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4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
8 | |
9 | =head1 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | #include <ev.h> |
11 | #include <ev.h> |
12 | |
12 | |
13 | ev_io stdin_watcher; |
13 | ev_io stdin_watcher; |
14 | ev_timer timeout_watcher; |
14 | ev_timer timeout_watcher; |
… | |
… | |
53 | The newest version of this document is also available as a html-formatted |
53 | The newest version of this document is also available as a html-formatted |
54 | web page you might find easier to navigate when reading it for the first |
54 | web page you might find easier to navigate when reading it for the first |
55 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
55 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
56 | |
56 | |
57 | Libev is an event loop: you register interest in certain events (such as a |
57 | Libev is an event loop: you register interest in certain events (such as a |
58 | file descriptor being readable or a timeout occuring), and it will manage |
58 | file descriptor being readable or a timeout occurring), and it will manage |
59 | these event sources and provide your program with events. |
59 | these event sources and provide your program with events. |
60 | |
60 | |
61 | To do this, it must take more or less complete control over your process |
61 | To do this, it must take more or less complete control over your process |
62 | (or thread) by executing the I<event loop> handler, and will then |
62 | (or thread) by executing the I<event loop> handler, and will then |
63 | communicate events via a callback mechanism. |
63 | communicate events via a callback mechanism. |
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65 | You register interest in certain events by registering so-called I<event |
65 | You register interest in certain events by registering so-called I<event |
66 | watchers>, which are relatively small C structures you initialise with the |
66 | watchers>, which are relatively small C structures you initialise with the |
67 | details of the event, and then hand it over to libev by I<starting> the |
67 | details of the event, and then hand it over to libev by I<starting> the |
68 | watcher. |
68 | watcher. |
69 | |
69 | |
70 | =head1 FEATURES |
70 | =head2 FEATURES |
71 | |
71 | |
72 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
72 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
73 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
73 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
74 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
74 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
75 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
75 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
… | |
… | |
82 | |
82 | |
83 | It also is quite fast (see this |
83 | It also is quite fast (see this |
84 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
84 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
85 | for example). |
85 | for example). |
86 | |
86 | |
87 | =head1 CONVENTIONS |
87 | =head2 CONVENTIONS |
88 | |
88 | |
89 | Libev is very configurable. In this manual the default configuration will |
89 | Libev is very configurable. In this manual the default configuration will |
90 | be described, which supports multiple event loops. For more info about |
90 | be described, which supports multiple event loops. For more info about |
91 | various configuration options please have a look at B<EMBED> section in |
91 | various configuration options please have a look at B<EMBED> section in |
92 | this manual. If libev was configured without support for multiple event |
92 | this manual. If libev was configured without support for multiple event |
93 | loops, then all functions taking an initial argument of name C<loop> |
93 | loops, then all functions taking an initial argument of name C<loop> |
94 | (which is always of type C<struct ev_loop *>) will not have this argument. |
94 | (which is always of type C<struct ev_loop *>) will not have this argument. |
95 | |
95 | |
96 | =head1 TIME REPRESENTATION |
96 | =head2 TIME REPRESENTATION |
97 | |
97 | |
98 | Libev represents time as a single floating point number, representing the |
98 | Libev represents time as a single floating point number, representing the |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
100 | the beginning of 1970, details are complicated, don't ask). This type is |
100 | the beginning of 1970, details are complicated, don't ask). This type is |
101 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
101 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
102 | to the C<double> type in C, and when you need to do any calculations on |
102 | to the C<double> type in C, and when you need to do any calculations on |
103 | it, you should treat it as such. |
103 | it, you should treat it as some floatingpoint value. Unlike the name |
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104 | component C<stamp> might indicate, it is also used for time differences |
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105 | throughout libev. |
104 | |
106 | |
105 | =head1 GLOBAL FUNCTIONS |
107 | =head1 GLOBAL FUNCTIONS |
106 | |
108 | |
107 | These functions can be called anytime, even before initialising the |
109 | These functions can be called anytime, even before initialising the |
108 | library in any way. |
110 | library in any way. |
… | |
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112 | =item ev_tstamp ev_time () |
114 | =item ev_tstamp ev_time () |
113 | |
115 | |
114 | Returns the current time as libev would use it. Please note that the |
116 | Returns the current time as libev would use it. Please note that the |
115 | C<ev_now> function is usually faster and also often returns the timestamp |
117 | C<ev_now> function is usually faster and also often returns the timestamp |
116 | you actually want to know. |
118 | you actually want to know. |
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119 | |
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120 | =item ev_sleep (ev_tstamp interval) |
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121 | |
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122 | Sleep for the given interval: The current thread will be blocked until |
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123 | either it is interrupted or the given time interval has passed. Basically |
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124 | this is a subsecond-resolution C<sleep ()>. |
117 | |
125 | |
118 | =item int ev_version_major () |
126 | =item int ev_version_major () |
119 | |
127 | |
120 | =item int ev_version_minor () |
128 | =item int ev_version_minor () |
121 | |
129 | |
… | |
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298 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
306 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
299 | |
307 | |
300 | This is your standard select(2) backend. Not I<completely> standard, as |
308 | This is your standard select(2) backend. Not I<completely> standard, as |
301 | libev tries to roll its own fd_set with no limits on the number of fds, |
309 | libev tries to roll its own fd_set with no limits on the number of fds, |
302 | but if that fails, expect a fairly low limit on the number of fds when |
310 | but if that fails, expect a fairly low limit on the number of fds when |
303 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
311 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
304 | the fastest backend for a low number of fds. |
312 | usually the fastest backend for a low number of (low-numbered :) fds. |
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313 | |
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314 | To get good performance out of this backend you need a high amount of |
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315 | parallelity (most of the file descriptors should be busy). If you are |
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316 | writing a server, you should C<accept ()> in a loop to accept as many |
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317 | connections as possible during one iteration. You might also want to have |
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318 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
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319 | readyness notifications you get per iteration. |
305 | |
320 | |
306 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
321 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
307 | |
322 | |
308 | And this is your standard poll(2) backend. It's more complicated than |
323 | And this is your standard poll(2) backend. It's more complicated |
309 | select, but handles sparse fds better and has no artificial limit on the |
324 | than select, but handles sparse fds better and has no artificial |
310 | number of fds you can use (except it will slow down considerably with a |
325 | limit on the number of fds you can use (except it will slow down |
311 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
326 | considerably with a lot of inactive fds). It scales similarly to select, |
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327 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
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328 | performance tips. |
312 | |
329 | |
313 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
330 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
314 | |
331 | |
315 | For few fds, this backend is a bit little slower than poll and select, |
332 | For few fds, this backend is a bit little slower than poll and select, |
316 | but it scales phenomenally better. While poll and select usually scale like |
333 | but it scales phenomenally better. While poll and select usually scale |
317 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
334 | like O(total_fds) where n is the total number of fds (or the highest fd), |
318 | either O(1) or O(active_fds). |
335 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
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336 | of shortcomings, such as silently dropping events in some hard-to-detect |
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337 | cases and rewiring a syscall per fd change, no fork support and bad |
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338 | support for dup. |
319 | |
339 | |
320 | While stopping and starting an I/O watcher in the same iteration will |
340 | While stopping, setting and starting an I/O watcher in the same iteration |
321 | result in some caching, there is still a syscall per such incident |
341 | will result in some caching, there is still a syscall per such incident |
322 | (because the fd could point to a different file description now), so its |
342 | (because the fd could point to a different file description now), so its |
323 | best to avoid that. Also, dup()ed file descriptors might not work very |
343 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
324 | well if you register events for both fds. |
344 | very well if you register events for both fds. |
325 | |
345 | |
326 | Please note that epoll sometimes generates spurious notifications, so you |
346 | Please note that epoll sometimes generates spurious notifications, so you |
327 | need to use non-blocking I/O or other means to avoid blocking when no data |
347 | need to use non-blocking I/O or other means to avoid blocking when no data |
328 | (or space) is available. |
348 | (or space) is available. |
329 | |
349 | |
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350 | Best performance from this backend is achieved by not unregistering all |
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351 | watchers for a file descriptor until it has been closed, if possible, i.e. |
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352 | keep at least one watcher active per fd at all times. |
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353 | |
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354 | While nominally embeddeble in other event loops, this feature is broken in |
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355 | all kernel versions tested so far. |
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356 | |
330 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
357 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
331 | |
358 | |
332 | Kqueue deserves special mention, as at the time of this writing, it |
359 | Kqueue deserves special mention, as at the time of this writing, it |
333 | was broken on all BSDs except NetBSD (usually it doesn't work with |
360 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
334 | anything but sockets and pipes, except on Darwin, where of course its |
361 | with anything but sockets and pipes, except on Darwin, where of course |
335 | completely useless). For this reason its not being "autodetected" |
362 | it's completely useless). For this reason it's not being "autodetected" |
336 | unless you explicitly specify it explicitly in the flags (i.e. using |
363 | unless you explicitly specify it explicitly in the flags (i.e. using |
337 | C<EVBACKEND_KQUEUE>). |
364 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
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365 | system like NetBSD. |
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366 | |
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367 | You still can embed kqueue into a normal poll or select backend and use it |
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368 | only for sockets (after having made sure that sockets work with kqueue on |
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369 | the target platform). See C<ev_embed> watchers for more info. |
338 | |
370 | |
339 | It scales in the same way as the epoll backend, but the interface to the |
371 | It scales in the same way as the epoll backend, but the interface to the |
340 | kernel is more efficient (which says nothing about its actual speed, of |
372 | kernel is more efficient (which says nothing about its actual speed, of |
341 | course). While starting and stopping an I/O watcher does not cause an |
373 | course). While stopping, setting and starting an I/O watcher does never |
342 | extra syscall as with epoll, it still adds up to four event changes per |
374 | cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to |
343 | incident, so its best to avoid that. |
375 | two event changes per incident, support for C<fork ()> is very bad and it |
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376 | drops fds silently in similarly hard-to-detect cases. |
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377 | |
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378 | This backend usually performs well under most conditions. |
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379 | |
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380 | While nominally embeddable in other event loops, this doesn't work |
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381 | everywhere, so you might need to test for this. And since it is broken |
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382 | almost everywhere, you should only use it when you have a lot of sockets |
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383 | (for which it usually works), by embedding it into another event loop |
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384 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
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385 | sockets. |
344 | |
386 | |
345 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
387 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
346 | |
388 | |
347 | This is not implemented yet (and might never be). |
389 | This is not implemented yet (and might never be, unless you send me an |
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390 | implementation). According to reports, C</dev/poll> only supports sockets |
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391 | and is not embeddable, which would limit the usefulness of this backend |
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392 | immensely. |
348 | |
393 | |
349 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
394 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
350 | |
395 | |
351 | This uses the Solaris 10 port mechanism. As with everything on Solaris, |
396 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
352 | it's really slow, but it still scales very well (O(active_fds)). |
397 | it's really slow, but it still scales very well (O(active_fds)). |
353 | |
398 | |
354 | Please note that solaris ports can result in a lot of spurious |
399 | Please note that solaris event ports can deliver a lot of spurious |
355 | notifications, so you need to use non-blocking I/O or other means to avoid |
400 | notifications, so you need to use non-blocking I/O or other means to avoid |
356 | blocking when no data (or space) is available. |
401 | blocking when no data (or space) is available. |
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402 | |
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403 | While this backend scales well, it requires one system call per active |
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404 | file descriptor per loop iteration. For small and medium numbers of file |
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405 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
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406 | might perform better. |
357 | |
407 | |
358 | =item C<EVBACKEND_ALL> |
408 | =item C<EVBACKEND_ALL> |
359 | |
409 | |
360 | Try all backends (even potentially broken ones that wouldn't be tried |
410 | Try all backends (even potentially broken ones that wouldn't be tried |
361 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
411 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
362 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
412 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
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413 | |
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414 | It is definitely not recommended to use this flag. |
363 | |
415 | |
364 | =back |
416 | =back |
365 | |
417 | |
366 | If one or more of these are ored into the flags value, then only these |
418 | If one or more of these are ored into the flags value, then only these |
367 | backends will be tried (in the reverse order as given here). If none are |
419 | backends will be tried (in the reverse order as given here). If none are |
… | |
… | |
402 | Destroys the default loop again (frees all memory and kernel state |
454 | Destroys the default loop again (frees all memory and kernel state |
403 | etc.). None of the active event watchers will be stopped in the normal |
455 | etc.). None of the active event watchers will be stopped in the normal |
404 | sense, so e.g. C<ev_is_active> might still return true. It is your |
456 | sense, so e.g. C<ev_is_active> might still return true. It is your |
405 | responsibility to either stop all watchers cleanly yoursef I<before> |
457 | responsibility to either stop all watchers cleanly yoursef I<before> |
406 | calling this function, or cope with the fact afterwards (which is usually |
458 | calling this function, or cope with the fact afterwards (which is usually |
407 | the easiest thing, youc na just ignore the watchers and/or C<free ()> them |
459 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
408 | for example). |
460 | for example). |
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461 | |
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462 | Note that certain global state, such as signal state, will not be freed by |
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463 | this function, and related watchers (such as signal and child watchers) |
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464 | would need to be stopped manually. |
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465 | |
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466 | In general it is not advisable to call this function except in the |
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467 | rare occasion where you really need to free e.g. the signal handling |
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468 | pipe fds. If you need dynamically allocated loops it is better to use |
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469 | C<ev_loop_new> and C<ev_loop_destroy>). |
409 | |
470 | |
410 | =item ev_loop_destroy (loop) |
471 | =item ev_loop_destroy (loop) |
411 | |
472 | |
412 | Like C<ev_default_destroy>, but destroys an event loop created by an |
473 | Like C<ev_default_destroy>, but destroys an event loop created by an |
413 | earlier call to C<ev_loop_new>. |
474 | earlier call to C<ev_loop_new>. |
… | |
… | |
458 | |
519 | |
459 | Returns the current "event loop time", which is the time the event loop |
520 | Returns the current "event loop time", which is the time the event loop |
460 | received events and started processing them. This timestamp does not |
521 | received events and started processing them. This timestamp does not |
461 | change as long as callbacks are being processed, and this is also the base |
522 | change as long as callbacks are being processed, and this is also the base |
462 | time used for relative timers. You can treat it as the timestamp of the |
523 | time used for relative timers. You can treat it as the timestamp of the |
463 | event occuring (or more correctly, libev finding out about it). |
524 | event occurring (or more correctly, libev finding out about it). |
464 | |
525 | |
465 | =item ev_loop (loop, int flags) |
526 | =item ev_loop (loop, int flags) |
466 | |
527 | |
467 | Finally, this is it, the event handler. This function usually is called |
528 | Finally, this is it, the event handler. This function usually is called |
468 | after you initialised all your watchers and you want to start handling |
529 | after you initialised all your watchers and you want to start handling |
… | |
… | |
552 | Example: For some weird reason, unregister the above signal handler again. |
613 | Example: For some weird reason, unregister the above signal handler again. |
553 | |
614 | |
554 | ev_ref (loop); |
615 | ev_ref (loop); |
555 | ev_signal_stop (loop, &exitsig); |
616 | ev_signal_stop (loop, &exitsig); |
556 | |
617 | |
|
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618 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
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619 | |
|
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620 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
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621 | |
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622 | These advanced functions influence the time that libev will spend waiting |
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623 | for events. Both are by default C<0>, meaning that libev will try to |
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624 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
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625 | |
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626 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
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627 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
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628 | increase efficiency of loop iterations. |
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629 | |
|
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630 | The background is that sometimes your program runs just fast enough to |
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631 | handle one (or very few) event(s) per loop iteration. While this makes |
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632 | the program responsive, it also wastes a lot of CPU time to poll for new |
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633 | events, especially with backends like C<select ()> which have a high |
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634 | overhead for the actual polling but can deliver many events at once. |
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635 | |
|
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636 | By setting a higher I<io collect interval> you allow libev to spend more |
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637 | time collecting I/O events, so you can handle more events per iteration, |
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638 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
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639 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
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640 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
|
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641 | |
|
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642 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
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643 | to spend more time collecting timeouts, at the expense of increased |
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644 | latency (the watcher callback will be called later). C<ev_io> watchers |
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645 | will not be affected. Setting this to a non-null value will not introduce |
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646 | any overhead in libev. |
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647 | |
|
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648 | Many (busy) programs can usually benefit by setting the io collect |
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649 | interval to a value near C<0.1> or so, which is often enough for |
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650 | interactive servers (of course not for games), likewise for timeouts. It |
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651 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
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652 | as this approsaches the timing granularity of most systems. |
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653 | |
557 | =back |
654 | =back |
558 | |
655 | |
559 | |
656 | |
560 | =head1 ANATOMY OF A WATCHER |
657 | =head1 ANATOMY OF A WATCHER |
561 | |
658 | |
… | |
… | |
913 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1010 | such as poll (fortunately in our Xlib example, Xlib already does this on |
914 | its own, so its quite safe to use). |
1011 | its own, so its quite safe to use). |
915 | |
1012 | |
916 | =head3 The special problem of disappearing file descriptors |
1013 | =head3 The special problem of disappearing file descriptors |
917 | |
1014 | |
918 | Some backends (e.g kqueue, epoll) need to be told about closing a file |
1015 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
919 | descriptor (either by calling C<close> explicitly or by any other means, |
1016 | descriptor (either by calling C<close> explicitly or by any other means, |
920 | such as C<dup>). The reason is that you register interest in some file |
1017 | such as C<dup>). The reason is that you register interest in some file |
921 | descriptor, but when it goes away, the operating system will silently drop |
1018 | descriptor, but when it goes away, the operating system will silently drop |
922 | this interest. If another file descriptor with the same number then is |
1019 | this interest. If another file descriptor with the same number then is |
923 | registered with libev, there is no efficient way to see that this is, in |
1020 | registered with libev, there is no efficient way to see that this is, in |
… | |
… | |
931 | descriptor even if the file descriptor number itself did not change. |
1028 | descriptor even if the file descriptor number itself did not change. |
932 | |
1029 | |
933 | This is how one would do it normally anyway, the important point is that |
1030 | This is how one would do it normally anyway, the important point is that |
934 | the libev application should not optimise around libev but should leave |
1031 | the libev application should not optimise around libev but should leave |
935 | optimisations to libev. |
1032 | optimisations to libev. |
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1033 | |
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1034 | =head3 The special problem of dup'ed file descriptors |
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1035 | |
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1036 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1037 | but only events for the underlying file descriptions. That means when you |
|
|
1038 | have C<dup ()>'ed file descriptors and register events for them, only one |
|
|
1039 | file descriptor might actually receive events. |
|
|
1040 | |
|
|
1041 | There is no workaround possible except not registering events |
|
|
1042 | for potentially C<dup ()>'ed file descriptors, or to resort to |
|
|
1043 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
|
|
1044 | |
|
|
1045 | =head3 The special problem of fork |
|
|
1046 | |
|
|
1047 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
|
|
1048 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1049 | it in the child. |
|
|
1050 | |
|
|
1051 | To support fork in your programs, you either have to call |
|
|
1052 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
|
|
1053 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
|
|
1054 | C<EVBACKEND_POLL>. |
936 | |
1055 | |
937 | |
1056 | |
938 | =head3 Watcher-Specific Functions |
1057 | =head3 Watcher-Specific Functions |
939 | |
1058 | |
940 | =over 4 |
1059 | =over 4 |
… | |
… | |
1220 | |
1339 | |
1221 | The current reschedule callback, or C<0>, if this functionality is |
1340 | The current reschedule callback, or C<0>, if this functionality is |
1222 | switched off. Can be changed any time, but changes only take effect when |
1341 | switched off. Can be changed any time, but changes only take effect when |
1223 | the periodic timer fires or C<ev_periodic_again> is being called. |
1342 | the periodic timer fires or C<ev_periodic_again> is being called. |
1224 | |
1343 | |
|
|
1344 | =item ev_tstamp at [read-only] |
|
|
1345 | |
|
|
1346 | When active, contains the absolute time that the watcher is supposed to |
|
|
1347 | trigger next. |
|
|
1348 | |
1225 | =back |
1349 | =back |
1226 | |
1350 | |
1227 | Example: Call a callback every hour, or, more precisely, whenever the |
1351 | Example: Call a callback every hour, or, more precisely, whenever the |
1228 | system clock is divisible by 3600. The callback invocation times have |
1352 | system clock is divisible by 3600. The callback invocation times have |
1229 | potentially a lot of jittering, but good long-term stability. |
1353 | potentially a lot of jittering, but good long-term stability. |
… | |
… | |
1371 | reader). Inotify will be used to give hints only and should not change the |
1495 | reader). Inotify will be used to give hints only and should not change the |
1372 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1496 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1373 | to fall back to regular polling again even with inotify, but changes are |
1497 | to fall back to regular polling again even with inotify, but changes are |
1374 | usually detected immediately, and if the file exists there will be no |
1498 | usually detected immediately, and if the file exists there will be no |
1375 | polling. |
1499 | polling. |
|
|
1500 | |
|
|
1501 | =head3 The special problem of stat time resolution |
|
|
1502 | |
|
|
1503 | The C<stat ()> syscall only supports full-second resolution portably, and |
|
|
1504 | even on systems where the resolution is higher, many filesystems still |
|
|
1505 | only support whole seconds. |
|
|
1506 | |
|
|
1507 | That means that, if the time is the only thing that changes, you might |
|
|
1508 | miss updates: on the first update, C<ev_stat> detects a change and calls |
|
|
1509 | your callback, which does something. When there is another update within |
|
|
1510 | the same second, C<ev_stat> will be unable to detect it. |
|
|
1511 | |
|
|
1512 | The solution to this is to delay acting on a change for a second (or till |
|
|
1513 | the next second boundary), using a roughly one-second delay C<ev_timer> |
|
|
1514 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
|
|
1515 | is added to work around small timing inconsistencies of some operating |
|
|
1516 | systems. |
1376 | |
1517 | |
1377 | =head3 Watcher-Specific Functions and Data Members |
1518 | =head3 Watcher-Specific Functions and Data Members |
1378 | |
1519 | |
1379 | =over 4 |
1520 | =over 4 |
1380 | |
1521 | |
… | |
… | |
1440 | } |
1581 | } |
1441 | |
1582 | |
1442 | ... |
1583 | ... |
1443 | ev_stat passwd; |
1584 | ev_stat passwd; |
1444 | |
1585 | |
1445 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); |
1586 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
1446 | ev_stat_start (loop, &passwd); |
1587 | ev_stat_start (loop, &passwd); |
|
|
1588 | |
|
|
1589 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
1590 | miss updates (however, frequent updates will delay processing, too, so |
|
|
1591 | one might do the work both on C<ev_stat> callback invocation I<and> on |
|
|
1592 | C<ev_timer> callback invocation). |
|
|
1593 | |
|
|
1594 | static ev_stat passwd; |
|
|
1595 | static ev_timer timer; |
|
|
1596 | |
|
|
1597 | static void |
|
|
1598 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1599 | { |
|
|
1600 | ev_timer_stop (EV_A_ w); |
|
|
1601 | |
|
|
1602 | /* now it's one second after the most recent passwd change */ |
|
|
1603 | } |
|
|
1604 | |
|
|
1605 | static void |
|
|
1606 | stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
1607 | { |
|
|
1608 | /* reset the one-second timer */ |
|
|
1609 | ev_timer_again (EV_A_ &timer); |
|
|
1610 | } |
|
|
1611 | |
|
|
1612 | ... |
|
|
1613 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
|
|
1614 | ev_stat_start (loop, &passwd); |
|
|
1615 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
1447 | |
1616 | |
1448 | |
1617 | |
1449 | =head2 C<ev_idle> - when you've got nothing better to do... |
1618 | =head2 C<ev_idle> - when you've got nothing better to do... |
1450 | |
1619 | |
1451 | Idle watchers trigger events when no other events of the same or higher |
1620 | Idle watchers trigger events when no other events of the same or higher |
… | |
… | |
1537 | |
1706 | |
1538 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1707 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1539 | priority, to ensure that they are being run before any other watchers |
1708 | priority, to ensure that they are being run before any other watchers |
1540 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1709 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1541 | too) should not activate ("feed") events into libev. While libev fully |
1710 | too) should not activate ("feed") events into libev. While libev fully |
1542 | supports this, they will be called before other C<ev_check> watchers did |
1711 | supports this, they will be called before other C<ev_check> watchers |
1543 | their job. As C<ev_check> watchers are often used to embed other event |
1712 | did their job. As C<ev_check> watchers are often used to embed other |
1544 | loops those other event loops might be in an unusable state until their |
1713 | (non-libev) event loops those other event loops might be in an unusable |
1545 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1714 | state until their C<ev_check> watcher ran (always remind yourself to |
1546 | others). |
1715 | coexist peacefully with others). |
1547 | |
1716 | |
1548 | =head3 Watcher-Specific Functions and Data Members |
1717 | =head3 Watcher-Specific Functions and Data Members |
1549 | |
1718 | |
1550 | =over 4 |
1719 | =over 4 |
1551 | |
1720 | |
… | |
… | |
1775 | |
1944 | |
1776 | Make a single, non-blocking sweep over the embedded loop. This works |
1945 | Make a single, non-blocking sweep over the embedded loop. This works |
1777 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
1946 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
1778 | apropriate way for embedded loops. |
1947 | apropriate way for embedded loops. |
1779 | |
1948 | |
1780 | =item struct ev_loop *loop [read-only] |
1949 | =item struct ev_loop *other [read-only] |
1781 | |
1950 | |
1782 | The embedded event loop. |
1951 | The embedded event loop. |
1783 | |
1952 | |
1784 | =back |
1953 | =back |
1785 | |
1954 | |
… | |
… | |
1792 | event loop blocks next and before C<ev_check> watchers are being called, |
1961 | event loop blocks next and before C<ev_check> watchers are being called, |
1793 | and only in the child after the fork. If whoever good citizen calling |
1962 | and only in the child after the fork. If whoever good citizen calling |
1794 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
1963 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
1795 | handlers will be invoked, too, of course. |
1964 | handlers will be invoked, too, of course. |
1796 | |
1965 | |
|
|
1966 | =head3 Watcher-Specific Functions and Data Members |
|
|
1967 | |
1797 | =over 4 |
1968 | =over 4 |
1798 | |
1969 | |
1799 | =item ev_fork_init (ev_signal *, callback) |
1970 | =item ev_fork_init (ev_signal *, callback) |
1800 | |
1971 | |
1801 | Initialises and configures the fork watcher - it has no parameters of any |
1972 | Initialises and configures the fork watcher - it has no parameters of any |
… | |
… | |
2017 | |
2188 | |
2018 | =item w->stop () |
2189 | =item w->stop () |
2019 | |
2190 | |
2020 | Stops the watcher if it is active. Again, no C<loop> argument. |
2191 | Stops the watcher if it is active. Again, no C<loop> argument. |
2021 | |
2192 | |
2022 | =item w->again () C<ev::timer>, C<ev::periodic> only |
2193 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
2023 | |
2194 | |
2024 | For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
2195 | For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
2025 | C<ev_TYPE_again> function. |
2196 | C<ev_TYPE_again> function. |
2026 | |
2197 | |
2027 | =item w->sweep () C<ev::embed> only |
2198 | =item w->sweep () (C<ev::embed> only) |
2028 | |
2199 | |
2029 | Invokes C<ev_embed_sweep>. |
2200 | Invokes C<ev_embed_sweep>. |
2030 | |
2201 | |
2031 | =item w->update () C<ev::stat> only |
2202 | =item w->update () (C<ev::stat> only) |
2032 | |
2203 | |
2033 | Invokes C<ev_stat_stat>. |
2204 | Invokes C<ev_stat_stat>. |
2034 | |
2205 | |
2035 | =back |
2206 | =back |
2036 | |
2207 | |
… | |
… | |
2056 | } |
2227 | } |
2057 | |
2228 | |
2058 | |
2229 | |
2059 | =head1 MACRO MAGIC |
2230 | =head1 MACRO MAGIC |
2060 | |
2231 | |
2061 | Libev can be compiled with a variety of options, the most fundemantal is |
2232 | Libev can be compiled with a variety of options, the most fundamantal |
2062 | C<EV_MULTIPLICITY>. This option determines whether (most) functions and |
2233 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2063 | callbacks have an initial C<struct ev_loop *> argument. |
2234 | functions and callbacks have an initial C<struct ev_loop *> argument. |
2064 | |
2235 | |
2065 | To make it easier to write programs that cope with either variant, the |
2236 | To make it easier to write programs that cope with either variant, the |
2066 | following macros are defined: |
2237 | following macros are defined: |
2067 | |
2238 | |
2068 | =over 4 |
2239 | =over 4 |
… | |
… | |
2122 | Libev can (and often is) directly embedded into host |
2293 | Libev can (and often is) directly embedded into host |
2123 | applications. Examples of applications that embed it include the Deliantra |
2294 | applications. Examples of applications that embed it include the Deliantra |
2124 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
2295 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
2125 | and rxvt-unicode. |
2296 | and rxvt-unicode. |
2126 | |
2297 | |
2127 | The goal is to enable you to just copy the neecssary files into your |
2298 | The goal is to enable you to just copy the necessary files into your |
2128 | source directory without having to change even a single line in them, so |
2299 | source directory without having to change even a single line in them, so |
2129 | you can easily upgrade by simply copying (or having a checked-out copy of |
2300 | you can easily upgrade by simply copying (or having a checked-out copy of |
2130 | libev somewhere in your source tree). |
2301 | libev somewhere in your source tree). |
2131 | |
2302 | |
2132 | =head2 FILESETS |
2303 | =head2 FILESETS |
… | |
… | |
2222 | |
2393 | |
2223 | If defined to be C<1>, libev will try to detect the availability of the |
2394 | If defined to be C<1>, libev will try to detect the availability of the |
2224 | monotonic clock option at both compiletime and runtime. Otherwise no use |
2395 | monotonic clock option at both compiletime and runtime. Otherwise no use |
2225 | of the monotonic clock option will be attempted. If you enable this, you |
2396 | of the monotonic clock option will be attempted. If you enable this, you |
2226 | usually have to link against librt or something similar. Enabling it when |
2397 | usually have to link against librt or something similar. Enabling it when |
2227 | the functionality isn't available is safe, though, althoguh you have |
2398 | the functionality isn't available is safe, though, although you have |
2228 | to make sure you link against any libraries where the C<clock_gettime> |
2399 | to make sure you link against any libraries where the C<clock_gettime> |
2229 | function is hiding in (often F<-lrt>). |
2400 | function is hiding in (often F<-lrt>). |
2230 | |
2401 | |
2231 | =item EV_USE_REALTIME |
2402 | =item EV_USE_REALTIME |
2232 | |
2403 | |
2233 | If defined to be C<1>, libev will try to detect the availability of the |
2404 | If defined to be C<1>, libev will try to detect the availability of the |
2234 | realtime clock option at compiletime (and assume its availability at |
2405 | realtime clock option at compiletime (and assume its availability at |
2235 | runtime if successful). Otherwise no use of the realtime clock option will |
2406 | runtime if successful). Otherwise no use of the realtime clock option will |
2236 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
2407 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
2237 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries |
2408 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
2238 | in the description of C<EV_USE_MONOTONIC>, though. |
2409 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
|
|
2410 | |
|
|
2411 | =item EV_USE_NANOSLEEP |
|
|
2412 | |
|
|
2413 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
|
|
2414 | and will use it for delays. Otherwise it will use C<select ()>. |
2239 | |
2415 | |
2240 | =item EV_USE_SELECT |
2416 | =item EV_USE_SELECT |
2241 | |
2417 | |
2242 | If undefined or defined to be C<1>, libev will compile in support for the |
2418 | If undefined or defined to be C<1>, libev will compile in support for the |
2243 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2419 | C<select>(2) backend. No attempt at autodetection will be done: if no |
… | |
… | |
2395 | than enough. If you need to manage thousands of children you might want to |
2571 | than enough. If you need to manage thousands of children you might want to |
2396 | increase this value (I<must> be a power of two). |
2572 | increase this value (I<must> be a power of two). |
2397 | |
2573 | |
2398 | =item EV_INOTIFY_HASHSIZE |
2574 | =item EV_INOTIFY_HASHSIZE |
2399 | |
2575 | |
2400 | C<ev_staz> watchers use a small hash table to distribute workload by |
2576 | C<ev_stat> watchers use a small hash table to distribute workload by |
2401 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2577 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2402 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2578 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2403 | watchers you might want to increase this value (I<must> be a power of |
2579 | watchers you might want to increase this value (I<must> be a power of |
2404 | two). |
2580 | two). |
2405 | |
2581 | |
… | |
… | |
2422 | |
2598 | |
2423 | =item ev_set_cb (ev, cb) |
2599 | =item ev_set_cb (ev, cb) |
2424 | |
2600 | |
2425 | Can be used to change the callback member declaration in each watcher, |
2601 | Can be used to change the callback member declaration in each watcher, |
2426 | and the way callbacks are invoked and set. Must expand to a struct member |
2602 | and the way callbacks are invoked and set. Must expand to a struct member |
2427 | definition and a statement, respectively. See the F<ev.v> header file for |
2603 | definition and a statement, respectively. See the F<ev.h> header file for |
2428 | their default definitions. One possible use for overriding these is to |
2604 | their default definitions. One possible use for overriding these is to |
2429 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
2605 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
2430 | method calls instead of plain function calls in C++. |
2606 | method calls instead of plain function calls in C++. |
|
|
2607 | |
|
|
2608 | =head2 EXPORTED API SYMBOLS |
|
|
2609 | |
|
|
2610 | If you need to re-export the API (e.g. via a dll) and you need a list of |
|
|
2611 | exported symbols, you can use the provided F<Symbol.*> files which list |
|
|
2612 | all public symbols, one per line: |
|
|
2613 | |
|
|
2614 | Symbols.ev for libev proper |
|
|
2615 | Symbols.event for the libevent emulation |
|
|
2616 | |
|
|
2617 | This can also be used to rename all public symbols to avoid clashes with |
|
|
2618 | multiple versions of libev linked together (which is obviously bad in |
|
|
2619 | itself, but sometimes it is inconvinient to avoid this). |
|
|
2620 | |
|
|
2621 | A sed command like this will create wrapper C<#define>'s that you need to |
|
|
2622 | include before including F<ev.h>: |
|
|
2623 | |
|
|
2624 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
|
|
2625 | |
|
|
2626 | This would create a file F<wrap.h> which essentially looks like this: |
|
|
2627 | |
|
|
2628 | #define ev_backend myprefix_ev_backend |
|
|
2629 | #define ev_check_start myprefix_ev_check_start |
|
|
2630 | #define ev_check_stop myprefix_ev_check_stop |
|
|
2631 | ... |
2431 | |
2632 | |
2432 | =head2 EXAMPLES |
2633 | =head2 EXAMPLES |
2433 | |
2634 | |
2434 | For a real-world example of a program the includes libev |
2635 | For a real-world example of a program the includes libev |
2435 | verbatim, you can have a look at the EV perl module |
2636 | verbatim, you can have a look at the EV perl module |
… | |
… | |
2476 | |
2677 | |
2477 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
2678 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
2478 | |
2679 | |
2479 | This means that, when you have a watcher that triggers in one hour and |
2680 | This means that, when you have a watcher that triggers in one hour and |
2480 | there are 100 watchers that would trigger before that then inserting will |
2681 | there are 100 watchers that would trigger before that then inserting will |
2481 | have to skip those 100 watchers. |
2682 | have to skip roughly seven (C<ld 100>) of these watchers. |
2482 | |
2683 | |
2483 | =item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) |
2684 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
2484 | |
2685 | |
2485 | That means that for changing a timer costs less than removing/adding them |
2686 | That means that changing a timer costs less than removing/adding them |
2486 | as only the relative motion in the event queue has to be paid for. |
2687 | as only the relative motion in the event queue has to be paid for. |
2487 | |
2688 | |
2488 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
2689 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
2489 | |
2690 | |
2490 | These just add the watcher into an array or at the head of a list. |
2691 | These just add the watcher into an array or at the head of a list. |
|
|
2692 | |
2491 | =item Stopping check/prepare/idle watchers: O(1) |
2693 | =item Stopping check/prepare/idle watchers: O(1) |
2492 | |
2694 | |
2493 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2695 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2494 | |
2696 | |
2495 | These watchers are stored in lists then need to be walked to find the |
2697 | These watchers are stored in lists then need to be walked to find the |
2496 | correct watcher to remove. The lists are usually short (you don't usually |
2698 | correct watcher to remove. The lists are usually short (you don't usually |
2497 | have many watchers waiting for the same fd or signal). |
2699 | have many watchers waiting for the same fd or signal). |
2498 | |
2700 | |
2499 | =item Finding the next timer per loop iteration: O(1) |
2701 | =item Finding the next timer in each loop iteration: O(1) |
|
|
2702 | |
|
|
2703 | By virtue of using a binary heap, the next timer is always found at the |
|
|
2704 | beginning of the storage array. |
2500 | |
2705 | |
2501 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2706 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2502 | |
2707 | |
2503 | A change means an I/O watcher gets started or stopped, which requires |
2708 | A change means an I/O watcher gets started or stopped, which requires |
2504 | libev to recalculate its status (and possibly tell the kernel). |
2709 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
2710 | on backend and wether C<ev_io_set> was used). |
2505 | |
2711 | |
2506 | =item Activating one watcher: O(1) |
2712 | =item Activating one watcher (putting it into the pending state): O(1) |
2507 | |
2713 | |
2508 | =item Priority handling: O(number_of_priorities) |
2714 | =item Priority handling: O(number_of_priorities) |
2509 | |
2715 | |
2510 | Priorities are implemented by allocating some space for each |
2716 | Priorities are implemented by allocating some space for each |
2511 | priority. When doing priority-based operations, libev usually has to |
2717 | priority. When doing priority-based operations, libev usually has to |
2512 | linearly search all the priorities. |
2718 | linearly search all the priorities, but starting/stopping and activating |
|
|
2719 | watchers becomes O(1) w.r.t. prioritiy handling. |
2513 | |
2720 | |
2514 | =back |
2721 | =back |
2515 | |
2722 | |
2516 | |
2723 | |
2517 | =head1 AUTHOR |
2724 | =head1 AUTHOR |