Index: sys/vm/vm_radix.c
===================================================================
--- sys/vm/vm_radix.c	(revision 229932)
+++ sys/vm/vm_radix.c	(working copy)
@@ -432,6 +432,9 @@ vm_radix_leaf(struct vm_radix *rtree, vm_pindex_t
 	start = *startp;
 restart:
 	level = vm_radix_height(rtree, &rnode);
+	if (start == end)
+		CTR3(KTR_FLO, "leaf: start %ju end %ju level %d",
+		    (uintmax_t)start, (uintmax_t)end, level);
 	if (start > VM_RADIX_MAX(level) || (end && start >= end)) {
 		rnode = NULL;
 		goto out;
Index: sys/sys/ktr.h
===================================================================
--- sys/sys/ktr.h	(revision 229932)
+++ sys/sys/ktr.h	(working copy)
@@ -75,6 +75,7 @@
 #define	KTR_INET6	0x10000000		/* IPv6 stack */
 #define	KTR_SCHED	0x20000000		/* Machine parsed sched info. */
 #define	KTR_BUF		0x40000000		/* Buffer cache */
+#define	KTR_FLO		0x80000000		/* Test */
 #define	KTR_ALL		0x7fffffff
 
 /* Trace classes to compile in */