*** empty log message ***

[software/libev.git] / ev.pod

diff --git a/ev.pod b/ev.pod
index 411fbb5f1a38cb0af2e56a0c39d6dc180df832bf..9845aff91cad874749bbe114158624ef6715064c 100644 (file)
--- a/ev.pod
+++ b/ev.pod
@@ -147,24 +147,70 @@ override the flags completely if it is found in the environment. This is
 useful to try out specific backends to test their performance, or to work
 around bugs.
 
 useful to try out specific backends to test their performance, or to work
 around bugs.
 

-=item C<EVMETHOD_SELECT>  (portable select backend)
+=item C<EVMETHOD_SELECT>  (value 1, portable select backend)

 
 

-=item C<EVMETHOD_POLL>    (poll backend, available everywhere except on windows)
+This is your standard select(2) backend. Not I<completely> standard, as
+libev tries to roll its own fd_set with no limits on the number of fds,
+but if that fails, expect a fairly low limit on the number of fds when
+using this backend. It doesn't scale too well (O(highest_fd)), but its usually
+the fastest backend for a low number of fds.

 
 

-=item C<EVMETHOD_EPOLL>   (linux only)
+=item C<EVMETHOD_POLL>    (value 2, poll backend, available everywhere except on windows)

 
 

-=item C<EVMETHOD_KQUEUE>  (some bsds only)
+And this is your standard poll(2) backend. It's more complicated than
+select, but handles sparse fds better and has no artificial limit on the
+number of fds you can use (except it will slow down considerably with a
+lot of inactive fds). It scales similarly to select, i.e. O(total_fds).

 
 

-=item C<EVMETHOD_DEVPOLL> (solaris 8 only)
+=item C<EVMETHOD_EPOLL>   (value 4, Linux)

 
 

-=item C<EVMETHOD_PORT>    (solaris 10 only)
+For few fds, this backend is a bit little slower than poll and select,
+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).

 
 

-If one or more of these are ored into the flags value, then only these
-backends will be tried (in the reverse order as given here). If one are
-specified, any backend will do.
+While stopping and starting an I/O watcher in the same iteration will
+result in some caching, there is still a syscall per such incident
+(because the fd could point to a different file description now), so its
+best to avoid that. Also, dup()ed file descriptors might not work very
+well if you register events for both fds.
+
+=item C<EVMETHOD_KQUEUE>  (value 8, most BSD clones)
+
+Kqueue deserves special mention, as at the time of this writing, it
+was broken on all BSDs except NetBSD (usually it doesn't work with
+anything but sockets and pipes, except on Darwin, where of course its
+completely useless). For this reason its not being "autodetected" unless
+you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).
+
+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 starting and stopping an I/O watcher does not cause an
+extra syscall as with epoll, it still adds up to four event changes per
+incident, so its best to avoid that.
+
+=item C<EVMETHOD_DEVPOLL> (value 16, Solaris 8)
+
+This is not implemented yet (and might never be).
+
+=item C<EVMETHOD_PORT>    (value 32, Solaris 10)
+
+This uses the Solaris 10 port mechanism. As with everything on Solaris,
+it's really slow, but it still scales very well (O(active_fds)).
+
+=item C<EVMETHOD_ALL>
+
+Try all backends (even potentially broken ones that wouldn't be tried
+with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
+C<EVMETHOD_ALL & ~EVMETHOD_KQUEUE>.

 
 =back
 
 
 =back
 

+If one or more of these are ored into the flags value, then only these
+backends will be tried (in the reverse order as given here). If none are
+specified, most compiled-in backend will be tried, usually in reverse
+order of their flag values :)
+

 =item struct ev_loop *ev_loop_new (unsigned int flags)
 
 Similar to C<ev_default_loop>, but always creates a new event loop that is
 =item struct ev_loop *ev_loop_new (unsigned int flags)
 
 Similar to C<ev_default_loop>, but always creates a new event loop that is