diff --git a/sys/conf/NOTES b/sys/conf/NOTES
--- a/sys/conf/NOTES
+++ b/sys/conf/NOTES
@@ -2610,6 +2610,7 @@
 options 	DEBUG_VFS_LOCKS	# enable VFS lock debugging
 options 	SOCKBUF_DEBUG	# enable sockbuf last record/mb tail checking
 options 	IFMEDIA_DEBUG	# enable debugging in net/if_media.c
+options 	NAMEI_DEBUG	# enable namei debugging
 
 #
 # Verbose SYSINIT
diff --git a/sys/conf/options b/sys/conf/options
--- a/sys/conf/options
+++ b/sys/conf/options
@@ -1033,3 +1033,6 @@
 # This option is insecure except in controlled environments where the static
 # environment's contents are known to be safe.
 PRESERVE_EARLY_KENV	opt_global.h
+
+# Debug namei operations
+NAMEI_DEBUG		opt_global.h
diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
--- a/sys/kern/vfs_lookup.c
+++ b/sys/kern/vfs_lookup.c
@@ -71,9 +71,6 @@
 
 #include <vm/uma.h>
 
-#define	NAMEI_DIAGNOSTIC 1
-#undef NAMEI_DIAGNOSTIC
-
 #ifdef INVARIANTS
 static void NDVALIDATE_impl(struct nameidata *, int);
 #define NDVALIDATE(ndp) NDVALIDATE_impl(ndp, __LINE__)
@@ -187,6 +184,11 @@
     &lookup_cap_dotdot_nonlocal, 0,
     "enables \"..\" components in path lookup in capability mode "
     "on non-local mount");
+#ifdef NAMEI_DEBUG
+static int namei_debug = NAMEI_DEBUG;
+SYSCTL_INT(_vfs, OID_AUTO, namei_debug, CTLFLAG_RWTUN, &namei_debug,
+    0, "enables debugging messages for namei operations");
+#endif
 
 static void
 nameicap_tracker_add(struct nameidata *ndp, struct vnode *dp)
@@ -1106,11 +1108,14 @@
 		error = ENAMETOOLONG;
 		goto bad;
 	}
-#ifdef NAMEI_DIAGNOSTIC
-	{ char c = *cp;
-	*cp = '\0';
-	printf("{%s}: ", cnp->cn_nameptr);
-	*cp = c; }
+#ifdef NAMEI_DEBUG
+	if (namei_debug) {
+		char c = *cp;
+
+		*cp = '\0';
+		printf("{%s}: ", cnp->cn_nameptr);
+		*cp = c;
+	}
 #endif
 	prev_ni_pathlen = ndp->ni_pathlen;
 	ndp->ni_pathlen -= cnp->cn_namelen;
@@ -1258,8 +1263,9 @@
 	 */
 	if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags))
 		cnp->cn_lkflags = LK_EXCLUSIVE;
-#ifdef NAMEI_DIAGNOSTIC
-	vn_printf(dp, "lookup in ");
+#ifdef NAMEI_DEBUG
+	if (namei_debug)
+		vn_printf(dp, "lookup in ");
 #endif
 	lkflags_save = cnp->cn_lkflags;
 	cnp->cn_lkflags = enforce_lkflags(dp->v_mount, cnp->cn_lkflags);
@@ -1267,8 +1273,9 @@
 	cnp->cn_lkflags = lkflags_save;
 	if (error != 0) {
 		KASSERT(ndp->ni_vp == NULL, ("leaf should be empty"));
-#ifdef NAMEI_DIAGNOSTIC
-		printf("not found\n");
+#ifdef NAMEI_DEBUG
+		if (namei_debug)
+			printf("not found\n");
 #endif
 		if ((error == ENOENT) &&
 		    (dp->v_vflag & VV_ROOT) && (dp->v_mount != NULL) &&
@@ -1321,8 +1328,9 @@
 	}
 
 good:
-#ifdef NAMEI_DIAGNOSTIC
-	printf("found\n");
+#ifdef NAMEI_DEBUG
+	if (namei_debug)
+		printf("found\n");
 #endif
 	dp = ndp->ni_vp;
 
@@ -1510,8 +1518,9 @@
 	 *
 	 * See a comment in vfs_lookup for cnp->cn_nameptr.
 	 */
-#ifdef NAMEI_DIAGNOSTIC
-	printf("{%s}: ", cnp->cn_nameptr);
+#ifdef NAMEI_DEBUG
+	if (namei_debug)
+		printf("{%s}: ", cnp->cn_nameptr);
 #endif
 
 	/*
@@ -1541,8 +1550,9 @@
 	/*
 	 * We now have a segment name to search for, and a directory to search.
 	 */
-#ifdef NAMEI_DIAGNOSTIC
-	vn_printf(dp, "search in ");
+#ifdef NAMEI_DEBUG
+	if (namei_debug)
+		vn_printf(dp, "search in ");
 #endif
 	if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) {
 		KASSERT(*vpp == NULL, ("leaf should be empty"));