… | |
… | |
620 | happily wraps around with enough iterations. |
620 | happily wraps around with enough iterations. |
621 | |
621 | |
622 | This value can sometimes be useful as a generation counter of sorts (it |
622 | 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 |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
624 | C<ev_prepare> and C<ev_check> calls. |
624 | C<ev_prepare> and C<ev_check> calls. |
|
|
625 | |
|
|
626 | =item unsigned int ev_loop_depth (loop) |
|
|
627 | |
|
|
628 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
629 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
630 | |
|
|
631 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
|
|
632 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
|
|
633 | in which case it is higher. |
|
|
634 | |
|
|
635 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
636 | etc.), doesn't count as exit. |
625 | |
637 | |
626 | =item unsigned int ev_backend (loop) |
638 | =item unsigned int ev_backend (loop) |
627 | |
639 | |
628 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
640 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
629 | use. |
641 | use. |
… | |
… | |
811 | |
823 | |
812 | By setting a higher I<io collect interval> you allow libev to spend more |
824 | 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, |
825 | 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 |
826 | 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 |
827 | 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. |
828 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
829 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
830 | once per this interval, on average. |
817 | |
831 | |
818 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
832 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
819 | to spend more time collecting timeouts, at the expense of increased |
833 | to spend more time collecting timeouts, at the expense of increased |
820 | latency/jitter/inexactness (the watcher callback will be called |
834 | 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 |
835 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
823 | |
837 | |
824 | Many (busy) programs can usually benefit by setting the I/O collect |
838 | 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 |
839 | 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 |
840 | 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>, |
841 | 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. |
842 | as this approaches the timing granularity of most systems. Note that if |
|
|
843 | you do transactions with the outside world and you can't increase the |
|
|
844 | parallelity, then this setting will limit your transaction rate (if you |
|
|
845 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
846 | then you can't do more than 100 transations per second). |
829 | |
847 | |
830 | Setting the I<timeout collect interval> can improve the opportunity for |
848 | Setting the I<timeout collect interval> can improve the opportunity for |
831 | saving power, as the program will "bundle" timer callback invocations that |
849 | 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 |
850 | 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 |
851 | 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 |
852 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
835 | they fire on, say, one-second boundaries only. |
853 | they fire on, say, one-second boundaries only. |
|
|
854 | |
|
|
855 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
856 | more often than 100 times per second: |
|
|
857 | |
|
|
858 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
859 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
860 | |
|
|
861 | =item ev_invoke_pending (loop) |
|
|
862 | |
|
|
863 | This call will simply invoke all pending watchers while resetting their |
|
|
864 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
865 | but when overriding the invoke callback this call comes handy. |
|
|
866 | |
|
|
867 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
868 | |
|
|
869 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
870 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
871 | this callback instead. This is useful, for example, when you want to |
|
|
872 | invoke the actual watchers inside another context (another thread etc.). |
|
|
873 | |
|
|
874 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
875 | callback. |
|
|
876 | |
|
|
877 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
878 | |
|
|
879 | Sometimes you want to share the same loop between multiple threads. This |
|
|
880 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
881 | each call to a libev function. |
|
|
882 | |
|
|
883 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
884 | wait for it to return. One way around this is to wake up the loop via |
|
|
885 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
886 | and I<acquire> callbacks on the loop. |
|
|
887 | |
|
|
888 | When set, then C<release> will be called just before the thread is |
|
|
889 | suspended waiting for new events, and C<acquire> is called just |
|
|
890 | afterwards. |
|
|
891 | |
|
|
892 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
893 | C<acquire> will just call the mutex_lock function again. |
|
|
894 | |
|
|
895 | While event loop modifications are allowed between invocations of |
|
|
896 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
897 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
898 | have no effect on the set of file descriptors being watched, or the time |
|
|
899 | waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
900 | to take note of any changes you made. |
|
|
901 | |
|
|
902 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
903 | invocations of C<release> and C<acquire>. |
|
|
904 | |
|
|
905 | See also the locking example in the C<THREADS> section later in this |
|
|
906 | document. |
|
|
907 | |
|
|
908 | =item ev_set_userdata (loop, void *data) |
|
|
909 | |
|
|
910 | =item ev_userdata (loop) |
|
|
911 | |
|
|
912 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
913 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
914 | C<0.> |
|
|
915 | |
|
|
916 | These two functions can be used to associate arbitrary data with a loop, |
|
|
917 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
918 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
919 | any other purpose as well. |
836 | |
920 | |
837 | =item ev_loop_verify (loop) |
921 | =item ev_loop_verify (loop) |
838 | |
922 | |
839 | This function only does something when C<EV_VERIFY> support has been |
923 | 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 |
924 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
1184 | #include <stddef.h> |
1268 | #include <stddef.h> |
1185 | |
1269 | |
1186 | static void |
1270 | static void |
1187 | t1_cb (EV_P_ ev_timer *w, int revents) |
1271 | t1_cb (EV_P_ ev_timer *w, int revents) |
1188 | { |
1272 | { |
1189 | struct my_biggy big = (struct my_biggy * |
1273 | struct my_biggy big = (struct my_biggy *) |
1190 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1274 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1191 | } |
1275 | } |
1192 | |
1276 | |
1193 | static void |
1277 | static void |
1194 | t2_cb (EV_P_ ev_timer *w, int revents) |
1278 | t2_cb (EV_P_ ev_timer *w, int revents) |
1195 | { |
1279 | { |
1196 | struct my_biggy big = (struct my_biggy * |
1280 | struct my_biggy big = (struct my_biggy *) |
1197 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1281 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1198 | } |
1282 | } |
1199 | |
1283 | |
1200 | =head2 WATCHER PRIORITY MODELS |
1284 | =head2 WATCHER PRIORITY MODELS |
1201 | |
1285 | |
… | |
… | |
1277 | // with the default priority are receiving events. |
1361 | // with the default priority are receiving events. |
1278 | ev_idle_start (EV_A_ &idle); |
1362 | ev_idle_start (EV_A_ &idle); |
1279 | } |
1363 | } |
1280 | |
1364 | |
1281 | static void |
1365 | static void |
1282 | idle-cb (EV_P_ ev_idle *w, int revents) |
1366 | idle_cb (EV_P_ ev_idle *w, int revents) |
1283 | { |
1367 | { |
1284 | // actual processing |
1368 | // actual processing |
1285 | read (STDIN_FILENO, ...); |
1369 | read (STDIN_FILENO, ...); |
1286 | |
1370 | |
1287 | // have to start the I/O watcher again, as |
1371 | // have to start the I/O watcher again, as |
… | |
… | |
1465 | year, it will still time out after (roughly) one hour. "Roughly" because |
1549 | year, it will still time out after (roughly) one hour. "Roughly" because |
1466 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1550 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1467 | monotonic clock option helps a lot here). |
1551 | monotonic clock option helps a lot here). |
1468 | |
1552 | |
1469 | The callback is guaranteed to be invoked only I<after> its timeout has |
1553 | The callback is guaranteed to be invoked only I<after> its timeout has |
1470 | passed. If multiple timers become ready during the same loop iteration |
1554 | passed (not I<at>, so on systems with very low-resolution clocks this |
1471 | then the ones with earlier time-out values are invoked before ones with |
1555 | might introduce a small delay). If multiple timers become ready during the |
1472 | later time-out values (but this is no longer true when a callback calls |
1556 | same loop iteration then the ones with earlier time-out values are invoked |
1473 | C<ev_loop> recursively). |
1557 | before ones of the same priority with later time-out values (but this is |
|
|
1558 | no longer true when a callback calls C<ev_loop> recursively). |
1474 | |
1559 | |
1475 | =head3 Be smart about timeouts |
1560 | =head3 Be smart about timeouts |
1476 | |
1561 | |
1477 | Many real-world problems involve some kind of timeout, usually for error |
1562 | Many real-world problems involve some kind of timeout, usually for error |
1478 | recovery. A typical example is an HTTP request - if the other side hangs, |
1563 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1522 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1607 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1523 | member and C<ev_timer_again>. |
1608 | member and C<ev_timer_again>. |
1524 | |
1609 | |
1525 | At start: |
1610 | At start: |
1526 | |
1611 | |
1527 | ev_timer_init (timer, callback); |
1612 | ev_init (timer, callback); |
1528 | timer->repeat = 60.; |
1613 | timer->repeat = 60.; |
1529 | ev_timer_again (loop, timer); |
1614 | ev_timer_again (loop, timer); |
1530 | |
1615 | |
1531 | Each time there is some activity: |
1616 | Each time there is some activity: |
1532 | |
1617 | |
… | |
… | |
1594 | |
1679 | |
1595 | To start the timer, simply initialise the watcher and set C<last_activity> |
1680 | To start the timer, simply initialise the watcher and set C<last_activity> |
1596 | to the current time (meaning we just have some activity :), then call the |
1681 | to the current time (meaning we just have some activity :), then call the |
1597 | callback, which will "do the right thing" and start the timer: |
1682 | callback, which will "do the right thing" and start the timer: |
1598 | |
1683 | |
1599 | ev_timer_init (timer, callback); |
1684 | ev_init (timer, callback); |
1600 | last_activity = ev_now (loop); |
1685 | last_activity = ev_now (loop); |
1601 | callback (loop, timer, EV_TIMEOUT); |
1686 | callback (loop, timer, EV_TIMEOUT); |
1602 | |
1687 | |
1603 | And when there is some activity, simply store the current time in |
1688 | And when there is some activity, simply store the current time in |
1604 | C<last_activity>, no libev calls at all: |
1689 | C<last_activity>, no libev calls at all: |
… | |
… | |
2001 | some child status changes (most typically when a child of yours dies or |
2086 | some child status changes (most typically when a child of yours dies or |
2002 | exits). It is permissible to install a child watcher I<after> the child |
2087 | exits). It is permissible to install a child watcher I<after> the child |
2003 | has been forked (which implies it might have already exited), as long |
2088 | has been forked (which implies it might have already exited), as long |
2004 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2089 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2005 | forking and then immediately registering a watcher for the child is fine, |
2090 | forking and then immediately registering a watcher for the child is fine, |
2006 | but forking and registering a watcher a few event loop iterations later is |
2091 | but forking and registering a watcher a few event loop iterations later or |
2007 | not. |
2092 | in the next callback invocation is not. |
2008 | |
2093 | |
2009 | Only the default event loop is capable of handling signals, and therefore |
2094 | Only the default event loop is capable of handling signals, and therefore |
2010 | you can only register child watchers in the default event loop. |
2095 | you can only register child watchers in the default event loop. |
|
|
2096 | |
|
|
2097 | Due to some design glitches inside libev, child watchers will always be |
|
|
2098 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2099 | libev) |
2011 | |
2100 | |
2012 | =head3 Process Interaction |
2101 | =head3 Process Interaction |
2013 | |
2102 | |
2014 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2103 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2015 | initialised. This is necessary to guarantee proper behaviour even if |
2104 | initialised. This is necessary to guarantee proper behaviour even if |
… | |
… | |
2367 | // no longer anything immediate to do. |
2456 | // no longer anything immediate to do. |
2368 | } |
2457 | } |
2369 | |
2458 | |
2370 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2459 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2371 | ev_idle_init (idle_watcher, idle_cb); |
2460 | ev_idle_init (idle_watcher, idle_cb); |
2372 | ev_idle_start (loop, idle_cb); |
2461 | ev_idle_start (loop, idle_watcher); |
2373 | |
2462 | |
2374 | |
2463 | |
2375 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2464 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2376 | |
2465 | |
2377 | Prepare and check watchers are usually (but not always) used in pairs: |
2466 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2470 | struct pollfd fds [nfd]; |
2559 | struct pollfd fds [nfd]; |
2471 | // actual code will need to loop here and realloc etc. |
2560 | // actual code will need to loop here and realloc etc. |
2472 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2561 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2473 | |
2562 | |
2474 | /* the callback is illegal, but won't be called as we stop during check */ |
2563 | /* the callback is illegal, but won't be called as we stop during check */ |
2475 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2564 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2476 | ev_timer_start (loop, &tw); |
2565 | ev_timer_start (loop, &tw); |
2477 | |
2566 | |
2478 | // create one ev_io per pollfd |
2567 | // create one ev_io per pollfd |
2479 | for (int i = 0; i < nfd; ++i) |
2568 | for (int i = 0; i < nfd; ++i) |
2480 | { |
2569 | { |
… | |
… | |
3642 | defined to be C<0>, then they are not. |
3731 | defined to be C<0>, then they are not. |
3643 | |
3732 | |
3644 | =item EV_MINIMAL |
3733 | =item EV_MINIMAL |
3645 | |
3734 | |
3646 | If you need to shave off some kilobytes of code at the expense of some |
3735 | If you need to shave off some kilobytes of code at the expense of some |
3647 | speed, define this symbol to C<1>. Currently this is used to override some |
3736 | speed (but with the full API), define this symbol to C<1>. Currently this |
3648 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3737 | is used to override some inlining decisions, saves roughly 30% code size |
3649 | much smaller 2-heap for timer management over the default 4-heap. |
3738 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3739 | the default 4-heap. |
|
|
3740 | |
|
|
3741 | You can save even more by disabling watcher types you do not need |
|
|
3742 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3743 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3744 | |
|
|
3745 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3746 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3747 | of the API are still available, and do not complain if this subset changes |
|
|
3748 | over time. |
3650 | |
3749 | |
3651 | =item EV_PID_HASHSIZE |
3750 | =item EV_PID_HASHSIZE |
3652 | |
3751 | |
3653 | C<ev_child> watchers use a small hash table to distribute workload by |
3752 | C<ev_child> watchers use a small hash table to distribute workload by |
3654 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3753 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3840 | default loop and triggering an C<ev_async> watcher from the default loop |
3939 | default loop and triggering an C<ev_async> watcher from the default loop |
3841 | watcher callback into the event loop interested in the signal. |
3940 | watcher callback into the event loop interested in the signal. |
3842 | |
3941 | |
3843 | =back |
3942 | =back |
3844 | |
3943 | |
|
|
3944 | =head4 THREAD LOCKING EXAMPLE |
|
|
3945 | |
|
|
3946 | Here is a fictitious example of how to run an event loop in a different |
|
|
3947 | thread than where callbacks are being invoked and watchers are |
|
|
3948 | created/added/removed. |
|
|
3949 | |
|
|
3950 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3951 | which uses exactly this technique (which is suited for many high-level |
|
|
3952 | languages). |
|
|
3953 | |
|
|
3954 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3955 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3956 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3957 | |
|
|
3958 | First, you need to associate some data with the event loop: |
|
|
3959 | |
|
|
3960 | typedef struct { |
|
|
3961 | mutex_t lock; /* global loop lock */ |
|
|
3962 | ev_async async_w; |
|
|
3963 | thread_t tid; |
|
|
3964 | cond_t invoke_cv; |
|
|
3965 | } userdata; |
|
|
3966 | |
|
|
3967 | void prepare_loop (EV_P) |
|
|
3968 | { |
|
|
3969 | // for simplicity, we use a static userdata struct. |
|
|
3970 | static userdata u; |
|
|
3971 | |
|
|
3972 | ev_async_init (&u->async_w, async_cb); |
|
|
3973 | ev_async_start (EV_A_ &u->async_w); |
|
|
3974 | |
|
|
3975 | pthread_mutex_init (&u->lock, 0); |
|
|
3976 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3977 | |
|
|
3978 | // now associate this with the loop |
|
|
3979 | ev_set_userdata (EV_A_ u); |
|
|
3980 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3981 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3982 | |
|
|
3983 | // then create the thread running ev_loop |
|
|
3984 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3985 | } |
|
|
3986 | |
|
|
3987 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3988 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3989 | that might have been added: |
|
|
3990 | |
|
|
3991 | static void |
|
|
3992 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3993 | { |
|
|
3994 | // just used for the side effects |
|
|
3995 | } |
|
|
3996 | |
|
|
3997 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3998 | protecting the loop data, respectively. |
|
|
3999 | |
|
|
4000 | static void |
|
|
4001 | l_release (EV_P) |
|
|
4002 | { |
|
|
4003 | userdata *u = ev_userdata (EV_A); |
|
|
4004 | pthread_mutex_unlock (&u->lock); |
|
|
4005 | } |
|
|
4006 | |
|
|
4007 | static void |
|
|
4008 | l_acquire (EV_P) |
|
|
4009 | { |
|
|
4010 | userdata *u = ev_userdata (EV_A); |
|
|
4011 | pthread_mutex_lock (&u->lock); |
|
|
4012 | } |
|
|
4013 | |
|
|
4014 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4015 | into C<ev_loop>: |
|
|
4016 | |
|
|
4017 | void * |
|
|
4018 | l_run (void *thr_arg) |
|
|
4019 | { |
|
|
4020 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4021 | |
|
|
4022 | l_acquire (EV_A); |
|
|
4023 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4024 | ev_loop (EV_A_ 0); |
|
|
4025 | l_release (EV_A); |
|
|
4026 | |
|
|
4027 | return 0; |
|
|
4028 | } |
|
|
4029 | |
|
|
4030 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4031 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4032 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4033 | have been called: |
|
|
4034 | |
|
|
4035 | static void |
|
|
4036 | l_invoke (EV_P) |
|
|
4037 | { |
|
|
4038 | userdata *u = ev_userdata (EV_A); |
|
|
4039 | |
|
|
4040 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4041 | |
|
|
4042 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4043 | } |
|
|
4044 | |
|
|
4045 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4046 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4047 | thread to continue: |
|
|
4048 | |
|
|
4049 | static void |
|
|
4050 | real_invoke_pending (EV_P) |
|
|
4051 | { |
|
|
4052 | userdata *u = ev_userdata (EV_A); |
|
|
4053 | |
|
|
4054 | pthread_mutex_lock (&u->lock); |
|
|
4055 | ev_invoke_pending (EV_A); |
|
|
4056 | pthread_cond_signal (&u->invoke_cv); |
|
|
4057 | pthread_mutex_unlock (&u->lock); |
|
|
4058 | } |
|
|
4059 | |
|
|
4060 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4061 | event loop, you will now have to lock: |
|
|
4062 | |
|
|
4063 | ev_timer timeout_watcher; |
|
|
4064 | userdata *u = ev_userdata (EV_A); |
|
|
4065 | |
|
|
4066 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4067 | |
|
|
4068 | pthread_mutex_lock (&u->lock); |
|
|
4069 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4070 | ev_async_send (EV_A_ &u->async_w); |
|
|
4071 | pthread_mutex_unlock (&u->lock); |
|
|
4072 | |
|
|
4073 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4074 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4075 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4076 | watchers in the next event loop iteration. |
|
|
4077 | |
3845 | =head3 COROUTINES |
4078 | =head3 COROUTINES |
3846 | |
4079 | |
3847 | Libev is very accommodating to coroutines ("cooperative threads"): |
4080 | Libev is very accommodating to coroutines ("cooperative threads"): |
3848 | libev fully supports nesting calls to its functions from different |
4081 | libev fully supports nesting calls to its functions from different |
3849 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4082 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3850 | different coroutines, and switch freely between both coroutines running the |
4083 | different coroutines, and switch freely between both coroutines running |
3851 | loop, as long as you don't confuse yourself). The only exception is that |
4084 | the loop, as long as you don't confuse yourself). The only exception is |
3852 | you must not do this from C<ev_periodic> reschedule callbacks. |
4085 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3853 | |
4086 | |
3854 | Care has been taken to ensure that libev does not keep local state inside |
4087 | Care has been taken to ensure that libev does not keep local state inside |
3855 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4088 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3856 | they do not call any callbacks. |
4089 | they do not call any callbacks. |
3857 | |
4090 | |
… | |
… | |
3934 | way (note also that glib is the slowest event library known to man). |
4167 | way (note also that glib is the slowest event library known to man). |
3935 | |
4168 | |
3936 | There is no supported compilation method available on windows except |
4169 | There is no supported compilation method available on windows except |
3937 | embedding it into other applications. |
4170 | embedding it into other applications. |
3938 | |
4171 | |
|
|
4172 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4173 | tries its best, but under most conditions, signals will simply not work. |
|
|
4174 | |
3939 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4175 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3940 | accept large writes: instead of resulting in a partial write, windows will |
4176 | accept large writes: instead of resulting in a partial write, windows will |
3941 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4177 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3942 | so make sure you only write small amounts into your sockets (less than a |
4178 | so make sure you only write small amounts into your sockets (less than a |
3943 | megabyte seems safe, but this apparently depends on the amount of memory |
4179 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3947 | the abysmal performance of winsockets, using a large number of sockets |
4183 | the abysmal performance of winsockets, using a large number of sockets |
3948 | is not recommended (and not reasonable). If your program needs to use |
4184 | is not recommended (and not reasonable). If your program needs to use |
3949 | more than a hundred or so sockets, then likely it needs to use a totally |
4185 | more than a hundred or so sockets, then likely it needs to use a totally |
3950 | different implementation for windows, as libev offers the POSIX readiness |
4186 | different implementation for windows, as libev offers the POSIX readiness |
3951 | notification model, which cannot be implemented efficiently on windows |
4187 | notification model, which cannot be implemented efficiently on windows |
3952 | (Microsoft monopoly games). |
4188 | (due to Microsoft monopoly games). |
3953 | |
4189 | |
3954 | A typical way to use libev under windows is to embed it (see the embedding |
4190 | A typical way to use libev under windows is to embed it (see the embedding |
3955 | section for details) and use the following F<evwrap.h> header file instead |
4191 | section for details) and use the following F<evwrap.h> header file instead |
3956 | of F<ev.h>: |
4192 | of F<ev.h>: |
3957 | |
4193 | |
… | |
… | |
3993 | |
4229 | |
3994 | Early versions of winsocket's select only supported waiting for a maximum |
4230 | Early versions of winsocket's select only supported waiting for a maximum |
3995 | of C<64> handles (probably owning to the fact that all windows kernels |
4231 | of C<64> handles (probably owning to the fact that all windows kernels |
3996 | can only wait for C<64> things at the same time internally; Microsoft |
4232 | can only wait for C<64> things at the same time internally; Microsoft |
3997 | recommends spawning a chain of threads and wait for 63 handles and the |
4233 | recommends spawning a chain of threads and wait for 63 handles and the |
3998 | previous thread in each. Great). |
4234 | previous thread in each. Sounds great!). |
3999 | |
4235 | |
4000 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4236 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4001 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4237 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4002 | call (which might be in libev or elsewhere, for example, perl does its own |
4238 | call (which might be in libev or elsewhere, for example, perl and many |
4003 | select emulation on windows). |
4239 | other interpreters do their own select emulation on windows). |
4004 | |
4240 | |
4005 | Another limit is the number of file descriptors in the Microsoft runtime |
4241 | Another limit is the number of file descriptors in the Microsoft runtime |
4006 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4242 | libraries, which by default is C<64> (there must be a hidden I<64> |
4007 | or something like this inside Microsoft). You can increase this by calling |
4243 | fetish or something like this inside Microsoft). You can increase this |
4008 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4244 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
4009 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4245 | (another arbitrary limit), but is broken in many versions of the Microsoft |
4010 | libraries. |
|
|
4011 | |
|
|
4012 | This might get you to about C<512> or C<2048> sockets (depending on |
4246 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4013 | windows version and/or the phase of the moon). To get more, you need to |
4247 | (depending on windows version and/or the phase of the moon). To get more, |
4014 | wrap all I/O functions and provide your own fd management, but the cost of |
4248 | you need to wrap all I/O functions and provide your own fd management, but |
4015 | calling select (O(n²)) will likely make this unworkable. |
4249 | the cost of calling select (O(n²)) will likely make this unworkable. |
4016 | |
4250 | |
4017 | =back |
4251 | =back |
4018 | |
4252 | |
4019 | =head2 PORTABILITY REQUIREMENTS |
4253 | =head2 PORTABILITY REQUIREMENTS |
4020 | |
4254 | |
… | |
… | |
4063 | =item C<double> must hold a time value in seconds with enough accuracy |
4297 | =item C<double> must hold a time value in seconds with enough accuracy |
4064 | |
4298 | |
4065 | The type C<double> is used to represent timestamps. It is required to |
4299 | The type C<double> is used to represent timestamps. It is required to |
4066 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4300 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4067 | enough for at least into the year 4000. This requirement is fulfilled by |
4301 | enough for at least into the year 4000. This requirement is fulfilled by |
4068 | implementations implementing IEEE 754 (basically all existing ones). |
4302 | implementations implementing IEEE 754, which is basically all existing |
|
|
4303 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4304 | 2200. |
4069 | |
4305 | |
4070 | =back |
4306 | =back |
4071 | |
4307 | |
4072 | If you know of other additional requirements drop me a note. |
4308 | If you know of other additional requirements drop me a note. |
4073 | |
4309 | |