… | |
… | |
115 | |
115 | |
116 | Returns the current time as libev would use it. Please note that the |
116 | Returns the current time as libev would use it. Please note that the |
117 | C<ev_now> function is usually faster and also often returns the timestamp |
117 | C<ev_now> function is usually faster and also often returns the timestamp |
118 | you actually want to know. |
118 | you actually want to know. |
119 | |
119 | |
|
|
120 | =item ev_sleep (ev_tstamp interval) |
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|
121 | |
|
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122 | Sleep for the given interval: The current thread will be blocked until |
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123 | either it is interrupted or the given time interval has passed. Basically |
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124 | this is a subsecond-resolution C<sleep ()>. |
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|
125 | |
120 | =item int ev_version_major () |
126 | =item int ev_version_major () |
121 | |
127 | |
122 | =item int ev_version_minor () |
128 | =item int ev_version_minor () |
123 | |
129 | |
124 | You can find out the major and minor ABI version numbers of the library |
130 | You can find out the major and minor ABI version numbers of the library |
… | |
… | |
313 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
319 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
314 | |
320 | |
315 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
321 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
316 | |
322 | |
317 | For few fds, this backend is a bit little slower than poll and select, |
323 | For few fds, this backend is a bit little slower than poll and select, |
318 | but it scales phenomenally better. While poll and select usually scale like |
324 | but it scales phenomenally better. While poll and select usually scale |
319 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
325 | like O(total_fds) where n is the total number of fds (or the highest fd), |
320 | either O(1) or O(active_fds). |
326 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
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|
327 | of shortcomings, such as silently dropping events in some hard-to-detect |
|
|
328 | cases and rewiring a syscall per fd change, no fork support and bad |
|
|
329 | support for dup: |
321 | |
330 | |
322 | While stopping and starting an I/O watcher in the same iteration will |
331 | While stopping, setting and starting an I/O watcher in the same iteration |
323 | result in some caching, there is still a syscall per such incident |
332 | will result in some caching, there is still a syscall per such incident |
324 | (because the fd could point to a different file description now), so its |
333 | (because the fd could point to a different file description now), so its |
325 | best to avoid that. Also, dup()ed file descriptors might not work very |
334 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
326 | well if you register events for both fds. |
335 | very well if you register events for both fds. |
327 | |
336 | |
328 | Please note that epoll sometimes generates spurious notifications, so you |
337 | Please note that epoll sometimes generates spurious notifications, so you |
329 | need to use non-blocking I/O or other means to avoid blocking when no data |
338 | need to use non-blocking I/O or other means to avoid blocking when no data |
330 | (or space) is available. |
339 | (or space) is available. |
331 | |
340 | |
332 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
341 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
333 | |
342 | |
334 | Kqueue deserves special mention, as at the time of this writing, it |
343 | Kqueue deserves special mention, as at the time of this writing, it |
335 | was broken on all BSDs except NetBSD (usually it doesn't work with |
344 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
336 | anything but sockets and pipes, except on Darwin, where of course it's |
345 | with anything but sockets and pipes, except on Darwin, where of course |
337 | completely useless). For this reason it's not being "autodetected" |
346 | it's completely useless). For this reason it's not being "autodetected" |
338 | unless you explicitly specify it explicitly in the flags (i.e. using |
347 | unless you explicitly specify it explicitly in the flags (i.e. using |
339 | C<EVBACKEND_KQUEUE>). |
348 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
349 | system like NetBSD. |
|
|
350 | |
|
|
351 | You still can embed kqueue into a normal poll or select backend and use it |
|
|
352 | only for sockets (after having made sure that sockets work with kqueue on |
|
|
353 | the target platform). See C<ev_embed> watchers for more info. |
340 | |
354 | |
341 | It scales in the same way as the epoll backend, but the interface to the |
355 | It scales in the same way as the epoll backend, but the interface to the |
342 | kernel is more efficient (which says nothing about its actual speed, of |
356 | kernel is more efficient (which says nothing about its actual speed, of |
343 | course). While starting and stopping an I/O watcher does not cause an |
357 | course). While stopping, setting and starting an I/O watcher does never |
344 | extra syscall as with epoll, it still adds up to four event changes per |
358 | cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to |
345 | incident, so its best to avoid that. |
359 | two event changes per incident, support for C<fork ()> is very bad and it |
|
|
360 | drops fds silently in similarly hard-to-detect cases. |
346 | |
361 | |
347 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
362 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
348 | |
363 | |
349 | This is not implemented yet (and might never be). |
364 | This is not implemented yet (and might never be). |
350 | |
365 | |
351 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
366 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
352 | |
367 | |
353 | This uses the Solaris 10 port mechanism. As with everything on Solaris, |
368 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
354 | it's really slow, but it still scales very well (O(active_fds)). |
369 | it's really slow, but it still scales very well (O(active_fds)). |
355 | |
370 | |
356 | Please note that solaris ports can result in a lot of spurious |
371 | Please note that solaris event ports can deliver a lot of spurious |
357 | notifications, so you need to use non-blocking I/O or other means to avoid |
372 | notifications, so you need to use non-blocking I/O or other means to avoid |
358 | blocking when no data (or space) is available. |
373 | blocking when no data (or space) is available. |
359 | |
374 | |
360 | =item C<EVBACKEND_ALL> |
375 | =item C<EVBACKEND_ALL> |
361 | |
376 | |
… | |
… | |
563 | Example: For some weird reason, unregister the above signal handler again. |
578 | Example: For some weird reason, unregister the above signal handler again. |
564 | |
579 | |
565 | ev_ref (loop); |
580 | ev_ref (loop); |
566 | ev_signal_stop (loop, &exitsig); |
581 | ev_signal_stop (loop, &exitsig); |
567 | |
582 | |
|
|
583 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
|
|
584 | |
|
|
585 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
|
|
586 | |
|
|
587 | These advanced functions influence the time that libev will spend waiting |
|
|
588 | for events. Both are by default C<0>, meaning that libev will try to |
|
|
589 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
|
|
590 | |
|
|
591 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
|
|
592 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
|
|
593 | increase efficiency of loop iterations. |
|
|
594 | |
|
|
595 | The background is that sometimes your program runs just fast enough to |
|
|
596 | handle one (or very few) event(s) per loop iteration. While this makes |
|
|
597 | the program responsive, it also wastes a lot of CPU time to poll for new |
|
|
598 | events, especially with backends like C<select ()> which have a high |
|
|
599 | overhead for the actual polling but can deliver many events at once. |
|
|
600 | |
|
|
601 | By setting a higher I<io collect interval> you allow libev to spend more |
|
|
602 | time collecting I/O events, so you can handle more events per iteration, |
|
|
603 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
|
|
604 | C<ev_timer>) will be not affected. Setting this to a non-null bvalue will |
|
|
605 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
|
|
606 | |
|
|
607 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
|
|
608 | to spend more time collecting timeouts, at the expense of increased |
|
|
609 | latency (the watcher callback will be called later). C<ev_io> watchers |
|
|
610 | will not be affected. Setting this to a non-null value will not introduce |
|
|
611 | any overhead in libev. |
|
|
612 | |
|
|
613 | Many (busy) programs can usually benefit by setting the io collect |
|
|
614 | interval to a value near C<0.1> or so, which is often enough for |
|
|
615 | interactive servers (of course not for games), likewise for timeouts. It |
|
|
616 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
|
|
617 | as this approsaches the timing granularity of most systems. |
|
|
618 | |
568 | =back |
619 | =back |
569 | |
620 | |
570 | |
621 | |
571 | =head1 ANATOMY OF A WATCHER |
622 | =head1 ANATOMY OF A WATCHER |
572 | |
623 | |
… | |
… | |
924 | such as poll (fortunately in our Xlib example, Xlib already does this on |
975 | such as poll (fortunately in our Xlib example, Xlib already does this on |
925 | its own, so its quite safe to use). |
976 | its own, so its quite safe to use). |
926 | |
977 | |
927 | =head3 The special problem of disappearing file descriptors |
978 | =head3 The special problem of disappearing file descriptors |
928 | |
979 | |
929 | Some backends (e.g kqueue, epoll) need to be told about closing a file |
980 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
930 | descriptor (either by calling C<close> explicitly or by any other means, |
981 | descriptor (either by calling C<close> explicitly or by any other means, |
931 | such as C<dup>). The reason is that you register interest in some file |
982 | such as C<dup>). The reason is that you register interest in some file |
932 | descriptor, but when it goes away, the operating system will silently drop |
983 | descriptor, but when it goes away, the operating system will silently drop |
933 | this interest. If another file descriptor with the same number then is |
984 | this interest. If another file descriptor with the same number then is |
934 | registered with libev, there is no efficient way to see that this is, in |
985 | registered with libev, there is no efficient way to see that this is, in |
… | |
… | |
942 | descriptor even if the file descriptor number itself did not change. |
993 | descriptor even if the file descriptor number itself did not change. |
943 | |
994 | |
944 | This is how one would do it normally anyway, the important point is that |
995 | This is how one would do it normally anyway, the important point is that |
945 | the libev application should not optimise around libev but should leave |
996 | the libev application should not optimise around libev but should leave |
946 | optimisations to libev. |
997 | optimisations to libev. |
|
|
998 | |
|
|
999 | =head3 The special problem of dup'ed file descriptors |
|
|
1000 | |
|
|
1001 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1002 | but only events for the underlying file descriptions. That menas when you |
|
|
1003 | have C<dup ()>'ed file descriptors and register events for them, only one |
|
|
1004 | file descriptor might actually receive events. |
|
|
1005 | |
|
|
1006 | There is no workaorund possible except not registering events |
|
|
1007 | for potentially C<dup ()>'ed file descriptors or to resort to |
|
|
1008 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
|
|
1009 | |
|
|
1010 | =head3 The special problem of fork |
|
|
1011 | |
|
|
1012 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
|
|
1013 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1014 | it in the child. |
|
|
1015 | |
|
|
1016 | To support fork in your programs, you either have to call |
|
|
1017 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
|
|
1018 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
|
|
1019 | C<EVBACKEND_POLL>. |
947 | |
1020 | |
948 | |
1021 | |
949 | =head3 Watcher-Specific Functions |
1022 | =head3 Watcher-Specific Functions |
950 | |
1023 | |
951 | =over 4 |
1024 | =over 4 |
… | |
… | |
1553 | |
1626 | |
1554 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1627 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1555 | priority, to ensure that they are being run before any other watchers |
1628 | priority, to ensure that they are being run before any other watchers |
1556 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1629 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1557 | too) should not activate ("feed") events into libev. While libev fully |
1630 | too) should not activate ("feed") events into libev. While libev fully |
1558 | supports this, they will be called before other C<ev_check> watchers did |
1631 | supports this, they will be called before other C<ev_check> watchers |
1559 | their job. As C<ev_check> watchers are often used to embed other event |
1632 | did their job. As C<ev_check> watchers are often used to embed other |
1560 | loops those other event loops might be in an unusable state until their |
1633 | (non-libev) event loops those other event loops might be in an unusable |
1561 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1634 | state until their C<ev_check> watcher ran (always remind yourself to |
1562 | others). |
1635 | coexist peacefully with others). |
1563 | |
1636 | |
1564 | =head3 Watcher-Specific Functions and Data Members |
1637 | =head3 Watcher-Specific Functions and Data Members |
1565 | |
1638 | |
1566 | =over 4 |
1639 | =over 4 |
1567 | |
1640 | |
… | |
… | |
2253 | runtime if successful). Otherwise no use of the realtime clock option will |
2326 | runtime if successful). Otherwise no use of the realtime clock option will |
2254 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
2327 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
2255 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
2328 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
2256 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
2329 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
2257 | |
2330 | |
|
|
2331 | =item EV_USE_NANOSLEEP |
|
|
2332 | |
|
|
2333 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
|
|
2334 | and will use it for delays. Otherwise it will use C<select ()>. |
|
|
2335 | |
2258 | =item EV_USE_SELECT |
2336 | =item EV_USE_SELECT |
2259 | |
2337 | |
2260 | If undefined or defined to be C<1>, libev will compile in support for the |
2338 | If undefined or defined to be C<1>, libev will compile in support for the |
2261 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2339 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2262 | other method takes over, select will be it. Otherwise the select backend |
2340 | other method takes over, select will be it. Otherwise the select backend |