profiler: document prefix arg for tree expansion

* doc/lispref/debugging.texi (Profiling):
* lisp/profiler.el (profiler-report-toggle-entry): Document use of
prefix argument to expand whole call trees.

1 files changed, 3 insertions, 2 deletions

diff --git a/doc/lispref/debugging.texi b/doc/lispref/debugging.texi
index 98c47052cb0..2f83b4040fa 100644
--- a/doc/lispref/debugging.texi
+++ b/doc/lispref/debugging.texi
@@ -840,8 +840,9 @@ called, followed by how much resource (processor or memory) it used in
 absolute and percentage times since profiling started.  If a given
 line has a @samp{+} symbol at the left-hand side, you can expand that
 line by typing @key{RET}, in order to see the function(s) called by
-the higher-level function.  Pressing @key{RET} again will collapse
-back to the original state.
+the higher-level function.  Use a prefix argument (@key{C-u RET}) to
+see the whole call tree below a function.  Pressing @key{RET} again
+will collapse back to the original state.
 
 Press @kbd{j} or @kbd{mouse-2} to jump to the definition of a function.
 Press @kbd{d} to view a function's documentation.