… | |
… | |
98 | =head2 FEATURES |
98 | =head2 FEATURES |
99 | |
99 | |
100 | 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 |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
102 | 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 |
103 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
104 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
105 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
106 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
107 | 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 |
108 | 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 |
109 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
|
|
110 | limited support for fork events (C<ev_fork>). |
110 | |
111 | |
111 | It also is quite fast (see this |
112 | It also is quite fast (see this |
112 | 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 |
113 | for example). |
114 | for example). |
114 | |
115 | |
… | |
… | |
361 | 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 |
362 | flag. |
363 | flag. |
363 | |
364 | |
364 | 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> |
365 | environment variable. |
366 | environment variable. |
|
|
367 | |
|
|
368 | =item C<EVFLAG_NOINOTIFY> |
|
|
369 | |
|
|
370 | When this flag is specified, then libev will not attempt to use the |
|
|
371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
|
|
372 | testing, this flag can be useful to conserve inotify file descriptors, as |
|
|
373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
|
|
374 | |
|
|
375 | =item C<EVFLAG_NOSIGNALFD> |
|
|
376 | |
|
|
377 | When this flag is specified, then libev will not attempt to use the |
|
|
378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is |
|
|
379 | probably only useful to work around any bugs in libev. Consequently, this |
|
|
380 | flag might go away once the signalfd functionality is considered stable, |
|
|
381 | so it's useful mostly in environment variables and not in program code. |
366 | |
382 | |
367 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
383 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
368 | |
384 | |
369 | 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 |
370 | 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, |
… | |
… | |
518 | |
534 | |
519 | It is definitely not recommended to use this flag. |
535 | It is definitely not recommended to use this flag. |
520 | |
536 | |
521 | =back |
537 | =back |
522 | |
538 | |
523 | 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, |
524 | 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 |
525 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
541 | here). If none are specified, all backends in C<ev_recommended_backends |
|
|
542 | ()> will be tried. |
526 | |
543 | |
527 | Example: This is the most typical usage. |
544 | Example: This is the most typical usage. |
528 | |
545 | |
529 | if (!ev_default_loop (0)) |
546 | if (!ev_default_loop (0)) |
530 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
547 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
… | |
… | |
620 | happily wraps around with enough iterations. |
637 | happily wraps around with enough iterations. |
621 | |
638 | |
622 | 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 |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
640 | "ticks" the number of loop iterations), as it roughly corresponds with |
624 | C<ev_prepare> and C<ev_check> calls. |
641 | C<ev_prepare> and C<ev_check> calls. |
|
|
642 | |
|
|
643 | =item unsigned int ev_loop_depth (loop) |
|
|
644 | |
|
|
645 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
646 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
647 | |
|
|
648 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
|
|
649 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
|
|
650 | in which case it is higher. |
|
|
651 | |
|
|
652 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
653 | etc.), doesn't count as exit. |
625 | |
654 | |
626 | =item unsigned int ev_backend (loop) |
655 | =item unsigned int ev_backend (loop) |
627 | |
656 | |
628 | 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 |
629 | use. |
658 | use. |
… | |
… | |
811 | |
840 | |
812 | 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 |
813 | 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, |
814 | 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 |
815 | 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 |
816 | 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. |
817 | |
848 | |
818 | 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 |
819 | to spend more time collecting timeouts, at the expense of increased |
850 | to spend more time collecting timeouts, at the expense of increased |
820 | latency/jitter/inexactness (the watcher callback will be called |
851 | latency/jitter/inexactness (the watcher callback will be called |
821 | 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 |
… | |
… | |
823 | |
854 | |
824 | 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 |
825 | 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 |
826 | interactive servers (of course not for games), likewise for timeouts. It |
857 | interactive servers (of course not for games), likewise for timeouts. It |
827 | 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>, |
828 | 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). |
829 | |
864 | |
830 | Setting the I<timeout collect interval> can improve the opportunity for |
865 | Setting the I<timeout collect interval> can improve the opportunity for |
831 | saving power, as the program will "bundle" timer callback invocations that |
866 | saving power, as the program will "bundle" timer callback invocations that |
832 | 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 |
833 | 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 |
834 | 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 |
835 | 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 |
|
|
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 |
|
|
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 |
|
|
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. |
836 | |
942 | |
837 | =item ev_loop_verify (loop) |
943 | =item ev_loop_verify (loop) |
838 | |
944 | |
839 | 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 |
840 | 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 |
… | |
… | |
1468 | |
1574 | |
1469 | 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 |
1470 | passed (not I<at>, so on systems with very low-resolution clocks this |
1576 | passed (not I<at>, so on systems with very low-resolution clocks this |
1471 | might introduce a small delay). If multiple timers become ready during the |
1577 | might introduce a small delay). If multiple timers become ready during the |
1472 | same loop iteration then the ones with earlier time-out values are invoked |
1578 | same loop iteration then the ones with earlier time-out values are invoked |
1473 | before ones with later time-out values (but this is no longer true when a |
1579 | before ones of the same priority with later time-out values (but this is |
1474 | callback calls C<ev_loop> recursively). |
1580 | no longer true when a callback calls C<ev_loop> recursively). |
1475 | |
1581 | |
1476 | =head3 Be smart about timeouts |
1582 | =head3 Be smart about timeouts |
1477 | |
1583 | |
1478 | 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 |
1479 | 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, |
… | |
… | |
1523 | 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> |
1524 | member and C<ev_timer_again>. |
1630 | member and C<ev_timer_again>. |
1525 | |
1631 | |
1526 | At start: |
1632 | At start: |
1527 | |
1633 | |
1528 | ev_timer_init (timer, callback); |
1634 | ev_init (timer, callback); |
1529 | timer->repeat = 60.; |
1635 | timer->repeat = 60.; |
1530 | ev_timer_again (loop, timer); |
1636 | ev_timer_again (loop, timer); |
1531 | |
1637 | |
1532 | Each time there is some activity: |
1638 | Each time there is some activity: |
1533 | |
1639 | |
… | |
… | |
1595 | |
1701 | |
1596 | 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> |
1597 | 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 |
1598 | callback, which will "do the right thing" and start the timer: |
1704 | callback, which will "do the right thing" and start the timer: |
1599 | |
1705 | |
1600 | ev_timer_init (timer, callback); |
1706 | ev_init (timer, callback); |
1601 | last_activity = ev_now (loop); |
1707 | last_activity = ev_now (loop); |
1602 | callback (loop, timer, EV_TIMEOUT); |
1708 | callback (loop, timer, EV_TIMEOUT); |
1603 | |
1709 | |
1604 | 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 |
1605 | C<last_activity>, no libev calls at all: |
1711 | C<last_activity>, no libev calls at all: |
… | |
… | |
1666 | |
1772 | |
1667 | 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 |
1668 | 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 |
1669 | ()>. |
1775 | ()>. |
1670 | |
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 | |
1671 | =head3 Watcher-Specific Functions and Data Members |
1807 | =head3 Watcher-Specific Functions and Data Members |
1672 | |
1808 | |
1673 | =over 4 |
1809 | =over 4 |
1674 | |
1810 | |
1675 | =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) |
… | |
… | |
1700 | 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 |
1701 | 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. |
1702 | |
1838 | |
1703 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1839 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1704 | 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. |
1705 | |
1853 | |
1706 | =item ev_tstamp repeat [read-write] |
1854 | =item ev_tstamp repeat [read-write] |
1707 | |
1855 | |
1708 | 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 |
1709 | 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), |
… | |
… | |
1945 | 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 |
1946 | 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 |
1947 | 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 |
1948 | normal event processing, like any other event. |
2096 | normal event processing, like any other event. |
1949 | |
2097 | |
1950 | If you want signals asynchronously, just use C<sigaction> as you would |
2098 | If you want signals to be delivered truly asynchronously, just use |
1951 | 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 |
1952 | 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. |
1953 | |
2102 | |
1954 | 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 | |
1955 | first watcher gets started will libev actually register a signal handler |
2109 | When the first watcher gets started will libev actually register something |
1956 | 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 |
1957 | 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). |
1958 | the last signal watcher for a signal is stopped, libev will reset the |
2112 | |
1959 | signal handler to SIG_DFL (regardless of what it was set to before). |
2113 | Both the signal mask state (C<sigprocmask>) and the signal handler state |
|
|
2114 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2115 | sotpping it again), that is, libev might or might not block the signal, |
|
|
2116 | and might or might not set or restore the installed signal handler. |
1960 | |
2117 | |
1961 | If possible and supported, libev will install its handlers with |
2118 | If possible and supported, libev will install its handlers with |
1962 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2119 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1963 | interrupted. If you have a problem with system calls getting interrupted by |
2120 | not be unduly interrupted. If you have a problem with system calls getting |
1964 | signals you can block all signals in an C<ev_check> watcher and unblock |
2121 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1965 | them in an C<ev_prepare> watcher. |
2122 | and unblock them in an C<ev_prepare> watcher. |
1966 | |
2123 | |
1967 | =head3 Watcher-Specific Functions and Data Members |
2124 | =head3 Watcher-Specific Functions and Data Members |
1968 | |
2125 | |
1969 | =over 4 |
2126 | =over 4 |
1970 | |
2127 | |
… | |
… | |
2002 | some child status changes (most typically when a child of yours dies or |
2159 | some child status changes (most typically when a child of yours dies or |
2003 | exits). It is permissible to install a child watcher I<after> the child |
2160 | exits). It is permissible to install a child watcher I<after> the child |
2004 | has been forked (which implies it might have already exited), as long |
2161 | has been forked (which implies it might have already exited), as long |
2005 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2162 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2006 | forking and then immediately registering a watcher for the child is fine, |
2163 | forking and then immediately registering a watcher for the child is fine, |
2007 | but forking and registering a watcher a few event loop iterations later is |
2164 | but forking and registering a watcher a few event loop iterations later or |
2008 | not. |
2165 | in the next callback invocation is not. |
2009 | |
2166 | |
2010 | Only the default event loop is capable of handling signals, and therefore |
2167 | Only the default event loop is capable of handling signals, and therefore |
2011 | you can only register child watchers in the default event loop. |
2168 | you can only register child watchers in the default event loop. |
2012 | |
2169 | |
|
|
2170 | Due to some design glitches inside libev, child watchers will always be |
|
|
2171 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2172 | libev) |
|
|
2173 | |
2013 | =head3 Process Interaction |
2174 | =head3 Process Interaction |
2014 | |
2175 | |
2015 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2176 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2016 | initialised. This is necessary to guarantee proper behaviour even if |
2177 | initialised. This is necessary to guarantee proper behaviour even if the |
2017 | the first child watcher is started after the child exits. The occurrence |
2178 | first child watcher is started after the child exits. The occurrence |
2018 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2179 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2019 | synchronously as part of the event loop processing. Libev always reaps all |
2180 | synchronously as part of the event loop processing. Libev always reaps all |
2020 | children, even ones not watched. |
2181 | children, even ones not watched. |
2021 | |
2182 | |
2022 | =head3 Overriding the Built-In Processing |
2183 | =head3 Overriding the Built-In Processing |
… | |
… | |
2032 | =head3 Stopping the Child Watcher |
2193 | =head3 Stopping the Child Watcher |
2033 | |
2194 | |
2034 | Currently, the child watcher never gets stopped, even when the |
2195 | Currently, the child watcher never gets stopped, even when the |
2035 | child terminates, so normally one needs to stop the watcher in the |
2196 | child terminates, so normally one needs to stop the watcher in the |
2036 | callback. Future versions of libev might stop the watcher automatically |
2197 | callback. Future versions of libev might stop the watcher automatically |
2037 | when a child exit is detected. |
2198 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2199 | problem). |
2038 | |
2200 | |
2039 | =head3 Watcher-Specific Functions and Data Members |
2201 | =head3 Watcher-Specific Functions and Data Members |
2040 | |
2202 | |
2041 | =over 4 |
2203 | =over 4 |
2042 | |
2204 | |
… | |
… | |
2471 | struct pollfd fds [nfd]; |
2633 | struct pollfd fds [nfd]; |
2472 | // actual code will need to loop here and realloc etc. |
2634 | // actual code will need to loop here and realloc etc. |
2473 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2635 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2474 | |
2636 | |
2475 | /* the callback is illegal, but won't be called as we stop during check */ |
2637 | /* the callback is illegal, but won't be called as we stop during check */ |
2476 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2638 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2477 | ev_timer_start (loop, &tw); |
2639 | ev_timer_start (loop, &tw); |
2478 | |
2640 | |
2479 | // create one ev_io per pollfd |
2641 | // create one ev_io per pollfd |
2480 | for (int i = 0; i < nfd; ++i) |
2642 | for (int i = 0; i < nfd; ++i) |
2481 | { |
2643 | { |
… | |
… | |
3245 | =item Ocaml |
3407 | =item Ocaml |
3246 | |
3408 | |
3247 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3409 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3248 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3410 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3249 | |
3411 | |
|
|
3412 | =item Lua |
|
|
3413 | |
|
|
3414 | Brian Maher has written a partial interface to libev |
|
|
3415 | for lua (only C<ev_io> and C<ev_timer>), to be found at |
|
|
3416 | L<http://github.com/brimworks/lua-ev>. |
|
|
3417 | |
3250 | =back |
3418 | =back |
3251 | |
3419 | |
3252 | |
3420 | |
3253 | =head1 MACRO MAGIC |
3421 | =head1 MACRO MAGIC |
3254 | |
3422 | |
… | |
… | |
3420 | keeps libev from including F<config.h>, and it also defines dummy |
3588 | keeps libev from including F<config.h>, and it also defines dummy |
3421 | implementations for some libevent functions (such as logging, which is not |
3589 | implementations for some libevent functions (such as logging, which is not |
3422 | supported). It will also not define any of the structs usually found in |
3590 | supported). It will also not define any of the structs usually found in |
3423 | F<event.h> that are not directly supported by the libev core alone. |
3591 | F<event.h> that are not directly supported by the libev core alone. |
3424 | |
3592 | |
3425 | In stanbdalone mode, libev will still try to automatically deduce the |
3593 | In standalone mode, libev will still try to automatically deduce the |
3426 | configuration, but has to be more conservative. |
3594 | configuration, but has to be more conservative. |
3427 | |
3595 | |
3428 | =item EV_USE_MONOTONIC |
3596 | =item EV_USE_MONOTONIC |
3429 | |
3597 | |
3430 | If defined to be C<1>, libev will try to detect the availability of the |
3598 | If defined to be C<1>, libev will try to detect the availability of the |
… | |
… | |
3495 | be used is the winsock select). This means that it will call |
3663 | be used is the winsock select). This means that it will call |
3496 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3664 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3497 | it is assumed that all these functions actually work on fds, even |
3665 | it is assumed that all these functions actually work on fds, even |
3498 | on win32. Should not be defined on non-win32 platforms. |
3666 | on win32. Should not be defined on non-win32 platforms. |
3499 | |
3667 | |
3500 | =item EV_FD_TO_WIN32_HANDLE |
3668 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3501 | |
3669 | |
3502 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3670 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3503 | file descriptors to socket handles. When not defining this symbol (the |
3671 | file descriptors to socket handles. When not defining this symbol (the |
3504 | default), then libev will call C<_get_osfhandle>, which is usually |
3672 | default), then libev will call C<_get_osfhandle>, which is usually |
3505 | correct. In some cases, programs use their own file descriptor management, |
3673 | correct. In some cases, programs use their own file descriptor management, |
3506 | in which case they can provide this function to map fds to socket handles. |
3674 | in which case they can provide this function to map fds to socket handles. |
|
|
3675 | |
|
|
3676 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3677 | |
|
|
3678 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3679 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3680 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3681 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3682 | |
|
|
3683 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3684 | |
|
|
3685 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3686 | macro can be used to override the C<close> function, useful to unregister |
|
|
3687 | file descriptors again. Note that the replacement function has to close |
|
|
3688 | the underlying OS handle. |
3507 | |
3689 | |
3508 | =item EV_USE_POLL |
3690 | =item EV_USE_POLL |
3509 | |
3691 | |
3510 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3692 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3511 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3693 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3643 | defined to be C<0>, then they are not. |
3825 | defined to be C<0>, then they are not. |
3644 | |
3826 | |
3645 | =item EV_MINIMAL |
3827 | =item EV_MINIMAL |
3646 | |
3828 | |
3647 | If you need to shave off some kilobytes of code at the expense of some |
3829 | If you need to shave off some kilobytes of code at the expense of some |
3648 | speed, define this symbol to C<1>. Currently this is used to override some |
3830 | speed (but with the full API), define this symbol to C<1>. Currently this |
3649 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3831 | is used to override some inlining decisions, saves roughly 30% code size |
3650 | much smaller 2-heap for timer management over the default 4-heap. |
3832 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3833 | the default 4-heap. |
|
|
3834 | |
|
|
3835 | You can save even more by disabling watcher types you do not need |
|
|
3836 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3837 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3838 | |
|
|
3839 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3840 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3841 | of the API are still available, and do not complain if this subset changes |
|
|
3842 | over time. |
|
|
3843 | |
|
|
3844 | =item EV_NSIG |
|
|
3845 | |
|
|
3846 | The highest supported signal number, +1 (or, the number of |
|
|
3847 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3848 | automatically, but sometimes this fails, in which case it can be |
|
|
3849 | specified. Also, using a lower number than detected (C<32> should be |
|
|
3850 | good for about any system in existance) can save some memory, as libev |
|
|
3851 | statically allocates some 12-24 bytes per signal number. |
3651 | |
3852 | |
3652 | =item EV_PID_HASHSIZE |
3853 | =item EV_PID_HASHSIZE |
3653 | |
3854 | |
3654 | C<ev_child> watchers use a small hash table to distribute workload by |
3855 | C<ev_child> watchers use a small hash table to distribute workload by |
3655 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3856 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3841 | default loop and triggering an C<ev_async> watcher from the default loop |
4042 | default loop and triggering an C<ev_async> watcher from the default loop |
3842 | watcher callback into the event loop interested in the signal. |
4043 | watcher callback into the event loop interested in the signal. |
3843 | |
4044 | |
3844 | =back |
4045 | =back |
3845 | |
4046 | |
|
|
4047 | =head4 THREAD LOCKING EXAMPLE |
|
|
4048 | |
|
|
4049 | Here is a fictitious example of how to run an event loop in a different |
|
|
4050 | thread than where callbacks are being invoked and watchers are |
|
|
4051 | created/added/removed. |
|
|
4052 | |
|
|
4053 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4054 | which uses exactly this technique (which is suited for many high-level |
|
|
4055 | languages). |
|
|
4056 | |
|
|
4057 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4058 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4059 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4060 | |
|
|
4061 | First, you need to associate some data with the event loop: |
|
|
4062 | |
|
|
4063 | typedef struct { |
|
|
4064 | mutex_t lock; /* global loop lock */ |
|
|
4065 | ev_async async_w; |
|
|
4066 | thread_t tid; |
|
|
4067 | cond_t invoke_cv; |
|
|
4068 | } userdata; |
|
|
4069 | |
|
|
4070 | void prepare_loop (EV_P) |
|
|
4071 | { |
|
|
4072 | // for simplicity, we use a static userdata struct. |
|
|
4073 | static userdata u; |
|
|
4074 | |
|
|
4075 | ev_async_init (&u->async_w, async_cb); |
|
|
4076 | ev_async_start (EV_A_ &u->async_w); |
|
|
4077 | |
|
|
4078 | pthread_mutex_init (&u->lock, 0); |
|
|
4079 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4080 | |
|
|
4081 | // now associate this with the loop |
|
|
4082 | ev_set_userdata (EV_A_ u); |
|
|
4083 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4084 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4085 | |
|
|
4086 | // then create the thread running ev_loop |
|
|
4087 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4088 | } |
|
|
4089 | |
|
|
4090 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4091 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4092 | that might have been added: |
|
|
4093 | |
|
|
4094 | static void |
|
|
4095 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4096 | { |
|
|
4097 | // just used for the side effects |
|
|
4098 | } |
|
|
4099 | |
|
|
4100 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4101 | protecting the loop data, respectively. |
|
|
4102 | |
|
|
4103 | static void |
|
|
4104 | l_release (EV_P) |
|
|
4105 | { |
|
|
4106 | userdata *u = ev_userdata (EV_A); |
|
|
4107 | pthread_mutex_unlock (&u->lock); |
|
|
4108 | } |
|
|
4109 | |
|
|
4110 | static void |
|
|
4111 | l_acquire (EV_P) |
|
|
4112 | { |
|
|
4113 | userdata *u = ev_userdata (EV_A); |
|
|
4114 | pthread_mutex_lock (&u->lock); |
|
|
4115 | } |
|
|
4116 | |
|
|
4117 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4118 | into C<ev_loop>: |
|
|
4119 | |
|
|
4120 | void * |
|
|
4121 | l_run (void *thr_arg) |
|
|
4122 | { |
|
|
4123 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4124 | |
|
|
4125 | l_acquire (EV_A); |
|
|
4126 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4127 | ev_loop (EV_A_ 0); |
|
|
4128 | l_release (EV_A); |
|
|
4129 | |
|
|
4130 | return 0; |
|
|
4131 | } |
|
|
4132 | |
|
|
4133 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4134 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4135 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4136 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4137 | and b) skipping inter-thread-communication when there are no pending |
|
|
4138 | watchers is very beneficial): |
|
|
4139 | |
|
|
4140 | static void |
|
|
4141 | l_invoke (EV_P) |
|
|
4142 | { |
|
|
4143 | userdata *u = ev_userdata (EV_A); |
|
|
4144 | |
|
|
4145 | while (ev_pending_count (EV_A)) |
|
|
4146 | { |
|
|
4147 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4148 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4149 | } |
|
|
4150 | } |
|
|
4151 | |
|
|
4152 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4153 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4154 | thread to continue: |
|
|
4155 | |
|
|
4156 | static void |
|
|
4157 | real_invoke_pending (EV_P) |
|
|
4158 | { |
|
|
4159 | userdata *u = ev_userdata (EV_A); |
|
|
4160 | |
|
|
4161 | pthread_mutex_lock (&u->lock); |
|
|
4162 | ev_invoke_pending (EV_A); |
|
|
4163 | pthread_cond_signal (&u->invoke_cv); |
|
|
4164 | pthread_mutex_unlock (&u->lock); |
|
|
4165 | } |
|
|
4166 | |
|
|
4167 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4168 | event loop, you will now have to lock: |
|
|
4169 | |
|
|
4170 | ev_timer timeout_watcher; |
|
|
4171 | userdata *u = ev_userdata (EV_A); |
|
|
4172 | |
|
|
4173 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4174 | |
|
|
4175 | pthread_mutex_lock (&u->lock); |
|
|
4176 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4177 | ev_async_send (EV_A_ &u->async_w); |
|
|
4178 | pthread_mutex_unlock (&u->lock); |
|
|
4179 | |
|
|
4180 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4181 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4182 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4183 | watchers in the next event loop iteration. |
|
|
4184 | |
3846 | =head3 COROUTINES |
4185 | =head3 COROUTINES |
3847 | |
4186 | |
3848 | Libev is very accommodating to coroutines ("cooperative threads"): |
4187 | Libev is very accommodating to coroutines ("cooperative threads"): |
3849 | libev fully supports nesting calls to its functions from different |
4188 | libev fully supports nesting calls to its functions from different |
3850 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4189 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3851 | different coroutines, and switch freely between both coroutines running the |
4190 | different coroutines, and switch freely between both coroutines running |
3852 | loop, as long as you don't confuse yourself). The only exception is that |
4191 | the loop, as long as you don't confuse yourself). The only exception is |
3853 | you must not do this from C<ev_periodic> reschedule callbacks. |
4192 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3854 | |
4193 | |
3855 | Care has been taken to ensure that libev does not keep local state inside |
4194 | Care has been taken to ensure that libev does not keep local state inside |
3856 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4195 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3857 | they do not call any callbacks. |
4196 | they do not call any callbacks. |
3858 | |
4197 | |
… | |
… | |
4065 | =item C<double> must hold a time value in seconds with enough accuracy |
4404 | =item C<double> must hold a time value in seconds with enough accuracy |
4066 | |
4405 | |
4067 | The type C<double> is used to represent timestamps. It is required to |
4406 | The type C<double> is used to represent timestamps. It is required to |
4068 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4407 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4069 | enough for at least into the year 4000. This requirement is fulfilled by |
4408 | enough for at least into the year 4000. This requirement is fulfilled by |
4070 | implementations implementing IEEE 754 (basically all existing ones). |
4409 | implementations implementing IEEE 754, which is basically all existing |
|
|
4410 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4411 | 2200. |
4071 | |
4412 | |
4072 | =back |
4413 | =back |
4073 | |
4414 | |
4074 | If you know of other additional requirements drop me a note. |
4415 | If you know of other additional requirements drop me a note. |
4075 | |
4416 | |