diff options
Diffstat (limited to 'ev.3')
| -rw-r--r-- | ev.3 | 78 |
1 files changed, 34 insertions, 44 deletions
@@ -257,8 +257,8 @@ library in any way. Returns the current time as libev would use it. Please note that the \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp you actually want to know. -.IP "void ev_sleep (ev_tstamp interval)" 4 -.IX Item "void ev_sleep (ev_tstamp interval)" +.IP "ev_sleep (ev_tstamp interval)" 4 +.IX Item "ev_sleep (ev_tstamp interval)" Sleep for the given interval: The current thread will be blocked until either it is interrupted or the given time interval has passed. Basically this is a subsecond-resolution \f(CW\*(C`sleep ()\*(C'\fR. @@ -486,20 +486,23 @@ need to use non-blocking I/O or other means to avoid blocking when no data .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" Kqueue deserves special mention, as at the time of this writing, it -was broken on \fIall\fR BSDs (usually it doesn't work with anything but -sockets and pipes, except on Darwin, where of course it's completely -useless. On NetBSD, it seems to work for all the \s-1FD\s0 types I tested, so it -is used by default there). For this reason it's not being \*(L"autodetected\*(R" +was broken on all BSDs except NetBSD (usually it doesn't work reliably +with anything but sockets and pipes, except on Darwin, where of course +it's completely useless). For this reason it's not being \*(L"autodetected\*(R" unless you explicitly specify it explicitly in the flags (i.e. using \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) system like NetBSD. .Sp +You still can embed kqueue into a normal poll or select backend and use it +only for sockets (after having made sure that sockets work with kqueue on +the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. +.Sp It scales in the same way as the epoll backend, but the interface to the -kernel is more efficient (which says nothing about its actual speed, -of course). While stopping, setting and starting an I/O watcher does -never cause an extra syscall as with epoll, it still adds up to two event -changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it drops fds -silently in similarly hard-to-detetc cases. +kernel is more efficient (which says nothing about its actual speed, of +course). While stopping, setting and starting an I/O watcher does never +cause an extra syscall as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to +two event changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it +drops fds silently in similarly hard-to-detect cases. .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" @@ -731,11 +734,11 @@ Example: For some weird reason, unregister the above signal handler again. \& ev_ref (loop); \& ev_signal_stop (loop, &exitsig); .Ve -.IP "ev_set_io_collect_interval (ev_tstamp interval)" 4 -.IX Item "ev_set_io_collect_interval (ev_tstamp interval)" +.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4 +.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)" .PD 0 -.IP "ev_set_timeout_collect_interval (ev_tstamp interval)" 4 -.IX Item "ev_set_timeout_collect_interval (ev_tstamp interval)" +.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4 +.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" .PD These advanced functions influence the time that libev will spend waiting for events. Both are by default \f(CW0\fR, meaning that libev will try to @@ -754,18 +757,20 @@ overhead for the actual polling but can deliver many events at once. By setting a higher \fIio collect interval\fR you allow libev to spend more time collecting I/O events, so you can handle more events per iteration, at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and -\&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. +\&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null bvalue will +introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. .Sp Likewise, by setting a higher \fItimeout collect interval\fR you allow libev to spend more time collecting timeouts, at the expense of increased latency (the watcher callback will be called later). \f(CW\*(C`ev_io\*(C'\fR watchers -will not be affected. -.Sp -Many programs can usually benefit by setting the io collect interval to -a value near \f(CW0.1\fR or so, which is often enough for interactive servers -(of course not for games), likewise for timeouts. It usually doesn't make -much sense to set it to a lower value than \f(CW0.01\fR, as this approsaches -the timing granularity of most systems. +will not be affected. Setting this to a non-null value will not introduce +any overhead in libev. +.Sp +Many (busy) programs can usually benefit by setting the io collect +interval to a value near \f(CW0.1\fR or so, which is often enough for +interactive servers (of course not for games), likewise for timeouts. It +usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR, +as this approsaches the timing granularity of most systems. .SH "ANATOMY OF A WATCHER" .IX Header "ANATOMY OF A WATCHER" A watcher is a structure that you create and register to record your @@ -1784,11 +1789,11 @@ It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C priority, to ensure that they are being run before any other watchers after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not activate (\*(L"feed\*(R") events into libev. While libev fully -supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did -their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event -loops those other event loops might be in an unusable state until their -\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with -others). +supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers +did their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other +(non\-libev) event loops those other event loops might be in an unusable +state until their \f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to +coexist peacefully with others). .PP \fIWatcher-Specific Functions and Data Members\fR .IX Subsection "Watcher-Specific Functions and Data Members" @@ -1978,7 +1983,7 @@ this. This is a rather advanced watcher type that lets you embed one event loop into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded loop, other types of watchers might be handled in a delayed or incorrect -fashion and must not be used). (See portability notes, below). +fashion and must not be used). .PP There are primarily two reasons you would want that: work around bugs and prioritise I/O. @@ -2048,21 +2053,6 @@ create it, and if that fails, use the normal loop for everything: \& else \& loop_lo = loop_hi; .Ve -.Sh "Portability notes" -.IX Subsection "Portability notes" -Kqueue is nominally embeddable, but this is broken on all BSDs that I -tried, in various ways. Usually the embedded event loop will simply never -receive events, sometimes it will only trigger a few times, sometimes in a -loop. Epoll is also nominally embeddable, but many Linux kernel versions -will always eport the epoll fd as ready, even when no events are pending. -.PP -While libev allows embedding these backends (they are contained in -\&\f(CW\*(C`ev_embeddable_backends ()\*(C'\fR), take extreme care that it will actually -work. -.PP -When in doubt, create a dynamic event loop forced to use sockets (this -usually works) and possibly another thread and a pipe or so to report to -your main event loop. .PP \fIWatcher-Specific Functions and Data Members\fR .IX Subsection "Watcher-Specific Functions and Data Members" |