| … | |
… | |
| 75 | While this document tries to be as complete as possible in documenting |
75 | While this document tries to be as complete as possible in documenting |
| 76 | libev, its usage and the rationale behind its design, it is not a tutorial |
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
| 77 | on event-based programming, nor will it introduce event-based programming |
77 | on event-based programming, nor will it introduce event-based programming |
| 78 | with libev. |
78 | with libev. |
| 79 | |
79 | |
| 80 | Familarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
| 81 | throughout this document. |
81 | throughout this document. |
| 82 | |
82 | |
| 83 | =head1 ABOUT LIBEV |
83 | =head1 ABOUT LIBEV |
| 84 | |
84 | |
| 85 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
| … | |
… | |
| 705 | C<ev_resume> directly afterwards to resume timer processing. |
705 | C<ev_resume> directly afterwards to resume timer processing. |
| 706 | |
706 | |
| 707 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
707 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
| 708 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
708 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
| 709 | will be rescheduled (that is, they will lose any events that would have |
709 | will be rescheduled (that is, they will lose any events that would have |
| 710 | occured while suspended). |
710 | occurred while suspended). |
| 711 | |
711 | |
| 712 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
712 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
| 713 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
713 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
| 714 | without a previous call to C<ev_suspend>. |
714 | without a previous call to C<ev_suspend>. |
| 715 | |
715 | |
| … | |
… | |
| 792 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
792 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
| 793 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
793 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
| 794 | |
794 | |
| 795 | This "unloop state" will be cleared when entering C<ev_loop> again. |
795 | This "unloop state" will be cleared when entering C<ev_loop> again. |
| 796 | |
796 | |
| 797 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
797 | It is safe to call C<ev_unloop> from outside any C<ev_loop> calls. |
| 798 | |
798 | |
| 799 | =item ev_ref (loop) |
799 | =item ev_ref (loop) |
| 800 | |
800 | |
| 801 | =item ev_unref (loop) |
801 | =item ev_unref (loop) |
| 802 | |
802 | |
| … | |
… | |
| 872 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
872 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
| 873 | as this approaches the timing granularity of most systems. Note that if |
873 | as this approaches the timing granularity of most systems. Note that if |
| 874 | you do transactions with the outside world and you can't increase the |
874 | you do transactions with the outside world and you can't increase the |
| 875 | parallelity, then this setting will limit your transaction rate (if you |
875 | parallelity, then this setting will limit your transaction rate (if you |
| 876 | need to poll once per transaction and the I/O collect interval is 0.01, |
876 | need to poll once per transaction and the I/O collect interval is 0.01, |
| 877 | then you can't do more than 100 transations per second). |
877 | then you can't do more than 100 transactions per second). |
| 878 | |
878 | |
| 879 | Setting the I<timeout collect interval> can improve the opportunity for |
879 | Setting the I<timeout collect interval> can improve the opportunity for |
| 880 | saving power, as the program will "bundle" timer callback invocations that |
880 | saving power, as the program will "bundle" timer callback invocations that |
| 881 | are "near" in time together, by delaying some, thus reducing the number of |
881 | are "near" in time together, by delaying some, thus reducing the number of |
| 882 | times the process sleeps and wakes up again. Another useful technique to |
882 | times the process sleeps and wakes up again. Another useful technique to |
| … | |
… | |
| 1380 | |
1380 | |
| 1381 | For example, to emulate how many other event libraries handle priorities, |
1381 | For example, to emulate how many other event libraries handle priorities, |
| 1382 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1382 | you can associate an C<ev_idle> watcher to each such watcher, and in |
| 1383 | the normal watcher callback, you just start the idle watcher. The real |
1383 | the normal watcher callback, you just start the idle watcher. The real |
| 1384 | processing is done in the idle watcher callback. This causes libev to |
1384 | processing is done in the idle watcher callback. This causes libev to |
| 1385 | continously poll and process kernel event data for the watcher, but when |
1385 | continuously poll and process kernel event data for the watcher, but when |
| 1386 | the lock-out case is known to be rare (which in turn is rare :), this is |
1386 | the lock-out case is known to be rare (which in turn is rare :), this is |
| 1387 | workable. |
1387 | workable. |
| 1388 | |
1388 | |
| 1389 | Usually, however, the lock-out model implemented that way will perform |
1389 | Usually, however, the lock-out model implemented that way will perform |
| 1390 | miserably under the type of load it was designed to handle. In that case, |
1390 | miserably under the type of load it was designed to handle. In that case, |
| … | |
… | |
| 1468 | |
1468 | |
| 1469 | If you cannot use non-blocking mode, then force the use of a |
1469 | If you cannot use non-blocking mode, then force the use of a |
| 1470 | known-to-be-good backend (at the time of this writing, this includes only |
1470 | known-to-be-good backend (at the time of this writing, this includes only |
| 1471 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
1471 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
| 1472 | descriptors for which non-blocking operation makes no sense (such as |
1472 | descriptors for which non-blocking operation makes no sense (such as |
| 1473 | files) - libev doesn't guarentee any specific behaviour in that case. |
1473 | files) - libev doesn't guarantee any specific behaviour in that case. |
| 1474 | |
1474 | |
| 1475 | Another thing you have to watch out for is that it is quite easy to |
1475 | Another thing you have to watch out for is that it is quite easy to |
| 1476 | receive "spurious" readiness notifications, that is your callback might |
1476 | receive "spurious" readiness notifications, that is your callback might |
| 1477 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1477 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
| 1478 | because there is no data. Not only are some backends known to create a |
1478 | because there is no data. Not only are some backends known to create a |
| … | |
… | |
| 1737 | ev_tstamp timeout = last_activity + 60.; |
1737 | ev_tstamp timeout = last_activity + 60.; |
| 1738 | |
1738 | |
| 1739 | // if last_activity + 60. is older than now, we did time out |
1739 | // if last_activity + 60. is older than now, we did time out |
| 1740 | if (timeout < now) |
1740 | if (timeout < now) |
| 1741 | { |
1741 | { |
| 1742 | // timeout occured, take action |
1742 | // timeout occurred, take action |
| 1743 | } |
1743 | } |
| 1744 | else |
1744 | else |
| 1745 | { |
1745 | { |
| 1746 | // callback was invoked, but there was some activity, re-arm |
1746 | // callback was invoked, but there was some activity, re-arm |
| 1747 | // the watcher to fire in last_activity + 60, which is |
1747 | // the watcher to fire in last_activity + 60, which is |
| … | |
… | |
| 3986 | |
3986 | |
| 3987 | The highest supported signal number, +1 (or, the number of |
3987 | The highest supported signal number, +1 (or, the number of |
| 3988 | signals): Normally, libev tries to deduce the maximum number of signals |
3988 | signals): Normally, libev tries to deduce the maximum number of signals |
| 3989 | automatically, but sometimes this fails, in which case it can be |
3989 | automatically, but sometimes this fails, in which case it can be |
| 3990 | specified. Also, using a lower number than detected (C<32> should be |
3990 | specified. Also, using a lower number than detected (C<32> should be |
| 3991 | good for about any system in existance) can save some memory, as libev |
3991 | good for about any system in existence) can save some memory, as libev |
| 3992 | statically allocates some 12-24 bytes per signal number. |
3992 | statically allocates some 12-24 bytes per signal number. |
| 3993 | |
3993 | |
| 3994 | =item EV_PID_HASHSIZE |
3994 | =item EV_PID_HASHSIZE |
| 3995 | |
3995 | |
| 3996 | C<ev_child> watchers use a small hash table to distribute workload by |
3996 | C<ev_child> watchers use a small hash table to distribute workload by |
| … | |
… | |
| 4651 | |
4651 | |
| 4652 | This is a simple rename - all other watcher types use their name |
4652 | This is a simple rename - all other watcher types use their name |
| 4653 | as revents flag, and now C<ev_timer> does, too. |
4653 | as revents flag, and now C<ev_timer> does, too. |
| 4654 | |
4654 | |
| 4655 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
4655 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
| 4656 | and continue to be present for the forseeable future, so this is mostly a |
4656 | and continue to be present for the foreseeable future, so this is mostly a |
| 4657 | documentation change. |
4657 | documentation change. |
| 4658 | |
4658 | |
| 4659 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4659 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
| 4660 | |
4660 | |
| 4661 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4661 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
