diff --git a/ChangeLog b/ChangeLog
index 6603a56028..a5baf6cbe0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2010-07-27  Andreas Schwab  <schwab@redhat.com>
+
+	* manual/memory.texi (Malloc Tunable Parameters): Document
+	M_PERTURB.
+
 2010-07-26  Roland McGrath  <roland@redhat.com>
 
 	[BZ #11840]
diff --git a/manual/memory.texi b/manual/memory.texi
index 59ea1ee342..db63c3313b 100644
--- a/manual/memory.texi
+++ b/manual/memory.texi
@@ -702,6 +702,11 @@ be allocated via @code{mmap}.
 @item M_MMAP_MAX
 The maximum number of chunks to allocate with @code{mmap}.  Setting this
 to zero disables all use of @code{mmap}.
+@item M_PERTURB
+If non-zero, memory blocks are filled with values depending on some
+low order bits of this parameter when they are allocated (except when
+allocated by @code{calloc}) and freed.  This can be used to debug the
+use of uninitialized or freed heap memory.
 @end table
 
 @end deftypefun