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