diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
index 87764ba12..4de02673b 100644
--- a/man2/perf_event_open.2
+++ b/man2/perf_event_open.2
@@ -796,7 +796,16 @@ If set, don't count when the CPU is idle.
 .IR "mmap"
 The
 .I mmap
-bit enables recording of exec mmap events.
+bit enables generation of
+.I PERF_RECORD_MMAP
+samples for every
+.BR mmap (2)
+call that has
+.I PROT_EXEC
+set.
+This allows tools to notice new executable code being mapped into
+a program (dynamic shared libraries for example)
+so that addresses can be mapped back to the original code.
 .TP
 .IR "comm"
 The
@@ -875,8 +884,14 @@ See also
 .IR "mmap_data" " (Since Linux 2.6.36)"
 The counterpart of the
 .I mmap
-field, but enables including data mmap events
-in the ring-buffer.
+field.
+This enables generation of
+.I PERF_RECORD_MMAP
+samples for
+.BR mmap (2)
+calls that do not have
+.I PROT_EXEC
+set (for example data and SysV shared memory).
 .TP
 .IR "sample_id_all" " (Since Linux 2.6.38)"
 If set, then TID, TIME, ID, STREAM_ID, and CPU can