module |
965 | far less memory than any other event loop and is still faster than Event |
933 | natively and the pure perl backend), and no faster event models, not even |
966 | natively. |
934 | C<Event> natively. |
|
|
935 | |
967 | |
936 | The pure perl implementation is hit in a few sweet spots (both the |
968 | The pure perl implementation is hit in a few sweet spots (both the |
937 | zero timeout and the use of a single fd hit optimisations in the perl |
969 | zero timeout and the use of a single fd hit optimisations in the perl |
938 | interpreter and the backend itself, and all watchers become ready at the |
970 | interpreter and the backend itself, and all watchers become ready at the |
939 | same time). Nevertheless this shows that it adds very little overhead in |
971 | same time). Nevertheless this shows that it adds very little overhead in |