… | |
… | |
131 | .\} |
131 | .\} |
132 | .rm #[ #] #H #V #F C |
132 | .rm #[ #] #H #V #F C |
133 | .\" ======================================================================== |
133 | .\" ======================================================================== |
134 | .\" |
134 | .\" |
135 | .IX Title "LIBEV 3" |
135 | .IX Title "LIBEV 3" |
136 | .TH LIBEV 3 "2019-06-20" "libev-4.25" "libev - high performance full featured event loop" |
136 | .TH LIBEV 3 "2020-01-22" "libev-4.31" "libev - high performance full featured event loop" |
137 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
137 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
138 | .\" way too many mistakes in technical documents. |
138 | .\" way too many mistakes in technical documents. |
139 | .if n .ad l |
139 | .if n .ad l |
140 | .nh |
140 | .nh |
141 | .SH "NAME" |
141 | .SH "NAME" |
… | |
… | |
240 | watchers\fR, which are relatively small C structures you initialise with the |
240 | watchers\fR, which are relatively small C structures you initialise with the |
241 | details of the event, and then hand it over to libev by \fIstarting\fR the |
241 | details of the event, and then hand it over to libev by \fIstarting\fR the |
242 | watcher. |
242 | watcher. |
243 | .SS "\s-1FEATURES\s0" |
243 | .SS "\s-1FEATURES\s0" |
244 | .IX Subsection "FEATURES" |
244 | .IX Subsection "FEATURES" |
245 | Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the |
245 | Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific aio and \f(CW\*(C`epoll\*(C'\fR |
246 | BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms |
246 | interfaces, the BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port |
247 | for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface |
247 | mechanisms for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR |
248 | (for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner |
248 | interface (for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner |
249 | inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative |
249 | inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative |
250 | timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling |
250 | timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling |
251 | (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status |
251 | (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status |
252 | change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event |
252 | change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event |
253 | loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and |
253 | loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and |
… | |
… | |
291 | When libev detects a usage error such as a negative timer interval, then |
291 | When libev detects a usage error such as a negative timer interval, then |
292 | it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism, |
292 | it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism, |
293 | so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in |
293 | so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in |
294 | the libev caller and need to be fixed there. |
294 | the libev caller and need to be fixed there. |
295 | .PP |
295 | .PP |
|
|
296 | Via the \f(CW\*(C`EV_FREQUENT\*(C'\fR macro you can compile in and/or enable extensive |
|
|
297 | consistency checking code inside libev that can be used to check for |
|
|
298 | internal inconsistencies, suually caused by application bugs. |
|
|
299 | .PP |
296 | Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions, and also has |
300 | Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions. These do not |
297 | extensive consistency checking code. These do not trigger under normal |
|
|
298 | circumstances, as they indicate either a bug in libev or worse. |
301 | trigger under normal circumstances, as they indicate either a bug in libev |
|
|
302 | or worse. |
299 | .SH "GLOBAL FUNCTIONS" |
303 | .SH "GLOBAL FUNCTIONS" |
300 | .IX Header "GLOBAL FUNCTIONS" |
304 | .IX Header "GLOBAL FUNCTIONS" |
301 | These functions can be called anytime, even before initialising the |
305 | These functions can be called anytime, even before initialising the |
302 | library in any way. |
306 | library in any way. |
303 | .IP "ev_tstamp ev_time ()" 4 |
307 | .IP "ev_tstamp ev_time ()" 4 |
… | |
… | |
602 | want to handle signals only in specific threads and want to avoid libev |
606 | want to handle signals only in specific threads and want to avoid libev |
603 | unblocking the signals. |
607 | unblocking the signals. |
604 | .Sp |
608 | .Sp |
605 | It's also required by \s-1POSIX\s0 in a threaded program, as libev calls |
609 | It's also required by \s-1POSIX\s0 in a threaded program, as libev calls |
606 | \&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified. |
610 | \&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified. |
|
|
611 | .ie n .IP """EVFLAG_NOTIMERFD""" 4 |
|
|
612 | .el .IP "\f(CWEVFLAG_NOTIMERFD\fR" 4 |
|
|
613 | .IX Item "EVFLAG_NOTIMERFD" |
|
|
614 | When this flag is specified, the libev will avoid using a \f(CW\*(C`timerfd\*(C'\fR to |
|
|
615 | detect time jumps. It will still be able to detect time jumps, but takes |
|
|
616 | longer and has a lower accuracy in doing so, but saves a file descriptor |
|
|
617 | per loop. |
607 | .Sp |
618 | .Sp |
608 | This flag's behaviour will become the default in future versions of libev. |
619 | The current implementation only tries to use a \f(CW\*(C`timerfd\*(C'\fR when the first |
|
|
620 | \&\f(CW\*(C`ev_periodic\*(C'\fR watcher is started and falls back on other methods if it |
|
|
621 | cannot be created, but this behaviour might change in the future. |
609 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
622 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
610 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
623 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
611 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
624 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
612 | This is your standard \fBselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
625 | This is your standard \fBselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
613 | libev tries to roll its own fd_set with no limits on the number of fds, |
626 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
638 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and |
651 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and |
639 | \&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. |
652 | \&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. |
640 | .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
653 | .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
641 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
654 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
642 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
655 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
643 | Use the linux-specific \fBepoll\fR\|(7) interface (for both pre\- and post\-2.6.9 |
656 | Use the Linux-specific \fBepoll\fR\|(7) interface (for both pre\- and post\-2.6.9 |
644 | kernels). |
657 | kernels). |
645 | .Sp |
658 | .Sp |
646 | For few fds, this backend is a bit little slower than poll and select, but |
659 | For few fds, this backend is a bit little slower than poll and select, but |
647 | it scales phenomenally better. While poll and select usually scale like |
660 | it scales phenomenally better. While poll and select usually scale like |
648 | O(total_fds) where total_fds is the total number of fds (or the highest |
661 | O(total_fds) where total_fds is the total number of fds (or the highest |
… | |
… | |
694 | All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or |
707 | All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or |
695 | faster than epoll for maybe up to a hundred file descriptors, depending on |
708 | faster than epoll for maybe up to a hundred file descriptors, depending on |
696 | the usage. So sad. |
709 | the usage. So sad. |
697 | .Sp |
710 | .Sp |
698 | While nominally embeddable in other event loops, this feature is broken in |
711 | While nominally embeddable in other event loops, this feature is broken in |
699 | all kernel versions tested so far. |
712 | a lot of kernel revisions, but probably(!) works in current versions. |
|
|
713 | .Sp |
|
|
714 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
|
|
715 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
716 | .ie n .IP """EVBACKEND_LINUXAIO"" (value 64, Linux)" 4 |
|
|
717 | .el .IP "\f(CWEVBACKEND_LINUXAIO\fR (value 64, Linux)" 4 |
|
|
718 | .IX Item "EVBACKEND_LINUXAIO (value 64, Linux)" |
|
|
719 | Use the Linux-specific Linux \s-1AIO\s0 (\fInot\fR \f(CWaio(7)\fR but \f(CWio_submit(2)\fR) event interface available in post\-4.18 kernels (but libev |
|
|
720 | only tries to use it in 4.19+). |
|
|
721 | .Sp |
|
|
722 | This is another Linux train wreck of an event interface. |
|
|
723 | .Sp |
|
|
724 | If this backend works for you (as of this writing, it was very |
|
|
725 | experimental), it is the best event interface available on Linux and might |
|
|
726 | be well worth enabling it \- if it isn't available in your kernel this will |
|
|
727 | be detected and this backend will be skipped. |
|
|
728 | .Sp |
|
|
729 | This backend can batch oneshot requests and supports a user-space ring |
|
|
730 | buffer to receive events. It also doesn't suffer from most of the design |
|
|
731 | problems of epoll (such as not being able to remove event sources from |
|
|
732 | the epoll set), and generally sounds too good to be true. Because, this |
|
|
733 | being the Linux kernel, of course it suffers from a whole new set of |
|
|
734 | limitations, forcing you to fall back to epoll, inheriting all its design |
|
|
735 | issues. |
|
|
736 | .Sp |
|
|
737 | For one, it is not easily embeddable (but probably could be done using |
|
|
738 | an event fd at some extra overhead). It also is subject to a system wide |
|
|
739 | limit that can be configured in \fI/proc/sys/fs/aio\-max\-nr\fR. If no \s-1AIO\s0 |
|
|
740 | requests are left, this backend will be skipped during initialisation, and |
|
|
741 | will switch to epoll when the loop is active. |
|
|
742 | .Sp |
|
|
743 | Most problematic in practice, however, is that not all file descriptors |
|
|
744 | work with it. For example, in Linux 5.1, \s-1TCP\s0 sockets, pipes, event fds, |
|
|
745 | files, \fI/dev/null\fR and many others are supported, but ttys do not work |
|
|
746 | properly (a known bug that the kernel developers don't care about, see |
|
|
747 | <https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
|
|
748 | (yet?) a generic event polling interface. |
|
|
749 | .Sp |
|
|
750 | Overall, it seems the Linux developers just don't want it to have a |
|
|
751 | generic event handling mechanism other than \f(CW\*(C`select\*(C'\fR or \f(CW\*(C`poll\*(C'\fR. |
|
|
752 | .Sp |
|
|
753 | To work around all these problem, the current version of libev uses its |
|
|
754 | epoll backend as a fallback for file descriptor types that do not work. Or |
|
|
755 | falls back completely to epoll if the kernel acts up. |
700 | .Sp |
756 | .Sp |
701 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
757 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
702 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
758 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
703 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
759 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
704 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
760 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
705 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
761 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
706 | Kqueue deserves special mention, as at the time of this writing, it |
762 | Kqueue deserves special mention, as at the time this backend was |
707 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
763 | implemented, it was broken on all BSDs except NetBSD (usually it doesn't |
708 | with anything but sockets and pipes, except on Darwin, where of course |
764 | work reliably with anything but sockets and pipes, except on Darwin, |
709 | it's completely useless). Unlike epoll, however, whose brokenness |
765 | where of course it's completely useless). Unlike epoll, however, whose |
710 | is by design, these kqueue bugs can (and eventually will) be fixed |
766 | brokenness is by design, these kqueue bugs can be (and mostly have been) |
711 | without \s-1API\s0 changes to existing programs. For this reason it's not being |
767 | fixed without \s-1API\s0 changes to existing programs. For this reason it's not |
712 | \&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using |
768 | being \*(L"auto-detected\*(R" on all platforms unless you explicitly specify it |
713 | \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) |
769 | in the flags (i.e. using \f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a |
714 | system like NetBSD. |
770 | known-to-be-good (\-enough) system like NetBSD. |
715 | .Sp |
771 | .Sp |
716 | You still can embed kqueue into a normal poll or select backend and use it |
772 | You still can embed kqueue into a normal poll or select backend and use it |
717 | only for sockets (after having made sure that sockets work with kqueue on |
773 | only for sockets (after having made sure that sockets work with kqueue on |
718 | the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
774 | the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
719 | .Sp |
775 | .Sp |
720 | It scales in the same way as the epoll backend, but the interface to the |
776 | It scales in the same way as the epoll backend, but the interface to the |
721 | kernel is more efficient (which says nothing about its actual speed, of |
777 | kernel is more efficient (which says nothing about its actual speed, of |
722 | course). While stopping, setting and starting an I/O watcher does never |
778 | course). While stopping, setting and starting an I/O watcher does never |
723 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
779 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
724 | two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you |
780 | two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you |
725 | might have to leak fd's on fork, but it's more sane than epoll) and it |
781 | might have to leak fds on fork, but it's more sane than epoll) and it |
726 | drops fds silently in similarly hard-to-detect cases. |
782 | drops fds silently in similarly hard-to-detect cases. |
727 | .Sp |
783 | .Sp |
728 | This backend usually performs well under most conditions. |
784 | This backend usually performs well under most conditions. |
729 | .Sp |
785 | .Sp |
730 | While nominally embeddable in other event loops, this doesn't work |
786 | While nominally embeddable in other event loops, this doesn't work |
… | |
… | |
807 | Example: Use whatever libev has to offer, but make sure that kqueue is |
863 | Example: Use whatever libev has to offer, but make sure that kqueue is |
808 | used if available. |
864 | used if available. |
809 | .Sp |
865 | .Sp |
810 | .Vb 1 |
866 | .Vb 1 |
811 | \& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
867 | \& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
868 | .Ve |
|
|
869 | .Sp |
|
|
870 | Example: Similarly, on linux, you mgiht want to take advantage of the |
|
|
871 | linux aio backend if possible, but fall back to something else if that |
|
|
872 | isn't available. |
|
|
873 | .Sp |
|
|
874 | .Vb 1 |
|
|
875 | \& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
812 | .Ve |
876 | .Ve |
813 | .RE |
877 | .RE |
814 | .IP "ev_loop_destroy (loop)" 4 |
878 | .IP "ev_loop_destroy (loop)" 4 |
815 | .IX Item "ev_loop_destroy (loop)" |
879 | .IX Item "ev_loop_destroy (loop)" |
816 | Destroys an event loop object (frees all memory and kernel state |
880 | Destroys an event loop object (frees all memory and kernel state |
… | |
… | |
1599 | .IX Subsection "WATCHER PRIORITY MODELS" |
1663 | .IX Subsection "WATCHER PRIORITY MODELS" |
1600 | Many event loops support \fIwatcher priorities\fR, which are usually small |
1664 | Many event loops support \fIwatcher priorities\fR, which are usually small |
1601 | integers that influence the ordering of event callback invocation |
1665 | integers that influence the ordering of event callback invocation |
1602 | between watchers in some way, all else being equal. |
1666 | between watchers in some way, all else being equal. |
1603 | .PP |
1667 | .PP |
1604 | In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its |
1668 | In libev, watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its |
1605 | description for the more technical details such as the actual priority |
1669 | description for the more technical details such as the actual priority |
1606 | range. |
1670 | range. |
1607 | .PP |
1671 | .PP |
1608 | There are two common ways how these these priorities are being interpreted |
1672 | There are two common ways how these these priorities are being interpreted |
1609 | by event loops: |
1673 | by event loops: |
… | |
… | |
1703 | .IX Header "WATCHER TYPES" |
1767 | .IX Header "WATCHER TYPES" |
1704 | This section describes each watcher in detail, but will not repeat |
1768 | This section describes each watcher in detail, but will not repeat |
1705 | information given in the last section. Any initialisation/set macros, |
1769 | information given in the last section. Any initialisation/set macros, |
1706 | functions and members specific to the watcher type are explained. |
1770 | functions and members specific to the watcher type are explained. |
1707 | .PP |
1771 | .PP |
1708 | Members are additionally marked with either \fI[read\-only]\fR, meaning that, |
1772 | Most members are additionally marked with either \fI[read\-only]\fR, meaning |
1709 | while the watcher is active, you can look at the member and expect some |
1773 | that, while the watcher is active, you can look at the member and expect |
1710 | sensible content, but you must not modify it (you can modify it while the |
1774 | some sensible content, but you must not modify it (you can modify it while |
1711 | watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
1775 | the watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
1712 | means you can expect it to have some sensible content while the watcher |
1776 | means you can expect it to have some sensible content while the watcher |
1713 | is active, but you can also modify it. Modifying it may not do something |
1777 | is active, but you can also modify it. Modifying it may not do something |
1714 | sensible or take immediate effect (or do anything at all), but libev will |
1778 | sensible or take immediate effect (or do anything at all), but libev will |
1715 | not crash or malfunction in any way. |
1779 | not crash or malfunction in any way. |
|
|
1780 | .PP |
|
|
1781 | In any case, the documentation for each member will explain what the |
|
|
1782 | effects are, and if there are any additional access restrictions. |
1716 | .ie n .SS """ev_io"" \- is this file descriptor readable or writable?" |
1783 | .ie n .SS """ev_io"" \- is this file descriptor readable or writable?" |
1717 | .el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
1784 | .el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
1718 | .IX Subsection "ev_io - is this file descriptor readable or writable?" |
1785 | .IX Subsection "ev_io - is this file descriptor readable or writable?" |
1719 | I/O watchers check whether a file descriptor is readable or writable |
1786 | I/O watchers check whether a file descriptor is readable or writable |
1720 | in each iteration of the event loop, or, more precisely, when reading |
1787 | in each iteration of the event loop, or, more precisely, when reading |
… | |
… | |
1748 | But really, best use non-blocking mode. |
1815 | But really, best use non-blocking mode. |
1749 | .PP |
1816 | .PP |
1750 | \fIThe special problem of disappearing file descriptors\fR |
1817 | \fIThe special problem of disappearing file descriptors\fR |
1751 | .IX Subsection "The special problem of disappearing file descriptors" |
1818 | .IX Subsection "The special problem of disappearing file descriptors" |
1752 | .PP |
1819 | .PP |
1753 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1820 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1754 | descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means, |
1821 | a file descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other |
1755 | such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file |
1822 | means, such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some |
1756 | descriptor, but when it goes away, the operating system will silently drop |
1823 | file descriptor, but when it goes away, the operating system will silently |
1757 | this interest. If another file descriptor with the same number then is |
1824 | drop this interest. If another file descriptor with the same number then |
1758 | registered with libev, there is no efficient way to see that this is, in |
1825 | is registered with libev, there is no efficient way to see that this is, |
1759 | fact, a different file descriptor. |
1826 | in fact, a different file descriptor. |
1760 | .PP |
1827 | .PP |
1761 | To avoid having to explicitly tell libev about such cases, libev follows |
1828 | To avoid having to explicitly tell libev about such cases, libev follows |
1762 | the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev |
1829 | the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev |
1763 | will assume that this is potentially a new file descriptor, otherwise |
1830 | will assume that this is potentially a new file descriptor, otherwise |
1764 | it is assumed that the file descriptor stays the same. That means that |
1831 | it is assumed that the file descriptor stays the same. That means that |
… | |
… | |
1816 | reuse the same code path. |
1883 | reuse the same code path. |
1817 | .PP |
1884 | .PP |
1818 | \fIThe special problem of fork\fR |
1885 | \fIThe special problem of fork\fR |
1819 | .IX Subsection "The special problem of fork" |
1886 | .IX Subsection "The special problem of fork" |
1820 | .PP |
1887 | .PP |
1821 | Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit |
1888 | Some backends (epoll, kqueue, linuxaio, iouring) do not support \f(CW\*(C`fork ()\*(C'\fR |
1822 | useless behaviour. Libev fully supports fork, but needs to be told about |
1889 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1823 | it in the child if you want to continue to use it in the child. |
1890 | to be told about it in the child if you want to continue to use it in the |
|
|
1891 | child. |
1824 | .PP |
1892 | .PP |
1825 | To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork |
1893 | To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork |
1826 | ()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to |
1894 | ()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to |
1827 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1895 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1828 | .PP |
1896 | .PP |
… | |
… | |
1887 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
1955 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
1888 | .PD |
1956 | .PD |
1889 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
1957 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
1890 | receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or |
1958 | receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or |
1891 | \&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events. |
1959 | \&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events. |
|
|
1960 | .IP "ev_io_modify (ev_io *, int events)" 4 |
|
|
1961 | .IX Item "ev_io_modify (ev_io *, int events)" |
|
|
1962 | Similar to \f(CW\*(C`ev_io_set\*(C'\fR, but only changes the event mask. Using this might |
|
|
1963 | be faster with some backends, as libev can assume that the \f(CW\*(C`fd\*(C'\fR still |
|
|
1964 | refers to the same underlying file description, something it cannot do |
|
|
1965 | when using \f(CW\*(C`ev_io_set\*(C'\fR. |
1892 | .IP "int fd [read\-only]" 4 |
1966 | .IP "int fd [no\-modify]" 4 |
1893 | .IX Item "int fd [read-only]" |
1967 | .IX Item "int fd [no-modify]" |
1894 | The file descriptor being watched. |
1968 | The file descriptor being watched. While it can be read at any time, you |
|
|
1969 | must not modify this member even when the watcher is stopped \- always use |
|
|
1970 | \&\f(CW\*(C`ev_io_set\*(C'\fR for that. |
1895 | .IP "int events [read\-only]" 4 |
1971 | .IP "int events [no\-modify]" 4 |
1896 | .IX Item "int events [read-only]" |
1972 | .IX Item "int events [no-modify]" |
1897 | The events being watched. |
1973 | The set of events being watched, among other flags. This field is a |
|
|
1974 | bit set \- to test for \f(CW\*(C`EV_READ\*(C'\fR, use \f(CW\*(C`w\->events & EV_READ\*(C'\fR, and |
|
|
1975 | similarly for \f(CW\*(C`EV_WRITE\*(C'\fR. |
|
|
1976 | .Sp |
|
|
1977 | As with \f(CW\*(C`fd\*(C'\fR, you must not modify this member even when the watcher is |
|
|
1978 | stopped, always use \f(CW\*(C`ev_io_set\*(C'\fR or \f(CW\*(C`ev_io_modify\*(C'\fR for that. |
1898 | .PP |
1979 | .PP |
1899 | \fIExamples\fR |
1980 | \fIExamples\fR |
1900 | .IX Subsection "Examples" |
1981 | .IX Subsection "Examples" |
1901 | .PP |
1982 | .PP |
1902 | Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well |
1983 | Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well |
… | |
… | |
4567 | \& ev_win32.c required on win32 platforms only |
4648 | \& ev_win32.c required on win32 platforms only |
4568 | \& |
4649 | \& |
4569 | \& ev_select.c only when select backend is enabled |
4650 | \& ev_select.c only when select backend is enabled |
4570 | \& ev_poll.c only when poll backend is enabled |
4651 | \& ev_poll.c only when poll backend is enabled |
4571 | \& ev_epoll.c only when the epoll backend is enabled |
4652 | \& ev_epoll.c only when the epoll backend is enabled |
|
|
4653 | \& ev_linuxaio.c only when the linux aio backend is enabled |
|
|
4654 | \& ev_iouring.c only when the linux io_uring backend is enabled |
4572 | \& ev_kqueue.c only when the kqueue backend is enabled |
4655 | \& ev_kqueue.c only when the kqueue backend is enabled |
4573 | \& ev_port.c only when the solaris port backend is enabled |
4656 | \& ev_port.c only when the solaris port backend is enabled |
4574 | .Ve |
4657 | .Ve |
4575 | .PP |
4658 | .PP |
4576 | \&\fIev.c\fR includes the backend files directly when enabled, so you only need |
4659 | \&\fIev.c\fR includes the backend files directly when enabled, so you only need |
… | |
… | |
4689 | higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). |
4772 | higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). |
4690 | .IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
4773 | .IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
4691 | .IX Item "EV_USE_NANOSLEEP" |
4774 | .IX Item "EV_USE_NANOSLEEP" |
4692 | If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
4775 | If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
4693 | and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
4776 | and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
|
|
4777 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
|
|
4778 | .IX Item "EV_USE_EVENTFD" |
|
|
4779 | If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is |
|
|
4780 | available and will probe for kernel support at runtime. This will improve |
|
|
4781 | \&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. |
|
|
4782 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4783 | 2.7 or newer, otherwise disabled. |
|
|
4784 | .IP "\s-1EV_USE_SIGNALFD\s0" 4 |
|
|
4785 | .IX Item "EV_USE_SIGNALFD" |
|
|
4786 | If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`signalfd ()\*(C'\fR is |
|
|
4787 | available and will probe for kernel support at runtime. This enables |
|
|
4788 | the use of \s-1EVFLAG_SIGNALFD\s0 for faster and simpler signal handling. If |
|
|
4789 | undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4790 | 2.7 or newer, otherwise disabled. |
|
|
4791 | .IP "\s-1EV_USE_TIMERFD\s0" 4 |
|
|
4792 | .IX Item "EV_USE_TIMERFD" |
|
|
4793 | If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`timerfd ()\*(C'\fR is |
|
|
4794 | available and will probe for kernel support at runtime. This allows |
|
|
4795 | libev to detect time jumps accurately. If undefined, it will be enabled |
|
|
4796 | if the headers indicate GNU/Linux + Glibc 2.8 or newer and define |
|
|
4797 | \&\f(CW\*(C`TFD_TIMER_CANCEL_ON_SET\*(C'\fR, otherwise disabled. |
4694 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
4798 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
4695 | .IX Item "EV_USE_EVENTFD" |
4799 | .IX Item "EV_USE_EVENTFD" |
4696 | If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is |
4800 | If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is |
4697 | available and will probe for kernel support at runtime. This will improve |
4801 | available and will probe for kernel support at runtime. This will improve |
4698 | \&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. |
4802 | \&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. |
… | |
… | |
4757 | If defined to be \f(CW1\fR, libev will compile in support for the Linux |
4861 | If defined to be \f(CW1\fR, libev will compile in support for the Linux |
4758 | \&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, |
4862 | \&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, |
4759 | otherwise another method will be used as fallback. This is the preferred |
4863 | otherwise another method will be used as fallback. This is the preferred |
4760 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4864 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4761 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4865 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4866 | .IP "\s-1EV_USE_LINUXAIO\s0" 4 |
|
|
4867 | .IX Item "EV_USE_LINUXAIO" |
|
|
4868 | If defined to be \f(CW1\fR, libev will compile in support for the Linux aio |
|
|
4869 | backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). If undefined, it will be |
|
|
4870 | enabled on linux, otherwise disabled. |
|
|
4871 | .IP "\s-1EV_USE_IOURING\s0" 4 |
|
|
4872 | .IX Item "EV_USE_IOURING" |
|
|
4873 | If defined to be \f(CW1\fR, libev will compile in support for the Linux |
|
|
4874 | io_uring backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). Due to it's |
|
|
4875 | current limitations it has to be requested explicitly. If undefined, it |
|
|
4876 | will be enabled on linux, otherwise disabled. |
4762 | .IP "\s-1EV_USE_KQUEUE\s0" 4 |
4877 | .IP "\s-1EV_USE_KQUEUE\s0" 4 |
4763 | .IX Item "EV_USE_KQUEUE" |
4878 | .IX Item "EV_USE_KQUEUE" |
4764 | If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style |
4879 | If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style |
4765 | \&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, |
4880 | \&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, |
4766 | otherwise another method will be used as fallback. This is the preferred |
4881 | otherwise another method will be used as fallback. This is the preferred |
… | |
… | |
5022 | in. If set to \f(CW1\fR, then verification code will be compiled in, but not |
5137 | in. If set to \f(CW1\fR, then verification code will be compiled in, but not |
5023 | called. If set to \f(CW2\fR, then the internal verification code will be |
5138 | called. If set to \f(CW2\fR, then the internal verification code will be |
5024 | called once per loop, which can slow down libev. If set to \f(CW3\fR, then the |
5139 | called once per loop, which can slow down libev. If set to \f(CW3\fR, then the |
5025 | verification code will be called very frequently, which will slow down |
5140 | verification code will be called very frequently, which will slow down |
5026 | libev considerably. |
5141 | libev considerably. |
|
|
5142 | .Sp |
|
|
5143 | Verification errors are reported via C's \f(CW\*(C`assert\*(C'\fR mechanism, so if you |
|
|
5144 | disable that (e.g. by defining \f(CW\*(C`NDEBUG\*(C'\fR) then no errors will be reported. |
5027 | .Sp |
5145 | .Sp |
5028 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it |
5146 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it |
5029 | will be \f(CW0\fR. |
5147 | will be \f(CW0\fR. |
5030 | .IP "\s-1EV_COMMON\s0" 4 |
5148 | .IP "\s-1EV_COMMON\s0" 4 |
5031 | .IX Item "EV_COMMON" |
5149 | .IX Item "EV_COMMON" |