*** empty log message ***

[software/libev.git] / ev.3

diff --git a/ev.3 b/ev.3
index be03d68dbc1cbb4941446e591c39dbfb55e4b1be..6494928f3b14bf9a202f40637ab72c8c6d27d1ff 100644 (file)
--- a/ev.3
+++ b/ev.3
@@ -129,7 +129,7 @@
 .\" ========================================================================
 .\"
 .IX Title "EV 1"
 .\" ========================================================================
 .\"
 .IX Title "EV 1"

-.TH EV 1 "2007-12-21" "perl v5.8.8" "User Contributed Perl Documentation"
+.TH EV 1 "2007-12-22" "perl v5.8.8" "User Contributed Perl Documentation"

 .SH "NAME"
 libev \- a high performance full\-featured event loop written in C
 .SH "SYNOPSIS"
 .SH "NAME"
 libev \- a high performance full\-featured event loop written in C
 .SH "SYNOPSIS"


@@ -257,6 +257,11 @@ 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.
 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 "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.

 .IP "int ev_version_major ()" 4
 .IX Item "int ev_version_major ()"
 .PD 0
 .IP "int ev_version_major ()" 4
 .IX Item "int ev_version_major ()"
 .PD 0


@@ -465,7 +470,7 @@ but it scales phenomenally better. While poll and select usually scale
 like O(total_fds) where n is the total number of fds (or the highest fd),
 epoll scales either O(1) or O(active_fds). The epoll design has a number
 of shortcomings, such as silently dropping events in some hard-to-detect
 like O(total_fds) where n is the total number of fds (or the highest fd),
 epoll scales either O(1) or O(active_fds). The epoll design has a number
 of shortcomings, such as silently dropping events in some hard-to-detect

-cases and rewuiring a syscall per fd change, no fork support and bad
+cases and rewiring a syscall per fd change, no fork support and bad

 support for dup:
 .Sp
 While stopping, setting and starting an I/O watcher in the same iteration
 support for dup:
 .Sp
 While stopping, setting and starting an I/O watcher in the same iteration


@@ -481,20 +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
 .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
 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
 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)"
 .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)"


@@ -726,6 +734,43 @@ Example: For some weird reason, unregister the above signal handler again.
 \&  ev_ref (loop);
 \&  ev_signal_stop (loop, &exitsig);
 .Ve
 \&  ev_ref (loop);
 \&  ev_signal_stop (loop, &exitsig);
 .Ve

+.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 (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
+invoke timer/periodic callbacks and I/O callbacks with minimum latency.
+.Sp
+Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
+allows libev to delay invocation of I/O and timer/periodic callbacks to
+increase efficiency of loop iterations.
+.Sp
+The background is that sometimes your program runs just fast enough to
+handle one (or very few) event(s) per loop iteration. While this makes
+the program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
+events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
+overhead for the actual polling but can deliver many events at once.
+.Sp
+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. 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. 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
 .SH "ANATOMY OF A WATCHER"
 .IX Header "ANATOMY OF A WATCHER"
 A watcher is a structure that you create and register to record your


@@ -1107,8 +1152,8 @@ This is how one would do it normally anyway, the important point is that
 the libev application should not optimise around libev but should leave
 optimisations to libev.
 .PP
 the libev application should not optimise around libev but should leave
 optimisations to libev.
 .PP

-\fIThs special problem of dup'ed file descriptors\fR
-.IX Subsection "Ths special problem of dup'ed file descriptors"
+\fIThe special problem of dup'ed file descriptors\fR
+.IX Subsection "The special problem of dup'ed file descriptors"

 .PP
 Some backends (e.g. epoll), cannot register events for file descriptors,
 but only events for the underlying file descriptions. That menas when you
 .PP
 Some backends (e.g. epoll), cannot register events for file descriptors,
 but only events for the underlying file descriptions. That menas when you


@@ -1744,11 +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
 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"
 .PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"


@@ -1938,7 +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
 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.
 .PP
 There are primarily two reasons you would want that: work around bugs and
 prioritise I/O.


@@ -2008,21 +2053,6 @@ create it, and if that fails, use the normal loop for everything:
 \&  else
 \&    loop_lo = loop_hi;
 .Ve
 \&  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"
 .PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"


@@ -2503,6 +2533,10 @@ runtime if successful). Otherwise no use of the realtime clock option will
 be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
 (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the
 note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
 be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
 (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the
 note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.

+.IP "\s-1EV_USE_NANOSLEEP\s0" 4
+.IX Item "EV_USE_NANOSLEEP"
+If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
+and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.

 .IP "\s-1EV_USE_SELECT\s0" 4
 .IX Item "EV_USE_SELECT"
 If undefined or defined to be \f(CW1\fR, libev will compile in support for the
 .IP "\s-1EV_USE_SELECT\s0" 4
 .IX Item "EV_USE_SELECT"
 If undefined or defined to be \f(CW1\fR, libev will compile in support for the