diff --git a/share/man/man9/MUTEX_PROFILING.9 b/share/man/man9/MUTEX_PROFILING.9
index bbca8ab4ed8e..7f8baf255eb2 100644
--- a/share/man/man9/MUTEX_PROFILING.9
+++ b/share/man/man9/MUTEX_PROFILING.9
@@ -1,5 +1,6 @@
 .\"-
 .\" Copyright (c) 2004 Dag-Erling Coïdan Smørgrav
+.\" Copyright (c) 2005 Robert N. M. Watson
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
@@ -158,6 +159,12 @@ option also prevents inlining of the mutex code, which results in a
 fairly severe performance penalty.
 It should therefore only be enabled on systems where mutex profiling
 is actually needed.
+.Dv MUTEX_PROFILING
+will introduce a substantial performance overhead that is easily
+monitorable using other profiling tools, so combining profiling tools
+with
+.Dv MUTEX_PROFILING
+is not recommended.
 .Pp
 Measurements are made and stored in nanoseconds using
 .Xr nanotime 9 ,
@@ -165,3 +172,19 @@ but are presented in microseconds.
 This should still be sufficient for the locks one would be most
 interested in profiling (those that are held long and/or acquired
 often).
+.Pp
+.Dv MUTEX_PROFILING
+should generally not be used in combination with other debugging options, as
+the results may be strongly affected by interactions between the features.
+In particular,
+.Dv MUTEX_PROFILING
+will report higher than normal
+.Xr uma 9
+lock contention when run with
+.Dv INVARIANTS
+due to extra locking that occurs when
+.Dv INVARIANTS
+is present; likewise, using it in combination with
+.Dv WITNESS
+with
+will lead to much higher lock hold times and contention in profiling output.