doc: describe how kernel inotify support affects tail -f

* doc/coreutils.texi (tail invocation) [-f]: Mention how inotify
kernel support makes a difference.
Prompted by http://bugzilla.redhat.com/662900

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 289c0ba..dfaf4c9 100644 (file)
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -2830,6 +2830,11 @@ no @var{file} operand is specified and standard input is a FIFO or a pipe.
 Likewise, the @option{-f} option has no effect for any
 operand specified as @samp{-}, when standard input is a FIFO or a pipe.
 
+With kernel inotify support, output is asynchronous and generally very prompt.
+Otherwise, @command{tail} sleeps for one second between checks---
+use @option{--sleep-interval=@var{N}} to change that default---which can
+make the output appear slightly less responsive or bursty.
+
 @item -F
 @opindex -F
 This option is the same as @option{--follow=name --retry}.  That is, tail