… | |
… | |
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); |
836 | |
860 | |
837 | =item ev_loop_verify (loop) |
861 | =item ev_loop_verify (loop) |
838 | |
862 | |
839 | This function only does something when C<EV_VERIFY> support has been |
863 | 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 |
864 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
1468 | |
1492 | |
1469 | The callback is guaranteed to be invoked only I<after> its timeout has |
1493 | 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 |
1494 | 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 |
1495 | 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 |
1496 | 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 |
1497 | before ones of the same priority with later time-out values (but this is |
1474 | callback calls C<ev_loop> recursively). |
1498 | no longer true when a callback calls C<ev_loop> recursively). |
1475 | |
1499 | |
1476 | =head3 Be smart about timeouts |
1500 | =head3 Be smart about timeouts |
1477 | |
1501 | |
1478 | Many real-world problems involve some kind of timeout, usually for error |
1502 | 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, |
1503 | 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> |
1547 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1524 | member and C<ev_timer_again>. |
1548 | member and C<ev_timer_again>. |
1525 | |
1549 | |
1526 | At start: |
1550 | At start: |
1527 | |
1551 | |
1528 | ev_timer_init (timer, callback); |
1552 | ev_init (timer, callback); |
1529 | timer->repeat = 60.; |
1553 | timer->repeat = 60.; |
1530 | ev_timer_again (loop, timer); |
1554 | ev_timer_again (loop, timer); |
1531 | |
1555 | |
1532 | Each time there is some activity: |
1556 | Each time there is some activity: |
1533 | |
1557 | |
… | |
… | |
1595 | |
1619 | |
1596 | To start the timer, simply initialise the watcher and set C<last_activity> |
1620 | 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 |
1621 | 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: |
1622 | callback, which will "do the right thing" and start the timer: |
1599 | |
1623 | |
1600 | ev_timer_init (timer, callback); |
1624 | ev_init (timer, callback); |
1601 | last_activity = ev_now (loop); |
1625 | last_activity = ev_now (loop); |
1602 | callback (loop, timer, EV_TIMEOUT); |
1626 | callback (loop, timer, EV_TIMEOUT); |
1603 | |
1627 | |
1604 | And when there is some activity, simply store the current time in |
1628 | And when there is some activity, simply store the current time in |
1605 | C<last_activity>, no libev calls at all: |
1629 | C<last_activity>, no libev calls at all: |
… | |
… | |
2002 | some child status changes (most typically when a child of yours dies or |
2026 | 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 |
2027 | 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 |
2028 | 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., |
2029 | 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, |
2030 | 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 |
2031 | but forking and registering a watcher a few event loop iterations later or |
2008 | not. |
2032 | in the next callback invocation is not. |
2009 | |
2033 | |
2010 | Only the default event loop is capable of handling signals, and therefore |
2034 | Only the default event loop is capable of handling signals, and therefore |
2011 | you can only register child watchers in the default event loop. |
2035 | you can only register child watchers in the default event loop. |
|
|
2036 | |
|
|
2037 | Due to some design glitches inside libev, child watchers will always be |
|
|
2038 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2039 | libev) |
2012 | |
2040 | |
2013 | =head3 Process Interaction |
2041 | =head3 Process Interaction |
2014 | |
2042 | |
2015 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2043 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2016 | initialised. This is necessary to guarantee proper behaviour even if |
2044 | initialised. This is necessary to guarantee proper behaviour even if |
… | |
… | |
2471 | struct pollfd fds [nfd]; |
2499 | struct pollfd fds [nfd]; |
2472 | // actual code will need to loop here and realloc etc. |
2500 | // actual code will need to loop here and realloc etc. |
2473 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2501 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2474 | |
2502 | |
2475 | /* the callback is illegal, but won't be called as we stop during check */ |
2503 | /* the callback is illegal, but won't be called as we stop during check */ |
2476 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2504 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2477 | ev_timer_start (loop, &tw); |
2505 | ev_timer_start (loop, &tw); |
2478 | |
2506 | |
2479 | // create one ev_io per pollfd |
2507 | // create one ev_io per pollfd |
2480 | for (int i = 0; i < nfd; ++i) |
2508 | for (int i = 0; i < nfd; ++i) |
2481 | { |
2509 | { |
… | |
… | |
3643 | defined to be C<0>, then they are not. |
3671 | defined to be C<0>, then they are not. |
3644 | |
3672 | |
3645 | =item EV_MINIMAL |
3673 | =item EV_MINIMAL |
3646 | |
3674 | |
3647 | If you need to shave off some kilobytes of code at the expense of some |
3675 | 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 |
3676 | 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 |
3677 | 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. |
3678 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3679 | the default 4-heap. |
|
|
3680 | |
|
|
3681 | You can save even more by disabling watcher types you do not need and |
|
|
3682 | setting C<EV_MAXPRI> == C<EV_MINPRI>. |
|
|
3683 | |
|
|
3684 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3685 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3686 | of the API are still available, and do not complain if this subset changes |
|
|
3687 | over time. |
3651 | |
3688 | |
3652 | =item EV_PID_HASHSIZE |
3689 | =item EV_PID_HASHSIZE |
3653 | |
3690 | |
3654 | C<ev_child> watchers use a small hash table to distribute workload by |
3691 | 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 |
3692 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
4065 | =item C<double> must hold a time value in seconds with enough accuracy |
4102 | =item C<double> must hold a time value in seconds with enough accuracy |
4066 | |
4103 | |
4067 | The type C<double> is used to represent timestamps. It is required to |
4104 | 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 |
4105 | 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 |
4106 | enough for at least into the year 4000. This requirement is fulfilled by |
4070 | implementations implementing IEEE 754 (basically all existing ones). |
4107 | implementations implementing IEEE 754, which is basically all existing |
|
|
4108 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4109 | 2200. |
4071 | |
4110 | |
4072 | =back |
4111 | =back |
4073 | |
4112 | |
4074 | If you know of other additional requirements drop me a note. |
4113 | If you know of other additional requirements drop me a note. |
4075 | |
4114 | |