Document the inadvisability of enabling sendfile.

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@1418 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/varnishd.1

@@ -28,7 +28,7 @@
 .\"
 .\" $Id$
 .\"
-.Dd May 1, 2007
+.Dd May 14, 2007
 .Dt VARNISHD 1
 .Os
 .Sh NAME
@@ -372,7 +372,10 @@ instead of
 This is not likely to have any effect unless the working set is too
 large to fit in physical memory.
 .Pp
-The default is 8192 bytes, which is probably too low.
+Note that several operating systems have known bugs which make it
+inadvisable to use this.
+.Pp
+The default is -1, which disables the use of sendfile altogether.
 .It Va send_timeout
 The time to wait before dropping the connection to a client which is
 not accepting data sent to it.