… | |
… | |
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) |
|
|
121 | |
|
|
122 | Sleep for the given interval: The current thread will be blocked until |
|
|
123 | either it is interrupted or the given time interval has passed. Basically |
|
|
124 | this is a subsecond-resolution C<sleep ()>. |
|
|
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 |
|
|
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 I<all> BSDs (usually it doesn't work with anything but |
336 | anything but sockets and pipes, except on Darwin, where of course it's |
345 | sockets and pipes, except on Darwin, where of course it's completely |
|
|
346 | useless. On NetBSD, it seems to work for all the FD types I tested, so it |
337 | completely useless). For this reason it's not being "autodetected" |
347 | is used by default there). For this reason it's not being "autodetected" |
338 | unless you explicitly specify it explicitly in the flags (i.e. using |
348 | unless you explicitly specify it explicitly in the flags (i.e. using |
339 | C<EVBACKEND_KQUEUE>). |
349 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
350 | system like NetBSD. |
340 | |
351 | |
341 | It scales in the same way as the epoll backend, but the interface to the |
352 | 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 |
353 | kernel is more efficient (which says nothing about its actual speed, |
343 | course). While starting and stopping an I/O watcher does not cause an |
354 | of course). While stopping, setting and starting an I/O watcher does |
344 | extra syscall as with epoll, it still adds up to four event changes per |
355 | never cause an extra syscall as with epoll, it still adds up to two event |
345 | incident, so its best to avoid that. |
356 | changes per incident, support for C<fork ()> is very bad and it drops fds |
|
|
357 | silently in similarly hard-to-detetc cases. |
346 | |
358 | |
347 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
359 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
348 | |
360 | |
349 | This is not implemented yet (and might never be). |
361 | This is not implemented yet (and might never be). |
350 | |
362 | |
351 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
363 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
352 | |
364 | |
353 | This uses the Solaris 10 port mechanism. As with everything on Solaris, |
365 | 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)). |
366 | it's really slow, but it still scales very well (O(active_fds)). |
355 | |
367 | |
356 | Please note that solaris ports can result in a lot of spurious |
368 | 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 |
369 | notifications, so you need to use non-blocking I/O or other means to avoid |
358 | blocking when no data (or space) is available. |
370 | blocking when no data (or space) is available. |
359 | |
371 | |
360 | =item C<EVBACKEND_ALL> |
372 | =item C<EVBACKEND_ALL> |
361 | |
373 | |
… | |
… | |
563 | Example: For some weird reason, unregister the above signal handler again. |
575 | Example: For some weird reason, unregister the above signal handler again. |
564 | |
576 | |
565 | ev_ref (loop); |
577 | ev_ref (loop); |
566 | ev_signal_stop (loop, &exitsig); |
578 | ev_signal_stop (loop, &exitsig); |
567 | |
579 | |
|
|
580 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
|
|
581 | |
|
|
582 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
|
|
583 | |
|
|
584 | These advanced functions influence the time that libev will spend waiting |
|
|
585 | for events. Both are by default C<0>, meaning that libev will try to |
|
|
586 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
|
|
587 | |
|
|
588 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
|
|
589 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
|
|
590 | increase efficiency of loop iterations. |
|
|
591 | |
|
|
592 | The background is that sometimes your program runs just fast enough to |
|
|
593 | handle one (or very few) event(s) per loop iteration. While this makes |
|
|
594 | the program responsive, it also wastes a lot of CPU time to poll for new |
|
|
595 | events, especially with backends like C<select ()> which have a high |
|
|
596 | overhead for the actual polling but can deliver many events at once. |
|
|
597 | |
|
|
598 | By setting a higher I<io collect interval> you allow libev to spend more |
|
|
599 | time collecting I/O events, so you can handle more events per iteration, |
|
|
600 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
|
|
601 | C<ev_timer>) will be not affected. |
|
|
602 | |
|
|
603 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
|
|
604 | to spend more time collecting timeouts, at the expense of increased |
|
|
605 | latency (the watcher callback will be called later). C<ev_io> watchers |
|
|
606 | will not be affected. |
|
|
607 | |
|
|
608 | Many (busy) programs can usually benefit by setting the io collect |
|
|
609 | interval to a value near C<0.1> or so, which is often enough for |
|
|
610 | interactive servers (of course not for games), likewise for timeouts. It |
|
|
611 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
|
|
612 | as this approsaches the timing granularity of most systems. |
|
|
613 | |
568 | =back |
614 | =back |
569 | |
615 | |
570 | |
616 | |
571 | =head1 ANATOMY OF A WATCHER |
617 | =head1 ANATOMY OF A WATCHER |
572 | |
618 | |
… | |
… | |
924 | such as poll (fortunately in our Xlib example, Xlib already does this on |
970 | such as poll (fortunately in our Xlib example, Xlib already does this on |
925 | its own, so its quite safe to use). |
971 | its own, so its quite safe to use). |
926 | |
972 | |
927 | =head3 The special problem of disappearing file descriptors |
973 | =head3 The special problem of disappearing file descriptors |
928 | |
974 | |
929 | Some backends (e.g kqueue, epoll) need to be told about closing a file |
975 | 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, |
976 | 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 |
977 | 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 |
978 | 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 |
979 | 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 |
980 | 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. |
988 | descriptor even if the file descriptor number itself did not change. |
943 | |
989 | |
944 | This is how one would do it normally anyway, the important point is that |
990 | 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 |
991 | the libev application should not optimise around libev but should leave |
946 | optimisations to libev. |
992 | optimisations to libev. |
|
|
993 | |
|
|
994 | =head3 The special problem of dup'ed file descriptors |
|
|
995 | |
|
|
996 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
997 | but only events for the underlying file descriptions. That menas when you |
|
|
998 | have C<dup ()>'ed file descriptors and register events for them, only one |
|
|
999 | file descriptor might actually receive events. |
|
|
1000 | |
|
|
1001 | There is no workaorund possible except not registering events |
|
|
1002 | for potentially C<dup ()>'ed file descriptors or to resort to |
|
|
1003 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
|
|
1004 | |
|
|
1005 | =head3 The special problem of fork |
|
|
1006 | |
|
|
1007 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
|
|
1008 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1009 | it in the child. |
|
|
1010 | |
|
|
1011 | To support fork in your programs, you either have to call |
|
|
1012 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
|
|
1013 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
|
|
1014 | C<EVBACKEND_POLL>. |
947 | |
1015 | |
948 | |
1016 | |
949 | =head3 Watcher-Specific Functions |
1017 | =head3 Watcher-Specific Functions |
950 | |
1018 | |
951 | =over 4 |
1019 | =over 4 |
… | |
… | |
1706 | =head2 C<ev_embed> - when one backend isn't enough... |
1774 | =head2 C<ev_embed> - when one backend isn't enough... |
1707 | |
1775 | |
1708 | This is a rather advanced watcher type that lets you embed one event loop |
1776 | This is a rather advanced watcher type that lets you embed one event loop |
1709 | into another (currently only C<ev_io> events are supported in the embedded |
1777 | into another (currently only C<ev_io> events are supported in the embedded |
1710 | loop, other types of watchers might be handled in a delayed or incorrect |
1778 | loop, other types of watchers might be handled in a delayed or incorrect |
1711 | fashion and must not be used). |
1779 | fashion and must not be used). (See portability notes, below). |
1712 | |
1780 | |
1713 | There are primarily two reasons you would want that: work around bugs and |
1781 | There are primarily two reasons you would want that: work around bugs and |
1714 | prioritise I/O. |
1782 | prioritise I/O. |
1715 | |
1783 | |
1716 | As an example for a bug workaround, the kqueue backend might only support |
1784 | As an example for a bug workaround, the kqueue backend might only support |
… | |
… | |
1771 | ev_embed_start (loop_hi, &embed); |
1839 | ev_embed_start (loop_hi, &embed); |
1772 | } |
1840 | } |
1773 | else |
1841 | else |
1774 | loop_lo = loop_hi; |
1842 | loop_lo = loop_hi; |
1775 | |
1843 | |
|
|
1844 | =head2 Portability notes |
|
|
1845 | |
|
|
1846 | Kqueue is nominally embeddable, but this is broken on all BSDs that I |
|
|
1847 | tried, in various ways. Usually the embedded event loop will simply never |
|
|
1848 | receive events, sometimes it will only trigger a few times, sometimes in a |
|
|
1849 | loop. Epoll is also nominally embeddable, but many Linux kernel versions |
|
|
1850 | will always eport the epoll fd as ready, even when no events are pending. |
|
|
1851 | |
|
|
1852 | While libev allows embedding these backends (they are contained in |
|
|
1853 | C<ev_embeddable_backends ()>), take extreme care that it will actually |
|
|
1854 | work. |
|
|
1855 | |
|
|
1856 | When in doubt, create a dynamic event loop forced to use sockets (this |
|
|
1857 | usually works) and possibly another thread and a pipe or so to report to |
|
|
1858 | your main event loop. |
|
|
1859 | |
1776 | =head3 Watcher-Specific Functions and Data Members |
1860 | =head3 Watcher-Specific Functions and Data Members |
1777 | |
1861 | |
1778 | =over 4 |
1862 | =over 4 |
1779 | |
1863 | |
1780 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
1864 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
… | |
… | |
2252 | realtime clock option at compiletime (and assume its availability at |
2336 | realtime clock option at compiletime (and assume its availability at |
2253 | runtime if successful). Otherwise no use of the realtime clock option will |
2337 | runtime if successful). Otherwise no use of the realtime clock option will |
2254 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
2338 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
2255 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
2339 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
2256 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
2340 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
|
|
2341 | |
|
|
2342 | =item EV_USE_NANOSLEEP |
|
|
2343 | |
|
|
2344 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
|
|
2345 | and will use it for delays. Otherwise it will use C<select ()>. |
2257 | |
2346 | |
2258 | =item EV_USE_SELECT |
2347 | =item EV_USE_SELECT |
2259 | |
2348 | |
2260 | If undefined or defined to be C<1>, libev will compile in support for the |
2349 | 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 |
2350 | C<select>(2) backend. No attempt at autodetection will be done: if no |
… | |
… | |
2440 | |
2529 | |
2441 | =item ev_set_cb (ev, cb) |
2530 | =item ev_set_cb (ev, cb) |
2442 | |
2531 | |
2443 | Can be used to change the callback member declaration in each watcher, |
2532 | Can be used to change the callback member declaration in each watcher, |
2444 | and the way callbacks are invoked and set. Must expand to a struct member |
2533 | and the way callbacks are invoked and set. Must expand to a struct member |
2445 | definition and a statement, respectively. See the F<ev.c> header file for |
2534 | definition and a statement, respectively. See the F<ev.h> header file for |
2446 | their default definitions. One possible use for overriding these is to |
2535 | their default definitions. One possible use for overriding these is to |
2447 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
2536 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
2448 | method calls instead of plain function calls in C++. |
2537 | method calls instead of plain function calls in C++. |
2449 | |
2538 | |
2450 | =head2 EXPORTED API SYMBOLS |
2539 | =head2 EXPORTED API SYMBOLS |