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@ -129,7 +129,7 @@ |
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.\" ======================================================================== |
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.\" |
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.IX Title ""<STANDARD INPUT>" 1" |
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.TH "<STANDARD INPUT>" 1 "2007-11-18" "perl v5.8.8" "User Contributed Perl Documentation" |
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.TH "<STANDARD INPUT>" 1 "2007-11-22" "perl v5.8.8" "User Contributed Perl Documentation" |
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.SH "NAME" |
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libev \- a high performance full\-featured event loop written in C |
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.SH "SYNOPSIS" |
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@ -262,31 +262,69 @@ or setgid) then libev will \fInot\fR look at the environment variable |
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override the flags completely if it is found in the environment. This is |
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useful to try out specific backends to test their performance, or to work |
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around bugs. |
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.ie n .IP """EVMETHOD_SELECT"" (portable select backend)" 4 |
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.el .IP "\f(CWEVMETHOD_SELECT\fR (portable select backend)" 4 |
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.IX Item "EVMETHOD_SELECT (portable select backend)" |
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.PD 0 |
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.ie n .IP """EVMETHOD_POLL"" (poll backend, available everywhere except on windows)" 4 |
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.el .IP "\f(CWEVMETHOD_POLL\fR (poll backend, available everywhere except on windows)" 4 |
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.IX Item "EVMETHOD_POLL (poll backend, available everywhere except on windows)" |
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.ie n .IP """EVMETHOD_EPOLL"" (linux only)" 4 |
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.el .IP "\f(CWEVMETHOD_EPOLL\fR (linux only)" 4 |
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.IX Item "EVMETHOD_EPOLL (linux only)" |
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.ie n .IP """EVMETHOD_KQUEUE"" (some bsds only)" 4 |
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.el .IP "\f(CWEVMETHOD_KQUEUE\fR (some bsds only)" 4 |
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.IX Item "EVMETHOD_KQUEUE (some bsds only)" |
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.ie n .IP """EVMETHOD_DEVPOLL"" (solaris 8 only)" 4 |
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.el .IP "\f(CWEVMETHOD_DEVPOLL\fR (solaris 8 only)" 4 |
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.IX Item "EVMETHOD_DEVPOLL (solaris 8 only)" |
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.ie n .IP """EVMETHOD_PORT"" (solaris 10 only)" 4 |
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.el .IP "\f(CWEVMETHOD_PORT\fR (solaris 10 only)" 4 |
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.IX Item "EVMETHOD_PORT (solaris 10 only)" |
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.PD |
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If one or more of these are ored into the flags value, then only these |
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backends will be tried (in the reverse order as given here). If one are |
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specified, any backend will do. |
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.ie n .IP """EVMETHOD_SELECT"" (value 1, portable select backend)" 4 |
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.el .IP "\f(CWEVMETHOD_SELECT\fR (value 1, portable select backend)" 4 |
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.IX Item "EVMETHOD_SELECT (value 1, portable select backend)" |
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This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
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libev tries to roll its own fd_set with no limits on the number of fds, |
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but if that fails, expect a fairly low limit on the number of fds when |
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using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
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the fastest backend for a low number of fds. |
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.ie n .IP """EVMETHOD_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
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.el .IP "\f(CWEVMETHOD_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
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.IX Item "EVMETHOD_POLL (value 2, poll backend, available everywhere except on windows)" |
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And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than |
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select, but handles sparse fds better and has no artificial limit on the |
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number of fds you can use (except it will slow down considerably with a |
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lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
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.ie n .IP """EVMETHOD_EPOLL"" (value 4, Linux)" 4 |
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.el .IP "\f(CWEVMETHOD_EPOLL\fR (value 4, Linux)" 4 |
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.IX Item "EVMETHOD_EPOLL (value 4, Linux)" |
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For few fds, this backend is a bit little slower than poll and select, |
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but it scales phenomenally better. While poll and select usually scale like |
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O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
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either O(1) or O(active_fds). |
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.Sp |
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While stopping and starting an I/O watcher in the same iteration will |
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result in some caching, there is still a syscall per such incident |
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(because the fd could point to a different file description now), so its |
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best to avoid that. Also, \fIdup()\fRed file descriptors might not work very |
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well if you register events for both fds. |
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.ie n .IP """EVMETHOD_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
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.el .IP "\f(CWEVMETHOD_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
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.IX Item "EVMETHOD_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 all BSDs except NetBSD (usually it doesn't work with |
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anything but sockets and pipes, except on Darwin, where of course its |
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completely useless). For this reason its not being \*(L"autodetected\*(R" unless |
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you explicitly specify the flags (i.e. you don't use \s-1EVFLAG_AUTO\s0). |
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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, of |
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course). While starting and stopping an I/O watcher does not cause an |
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extra syscall as with epoll, it still adds up to four event changes per |
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incident, so its best to avoid that. |
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.ie n .IP """EVMETHOD_DEVPOLL"" (value 16, Solaris 8)" 4 |
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.el .IP "\f(CWEVMETHOD_DEVPOLL\fR (value 16, Solaris 8)" 4 |
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.IX Item "EVMETHOD_DEVPOLL (value 16, Solaris 8)" |
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This is not implemented yet (and might never be). |
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.ie n .IP """EVMETHOD_PORT"" (value 32, Solaris 10)" 4 |
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.el .IP "\f(CWEVMETHOD_PORT\fR (value 32, Solaris 10)" 4 |
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.IX Item "EVMETHOD_PORT (value 32, Solaris 10)" |
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This uses the Solaris 10 port mechanism. As with everything on Solaris, |
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it's really slow, but it still scales very well (O(active_fds)). |
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.ie n .IP """EVMETHOD_ALL""" 4 |
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.el .IP "\f(CWEVMETHOD_ALL\fR" 4 |
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.IX Item "EVMETHOD_ALL" |
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Try all backends (even potentially broken ones). Since this is a mask, you |
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can do stuff like \f(CW\*(C`EVMETHOD_ALL & ~EVMETHOD_KQUEUE\*(C'\fR. |
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.RE |
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.RS 4 |
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.Sp |
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If one or more of these are ored into the flags value, then only these |
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backends will be tried (in the reverse order as given here). If none are |
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specified, most compiled-in backend will be tried, usually in reverse |
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order of their flag values :) |
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.RE |
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.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
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.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
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Marc Alexander Lehmann
15 years ago