[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.81 by root, Fri Apr 25 13:05:17 2008 UTC vs.
Revision 1.85 by root, Fri Apr 25 13:51:32 2008 UTC

 =head2 I/O WATCHERS
 You can create an I/O watcher by calling the C<< AnyEvent->io >> method
 with the following mandatory key-value pairs as arguments:
-C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for
+C<fh> the Perl I<file handle> (I<not> file descriptor) to watch
-events. C<poll> must be a string that is either C<r> or C<w>, which
+for events. C<poll> must be a string that is either C<r> or C<w>,
-creates a watcher waiting for "r"eadable or "w"ritable events,
+which creates a watcher waiting for "r"eadable or "w"ritable events,
 respectively. C<cb> is the callback to invoke each time the file handle
 becomes ready.
-As long as the I/O watcher exists it will keep the file descriptor or a
+Although the callback might get passed parameters, their value and
-copy of it alive/open.
+presence is undefined and you cannot rely on them. Portable AnyEvent
+callbacks cannot use arguments passed to I/O watcher callbacks.
+The I/O watcher might use the underlying file descriptor or a copy of it.
-It is not allowed to close a file handle as long as any watcher is active
+You must not close a file handle as long as any watcher is active on the
-on the underlying file descriptor.
+underlying file descriptor.
 Some event loops issue spurious readyness notifications, so you should
 always use non-blocking calls when reading/writing from/to your file
 handles.
 You can create a time watcher by calling the C<< AnyEvent->timer >>
 method with the following mandatory arguments:
 C<after> specifies after how many seconds (fractional values are
-supported) should the timer activate. C<cb> the callback to invoke in that
+supported) the callback should be invoked. C<cb> is the callback to invoke
-case.
+in that case.
+Although the callback might get passed parameters, their value and
+presence is undefined and you cannot rely on them. Portable AnyEvent
+callbacks cannot use arguments passed to time watcher callbacks.
 The timer callback will be invoked at most once: if you want a repeating
 timer you have to create a new watcher (this is a limitation by both Tk
 and Glib).
 You can watch for signals using a signal watcher, C<signal> is the signal
 I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
 be invoked whenever a signal occurs.
+Although the callback might get passed parameters, their value and
+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
 that it might take a while until the signal gets handled by the process,
 but it is guarenteed not to interrupt any other callbacks.
 The child process is specified by the C<pid> argument (if set to C<0>, it
 watches for any child process exit). The watcher will trigger as often
 as status change for the child are received. This works by installing a
 signal handler for C<SIGCHLD>. The callback will be called with the pid
-and exit status (as returned by waitpid).
+and exit status (as returned by waitpid), so unlike other watcher types,
+you I<can> rely on child watcher callback arguments.
-Example: wait for pid 1333
+There is a slight catch to child watchers, however: you usually start them
+I<after> the child process was created, and this means the process could
+have exited already (and no SIGCHLD will be sent anymore).
+Not all event models handle this correctly (POE doesn't), but even for
+event models that I<do> handle this correctly, they usually need to be
+loaded before the process exits (i.e. before you fork in the first place).
+This means you cannot create a child watcher as the very first thing in an
+AnyEvent program, you I<have> to create at least one watcher before you
+C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
+Example: fork a process and wait for it
+  my $done = AnyEvent->condvar;
+  AnyEvent::detect; # force event module to be initialised
+  my $pid = fork or exit 5;
   my $w = AnyEvent->child (
-     pid => 1333,
+     pid => $pid,
      cb  => sub {
         my ($pid, $status) = @_;
         warn "pid $pid exited with status $status";
+        $done->broadcast;
      },
   );
+  # do something else, then wait for process exit
+  $done->wait;
 =head2 CONDITION VARIABLES
 Condition variables can be created by calling the C<< AnyEvent->condvar >>
 method without any arguments.
 =head2 Results
           name watchers bytes create invoke destroy comment
          EV/EV   400000   244   0.56   0.46    0.31 EV native interface
-        EV/Any   100000   610   3.52   0.91    0.75 EV + AnyEvent watchers
+        EV/Any   100000   244   2.50   0.46    0.29 EV + AnyEvent watchers
-    CoroEV/Any   100000   610   3.49   0.92    0.75 coroutines + Coro::Signal
+    CoroEV/Any   100000   244   2.49   0.44    0.29 coroutines + Coro::Signal
-      Perl/Any   100000   513   4.91   0.92    1.15 pure perl implementation
+      Perl/Any   100000   513   4.92   0.87    1.12 pure perl implementation
-   Event/Event    16000   523  28.05  21.38    0.86 Event native interface
+   Event/Event    16000   516  31.88  31.30    0.85 Event native interface
-     Event/Any    16000   943  34.43  20.48    1.39 Event + AnyEvent watchers
+     Event/Any    16000   936  39.17  33.63    1.43 Event + AnyEvent watchers
-      Glib/Any    16000  1357  96.99  12.55   55.51 quadratic behaviour
+      Glib/Any    16000  1357  98.22  12.41   54.00 quadratic behaviour
-        Tk/Any     2000  1855  27.01  66.61   14.03 SEGV with >> 2000 watchers
+        Tk/Any     2000  1860  26.97  67.98   14.00 SEGV with >> 2000 watchers
-     POE/Event     2000  6644 108.15 768.19   14.33 via POE::Loop::Event
+     POE/Event     2000  6644 108.64 736.02   14.73 via POE::Loop::Event
-    POE/Select     2000  6343  94.69 807.65  562.69 via POE::Loop::Select
+    POE/Select     2000  6343  94.13 809.12  565.96 via POE::Loop::Select
 =head2 Discussion
 The benchmark does I<not> measure scalability of the event loop very
 well. For example, a select-based event loop (such as the pure perl one)
 file descriptors grows high. In this benchmark, all events become ready at
 the same time, so select/poll-based implementations get an unnatural speed
 boost.
 C<EV> is the sole leader regarding speed and memory use, which are both
-maximal/minimal, respectively. Even when going through AnyEvent, there are
+maximal/minimal, respectively. Even when going through AnyEvent, it uses
-only two event loops that use slightly less memory (the C<Event> module
+far less memory than any other event loop and is still faster than Event
-natively and the pure perl backend), and no faster event models, not even
+natively.
-C<Event> natively.
 The pure perl implementation is hit in a few sweet spots (both the
 zero timeout and the use of a single fd hit optimisations in the perl
 interpreter and the backend itself, and all watchers become ready at the
 same time). Nevertheless this shows that it adds very little overhead in

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.81 by root, Fri Apr 25 13:05:17 2008 UTC vs. Revision 1.85 by root, Fri Apr 25 13:51:32 2008 UTC

Diff Legend

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.81 by root, Fri Apr 25 13:05:17 2008 UTC vs.
Revision 1.85 by root, Fri Apr 25 13:51:32 2008 UTC