… | |
… | |
118 | Libev is very configurable. In this manual the default (and most common) |
118 | Libev is very configurable. In this manual the default (and most common) |
119 | configuration will be described, which supports multiple event loops. For |
119 | configuration will be described, which supports multiple event loops. For |
120 | more info about various configuration options please have a look at |
120 | more info about various configuration options please have a look at |
121 | B<EMBED> section in this manual. If libev was configured without support |
121 | B<EMBED> section in this manual. If libev was configured without support |
122 | for multiple event loops, then all functions taking an initial argument of |
122 | for multiple event loops, then all functions taking an initial argument of |
123 | name C<loop> (which is always of type C<ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
124 | this argument. |
124 | this argument. |
125 | |
125 | |
126 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
127 | |
127 | |
128 | Libev represents time as a single floating point number, representing |
128 | Libev represents time as a single floating point number, representing |
… | |
… | |
345 | useful to try out specific backends to test their performance, or to work |
345 | useful to try out specific backends to test their performance, or to work |
346 | around bugs. |
346 | around bugs. |
347 | |
347 | |
348 | =item C<EVFLAG_FORKCHECK> |
348 | =item C<EVFLAG_FORKCHECK> |
349 | |
349 | |
350 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
350 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
351 | a fork, you can also make libev check for a fork in each iteration by |
351 | make libev check for a fork in each iteration by enabling this flag. |
352 | enabling this flag. |
|
|
353 | |
352 | |
354 | This works by calling C<getpid ()> on every iteration of the loop, |
353 | This works by calling C<getpid ()> on every iteration of the loop, |
355 | and thus this might slow down your event loop if you do a lot of loop |
354 | and thus this might slow down your event loop if you do a lot of loop |
356 | iterations and little real work, but is usually not noticeable (on my |
355 | iterations and little real work, but is usually not noticeable (on my |
357 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
356 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
… | |
370 | When this flag is specified, then libev will not attempt to use the |
369 | When this flag is specified, then libev will not attempt to use the |
371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
370 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
372 | testing, this flag can be useful to conserve inotify file descriptors, as |
371 | testing, this flag can be useful to conserve inotify file descriptors, as |
373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
372 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
374 | |
373 | |
375 | =item C<EVFLAG_NOSIGNALFD> |
374 | =item C<EVFLAG_SIGNALFD> |
376 | |
375 | |
377 | When this flag is specified, then libev will not attempt to use the |
376 | When this flag is specified, then libev will attempt to use the |
378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is |
377 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
379 | probably only useful to work around any bugs in libev. Consequently, this |
378 | delivers signals synchronously, which makes it both faster and might make |
380 | flag might go away once the signalfd functionality is considered stable, |
379 | it possible to get the queued signal data. It can also simplify signal |
381 | so it's useful mostly in environment variables and not in program code. |
380 | handling with threads, as long as you properly block signals in your |
|
|
381 | threads that are not interested in handling them. |
|
|
382 | |
|
|
383 | Signalfd will not be used by default as this changes your signal mask, and |
|
|
384 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
|
385 | example) that can't properly initialise their signal masks. |
382 | |
386 | |
383 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
387 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
384 | |
388 | |
385 | This is your standard select(2) backend. Not I<completely> standard, as |
389 | This is your standard select(2) backend. Not I<completely> standard, as |
386 | libev tries to roll its own fd_set with no limits on the number of fds, |
390 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
410 | |
414 | |
411 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
415 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
412 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
416 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
413 | |
417 | |
414 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
418 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
|
|
419 | |
|
|
420 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
421 | kernels). |
415 | |
422 | |
416 | For few fds, this backend is a bit little slower than poll and select, |
423 | For few fds, this backend is a bit little slower than poll and select, |
417 | but it scales phenomenally better. While poll and select usually scale |
424 | but it scales phenomenally better. While poll and select usually scale |
418 | like O(total_fds) where n is the total number of fds (or the highest fd), |
425 | like O(total_fds) where n is the total number of fds (or the highest fd), |
419 | epoll scales either O(1) or O(active_fds). |
426 | epoll scales either O(1) or O(active_fds). |
… | |
… | |
559 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
566 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
560 | |
567 | |
561 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
568 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
562 | |
569 | |
563 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
570 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
564 | always distinct from the default loop. Unlike the default loop, it cannot |
571 | always distinct from the default loop. |
565 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
566 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
567 | |
572 | |
568 | Note that this function I<is> thread-safe, and the recommended way to use |
573 | Note that this function I<is> thread-safe, and one common way to use |
569 | libev with threads is indeed to create one loop per thread, and using the |
574 | libev with threads is indeed to create one loop per thread, and using the |
570 | default loop in the "main" or "initial" thread. |
575 | default loop in the "main" or "initial" thread. |
571 | |
576 | |
572 | Example: Try to create a event loop that uses epoll and nothing else. |
577 | Example: Try to create a event loop that uses epoll and nothing else. |
573 | |
578 | |
… | |
… | |
575 | if (!epoller) |
580 | if (!epoller) |
576 | fatal ("no epoll found here, maybe it hides under your chair"); |
581 | fatal ("no epoll found here, maybe it hides under your chair"); |
577 | |
582 | |
578 | =item ev_default_destroy () |
583 | =item ev_default_destroy () |
579 | |
584 | |
580 | Destroys the default loop again (frees all memory and kernel state |
585 | Destroys the default loop (frees all memory and kernel state etc.). None |
581 | etc.). None of the active event watchers will be stopped in the normal |
586 | of the active event watchers will be stopped in the normal sense, so |
582 | sense, so e.g. C<ev_is_active> might still return true. It is your |
587 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
583 | responsibility to either stop all watchers cleanly yourself I<before> |
588 | either stop all watchers cleanly yourself I<before> calling this function, |
584 | calling this function, or cope with the fact afterwards (which is usually |
589 | or cope with the fact afterwards (which is usually the easiest thing, you |
585 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
590 | can just ignore the watchers and/or C<free ()> them for example). |
586 | for example). |
|
|
587 | |
591 | |
588 | Note that certain global state, such as signal state (and installed signal |
592 | Note that certain global state, such as signal state (and installed signal |
589 | handlers), will not be freed by this function, and related watchers (such |
593 | handlers), will not be freed by this function, and related watchers (such |
590 | as signal and child watchers) would need to be stopped manually. |
594 | as signal and child watchers) would need to be stopped manually. |
591 | |
595 | |
592 | In general it is not advisable to call this function except in the |
596 | In general it is not advisable to call this function except in the |
593 | rare occasion where you really need to free e.g. the signal handling |
597 | rare occasion where you really need to free e.g. the signal handling |
594 | pipe fds. If you need dynamically allocated loops it is better to use |
598 | pipe fds. If you need dynamically allocated loops it is better to use |
595 | C<ev_loop_new> and C<ev_loop_destroy>). |
599 | C<ev_loop_new> and C<ev_loop_destroy>. |
596 | |
600 | |
597 | =item ev_loop_destroy (loop) |
601 | =item ev_loop_destroy (loop) |
598 | |
602 | |
599 | Like C<ev_default_destroy>, but destroys an event loop created by an |
603 | Like C<ev_default_destroy>, but destroys an event loop created by an |
600 | earlier call to C<ev_loop_new>. |
604 | earlier call to C<ev_loop_new>. |
… | |
… | |
606 | name, you can call it anytime, but it makes most sense after forking, in |
610 | name, you can call it anytime, but it makes most sense after forking, in |
607 | the child process (or both child and parent, but that again makes little |
611 | the child process (or both child and parent, but that again makes little |
608 | sense). You I<must> call it in the child before using any of the libev |
612 | sense). You I<must> call it in the child before using any of the libev |
609 | functions, and it will only take effect at the next C<ev_loop> iteration. |
613 | functions, and it will only take effect at the next C<ev_loop> iteration. |
610 | |
614 | |
|
|
615 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
616 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
617 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
618 | during fork. |
|
|
619 | |
611 | On the other hand, you only need to call this function in the child |
620 | On the other hand, you only need to call this function in the child |
612 | process if and only if you want to use the event library in the child. If |
621 | process if and only if you want to use the event loop in the child. If you |
613 | you just fork+exec, you don't have to call it at all. |
622 | just fork+exec or create a new loop in the child, you don't have to call |
|
|
623 | it at all. |
614 | |
624 | |
615 | The function itself is quite fast and it's usually not a problem to call |
625 | The function itself is quite fast and it's usually not a problem to call |
616 | it just in case after a fork. To make this easy, the function will fit in |
626 | it just in case after a fork. To make this easy, the function will fit in |
617 | quite nicely into a call to C<pthread_atfork>: |
627 | quite nicely into a call to C<pthread_atfork>: |
618 | |
628 | |
… | |
… | |
620 | |
630 | |
621 | =item ev_loop_fork (loop) |
631 | =item ev_loop_fork (loop) |
622 | |
632 | |
623 | Like C<ev_default_fork>, but acts on an event loop created by |
633 | Like C<ev_default_fork>, but acts on an event loop created by |
624 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
634 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
625 | after fork that you want to re-use in the child, and how you do this is |
635 | after fork that you want to re-use in the child, and how you keep track of |
626 | entirely your own problem. |
636 | them is entirely your own problem. |
627 | |
637 | |
628 | =item int ev_is_default_loop (loop) |
638 | =item int ev_is_default_loop (loop) |
629 | |
639 | |
630 | Returns true when the given loop is, in fact, the default loop, and false |
640 | Returns true when the given loop is, in fact, the default loop, and false |
631 | otherwise. |
641 | otherwise. |
632 | |
642 | |
633 | =item unsigned int ev_loop_count (loop) |
643 | =item unsigned int ev_iteration (loop) |
634 | |
644 | |
635 | Returns the count of loop iterations for the loop, which is identical to |
645 | Returns the current iteration count for the loop, which is identical to |
636 | the number of times libev did poll for new events. It starts at C<0> and |
646 | the number of times libev did poll for new events. It starts at C<0> and |
637 | happily wraps around with enough iterations. |
647 | happily wraps around with enough iterations. |
638 | |
648 | |
639 | This value can sometimes be useful as a generation counter of sorts (it |
649 | This value can sometimes be useful as a generation counter of sorts (it |
640 | "ticks" the number of loop iterations), as it roughly corresponds with |
650 | "ticks" the number of loop iterations), as it roughly corresponds with |
641 | C<ev_prepare> and C<ev_check> calls. |
651 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
652 | prepare and check phases. |
642 | |
653 | |
643 | =item unsigned int ev_loop_depth (loop) |
654 | =item unsigned int ev_depth (loop) |
644 | |
655 | |
645 | Returns the number of times C<ev_loop> was entered minus the number of |
656 | Returns the number of times C<ev_loop> was entered minus the number of |
646 | times C<ev_loop> was exited, in other words, the recursion depth. |
657 | times C<ev_loop> was exited, in other words, the recursion depth. |
647 | |
658 | |
648 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
659 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
649 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
660 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
650 | in which case it is higher. |
661 | in which case it is higher. |
651 | |
662 | |
652 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
663 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
653 | etc.), doesn't count as exit. |
664 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
|
|
665 | ungentleman behaviour unless it's really convenient. |
654 | |
666 | |
655 | =item unsigned int ev_backend (loop) |
667 | =item unsigned int ev_backend (loop) |
656 | |
668 | |
657 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
669 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
658 | use. |
670 | use. |
… | |
… | |
789 | |
801 | |
790 | Ref/unref can be used to add or remove a reference count on the event |
802 | Ref/unref can be used to add or remove a reference count on the event |
791 | loop: Every watcher keeps one reference, and as long as the reference |
803 | loop: Every watcher keeps one reference, and as long as the reference |
792 | count is nonzero, C<ev_loop> will not return on its own. |
804 | count is nonzero, C<ev_loop> will not return on its own. |
793 | |
805 | |
794 | If you have a watcher you never unregister that should not keep C<ev_loop> |
806 | This is useful when you have a watcher that you never intend to |
795 | from returning, call ev_unref() after starting, and ev_ref() before |
807 | unregister, but that nevertheless should not keep C<ev_loop> from |
|
|
808 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
796 | stopping it. |
809 | before stopping it. |
797 | |
810 | |
798 | As an example, libev itself uses this for its internal signal pipe: It |
811 | As an example, libev itself uses this for its internal signal pipe: It |
799 | is not visible to the libev user and should not keep C<ev_loop> from |
812 | is not visible to the libev user and should not keep C<ev_loop> from |
800 | exiting if no event watchers registered by it are active. It is also an |
813 | exiting if no event watchers registered by it are active. It is also an |
801 | excellent way to do this for generic recurring timers or from within |
814 | excellent way to do this for generic recurring timers or from within |
… | |
… | |
916 | |
929 | |
917 | While event loop modifications are allowed between invocations of |
930 | While event loop modifications are allowed between invocations of |
918 | C<release> and C<acquire> (that's their only purpose after all), no |
931 | C<release> and C<acquire> (that's their only purpose after all), no |
919 | modifications done will affect the event loop, i.e. adding watchers will |
932 | modifications done will affect the event loop, i.e. adding watchers will |
920 | have no effect on the set of file descriptors being watched, or the time |
933 | have no effect on the set of file descriptors being watched, or the time |
921 | waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it |
934 | waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it |
922 | to take note of any changes you made. |
935 | to take note of any changes you made. |
923 | |
936 | |
924 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
937 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
925 | invocations of C<release> and C<acquire>. |
938 | invocations of C<release> and C<acquire>. |
926 | |
939 | |
… | |
… | |
1023 | =item C<EV_WRITE> |
1036 | =item C<EV_WRITE> |
1024 | |
1037 | |
1025 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1038 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1026 | writable. |
1039 | writable. |
1027 | |
1040 | |
1028 | =item C<EV_TIMEOUT> |
1041 | =item C<EV_TIMER> |
1029 | |
1042 | |
1030 | The C<ev_timer> watcher has timed out. |
1043 | The C<ev_timer> watcher has timed out. |
1031 | |
1044 | |
1032 | =item C<EV_PERIODIC> |
1045 | =item C<EV_PERIODIC> |
1033 | |
1046 | |
… | |
… | |
1123 | |
1136 | |
1124 | ev_io w; |
1137 | ev_io w; |
1125 | ev_init (&w, my_cb); |
1138 | ev_init (&w, my_cb); |
1126 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1139 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1127 | |
1140 | |
1128 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1141 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
1129 | |
1142 | |
1130 | This macro initialises the type-specific parts of a watcher. You need to |
1143 | This macro initialises the type-specific parts of a watcher. You need to |
1131 | call C<ev_init> at least once before you call this macro, but you can |
1144 | call C<ev_init> at least once before you call this macro, but you can |
1132 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1145 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1133 | macro on a watcher that is active (it can be pending, however, which is a |
1146 | macro on a watcher that is active (it can be pending, however, which is a |
… | |
… | |
1146 | |
1159 | |
1147 | Example: Initialise and set an C<ev_io> watcher in one step. |
1160 | Example: Initialise and set an C<ev_io> watcher in one step. |
1148 | |
1161 | |
1149 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1162 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1150 | |
1163 | |
1151 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1164 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
1152 | |
1165 | |
1153 | Starts (activates) the given watcher. Only active watchers will receive |
1166 | Starts (activates) the given watcher. Only active watchers will receive |
1154 | events. If the watcher is already active nothing will happen. |
1167 | events. If the watcher is already active nothing will happen. |
1155 | |
1168 | |
1156 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1169 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1157 | whole section. |
1170 | whole section. |
1158 | |
1171 | |
1159 | ev_io_start (EV_DEFAULT_UC, &w); |
1172 | ev_io_start (EV_DEFAULT_UC, &w); |
1160 | |
1173 | |
1161 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1174 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
1162 | |
1175 | |
1163 | Stops the given watcher if active, and clears the pending status (whether |
1176 | Stops the given watcher if active, and clears the pending status (whether |
1164 | the watcher was active or not). |
1177 | the watcher was active or not). |
1165 | |
1178 | |
1166 | It is possible that stopped watchers are pending - for example, |
1179 | It is possible that stopped watchers are pending - for example, |
… | |
… | |
1191 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1204 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1192 | |
1205 | |
1193 | Change the callback. You can change the callback at virtually any time |
1206 | Change the callback. You can change the callback at virtually any time |
1194 | (modulo threads). |
1207 | (modulo threads). |
1195 | |
1208 | |
1196 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1209 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1197 | |
1210 | |
1198 | =item int ev_priority (ev_TYPE *watcher) |
1211 | =item int ev_priority (ev_TYPE *watcher) |
1199 | |
1212 | |
1200 | Set and query the priority of the watcher. The priority is a small |
1213 | Set and query the priority of the watcher. The priority is a small |
1201 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1214 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
… | |
… | |
1232 | returns its C<revents> bitset (as if its callback was invoked). If the |
1245 | returns its C<revents> bitset (as if its callback was invoked). If the |
1233 | watcher isn't pending it does nothing and returns C<0>. |
1246 | watcher isn't pending it does nothing and returns C<0>. |
1234 | |
1247 | |
1235 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1248 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1236 | callback to be invoked, which can be accomplished with this function. |
1249 | callback to be invoked, which can be accomplished with this function. |
|
|
1250 | |
|
|
1251 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1252 | |
|
|
1253 | Feeds the given event set into the event loop, as if the specified event |
|
|
1254 | had happened for the specified watcher (which must be a pointer to an |
|
|
1255 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1256 | not free the watcher as long as it has pending events. |
|
|
1257 | |
|
|
1258 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1259 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1260 | not started in the first place. |
|
|
1261 | |
|
|
1262 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1263 | functions that do not need a watcher. |
1237 | |
1264 | |
1238 | =back |
1265 | =back |
1239 | |
1266 | |
1240 | |
1267 | |
1241 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1268 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
… | |
… | |
1515 | |
1542 | |
1516 | So when you encounter spurious, unexplained daemon exits, make sure you |
1543 | So when you encounter spurious, unexplained daemon exits, make sure you |
1517 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1544 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1518 | somewhere, as that would have given you a big clue). |
1545 | somewhere, as that would have given you a big clue). |
1519 | |
1546 | |
|
|
1547 | =head3 The special problem of accept()ing when you can't |
|
|
1548 | |
|
|
1549 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1550 | found in port-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1551 | connection from the pending queue in all error cases. |
|
|
1552 | |
|
|
1553 | For example, larger servers often run out of file descriptors (because |
|
|
1554 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1555 | rejecting the connection, leading to libev signalling readiness on |
|
|
1556 | the next iteration again (the connection still exists after all), and |
|
|
1557 | typically causing the program to loop at 100% CPU usage. |
|
|
1558 | |
|
|
1559 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1560 | operating systems, there is usually little the app can do to remedy the |
|
|
1561 | situation, and no known thread-safe method of removing the connection to |
|
|
1562 | cope with overload is known (to me). |
|
|
1563 | |
|
|
1564 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1565 | - when the program encounters an overload, it will just loop until the |
|
|
1566 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1567 | event-based way to handle this situation, so it's the best one can do. |
|
|
1568 | |
|
|
1569 | A better way to handle the situation is to log any errors other than |
|
|
1570 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1571 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1572 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1573 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1574 | usage. |
|
|
1575 | |
|
|
1576 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1577 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1578 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1579 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1580 | clients under typical overload conditions. |
|
|
1581 | |
|
|
1582 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1583 | is often done with C<malloc> failures, but this results in an easy |
|
|
1584 | opportunity for a DoS attack. |
1520 | |
1585 | |
1521 | =head3 Watcher-Specific Functions |
1586 | =head3 Watcher-Specific Functions |
1522 | |
1587 | |
1523 | =over 4 |
1588 | =over 4 |
1524 | |
1589 | |
… | |
… | |
1703 | to the current time (meaning we just have some activity :), then call the |
1768 | to the current time (meaning we just have some activity :), then call the |
1704 | callback, which will "do the right thing" and start the timer: |
1769 | callback, which will "do the right thing" and start the timer: |
1705 | |
1770 | |
1706 | ev_init (timer, callback); |
1771 | ev_init (timer, callback); |
1707 | last_activity = ev_now (loop); |
1772 | last_activity = ev_now (loop); |
1708 | callback (loop, timer, EV_TIMEOUT); |
1773 | callback (loop, timer, EV_TIMER); |
1709 | |
1774 | |
1710 | And when there is some activity, simply store the current time in |
1775 | And when there is some activity, simply store the current time in |
1711 | C<last_activity>, no libev calls at all: |
1776 | C<last_activity>, no libev calls at all: |
1712 | |
1777 | |
1713 | last_actiivty = ev_now (loop); |
1778 | last_actiivty = ev_now (loop); |
… | |
… | |
1837 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1902 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1838 | |
1903 | |
1839 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1904 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1840 | usage example. |
1905 | usage example. |
1841 | |
1906 | |
1842 | =item ev_timer_remaining (loop, ev_timer *) |
1907 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1843 | |
1908 | |
1844 | Returns the remaining time until a timer fires. If the timer is active, |
1909 | Returns the remaining time until a timer fires. If the timer is active, |
1845 | then this time is relative to the current event loop time, otherwise it's |
1910 | then this time is relative to the current event loop time, otherwise it's |
1846 | the timeout value currently configured. |
1911 | the timeout value currently configured. |
1847 | |
1912 | |
1848 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1913 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1849 | C<5>. When the timer is started and one second passes, C<ev_timer_remain> |
1914 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
1850 | will return C<4>. When the timer expires and is restarted, it will return |
1915 | will return C<4>. When the timer expires and is restarted, it will return |
1851 | roughly C<7> (likely slightly less as callback invocation takes some time, |
1916 | roughly C<7> (likely slightly less as callback invocation takes some time, |
1852 | too), and so on. |
1917 | too), and so on. |
1853 | |
1918 | |
1854 | =item ev_tstamp repeat [read-write] |
1919 | =item ev_tstamp repeat [read-write] |
… | |
… | |
2114 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2179 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2115 | not be unduly interrupted. If you have a problem with system calls getting |
2180 | not be unduly interrupted. If you have a problem with system calls getting |
2116 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2181 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2117 | and unblock them in an C<ev_prepare> watcher. |
2182 | and unblock them in an C<ev_prepare> watcher. |
2118 | |
2183 | |
2119 | =head3 The special problem of inheritance over execve |
2184 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2120 | |
2185 | |
2121 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2186 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2122 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2187 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2123 | stopping it again), that is, libev might or might not block the signal, |
2188 | stopping it again), that is, libev might or might not block the signal, |
2124 | and might or might not set or restore the installed signal handler. |
2189 | and might or might not set or restore the installed signal handler. |
… | |
… | |
2134 | |
2199 | |
2135 | The simplest way to ensure that the signal mask is reset in the child is |
2200 | The simplest way to ensure that the signal mask is reset in the child is |
2136 | to install a fork handler with C<pthread_atfork> that resets it. That will |
2201 | to install a fork handler with C<pthread_atfork> that resets it. That will |
2137 | catch fork calls done by libraries (such as the libc) as well. |
2202 | catch fork calls done by libraries (such as the libc) as well. |
2138 | |
2203 | |
2139 | In current versions of libev, you can also ensure that the signal mask is |
2204 | In current versions of libev, the signal will not be blocked indefinitely |
2140 | not blocking any signals (except temporarily, so thread users watch out) |
2205 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
2141 | by specifying the C<EVFLAG_NOSIGNALFD> when creating the event loop. This |
2206 | the window of opportunity for problems, it will not go away, as libev |
2142 | is not guaranteed for future versions, however. |
2207 | I<has> to modify the signal mask, at least temporarily. |
|
|
2208 | |
|
|
2209 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2210 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2211 | is not a libev-specific thing, this is true for most event libraries. |
2143 | |
2212 | |
2144 | =head3 Watcher-Specific Functions and Data Members |
2213 | =head3 Watcher-Specific Functions and Data Members |
2145 | |
2214 | |
2146 | =over 4 |
2215 | =over 4 |
2147 | |
2216 | |
… | |
… | |
2964 | =head3 Queueing |
3033 | =head3 Queueing |
2965 | |
3034 | |
2966 | C<ev_async> does not support queueing of data in any way. The reason |
3035 | C<ev_async> does not support queueing of data in any way. The reason |
2967 | is that the author does not know of a simple (or any) algorithm for a |
3036 | is that the author does not know of a simple (or any) algorithm for a |
2968 | multiple-writer-single-reader queue that works in all cases and doesn't |
3037 | multiple-writer-single-reader queue that works in all cases and doesn't |
2969 | need elaborate support such as pthreads. |
3038 | need elaborate support such as pthreads or unportable memory access |
|
|
3039 | semantics. |
2970 | |
3040 | |
2971 | That means that if you want to queue data, you have to provide your own |
3041 | That means that if you want to queue data, you have to provide your own |
2972 | queue. But at least I can tell you how to implement locking around your |
3042 | queue. But at least I can tell you how to implement locking around your |
2973 | queue: |
3043 | queue: |
2974 | |
3044 | |
… | |
… | |
3113 | |
3183 | |
3114 | If C<timeout> is less than 0, then no timeout watcher will be |
3184 | If C<timeout> is less than 0, then no timeout watcher will be |
3115 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3185 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3116 | repeat = 0) will be started. C<0> is a valid timeout. |
3186 | repeat = 0) will be started. C<0> is a valid timeout. |
3117 | |
3187 | |
3118 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3188 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
3119 | passed an C<revents> set like normal event callbacks (a combination of |
3189 | passed an C<revents> set like normal event callbacks (a combination of |
3120 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3190 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
3121 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3191 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3122 | a timeout and an io event at the same time - you probably should give io |
3192 | a timeout and an io event at the same time - you probably should give io |
3123 | events precedence. |
3193 | events precedence. |
3124 | |
3194 | |
3125 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3195 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3126 | |
3196 | |
3127 | static void stdin_ready (int revents, void *arg) |
3197 | static void stdin_ready (int revents, void *arg) |
3128 | { |
3198 | { |
3129 | if (revents & EV_READ) |
3199 | if (revents & EV_READ) |
3130 | /* stdin might have data for us, joy! */; |
3200 | /* stdin might have data for us, joy! */; |
3131 | else if (revents & EV_TIMEOUT) |
3201 | else if (revents & EV_TIMER) |
3132 | /* doh, nothing entered */; |
3202 | /* doh, nothing entered */; |
3133 | } |
3203 | } |
3134 | |
3204 | |
3135 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3205 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3136 | |
3206 | |
3137 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
|
|
3138 | |
|
|
3139 | Feeds the given event set into the event loop, as if the specified event |
|
|
3140 | had happened for the specified watcher (which must be a pointer to an |
|
|
3141 | initialised but not necessarily started event watcher). |
|
|
3142 | |
|
|
3143 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
3207 | =item ev_feed_fd_event (loop, int fd, int revents) |
3144 | |
3208 | |
3145 | Feed an event on the given fd, as if a file descriptor backend detected |
3209 | Feed an event on the given fd, as if a file descriptor backend detected |
3146 | the given events it. |
3210 | the given events it. |
3147 | |
3211 | |
3148 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
3212 | =item ev_feed_signal_event (loop, int signum) |
3149 | |
3213 | |
3150 | Feed an event as if the given signal occurred (C<loop> must be the default |
3214 | Feed an event as if the given signal occurred (C<loop> must be the default |
3151 | loop!). |
3215 | loop!). |
3152 | |
3216 | |
3153 | =back |
3217 | =back |
… | |
… | |
3233 | |
3297 | |
3234 | =over 4 |
3298 | =over 4 |
3235 | |
3299 | |
3236 | =item ev::TYPE::TYPE () |
3300 | =item ev::TYPE::TYPE () |
3237 | |
3301 | |
3238 | =item ev::TYPE::TYPE (struct ev_loop *) |
3302 | =item ev::TYPE::TYPE (loop) |
3239 | |
3303 | |
3240 | =item ev::TYPE::~TYPE |
3304 | =item ev::TYPE::~TYPE |
3241 | |
3305 | |
3242 | The constructor (optionally) takes an event loop to associate the watcher |
3306 | The constructor (optionally) takes an event loop to associate the watcher |
3243 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3307 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
3320 | Example: Use a plain function as callback. |
3384 | Example: Use a plain function as callback. |
3321 | |
3385 | |
3322 | static void io_cb (ev::io &w, int revents) { } |
3386 | static void io_cb (ev::io &w, int revents) { } |
3323 | iow.set <io_cb> (); |
3387 | iow.set <io_cb> (); |
3324 | |
3388 | |
3325 | =item w->set (struct ev_loop *) |
3389 | =item w->set (loop) |
3326 | |
3390 | |
3327 | Associates a different C<struct ev_loop> with this watcher. You can only |
3391 | Associates a different C<struct ev_loop> with this watcher. You can only |
3328 | do this when the watcher is inactive (and not pending either). |
3392 | do this when the watcher is inactive (and not pending either). |
3329 | |
3393 | |
3330 | =item w->set ([arguments]) |
3394 | =item w->set ([arguments]) |
… | |
… | |
3429 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3493 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3430 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3494 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3431 | |
3495 | |
3432 | =item Lua |
3496 | =item Lua |
3433 | |
3497 | |
3434 | Brian Maher has written a partial interface to libev |
3498 | Brian Maher has written a partial interface to libev for lua (at the |
3435 | for lua (only C<ev_io> and C<ev_timer>), to be found at |
3499 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3436 | L<http://github.com/brimworks/lua-ev>. |
3500 | L<http://github.com/brimworks/lua-ev>. |
3437 | |
3501 | |
3438 | =back |
3502 | =back |
3439 | |
3503 | |
3440 | |
3504 | |
… | |
… | |
3595 | libev.m4 |
3659 | libev.m4 |
3596 | |
3660 | |
3597 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3661 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3598 | |
3662 | |
3599 | Libev can be configured via a variety of preprocessor symbols you have to |
3663 | Libev can be configured via a variety of preprocessor symbols you have to |
3600 | define before including any of its files. The default in the absence of |
3664 | define before including (or compiling) any of its files. The default in |
3601 | autoconf is documented for every option. |
3665 | the absence of autoconf is documented for every option. |
|
|
3666 | |
|
|
3667 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3668 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3669 | to redefine them before including F<ev.h> without breakign compatibility |
|
|
3670 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3671 | users of libev and the libev code itself must be compiled with compatible |
|
|
3672 | settings. |
3602 | |
3673 | |
3603 | =over 4 |
3674 | =over 4 |
3604 | |
3675 | |
3605 | =item EV_STANDALONE |
3676 | =item EV_STANDALONE (h) |
3606 | |
3677 | |
3607 | Must always be C<1> if you do not use autoconf configuration, which |
3678 | Must always be C<1> if you do not use autoconf configuration, which |
3608 | keeps libev from including F<config.h>, and it also defines dummy |
3679 | keeps libev from including F<config.h>, and it also defines dummy |
3609 | implementations for some libevent functions (such as logging, which is not |
3680 | implementations for some libevent functions (such as logging, which is not |
3610 | supported). It will also not define any of the structs usually found in |
3681 | supported). It will also not define any of the structs usually found in |
… | |
… | |
3760 | as well as for signal and thread safety in C<ev_async> watchers. |
3831 | as well as for signal and thread safety in C<ev_async> watchers. |
3761 | |
3832 | |
3762 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3833 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3763 | (from F<signal.h>), which is usually good enough on most platforms. |
3834 | (from F<signal.h>), which is usually good enough on most platforms. |
3764 | |
3835 | |
3765 | =item EV_H |
3836 | =item EV_H (h) |
3766 | |
3837 | |
3767 | The name of the F<ev.h> header file used to include it. The default if |
3838 | The name of the F<ev.h> header file used to include it. The default if |
3768 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3839 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3769 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3840 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3770 | |
3841 | |
3771 | =item EV_CONFIG_H |
3842 | =item EV_CONFIG_H (h) |
3772 | |
3843 | |
3773 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3844 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3774 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3845 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3775 | C<EV_H>, above. |
3846 | C<EV_H>, above. |
3776 | |
3847 | |
3777 | =item EV_EVENT_H |
3848 | =item EV_EVENT_H (h) |
3778 | |
3849 | |
3779 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3850 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3780 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3851 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3781 | |
3852 | |
3782 | =item EV_PROTOTYPES |
3853 | =item EV_PROTOTYPES (h) |
3783 | |
3854 | |
3784 | If defined to be C<0>, then F<ev.h> will not define any function |
3855 | If defined to be C<0>, then F<ev.h> will not define any function |
3785 | prototypes, but still define all the structs and other symbols. This is |
3856 | prototypes, but still define all the structs and other symbols. This is |
3786 | occasionally useful if you want to provide your own wrapper functions |
3857 | occasionally useful if you want to provide your own wrapper functions |
3787 | around libev functions. |
3858 | around libev functions. |
… | |
… | |
3809 | fine. |
3880 | fine. |
3810 | |
3881 | |
3811 | If your embedding application does not need any priorities, defining these |
3882 | If your embedding application does not need any priorities, defining these |
3812 | both to C<0> will save some memory and CPU. |
3883 | both to C<0> will save some memory and CPU. |
3813 | |
3884 | |
3814 | =item EV_PERIODIC_ENABLE |
3885 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
3886 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
3887 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3815 | |
3888 | |
3816 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3889 | If undefined or defined to be C<1> (and the platform supports it), then |
3817 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3890 | the respective watcher type is supported. If defined to be C<0>, then it |
3818 | code. |
3891 | is not. Disabling watcher types mainly saves codesize. |
3819 | |
3892 | |
3820 | =item EV_IDLE_ENABLE |
3893 | =item EV_FEATURES |
3821 | |
|
|
3822 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3823 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3824 | code. |
|
|
3825 | |
|
|
3826 | =item EV_EMBED_ENABLE |
|
|
3827 | |
|
|
3828 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3829 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3830 | watcher types, which therefore must not be disabled. |
|
|
3831 | |
|
|
3832 | =item EV_STAT_ENABLE |
|
|
3833 | |
|
|
3834 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3835 | defined to be C<0>, then they are not. |
|
|
3836 | |
|
|
3837 | =item EV_FORK_ENABLE |
|
|
3838 | |
|
|
3839 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3840 | defined to be C<0>, then they are not. |
|
|
3841 | |
|
|
3842 | =item EV_ASYNC_ENABLE |
|
|
3843 | |
|
|
3844 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3845 | defined to be C<0>, then they are not. |
|
|
3846 | |
|
|
3847 | =item EV_MINIMAL |
|
|
3848 | |
3894 | |
3849 | If you need to shave off some kilobytes of code at the expense of some |
3895 | If you need to shave off some kilobytes of code at the expense of some |
3850 | speed (but with the full API), define this symbol to C<1>. Currently this |
3896 | speed (but with the full API), you can define this symbol to request |
3851 | is used to override some inlining decisions, saves roughly 30% code size |
3897 | certain subsets of functionality. The default is to enable all features |
3852 | on amd64. It also selects a much smaller 2-heap for timer management over |
3898 | that can be enabled on the platform. |
3853 | the default 4-heap. |
|
|
3854 | |
3899 | |
3855 | You can save even more by disabling watcher types you do not need |
3900 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
3856 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
3901 | with some broad features you want) and then selectively re-enable |
3857 | (C<-DNDEBUG>) will usually reduce code size a lot. |
3902 | additional parts you want, for example if you want everything minimal, |
|
|
3903 | but multiple event loop support, async and child watchers and the poll |
|
|
3904 | backend, use this: |
3858 | |
3905 | |
3859 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
3906 | #define EV_FEATURES 0 |
3860 | provide a bare-bones event library. See C<ev.h> for details on what parts |
3907 | #define EV_MULTIPLICITY 1 |
3861 | of the API are still available, and do not complain if this subset changes |
3908 | #define EV_USE_POLL 1 |
3862 | over time. |
3909 | #define EV_CHILD_ENABLE 1 |
|
|
3910 | #define EV_ASYNC_ENABLE 1 |
|
|
3911 | |
|
|
3912 | The actual value is a bitset, it can be a combination of the following |
|
|
3913 | values: |
|
|
3914 | |
|
|
3915 | =over 4 |
|
|
3916 | |
|
|
3917 | =item C<1> - faster/larger code |
|
|
3918 | |
|
|
3919 | Use larger code to speed up some operations. |
|
|
3920 | |
|
|
3921 | Currently this is used to override some inlining decisions (enlarging the roughly |
|
|
3922 | 30% code size on amd64. |
|
|
3923 | |
|
|
3924 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
3925 | gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
3926 | assertions. |
|
|
3927 | |
|
|
3928 | =item C<2> - faster/larger data structures |
|
|
3929 | |
|
|
3930 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
3931 | hash table sizes and so on. This will usually further increase codesize |
|
|
3932 | and can additionally have an effect on the size of data structures at |
|
|
3933 | runtime. |
|
|
3934 | |
|
|
3935 | =item C<4> - full API configuration |
|
|
3936 | |
|
|
3937 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
3938 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
3939 | |
|
|
3940 | =item C<8> - full API |
|
|
3941 | |
|
|
3942 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
3943 | details on which parts of the API are still available without this |
|
|
3944 | feature, and do not complain if this subset changes over time. |
|
|
3945 | |
|
|
3946 | =item C<16> - enable all optional watcher types |
|
|
3947 | |
|
|
3948 | Enables all optional watcher types. If you want to selectively enable |
|
|
3949 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
3950 | embed, async, child...) you can enable them manually by defining |
|
|
3951 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
3952 | |
|
|
3953 | =item C<32> - enable all backends |
|
|
3954 | |
|
|
3955 | This enables all backends - without this feature, you need to enable at |
|
|
3956 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
3957 | |
|
|
3958 | =item C<64> - enable OS-specific "helper" APIs |
|
|
3959 | |
|
|
3960 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
3961 | default. |
|
|
3962 | |
|
|
3963 | =back |
|
|
3964 | |
|
|
3965 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
3966 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
3967 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
3968 | watchers, timers and monotonic clock support. |
|
|
3969 | |
|
|
3970 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
3971 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
3972 | your program might be left out as well - a binary starting a timer and an |
|
|
3973 | I/O watcher then might come out at only 5Kb. |
|
|
3974 | |
|
|
3975 | =item EV_AVOID_STDIO |
|
|
3976 | |
|
|
3977 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
3978 | functions (printf, scanf, perror etc.). This will increase the codesize |
|
|
3979 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
3980 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
3981 | big. |
|
|
3982 | |
|
|
3983 | Note that error messages might become less precise when this option is |
|
|
3984 | enabled. |
3863 | |
3985 | |
3864 | =item EV_NSIG |
3986 | =item EV_NSIG |
3865 | |
3987 | |
3866 | The highest supported signal number, +1 (or, the number of |
3988 | The highest supported signal number, +1 (or, the number of |
3867 | signals): Normally, libev tries to deduce the maximum number of signals |
3989 | signals): Normally, libev tries to deduce the maximum number of signals |
… | |
… | |
3871 | statically allocates some 12-24 bytes per signal number. |
3993 | statically allocates some 12-24 bytes per signal number. |
3872 | |
3994 | |
3873 | =item EV_PID_HASHSIZE |
3995 | =item EV_PID_HASHSIZE |
3874 | |
3996 | |
3875 | C<ev_child> watchers use a small hash table to distribute workload by |
3997 | C<ev_child> watchers use a small hash table to distribute workload by |
3876 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3998 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3877 | than enough. If you need to manage thousands of children you might want to |
3999 | usually more than enough. If you need to manage thousands of children you |
3878 | increase this value (I<must> be a power of two). |
4000 | might want to increase this value (I<must> be a power of two). |
3879 | |
4001 | |
3880 | =item EV_INOTIFY_HASHSIZE |
4002 | =item EV_INOTIFY_HASHSIZE |
3881 | |
4003 | |
3882 | C<ev_stat> watchers use a small hash table to distribute workload by |
4004 | C<ev_stat> watchers use a small hash table to distribute workload by |
3883 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4005 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3884 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4006 | disabled), usually more than enough. If you need to manage thousands of |
3885 | watchers you might want to increase this value (I<must> be a power of |
4007 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3886 | two). |
4008 | power of two). |
3887 | |
4009 | |
3888 | =item EV_USE_4HEAP |
4010 | =item EV_USE_4HEAP |
3889 | |
4011 | |
3890 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4012 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3891 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4013 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3892 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4014 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3893 | faster performance with many (thousands) of watchers. |
4015 | faster performance with many (thousands) of watchers. |
3894 | |
4016 | |
3895 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4017 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3896 | (disabled). |
4018 | will be C<0>. |
3897 | |
4019 | |
3898 | =item EV_HEAP_CACHE_AT |
4020 | =item EV_HEAP_CACHE_AT |
3899 | |
4021 | |
3900 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4022 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3901 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4023 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3902 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4024 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3903 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4025 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3904 | but avoids random read accesses on heap changes. This improves performance |
4026 | but avoids random read accesses on heap changes. This improves performance |
3905 | noticeably with many (hundreds) of watchers. |
4027 | noticeably with many (hundreds) of watchers. |
3906 | |
4028 | |
3907 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4029 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3908 | (disabled). |
4030 | will be C<0>. |
3909 | |
4031 | |
3910 | =item EV_VERIFY |
4032 | =item EV_VERIFY |
3911 | |
4033 | |
3912 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4034 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
3913 | be done: If set to C<0>, no internal verification code will be compiled |
4035 | be done: If set to C<0>, no internal verification code will be compiled |
… | |
… | |
3915 | called. If set to C<2>, then the internal verification code will be |
4037 | called. If set to C<2>, then the internal verification code will be |
3916 | called once per loop, which can slow down libev. If set to C<3>, then the |
4038 | called once per loop, which can slow down libev. If set to C<3>, then the |
3917 | verification code will be called very frequently, which will slow down |
4039 | verification code will be called very frequently, which will slow down |
3918 | libev considerably. |
4040 | libev considerably. |
3919 | |
4041 | |
3920 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4042 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3921 | C<0>. |
4043 | will be C<0>. |
3922 | |
4044 | |
3923 | =item EV_COMMON |
4045 | =item EV_COMMON |
3924 | |
4046 | |
3925 | By default, all watchers have a C<void *data> member. By redefining |
4047 | By default, all watchers have a C<void *data> member. By redefining |
3926 | this macro to a something else you can include more and other types of |
4048 | this macro to a something else you can include more and other types of |
… | |
… | |
3984 | file. |
4106 | file. |
3985 | |
4107 | |
3986 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4108 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3987 | that everybody includes and which overrides some configure choices: |
4109 | that everybody includes and which overrides some configure choices: |
3988 | |
4110 | |
3989 | #define EV_MINIMAL 1 |
4111 | #define EV_FEATURES 8 |
3990 | #define EV_USE_POLL 0 |
4112 | #define EV_USE_SELECT 1 |
3991 | #define EV_MULTIPLICITY 0 |
|
|
3992 | #define EV_PERIODIC_ENABLE 0 |
4113 | #define EV_PREPARE_ENABLE 1 |
|
|
4114 | #define EV_IDLE_ENABLE 1 |
3993 | #define EV_STAT_ENABLE 0 |
4115 | #define EV_SIGNAL_ENABLE 1 |
3994 | #define EV_FORK_ENABLE 0 |
4116 | #define EV_CHILD_ENABLE 1 |
|
|
4117 | #define EV_USE_STDEXCEPT 0 |
3995 | #define EV_CONFIG_H <config.h> |
4118 | #define EV_CONFIG_H <config.h> |
3996 | #define EV_MINPRI 0 |
|
|
3997 | #define EV_MAXPRI 0 |
|
|
3998 | |
4119 | |
3999 | #include "ev++.h" |
4120 | #include "ev++.h" |
4000 | |
4121 | |
4001 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4122 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4002 | |
4123 | |
… | |
… | |
4504 | involves iterating over all running async watchers or all signal numbers. |
4625 | involves iterating over all running async watchers or all signal numbers. |
4505 | |
4626 | |
4506 | =back |
4627 | =back |
4507 | |
4628 | |
4508 | |
4629 | |
|
|
4630 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
4631 | |
|
|
4632 | The major version 4 introduced some minor incompatible changes to the API. |
|
|
4633 | |
|
|
4634 | At the moment, the C<ev.h> header file tries to implement superficial |
|
|
4635 | compatibility, so most programs should still compile. Those might be |
|
|
4636 | removed in later versions of libev, so better update early than late. |
|
|
4637 | |
|
|
4638 | =over 4 |
|
|
4639 | |
|
|
4640 | =item C<ev_loop_count> renamed to C<ev_iteration> |
|
|
4641 | |
|
|
4642 | =item C<ev_loop_depth> renamed to C<ev_depth> |
|
|
4643 | |
|
|
4644 | =item C<ev_loop_verify> renamed to C<ev_verify> |
|
|
4645 | |
|
|
4646 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4647 | C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is |
|
|
4648 | still called C<ev_loop_fork> because it would otherwise clash with the |
|
|
4649 | C<ev_frok> typedef. |
|
|
4650 | |
|
|
4651 | =item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents> |
|
|
4652 | |
|
|
4653 | This is a simple rename - all other watcher types use their name |
|
|
4654 | as revents flag, and now C<ev_timer> does, too. |
|
|
4655 | |
|
|
4656 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
|
|
4657 | and continue to be present for the forseeable future, so this is mostly a |
|
|
4658 | documentation change. |
|
|
4659 | |
|
|
4660 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
4661 | |
|
|
4662 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
4663 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
4664 | and work, but the library code will of course be larger. |
|
|
4665 | |
|
|
4666 | =back |
|
|
4667 | |
|
|
4668 | |
4509 | =head1 GLOSSARY |
4669 | =head1 GLOSSARY |
4510 | |
4670 | |
4511 | =over 4 |
4671 | =over 4 |
4512 | |
4672 | |
4513 | =item active |
4673 | =item active |
… | |
… | |
4534 | A change of state of some external event, such as data now being available |
4694 | A change of state of some external event, such as data now being available |
4535 | for reading on a file descriptor, time having passed or simply not having |
4695 | for reading on a file descriptor, time having passed or simply not having |
4536 | any other events happening anymore. |
4696 | any other events happening anymore. |
4537 | |
4697 | |
4538 | In libev, events are represented as single bits (such as C<EV_READ> or |
4698 | In libev, events are represented as single bits (such as C<EV_READ> or |
4539 | C<EV_TIMEOUT>). |
4699 | C<EV_TIMER>). |
4540 | |
4700 | |
4541 | =item event library |
4701 | =item event library |
4542 | |
4702 | |
4543 | A software package implementing an event model and loop. |
4703 | A software package implementing an event model and loop. |
4544 | |
4704 | |