… | |
… | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
|
|
14 | #include <stdio.h> // for puts |
|
|
15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
… | |
… | |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // unloop was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
|
|
68 | |
|
|
69 | This document documents the libev software package. |
66 | |
70 | |
67 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
|
|
74 | |
|
|
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 |
|
|
77 | on event-based programming, nor will it introduce event-based programming |
|
|
78 | with libev. |
|
|
79 | |
|
|
80 | Familarity with event based programming techniques in general is assumed |
|
|
81 | throughout this document. |
|
|
82 | |
|
|
83 | =head1 ABOUT LIBEV |
70 | |
84 | |
71 | 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 |
72 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
74 | |
88 | |
… | |
… | |
108 | name C<loop> (which is always of type C<ev_loop *>) will not have |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
109 | this argument. |
123 | this argument. |
110 | |
124 | |
111 | =head2 TIME REPRESENTATION |
125 | =head2 TIME REPRESENTATION |
112 | |
126 | |
113 | Libev represents time as a single floating point number, representing the |
127 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
129 | near the beginning of 1970, details are complicated, don't ask). This |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
130 | type is called C<ev_tstamp>, which is what you should use too. It usually |
117 | to the C<double> type in C, and when you need to do any calculations on |
131 | aliases to the C<double> type in C. When you need to do any calculations |
118 | it, you should treat it as some floating point value. Unlike the name |
132 | on it, you should treat it as some floating point value. Unlike the name |
119 | component C<stamp> might indicate, it is also used for time differences |
133 | component C<stamp> might indicate, it is also used for time differences |
120 | throughout libev. |
134 | throughout libev. |
121 | |
135 | |
122 | =head1 ERROR HANDLING |
136 | =head1 ERROR HANDLING |
123 | |
137 | |
… | |
… | |
276 | |
290 | |
277 | =back |
291 | =back |
278 | |
292 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
293 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
294 | |
281 | An event loop is described by a C<ev_loop *>. The library knows two |
295 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
282 | types of such loops, the I<default> loop, which supports signals and child |
296 | is I<not> optional in this case, as there is also an C<ev_loop> |
283 | events, and dynamically created loops which do not. |
297 | I<function>). |
|
|
298 | |
|
|
299 | The library knows two types of such loops, the I<default> loop, which |
|
|
300 | supports signals and child events, and dynamically created loops which do |
|
|
301 | not. |
284 | |
302 | |
285 | =over 4 |
303 | =over 4 |
286 | |
304 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
305 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
306 | |
… | |
… | |
294 | If you don't know what event loop to use, use the one returned from this |
312 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
313 | function. |
296 | |
314 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
315 | Note that this function is I<not> thread-safe, so if you want to use it |
298 | from multiple threads, you have to lock (note also that this is unlikely, |
316 | from multiple threads, you have to lock (note also that this is unlikely, |
299 | as loops cannot bes hared easily between threads anyway). |
317 | as loops cannot be shared easily between threads anyway). |
300 | |
318 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
319 | The default loop is the only loop that can handle C<ev_signal> and |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
320 | C<ev_child> watchers, and to do this, it always registers a handler |
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
321 | for C<SIGCHLD>. If this is a problem for your application you can either |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
322 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
398 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
381 | |
399 | |
382 | For few fds, this backend is a bit little slower than poll and select, |
400 | For few fds, this backend is a bit little slower than poll and select, |
383 | but it scales phenomenally better. While poll and select usually scale |
401 | but it scales phenomenally better. While poll and select usually scale |
384 | like O(total_fds) where n is the total number of fds (or the highest fd), |
402 | like O(total_fds) where n is the total number of fds (or the highest fd), |
385 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
403 | epoll scales either O(1) or O(active_fds). |
386 | of shortcomings, such as silently dropping events in some hard-to-detect |
404 | |
387 | cases and requiring a system call per fd change, no fork support and bad |
405 | The epoll mechanism deserves honorable mention as the most misdesigned |
388 | support for dup. |
406 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
407 | dropping file descriptors, requiring a system call per change per file |
|
|
408 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
409 | so on. The biggest issue is fork races, however - if a program forks then |
|
|
410 | I<both> parent and child process have to recreate the epoll set, which can |
|
|
411 | take considerable time (one syscall per file descriptor) and is of course |
|
|
412 | hard to detect. |
|
|
413 | |
|
|
414 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
415 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
416 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
417 | even remove them from the set) than registered in the set (especially |
|
|
418 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
419 | employing an additional generation counter and comparing that against the |
|
|
420 | events to filter out spurious ones, recreating the set when required. |
389 | |
421 | |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
422 | While stopping, setting and starting an I/O watcher in the same iteration |
391 | will result in some caching, there is still a system call per such incident |
423 | will result in some caching, there is still a system call per such |
392 | (because the fd could point to a different file description now), so its |
424 | incident (because the same I<file descriptor> could point to a different |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
425 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
394 | very well if you register events for both fds. |
426 | file descriptors might not work very well if you register events for both |
395 | |
427 | file descriptors. |
396 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
397 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
398 | (or space) is available. |
|
|
399 | |
428 | |
400 | Best performance from this backend is achieved by not unregistering all |
429 | Best performance from this backend is achieved by not unregistering all |
401 | watchers for a file descriptor until it has been closed, if possible, |
430 | watchers for a file descriptor until it has been closed, if possible, |
402 | i.e. keep at least one watcher active per fd at all times. Stopping and |
431 | i.e. keep at least one watcher active per fd at all times. Stopping and |
403 | starting a watcher (without re-setting it) also usually doesn't cause |
432 | starting a watcher (without re-setting it) also usually doesn't cause |
404 | extra overhead. |
433 | extra overhead. A fork can both result in spurious notifications as well |
|
|
434 | as in libev having to destroy and recreate the epoll object, which can |
|
|
435 | take considerable time and thus should be avoided. |
|
|
436 | |
|
|
437 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
438 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
439 | the usage. So sad. |
405 | |
440 | |
406 | While nominally embeddable in other event loops, this feature is broken in |
441 | While nominally embeddable in other event loops, this feature is broken in |
407 | all kernel versions tested so far. |
442 | all kernel versions tested so far. |
408 | |
443 | |
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
444 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
410 | C<EVBACKEND_POLL>. |
445 | C<EVBACKEND_POLL>. |
411 | |
446 | |
412 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
447 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
413 | |
448 | |
414 | Kqueue deserves special mention, as at the time of this writing, it was |
449 | Kqueue deserves special mention, as at the time of this writing, it |
415 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
450 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
416 | anything but sockets and pipes, except on Darwin, where of course it's |
451 | with anything but sockets and pipes, except on Darwin, where of course |
417 | completely useless). For this reason it's not being "auto-detected" unless |
452 | it's completely useless). Unlike epoll, however, whose brokenness |
418 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
453 | is by design, these kqueue bugs can (and eventually will) be fixed |
419 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
454 | without API changes to existing programs. For this reason it's not being |
|
|
455 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
|
|
456 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
457 | system like NetBSD. |
420 | |
458 | |
421 | You still can embed kqueue into a normal poll or select backend and use it |
459 | You still can embed kqueue into a normal poll or select backend and use it |
422 | only for sockets (after having made sure that sockets work with kqueue on |
460 | only for sockets (after having made sure that sockets work with kqueue on |
423 | the target platform). See C<ev_embed> watchers for more info. |
461 | the target platform). See C<ev_embed> watchers for more info. |
424 | |
462 | |
425 | It scales in the same way as the epoll backend, but the interface to the |
463 | It scales in the same way as the epoll backend, but the interface to the |
426 | kernel is more efficient (which says nothing about its actual speed, of |
464 | kernel is more efficient (which says nothing about its actual speed, of |
427 | course). While stopping, setting and starting an I/O watcher does never |
465 | course). While stopping, setting and starting an I/O watcher does never |
428 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
466 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
429 | two event changes per incident. Support for C<fork ()> is very bad and it |
467 | two event changes per incident. Support for C<fork ()> is very bad (but |
430 | drops fds silently in similarly hard-to-detect cases. |
468 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
469 | cases |
431 | |
470 | |
432 | This backend usually performs well under most conditions. |
471 | This backend usually performs well under most conditions. |
433 | |
472 | |
434 | While nominally embeddable in other event loops, this doesn't work |
473 | While nominally embeddable in other event loops, this doesn't work |
435 | everywhere, so you might need to test for this. And since it is broken |
474 | everywhere, so you might need to test for this. And since it is broken |
436 | almost everywhere, you should only use it when you have a lot of sockets |
475 | almost everywhere, you should only use it when you have a lot of sockets |
437 | (for which it usually works), by embedding it into another event loop |
476 | (for which it usually works), by embedding it into another event loop |
438 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
477 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
439 | using it only for sockets. |
478 | also broken on OS X)) and, did I mention it, using it only for sockets. |
440 | |
479 | |
441 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
480 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
442 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
481 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
443 | C<NOTE_EOF>. |
482 | C<NOTE_EOF>. |
444 | |
483 | |
… | |
… | |
464 | might perform better. |
503 | might perform better. |
465 | |
504 | |
466 | On the positive side, with the exception of the spurious readiness |
505 | On the positive side, with the exception of the spurious readiness |
467 | notifications, this backend actually performed fully to specification |
506 | notifications, this backend actually performed fully to specification |
468 | in all tests and is fully embeddable, which is a rare feat among the |
507 | in all tests and is fully embeddable, which is a rare feat among the |
469 | OS-specific backends. |
508 | OS-specific backends (I vastly prefer correctness over speed hacks). |
470 | |
509 | |
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
510 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
472 | C<EVBACKEND_POLL>. |
511 | C<EVBACKEND_POLL>. |
473 | |
512 | |
474 | =item C<EVBACKEND_ALL> |
513 | =item C<EVBACKEND_ALL> |
… | |
… | |
527 | responsibility to either stop all watchers cleanly yourself I<before> |
566 | responsibility to either stop all watchers cleanly yourself I<before> |
528 | calling this function, or cope with the fact afterwards (which is usually |
567 | calling this function, or cope with the fact afterwards (which is usually |
529 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
568 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
530 | for example). |
569 | for example). |
531 | |
570 | |
532 | Note that certain global state, such as signal state, will not be freed by |
571 | Note that certain global state, such as signal state (and installed signal |
533 | this function, and related watchers (such as signal and child watchers) |
572 | handlers), will not be freed by this function, and related watchers (such |
534 | would need to be stopped manually. |
573 | as signal and child watchers) would need to be stopped manually. |
535 | |
574 | |
536 | In general it is not advisable to call this function except in the |
575 | In general it is not advisable to call this function except in the |
537 | rare occasion where you really need to free e.g. the signal handling |
576 | rare occasion where you really need to free e.g. the signal handling |
538 | pipe fds. If you need dynamically allocated loops it is better to use |
577 | pipe fds. If you need dynamically allocated loops it is better to use |
539 | C<ev_loop_new> and C<ev_loop_destroy>). |
578 | C<ev_loop_new> and C<ev_loop_destroy>). |
… | |
… | |
582 | |
621 | |
583 | 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 |
584 | "ticks" the number of loop iterations), as it roughly corresponds with |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
585 | C<ev_prepare> and C<ev_check> calls. |
624 | C<ev_prepare> and C<ev_check> calls. |
586 | |
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. |
|
|
637 | |
587 | =item unsigned int ev_backend (loop) |
638 | =item unsigned int ev_backend (loop) |
588 | |
639 | |
589 | 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 |
590 | use. |
641 | use. |
591 | |
642 | |
… | |
… | |
605 | |
656 | |
606 | This function is rarely useful, but when some event callback runs for a |
657 | This function is rarely useful, but when some event callback runs for a |
607 | very long time without entering the event loop, updating libev's idea of |
658 | very long time without entering the event loop, updating libev's idea of |
608 | the current time is a good idea. |
659 | the current time is a good idea. |
609 | |
660 | |
610 | See also "The special problem of time updates" in the C<ev_timer> section. |
661 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
662 | |
|
|
663 | =item ev_suspend (loop) |
|
|
664 | |
|
|
665 | =item ev_resume (loop) |
|
|
666 | |
|
|
667 | These two functions suspend and resume a loop, for use when the loop is |
|
|
668 | not used for a while and timeouts should not be processed. |
|
|
669 | |
|
|
670 | A typical use case would be an interactive program such as a game: When |
|
|
671 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
672 | would be best to handle timeouts as if no time had actually passed while |
|
|
673 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
674 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
675 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
676 | |
|
|
677 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
678 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
679 | will be rescheduled (that is, they will lose any events that would have |
|
|
680 | occured while suspended). |
|
|
681 | |
|
|
682 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
683 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
684 | without a previous call to C<ev_suspend>. |
|
|
685 | |
|
|
686 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
687 | event loop time (see C<ev_now_update>). |
611 | |
688 | |
612 | =item ev_loop (loop, int flags) |
689 | =item ev_loop (loop, int flags) |
613 | |
690 | |
614 | Finally, this is it, the event handler. This function usually is called |
691 | Finally, this is it, the event handler. This function usually is called |
615 | after you initialised all your watchers and you want to start handling |
692 | after you initialised all your watchers and you want to start handling |
… | |
… | |
631 | the loop. |
708 | the loop. |
632 | |
709 | |
633 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
710 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
634 | necessary) and will handle those and any already outstanding ones. It |
711 | necessary) and will handle those and any already outstanding ones. It |
635 | will block your process until at least one new event arrives (which could |
712 | will block your process until at least one new event arrives (which could |
636 | be an event internal to libev itself, so there is no guarentee that a |
713 | be an event internal to libev itself, so there is no guarantee that a |
637 | user-registered callback will be called), and will return after one |
714 | user-registered callback will be called), and will return after one |
638 | iteration of the loop. |
715 | iteration of the loop. |
639 | |
716 | |
640 | This is useful if you are waiting for some external event in conjunction |
717 | This is useful if you are waiting for some external event in conjunction |
641 | with something not expressible using other libev watchers (i.e. "roll your |
718 | with something not expressible using other libev watchers (i.e. "roll your |
… | |
… | |
699 | |
776 | |
700 | If you have a watcher you never unregister that should not keep C<ev_loop> |
777 | If you have a watcher you never unregister that should not keep C<ev_loop> |
701 | from returning, call ev_unref() after starting, and ev_ref() before |
778 | from returning, call ev_unref() after starting, and ev_ref() before |
702 | stopping it. |
779 | stopping it. |
703 | |
780 | |
704 | As an example, libev itself uses this for its internal signal pipe: It is |
781 | As an example, libev itself uses this for its internal signal pipe: It |
705 | not visible to the libev user and should not keep C<ev_loop> from exiting |
782 | is not visible to the libev user and should not keep C<ev_loop> from |
706 | if no event watchers registered by it are active. It is also an excellent |
783 | exiting if no event watchers registered by it are active. It is also an |
707 | way to do this for generic recurring timers or from within third-party |
784 | excellent way to do this for generic recurring timers or from within |
708 | libraries. Just remember to I<unref after start> and I<ref before stop> |
785 | third-party libraries. Just remember to I<unref after start> and I<ref |
709 | (but only if the watcher wasn't active before, or was active before, |
786 | before stop> (but only if the watcher wasn't active before, or was active |
710 | respectively). |
787 | before, respectively. Note also that libev might stop watchers itself |
|
|
788 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
789 | in the callback). |
711 | |
790 | |
712 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
791 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
713 | running when nothing else is active. |
792 | running when nothing else is active. |
714 | |
793 | |
715 | ev_signal exitsig; |
794 | ev_signal exitsig; |
… | |
… | |
744 | |
823 | |
745 | 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 |
746 | 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, |
747 | 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 |
748 | 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 |
749 | 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. |
750 | |
831 | |
751 | 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 |
752 | to spend more time collecting timeouts, at the expense of increased |
833 | to spend more time collecting timeouts, at the expense of increased |
753 | latency/jitter/inexactness (the watcher callback will be called |
834 | latency/jitter/inexactness (the watcher callback will be called |
754 | 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 |
… | |
… | |
756 | |
837 | |
757 | 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 |
758 | 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 |
759 | interactive servers (of course not for games), likewise for timeouts. It |
840 | interactive servers (of course not for games), likewise for timeouts. It |
760 | 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>, |
761 | 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). |
762 | |
847 | |
763 | Setting the I<timeout collect interval> can improve the opportunity for |
848 | Setting the I<timeout collect interval> can improve the opportunity for |
764 | saving power, as the program will "bundle" timer callback invocations that |
849 | saving power, as the program will "bundle" timer callback invocations that |
765 | 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 |
766 | 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 |
767 | 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 |
768 | they fire on, say, one-second boundaries only. |
853 | they fire on, say, one-second boundaries only. |
769 | |
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 int ev_pending_count (loop) |
|
|
868 | |
|
|
869 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
870 | are pending. |
|
|
871 | |
|
|
872 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
873 | |
|
|
874 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
875 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
876 | this callback instead. This is useful, for example, when you want to |
|
|
877 | invoke the actual watchers inside another context (another thread etc.). |
|
|
878 | |
|
|
879 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
880 | callback. |
|
|
881 | |
|
|
882 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
883 | |
|
|
884 | Sometimes you want to share the same loop between multiple threads. This |
|
|
885 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
886 | each call to a libev function. |
|
|
887 | |
|
|
888 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
889 | wait for it to return. One way around this is to wake up the loop via |
|
|
890 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
891 | and I<acquire> callbacks on the loop. |
|
|
892 | |
|
|
893 | When set, then C<release> will be called just before the thread is |
|
|
894 | suspended waiting for new events, and C<acquire> is called just |
|
|
895 | afterwards. |
|
|
896 | |
|
|
897 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
898 | C<acquire> will just call the mutex_lock function again. |
|
|
899 | |
|
|
900 | While event loop modifications are allowed between invocations of |
|
|
901 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
902 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
903 | have no effect on the set of file descriptors being watched, or the time |
|
|
904 | waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
905 | to take note of any changes you made. |
|
|
906 | |
|
|
907 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
908 | invocations of C<release> and C<acquire>. |
|
|
909 | |
|
|
910 | See also the locking example in the C<THREADS> section later in this |
|
|
911 | document. |
|
|
912 | |
|
|
913 | =item ev_set_userdata (loop, void *data) |
|
|
914 | |
|
|
915 | =item ev_userdata (loop) |
|
|
916 | |
|
|
917 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
918 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
919 | C<0.> |
|
|
920 | |
|
|
921 | These two functions can be used to associate arbitrary data with a loop, |
|
|
922 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
923 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
924 | any other purpose as well. |
|
|
925 | |
770 | =item ev_loop_verify (loop) |
926 | =item ev_loop_verify (loop) |
771 | |
927 | |
772 | This function only does something when C<EV_VERIFY> support has been |
928 | This function only does something when C<EV_VERIFY> support has been |
773 | compiled in. which is the default for non-minimal builds. It tries to go |
929 | compiled in, which is the default for non-minimal builds. It tries to go |
774 | through all internal structures and checks them for validity. If anything |
930 | through all internal structures and checks them for validity. If anything |
775 | is found to be inconsistent, it will print an error message to standard |
931 | is found to be inconsistent, it will print an error message to standard |
776 | error and call C<abort ()>. |
932 | error and call C<abort ()>. |
777 | |
933 | |
778 | This can be used to catch bugs inside libev itself: under normal |
934 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
782 | =back |
938 | =back |
783 | |
939 | |
784 | |
940 | |
785 | =head1 ANATOMY OF A WATCHER |
941 | =head1 ANATOMY OF A WATCHER |
786 | |
942 | |
|
|
943 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
944 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
945 | watchers and C<ev_io_start> for I/O watchers. |
|
|
946 | |
787 | A watcher is a structure that you create and register to record your |
947 | A watcher is a structure that you create and register to record your |
788 | interest in some event. For instance, if you want to wait for STDIN to |
948 | interest in some event. For instance, if you want to wait for STDIN to |
789 | become readable, you would create an C<ev_io> watcher for that: |
949 | become readable, you would create an C<ev_io> watcher for that: |
790 | |
950 | |
791 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
951 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
… | |
… | |
793 | ev_io_stop (w); |
953 | ev_io_stop (w); |
794 | ev_unloop (loop, EVUNLOOP_ALL); |
954 | ev_unloop (loop, EVUNLOOP_ALL); |
795 | } |
955 | } |
796 | |
956 | |
797 | struct ev_loop *loop = ev_default_loop (0); |
957 | struct ev_loop *loop = ev_default_loop (0); |
|
|
958 | |
798 | ev_io stdin_watcher; |
959 | ev_io stdin_watcher; |
|
|
960 | |
799 | ev_init (&stdin_watcher, my_cb); |
961 | ev_init (&stdin_watcher, my_cb); |
800 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
962 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
801 | ev_io_start (loop, &stdin_watcher); |
963 | ev_io_start (loop, &stdin_watcher); |
|
|
964 | |
802 | ev_loop (loop, 0); |
965 | ev_loop (loop, 0); |
803 | |
966 | |
804 | As you can see, you are responsible for allocating the memory for your |
967 | As you can see, you are responsible for allocating the memory for your |
805 | watcher structures (and it is usually a bad idea to do this on the stack, |
968 | watcher structures (and it is I<usually> a bad idea to do this on the |
806 | although this can sometimes be quite valid). |
969 | stack). |
|
|
970 | |
|
|
971 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
972 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
807 | |
973 | |
808 | Each watcher structure must be initialised by a call to C<ev_init |
974 | Each watcher structure must be initialised by a call to C<ev_init |
809 | (watcher *, callback)>, which expects a callback to be provided. This |
975 | (watcher *, callback)>, which expects a callback to be provided. This |
810 | callback gets invoked each time the event occurs (or, in the case of I/O |
976 | callback gets invoked each time the event occurs (or, in the case of I/O |
811 | watchers, each time the event loop detects that the file descriptor given |
977 | watchers, each time the event loop detects that the file descriptor given |
812 | is readable and/or writable). |
978 | is readable and/or writable). |
813 | |
979 | |
814 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
980 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
815 | with arguments specific to this watcher type. There is also a macro |
981 | macro to configure it, with arguments specific to the watcher type. There |
816 | to combine initialisation and setting in one call: C<< ev_<type>_init |
982 | is also a macro to combine initialisation and setting in one call: C<< |
817 | (watcher *, callback, ...) >>. |
983 | ev_TYPE_init (watcher *, callback, ...) >>. |
818 | |
984 | |
819 | To make the watcher actually watch out for events, you have to start it |
985 | To make the watcher actually watch out for events, you have to start it |
820 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
986 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
821 | *) >>), and you can stop watching for events at any time by calling the |
987 | *) >>), and you can stop watching for events at any time by calling the |
822 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
988 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
823 | |
989 | |
824 | As long as your watcher is active (has been started but not stopped) you |
990 | As long as your watcher is active (has been started but not stopped) you |
825 | must not touch the values stored in it. Most specifically you must never |
991 | must not touch the values stored in it. Most specifically you must never |
826 | reinitialise it or call its C<set> macro. |
992 | reinitialise it or call its C<ev_TYPE_set> macro. |
827 | |
993 | |
828 | Each and every callback receives the event loop pointer as first, the |
994 | Each and every callback receives the event loop pointer as first, the |
829 | registered watcher structure as second, and a bitset of received events as |
995 | registered watcher structure as second, and a bitset of received events as |
830 | third argument. |
996 | third argument. |
831 | |
997 | |
… | |
… | |
889 | |
1055 | |
890 | =item C<EV_ASYNC> |
1056 | =item C<EV_ASYNC> |
891 | |
1057 | |
892 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1058 | The given async watcher has been asynchronously notified (see C<ev_async>). |
893 | |
1059 | |
|
|
1060 | =item C<EV_CUSTOM> |
|
|
1061 | |
|
|
1062 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1063 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
1064 | |
894 | =item C<EV_ERROR> |
1065 | =item C<EV_ERROR> |
895 | |
1066 | |
896 | An unspecified error has occurred, the watcher has been stopped. This might |
1067 | An unspecified error has occurred, the watcher has been stopped. This might |
897 | happen because the watcher could not be properly started because libev |
1068 | happen because the watcher could not be properly started because libev |
898 | ran out of memory, a file descriptor was found to be closed or any other |
1069 | ran out of memory, a file descriptor was found to be closed or any other |
… | |
… | |
912 | |
1083 | |
913 | =back |
1084 | =back |
914 | |
1085 | |
915 | =head2 GENERIC WATCHER FUNCTIONS |
1086 | =head2 GENERIC WATCHER FUNCTIONS |
916 | |
1087 | |
917 | In the following description, C<TYPE> stands for the watcher type, |
|
|
918 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
919 | |
|
|
920 | =over 4 |
1088 | =over 4 |
921 | |
1089 | |
922 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1090 | =item C<ev_init> (ev_TYPE *watcher, callback) |
923 | |
1091 | |
924 | This macro initialises the generic portion of a watcher. The contents |
1092 | This macro initialises the generic portion of a watcher. The contents |
… | |
… | |
1016 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1184 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1017 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1185 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1018 | before watchers with lower priority, but priority will not keep watchers |
1186 | before watchers with lower priority, but priority will not keep watchers |
1019 | from being executed (except for C<ev_idle> watchers). |
1187 | from being executed (except for C<ev_idle> watchers). |
1020 | |
1188 | |
1021 | This means that priorities are I<only> used for ordering callback |
|
|
1022 | invocation after new events have been received. This is useful, for |
|
|
1023 | example, to reduce latency after idling, or more often, to bind two |
|
|
1024 | watchers on the same event and make sure one is called first. |
|
|
1025 | |
|
|
1026 | If you need to suppress invocation when higher priority events are pending |
1189 | If you need to suppress invocation when higher priority events are pending |
1027 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1190 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1028 | |
1191 | |
1029 | You I<must not> change the priority of a watcher as long as it is active or |
1192 | You I<must not> change the priority of a watcher as long as it is active or |
1030 | pending. |
1193 | pending. |
1031 | |
1194 | |
|
|
1195 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1196 | fine, as long as you do not mind that the priority value you query might |
|
|
1197 | or might not have been clamped to the valid range. |
|
|
1198 | |
1032 | The default priority used by watchers when no priority has been set is |
1199 | The default priority used by watchers when no priority has been set is |
1033 | always C<0>, which is supposed to not be too high and not be too low :). |
1200 | always C<0>, which is supposed to not be too high and not be too low :). |
1034 | |
1201 | |
1035 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1202 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1036 | fine, as long as you do not mind that the priority value you query might |
1203 | priorities. |
1037 | or might not have been adjusted to be within valid range. |
|
|
1038 | |
1204 | |
1039 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1205 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1040 | |
1206 | |
1041 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1207 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1042 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1208 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1107 | #include <stddef.h> |
1273 | #include <stddef.h> |
1108 | |
1274 | |
1109 | static void |
1275 | static void |
1110 | t1_cb (EV_P_ ev_timer *w, int revents) |
1276 | t1_cb (EV_P_ ev_timer *w, int revents) |
1111 | { |
1277 | { |
1112 | struct my_biggy big = (struct my_biggy * |
1278 | struct my_biggy big = (struct my_biggy *) |
1113 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1279 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1114 | } |
1280 | } |
1115 | |
1281 | |
1116 | static void |
1282 | static void |
1117 | t2_cb (EV_P_ ev_timer *w, int revents) |
1283 | t2_cb (EV_P_ ev_timer *w, int revents) |
1118 | { |
1284 | { |
1119 | struct my_biggy big = (struct my_biggy * |
1285 | struct my_biggy big = (struct my_biggy *) |
1120 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1286 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1121 | } |
1287 | } |
|
|
1288 | |
|
|
1289 | =head2 WATCHER PRIORITY MODELS |
|
|
1290 | |
|
|
1291 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1292 | integers that influence the ordering of event callback invocation |
|
|
1293 | between watchers in some way, all else being equal. |
|
|
1294 | |
|
|
1295 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1296 | description for the more technical details such as the actual priority |
|
|
1297 | range. |
|
|
1298 | |
|
|
1299 | There are two common ways how these these priorities are being interpreted |
|
|
1300 | by event loops: |
|
|
1301 | |
|
|
1302 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1303 | of lower priority watchers, which means as long as higher priority |
|
|
1304 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1305 | |
|
|
1306 | The less common only-for-ordering model uses priorities solely to order |
|
|
1307 | callback invocation within a single event loop iteration: Higher priority |
|
|
1308 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1309 | before polling for new events. |
|
|
1310 | |
|
|
1311 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1312 | except for idle watchers (which use the lock-out model). |
|
|
1313 | |
|
|
1314 | The rationale behind this is that implementing the lock-out model for |
|
|
1315 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1316 | libraries will just poll for the same events again and again as long as |
|
|
1317 | their callbacks have not been executed, which is very inefficient in the |
|
|
1318 | common case of one high-priority watcher locking out a mass of lower |
|
|
1319 | priority ones. |
|
|
1320 | |
|
|
1321 | Static (ordering) priorities are most useful when you have two or more |
|
|
1322 | watchers handling the same resource: a typical usage example is having an |
|
|
1323 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1324 | timeouts. Under load, data might be received while the program handles |
|
|
1325 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1326 | handler will be executed before checking for data. In that case, giving |
|
|
1327 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1328 | handled first even under adverse conditions (which is usually, but not |
|
|
1329 | always, what you want). |
|
|
1330 | |
|
|
1331 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1332 | will only be executed when no same or higher priority watchers have |
|
|
1333 | received events, they can be used to implement the "lock-out" model when |
|
|
1334 | required. |
|
|
1335 | |
|
|
1336 | For example, to emulate how many other event libraries handle priorities, |
|
|
1337 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1338 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1339 | processing is done in the idle watcher callback. This causes libev to |
|
|
1340 | continously poll and process kernel event data for the watcher, but when |
|
|
1341 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1342 | workable. |
|
|
1343 | |
|
|
1344 | Usually, however, the lock-out model implemented that way will perform |
|
|
1345 | miserably under the type of load it was designed to handle. In that case, |
|
|
1346 | it might be preferable to stop the real watcher before starting the |
|
|
1347 | idle watcher, so the kernel will not have to process the event in case |
|
|
1348 | the actual processing will be delayed for considerable time. |
|
|
1349 | |
|
|
1350 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1351 | priority than the default, and which should only process data when no |
|
|
1352 | other events are pending: |
|
|
1353 | |
|
|
1354 | ev_idle idle; // actual processing watcher |
|
|
1355 | ev_io io; // actual event watcher |
|
|
1356 | |
|
|
1357 | static void |
|
|
1358 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1359 | { |
|
|
1360 | // stop the I/O watcher, we received the event, but |
|
|
1361 | // are not yet ready to handle it. |
|
|
1362 | ev_io_stop (EV_A_ w); |
|
|
1363 | |
|
|
1364 | // start the idle watcher to ahndle the actual event. |
|
|
1365 | // it will not be executed as long as other watchers |
|
|
1366 | // with the default priority are receiving events. |
|
|
1367 | ev_idle_start (EV_A_ &idle); |
|
|
1368 | } |
|
|
1369 | |
|
|
1370 | static void |
|
|
1371 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1372 | { |
|
|
1373 | // actual processing |
|
|
1374 | read (STDIN_FILENO, ...); |
|
|
1375 | |
|
|
1376 | // have to start the I/O watcher again, as |
|
|
1377 | // we have handled the event |
|
|
1378 | ev_io_start (EV_P_ &io); |
|
|
1379 | } |
|
|
1380 | |
|
|
1381 | // initialisation |
|
|
1382 | ev_idle_init (&idle, idle_cb); |
|
|
1383 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1384 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1385 | |
|
|
1386 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1387 | low-priority connections can not be locked out forever under load. This |
|
|
1388 | enables your program to keep a lower latency for important connections |
|
|
1389 | during short periods of high load, while not completely locking out less |
|
|
1390 | important ones. |
1122 | |
1391 | |
1123 | |
1392 | |
1124 | =head1 WATCHER TYPES |
1393 | =head1 WATCHER TYPES |
1125 | |
1394 | |
1126 | This section describes each watcher in detail, but will not repeat |
1395 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1152 | descriptors to non-blocking mode is also usually a good idea (but not |
1421 | descriptors to non-blocking mode is also usually a good idea (but not |
1153 | required if you know what you are doing). |
1422 | required if you know what you are doing). |
1154 | |
1423 | |
1155 | If you cannot use non-blocking mode, then force the use of a |
1424 | If you cannot use non-blocking mode, then force the use of a |
1156 | known-to-be-good backend (at the time of this writing, this includes only |
1425 | known-to-be-good backend (at the time of this writing, this includes only |
1157 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1426 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1427 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1428 | files) - libev doesn't guarentee any specific behaviour in that case. |
1158 | |
1429 | |
1159 | Another thing you have to watch out for is that it is quite easy to |
1430 | Another thing you have to watch out for is that it is quite easy to |
1160 | receive "spurious" readiness notifications, that is your callback might |
1431 | receive "spurious" readiness notifications, that is your callback might |
1161 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1432 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1162 | because there is no data. Not only are some backends known to create a |
1433 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1283 | year, it will still time out after (roughly) one hour. "Roughly" because |
1554 | year, it will still time out after (roughly) one hour. "Roughly" because |
1284 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1555 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1285 | monotonic clock option helps a lot here). |
1556 | monotonic clock option helps a lot here). |
1286 | |
1557 | |
1287 | The callback is guaranteed to be invoked only I<after> its timeout has |
1558 | The callback is guaranteed to be invoked only I<after> its timeout has |
1288 | passed, but if multiple timers become ready during the same loop iteration |
1559 | passed (not I<at>, so on systems with very low-resolution clocks this |
1289 | then order of execution is undefined. |
1560 | might introduce a small delay). If multiple timers become ready during the |
|
|
1561 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1562 | before ones of the same priority with later time-out values (but this is |
|
|
1563 | no longer true when a callback calls C<ev_loop> recursively). |
1290 | |
1564 | |
1291 | =head3 Be smart about timeouts |
1565 | =head3 Be smart about timeouts |
1292 | |
1566 | |
1293 | Many real-world problems invole some kind of time-out, usually for error |
1567 | Many real-world problems involve some kind of timeout, usually for error |
1294 | recovery. A typical example is an HTTP request - if the other side hangs, |
1568 | recovery. A typical example is an HTTP request - if the other side hangs, |
1295 | you want to raise some error after a while. |
1569 | you want to raise some error after a while. |
1296 | |
1570 | |
1297 | Here are some ways on how to handle this problem, from simple and |
1571 | What follows are some ways to handle this problem, from obvious and |
1298 | inefficient to very efficient. |
1572 | inefficient to smart and efficient. |
1299 | |
1573 | |
1300 | In the following examples a 60 second activity timeout is assumed - a |
1574 | In the following, a 60 second activity timeout is assumed - a timeout that |
1301 | timeout that gets reset to 60 seconds each time some data ("a lifesign") |
1575 | gets reset to 60 seconds each time there is activity (e.g. each time some |
1302 | was received. |
1576 | data or other life sign was received). |
1303 | |
1577 | |
1304 | =over 4 |
1578 | =over 4 |
1305 | |
1579 | |
1306 | =item 1. Use a timer and stop, reinitialise, start it on activity. |
1580 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
1307 | |
1581 | |
1308 | This is the most obvious, but not the most simple way: In the beginning, |
1582 | This is the most obvious, but not the most simple way: In the beginning, |
1309 | start the watcher: |
1583 | start the watcher: |
1310 | |
1584 | |
1311 | ev_timer_init (timer, callback, 60., 0.); |
1585 | ev_timer_init (timer, callback, 60., 0.); |
1312 | ev_timer_start (loop, timer); |
1586 | ev_timer_start (loop, timer); |
1313 | |
1587 | |
1314 | Then, each time there is some activity, C<ev_timer_stop> the timer, |
1588 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
1315 | initialise it again, and start it: |
1589 | and start it again: |
1316 | |
1590 | |
1317 | ev_timer_stop (loop, timer); |
1591 | ev_timer_stop (loop, timer); |
1318 | ev_timer_set (timer, 60., 0.); |
1592 | ev_timer_set (timer, 60., 0.); |
1319 | ev_timer_start (loop, timer); |
1593 | ev_timer_start (loop, timer); |
1320 | |
1594 | |
1321 | This is relatively simple to implement, but means that each time there |
1595 | This is relatively simple to implement, but means that each time there is |
1322 | is some activity, libev will first have to remove the timer from it's |
1596 | some activity, libev will first have to remove the timer from its internal |
1323 | internal data strcuture and then add it again. |
1597 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1598 | still not a constant-time operation. |
1324 | |
1599 | |
1325 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
1600 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
1326 | |
1601 | |
1327 | This is the easiest way, and involves using C<ev_timer_again> instead of |
1602 | This is the easiest way, and involves using C<ev_timer_again> instead of |
1328 | C<ev_timer_start>. |
1603 | C<ev_timer_start>. |
1329 | |
1604 | |
1330 | For this, configure an C<ev_timer> with a C<repeat> value of C<60> and |
1605 | To implement this, configure an C<ev_timer> with a C<repeat> value |
1331 | then call C<ev_timer_again> at start and each time you successfully read |
1606 | of C<60> and then call C<ev_timer_again> at start and each time you |
1332 | or write some data. If you go into an idle state where you do not expect |
1607 | successfully read or write some data. If you go into an idle state where |
1333 | data to travel on the socket, you can C<ev_timer_stop> the timer, and |
1608 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
1334 | C<ev_timer_again> will automatically restart it if need be. |
1609 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
1335 | |
1610 | |
1336 | That means you can ignore the C<after> value and C<ev_timer_start> |
1611 | That means you can ignore both the C<ev_timer_start> function and the |
1337 | altogether and only ever use the C<repeat> value and C<ev_timer_again>. |
1612 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1613 | member and C<ev_timer_again>. |
1338 | |
1614 | |
1339 | At start: |
1615 | At start: |
1340 | |
1616 | |
1341 | ev_timer_init (timer, callback, 0., 60.); |
1617 | ev_init (timer, callback); |
|
|
1618 | timer->repeat = 60.; |
1342 | ev_timer_again (loop, timer); |
1619 | ev_timer_again (loop, timer); |
1343 | |
1620 | |
1344 | Each time you receive some data: |
1621 | Each time there is some activity: |
1345 | |
1622 | |
1346 | ev_timer_again (loop, timer); |
1623 | ev_timer_again (loop, timer); |
1347 | |
1624 | |
1348 | It is even possible to change the time-out on the fly: |
1625 | It is even possible to change the time-out on the fly, regardless of |
|
|
1626 | whether the watcher is active or not: |
1349 | |
1627 | |
1350 | timer->repeat = 30.; |
1628 | timer->repeat = 30.; |
1351 | ev_timer_again (loop, timer); |
1629 | ev_timer_again (loop, timer); |
1352 | |
1630 | |
1353 | This is slightly more efficient then stopping/starting the timer each time |
1631 | This is slightly more efficient then stopping/starting the timer each time |
1354 | you want to modify its timeout value, as libev does not have to completely |
1632 | you want to modify its timeout value, as libev does not have to completely |
1355 | remove and re-insert the timer from/into it's internal data structure. |
1633 | remove and re-insert the timer from/into its internal data structure. |
|
|
1634 | |
|
|
1635 | It is, however, even simpler than the "obvious" way to do it. |
1356 | |
1636 | |
1357 | =item 3. Let the timer time out, but then re-arm it as required. |
1637 | =item 3. Let the timer time out, but then re-arm it as required. |
1358 | |
1638 | |
1359 | This method is more tricky, but usually most efficient: Most timeouts are |
1639 | This method is more tricky, but usually most efficient: Most timeouts are |
1360 | relatively long compared to the loop iteration time - in our example, |
1640 | relatively long compared to the intervals between other activity - in |
1361 | within 60 seconds, there are usually many I/O events with associated |
1641 | our example, within 60 seconds, there are usually many I/O events with |
1362 | activity resets. |
1642 | associated activity resets. |
1363 | |
1643 | |
1364 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1644 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1365 | but remember the time of last activity, and check for a real timeout only |
1645 | but remember the time of last activity, and check for a real timeout only |
1366 | within the callback: |
1646 | within the callback: |
1367 | |
1647 | |
1368 | ev_tstamp last_activity; // time of last activity |
1648 | ev_tstamp last_activity; // time of last activity |
1369 | |
1649 | |
1370 | static void |
1650 | static void |
1371 | callback (EV_P_ ev_timer *w, int revents) |
1651 | callback (EV_P_ ev_timer *w, int revents) |
1372 | { |
1652 | { |
1373 | ev_tstamp now = ev_now (EV_A); |
1653 | ev_tstamp now = ev_now (EV_A); |
1374 | ev_tstamp timeout = last_activity + 60.; |
1654 | ev_tstamp timeout = last_activity + 60.; |
1375 | |
1655 | |
1376 | // if last_activity is older than now - timeout, we did time out |
1656 | // if last_activity + 60. is older than now, we did time out |
1377 | if (timeout < now) |
1657 | if (timeout < now) |
1378 | { |
1658 | { |
1379 | // timeout occured, take action |
1659 | // timeout occured, take action |
1380 | } |
1660 | } |
1381 | else |
1661 | else |
1382 | { |
1662 | { |
1383 | // callback was invoked, but there was some activity, re-arm |
1663 | // callback was invoked, but there was some activity, re-arm |
1384 | // to fire in last_activity + 60. |
1664 | // the watcher to fire in last_activity + 60, which is |
|
|
1665 | // guaranteed to be in the future, so "again" is positive: |
1385 | w->again = timeout - now; |
1666 | w->repeat = timeout - now; |
1386 | ev_timer_again (EV_A_ w); |
1667 | ev_timer_again (EV_A_ w); |
1387 | } |
1668 | } |
1388 | } |
1669 | } |
1389 | |
1670 | |
1390 | To summarise the callback: first calculate the real time-out (defined as |
1671 | To summarise the callback: first calculate the real timeout (defined |
1391 | "60 seconds after the last activity"), then check if that time has been |
1672 | as "60 seconds after the last activity"), then check if that time has |
1392 | reached, which means there was a real timeout. Otherwise the callback was |
1673 | been reached, which means something I<did>, in fact, time out. Otherwise |
1393 | invoked too early (timeout is in the future), so re-schedule the timer to |
1674 | the callback was invoked too early (C<timeout> is in the future), so |
1394 | fire at that future time. |
1675 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1676 | a timeout then. |
1395 | |
1677 | |
1396 | Note how C<ev_timer_again> is used, taking advantage of the |
1678 | Note how C<ev_timer_again> is used, taking advantage of the |
1397 | C<ev_timer_again> optimisation when the timer is already running. |
1679 | C<ev_timer_again> optimisation when the timer is already running. |
1398 | |
1680 | |
1399 | This scheme causes more callback invocations (about one every 60 seconds), |
1681 | This scheme causes more callback invocations (about one every 60 seconds |
1400 | but virtually no calls to libev to change the timeout. |
1682 | minus half the average time between activity), but virtually no calls to |
|
|
1683 | libev to change the timeout. |
1401 | |
1684 | |
1402 | To start the timer, simply intiialise the watcher and C<last_activity>, |
1685 | To start the timer, simply initialise the watcher and set C<last_activity> |
1403 | then call the callback: |
1686 | to the current time (meaning we just have some activity :), then call the |
|
|
1687 | callback, which will "do the right thing" and start the timer: |
1404 | |
1688 | |
1405 | ev_timer_init (timer, callback); |
1689 | ev_init (timer, callback); |
1406 | last_activity = ev_now (loop); |
1690 | last_activity = ev_now (loop); |
1407 | callback (loop, timer, EV_TIMEOUT); |
1691 | callback (loop, timer, EV_TIMEOUT); |
1408 | |
1692 | |
1409 | And when there is some activity, simply remember the time in |
1693 | And when there is some activity, simply store the current time in |
1410 | C<last_activity>: |
1694 | C<last_activity>, no libev calls at all: |
1411 | |
1695 | |
1412 | last_actiivty = ev_now (loop); |
1696 | last_actiivty = ev_now (loop); |
1413 | |
1697 | |
1414 | This technique is slightly more complex, but in most cases where the |
1698 | This technique is slightly more complex, but in most cases where the |
1415 | time-out is unlikely to be triggered, much more efficient. |
1699 | time-out is unlikely to be triggered, much more efficient. |
1416 | |
1700 | |
|
|
1701 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1702 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1703 | fix things for you. |
|
|
1704 | |
|
|
1705 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1706 | |
|
|
1707 | If there is not one request, but many thousands (millions...), all |
|
|
1708 | employing some kind of timeout with the same timeout value, then one can |
|
|
1709 | do even better: |
|
|
1710 | |
|
|
1711 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1712 | at the I<end> of the list. |
|
|
1713 | |
|
|
1714 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1715 | the list is expected to fire (for example, using the technique #3). |
|
|
1716 | |
|
|
1717 | When there is some activity, remove the timer from the list, recalculate |
|
|
1718 | the timeout, append it to the end of the list again, and make sure to |
|
|
1719 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1720 | |
|
|
1721 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1722 | starting, stopping and updating the timers, at the expense of a major |
|
|
1723 | complication, and having to use a constant timeout. The constant timeout |
|
|
1724 | ensures that the list stays sorted. |
|
|
1725 | |
1417 | =back |
1726 | =back |
|
|
1727 | |
|
|
1728 | So which method the best? |
|
|
1729 | |
|
|
1730 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1731 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1732 | better, and isn't very complicated either. In most case, choosing either |
|
|
1733 | one is fine, with #3 being better in typical situations. |
|
|
1734 | |
|
|
1735 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1736 | rather complicated, but extremely efficient, something that really pays |
|
|
1737 | off after the first million or so of active timers, i.e. it's usually |
|
|
1738 | overkill :) |
1418 | |
1739 | |
1419 | =head3 The special problem of time updates |
1740 | =head3 The special problem of time updates |
1420 | |
1741 | |
1421 | Establishing the current time is a costly operation (it usually takes at |
1742 | Establishing the current time is a costly operation (it usually takes at |
1422 | least two system calls): EV therefore updates its idea of the current |
1743 | least two system calls): EV therefore updates its idea of the current |
… | |
… | |
1434 | |
1755 | |
1435 | If the event loop is suspended for a long time, you can also force an |
1756 | If the event loop is suspended for a long time, you can also force an |
1436 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1757 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1437 | ()>. |
1758 | ()>. |
1438 | |
1759 | |
|
|
1760 | =head3 The special problems of suspended animation |
|
|
1761 | |
|
|
1762 | When you leave the server world it is quite customary to hit machines that |
|
|
1763 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1764 | |
|
|
1765 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1766 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1767 | to run until the system is suspended, but they will not advance while the |
|
|
1768 | system is suspended. That means, on resume, it will be as if the program |
|
|
1769 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1770 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1771 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1772 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1773 | be adjusted accordingly. |
|
|
1774 | |
|
|
1775 | I would not be surprised to see different behaviour in different between |
|
|
1776 | operating systems, OS versions or even different hardware. |
|
|
1777 | |
|
|
1778 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1779 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1780 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1781 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1782 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1783 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1784 | |
|
|
1785 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1786 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1787 | deterministic behaviour in this case (you can do nothing against |
|
|
1788 | C<SIGSTOP>). |
|
|
1789 | |
1439 | =head3 Watcher-Specific Functions and Data Members |
1790 | =head3 Watcher-Specific Functions and Data Members |
1440 | |
1791 | |
1441 | =over 4 |
1792 | =over 4 |
1442 | |
1793 | |
1443 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1794 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1466 | If the timer is started but non-repeating, stop it (as if it timed out). |
1817 | If the timer is started but non-repeating, stop it (as if it timed out). |
1467 | |
1818 | |
1468 | If the timer is repeating, either start it if necessary (with the |
1819 | If the timer is repeating, either start it if necessary (with the |
1469 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1820 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1470 | |
1821 | |
1471 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1822 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1472 | usage example. |
1823 | usage example. |
1473 | |
1824 | |
1474 | =item ev_tstamp repeat [read-write] |
1825 | =item ev_tstamp repeat [read-write] |
1475 | |
1826 | |
1476 | The current C<repeat> value. Will be used each time the watcher times out |
1827 | The current C<repeat> value. Will be used each time the watcher times out |
… | |
… | |
1515 | =head2 C<ev_periodic> - to cron or not to cron? |
1866 | =head2 C<ev_periodic> - to cron or not to cron? |
1516 | |
1867 | |
1517 | Periodic watchers are also timers of a kind, but they are very versatile |
1868 | Periodic watchers are also timers of a kind, but they are very versatile |
1518 | (and unfortunately a bit complex). |
1869 | (and unfortunately a bit complex). |
1519 | |
1870 | |
1520 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1871 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1521 | but on wall clock time (absolute time). You can tell a periodic watcher |
1872 | relative time, the physical time that passes) but on wall clock time |
1522 | to trigger after some specific point in time. For example, if you tell a |
1873 | (absolute time, the thing you can read on your calender or clock). The |
1523 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1874 | difference is that wall clock time can run faster or slower than real |
1524 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1875 | time, and time jumps are not uncommon (e.g. when you adjust your |
1525 | clock to January of the previous year, then it will take more than year |
1876 | wrist-watch). |
1526 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1527 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1528 | |
1877 | |
|
|
1878 | You can tell a periodic watcher to trigger after some specific point |
|
|
1879 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1880 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1881 | not a delay) and then reset your system clock to January of the previous |
|
|
1882 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1883 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1884 | it, as it uses a relative timeout). |
|
|
1885 | |
1529 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1886 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1530 | such as triggering an event on each "midnight, local time", or other |
1887 | timers, such as triggering an event on each "midnight, local time", or |
1531 | complicated rules. |
1888 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1889 | those cannot react to time jumps. |
1532 | |
1890 | |
1533 | As with timers, the callback is guaranteed to be invoked only when the |
1891 | As with timers, the callback is guaranteed to be invoked only when the |
1534 | time (C<at>) has passed, but if multiple periodic timers become ready |
1892 | point in time where it is supposed to trigger has passed. If multiple |
1535 | during the same loop iteration, then order of execution is undefined. |
1893 | timers become ready during the same loop iteration then the ones with |
|
|
1894 | earlier time-out values are invoked before ones with later time-out values |
|
|
1895 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1536 | |
1896 | |
1537 | =head3 Watcher-Specific Functions and Data Members |
1897 | =head3 Watcher-Specific Functions and Data Members |
1538 | |
1898 | |
1539 | =over 4 |
1899 | =over 4 |
1540 | |
1900 | |
1541 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1901 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1542 | |
1902 | |
1543 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1903 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1544 | |
1904 | |
1545 | Lots of arguments, lets sort it out... There are basically three modes of |
1905 | Lots of arguments, let's sort it out... There are basically three modes of |
1546 | operation, and we will explain them from simplest to most complex: |
1906 | operation, and we will explain them from simplest to most complex: |
1547 | |
1907 | |
1548 | =over 4 |
1908 | =over 4 |
1549 | |
1909 | |
1550 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1910 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1551 | |
1911 | |
1552 | In this configuration the watcher triggers an event after the wall clock |
1912 | In this configuration the watcher triggers an event after the wall clock |
1553 | time C<at> has passed. It will not repeat and will not adjust when a time |
1913 | time C<offset> has passed. It will not repeat and will not adjust when a |
1554 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1914 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1555 | only run when the system clock reaches or surpasses this time. |
1915 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1916 | this point in time. |
1556 | |
1917 | |
1557 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1918 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1558 | |
1919 | |
1559 | In this mode the watcher will always be scheduled to time out at the next |
1920 | In this mode the watcher will always be scheduled to time out at the next |
1560 | C<at + N * interval> time (for some integer N, which can also be negative) |
1921 | C<offset + N * interval> time (for some integer N, which can also be |
1561 | and then repeat, regardless of any time jumps. |
1922 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1923 | argument is merely an offset into the C<interval> periods. |
1562 | |
1924 | |
1563 | This can be used to create timers that do not drift with respect to the |
1925 | This can be used to create timers that do not drift with respect to the |
1564 | system clock, for example, here is a C<ev_periodic> that triggers each |
1926 | system clock, for example, here is an C<ev_periodic> that triggers each |
1565 | hour, on the hour: |
1927 | hour, on the hour (with respect to UTC): |
1566 | |
1928 | |
1567 | ev_periodic_set (&periodic, 0., 3600., 0); |
1929 | ev_periodic_set (&periodic, 0., 3600., 0); |
1568 | |
1930 | |
1569 | This doesn't mean there will always be 3600 seconds in between triggers, |
1931 | This doesn't mean there will always be 3600 seconds in between triggers, |
1570 | but only that the callback will be called when the system time shows a |
1932 | but only that the callback will be called when the system time shows a |
1571 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1933 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1572 | by 3600. |
1934 | by 3600. |
1573 | |
1935 | |
1574 | Another way to think about it (for the mathematically inclined) is that |
1936 | Another way to think about it (for the mathematically inclined) is that |
1575 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1937 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1576 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1938 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1577 | |
1939 | |
1578 | For numerical stability it is preferable that the C<at> value is near |
1940 | For numerical stability it is preferable that the C<offset> value is near |
1579 | C<ev_now ()> (the current time), but there is no range requirement for |
1941 | C<ev_now ()> (the current time), but there is no range requirement for |
1580 | this value, and in fact is often specified as zero. |
1942 | this value, and in fact is often specified as zero. |
1581 | |
1943 | |
1582 | Note also that there is an upper limit to how often a timer can fire (CPU |
1944 | Note also that there is an upper limit to how often a timer can fire (CPU |
1583 | speed for example), so if C<interval> is very small then timing stability |
1945 | speed for example), so if C<interval> is very small then timing stability |
1584 | will of course deteriorate. Libev itself tries to be exact to be about one |
1946 | will of course deteriorate. Libev itself tries to be exact to be about one |
1585 | millisecond (if the OS supports it and the machine is fast enough). |
1947 | millisecond (if the OS supports it and the machine is fast enough). |
1586 | |
1948 | |
1587 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1949 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1588 | |
1950 | |
1589 | In this mode the values for C<interval> and C<at> are both being |
1951 | In this mode the values for C<interval> and C<offset> are both being |
1590 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1952 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1591 | reschedule callback will be called with the watcher as first, and the |
1953 | reschedule callback will be called with the watcher as first, and the |
1592 | current time as second argument. |
1954 | current time as second argument. |
1593 | |
1955 | |
1594 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1956 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1595 | ever, or make ANY event loop modifications whatsoever>. |
1957 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1958 | allowed by documentation here>. |
1596 | |
1959 | |
1597 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1960 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1598 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1961 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1599 | only event loop modification you are allowed to do). |
1962 | only event loop modification you are allowed to do). |
1600 | |
1963 | |
… | |
… | |
1630 | a different time than the last time it was called (e.g. in a crond like |
1993 | a different time than the last time it was called (e.g. in a crond like |
1631 | program when the crontabs have changed). |
1994 | program when the crontabs have changed). |
1632 | |
1995 | |
1633 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1996 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1634 | |
1997 | |
1635 | When active, returns the absolute time that the watcher is supposed to |
1998 | When active, returns the absolute time that the watcher is supposed |
1636 | trigger next. |
1999 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2000 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2001 | rescheduling modes. |
1637 | |
2002 | |
1638 | =item ev_tstamp offset [read-write] |
2003 | =item ev_tstamp offset [read-write] |
1639 | |
2004 | |
1640 | When repeating, this contains the offset value, otherwise this is the |
2005 | When repeating, this contains the offset value, otherwise this is the |
1641 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2006 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2007 | although libev might modify this value for better numerical stability). |
1642 | |
2008 | |
1643 | Can be modified any time, but changes only take effect when the periodic |
2009 | Can be modified any time, but changes only take effect when the periodic |
1644 | timer fires or C<ev_periodic_again> is being called. |
2010 | timer fires or C<ev_periodic_again> is being called. |
1645 | |
2011 | |
1646 | =item ev_tstamp interval [read-write] |
2012 | =item ev_tstamp interval [read-write] |
… | |
… | |
1755 | some child status changes (most typically when a child of yours dies or |
2121 | some child status changes (most typically when a child of yours dies or |
1756 | exits). It is permissible to install a child watcher I<after> the child |
2122 | exits). It is permissible to install a child watcher I<after> the child |
1757 | has been forked (which implies it might have already exited), as long |
2123 | has been forked (which implies it might have already exited), as long |
1758 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2124 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1759 | forking and then immediately registering a watcher for the child is fine, |
2125 | forking and then immediately registering a watcher for the child is fine, |
1760 | but forking and registering a watcher a few event loop iterations later is |
2126 | but forking and registering a watcher a few event loop iterations later or |
1761 | not. |
2127 | in the next callback invocation is not. |
1762 | |
2128 | |
1763 | Only the default event loop is capable of handling signals, and therefore |
2129 | Only the default event loop is capable of handling signals, and therefore |
1764 | you can only register child watchers in the default event loop. |
2130 | you can only register child watchers in the default event loop. |
|
|
2131 | |
|
|
2132 | Due to some design glitches inside libev, child watchers will always be |
|
|
2133 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2134 | libev) |
1765 | |
2135 | |
1766 | =head3 Process Interaction |
2136 | =head3 Process Interaction |
1767 | |
2137 | |
1768 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2138 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1769 | initialised. This is necessary to guarantee proper behaviour even if |
2139 | initialised. This is necessary to guarantee proper behaviour even if |
… | |
… | |
1852 | |
2222 | |
1853 | |
2223 | |
1854 | =head2 C<ev_stat> - did the file attributes just change? |
2224 | =head2 C<ev_stat> - did the file attributes just change? |
1855 | |
2225 | |
1856 | This watches a file system path for attribute changes. That is, it calls |
2226 | This watches a file system path for attribute changes. That is, it calls |
1857 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2227 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1858 | compared to the last time, invoking the callback if it did. |
2228 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2229 | it did. |
1859 | |
2230 | |
1860 | The path does not need to exist: changing from "path exists" to "path does |
2231 | The path does not need to exist: changing from "path exists" to "path does |
1861 | not exist" is a status change like any other. The condition "path does |
2232 | not exist" is a status change like any other. The condition "path does not |
1862 | not exist" is signified by the C<st_nlink> field being zero (which is |
2233 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1863 | otherwise always forced to be at least one) and all the other fields of |
2234 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1864 | the stat buffer having unspecified contents. |
2235 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2236 | contents. |
1865 | |
2237 | |
1866 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2238 | The path I<must not> end in a slash or contain special components such as |
|
|
2239 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1867 | relative and your working directory changes, the behaviour is undefined. |
2240 | your working directory changes, then the behaviour is undefined. |
1868 | |
2241 | |
1869 | Since there is no standard kernel interface to do this, the portable |
2242 | Since there is no portable change notification interface available, the |
1870 | implementation simply calls C<stat (2)> regularly on the path to see if |
2243 | portable implementation simply calls C<stat(2)> regularly on the path |
1871 | it changed somehow. You can specify a recommended polling interval for |
2244 | to see if it changed somehow. You can specify a recommended polling |
1872 | this case. If you specify a polling interval of C<0> (highly recommended!) |
2245 | interval for this case. If you specify a polling interval of C<0> (highly |
1873 | then a I<suitable, unspecified default> value will be used (which |
2246 | recommended!) then a I<suitable, unspecified default> value will be used |
1874 | you can expect to be around five seconds, although this might change |
2247 | (which you can expect to be around five seconds, although this might |
1875 | dynamically). Libev will also impose a minimum interval which is currently |
2248 | change dynamically). Libev will also impose a minimum interval which is |
1876 | around C<0.1>, but thats usually overkill. |
2249 | currently around C<0.1>, but that's usually overkill. |
1877 | |
2250 | |
1878 | This watcher type is not meant for massive numbers of stat watchers, |
2251 | This watcher type is not meant for massive numbers of stat watchers, |
1879 | as even with OS-supported change notifications, this can be |
2252 | as even with OS-supported change notifications, this can be |
1880 | resource-intensive. |
2253 | resource-intensive. |
1881 | |
2254 | |
1882 | At the time of this writing, the only OS-specific interface implemented |
2255 | At the time of this writing, the only OS-specific interface implemented |
1883 | is the Linux inotify interface (implementing kqueue support is left as |
2256 | is the Linux inotify interface (implementing kqueue support is left as an |
1884 | an exercise for the reader. Note, however, that the author sees no way |
2257 | exercise for the reader. Note, however, that the author sees no way of |
1885 | of implementing C<ev_stat> semantics with kqueue). |
2258 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1886 | |
2259 | |
1887 | =head3 ABI Issues (Largefile Support) |
2260 | =head3 ABI Issues (Largefile Support) |
1888 | |
2261 | |
1889 | Libev by default (unless the user overrides this) uses the default |
2262 | Libev by default (unless the user overrides this) uses the default |
1890 | compilation environment, which means that on systems with large file |
2263 | compilation environment, which means that on systems with large file |
1891 | support disabled by default, you get the 32 bit version of the stat |
2264 | support disabled by default, you get the 32 bit version of the stat |
1892 | structure. When using the library from programs that change the ABI to |
2265 | structure. When using the library from programs that change the ABI to |
1893 | use 64 bit file offsets the programs will fail. In that case you have to |
2266 | use 64 bit file offsets the programs will fail. In that case you have to |
1894 | compile libev with the same flags to get binary compatibility. This is |
2267 | compile libev with the same flags to get binary compatibility. This is |
1895 | obviously the case with any flags that change the ABI, but the problem is |
2268 | obviously the case with any flags that change the ABI, but the problem is |
1896 | most noticeably disabled with ev_stat and large file support. |
2269 | most noticeably displayed with ev_stat and large file support. |
1897 | |
2270 | |
1898 | The solution for this is to lobby your distribution maker to make large |
2271 | The solution for this is to lobby your distribution maker to make large |
1899 | file interfaces available by default (as e.g. FreeBSD does) and not |
2272 | file interfaces available by default (as e.g. FreeBSD does) and not |
1900 | optional. Libev cannot simply switch on large file support because it has |
2273 | optional. Libev cannot simply switch on large file support because it has |
1901 | to exchange stat structures with application programs compiled using the |
2274 | to exchange stat structures with application programs compiled using the |
1902 | default compilation environment. |
2275 | default compilation environment. |
1903 | |
2276 | |
1904 | =head3 Inotify and Kqueue |
2277 | =head3 Inotify and Kqueue |
1905 | |
2278 | |
1906 | When C<inotify (7)> support has been compiled into libev (generally |
2279 | When C<inotify (7)> support has been compiled into libev and present at |
1907 | only available with Linux 2.6.25 or above due to bugs in earlier |
2280 | runtime, it will be used to speed up change detection where possible. The |
1908 | implementations) and present at runtime, it will be used to speed up |
2281 | inotify descriptor will be created lazily when the first C<ev_stat> |
1909 | change detection where possible. The inotify descriptor will be created |
2282 | watcher is being started. |
1910 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1911 | |
2283 | |
1912 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2284 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1913 | except that changes might be detected earlier, and in some cases, to avoid |
2285 | except that changes might be detected earlier, and in some cases, to avoid |
1914 | making regular C<stat> calls. Even in the presence of inotify support |
2286 | making regular C<stat> calls. Even in the presence of inotify support |
1915 | there are many cases where libev has to resort to regular C<stat> polling, |
2287 | there are many cases where libev has to resort to regular C<stat> polling, |
1916 | but as long as the path exists, libev usually gets away without polling. |
2288 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2289 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2290 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2291 | xfs are fully working) libev usually gets away without polling. |
1917 | |
2292 | |
1918 | There is no support for kqueue, as apparently it cannot be used to |
2293 | There is no support for kqueue, as apparently it cannot be used to |
1919 | implement this functionality, due to the requirement of having a file |
2294 | implement this functionality, due to the requirement of having a file |
1920 | descriptor open on the object at all times, and detecting renames, unlinks |
2295 | descriptor open on the object at all times, and detecting renames, unlinks |
1921 | etc. is difficult. |
2296 | etc. is difficult. |
1922 | |
2297 | |
|
|
2298 | =head3 C<stat ()> is a synchronous operation |
|
|
2299 | |
|
|
2300 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2301 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2302 | ()>, which is a synchronous operation. |
|
|
2303 | |
|
|
2304 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2305 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2306 | as the path data is usually in memory already (except when starting the |
|
|
2307 | watcher). |
|
|
2308 | |
|
|
2309 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2310 | time due to network issues, and even under good conditions, a stat call |
|
|
2311 | often takes multiple milliseconds. |
|
|
2312 | |
|
|
2313 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2314 | paths, although this is fully supported by libev. |
|
|
2315 | |
1923 | =head3 The special problem of stat time resolution |
2316 | =head3 The special problem of stat time resolution |
1924 | |
2317 | |
1925 | The C<stat ()> system call only supports full-second resolution portably, and |
2318 | The C<stat ()> system call only supports full-second resolution portably, |
1926 | even on systems where the resolution is higher, most file systems still |
2319 | and even on systems where the resolution is higher, most file systems |
1927 | only support whole seconds. |
2320 | still only support whole seconds. |
1928 | |
2321 | |
1929 | That means that, if the time is the only thing that changes, you can |
2322 | That means that, if the time is the only thing that changes, you can |
1930 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2323 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1931 | calls your callback, which does something. When there is another update |
2324 | calls your callback, which does something. When there is another update |
1932 | within the same second, C<ev_stat> will be unable to detect unless the |
2325 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
2075 | |
2468 | |
2076 | =head3 Watcher-Specific Functions and Data Members |
2469 | =head3 Watcher-Specific Functions and Data Members |
2077 | |
2470 | |
2078 | =over 4 |
2471 | =over 4 |
2079 | |
2472 | |
2080 | =item ev_idle_init (ev_signal *, callback) |
2473 | =item ev_idle_init (ev_idle *, callback) |
2081 | |
2474 | |
2082 | Initialises and configures the idle watcher - it has no parameters of any |
2475 | Initialises and configures the idle watcher - it has no parameters of any |
2083 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2476 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2084 | believe me. |
2477 | believe me. |
2085 | |
2478 | |
… | |
… | |
2098 | // no longer anything immediate to do. |
2491 | // no longer anything immediate to do. |
2099 | } |
2492 | } |
2100 | |
2493 | |
2101 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2494 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2102 | ev_idle_init (idle_watcher, idle_cb); |
2495 | ev_idle_init (idle_watcher, idle_cb); |
2103 | ev_idle_start (loop, idle_cb); |
2496 | ev_idle_start (loop, idle_watcher); |
2104 | |
2497 | |
2105 | |
2498 | |
2106 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2499 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2107 | |
2500 | |
2108 | Prepare and check watchers are usually (but not always) used in pairs: |
2501 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2201 | struct pollfd fds [nfd]; |
2594 | struct pollfd fds [nfd]; |
2202 | // actual code will need to loop here and realloc etc. |
2595 | // actual code will need to loop here and realloc etc. |
2203 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2596 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2204 | |
2597 | |
2205 | /* the callback is illegal, but won't be called as we stop during check */ |
2598 | /* the callback is illegal, but won't be called as we stop during check */ |
2206 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2599 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2207 | ev_timer_start (loop, &tw); |
2600 | ev_timer_start (loop, &tw); |
2208 | |
2601 | |
2209 | // create one ev_io per pollfd |
2602 | // create one ev_io per pollfd |
2210 | for (int i = 0; i < nfd; ++i) |
2603 | for (int i = 0; i < nfd; ++i) |
2211 | { |
2604 | { |
… | |
… | |
2324 | some fds have to be watched and handled very quickly (with low latency), |
2717 | some fds have to be watched and handled very quickly (with low latency), |
2325 | and even priorities and idle watchers might have too much overhead. In |
2718 | and even priorities and idle watchers might have too much overhead. In |
2326 | this case you would put all the high priority stuff in one loop and all |
2719 | this case you would put all the high priority stuff in one loop and all |
2327 | the rest in a second one, and embed the second one in the first. |
2720 | the rest in a second one, and embed the second one in the first. |
2328 | |
2721 | |
2329 | As long as the watcher is active, the callback will be invoked every time |
2722 | As long as the watcher is active, the callback will be invoked every |
2330 | there might be events pending in the embedded loop. The callback must then |
2723 | time there might be events pending in the embedded loop. The callback |
2331 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2724 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2332 | their callbacks (you could also start an idle watcher to give the embedded |
2725 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2333 | loop strictly lower priority for example). You can also set the callback |
2726 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2334 | to C<0>, in which case the embed watcher will automatically execute the |
2727 | to give the embedded loop strictly lower priority for example). |
2335 | embedded loop sweep. |
|
|
2336 | |
2728 | |
2337 | As long as the watcher is started it will automatically handle events. The |
2729 | You can also set the callback to C<0>, in which case the embed watcher |
2338 | callback will be invoked whenever some events have been handled. You can |
2730 | will automatically execute the embedded loop sweep whenever necessary. |
2339 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2340 | interested in that. |
|
|
2341 | |
2731 | |
2342 | Also, there have not currently been made special provisions for forking: |
2732 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2343 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2733 | is active, i.e., the embedded loop will automatically be forked when the |
2344 | but you will also have to stop and restart any C<ev_embed> watchers |
2734 | embedding loop forks. In other cases, the user is responsible for calling |
2345 | yourself - but you can use a fork watcher to handle this automatically, |
2735 | C<ev_loop_fork> on the embedded loop. |
2346 | and future versions of libev might do just that. |
|
|
2347 | |
2736 | |
2348 | Unfortunately, not all backends are embeddable: only the ones returned by |
2737 | Unfortunately, not all backends are embeddable: only the ones returned by |
2349 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2738 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2350 | portable one. |
2739 | portable one. |
2351 | |
2740 | |
… | |
… | |
2445 | event loop blocks next and before C<ev_check> watchers are being called, |
2834 | event loop blocks next and before C<ev_check> watchers are being called, |
2446 | and only in the child after the fork. If whoever good citizen calling |
2835 | and only in the child after the fork. If whoever good citizen calling |
2447 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2836 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2448 | handlers will be invoked, too, of course. |
2837 | handlers will be invoked, too, of course. |
2449 | |
2838 | |
|
|
2839 | =head3 The special problem of life after fork - how is it possible? |
|
|
2840 | |
|
|
2841 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2842 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2843 | sequence should be handled by libev without any problems. |
|
|
2844 | |
|
|
2845 | This changes when the application actually wants to do event handling |
|
|
2846 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2847 | fork. |
|
|
2848 | |
|
|
2849 | The default mode of operation (for libev, with application help to detect |
|
|
2850 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2851 | when I<either> the parent I<or> the child process continues. |
|
|
2852 | |
|
|
2853 | When both processes want to continue using libev, then this is usually the |
|
|
2854 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2855 | supposed to continue with all watchers in place as before, while the other |
|
|
2856 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2857 | |
|
|
2858 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2859 | simply create a new event loop, which of course will be "empty", and |
|
|
2860 | use that for new watchers. This has the advantage of not touching more |
|
|
2861 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2862 | disadvantage of having to use multiple event loops (which do not support |
|
|
2863 | signal watchers). |
|
|
2864 | |
|
|
2865 | When this is not possible, or you want to use the default loop for |
|
|
2866 | other reasons, then in the process that wants to start "fresh", call |
|
|
2867 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2868 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2869 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2870 | also that in that case, you have to re-register any signal watchers. |
|
|
2871 | |
2450 | =head3 Watcher-Specific Functions and Data Members |
2872 | =head3 Watcher-Specific Functions and Data Members |
2451 | |
2873 | |
2452 | =over 4 |
2874 | =over 4 |
2453 | |
2875 | |
2454 | =item ev_fork_init (ev_signal *, callback) |
2876 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2571 | =over 4 |
2993 | =over 4 |
2572 | |
2994 | |
2573 | =item ev_async_init (ev_async *, callback) |
2995 | =item ev_async_init (ev_async *, callback) |
2574 | |
2996 | |
2575 | Initialises and configures the async watcher - it has no parameters of any |
2997 | Initialises and configures the async watcher - it has no parameters of any |
2576 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2998 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2577 | trust me. |
2999 | trust me. |
2578 | |
3000 | |
2579 | =item ev_async_send (loop, ev_async *) |
3001 | =item ev_async_send (loop, ev_async *) |
2580 | |
3002 | |
2581 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3003 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2582 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3004 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2583 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3005 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2584 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3006 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2585 | section below on what exactly this means). |
3007 | section below on what exactly this means). |
2586 | |
3008 | |
|
|
3009 | Note that, as with other watchers in libev, multiple events might get |
|
|
3010 | compressed into a single callback invocation (another way to look at this |
|
|
3011 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3012 | reset when the event loop detects that). |
|
|
3013 | |
2587 | This call incurs the overhead of a system call only once per loop iteration, |
3014 | This call incurs the overhead of a system call only once per event loop |
2588 | so while the overhead might be noticeable, it doesn't apply to repeated |
3015 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2589 | calls to C<ev_async_send>. |
3016 | repeated calls to C<ev_async_send> for the same event loop. |
2590 | |
3017 | |
2591 | =item bool = ev_async_pending (ev_async *) |
3018 | =item bool = ev_async_pending (ev_async *) |
2592 | |
3019 | |
2593 | Returns a non-zero value when C<ev_async_send> has been called on the |
3020 | Returns a non-zero value when C<ev_async_send> has been called on the |
2594 | watcher but the event has not yet been processed (or even noted) by the |
3021 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2597 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3024 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2598 | the loop iterates next and checks for the watcher to have become active, |
3025 | the loop iterates next and checks for the watcher to have become active, |
2599 | it will reset the flag again. C<ev_async_pending> can be used to very |
3026 | it will reset the flag again. C<ev_async_pending> can be used to very |
2600 | quickly check whether invoking the loop might be a good idea. |
3027 | quickly check whether invoking the loop might be a good idea. |
2601 | |
3028 | |
2602 | Not that this does I<not> check whether the watcher itself is pending, only |
3029 | Not that this does I<not> check whether the watcher itself is pending, |
2603 | whether it has been requested to make this watcher pending. |
3030 | only whether it has been requested to make this watcher pending: there |
|
|
3031 | is a time window between the event loop checking and resetting the async |
|
|
3032 | notification, and the callback being invoked. |
2604 | |
3033 | |
2605 | =back |
3034 | =back |
2606 | |
3035 | |
2607 | |
3036 | |
2608 | =head1 OTHER FUNCTIONS |
3037 | =head1 OTHER FUNCTIONS |
… | |
… | |
2787 | |
3216 | |
2788 | myclass obj; |
3217 | myclass obj; |
2789 | ev::io iow; |
3218 | ev::io iow; |
2790 | iow.set <myclass, &myclass::io_cb> (&obj); |
3219 | iow.set <myclass, &myclass::io_cb> (&obj); |
2791 | |
3220 | |
|
|
3221 | =item w->set (object *) |
|
|
3222 | |
|
|
3223 | This is an B<experimental> feature that might go away in a future version. |
|
|
3224 | |
|
|
3225 | This is a variation of a method callback - leaving out the method to call |
|
|
3226 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3227 | functor objects without having to manually specify the C<operator ()> all |
|
|
3228 | the time. Incidentally, you can then also leave out the template argument |
|
|
3229 | list. |
|
|
3230 | |
|
|
3231 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3232 | int revents)>. |
|
|
3233 | |
|
|
3234 | See the method-C<set> above for more details. |
|
|
3235 | |
|
|
3236 | Example: use a functor object as callback. |
|
|
3237 | |
|
|
3238 | struct myfunctor |
|
|
3239 | { |
|
|
3240 | void operator() (ev::io &w, int revents) |
|
|
3241 | { |
|
|
3242 | ... |
|
|
3243 | } |
|
|
3244 | } |
|
|
3245 | |
|
|
3246 | myfunctor f; |
|
|
3247 | |
|
|
3248 | ev::io w; |
|
|
3249 | w.set (&f); |
|
|
3250 | |
2792 | =item w->set<function> (void *data = 0) |
3251 | =item w->set<function> (void *data = 0) |
2793 | |
3252 | |
2794 | Also sets a callback, but uses a static method or plain function as |
3253 | Also sets a callback, but uses a static method or plain function as |
2795 | callback. The optional C<data> argument will be stored in the watcher's |
3254 | callback. The optional C<data> argument will be stored in the watcher's |
2796 | C<data> member and is free for you to use. |
3255 | C<data> member and is free for you to use. |
… | |
… | |
2882 | L<http://software.schmorp.de/pkg/EV>. |
3341 | L<http://software.schmorp.de/pkg/EV>. |
2883 | |
3342 | |
2884 | =item Python |
3343 | =item Python |
2885 | |
3344 | |
2886 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3345 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2887 | seems to be quite complete and well-documented. Note, however, that the |
3346 | seems to be quite complete and well-documented. |
2888 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2889 | for everybody else, and therefore, should never be applied in an installed |
|
|
2890 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2891 | libev). |
|
|
2892 | |
3347 | |
2893 | =item Ruby |
3348 | =item Ruby |
2894 | |
3349 | |
2895 | Tony Arcieri has written a ruby extension that offers access to a subset |
3350 | Tony Arcieri has written a ruby extension that offers access to a subset |
2896 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3351 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2897 | more on top of it. It can be found via gem servers. Its homepage is at |
3352 | more on top of it. It can be found via gem servers. Its homepage is at |
2898 | L<http://rev.rubyforge.org/>. |
3353 | L<http://rev.rubyforge.org/>. |
2899 | |
3354 | |
|
|
3355 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3356 | makes rev work even on mingw. |
|
|
3357 | |
|
|
3358 | =item Haskell |
|
|
3359 | |
|
|
3360 | A haskell binding to libev is available at |
|
|
3361 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3362 | |
2900 | =item D |
3363 | =item D |
2901 | |
3364 | |
2902 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3365 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2903 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3366 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3367 | |
|
|
3368 | =item Ocaml |
|
|
3369 | |
|
|
3370 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3371 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
2904 | |
3372 | |
2905 | =back |
3373 | =back |
2906 | |
3374 | |
2907 | |
3375 | |
2908 | =head1 MACRO MAGIC |
3376 | =head1 MACRO MAGIC |
… | |
… | |
3009 | |
3477 | |
3010 | #define EV_STANDALONE 1 |
3478 | #define EV_STANDALONE 1 |
3011 | #include "ev.h" |
3479 | #include "ev.h" |
3012 | |
3480 | |
3013 | Both header files and implementation files can be compiled with a C++ |
3481 | Both header files and implementation files can be compiled with a C++ |
3014 | compiler (at least, thats a stated goal, and breakage will be treated |
3482 | compiler (at least, that's a stated goal, and breakage will be treated |
3015 | as a bug). |
3483 | as a bug). |
3016 | |
3484 | |
3017 | You need the following files in your source tree, or in a directory |
3485 | You need the following files in your source tree, or in a directory |
3018 | in your include path (e.g. in libev/ when using -Ilibev): |
3486 | in your include path (e.g. in libev/ when using -Ilibev): |
3019 | |
3487 | |
… | |
… | |
3075 | keeps libev from including F<config.h>, and it also defines dummy |
3543 | keeps libev from including F<config.h>, and it also defines dummy |
3076 | implementations for some libevent functions (such as logging, which is not |
3544 | implementations for some libevent functions (such as logging, which is not |
3077 | supported). It will also not define any of the structs usually found in |
3545 | supported). It will also not define any of the structs usually found in |
3078 | F<event.h> that are not directly supported by the libev core alone. |
3546 | F<event.h> that are not directly supported by the libev core alone. |
3079 | |
3547 | |
|
|
3548 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3549 | configuration, but has to be more conservative. |
|
|
3550 | |
3080 | =item EV_USE_MONOTONIC |
3551 | =item EV_USE_MONOTONIC |
3081 | |
3552 | |
3082 | If defined to be C<1>, libev will try to detect the availability of the |
3553 | If defined to be C<1>, libev will try to detect the availability of the |
3083 | monotonic clock option at both compile time and runtime. Otherwise no use |
3554 | monotonic clock option at both compile time and runtime. Otherwise no |
3084 | of the monotonic clock option will be attempted. If you enable this, you |
3555 | use of the monotonic clock option will be attempted. If you enable this, |
3085 | usually have to link against librt or something similar. Enabling it when |
3556 | you usually have to link against librt or something similar. Enabling it |
3086 | the functionality isn't available is safe, though, although you have |
3557 | when the functionality isn't available is safe, though, although you have |
3087 | to make sure you link against any libraries where the C<clock_gettime> |
3558 | to make sure you link against any libraries where the C<clock_gettime> |
3088 | function is hiding in (often F<-lrt>). |
3559 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3089 | |
3560 | |
3090 | =item EV_USE_REALTIME |
3561 | =item EV_USE_REALTIME |
3091 | |
3562 | |
3092 | If defined to be C<1>, libev will try to detect the availability of the |
3563 | If defined to be C<1>, libev will try to detect the availability of the |
3093 | real-time clock option at compile time (and assume its availability at |
3564 | real-time clock option at compile time (and assume its availability |
3094 | runtime if successful). Otherwise no use of the real-time clock option will |
3565 | at runtime if successful). Otherwise no use of the real-time clock |
3095 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3566 | option will be attempted. This effectively replaces C<gettimeofday> |
3096 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3567 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3097 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3568 | correctness. See the note about libraries in the description of |
|
|
3569 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3570 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3571 | |
|
|
3572 | =item EV_USE_CLOCK_SYSCALL |
|
|
3573 | |
|
|
3574 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3575 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3576 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3577 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3578 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3579 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3580 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3581 | higher, as it simplifies linking (no need for C<-lrt>). |
3098 | |
3582 | |
3099 | =item EV_USE_NANOSLEEP |
3583 | =item EV_USE_NANOSLEEP |
3100 | |
3584 | |
3101 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3585 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3102 | and will use it for delays. Otherwise it will use C<select ()>. |
3586 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3118 | |
3602 | |
3119 | =item EV_SELECT_USE_FD_SET |
3603 | =item EV_SELECT_USE_FD_SET |
3120 | |
3604 | |
3121 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3605 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3122 | structure. This is useful if libev doesn't compile due to a missing |
3606 | structure. This is useful if libev doesn't compile due to a missing |
3123 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3607 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3124 | exotic systems. This usually limits the range of file descriptors to some |
3608 | on exotic systems. This usually limits the range of file descriptors to |
3125 | low limit such as 1024 or might have other limitations (winsocket only |
3609 | some low limit such as 1024 or might have other limitations (winsocket |
3126 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3610 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3127 | influence the size of the C<fd_set> used. |
3611 | configures the maximum size of the C<fd_set>. |
3128 | |
3612 | |
3129 | =item EV_SELECT_IS_WINSOCKET |
3613 | =item EV_SELECT_IS_WINSOCKET |
3130 | |
3614 | |
3131 | When defined to C<1>, the select backend will assume that |
3615 | When defined to C<1>, the select backend will assume that |
3132 | select/socket/connect etc. don't understand file descriptors but |
3616 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3282 | defined to be C<0>, then they are not. |
3766 | defined to be C<0>, then they are not. |
3283 | |
3767 | |
3284 | =item EV_MINIMAL |
3768 | =item EV_MINIMAL |
3285 | |
3769 | |
3286 | If you need to shave off some kilobytes of code at the expense of some |
3770 | If you need to shave off some kilobytes of code at the expense of some |
3287 | speed, define this symbol to C<1>. Currently this is used to override some |
3771 | speed (but with the full API), define this symbol to C<1>. Currently this |
3288 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3772 | is used to override some inlining decisions, saves roughly 30% code size |
3289 | much smaller 2-heap for timer management over the default 4-heap. |
3773 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3774 | the default 4-heap. |
|
|
3775 | |
|
|
3776 | You can save even more by disabling watcher types you do not need |
|
|
3777 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3778 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3779 | |
|
|
3780 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3781 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3782 | of the API are still available, and do not complain if this subset changes |
|
|
3783 | over time. |
3290 | |
3784 | |
3291 | =item EV_PID_HASHSIZE |
3785 | =item EV_PID_HASHSIZE |
3292 | |
3786 | |
3293 | C<ev_child> watchers use a small hash table to distribute workload by |
3787 | C<ev_child> watchers use a small hash table to distribute workload by |
3294 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3788 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3480 | default loop and triggering an C<ev_async> watcher from the default loop |
3974 | default loop and triggering an C<ev_async> watcher from the default loop |
3481 | watcher callback into the event loop interested in the signal. |
3975 | watcher callback into the event loop interested in the signal. |
3482 | |
3976 | |
3483 | =back |
3977 | =back |
3484 | |
3978 | |
|
|
3979 | =head4 THREAD LOCKING EXAMPLE |
|
|
3980 | |
|
|
3981 | Here is a fictitious example of how to run an event loop in a different |
|
|
3982 | thread than where callbacks are being invoked and watchers are |
|
|
3983 | created/added/removed. |
|
|
3984 | |
|
|
3985 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3986 | which uses exactly this technique (which is suited for many high-level |
|
|
3987 | languages). |
|
|
3988 | |
|
|
3989 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3990 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3991 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3992 | |
|
|
3993 | First, you need to associate some data with the event loop: |
|
|
3994 | |
|
|
3995 | typedef struct { |
|
|
3996 | mutex_t lock; /* global loop lock */ |
|
|
3997 | ev_async async_w; |
|
|
3998 | thread_t tid; |
|
|
3999 | cond_t invoke_cv; |
|
|
4000 | } userdata; |
|
|
4001 | |
|
|
4002 | void prepare_loop (EV_P) |
|
|
4003 | { |
|
|
4004 | // for simplicity, we use a static userdata struct. |
|
|
4005 | static userdata u; |
|
|
4006 | |
|
|
4007 | ev_async_init (&u->async_w, async_cb); |
|
|
4008 | ev_async_start (EV_A_ &u->async_w); |
|
|
4009 | |
|
|
4010 | pthread_mutex_init (&u->lock, 0); |
|
|
4011 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4012 | |
|
|
4013 | // now associate this with the loop |
|
|
4014 | ev_set_userdata (EV_A_ u); |
|
|
4015 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4016 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4017 | |
|
|
4018 | // then create the thread running ev_loop |
|
|
4019 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4020 | } |
|
|
4021 | |
|
|
4022 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4023 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4024 | that might have been added: |
|
|
4025 | |
|
|
4026 | static void |
|
|
4027 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4028 | { |
|
|
4029 | // just used for the side effects |
|
|
4030 | } |
|
|
4031 | |
|
|
4032 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4033 | protecting the loop data, respectively. |
|
|
4034 | |
|
|
4035 | static void |
|
|
4036 | l_release (EV_P) |
|
|
4037 | { |
|
|
4038 | userdata *u = ev_userdata (EV_A); |
|
|
4039 | pthread_mutex_unlock (&u->lock); |
|
|
4040 | } |
|
|
4041 | |
|
|
4042 | static void |
|
|
4043 | l_acquire (EV_P) |
|
|
4044 | { |
|
|
4045 | userdata *u = ev_userdata (EV_A); |
|
|
4046 | pthread_mutex_lock (&u->lock); |
|
|
4047 | } |
|
|
4048 | |
|
|
4049 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4050 | into C<ev_loop>: |
|
|
4051 | |
|
|
4052 | void * |
|
|
4053 | l_run (void *thr_arg) |
|
|
4054 | { |
|
|
4055 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4056 | |
|
|
4057 | l_acquire (EV_A); |
|
|
4058 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4059 | ev_loop (EV_A_ 0); |
|
|
4060 | l_release (EV_A); |
|
|
4061 | |
|
|
4062 | return 0; |
|
|
4063 | } |
|
|
4064 | |
|
|
4065 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4066 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4067 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4068 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4069 | and b) skipping inter-thread-communication when there are no pending |
|
|
4070 | watchers is very beneficial): |
|
|
4071 | |
|
|
4072 | static void |
|
|
4073 | l_invoke (EV_P) |
|
|
4074 | { |
|
|
4075 | userdata *u = ev_userdata (EV_A); |
|
|
4076 | |
|
|
4077 | while (ev_pending_count (EV_A)) |
|
|
4078 | { |
|
|
4079 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4080 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4081 | } |
|
|
4082 | } |
|
|
4083 | |
|
|
4084 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4085 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4086 | thread to continue: |
|
|
4087 | |
|
|
4088 | static void |
|
|
4089 | real_invoke_pending (EV_P) |
|
|
4090 | { |
|
|
4091 | userdata *u = ev_userdata (EV_A); |
|
|
4092 | |
|
|
4093 | pthread_mutex_lock (&u->lock); |
|
|
4094 | ev_invoke_pending (EV_A); |
|
|
4095 | pthread_cond_signal (&u->invoke_cv); |
|
|
4096 | pthread_mutex_unlock (&u->lock); |
|
|
4097 | } |
|
|
4098 | |
|
|
4099 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4100 | event loop, you will now have to lock: |
|
|
4101 | |
|
|
4102 | ev_timer timeout_watcher; |
|
|
4103 | userdata *u = ev_userdata (EV_A); |
|
|
4104 | |
|
|
4105 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4106 | |
|
|
4107 | pthread_mutex_lock (&u->lock); |
|
|
4108 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4109 | ev_async_send (EV_A_ &u->async_w); |
|
|
4110 | pthread_mutex_unlock (&u->lock); |
|
|
4111 | |
|
|
4112 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4113 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4114 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4115 | watchers in the next event loop iteration. |
|
|
4116 | |
3485 | =head3 COROUTINES |
4117 | =head3 COROUTINES |
3486 | |
4118 | |
3487 | Libev is very accommodating to coroutines ("cooperative threads"): |
4119 | Libev is very accommodating to coroutines ("cooperative threads"): |
3488 | libev fully supports nesting calls to its functions from different |
4120 | libev fully supports nesting calls to its functions from different |
3489 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4121 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3490 | different coroutines, and switch freely between both coroutines running the |
4122 | different coroutines, and switch freely between both coroutines running |
3491 | loop, as long as you don't confuse yourself). The only exception is that |
4123 | the loop, as long as you don't confuse yourself). The only exception is |
3492 | you must not do this from C<ev_periodic> reschedule callbacks. |
4124 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3493 | |
4125 | |
3494 | Care has been taken to ensure that libev does not keep local state inside |
4126 | Care has been taken to ensure that libev does not keep local state inside |
3495 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4127 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3496 | they do not clal any callbacks. |
4128 | they do not call any callbacks. |
3497 | |
4129 | |
3498 | =head2 COMPILER WARNINGS |
4130 | =head2 COMPILER WARNINGS |
3499 | |
4131 | |
3500 | Depending on your compiler and compiler settings, you might get no or a |
4132 | Depending on your compiler and compiler settings, you might get no or a |
3501 | lot of warnings when compiling libev code. Some people are apparently |
4133 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3535 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4167 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3536 | ==2274== possibly lost: 0 bytes in 0 blocks. |
4168 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3537 | ==2274== still reachable: 256 bytes in 1 blocks. |
4169 | ==2274== still reachable: 256 bytes in 1 blocks. |
3538 | |
4170 | |
3539 | Then there is no memory leak, just as memory accounted to global variables |
4171 | Then there is no memory leak, just as memory accounted to global variables |
3540 | is not a memleak - the memory is still being refernced, and didn't leak. |
4172 | is not a memleak - the memory is still being referenced, and didn't leak. |
3541 | |
4173 | |
3542 | Similarly, under some circumstances, valgrind might report kernel bugs |
4174 | Similarly, under some circumstances, valgrind might report kernel bugs |
3543 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
4175 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3544 | although an acceptable workaround has been found here), or it might be |
4176 | although an acceptable workaround has been found here), or it might be |
3545 | confused. |
4177 | confused. |
… | |
… | |
3574 | way (note also that glib is the slowest event library known to man). |
4206 | way (note also that glib is the slowest event library known to man). |
3575 | |
4207 | |
3576 | There is no supported compilation method available on windows except |
4208 | There is no supported compilation method available on windows except |
3577 | embedding it into other applications. |
4209 | embedding it into other applications. |
3578 | |
4210 | |
|
|
4211 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4212 | tries its best, but under most conditions, signals will simply not work. |
|
|
4213 | |
3579 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4214 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3580 | accept large writes: instead of resulting in a partial write, windows will |
4215 | accept large writes: instead of resulting in a partial write, windows will |
3581 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4216 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3582 | so make sure you only write small amounts into your sockets (less than a |
4217 | so make sure you only write small amounts into your sockets (less than a |
3583 | megabyte seems safe, but this apparently depends on the amount of memory |
4218 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3587 | the abysmal performance of winsockets, using a large number of sockets |
4222 | the abysmal performance of winsockets, using a large number of sockets |
3588 | is not recommended (and not reasonable). If your program needs to use |
4223 | is not recommended (and not reasonable). If your program needs to use |
3589 | more than a hundred or so sockets, then likely it needs to use a totally |
4224 | more than a hundred or so sockets, then likely it needs to use a totally |
3590 | different implementation for windows, as libev offers the POSIX readiness |
4225 | different implementation for windows, as libev offers the POSIX readiness |
3591 | notification model, which cannot be implemented efficiently on windows |
4226 | notification model, which cannot be implemented efficiently on windows |
3592 | (Microsoft monopoly games). |
4227 | (due to Microsoft monopoly games). |
3593 | |
4228 | |
3594 | A typical way to use libev under windows is to embed it (see the embedding |
4229 | A typical way to use libev under windows is to embed it (see the embedding |
3595 | section for details) and use the following F<evwrap.h> header file instead |
4230 | section for details) and use the following F<evwrap.h> header file instead |
3596 | of F<ev.h>: |
4231 | of F<ev.h>: |
3597 | |
4232 | |
… | |
… | |
3633 | |
4268 | |
3634 | Early versions of winsocket's select only supported waiting for a maximum |
4269 | Early versions of winsocket's select only supported waiting for a maximum |
3635 | of C<64> handles (probably owning to the fact that all windows kernels |
4270 | of C<64> handles (probably owning to the fact that all windows kernels |
3636 | can only wait for C<64> things at the same time internally; Microsoft |
4271 | can only wait for C<64> things at the same time internally; Microsoft |
3637 | recommends spawning a chain of threads and wait for 63 handles and the |
4272 | recommends spawning a chain of threads and wait for 63 handles and the |
3638 | previous thread in each. Great). |
4273 | previous thread in each. Sounds great!). |
3639 | |
4274 | |
3640 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4275 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3641 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4276 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3642 | call (which might be in libev or elsewhere, for example, perl does its own |
4277 | call (which might be in libev or elsewhere, for example, perl and many |
3643 | select emulation on windows). |
4278 | other interpreters do their own select emulation on windows). |
3644 | |
4279 | |
3645 | Another limit is the number of file descriptors in the Microsoft runtime |
4280 | Another limit is the number of file descriptors in the Microsoft runtime |
3646 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4281 | libraries, which by default is C<64> (there must be a hidden I<64> |
3647 | or something like this inside Microsoft). You can increase this by calling |
4282 | fetish or something like this inside Microsoft). You can increase this |
3648 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4283 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3649 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4284 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3650 | libraries. |
|
|
3651 | |
|
|
3652 | This might get you to about C<512> or C<2048> sockets (depending on |
4285 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3653 | windows version and/or the phase of the moon). To get more, you need to |
4286 | (depending on windows version and/or the phase of the moon). To get more, |
3654 | wrap all I/O functions and provide your own fd management, but the cost of |
4287 | you need to wrap all I/O functions and provide your own fd management, but |
3655 | calling select (O(n²)) will likely make this unworkable. |
4288 | the cost of calling select (O(n²)) will likely make this unworkable. |
3656 | |
4289 | |
3657 | =back |
4290 | =back |
3658 | |
4291 | |
3659 | =head2 PORTABILITY REQUIREMENTS |
4292 | =head2 PORTABILITY REQUIREMENTS |
3660 | |
4293 | |
… | |
… | |
3703 | =item C<double> must hold a time value in seconds with enough accuracy |
4336 | =item C<double> must hold a time value in seconds with enough accuracy |
3704 | |
4337 | |
3705 | The type C<double> is used to represent timestamps. It is required to |
4338 | The type C<double> is used to represent timestamps. It is required to |
3706 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4339 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3707 | enough for at least into the year 4000. This requirement is fulfilled by |
4340 | enough for at least into the year 4000. This requirement is fulfilled by |
3708 | implementations implementing IEEE 754 (basically all existing ones). |
4341 | implementations implementing IEEE 754, which is basically all existing |
|
|
4342 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4343 | 2200. |
3709 | |
4344 | |
3710 | =back |
4345 | =back |
3711 | |
4346 | |
3712 | If you know of other additional requirements drop me a note. |
4347 | If you know of other additional requirements drop me a note. |
3713 | |
4348 | |
… | |
… | |
3781 | involves iterating over all running async watchers or all signal numbers. |
4416 | involves iterating over all running async watchers or all signal numbers. |
3782 | |
4417 | |
3783 | =back |
4418 | =back |
3784 | |
4419 | |
3785 | |
4420 | |
|
|
4421 | =head1 GLOSSARY |
|
|
4422 | |
|
|
4423 | =over 4 |
|
|
4424 | |
|
|
4425 | =item active |
|
|
4426 | |
|
|
4427 | A watcher is active as long as it has been started (has been attached to |
|
|
4428 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4429 | |
|
|
4430 | =item application |
|
|
4431 | |
|
|
4432 | In this document, an application is whatever is using libev. |
|
|
4433 | |
|
|
4434 | =item callback |
|
|
4435 | |
|
|
4436 | The address of a function that is called when some event has been |
|
|
4437 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4438 | received the event, and the actual event bitset. |
|
|
4439 | |
|
|
4440 | =item callback invocation |
|
|
4441 | |
|
|
4442 | The act of calling the callback associated with a watcher. |
|
|
4443 | |
|
|
4444 | =item event |
|
|
4445 | |
|
|
4446 | A change of state of some external event, such as data now being available |
|
|
4447 | for reading on a file descriptor, time having passed or simply not having |
|
|
4448 | any other events happening anymore. |
|
|
4449 | |
|
|
4450 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4451 | C<EV_TIMEOUT>). |
|
|
4452 | |
|
|
4453 | =item event library |
|
|
4454 | |
|
|
4455 | A software package implementing an event model and loop. |
|
|
4456 | |
|
|
4457 | =item event loop |
|
|
4458 | |
|
|
4459 | An entity that handles and processes external events and converts them |
|
|
4460 | into callback invocations. |
|
|
4461 | |
|
|
4462 | =item event model |
|
|
4463 | |
|
|
4464 | The model used to describe how an event loop handles and processes |
|
|
4465 | watchers and events. |
|
|
4466 | |
|
|
4467 | =item pending |
|
|
4468 | |
|
|
4469 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4470 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4471 | pending status is explicitly cleared by the application. |
|
|
4472 | |
|
|
4473 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4474 | its pending status. |
|
|
4475 | |
|
|
4476 | =item real time |
|
|
4477 | |
|
|
4478 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4479 | |
|
|
4480 | =item wall-clock time |
|
|
4481 | |
|
|
4482 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4483 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4484 | clock. |
|
|
4485 | |
|
|
4486 | =item watcher |
|
|
4487 | |
|
|
4488 | A data structure that describes interest in certain events. Watchers need |
|
|
4489 | to be started (attached to an event loop) before they can receive events. |
|
|
4490 | |
|
|
4491 | =item watcher invocation |
|
|
4492 | |
|
|
4493 | The act of calling the callback associated with a watcher. |
|
|
4494 | |
|
|
4495 | =back |
|
|
4496 | |
3786 | =head1 AUTHOR |
4497 | =head1 AUTHOR |
3787 | |
4498 | |
3788 | Marc Lehmann <libev@schmorp.de>. |
4499 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3789 | |
4500 | |