… | |
… | |
58 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
59 | |
59 | |
60 | // now wait for events to arrive |
60 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // break was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 ABOUT THIS DOCUMENT |
67 | =head1 ABOUT THIS DOCUMENT |
68 | |
68 | |
… | |
… | |
178 | you actually want to know. Also interesting is the combination of |
178 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
179 | C<ev_update_now> and C<ev_now>. |
180 | |
180 | |
181 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
182 | |
182 | |
183 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
184 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
|
|
185 | passed (approximately - it might return a bit earlier even if not |
|
|
186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
|
|
187 | |
185 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
|
|
189 | |
|
|
190 | The range of the C<interval> is limited - libev only guarantees to work |
|
|
191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
186 | |
192 | |
187 | =item int ev_version_major () |
193 | =item int ev_version_major () |
188 | |
194 | |
189 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
190 | |
196 | |
… | |
… | |
483 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
484 | |
490 | |
485 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
486 | kernels). |
492 | kernels). |
487 | |
493 | |
488 | For few fds, this backend is a bit little slower than poll and select, |
494 | For few fds, this backend is a bit little slower than poll and select, but |
489 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
490 | like O(total_fds) where n is the total number of fds (or the highest fd), |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
491 | epoll scales either O(1) or O(active_fds). |
497 | fd), epoll scales either O(1) or O(active_fds). |
492 | |
498 | |
493 | The epoll mechanism deserves honorable mention as the most misdesigned |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
494 | of the more advanced event mechanisms: mere annoyances include silently |
500 | of the more advanced event mechanisms: mere annoyances include silently |
495 | dropping file descriptors, requiring a system call per change per file |
501 | dropping file descriptors, requiring a system call per change per file |
496 | descriptor (and unnecessary guessing of parameters), problems with dup, |
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
… | |
… | |
499 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
505 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
500 | forks then I<both> parent and child process have to recreate the epoll |
506 | forks then I<both> parent and child process have to recreate the epoll |
501 | set, which can take considerable time (one syscall per file descriptor) |
507 | set, which can take considerable time (one syscall per file descriptor) |
502 | and is of course hard to detect. |
508 | and is of course hard to detect. |
503 | |
509 | |
504 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
505 | of course I<doesn't>, and epoll just loves to report events for totally |
511 | but of course I<doesn't>, and epoll just loves to report events for |
506 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
507 | even remove them from the set) than registered in the set (especially |
513 | one cannot even remove them from the set) than registered in the set |
508 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
509 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
510 | events to filter out spurious ones, recreating the set when required. Last |
516 | that against the events to filter out spurious ones, recreating the set |
|
|
517 | when required. Epoll also errornously rounds down timeouts, but gives you |
|
|
518 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
519 | because epoll returns immediately despite a nonzero timeout. And last |
511 | not least, it also refuses to work with some file descriptors which work |
520 | not least, it also refuses to work with some file descriptors which work |
512 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
513 | |
522 | |
514 | Epoll is truly the train wreck analog among event poll mechanisms, |
523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
515 | a frankenpoll, cobbled together in a hurry, no thought to design or |
524 | cobbled together in a hurry, no thought to design or interaction with |
516 | interaction with others. |
525 | others. Oh, the pain, will it ever stop... |
517 | |
526 | |
518 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | While stopping, setting and starting an I/O watcher in the same iteration |
519 | will result in some caching, there is still a system call per such |
528 | will result in some caching, there is still a system call per such |
520 | incident (because the same I<file descriptor> could point to a different |
529 | incident (because the same I<file descriptor> could point to a different |
521 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
825 | This is useful if you are waiting for some external event in conjunction |
834 | This is useful if you are waiting for some external event in conjunction |
826 | with something not expressible using other libev watchers (i.e. "roll your |
835 | with something not expressible using other libev watchers (i.e. "roll your |
827 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
836 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
828 | usually a better approach for this kind of thing. |
837 | usually a better approach for this kind of thing. |
829 | |
838 | |
830 | Here are the gory details of what C<ev_run> does: |
839 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
840 | understanding, not a guarantee that things will work exactly like this in |
|
|
841 | future versions): |
831 | |
842 | |
832 | - Increment loop depth. |
843 | - Increment loop depth. |
833 | - Reset the ev_break status. |
844 | - Reset the ev_break status. |
834 | - Before the first iteration, call any pending watchers. |
845 | - Before the first iteration, call any pending watchers. |
835 | LOOP: |
846 | LOOP: |
… | |
… | |
868 | anymore. |
879 | anymore. |
869 | |
880 | |
870 | ... queue jobs here, make sure they register event watchers as long |
881 | ... queue jobs here, make sure they register event watchers as long |
871 | ... as they still have work to do (even an idle watcher will do..) |
882 | ... as they still have work to do (even an idle watcher will do..) |
872 | ev_run (my_loop, 0); |
883 | ev_run (my_loop, 0); |
873 | ... jobs done or somebody called unloop. yeah! |
884 | ... jobs done or somebody called break. yeah! |
874 | |
885 | |
875 | =item ev_break (loop, how) |
886 | =item ev_break (loop, how) |
876 | |
887 | |
877 | Can be used to make a call to C<ev_run> return early (but only after it |
888 | Can be used to make a call to C<ev_run> return early (but only after it |
878 | has processed all outstanding events). The C<how> argument must be either |
889 | has processed all outstanding events). The C<how> argument must be either |
… | |
… | |
2151 | |
2162 | |
2152 | Another way to think about it (for the mathematically inclined) is that |
2163 | Another way to think about it (for the mathematically inclined) is that |
2153 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2164 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2154 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2165 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2155 | |
2166 | |
2156 | For numerical stability it is preferable that the C<offset> value is near |
2167 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2157 | C<ev_now ()> (the current time), but there is no range requirement for |
2168 | interval value should be higher than C<1/8192> (which is around 100 |
2158 | this value, and in fact is often specified as zero. |
2169 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2170 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2171 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2172 | C<0> and C<interval>, which is also the recommended range. |
2159 | |
2173 | |
2160 | Note also that there is an upper limit to how often a timer can fire (CPU |
2174 | Note also that there is an upper limit to how often a timer can fire (CPU |
2161 | speed for example), so if C<interval> is very small then timing stability |
2175 | speed for example), so if C<interval> is very small then timing stability |
2162 | will of course deteriorate. Libev itself tries to be exact to be about one |
2176 | will of course deteriorate. Libev itself tries to be exact to be about one |
2163 | millisecond (if the OS supports it and the machine is fast enough). |
2177 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
3188 | atexit (program_exits); |
3202 | atexit (program_exits); |
3189 | |
3203 | |
3190 | |
3204 | |
3191 | =head2 C<ev_async> - how to wake up an event loop |
3205 | =head2 C<ev_async> - how to wake up an event loop |
3192 | |
3206 | |
3193 | In general, you cannot use an C<ev_run> from multiple threads or other |
3207 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3194 | asynchronous sources such as signal handlers (as opposed to multiple event |
3208 | asynchronous sources such as signal handlers (as opposed to multiple event |
3195 | loops - those are of course safe to use in different threads). |
3209 | loops - those are of course safe to use in different threads). |
3196 | |
3210 | |
3197 | Sometimes, however, you need to wake up an event loop you do not control, |
3211 | Sometimes, however, you need to wake up an event loop you do not control, |
3198 | for example because it belongs to another thread. This is what C<ev_async> |
3212 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3308 | trust me. |
3322 | trust me. |
3309 | |
3323 | |
3310 | =item ev_async_send (loop, ev_async *) |
3324 | =item ev_async_send (loop, ev_async *) |
3311 | |
3325 | |
3312 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3326 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3313 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3327 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3328 | returns. |
|
|
3329 | |
3314 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3330 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3315 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3331 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3316 | section below on what exactly this means). |
3332 | embedding section below on what exactly this means). |
3317 | |
3333 | |
3318 | Note that, as with other watchers in libev, multiple events might get |
3334 | Note that, as with other watchers in libev, multiple events might get |
3319 | compressed into a single callback invocation (another way to look at this |
3335 | compressed into a single callback invocation (another way to look at this |
3320 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3336 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3321 | reset when the event loop detects that). |
3337 | reset when the event loop detects that). |
… | |
… | |
3547 | // now associate this with the loop |
3563 | // now associate this with the loop |
3548 | ev_set_userdata (EV_A_ u); |
3564 | ev_set_userdata (EV_A_ u); |
3549 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3565 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3550 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3566 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3551 | |
3567 | |
3552 | // then create the thread running ev_loop |
3568 | // then create the thread running ev_run |
3553 | pthread_create (&u->tid, 0, l_run, EV_A); |
3569 | pthread_create (&u->tid, 0, l_run, EV_A); |
3554 | } |
3570 | } |
3555 | |
3571 | |
3556 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3572 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3557 | solely to wake up the event loop so it takes notice of any new watchers |
3573 | solely to wake up the event loop so it takes notice of any new watchers |
… | |
… | |
4202 | F<event.h> that are not directly supported by the libev core alone. |
4218 | F<event.h> that are not directly supported by the libev core alone. |
4203 | |
4219 | |
4204 | In standalone mode, libev will still try to automatically deduce the |
4220 | In standalone mode, libev will still try to automatically deduce the |
4205 | configuration, but has to be more conservative. |
4221 | configuration, but has to be more conservative. |
4206 | |
4222 | |
|
|
4223 | =item EV_USE_FLOOR |
|
|
4224 | |
|
|
4225 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4226 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4227 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4228 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4229 | function is not available will fail, so the safe default is to not enable |
|
|
4230 | this. |
|
|
4231 | |
4207 | =item EV_USE_MONOTONIC |
4232 | =item EV_USE_MONOTONIC |
4208 | |
4233 | |
4209 | If defined to be C<1>, libev will try to detect the availability of the |
4234 | If defined to be C<1>, libev will try to detect the availability of the |
4210 | monotonic clock option at both compile time and runtime. Otherwise no |
4235 | monotonic clock option at both compile time and runtime. Otherwise no |
4211 | use of the monotonic clock option will be attempted. If you enable this, |
4236 | use of the monotonic clock option will be attempted. If you enable this, |
… | |
… | |
5222 | The physical time that is observed. It is apparently strictly monotonic :) |
5247 | The physical time that is observed. It is apparently strictly monotonic :) |
5223 | |
5248 | |
5224 | =item wall-clock time |
5249 | =item wall-clock time |
5225 | |
5250 | |
5226 | The time and date as shown on clocks. Unlike real time, it can actually |
5251 | The time and date as shown on clocks. Unlike real time, it can actually |
5227 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5252 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5228 | clock. |
5253 | clock. |
5229 | |
5254 | |
5230 | =item watcher |
5255 | =item watcher |
5231 | |
5256 | |
5232 | A data structure that describes interest in certain events. Watchers need |
5257 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5235 | =back |
5260 | =back |
5236 | |
5261 | |
5237 | =head1 AUTHOR |
5262 | =head1 AUTHOR |
5238 | |
5263 | |
5239 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5264 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5240 | Magnusson and Emanuele Giaquinta. |
5265 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5241 | |
5266 | |