… | |
… | |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // unloop was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
68 | |
70 | |
69 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
70 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
71 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
72 | |
84 | |
73 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
74 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
75 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
76 | |
88 | |
… | |
… | |
86 | =head2 FEATURES |
98 | =head2 FEATURES |
87 | |
99 | |
88 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
89 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
90 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
91 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
92 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
93 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
94 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
95 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
107 | change events (C<ev_child>), and event watchers dealing with the event |
96 | file watchers (C<ev_stat>) and even limited support for fork events |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
97 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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110 | limited support for fork events (C<ev_fork>). |
98 | |
111 | |
99 | It also is quite fast (see this |
112 | It also is quite fast (see this |
100 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
101 | for example). |
114 | for example). |
102 | |
115 | |
… | |
… | |
110 | name C<loop> (which is always of type C<ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<ev_loop *>) will not have |
111 | this argument. |
124 | this argument. |
112 | |
125 | |
113 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
114 | |
127 | |
115 | Libev represents time as a single floating point number, representing the |
128 | Libev represents time as a single floating point number, representing |
116 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
117 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | near the beginning of 1970, details are complicated, don't ask). This |
118 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
131 | type is called C<ev_tstamp>, which is what you should use too. It usually |
119 | to the C<double> type in C, and when you need to do any calculations on |
132 | aliases to the C<double> type in C. When you need to do any calculations |
120 | it, you should treat it as some floating point value. Unlike the name |
133 | on it, you should treat it as some floating point value. Unlike the name |
121 | component C<stamp> might indicate, it is also used for time differences |
134 | component C<stamp> might indicate, it is also used for time differences |
122 | throughout libev. |
135 | throughout libev. |
123 | |
136 | |
124 | =head1 ERROR HANDLING |
137 | =head1 ERROR HANDLING |
125 | |
138 | |
… | |
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349 | forget about forgetting to tell libev about forking) when you use this |
362 | forget about forgetting to tell libev about forking) when you use this |
350 | flag. |
363 | flag. |
351 | |
364 | |
352 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
365 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
353 | environment variable. |
366 | environment variable. |
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367 | |
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368 | =item C<EVFLAG_NOINOTIFY> |
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369 | |
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370 | When this flag is specified, then libev will not attempt to use the |
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371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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372 | testing, this flag can be useful to conserve inotify file descriptors, as |
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373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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374 | |
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375 | =item C<EVFLAG_NOSIGNALFD> |
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376 | |
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377 | When this flag is specified, then libev will not attempt to use the |
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378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is |
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379 | probably only useful to work around any bugs in libev. Consequently, this |
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380 | flag might go away once the signalfd functionality is considered stable, |
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381 | so it's useful mostly in environment variables and not in program code. |
354 | |
382 | |
355 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
383 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
356 | |
384 | |
357 | This is your standard select(2) backend. Not I<completely> standard, as |
385 | This is your standard select(2) backend. Not I<completely> standard, as |
358 | libev tries to roll its own fd_set with no limits on the number of fds, |
386 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
506 | |
534 | |
507 | It is definitely not recommended to use this flag. |
535 | It is definitely not recommended to use this flag. |
508 | |
536 | |
509 | =back |
537 | =back |
510 | |
538 | |
511 | If one or more of these are or'ed into the flags value, then only these |
539 | If one or more of the backend flags are or'ed into the flags value, |
512 | backends will be tried (in the reverse order as listed here). If none are |
540 | then only these backends will be tried (in the reverse order as listed |
513 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
541 | here). If none are specified, all backends in C<ev_recommended_backends |
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542 | ()> will be tried. |
514 | |
543 | |
515 | Example: This is the most typical usage. |
544 | Example: This is the most typical usage. |
516 | |
545 | |
517 | if (!ev_default_loop (0)) |
546 | if (!ev_default_loop (0)) |
518 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
547 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
… | |
… | |
609 | |
638 | |
610 | This value can sometimes be useful as a generation counter of sorts (it |
639 | This value can sometimes be useful as a generation counter of sorts (it |
611 | "ticks" the number of loop iterations), as it roughly corresponds with |
640 | "ticks" the number of loop iterations), as it roughly corresponds with |
612 | C<ev_prepare> and C<ev_check> calls. |
641 | C<ev_prepare> and C<ev_check> calls. |
613 | |
642 | |
|
|
643 | =item unsigned int ev_loop_depth (loop) |
|
|
644 | |
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645 | Returns the number of times C<ev_loop> was entered minus the number of |
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|
646 | times C<ev_loop> was exited, in other words, the recursion depth. |
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647 | |
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648 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
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649 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
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650 | in which case it is higher. |
|
|
651 | |
|
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652 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
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653 | etc.), doesn't count as exit. |
|
|
654 | |
614 | =item unsigned int ev_backend (loop) |
655 | =item unsigned int ev_backend (loop) |
615 | |
656 | |
616 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
657 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
617 | use. |
658 | use. |
618 | |
659 | |
… | |
… | |
632 | |
673 | |
633 | This function is rarely useful, but when some event callback runs for a |
674 | This function is rarely useful, but when some event callback runs for a |
634 | very long time without entering the event loop, updating libev's idea of |
675 | very long time without entering the event loop, updating libev's idea of |
635 | the current time is a good idea. |
676 | the current time is a good idea. |
636 | |
677 | |
637 | See also "The special problem of time updates" in the C<ev_timer> section. |
678 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
679 | |
|
|
680 | =item ev_suspend (loop) |
|
|
681 | |
|
|
682 | =item ev_resume (loop) |
|
|
683 | |
|
|
684 | These two functions suspend and resume a loop, for use when the loop is |
|
|
685 | not used for a while and timeouts should not be processed. |
|
|
686 | |
|
|
687 | A typical use case would be an interactive program such as a game: When |
|
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688 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
689 | would be best to handle timeouts as if no time had actually passed while |
|
|
690 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
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691 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
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692 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
693 | |
|
|
694 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
695 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
696 | will be rescheduled (that is, they will lose any events that would have |
|
|
697 | occured while suspended). |
|
|
698 | |
|
|
699 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
700 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
701 | without a previous call to C<ev_suspend>. |
|
|
702 | |
|
|
703 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
704 | event loop time (see C<ev_now_update>). |
638 | |
705 | |
639 | =item ev_loop (loop, int flags) |
706 | =item ev_loop (loop, int flags) |
640 | |
707 | |
641 | Finally, this is it, the event handler. This function usually is called |
708 | Finally, this is it, the event handler. This function usually is called |
642 | after you initialised all your watchers and you want to start handling |
709 | after you initialised all your watchers and you want to start handling |
… | |
… | |
773 | |
840 | |
774 | By setting a higher I<io collect interval> you allow libev to spend more |
841 | By setting a higher I<io collect interval> you allow libev to spend more |
775 | time collecting I/O events, so you can handle more events per iteration, |
842 | time collecting I/O events, so you can handle more events per iteration, |
776 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
843 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
777 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
844 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
778 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
845 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
846 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
847 | once per this interval, on average. |
779 | |
848 | |
780 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
849 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
781 | to spend more time collecting timeouts, at the expense of increased |
850 | to spend more time collecting timeouts, at the expense of increased |
782 | latency/jitter/inexactness (the watcher callback will be called |
851 | latency/jitter/inexactness (the watcher callback will be called |
783 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
852 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
785 | |
854 | |
786 | Many (busy) programs can usually benefit by setting the I/O collect |
855 | Many (busy) programs can usually benefit by setting the I/O collect |
787 | interval to a value near C<0.1> or so, which is often enough for |
856 | interval to a value near C<0.1> or so, which is often enough for |
788 | interactive servers (of course not for games), likewise for timeouts. It |
857 | interactive servers (of course not for games), likewise for timeouts. It |
789 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
858 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
790 | as this approaches the timing granularity of most systems. |
859 | as this approaches the timing granularity of most systems. Note that if |
|
|
860 | you do transactions with the outside world and you can't increase the |
|
|
861 | parallelity, then this setting will limit your transaction rate (if you |
|
|
862 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
863 | then you can't do more than 100 transations per second). |
791 | |
864 | |
792 | Setting the I<timeout collect interval> can improve the opportunity for |
865 | Setting the I<timeout collect interval> can improve the opportunity for |
793 | saving power, as the program will "bundle" timer callback invocations that |
866 | saving power, as the program will "bundle" timer callback invocations that |
794 | are "near" in time together, by delaying some, thus reducing the number of |
867 | are "near" in time together, by delaying some, thus reducing the number of |
795 | times the process sleeps and wakes up again. Another useful technique to |
868 | times the process sleeps and wakes up again. Another useful technique to |
796 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
869 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
797 | they fire on, say, one-second boundaries only. |
870 | they fire on, say, one-second boundaries only. |
|
|
871 | |
|
|
872 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
873 | more often than 100 times per second: |
|
|
874 | |
|
|
875 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
876 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
877 | |
|
|
878 | =item ev_invoke_pending (loop) |
|
|
879 | |
|
|
880 | This call will simply invoke all pending watchers while resetting their |
|
|
881 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
882 | but when overriding the invoke callback this call comes handy. |
|
|
883 | |
|
|
884 | =item int ev_pending_count (loop) |
|
|
885 | |
|
|
886 | Returns the number of pending watchers - zero indicates that no watchers |
|
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887 | are pending. |
|
|
888 | |
|
|
889 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
890 | |
|
|
891 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
892 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
893 | this callback instead. This is useful, for example, when you want to |
|
|
894 | invoke the actual watchers inside another context (another thread etc.). |
|
|
895 | |
|
|
896 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
897 | callback. |
|
|
898 | |
|
|
899 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
900 | |
|
|
901 | Sometimes you want to share the same loop between multiple threads. This |
|
|
902 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
903 | each call to a libev function. |
|
|
904 | |
|
|
905 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
906 | wait for it to return. One way around this is to wake up the loop via |
|
|
907 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
908 | and I<acquire> callbacks on the loop. |
|
|
909 | |
|
|
910 | When set, then C<release> will be called just before the thread is |
|
|
911 | suspended waiting for new events, and C<acquire> is called just |
|
|
912 | afterwards. |
|
|
913 | |
|
|
914 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
915 | C<acquire> will just call the mutex_lock function again. |
|
|
916 | |
|
|
917 | While event loop modifications are allowed between invocations of |
|
|
918 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
919 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
920 | have no effect on the set of file descriptors being watched, or the time |
|
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921 | waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
922 | to take note of any changes you made. |
|
|
923 | |
|
|
924 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
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925 | invocations of C<release> and C<acquire>. |
|
|
926 | |
|
|
927 | See also the locking example in the C<THREADS> section later in this |
|
|
928 | document. |
|
|
929 | |
|
|
930 | =item ev_set_userdata (loop, void *data) |
|
|
931 | |
|
|
932 | =item ev_userdata (loop) |
|
|
933 | |
|
|
934 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
935 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
936 | C<0.> |
|
|
937 | |
|
|
938 | These two functions can be used to associate arbitrary data with a loop, |
|
|
939 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
940 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
941 | any other purpose as well. |
798 | |
942 | |
799 | =item ev_loop_verify (loop) |
943 | =item ev_loop_verify (loop) |
800 | |
944 | |
801 | This function only does something when C<EV_VERIFY> support has been |
945 | This function only does something when C<EV_VERIFY> support has been |
802 | compiled in, which is the default for non-minimal builds. It tries to go |
946 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
1057 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1201 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1058 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1202 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1059 | before watchers with lower priority, but priority will not keep watchers |
1203 | before watchers with lower priority, but priority will not keep watchers |
1060 | from being executed (except for C<ev_idle> watchers). |
1204 | from being executed (except for C<ev_idle> watchers). |
1061 | |
1205 | |
1062 | This means that priorities are I<only> used for ordering callback |
|
|
1063 | invocation after new events have been received. This is useful, for |
|
|
1064 | example, to reduce latency after idling, or more often, to bind two |
|
|
1065 | watchers on the same event and make sure one is called first. |
|
|
1066 | |
|
|
1067 | If you need to suppress invocation when higher priority events are pending |
1206 | If you need to suppress invocation when higher priority events are pending |
1068 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1207 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1069 | |
1208 | |
1070 | You I<must not> change the priority of a watcher as long as it is active or |
1209 | You I<must not> change the priority of a watcher as long as it is active or |
1071 | pending. |
1210 | pending. |
1072 | |
|
|
1073 | The default priority used by watchers when no priority has been set is |
|
|
1074 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1075 | |
1211 | |
1076 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1212 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1077 | fine, as long as you do not mind that the priority value you query might |
1213 | fine, as long as you do not mind that the priority value you query might |
1078 | or might not have been clamped to the valid range. |
1214 | or might not have been clamped to the valid range. |
|
|
1215 | |
|
|
1216 | The default priority used by watchers when no priority has been set is |
|
|
1217 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1218 | |
|
|
1219 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1220 | priorities. |
1079 | |
1221 | |
1080 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1222 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1081 | |
1223 | |
1082 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1224 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1083 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1225 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1148 | #include <stddef.h> |
1290 | #include <stddef.h> |
1149 | |
1291 | |
1150 | static void |
1292 | static void |
1151 | t1_cb (EV_P_ ev_timer *w, int revents) |
1293 | t1_cb (EV_P_ ev_timer *w, int revents) |
1152 | { |
1294 | { |
1153 | struct my_biggy big = (struct my_biggy * |
1295 | struct my_biggy big = (struct my_biggy *) |
1154 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1296 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1155 | } |
1297 | } |
1156 | |
1298 | |
1157 | static void |
1299 | static void |
1158 | t2_cb (EV_P_ ev_timer *w, int revents) |
1300 | t2_cb (EV_P_ ev_timer *w, int revents) |
1159 | { |
1301 | { |
1160 | struct my_biggy big = (struct my_biggy * |
1302 | struct my_biggy big = (struct my_biggy *) |
1161 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1303 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1162 | } |
1304 | } |
|
|
1305 | |
|
|
1306 | =head2 WATCHER PRIORITY MODELS |
|
|
1307 | |
|
|
1308 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1309 | integers that influence the ordering of event callback invocation |
|
|
1310 | between watchers in some way, all else being equal. |
|
|
1311 | |
|
|
1312 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1313 | description for the more technical details such as the actual priority |
|
|
1314 | range. |
|
|
1315 | |
|
|
1316 | There are two common ways how these these priorities are being interpreted |
|
|
1317 | by event loops: |
|
|
1318 | |
|
|
1319 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1320 | of lower priority watchers, which means as long as higher priority |
|
|
1321 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1322 | |
|
|
1323 | The less common only-for-ordering model uses priorities solely to order |
|
|
1324 | callback invocation within a single event loop iteration: Higher priority |
|
|
1325 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1326 | before polling for new events. |
|
|
1327 | |
|
|
1328 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1329 | except for idle watchers (which use the lock-out model). |
|
|
1330 | |
|
|
1331 | The rationale behind this is that implementing the lock-out model for |
|
|
1332 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1333 | libraries will just poll for the same events again and again as long as |
|
|
1334 | their callbacks have not been executed, which is very inefficient in the |
|
|
1335 | common case of one high-priority watcher locking out a mass of lower |
|
|
1336 | priority ones. |
|
|
1337 | |
|
|
1338 | Static (ordering) priorities are most useful when you have two or more |
|
|
1339 | watchers handling the same resource: a typical usage example is having an |
|
|
1340 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1341 | timeouts. Under load, data might be received while the program handles |
|
|
1342 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1343 | handler will be executed before checking for data. In that case, giving |
|
|
1344 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1345 | handled first even under adverse conditions (which is usually, but not |
|
|
1346 | always, what you want). |
|
|
1347 | |
|
|
1348 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1349 | will only be executed when no same or higher priority watchers have |
|
|
1350 | received events, they can be used to implement the "lock-out" model when |
|
|
1351 | required. |
|
|
1352 | |
|
|
1353 | For example, to emulate how many other event libraries handle priorities, |
|
|
1354 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1355 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1356 | processing is done in the idle watcher callback. This causes libev to |
|
|
1357 | continously poll and process kernel event data for the watcher, but when |
|
|
1358 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1359 | workable. |
|
|
1360 | |
|
|
1361 | Usually, however, the lock-out model implemented that way will perform |
|
|
1362 | miserably under the type of load it was designed to handle. In that case, |
|
|
1363 | it might be preferable to stop the real watcher before starting the |
|
|
1364 | idle watcher, so the kernel will not have to process the event in case |
|
|
1365 | the actual processing will be delayed for considerable time. |
|
|
1366 | |
|
|
1367 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1368 | priority than the default, and which should only process data when no |
|
|
1369 | other events are pending: |
|
|
1370 | |
|
|
1371 | ev_idle idle; // actual processing watcher |
|
|
1372 | ev_io io; // actual event watcher |
|
|
1373 | |
|
|
1374 | static void |
|
|
1375 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1376 | { |
|
|
1377 | // stop the I/O watcher, we received the event, but |
|
|
1378 | // are not yet ready to handle it. |
|
|
1379 | ev_io_stop (EV_A_ w); |
|
|
1380 | |
|
|
1381 | // start the idle watcher to ahndle the actual event. |
|
|
1382 | // it will not be executed as long as other watchers |
|
|
1383 | // with the default priority are receiving events. |
|
|
1384 | ev_idle_start (EV_A_ &idle); |
|
|
1385 | } |
|
|
1386 | |
|
|
1387 | static void |
|
|
1388 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1389 | { |
|
|
1390 | // actual processing |
|
|
1391 | read (STDIN_FILENO, ...); |
|
|
1392 | |
|
|
1393 | // have to start the I/O watcher again, as |
|
|
1394 | // we have handled the event |
|
|
1395 | ev_io_start (EV_P_ &io); |
|
|
1396 | } |
|
|
1397 | |
|
|
1398 | // initialisation |
|
|
1399 | ev_idle_init (&idle, idle_cb); |
|
|
1400 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1401 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1402 | |
|
|
1403 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1404 | low-priority connections can not be locked out forever under load. This |
|
|
1405 | enables your program to keep a lower latency for important connections |
|
|
1406 | during short periods of high load, while not completely locking out less |
|
|
1407 | important ones. |
1163 | |
1408 | |
1164 | |
1409 | |
1165 | =head1 WATCHER TYPES |
1410 | =head1 WATCHER TYPES |
1166 | |
1411 | |
1167 | This section describes each watcher in detail, but will not repeat |
1412 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1193 | descriptors to non-blocking mode is also usually a good idea (but not |
1438 | descriptors to non-blocking mode is also usually a good idea (but not |
1194 | required if you know what you are doing). |
1439 | required if you know what you are doing). |
1195 | |
1440 | |
1196 | If you cannot use non-blocking mode, then force the use of a |
1441 | If you cannot use non-blocking mode, then force the use of a |
1197 | known-to-be-good backend (at the time of this writing, this includes only |
1442 | known-to-be-good backend (at the time of this writing, this includes only |
1198 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1443 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1444 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1445 | files) - libev doesn't guarentee any specific behaviour in that case. |
1199 | |
1446 | |
1200 | Another thing you have to watch out for is that it is quite easy to |
1447 | Another thing you have to watch out for is that it is quite easy to |
1201 | receive "spurious" readiness notifications, that is your callback might |
1448 | receive "spurious" readiness notifications, that is your callback might |
1202 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1449 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1203 | because there is no data. Not only are some backends known to create a |
1450 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1324 | year, it will still time out after (roughly) one hour. "Roughly" because |
1571 | year, it will still time out after (roughly) one hour. "Roughly" because |
1325 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1572 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1326 | monotonic clock option helps a lot here). |
1573 | monotonic clock option helps a lot here). |
1327 | |
1574 | |
1328 | The callback is guaranteed to be invoked only I<after> its timeout has |
1575 | The callback is guaranteed to be invoked only I<after> its timeout has |
1329 | passed, but if multiple timers become ready during the same loop iteration |
1576 | passed (not I<at>, so on systems with very low-resolution clocks this |
1330 | then order of execution is undefined. |
1577 | might introduce a small delay). If multiple timers become ready during the |
|
|
1578 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1579 | before ones of the same priority with later time-out values (but this is |
|
|
1580 | no longer true when a callback calls C<ev_loop> recursively). |
1331 | |
1581 | |
1332 | =head3 Be smart about timeouts |
1582 | =head3 Be smart about timeouts |
1333 | |
1583 | |
1334 | Many real-world problems involve some kind of timeout, usually for error |
1584 | Many real-world problems involve some kind of timeout, usually for error |
1335 | recovery. A typical example is an HTTP request - if the other side hangs, |
1585 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1379 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1629 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1380 | member and C<ev_timer_again>. |
1630 | member and C<ev_timer_again>. |
1381 | |
1631 | |
1382 | At start: |
1632 | At start: |
1383 | |
1633 | |
1384 | ev_timer_init (timer, callback); |
1634 | ev_init (timer, callback); |
1385 | timer->repeat = 60.; |
1635 | timer->repeat = 60.; |
1386 | ev_timer_again (loop, timer); |
1636 | ev_timer_again (loop, timer); |
1387 | |
1637 | |
1388 | Each time there is some activity: |
1638 | Each time there is some activity: |
1389 | |
1639 | |
… | |
… | |
1451 | |
1701 | |
1452 | To start the timer, simply initialise the watcher and set C<last_activity> |
1702 | To start the timer, simply initialise the watcher and set C<last_activity> |
1453 | to the current time (meaning we just have some activity :), then call the |
1703 | to the current time (meaning we just have some activity :), then call the |
1454 | callback, which will "do the right thing" and start the timer: |
1704 | callback, which will "do the right thing" and start the timer: |
1455 | |
1705 | |
1456 | ev_timer_init (timer, callback); |
1706 | ev_init (timer, callback); |
1457 | last_activity = ev_now (loop); |
1707 | last_activity = ev_now (loop); |
1458 | callback (loop, timer, EV_TIMEOUT); |
1708 | callback (loop, timer, EV_TIMEOUT); |
1459 | |
1709 | |
1460 | And when there is some activity, simply store the current time in |
1710 | And when there is some activity, simply store the current time in |
1461 | C<last_activity>, no libev calls at all: |
1711 | C<last_activity>, no libev calls at all: |
… | |
… | |
1522 | |
1772 | |
1523 | If the event loop is suspended for a long time, you can also force an |
1773 | If the event loop is suspended for a long time, you can also force an |
1524 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1774 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1525 | ()>. |
1775 | ()>. |
1526 | |
1776 | |
|
|
1777 | =head3 The special problems of suspended animation |
|
|
1778 | |
|
|
1779 | When you leave the server world it is quite customary to hit machines that |
|
|
1780 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1781 | |
|
|
1782 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1783 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1784 | to run until the system is suspended, but they will not advance while the |
|
|
1785 | system is suspended. That means, on resume, it will be as if the program |
|
|
1786 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1787 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1788 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1789 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1790 | be adjusted accordingly. |
|
|
1791 | |
|
|
1792 | I would not be surprised to see different behaviour in different between |
|
|
1793 | operating systems, OS versions or even different hardware. |
|
|
1794 | |
|
|
1795 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1796 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1797 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1798 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1799 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1800 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1801 | |
|
|
1802 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1803 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1804 | deterministic behaviour in this case (you can do nothing against |
|
|
1805 | C<SIGSTOP>). |
|
|
1806 | |
1527 | =head3 Watcher-Specific Functions and Data Members |
1807 | =head3 Watcher-Specific Functions and Data Members |
1528 | |
1808 | |
1529 | =over 4 |
1809 | =over 4 |
1530 | |
1810 | |
1531 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1811 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1554 | If the timer is started but non-repeating, stop it (as if it timed out). |
1834 | If the timer is started but non-repeating, stop it (as if it timed out). |
1555 | |
1835 | |
1556 | If the timer is repeating, either start it if necessary (with the |
1836 | If the timer is repeating, either start it if necessary (with the |
1557 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1837 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1558 | |
1838 | |
1559 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1839 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1560 | usage example. |
1840 | usage example. |
|
|
1841 | |
|
|
1842 | =item ev_timer_remaining (loop, ev_timer *) |
|
|
1843 | |
|
|
1844 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
1845 | then this time is relative to the current event loop time, otherwise it's |
|
|
1846 | the timeout value currently configured. |
|
|
1847 | |
|
|
1848 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
1849 | C<5>. When the timer is started and one second passes, C<ev_timer_remain> |
|
|
1850 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1851 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1852 | too), and so on. |
1561 | |
1853 | |
1562 | =item ev_tstamp repeat [read-write] |
1854 | =item ev_tstamp repeat [read-write] |
1563 | |
1855 | |
1564 | The current C<repeat> value. Will be used each time the watcher times out |
1856 | The current C<repeat> value. Will be used each time the watcher times out |
1565 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1857 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1624 | timers, such as triggering an event on each "midnight, local time", or |
1916 | timers, such as triggering an event on each "midnight, local time", or |
1625 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
1917 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
1626 | those cannot react to time jumps. |
1918 | those cannot react to time jumps. |
1627 | |
1919 | |
1628 | As with timers, the callback is guaranteed to be invoked only when the |
1920 | As with timers, the callback is guaranteed to be invoked only when the |
1629 | point in time where it is supposed to trigger has passed, but if multiple |
1921 | point in time where it is supposed to trigger has passed. If multiple |
1630 | periodic timers become ready during the same loop iteration, then order of |
1922 | timers become ready during the same loop iteration then the ones with |
1631 | execution is undefined. |
1923 | earlier time-out values are invoked before ones with later time-out values |
|
|
1924 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1632 | |
1925 | |
1633 | =head3 Watcher-Specific Functions and Data Members |
1926 | =head3 Watcher-Specific Functions and Data Members |
1634 | |
1927 | |
1635 | =over 4 |
1928 | =over 4 |
1636 | |
1929 | |
… | |
… | |
1800 | Signal watchers will trigger an event when the process receives a specific |
2093 | Signal watchers will trigger an event when the process receives a specific |
1801 | signal one or more times. Even though signals are very asynchronous, libev |
2094 | signal one or more times. Even though signals are very asynchronous, libev |
1802 | will try it's best to deliver signals synchronously, i.e. as part of the |
2095 | will try it's best to deliver signals synchronously, i.e. as part of the |
1803 | normal event processing, like any other event. |
2096 | normal event processing, like any other event. |
1804 | |
2097 | |
1805 | If you want signals asynchronously, just use C<sigaction> as you would |
2098 | If you want signals to be delivered truly asynchronously, just use |
1806 | do without libev and forget about sharing the signal. You can even use |
2099 | C<sigaction> as you would do without libev and forget about sharing |
1807 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2100 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2101 | synchronously wake up an event loop. |
1808 | |
2102 | |
1809 | You can configure as many watchers as you like per signal. Only when the |
2103 | You can configure as many watchers as you like for the same signal, but |
|
|
2104 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2105 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2106 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2107 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2108 | |
1810 | first watcher gets started will libev actually register a signal handler |
2109 | When the first watcher gets started will libev actually register something |
1811 | with the kernel (thus it coexists with your own signal handlers as long as |
2110 | with the kernel (thus it coexists with your own signal handlers as long as |
1812 | you don't register any with libev for the same signal). Similarly, when |
2111 | you don't register any with libev for the same signal). |
1813 | the last signal watcher for a signal is stopped, libev will reset the |
|
|
1814 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1815 | |
2112 | |
1816 | If possible and supported, libev will install its handlers with |
2113 | If possible and supported, libev will install its handlers with |
1817 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2114 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1818 | interrupted. If you have a problem with system calls getting interrupted by |
2115 | not be unduly interrupted. If you have a problem with system calls getting |
1819 | signals you can block all signals in an C<ev_check> watcher and unblock |
2116 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1820 | them in an C<ev_prepare> watcher. |
2117 | and unblock them in an C<ev_prepare> watcher. |
|
|
2118 | |
|
|
2119 | =head3 The special problem of inheritance over execve |
|
|
2120 | |
|
|
2121 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2122 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2123 | stopping it again), that is, libev might or might not block the signal, |
|
|
2124 | and might or might not set or restore the installed signal handler. |
|
|
2125 | |
|
|
2126 | While this does not matter for the signal disposition (libev never |
|
|
2127 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2128 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2129 | many signals to be blocked. |
|
|
2130 | |
|
|
2131 | This means that before calling C<exec> (from the child) you should reset |
|
|
2132 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2133 | choice usually). |
1821 | |
2134 | |
1822 | =head3 Watcher-Specific Functions and Data Members |
2135 | =head3 Watcher-Specific Functions and Data Members |
1823 | |
2136 | |
1824 | =over 4 |
2137 | =over 4 |
1825 | |
2138 | |
… | |
… | |
1857 | some child status changes (most typically when a child of yours dies or |
2170 | some child status changes (most typically when a child of yours dies or |
1858 | exits). It is permissible to install a child watcher I<after> the child |
2171 | exits). It is permissible to install a child watcher I<after> the child |
1859 | has been forked (which implies it might have already exited), as long |
2172 | has been forked (which implies it might have already exited), as long |
1860 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2173 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1861 | forking and then immediately registering a watcher for the child is fine, |
2174 | forking and then immediately registering a watcher for the child is fine, |
1862 | but forking and registering a watcher a few event loop iterations later is |
2175 | but forking and registering a watcher a few event loop iterations later or |
1863 | not. |
2176 | in the next callback invocation is not. |
1864 | |
2177 | |
1865 | Only the default event loop is capable of handling signals, and therefore |
2178 | Only the default event loop is capable of handling signals, and therefore |
1866 | you can only register child watchers in the default event loop. |
2179 | you can only register child watchers in the default event loop. |
1867 | |
2180 | |
|
|
2181 | Due to some design glitches inside libev, child watchers will always be |
|
|
2182 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2183 | libev) |
|
|
2184 | |
1868 | =head3 Process Interaction |
2185 | =head3 Process Interaction |
1869 | |
2186 | |
1870 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2187 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1871 | initialised. This is necessary to guarantee proper behaviour even if |
2188 | initialised. This is necessary to guarantee proper behaviour even if the |
1872 | the first child watcher is started after the child exits. The occurrence |
2189 | first child watcher is started after the child exits. The occurrence |
1873 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2190 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1874 | synchronously as part of the event loop processing. Libev always reaps all |
2191 | synchronously as part of the event loop processing. Libev always reaps all |
1875 | children, even ones not watched. |
2192 | children, even ones not watched. |
1876 | |
2193 | |
1877 | =head3 Overriding the Built-In Processing |
2194 | =head3 Overriding the Built-In Processing |
… | |
… | |
1887 | =head3 Stopping the Child Watcher |
2204 | =head3 Stopping the Child Watcher |
1888 | |
2205 | |
1889 | Currently, the child watcher never gets stopped, even when the |
2206 | Currently, the child watcher never gets stopped, even when the |
1890 | child terminates, so normally one needs to stop the watcher in the |
2207 | child terminates, so normally one needs to stop the watcher in the |
1891 | callback. Future versions of libev might stop the watcher automatically |
2208 | callback. Future versions of libev might stop the watcher automatically |
1892 | when a child exit is detected. |
2209 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2210 | problem). |
1893 | |
2211 | |
1894 | =head3 Watcher-Specific Functions and Data Members |
2212 | =head3 Watcher-Specific Functions and Data Members |
1895 | |
2213 | |
1896 | =over 4 |
2214 | =over 4 |
1897 | |
2215 | |
… | |
… | |
2223 | // no longer anything immediate to do. |
2541 | // no longer anything immediate to do. |
2224 | } |
2542 | } |
2225 | |
2543 | |
2226 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2544 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2227 | ev_idle_init (idle_watcher, idle_cb); |
2545 | ev_idle_init (idle_watcher, idle_cb); |
2228 | ev_idle_start (loop, idle_cb); |
2546 | ev_idle_start (loop, idle_watcher); |
2229 | |
2547 | |
2230 | |
2548 | |
2231 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2549 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2232 | |
2550 | |
2233 | Prepare and check watchers are usually (but not always) used in pairs: |
2551 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2326 | struct pollfd fds [nfd]; |
2644 | struct pollfd fds [nfd]; |
2327 | // actual code will need to loop here and realloc etc. |
2645 | // actual code will need to loop here and realloc etc. |
2328 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2646 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2329 | |
2647 | |
2330 | /* the callback is illegal, but won't be called as we stop during check */ |
2648 | /* the callback is illegal, but won't be called as we stop during check */ |
2331 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2649 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2332 | ev_timer_start (loop, &tw); |
2650 | ev_timer_start (loop, &tw); |
2333 | |
2651 | |
2334 | // create one ev_io per pollfd |
2652 | // create one ev_io per pollfd |
2335 | for (int i = 0; i < nfd; ++i) |
2653 | for (int i = 0; i < nfd; ++i) |
2336 | { |
2654 | { |
… | |
… | |
2566 | event loop blocks next and before C<ev_check> watchers are being called, |
2884 | event loop blocks next and before C<ev_check> watchers are being called, |
2567 | and only in the child after the fork. If whoever good citizen calling |
2885 | and only in the child after the fork. If whoever good citizen calling |
2568 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2886 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2569 | handlers will be invoked, too, of course. |
2887 | handlers will be invoked, too, of course. |
2570 | |
2888 | |
|
|
2889 | =head3 The special problem of life after fork - how is it possible? |
|
|
2890 | |
|
|
2891 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2892 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2893 | sequence should be handled by libev without any problems. |
|
|
2894 | |
|
|
2895 | This changes when the application actually wants to do event handling |
|
|
2896 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2897 | fork. |
|
|
2898 | |
|
|
2899 | The default mode of operation (for libev, with application help to detect |
|
|
2900 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2901 | when I<either> the parent I<or> the child process continues. |
|
|
2902 | |
|
|
2903 | When both processes want to continue using libev, then this is usually the |
|
|
2904 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2905 | supposed to continue with all watchers in place as before, while the other |
|
|
2906 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2907 | |
|
|
2908 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2909 | simply create a new event loop, which of course will be "empty", and |
|
|
2910 | use that for new watchers. This has the advantage of not touching more |
|
|
2911 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2912 | disadvantage of having to use multiple event loops (which do not support |
|
|
2913 | signal watchers). |
|
|
2914 | |
|
|
2915 | When this is not possible, or you want to use the default loop for |
|
|
2916 | other reasons, then in the process that wants to start "fresh", call |
|
|
2917 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2918 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2919 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2920 | also that in that case, you have to re-register any signal watchers. |
|
|
2921 | |
2571 | =head3 Watcher-Specific Functions and Data Members |
2922 | =head3 Watcher-Specific Functions and Data Members |
2572 | |
2923 | |
2573 | =over 4 |
2924 | =over 4 |
2574 | |
2925 | |
2575 | =item ev_fork_init (ev_signal *, callback) |
2926 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
3067 | =item Ocaml |
3418 | =item Ocaml |
3068 | |
3419 | |
3069 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3420 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3070 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3421 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3071 | |
3422 | |
|
|
3423 | =item Lua |
|
|
3424 | |
|
|
3425 | Brian Maher has written a partial interface to libev |
|
|
3426 | for lua (only C<ev_io> and C<ev_timer>), to be found at |
|
|
3427 | L<http://github.com/brimworks/lua-ev>. |
|
|
3428 | |
3072 | =back |
3429 | =back |
3073 | |
3430 | |
3074 | |
3431 | |
3075 | =head1 MACRO MAGIC |
3432 | =head1 MACRO MAGIC |
3076 | |
3433 | |
… | |
… | |
3242 | keeps libev from including F<config.h>, and it also defines dummy |
3599 | keeps libev from including F<config.h>, and it also defines dummy |
3243 | implementations for some libevent functions (such as logging, which is not |
3600 | implementations for some libevent functions (such as logging, which is not |
3244 | supported). It will also not define any of the structs usually found in |
3601 | supported). It will also not define any of the structs usually found in |
3245 | F<event.h> that are not directly supported by the libev core alone. |
3602 | F<event.h> that are not directly supported by the libev core alone. |
3246 | |
3603 | |
3247 | In stanbdalone mode, libev will still try to automatically deduce the |
3604 | In standalone mode, libev will still try to automatically deduce the |
3248 | configuration, but has to be more conservative. |
3605 | configuration, but has to be more conservative. |
3249 | |
3606 | |
3250 | =item EV_USE_MONOTONIC |
3607 | =item EV_USE_MONOTONIC |
3251 | |
3608 | |
3252 | If defined to be C<1>, libev will try to detect the availability of the |
3609 | If defined to be C<1>, libev will try to detect the availability of the |
… | |
… | |
3317 | be used is the winsock select). This means that it will call |
3674 | be used is the winsock select). This means that it will call |
3318 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3675 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3319 | it is assumed that all these functions actually work on fds, even |
3676 | it is assumed that all these functions actually work on fds, even |
3320 | on win32. Should not be defined on non-win32 platforms. |
3677 | on win32. Should not be defined on non-win32 platforms. |
3321 | |
3678 | |
3322 | =item EV_FD_TO_WIN32_HANDLE |
3679 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3323 | |
3680 | |
3324 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3681 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3325 | file descriptors to socket handles. When not defining this symbol (the |
3682 | file descriptors to socket handles. When not defining this symbol (the |
3326 | default), then libev will call C<_get_osfhandle>, which is usually |
3683 | default), then libev will call C<_get_osfhandle>, which is usually |
3327 | correct. In some cases, programs use their own file descriptor management, |
3684 | correct. In some cases, programs use their own file descriptor management, |
3328 | in which case they can provide this function to map fds to socket handles. |
3685 | in which case they can provide this function to map fds to socket handles. |
|
|
3686 | |
|
|
3687 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3688 | |
|
|
3689 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3690 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3691 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3692 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3693 | |
|
|
3694 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3695 | |
|
|
3696 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3697 | macro can be used to override the C<close> function, useful to unregister |
|
|
3698 | file descriptors again. Note that the replacement function has to close |
|
|
3699 | the underlying OS handle. |
3329 | |
3700 | |
3330 | =item EV_USE_POLL |
3701 | =item EV_USE_POLL |
3331 | |
3702 | |
3332 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3703 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3333 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3704 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3465 | defined to be C<0>, then they are not. |
3836 | defined to be C<0>, then they are not. |
3466 | |
3837 | |
3467 | =item EV_MINIMAL |
3838 | =item EV_MINIMAL |
3468 | |
3839 | |
3469 | If you need to shave off some kilobytes of code at the expense of some |
3840 | If you need to shave off some kilobytes of code at the expense of some |
3470 | speed, define this symbol to C<1>. Currently this is used to override some |
3841 | speed (but with the full API), define this symbol to C<1>. Currently this |
3471 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3842 | is used to override some inlining decisions, saves roughly 30% code size |
3472 | much smaller 2-heap for timer management over the default 4-heap. |
3843 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3844 | the default 4-heap. |
|
|
3845 | |
|
|
3846 | You can save even more by disabling watcher types you do not need |
|
|
3847 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3848 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3849 | |
|
|
3850 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3851 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3852 | of the API are still available, and do not complain if this subset changes |
|
|
3853 | over time. |
|
|
3854 | |
|
|
3855 | =item EV_NSIG |
|
|
3856 | |
|
|
3857 | The highest supported signal number, +1 (or, the number of |
|
|
3858 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3859 | automatically, but sometimes this fails, in which case it can be |
|
|
3860 | specified. Also, using a lower number than detected (C<32> should be |
|
|
3861 | good for about any system in existance) can save some memory, as libev |
|
|
3862 | statically allocates some 12-24 bytes per signal number. |
3473 | |
3863 | |
3474 | =item EV_PID_HASHSIZE |
3864 | =item EV_PID_HASHSIZE |
3475 | |
3865 | |
3476 | C<ev_child> watchers use a small hash table to distribute workload by |
3866 | C<ev_child> watchers use a small hash table to distribute workload by |
3477 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3867 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3663 | default loop and triggering an C<ev_async> watcher from the default loop |
4053 | default loop and triggering an C<ev_async> watcher from the default loop |
3664 | watcher callback into the event loop interested in the signal. |
4054 | watcher callback into the event loop interested in the signal. |
3665 | |
4055 | |
3666 | =back |
4056 | =back |
3667 | |
4057 | |
|
|
4058 | =head4 THREAD LOCKING EXAMPLE |
|
|
4059 | |
|
|
4060 | Here is a fictitious example of how to run an event loop in a different |
|
|
4061 | thread than where callbacks are being invoked and watchers are |
|
|
4062 | created/added/removed. |
|
|
4063 | |
|
|
4064 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4065 | which uses exactly this technique (which is suited for many high-level |
|
|
4066 | languages). |
|
|
4067 | |
|
|
4068 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4069 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4070 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4071 | |
|
|
4072 | First, you need to associate some data with the event loop: |
|
|
4073 | |
|
|
4074 | typedef struct { |
|
|
4075 | mutex_t lock; /* global loop lock */ |
|
|
4076 | ev_async async_w; |
|
|
4077 | thread_t tid; |
|
|
4078 | cond_t invoke_cv; |
|
|
4079 | } userdata; |
|
|
4080 | |
|
|
4081 | void prepare_loop (EV_P) |
|
|
4082 | { |
|
|
4083 | // for simplicity, we use a static userdata struct. |
|
|
4084 | static userdata u; |
|
|
4085 | |
|
|
4086 | ev_async_init (&u->async_w, async_cb); |
|
|
4087 | ev_async_start (EV_A_ &u->async_w); |
|
|
4088 | |
|
|
4089 | pthread_mutex_init (&u->lock, 0); |
|
|
4090 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4091 | |
|
|
4092 | // now associate this with the loop |
|
|
4093 | ev_set_userdata (EV_A_ u); |
|
|
4094 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4095 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4096 | |
|
|
4097 | // then create the thread running ev_loop |
|
|
4098 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4099 | } |
|
|
4100 | |
|
|
4101 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4102 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4103 | that might have been added: |
|
|
4104 | |
|
|
4105 | static void |
|
|
4106 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4107 | { |
|
|
4108 | // just used for the side effects |
|
|
4109 | } |
|
|
4110 | |
|
|
4111 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4112 | protecting the loop data, respectively. |
|
|
4113 | |
|
|
4114 | static void |
|
|
4115 | l_release (EV_P) |
|
|
4116 | { |
|
|
4117 | userdata *u = ev_userdata (EV_A); |
|
|
4118 | pthread_mutex_unlock (&u->lock); |
|
|
4119 | } |
|
|
4120 | |
|
|
4121 | static void |
|
|
4122 | l_acquire (EV_P) |
|
|
4123 | { |
|
|
4124 | userdata *u = ev_userdata (EV_A); |
|
|
4125 | pthread_mutex_lock (&u->lock); |
|
|
4126 | } |
|
|
4127 | |
|
|
4128 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4129 | into C<ev_loop>: |
|
|
4130 | |
|
|
4131 | void * |
|
|
4132 | l_run (void *thr_arg) |
|
|
4133 | { |
|
|
4134 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4135 | |
|
|
4136 | l_acquire (EV_A); |
|
|
4137 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4138 | ev_loop (EV_A_ 0); |
|
|
4139 | l_release (EV_A); |
|
|
4140 | |
|
|
4141 | return 0; |
|
|
4142 | } |
|
|
4143 | |
|
|
4144 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4145 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4146 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4147 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4148 | and b) skipping inter-thread-communication when there are no pending |
|
|
4149 | watchers is very beneficial): |
|
|
4150 | |
|
|
4151 | static void |
|
|
4152 | l_invoke (EV_P) |
|
|
4153 | { |
|
|
4154 | userdata *u = ev_userdata (EV_A); |
|
|
4155 | |
|
|
4156 | while (ev_pending_count (EV_A)) |
|
|
4157 | { |
|
|
4158 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4159 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4160 | } |
|
|
4161 | } |
|
|
4162 | |
|
|
4163 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4164 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4165 | thread to continue: |
|
|
4166 | |
|
|
4167 | static void |
|
|
4168 | real_invoke_pending (EV_P) |
|
|
4169 | { |
|
|
4170 | userdata *u = ev_userdata (EV_A); |
|
|
4171 | |
|
|
4172 | pthread_mutex_lock (&u->lock); |
|
|
4173 | ev_invoke_pending (EV_A); |
|
|
4174 | pthread_cond_signal (&u->invoke_cv); |
|
|
4175 | pthread_mutex_unlock (&u->lock); |
|
|
4176 | } |
|
|
4177 | |
|
|
4178 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4179 | event loop, you will now have to lock: |
|
|
4180 | |
|
|
4181 | ev_timer timeout_watcher; |
|
|
4182 | userdata *u = ev_userdata (EV_A); |
|
|
4183 | |
|
|
4184 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4185 | |
|
|
4186 | pthread_mutex_lock (&u->lock); |
|
|
4187 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4188 | ev_async_send (EV_A_ &u->async_w); |
|
|
4189 | pthread_mutex_unlock (&u->lock); |
|
|
4190 | |
|
|
4191 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4192 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4193 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4194 | watchers in the next event loop iteration. |
|
|
4195 | |
3668 | =head3 COROUTINES |
4196 | =head3 COROUTINES |
3669 | |
4197 | |
3670 | Libev is very accommodating to coroutines ("cooperative threads"): |
4198 | Libev is very accommodating to coroutines ("cooperative threads"): |
3671 | libev fully supports nesting calls to its functions from different |
4199 | libev fully supports nesting calls to its functions from different |
3672 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4200 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3673 | different coroutines, and switch freely between both coroutines running the |
4201 | different coroutines, and switch freely between both coroutines running |
3674 | loop, as long as you don't confuse yourself). The only exception is that |
4202 | the loop, as long as you don't confuse yourself). The only exception is |
3675 | you must not do this from C<ev_periodic> reschedule callbacks. |
4203 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3676 | |
4204 | |
3677 | Care has been taken to ensure that libev does not keep local state inside |
4205 | Care has been taken to ensure that libev does not keep local state inside |
3678 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4206 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3679 | they do not call any callbacks. |
4207 | they do not call any callbacks. |
3680 | |
4208 | |
… | |
… | |
3757 | way (note also that glib is the slowest event library known to man). |
4285 | way (note also that glib is the slowest event library known to man). |
3758 | |
4286 | |
3759 | There is no supported compilation method available on windows except |
4287 | There is no supported compilation method available on windows except |
3760 | embedding it into other applications. |
4288 | embedding it into other applications. |
3761 | |
4289 | |
|
|
4290 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4291 | tries its best, but under most conditions, signals will simply not work. |
|
|
4292 | |
3762 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4293 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3763 | accept large writes: instead of resulting in a partial write, windows will |
4294 | accept large writes: instead of resulting in a partial write, windows will |
3764 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4295 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3765 | so make sure you only write small amounts into your sockets (less than a |
4296 | so make sure you only write small amounts into your sockets (less than a |
3766 | megabyte seems safe, but this apparently depends on the amount of memory |
4297 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3770 | the abysmal performance of winsockets, using a large number of sockets |
4301 | the abysmal performance of winsockets, using a large number of sockets |
3771 | is not recommended (and not reasonable). If your program needs to use |
4302 | is not recommended (and not reasonable). If your program needs to use |
3772 | more than a hundred or so sockets, then likely it needs to use a totally |
4303 | more than a hundred or so sockets, then likely it needs to use a totally |
3773 | different implementation for windows, as libev offers the POSIX readiness |
4304 | different implementation for windows, as libev offers the POSIX readiness |
3774 | notification model, which cannot be implemented efficiently on windows |
4305 | notification model, which cannot be implemented efficiently on windows |
3775 | (Microsoft monopoly games). |
4306 | (due to Microsoft monopoly games). |
3776 | |
4307 | |
3777 | A typical way to use libev under windows is to embed it (see the embedding |
4308 | A typical way to use libev under windows is to embed it (see the embedding |
3778 | section for details) and use the following F<evwrap.h> header file instead |
4309 | section for details) and use the following F<evwrap.h> header file instead |
3779 | of F<ev.h>: |
4310 | of F<ev.h>: |
3780 | |
4311 | |
… | |
… | |
3816 | |
4347 | |
3817 | Early versions of winsocket's select only supported waiting for a maximum |
4348 | Early versions of winsocket's select only supported waiting for a maximum |
3818 | of C<64> handles (probably owning to the fact that all windows kernels |
4349 | of C<64> handles (probably owning to the fact that all windows kernels |
3819 | can only wait for C<64> things at the same time internally; Microsoft |
4350 | can only wait for C<64> things at the same time internally; Microsoft |
3820 | recommends spawning a chain of threads and wait for 63 handles and the |
4351 | recommends spawning a chain of threads and wait for 63 handles and the |
3821 | previous thread in each. Great). |
4352 | previous thread in each. Sounds great!). |
3822 | |
4353 | |
3823 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4354 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3824 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4355 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3825 | call (which might be in libev or elsewhere, for example, perl does its own |
4356 | call (which might be in libev or elsewhere, for example, perl and many |
3826 | select emulation on windows). |
4357 | other interpreters do their own select emulation on windows). |
3827 | |
4358 | |
3828 | Another limit is the number of file descriptors in the Microsoft runtime |
4359 | Another limit is the number of file descriptors in the Microsoft runtime |
3829 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4360 | libraries, which by default is C<64> (there must be a hidden I<64> |
3830 | or something like this inside Microsoft). You can increase this by calling |
4361 | fetish or something like this inside Microsoft). You can increase this |
3831 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4362 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3832 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4363 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3833 | libraries. |
|
|
3834 | |
|
|
3835 | This might get you to about C<512> or C<2048> sockets (depending on |
4364 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3836 | windows version and/or the phase of the moon). To get more, you need to |
4365 | (depending on windows version and/or the phase of the moon). To get more, |
3837 | wrap all I/O functions and provide your own fd management, but the cost of |
4366 | you need to wrap all I/O functions and provide your own fd management, but |
3838 | calling select (O(n²)) will likely make this unworkable. |
4367 | the cost of calling select (O(n²)) will likely make this unworkable. |
3839 | |
4368 | |
3840 | =back |
4369 | =back |
3841 | |
4370 | |
3842 | =head2 PORTABILITY REQUIREMENTS |
4371 | =head2 PORTABILITY REQUIREMENTS |
3843 | |
4372 | |
… | |
… | |
3886 | =item C<double> must hold a time value in seconds with enough accuracy |
4415 | =item C<double> must hold a time value in seconds with enough accuracy |
3887 | |
4416 | |
3888 | The type C<double> is used to represent timestamps. It is required to |
4417 | The type C<double> is used to represent timestamps. It is required to |
3889 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4418 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3890 | enough for at least into the year 4000. This requirement is fulfilled by |
4419 | enough for at least into the year 4000. This requirement is fulfilled by |
3891 | implementations implementing IEEE 754 (basically all existing ones). |
4420 | implementations implementing IEEE 754, which is basically all existing |
|
|
4421 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4422 | 2200. |
3892 | |
4423 | |
3893 | =back |
4424 | =back |
3894 | |
4425 | |
3895 | If you know of other additional requirements drop me a note. |
4426 | If you know of other additional requirements drop me a note. |
3896 | |
4427 | |
… | |
… | |
3964 | involves iterating over all running async watchers or all signal numbers. |
4495 | involves iterating over all running async watchers or all signal numbers. |
3965 | |
4496 | |
3966 | =back |
4497 | =back |
3967 | |
4498 | |
3968 | |
4499 | |
|
|
4500 | =head1 GLOSSARY |
|
|
4501 | |
|
|
4502 | =over 4 |
|
|
4503 | |
|
|
4504 | =item active |
|
|
4505 | |
|
|
4506 | A watcher is active as long as it has been started (has been attached to |
|
|
4507 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4508 | |
|
|
4509 | =item application |
|
|
4510 | |
|
|
4511 | In this document, an application is whatever is using libev. |
|
|
4512 | |
|
|
4513 | =item callback |
|
|
4514 | |
|
|
4515 | The address of a function that is called when some event has been |
|
|
4516 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4517 | received the event, and the actual event bitset. |
|
|
4518 | |
|
|
4519 | =item callback invocation |
|
|
4520 | |
|
|
4521 | The act of calling the callback associated with a watcher. |
|
|
4522 | |
|
|
4523 | =item event |
|
|
4524 | |
|
|
4525 | A change of state of some external event, such as data now being available |
|
|
4526 | for reading on a file descriptor, time having passed or simply not having |
|
|
4527 | any other events happening anymore. |
|
|
4528 | |
|
|
4529 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4530 | C<EV_TIMEOUT>). |
|
|
4531 | |
|
|
4532 | =item event library |
|
|
4533 | |
|
|
4534 | A software package implementing an event model and loop. |
|
|
4535 | |
|
|
4536 | =item event loop |
|
|
4537 | |
|
|
4538 | An entity that handles and processes external events and converts them |
|
|
4539 | into callback invocations. |
|
|
4540 | |
|
|
4541 | =item event model |
|
|
4542 | |
|
|
4543 | The model used to describe how an event loop handles and processes |
|
|
4544 | watchers and events. |
|
|
4545 | |
|
|
4546 | =item pending |
|
|
4547 | |
|
|
4548 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4549 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4550 | pending status is explicitly cleared by the application. |
|
|
4551 | |
|
|
4552 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4553 | its pending status. |
|
|
4554 | |
|
|
4555 | =item real time |
|
|
4556 | |
|
|
4557 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4558 | |
|
|
4559 | =item wall-clock time |
|
|
4560 | |
|
|
4561 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4562 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4563 | clock. |
|
|
4564 | |
|
|
4565 | =item watcher |
|
|
4566 | |
|
|
4567 | A data structure that describes interest in certain events. Watchers need |
|
|
4568 | to be started (attached to an event loop) before they can receive events. |
|
|
4569 | |
|
|
4570 | =item watcher invocation |
|
|
4571 | |
|
|
4572 | The act of calling the callback associated with a watcher. |
|
|
4573 | |
|
|
4574 | =back |
|
|
4575 | |
3969 | =head1 AUTHOR |
4576 | =head1 AUTHOR |
3970 | |
4577 | |
3971 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
4578 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3972 | |
4579 | |