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Revision 1.130 by root, Wed Feb 6 18:34:24 2008 UTC

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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;
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65You register interest in certain events by registering so-called I<event 65You register interest in certain events by registering so-called I<event
66watchers>, which are relatively small C structures you initialise with the 66watchers>, which are relatively small C structures you initialise with the
67details of the event, and then hand it over to libev by I<starting> the 67details of the event, and then hand it over to libev by I<starting> the
68watcher. 68watcher.
69 69
70=head1 FEATURES 70=head2 FEATURES
71 71
72Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the 72Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73BSD-specific C<kqueue> and the Solaris-specific event port mechanisms 73BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74for file descriptor events (C<ev_io>), the Linux C<inotify> interface 74for 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
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82 82
83It also is quite fast (see this 83It also is quite fast (see this
84L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent 84L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85for example). 85for example).
86 86
87=head1 CONVENTIONS 87=head2 CONVENTIONS
88 88
89Libev is very configurable. In this manual the default configuration will 89Libev is very configurable. In this manual the default configuration will
90be described, which supports multiple event loops. For more info about 90be described, which supports multiple event loops. For more info about
91various configuration options please have a look at B<EMBED> section in 91various configuration options please have a look at B<EMBED> section in
92this manual. If libev was configured without support for multiple event 92this manual. If libev was configured without support for multiple event
93loops, then all functions taking an initial argument of name C<loop> 93loops, 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
98Libev represents time as a single floating point number, representing the 98Libev 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
100the beginning of 1970, details are complicated, don't ask). This type is 100the beginning of 1970, details are complicated, don't ask). This type is
101called C<ev_tstamp>, which is what you should use too. It usually aliases 101called C<ev_tstamp>, which is what you should use too. It usually aliases
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260flags. If that is troubling you, check C<ev_backend ()> afterwards). 260flags. If that is troubling you, check C<ev_backend ()> afterwards).
261 261
262If you don't know what event loop to use, use the one returned from this 262If you don't know what event loop to use, use the one returned from this
263function. 263function.
264 264
265The default loop is the only loop that can handle C<ev_signal> and
266C<ev_child> watchers, and to do this, it always registers a handler
267for C<SIGCHLD>. If this is a problem for your app you can either
268create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
269can simply overwrite the C<SIGCHLD> signal handler I<after> calling
270C<ev_default_init>.
271
265The flags argument can be used to specify special behaviour or specific 272The flags argument can be used to specify special behaviour or specific
266backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). 273backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267 274
268The following flags are supported: 275The following flags are supported:
269 276
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306=item C<EVBACKEND_SELECT> (value 1, portable select backend) 313=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307 314
308This is your standard select(2) backend. Not I<completely> standard, as 315This is your standard select(2) backend. Not I<completely> standard, as
309libev tries to roll its own fd_set with no limits on the number of fds, 316libev tries to roll its own fd_set with no limits on the number of fds,
310but if that fails, expect a fairly low limit on the number of fds when 317but if that fails, expect a fairly low limit on the number of fds when
311using this backend. It doesn't scale too well (O(highest_fd)), but its usually 318using this backend. It doesn't scale too well (O(highest_fd)), but its
312the fastest backend for a low number of fds. 319usually the fastest backend for a low number of (low-numbered :) fds.
320
321To get good performance out of this backend you need a high amount of
322parallelity (most of the file descriptors should be busy). If you are
323writing a server, you should C<accept ()> in a loop to accept as many
324connections as possible during one iteration. You might also want to have
325a look at C<ev_set_io_collect_interval ()> to increase the amount of
326readyness notifications you get per iteration.
313 327
314=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) 328=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
315 329
316And this is your standard poll(2) backend. It's more complicated than 330And this is your standard poll(2) backend. It's more complicated
317select, but handles sparse fds better and has no artificial limit on the 331than select, but handles sparse fds better and has no artificial
318number of fds you can use (except it will slow down considerably with a 332limit on the number of fds you can use (except it will slow down
319lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 333considerably with a lot of inactive fds). It scales similarly to select,
334i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
335performance tips.
320 336
321=item C<EVBACKEND_EPOLL> (value 4, Linux) 337=item C<EVBACKEND_EPOLL> (value 4, Linux)
322 338
323For few fds, this backend is a bit little slower than poll and select, 339For few fds, this backend is a bit little slower than poll and select,
324but it scales phenomenally better. While poll and select usually scale 340but it scales phenomenally better. While poll and select usually scale
325like O(total_fds) where n is the total number of fds (or the highest fd), 341like O(total_fds) where n is the total number of fds (or the highest fd),
326epoll scales either O(1) or O(active_fds). The epoll design has a number 342epoll scales either O(1) or O(active_fds). The epoll design has a number
327of shortcomings, such as silently dropping events in some hard-to-detect 343of shortcomings, such as silently dropping events in some hard-to-detect
328cases and rewiring a syscall per fd change, no fork support and bad 344cases and rewiring a syscall per fd change, no fork support and bad
329support for dup: 345support for dup.
330 346
331While stopping, setting and starting an I/O watcher in the same iteration 347While stopping, setting and starting an I/O watcher in the same iteration
332will result in some caching, there is still a syscall per such incident 348will result in some caching, there is still a syscall per such incident
333(because the fd could point to a different file description now), so its 349(because the fd could point to a different file description now), so its
334best to avoid that. Also, C<dup ()>'ed file descriptors might not work 350best to avoid that. Also, C<dup ()>'ed file descriptors might not work
335very well if you register events for both fds. 351very well if you register events for both fds.
336 352
337Please note that epoll sometimes generates spurious notifications, so you 353Please note that epoll sometimes generates spurious notifications, so you
338need to use non-blocking I/O or other means to avoid blocking when no data 354need to use non-blocking I/O or other means to avoid blocking when no data
339(or space) is available. 355(or space) is available.
356
357Best performance from this backend is achieved by not unregistering all
358watchers for a file descriptor until it has been closed, if possible, i.e.
359keep at least one watcher active per fd at all times.
360
361While nominally embeddeble in other event loops, this feature is broken in
362all kernel versions tested so far.
340 363
341=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) 364=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
342 365
343Kqueue deserves special mention, as at the time of this writing, it 366Kqueue deserves special mention, as at the time of this writing, it
344was broken on all BSDs except NetBSD (usually it doesn't work reliably 367was broken on all BSDs except NetBSD (usually it doesn't work reliably
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357course). While stopping, setting and starting an I/O watcher does never 380course). While stopping, setting and starting an I/O watcher does never
358cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to 381cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
359two event changes per incident, support for C<fork ()> is very bad and it 382two event changes per incident, support for C<fork ()> is very bad and it
360drops fds silently in similarly hard-to-detect cases. 383drops fds silently in similarly hard-to-detect cases.
361 384
385This backend usually performs well under most conditions.
386
387While nominally embeddable in other event loops, this doesn't work
388everywhere, so you might need to test for this. And since it is broken
389almost everywhere, you should only use it when you have a lot of sockets
390(for which it usually works), by embedding it into another event loop
391(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
392sockets.
393
362=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) 394=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
363 395
364This is not implemented yet (and might never be). 396This is not implemented yet (and might never be, unless you send me an
397implementation). According to reports, C</dev/poll> only supports sockets
398and is not embeddable, which would limit the usefulness of this backend
399immensely.
365 400
366=item C<EVBACKEND_PORT> (value 32, Solaris 10) 401=item C<EVBACKEND_PORT> (value 32, Solaris 10)
367 402
368This uses the Solaris 10 event port mechanism. As with everything on Solaris, 403This uses the Solaris 10 event port mechanism. As with everything on Solaris,
369it's really slow, but it still scales very well (O(active_fds)). 404it's really slow, but it still scales very well (O(active_fds)).
370 405
371Please note that solaris event ports can deliver a lot of spurious 406Please note that solaris event ports can deliver a lot of spurious
372notifications, so you need to use non-blocking I/O or other means to avoid 407notifications, so you need to use non-blocking I/O or other means to avoid
373blocking when no data (or space) is available. 408blocking when no data (or space) is available.
374 409
410While this backend scales well, it requires one system call per active
411file descriptor per loop iteration. For small and medium numbers of file
412descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
413might perform better.
414
415On the positive side, ignoring the spurious readyness notifications, this
416backend actually performed to specification in all tests and is fully
417embeddable, which is a rare feat among the OS-specific backends.
418
375=item C<EVBACKEND_ALL> 419=item C<EVBACKEND_ALL>
376 420
377Try all backends (even potentially broken ones that wouldn't be tried 421Try all backends (even potentially broken ones that wouldn't be tried
378with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as 422with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
379C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. 423C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
380 424
425It is definitely not recommended to use this flag.
426
381=back 427=back
382 428
383If one or more of these are ored into the flags value, then only these 429If one or more of these are ored into the flags value, then only these
384backends will be tried (in the reverse order as given here). If none are 430backends will be tried (in the reverse order as listed here). If none are
385specified, most compiled-in backend will be tried, usually in reverse 431specified, all backends in C<ev_recommended_backends ()> will be tried.
386order of their flag values :)
387 432
388The most typical usage is like this: 433The most typical usage is like this:
389 434
390 if (!ev_default_loop (0)) 435 if (!ev_default_loop (0))
391 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); 436 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
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438Like C<ev_default_destroy>, but destroys an event loop created by an 483Like C<ev_default_destroy>, but destroys an event loop created by an
439earlier call to C<ev_loop_new>. 484earlier call to C<ev_loop_new>.
440 485
441=item ev_default_fork () 486=item ev_default_fork ()
442 487
488This function sets a flag that causes subsequent C<ev_loop> iterations
443This function reinitialises the kernel state for backends that have 489to reinitialise the kernel state for backends that have one. Despite the
444one. Despite the name, you can call it anytime, but it makes most sense 490name, you can call it anytime, but it makes most sense after forking, in
445after forking, in either the parent or child process (or both, but that 491the child process (or both child and parent, but that again makes little
446again makes little sense). 492sense). You I<must> call it in the child before using any of the libev
493functions, and it will only take effect at the next C<ev_loop> iteration.
447 494
448You I<must> call this function in the child process after forking if and 495On the other hand, you only need to call this function in the child
449only if you want to use the event library in both processes. If you just 496process if and only if you want to use the event library in the child. If
450fork+exec, you don't have to call it. 497you just fork+exec, you don't have to call it at all.
451 498
452The function itself is quite fast and it's usually not a problem to call 499The function itself is quite fast and it's usually not a problem to call
453it just in case after a fork. To make this easy, the function will fit in 500it just in case after a fork. To make this easy, the function will fit in
454quite nicely into a call to C<pthread_atfork>: 501quite nicely into a call to C<pthread_atfork>:
455 502
456 pthread_atfork (0, 0, ev_default_fork); 503 pthread_atfork (0, 0, ev_default_fork);
457
458At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
459without calling this function, so if you force one of those backends you
460do not need to care.
461 504
462=item ev_loop_fork (loop) 505=item ev_loop_fork (loop)
463 506
464Like C<ev_default_fork>, but acts on an event loop created by 507Like C<ev_default_fork>, but acts on an event loop created by
465C<ev_loop_new>. Yes, you have to call this on every allocated event loop 508C<ev_loop_new>. Yes, you have to call this on every allocated event loop
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516usually a better approach for this kind of thing. 559usually a better approach for this kind of thing.
517 560
518Here are the gory details of what C<ev_loop> does: 561Here are the gory details of what C<ev_loop> does:
519 562
520 - Before the first iteration, call any pending watchers. 563 - Before the first iteration, call any pending watchers.
521 * If there are no active watchers (reference count is zero), return. 564 * If EVFLAG_FORKCHECK was used, check for a fork.
522 - Queue all prepare watchers and then call all outstanding watchers. 565 - If a fork was detected, queue and call all fork watchers.
566 - Queue and call all prepare watchers.
523 - If we have been forked, recreate the kernel state. 567 - If we have been forked, recreate the kernel state.
524 - Update the kernel state with all outstanding changes. 568 - Update the kernel state with all outstanding changes.
525 - Update the "event loop time". 569 - Update the "event loop time".
526 - Calculate for how long to block. 570 - Calculate for how long to sleep or block, if at all
571 (active idle watchers, EVLOOP_NONBLOCK or not having
572 any active watchers at all will result in not sleeping).
573 - Sleep if the I/O and timer collect interval say so.
527 - Block the process, waiting for any events. 574 - Block the process, waiting for any events.
528 - Queue all outstanding I/O (fd) events. 575 - Queue all outstanding I/O (fd) events.
529 - Update the "event loop time" and do time jump handling. 576 - Update the "event loop time" and do time jump handling.
530 - Queue all outstanding timers. 577 - Queue all outstanding timers.
531 - Queue all outstanding periodics. 578 - Queue all outstanding periodics.
532 - If no events are pending now, queue all idle watchers. 579 - If no events are pending now, queue all idle watchers.
533 - Queue all check watchers. 580 - Queue all check watchers.
534 - Call all queued watchers in reverse order (i.e. check watchers first). 581 - Call all queued watchers in reverse order (i.e. check watchers first).
535 Signals and child watchers are implemented as I/O watchers, and will 582 Signals and child watchers are implemented as I/O watchers, and will
536 be handled here by queueing them when their watcher gets executed. 583 be handled here by queueing them when their watcher gets executed.
537 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 584 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
538 were used, return, otherwise continue with step *. 585 were used, or there are no active watchers, return, otherwise
586 continue with step *.
539 587
540Example: Queue some jobs and then loop until no events are outsanding 588Example: Queue some jobs and then loop until no events are outstanding
541anymore. 589anymore.
542 590
543 ... queue jobs here, make sure they register event watchers as long 591 ... queue jobs here, make sure they register event watchers as long
544 ... as they still have work to do (even an idle watcher will do..) 592 ... as they still have work to do (even an idle watcher will do..)
545 ev_loop (my_loop, 0); 593 ev_loop (my_loop, 0);
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549 597
550Can be used to make a call to C<ev_loop> return early (but only after it 598Can be used to make a call to C<ev_loop> return early (but only after it
551has processed all outstanding events). The C<how> argument must be either 599has processed all outstanding events). The C<how> argument must be either
552C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or 600C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
553C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. 601C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
602
603This "unloop state" will be cleared when entering C<ev_loop> again.
554 604
555=item ev_ref (loop) 605=item ev_ref (loop)
556 606
557=item ev_unref (loop) 607=item ev_unref (loop)
558 608
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563returning, ev_unref() after starting, and ev_ref() before stopping it. For 613returning, ev_unref() after starting, and ev_ref() before stopping it. For
564example, libev itself uses this for its internal signal pipe: It is not 614example, libev itself uses this for its internal signal pipe: It is not
565visible to the libev user and should not keep C<ev_loop> from exiting if 615visible to the libev user and should not keep C<ev_loop> from exiting if
566no event watchers registered by it are active. It is also an excellent 616no event watchers registered by it are active. It is also an excellent
567way to do this for generic recurring timers or from within third-party 617way to do this for generic recurring timers or from within third-party
568libraries. Just remember to I<unref after start> and I<ref before stop>. 618libraries. Just remember to I<unref after start> and I<ref before stop>
619(but only if the watcher wasn't active before, or was active before,
620respectively).
569 621
570Example: Create a signal watcher, but keep it from keeping C<ev_loop> 622Example: Create a signal watcher, but keep it from keeping C<ev_loop>
571running when nothing else is active. 623running when nothing else is active.
572 624
573 struct ev_signal exitsig; 625 struct ev_signal exitsig;
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599overhead for the actual polling but can deliver many events at once. 651overhead for the actual polling but can deliver many events at once.
600 652
601By setting a higher I<io collect interval> you allow libev to spend more 653By setting a higher I<io collect interval> you allow libev to spend more
602time collecting I/O events, so you can handle more events per iteration, 654time collecting I/O events, so you can handle more events per iteration,
603at the cost of increasing latency. Timeouts (both C<ev_periodic> and 655at the cost of increasing latency. Timeouts (both C<ev_periodic> and
604C<ev_timer>) will be not affected. Setting this to a non-null bvalue will 656C<ev_timer>) will be not affected. Setting this to a non-null value will
605introduce an additional C<ev_sleep ()> call into most loop iterations. 657introduce an additional C<ev_sleep ()> call into most loop iterations.
606 658
607Likewise, by setting a higher I<timeout collect interval> you allow libev 659Likewise, by setting a higher I<timeout collect interval> you allow libev
608to spend more time collecting timeouts, at the expense of increased 660to spend more time collecting timeouts, at the expense of increased
609latency (the watcher callback will be called later). C<ev_io> watchers 661latency (the watcher callback will be called later). C<ev_io> watchers
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721 773
722=item C<EV_FORK> 774=item C<EV_FORK>
723 775
724The event loop has been resumed in the child process after fork (see 776The event loop has been resumed in the child process after fork (see
725C<ev_fork>). 777C<ev_fork>).
778
779=item C<EV_ASYNC>
780
781The given async watcher has been asynchronously notified (see C<ev_async>).
726 782
727=item C<EV_ERROR> 783=item C<EV_ERROR>
728 784
729An unspecified error has occured, the watcher has been stopped. This might 785An unspecified error has occured, the watcher has been stopped. This might
730happen because the watcher could not be properly started because libev 786happen because the watcher could not be properly started because libev
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948In general you can register as many read and/or write event watchers per 1004In general you can register as many read and/or write event watchers per
949fd as you want (as long as you don't confuse yourself). Setting all file 1005fd as you want (as long as you don't confuse yourself). Setting all file
950descriptors to non-blocking mode is also usually a good idea (but not 1006descriptors to non-blocking mode is also usually a good idea (but not
951required if you know what you are doing). 1007required if you know what you are doing).
952 1008
953You have to be careful with dup'ed file descriptors, though. Some backends
954(the linux epoll backend is a notable example) cannot handle dup'ed file
955descriptors correctly if you register interest in two or more fds pointing
956to the same underlying file/socket/etc. description (that is, they share
957the same underlying "file open").
958
959If you must do this, then force the use of a known-to-be-good backend 1009If you must do this, then force the use of a known-to-be-good backend
960(at the time of this writing, this includes only C<EVBACKEND_SELECT> and 1010(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
961C<EVBACKEND_POLL>). 1011C<EVBACKEND_POLL>).
962 1012
963Another thing you have to watch out for is that it is quite easy to 1013Another thing you have to watch out for is that it is quite easy to
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997optimisations to libev. 1047optimisations to libev.
998 1048
999=head3 The special problem of dup'ed file descriptors 1049=head3 The special problem of dup'ed file descriptors
1000 1050
1001Some backends (e.g. epoll), cannot register events for file descriptors, 1051Some backends (e.g. epoll), cannot register events for file descriptors,
1002but only events for the underlying file descriptions. That menas when you 1052but only events for the underlying file descriptions. That means when you
1003have C<dup ()>'ed file descriptors and register events for them, only one 1053have C<dup ()>'ed file descriptors or weirder constellations, and register
1004file descriptor might actually receive events. 1054events for them, only one file descriptor might actually receive events.
1005 1055
1006There is no workaorund possible except not registering events 1056There is no workaround possible except not registering events
1007for potentially C<dup ()>'ed file descriptors or to resort to 1057for potentially C<dup ()>'ed file descriptors, or to resort to
1008C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. 1058C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1009 1059
1010=head3 The special problem of fork 1060=head3 The special problem of fork
1011 1061
1012Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit 1062Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
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1038=item int events [read-only] 1088=item int events [read-only]
1039 1089
1040The events being watched. 1090The events being watched.
1041 1091
1042=back 1092=back
1093
1094=head3 Examples
1043 1095
1044Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1096Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1045readable, but only once. Since it is likely line-buffered, you could 1097readable, but only once. Since it is likely line-buffered, you could
1046attempt to read a whole line in the callback. 1098attempt to read a whole line in the callback.
1047 1099
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1145or C<ev_timer_again> is called and determines the next timeout (if any), 1197or C<ev_timer_again> is called and determines the next timeout (if any),
1146which is also when any modifications are taken into account. 1198which is also when any modifications are taken into account.
1147 1199
1148=back 1200=back
1149 1201
1202=head3 Examples
1203
1150Example: Create a timer that fires after 60 seconds. 1204Example: Create a timer that fires after 60 seconds.
1151 1205
1152 static void 1206 static void
1153 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1207 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1154 { 1208 {
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1311When active, contains the absolute time that the watcher is supposed to 1365When active, contains the absolute time that the watcher is supposed to
1312trigger next. 1366trigger next.
1313 1367
1314=back 1368=back
1315 1369
1370=head3 Examples
1371
1316Example: Call a callback every hour, or, more precisely, whenever the 1372Example: Call a callback every hour, or, more precisely, whenever the
1317system clock is divisible by 3600. The callback invocation times have 1373system clock is divisible by 3600. The callback invocation times have
1318potentially a lot of jittering, but good long-term stability. 1374potentially a lot of jittering, but good long-term stability.
1319 1375
1320 static void 1376 static void
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1386 1442
1387=head3 Watcher-Specific Functions and Data Members 1443=head3 Watcher-Specific Functions and Data Members
1388 1444
1389=over 4 1445=over 4
1390 1446
1391=item ev_child_init (ev_child *, callback, int pid) 1447=item ev_child_init (ev_child *, callback, int pid, int trace)
1392 1448
1393=item ev_child_set (ev_child *, int pid) 1449=item ev_child_set (ev_child *, int pid, int trace)
1394 1450
1395Configures the watcher to wait for status changes of process C<pid> (or 1451Configures the watcher to wait for status changes of process C<pid> (or
1396I<any> process if C<pid> is specified as C<0>). The callback can look 1452I<any> process if C<pid> is specified as C<0>). The callback can look
1397at the C<rstatus> member of the C<ev_child> watcher structure to see 1453at the C<rstatus> member of the C<ev_child> watcher structure to see
1398the status word (use the macros from C<sys/wait.h> and see your systems 1454the status word (use the macros from C<sys/wait.h> and see your systems
1399C<waitpid> documentation). The C<rpid> member contains the pid of the 1455C<waitpid> documentation). The C<rpid> member contains the pid of the
1400process causing the status change. 1456process causing the status change. C<trace> must be either C<0> (only
1457activate the watcher when the process terminates) or C<1> (additionally
1458activate the watcher when the process is stopped or continued).
1401 1459
1402=item int pid [read-only] 1460=item int pid [read-only]
1403 1461
1404The process id this watcher watches out for, or C<0>, meaning any process id. 1462The process id this watcher watches out for, or C<0>, meaning any process id.
1405 1463
… …
1411 1469
1412The process exit/trace status caused by C<rpid> (see your systems 1470The process exit/trace status caused by C<rpid> (see your systems
1413C<waitpid> and C<sys/wait.h> documentation for details). 1471C<waitpid> and C<sys/wait.h> documentation for details).
1414 1472
1415=back 1473=back
1474
1475=head3 Examples
1416 1476
1417Example: Try to exit cleanly on SIGINT and SIGTERM. 1477Example: Try to exit cleanly on SIGINT and SIGTERM.
1418 1478
1419 static void 1479 static void
1420 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1480 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
… …
1461semantics of C<ev_stat> watchers, which means that libev sometimes needs 1521semantics of C<ev_stat> watchers, which means that libev sometimes needs
1462to fall back to regular polling again even with inotify, but changes are 1522to fall back to regular polling again even with inotify, but changes are
1463usually detected immediately, and if the file exists there will be no 1523usually detected immediately, and if the file exists there will be no
1464polling. 1524polling.
1465 1525
1526=head3 Inotify
1527
1528When C<inotify (7)> support has been compiled into libev (generally only
1529available on Linux) and present at runtime, it will be used to speed up
1530change detection where possible. The inotify descriptor will be created lazily
1531when the first C<ev_stat> watcher is being started.
1532
1533Inotify presense does not change the semantics of C<ev_stat> watchers
1534except that changes might be detected earlier, and in some cases, to avoid
1535making regular C<stat> calls. Even in the presense of inotify support
1536there are many cases where libev has to resort to regular C<stat> polling.
1537
1538(There is no support for kqueue, as apparently it cannot be used to
1539implement this functionality, due to the requirement of having a file
1540descriptor open on the object at all times).
1541
1542=head3 The special problem of stat time resolution
1543
1544The C<stat ()> syscall only supports full-second resolution portably, and
1545even on systems where the resolution is higher, many filesystems still
1546only support whole seconds.
1547
1548That means that, if the time is the only thing that changes, you might
1549miss updates: on the first update, C<ev_stat> detects a change and calls
1550your callback, which does something. When there is another update within
1551the same second, C<ev_stat> will be unable to detect it.
1552
1553The solution to this is to delay acting on a change for a second (or till
1554the next second boundary), using a roughly one-second delay C<ev_timer>
1555(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
1556is added to work around small timing inconsistencies of some operating
1557systems.
1558
1466=head3 Watcher-Specific Functions and Data Members 1559=head3 Watcher-Specific Functions and Data Members
1467 1560
1468=over 4 1561=over 4
1469 1562
1470=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1563=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
… …
1507=item const char *path [read-only] 1600=item const char *path [read-only]
1508 1601
1509The filesystem path that is being watched. 1602The filesystem path that is being watched.
1510 1603
1511=back 1604=back
1605
1606=head3 Examples
1512 1607
1513Example: Watch C</etc/passwd> for attribute changes. 1608Example: Watch C</etc/passwd> for attribute changes.
1514 1609
1515 static void 1610 static void
1516 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1611 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
… …
1529 } 1624 }
1530 1625
1531 ... 1626 ...
1532 ev_stat passwd; 1627 ev_stat passwd;
1533 1628
1534 ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); 1629 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1535 ev_stat_start (loop, &passwd); 1630 ev_stat_start (loop, &passwd);
1631
1632Example: Like above, but additionally use a one-second delay so we do not
1633miss updates (however, frequent updates will delay processing, too, so
1634one might do the work both on C<ev_stat> callback invocation I<and> on
1635C<ev_timer> callback invocation).
1636
1637 static ev_stat passwd;
1638 static ev_timer timer;
1639
1640 static void
1641 timer_cb (EV_P_ ev_timer *w, int revents)
1642 {
1643 ev_timer_stop (EV_A_ w);
1644
1645 /* now it's one second after the most recent passwd change */
1646 }
1647
1648 static void
1649 stat_cb (EV_P_ ev_stat *w, int revents)
1650 {
1651 /* reset the one-second timer */
1652 ev_timer_again (EV_A_ &timer);
1653 }
1654
1655 ...
1656 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1657 ev_stat_start (loop, &passwd);
1658 ev_timer_init (&timer, timer_cb, 0., 1.01);
1536 1659
1537 1660
1538=head2 C<ev_idle> - when you've got nothing better to do... 1661=head2 C<ev_idle> - when you've got nothing better to do...
1539 1662
1540Idle watchers trigger events when no other events of the same or higher 1663Idle watchers trigger events when no other events of the same or higher
… …
1566kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1689kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1567believe me. 1690believe me.
1568 1691
1569=back 1692=back
1570 1693
1694=head3 Examples
1695
1571Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1696Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1572callback, free it. Also, use no error checking, as usual. 1697callback, free it. Also, use no error checking, as usual.
1573 1698
1574 static void 1699 static void
1575 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1700 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1576 { 1701 {
1577 free (w); 1702 free (w);
1578 // now do something you wanted to do when the program has 1703 // now do something you wanted to do when the program has
1579 // no longer asnything immediate to do. 1704 // no longer anything immediate to do.
1580 } 1705 }
1581 1706
1582 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1707 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1583 ev_idle_init (idle_watcher, idle_cb); 1708 ev_idle_init (idle_watcher, idle_cb);
1584 ev_idle_start (loop, idle_cb); 1709 ev_idle_start (loop, idle_cb);
… …
1646parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1771parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1647macros, but using them is utterly, utterly and completely pointless. 1772macros, but using them is utterly, utterly and completely pointless.
1648 1773
1649=back 1774=back
1650 1775
1776=head3 Examples
1777
1651There are a number of principal ways to embed other event loops or modules 1778There are a number of principal ways to embed other event loops or modules
1652into libev. Here are some ideas on how to include libadns into libev 1779into libev. Here are some ideas on how to include libadns into libev
1653(there is a Perl module named C<EV::ADNS> that does this, which you could 1780(there is a Perl module named C<EV::ADNS> that does this, which you could
1654use for an actually working example. Another Perl module named C<EV::Glib> 1781use for an actually working example. Another Perl module named C<EV::Glib>
1655embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV 1782embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
… …
1823portable one. 1950portable one.
1824 1951
1825So when you want to use this feature you will always have to be prepared 1952So when you want to use this feature you will always have to be prepared
1826that you cannot get an embeddable loop. The recommended way to get around 1953that you cannot get an embeddable loop. The recommended way to get around
1827this is to have a separate variables for your embeddable loop, try to 1954this is to have a separate variables for your embeddable loop, try to
1828create it, and if that fails, use the normal loop for everything: 1955create it, and if that fails, use the normal loop for everything.
1956
1957=head3 Watcher-Specific Functions and Data Members
1958
1959=over 4
1960
1961=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1962
1963=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1964
1965Configures the watcher to embed the given loop, which must be
1966embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1967invoked automatically, otherwise it is the responsibility of the callback
1968to invoke it (it will continue to be called until the sweep has been done,
1969if you do not want thta, you need to temporarily stop the embed watcher).
1970
1971=item ev_embed_sweep (loop, ev_embed *)
1972
1973Make a single, non-blocking sweep over the embedded loop. This works
1974similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1975apropriate way for embedded loops.
1976
1977=item struct ev_loop *other [read-only]
1978
1979The embedded event loop.
1980
1981=back
1982
1983=head3 Examples
1984
1985Example: Try to get an embeddable event loop and embed it into the default
1986event loop. If that is not possible, use the default loop. The default
1987loop is stored in C<loop_hi>, while the mebeddable loop is stored in
1988C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
1989used).
1829 1990
1830 struct ev_loop *loop_hi = ev_default_init (0); 1991 struct ev_loop *loop_hi = ev_default_init (0);
1831 struct ev_loop *loop_lo = 0; 1992 struct ev_loop *loop_lo = 0;
1832 struct ev_embed embed; 1993 struct ev_embed embed;
1833 1994
… …
1844 ev_embed_start (loop_hi, &embed); 2005 ev_embed_start (loop_hi, &embed);
1845 } 2006 }
1846 else 2007 else
1847 loop_lo = loop_hi; 2008 loop_lo = loop_hi;
1848 2009
1849=head3 Watcher-Specific Functions and Data Members 2010Example: Check if kqueue is available but not recommended and create
2011a kqueue backend for use with sockets (which usually work with any
2012kqueue implementation). Store the kqueue/socket-only event loop in
2013C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1850 2014
1851=over 4 2015 struct ev_loop *loop = ev_default_init (0);
2016 struct ev_loop *loop_socket = 0;
2017 struct ev_embed embed;
2018
2019 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2020 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2021 {
2022 ev_embed_init (&embed, 0, loop_socket);
2023 ev_embed_start (loop, &embed);
2024 }
1852 2025
1853=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 2026 if (!loop_socket)
2027 loop_socket = loop;
1854 2028
1855=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 2029 // now use loop_socket for all sockets, and loop for everything else
1856
1857Configures the watcher to embed the given loop, which must be
1858embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1859invoked automatically, otherwise it is the responsibility of the callback
1860to invoke it (it will continue to be called until the sweep has been done,
1861if you do not want thta, you need to temporarily stop the embed watcher).
1862
1863=item ev_embed_sweep (loop, ev_embed *)
1864
1865Make a single, non-blocking sweep over the embedded loop. This works
1866similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1867apropriate way for embedded loops.
1868
1869=item struct ev_loop *other [read-only]
1870
1871The embedded event loop.
1872
1873=back
1874 2030
1875 2031
1876=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2032=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1877 2033
1878Fork watchers are called when a C<fork ()> was detected (usually because 2034Fork watchers are called when a C<fork ()> was detected (usually because
… …
1894believe me. 2050believe me.
1895 2051
1896=back 2052=back
1897 2053
1898 2054
2055=head2 C<ev_async> - how to wake up another event loop
2056
2057In general, you cannot use an C<ev_loop> from multiple threads or other
2058asynchronous sources such as signal handlers (as opposed to multiple event
2059loops - those are of course safe to use in different threads).
2060
2061Sometimes, however, you need to wake up another event loop you do not
2062control, for example because it belongs to another thread. This is what
2063C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
2064can signal it by calling C<ev_async_send>, which is thread- and signal
2065safe.
2066
2067This functionality is very similar to C<ev_signal> watchers, as signals,
2068too, are asynchronous in nature, and signals, too, will be compressed
2069(i.e. the number of callback invocations may be less than the number of
2070C<ev_async_sent> calls).
2071
2072Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2073just the default loop.
2074
2075=head3 Queueing
2076
2077C<ev_async> does not support queueing of data in any way. The reason
2078is that the author does not know of a simple (or any) algorithm for a
2079multiple-writer-single-reader queue that works in all cases and doesn't
2080need elaborate support such as pthreads.
2081
2082That means that if you want to queue data, you have to provide your own
2083queue. But at least I can tell you would implement locking around your
2084queue:
2085
2086=over 4
2087
2088=item queueing from a signal handler context
2089
2090To implement race-free queueing, you simply add to the queue in the signal
2091handler but you block the signal handler in the watcher callback. Here is an example that does that for
2092some fictitiuous SIGUSR1 handler:
2093
2094 static ev_async mysig;
2095
2096 static void
2097 sigusr1_handler (void)
2098 {
2099 sometype data;
2100
2101 // no locking etc.
2102 queue_put (data);
2103 ev_async_send (DEFAULT_ &mysig);
2104 }
2105
2106 static void
2107 mysig_cb (EV_P_ ev_async *w, int revents)
2108 {
2109 sometype data;
2110 sigset_t block, prev;
2111
2112 sigemptyset (&block);
2113 sigaddset (&block, SIGUSR1);
2114 sigprocmask (SIG_BLOCK, &block, &prev);
2115
2116 while (queue_get (&data))
2117 process (data);
2118
2119 if (sigismember (&prev, SIGUSR1)
2120 sigprocmask (SIG_UNBLOCK, &block, 0);
2121 }
2122
2123(Note: pthreads in theory requires you to use C<pthread_setmask>
2124instead of C<sigprocmask> when you use threads, but libev doesn't do it
2125either...).
2126
2127=item queueing from a thread context
2128
2129The strategy for threads is different, as you cannot (easily) block
2130threads but you can easily preempt them, so to queue safely you need to
2131employ a traditional mutex lock, such as in this pthread example:
2132
2133 static ev_async mysig;
2134 static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
2135
2136 static void
2137 otherthread (void)
2138 {
2139 // only need to lock the actual queueing operation
2140 pthread_mutex_lock (&mymutex);
2141 queue_put (data);
2142 pthread_mutex_unlock (&mymutex);
2143
2144 ev_async_send (DEFAULT_ &mysig);
2145 }
2146
2147 static void
2148 mysig_cb (EV_P_ ev_async *w, int revents)
2149 {
2150 pthread_mutex_lock (&mymutex);
2151
2152 while (queue_get (&data))
2153 process (data);
2154
2155 pthread_mutex_unlock (&mymutex);
2156 }
2157
2158=back
2159
2160
2161=head3 Watcher-Specific Functions and Data Members
2162
2163=over 4
2164
2165=item ev_async_init (ev_async *, callback)
2166
2167Initialises and configures the async watcher - it has no parameters of any
2168kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2169believe me.
2170
2171=item ev_async_send (loop, ev_async *)
2172
2173Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2174an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2175C<ev_feed_event>, this call is safe to do in other threads, signal or
2176similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
2177section below on what exactly this means).
2178
2179This call incurs the overhead of a syscall only once per loop iteration,
2180so while the overhead might be noticable, it doesn't apply to repeated
2181calls to C<ev_async_send>.
2182
2183=back
2184
2185
1899=head1 OTHER FUNCTIONS 2186=head1 OTHER FUNCTIONS
1900 2187
1901There are some other functions of possible interest. Described. Here. Now. 2188There are some other functions of possible interest. Described. Here. Now.
1902 2189
1903=over 4 2190=over 4
… …
2130Example: Define a class with an IO and idle watcher, start one of them in 2417Example: Define a class with an IO and idle watcher, start one of them in
2131the constructor. 2418the constructor.
2132 2419
2133 class myclass 2420 class myclass
2134 { 2421 {
2135 ev_io io; void io_cb (ev::io &w, int revents); 2422 ev::io io; void io_cb (ev::io &w, int revents);
2136 ev_idle idle void idle_cb (ev::idle &w, int revents); 2423 ev:idle idle void idle_cb (ev::idle &w, int revents);
2137 2424
2138 myclass (); 2425 myclass (int fd)
2139 }
2140
2141 myclass::myclass (int fd)
2142 { 2426 {
2143 io .set <myclass, &myclass::io_cb > (this); 2427 io .set <myclass, &myclass::io_cb > (this);
2144 idle.set <myclass, &myclass::idle_cb> (this); 2428 idle.set <myclass, &myclass::idle_cb> (this);
2145 2429
2146 io.start (fd, ev::READ); 2430 io.start (fd, ev::READ);
2431 }
2147 } 2432 };
2148 2433
2149 2434
2150=head1 MACRO MAGIC 2435=head1 MACRO MAGIC
2151 2436
2152Libev can be compiled with a variety of options, the most fundamantal 2437Libev can be compiled with a variety of options, the most fundamantal
… …
2357wants osf handles on win32 (this is the case when the select to 2642wants osf handles on win32 (this is the case when the select to
2358be used is the winsock select). This means that it will call 2643be used is the winsock select). This means that it will call
2359C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, 2644C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2360it is assumed that all these functions actually work on fds, even 2645it is assumed that all these functions actually work on fds, even
2361on win32. Should not be defined on non-win32 platforms. 2646on win32. Should not be defined on non-win32 platforms.
2647
2648=item EV_FD_TO_WIN32_HANDLE
2649
2650If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2651file descriptors to socket handles. When not defining this symbol (the
2652default), then libev will call C<_get_osfhandle>, which is usually
2653correct. In some cases, programs use their own file descriptor management,
2654in which case they can provide this function to map fds to socket handles.
2362 2655
2363=item EV_USE_POLL 2656=item EV_USE_POLL
2364 2657
2365If defined to be C<1>, libev will compile in support for the C<poll>(2) 2658If defined to be C<1>, libev will compile in support for the C<poll>(2)
2366backend. Otherwise it will be enabled on non-win32 platforms. It 2659backend. Otherwise it will be enabled on non-win32 platforms. It
… …
2400 2693
2401If defined to be C<1>, libev will compile in support for the Linux inotify 2694If defined to be C<1>, libev will compile in support for the Linux inotify
2402interface to speed up C<ev_stat> watchers. Its actual availability will 2695interface to speed up C<ev_stat> watchers. Its actual availability will
2403be detected at runtime. 2696be detected at runtime.
2404 2697
2698=item EV_ATOMIC_T
2699
2700Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2701access is atomic with respect to other threads or signal contexts. No such
2702type is easily found in the C language, so you can provide your own type
2703that you know is safe for your purposes. It is used both for signal handler "locking"
2704as well as for signal and thread safety in C<ev_async> watchers.
2705
2706In the absense of this define, libev will use C<sig_atomic_t volatile>
2707(from F<signal.h>), which is usually good enough on most platforms.
2708
2405=item EV_H 2709=item EV_H
2406 2710
2407The name of the F<ev.h> header file used to include it. The default if 2711The name of the F<ev.h> header file used to include it. The default if
2408undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2712undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2409can be used to virtually rename the F<ev.h> header file in case of conflicts. 2713used to virtually rename the F<ev.h> header file in case of conflicts.
2410 2714
2411=item EV_CONFIG_H 2715=item EV_CONFIG_H
2412 2716
2413If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 2717If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2414F<ev.c>'s idea of where to find the F<config.h> file, similarly to 2718F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2415C<EV_H>, above. 2719C<EV_H>, above.
2416 2720
2417=item EV_EVENT_H 2721=item EV_EVENT_H
2418 2722
2419Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 2723Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2420of how the F<event.h> header can be found. 2724of how the F<event.h> header can be found, the default is C<"event.h">.
2421 2725
2422=item EV_PROTOTYPES 2726=item EV_PROTOTYPES
2423 2727
2424If defined to be C<0>, then F<ev.h> will not define any function 2728If defined to be C<0>, then F<ev.h> will not define any function
2425prototypes, but still define all the structs and other symbols. This is 2729prototypes, but still define all the structs and other symbols. This is
… …
2476=item EV_FORK_ENABLE 2780=item EV_FORK_ENABLE
2477 2781
2478If undefined or defined to be C<1>, then fork watchers are supported. If 2782If undefined or defined to be C<1>, then fork watchers are supported. If
2479defined to be C<0>, then they are not. 2783defined to be C<0>, then they are not.
2480 2784
2785=item EV_ASYNC_ENABLE
2786
2787If undefined or defined to be C<1>, then async watchers are supported. If
2788defined to be C<0>, then they are not.
2789
2481=item EV_MINIMAL 2790=item EV_MINIMAL
2482 2791
2483If you need to shave off some kilobytes of code at the expense of some 2792If you need to shave off some kilobytes of code at the expense of some
2484speed, define this symbol to C<1>. Currently only used for gcc to override 2793speed, define this symbol to C<1>. Currently only used for gcc to override
2485some inlining decisions, saves roughly 30% codesize of amd64. 2794some inlining decisions, saves roughly 30% codesize of amd64.
… …
2491than enough. If you need to manage thousands of children you might want to 2800than enough. If you need to manage thousands of children you might want to
2492increase this value (I<must> be a power of two). 2801increase this value (I<must> be a power of two).
2493 2802
2494=item EV_INOTIFY_HASHSIZE 2803=item EV_INOTIFY_HASHSIZE
2495 2804
2496C<ev_staz> watchers use a small hash table to distribute workload by 2805C<ev_stat> watchers use a small hash table to distribute workload by
2497inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 2806inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2498usually more than enough. If you need to manage thousands of C<ev_stat> 2807usually more than enough. If you need to manage thousands of C<ev_stat>
2499watchers you might want to increase this value (I<must> be a power of 2808watchers you might want to increase this value (I<must> be a power of
2500two). 2809two).
2501 2810
… …
2597 2906
2598=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) 2907=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2599 2908
2600This means that, when you have a watcher that triggers in one hour and 2909This means that, when you have a watcher that triggers in one hour and
2601there are 100 watchers that would trigger before that then inserting will 2910there are 100 watchers that would trigger before that then inserting will
2602have to skip those 100 watchers. 2911have to skip roughly seven (C<ld 100>) of these watchers.
2603 2912
2604=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) 2913=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2605 2914
2606That means that for changing a timer costs less than removing/adding them 2915That means that changing a timer costs less than removing/adding them
2607as only the relative motion in the event queue has to be paid for. 2916as only the relative motion in the event queue has to be paid for.
2608 2917
2609=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2918=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2610 2919
2611These just add the watcher into an array or at the head of a list. 2920These just add the watcher into an array or at the head of a list.
2921
2612=item Stopping check/prepare/idle watchers: O(1) 2922=item Stopping check/prepare/idle/fork/async watchers: O(1)
2613 2923
2614=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2924=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2615 2925
2616These watchers are stored in lists then need to be walked to find the 2926These watchers are stored in lists then need to be walked to find the
2617correct watcher to remove. The lists are usually short (you don't usually 2927correct watcher to remove. The lists are usually short (you don't usually
2618have many watchers waiting for the same fd or signal). 2928have many watchers waiting for the same fd or signal).
2619 2929
2620=item Finding the next timer per loop iteration: O(1) 2930=item Finding the next timer in each loop iteration: O(1)
2931
2932By virtue of using a binary heap, the next timer is always found at the
2933beginning of the storage array.
2621 2934
2622=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2935=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2623 2936
2624A change means an I/O watcher gets started or stopped, which requires 2937A change means an I/O watcher gets started or stopped, which requires
2625libev to recalculate its status (and possibly tell the kernel). 2938libev to recalculate its status (and possibly tell the kernel, depending
2939on backend and wether C<ev_io_set> was used).
2626 2940
2627=item Activating one watcher: O(1) 2941=item Activating one watcher (putting it into the pending state): O(1)
2628 2942
2629=item Priority handling: O(number_of_priorities) 2943=item Priority handling: O(number_of_priorities)
2630 2944
2631Priorities are implemented by allocating some space for each 2945Priorities are implemented by allocating some space for each
2632priority. When doing priority-based operations, libev usually has to 2946priority. When doing priority-based operations, libev usually has to
2633linearly search all the priorities. 2947linearly search all the priorities, but starting/stopping and activating
2948watchers becomes O(1) w.r.t. priority handling.
2949
2950=item Sending an ev_async: O(1)
2951
2952=item Processing ev_async_send: O(number_of_async_watchers)
2953
2954=item Processing signals: O(max_signal_number)
2955
2956Sending involves a syscall I<iff> there were no other C<ev_async_send>
2957calls in the current loop iteration. Checking for async and signal events
2958involves iterating over all running async watchers or all signal numbers.
2634 2959
2635=back 2960=back
2636 2961
2637 2962
2963=head1 Win32 platform limitations and workarounds
2964
2965Win32 doesn't support any of the standards (e.g. POSIX) that libev
2966requires, and its I/O model is fundamentally incompatible with the POSIX
2967model. Libev still offers limited functionality on this platform in
2968the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2969descriptors. This only applies when using Win32 natively, not when using
2970e.g. cygwin.
2971
2972There is no supported compilation method available on windows except
2973embedding it into other applications.
2974
2975Due to the many, low, and arbitrary limits on the win32 platform and the
2976abysmal performance of winsockets, using a large number of sockets is not
2977recommended (and not reasonable). If your program needs to use more than
2978a hundred or so sockets, then likely it needs to use a totally different
2979implementation for windows, as libev offers the POSIX model, which cannot
2980be implemented efficiently on windows (microsoft monopoly games).
2981
2982=over 4
2983
2984=item The winsocket select function
2985
2986The winsocket C<select> function doesn't follow POSIX in that it requires
2987socket I<handles> and not socket I<file descriptors>. This makes select
2988very inefficient, and also requires a mapping from file descriptors
2989to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
2990C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
2991symbols for more info.
2992
2993The configuration for a "naked" win32 using the microsoft runtime
2994libraries and raw winsocket select is:
2995
2996 #define EV_USE_SELECT 1
2997 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2998
2999Note that winsockets handling of fd sets is O(n), so you can easily get a
3000complexity in the O(n²) range when using win32.
3001
3002=item Limited number of file descriptors
3003
3004Windows has numerous arbitrary (and low) limits on things. Early versions
3005of winsocket's select only supported waiting for a max. of C<64> handles
3006(probably owning to the fact that all windows kernels can only wait for
3007C<64> things at the same time internally; microsoft recommends spawning a
3008chain of threads and wait for 63 handles and the previous thread in each).
3009
3010Newer versions support more handles, but you need to define C<FD_SETSIZE>
3011to some high number (e.g. C<2048>) before compiling the winsocket select
3012call (which might be in libev or elsewhere, for example, perl does its own
3013select emulation on windows).
3014
3015Another limit is the number of file descriptors in the microsoft runtime
3016libraries, which by default is C<64> (there must be a hidden I<64> fetish
3017or something like this inside microsoft). You can increase this by calling
3018C<_setmaxstdio>, which can increase this limit to C<2048> (another
3019arbitrary limit), but is broken in many versions of the microsoft runtime
3020libraries.
3021
3022This might get you to about C<512> or C<2048> sockets (depending on
3023windows version and/or the phase of the moon). To get more, you need to
3024wrap all I/O functions and provide your own fd management, but the cost of
3025calling select (O(n²)) will likely make this unworkable.
3026
3027=back
3028
3029
2638=head1 AUTHOR 3030=head1 AUTHOR
2639 3031
2640Marc Lehmann <libev@schmorp.de>. 3032Marc Lehmann <libev@schmorp.de>.
2641 3033

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