Index: sys/vm/vm_reserv.c
===================================================================
--- sys/vm/vm_reserv.c
+++ sys/vm/vm_reserv.c
@@ -1244,8 +1244,16 @@
 	int bitpos, bits_left, i, hi, lo, n;
 
 	vm_reserv_assert_locked(rv);
+	KASSERT(npages <= VM_LEVEL_0_NPAGES - 1,
+	    ("%s: Too many pages", __FUNCTION__));
 	size = npages << PAGE_SHIFT;
+	KASSERT(size <= boundary,
+	    ("%s: Size overflows boundary", __FUNCTION__));
 	pa = VM_PAGE_TO_PHYS(&rv->pages[0]);
+	KASSERT(pa + VM_LEVEL_0_SIZE - size >= low,
+	    ("%s: This entire reservation is too low", __FUNCTION__));
+	KASSERT(pa + size <= high,
+	    ("%s: This entire reservation is too high", __FUNCTION__));
 	lo = (pa < low) ?
 	    ((low + PAGE_MASK - pa) >> PAGE_SHIFT) : 0;
 	i = lo / NBPOPMAP;
@@ -1277,23 +1285,29 @@
 			}
 			hi = NBPOPMAP * i + bitpos;
 			pa = VM_PAGE_TO_PHYS(&rv->pages[lo]);
-			if ((pa & (alignment - 1)) != 0) {
+
+			if (0 < (((alignment - 1) & -pa) >> PAGE_SHIFT)) {
 				/* Skip to next aligned page. */
-				lo += (((pa - 1) | (alignment - 1)) + 1) >>
-				    PAGE_SHIFT;
+				lo += ((alignment - 1) & -pa) >> PAGE_SHIFT;
 				if (lo >= VM_LEVEL_0_NPAGES)
 					return (false);
 				pa = VM_PAGE_TO_PHYS(&rv->pages[lo]);
 			}
-			if (((pa ^ (pa + size - 1)) & ~(boundary - 1)) != 0) {
+			KASSERT((pa & (alignment - 1)) == 0,
+			    ("%s: adjusted address does not align to %lx",
+			        __FUNCTION__, alignment));
+
+			if (npages > (((boundary - 1) & -pa) >> PAGE_SHIFT)) {
 				/* Skip to next boundary-matching page. */
-				lo += (((pa - 1) | (boundary - 1)) + 1) >>
-				    PAGE_SHIFT;
+				lo += ((boundary - 1) & -pa) >> PAGE_SHIFT;
 				if (lo >= VM_LEVEL_0_NPAGES)
 					return (false);
 				pa = VM_PAGE_TO_PHYS(&rv->pages[lo]);
 			}
-			if (lo * PAGE_SIZE + size <= hi * PAGE_SIZE)
+			KASSERT((((pa ^ (pa + size - 1)) & -boundary) == 0),
+			    ("%s: adjusted address spans boundary to %lx",
+			        __FUNCTION__, boundary));
+			if (lo + npages <= hi)
 				return (true);
 			lo = hi;
 		}
@@ -1326,6 +1340,8 @@
 	marker = &vm_rvd[domain].marker;
 	queue = &vm_rvd[domain].partpop;
 	size = npages << PAGE_SHIFT;
+	if (size > boundary)
+		return (false);
 
 	vm_reserv_domain_scan_lock(domain);
 	vm_reserv_domain_lock(domain);
@@ -1480,6 +1496,90 @@
 	return (new_end);
 }
 
+/*
+ * XXX
+ */
+static vm_object_t
+debug_vm_reserv_reclaim_contig_pre(void)
+{
+	vm_object_t object;
+	int i;
+
+	object = vm_object_allocate(OBJT_DEFAULT, 512);
+	object->flags |= OBJ_COLORED;
+	object->pg_color = 0;
+
+	/*
+	 * Change the set of vm_page_alloc() calls to vary the allocated versus
+	 * free pattern that vm_reserv_reclaim_contig() has to handle.
+	 */
+	VM_OBJECT_WLOCK(object);
+	for (i = 0; i < 512; i += 17)
+		(void)vm_page_alloc(object, i, VM_ALLOC_NORMAL | VM_ALLOC_NOBUSY);
+	VM_OBJECT_WUNLOCK(object);
+
+	return (object);
+}
+
+/*
+ * XXX
+ */
+static uint64_t
+debug_vm_reserv_reclaim_contig_test(vm_object_t object)
+{
+	vm_reserv_t rv;
+
+	rv = LIST_FIRST(&object->rvq);
+	vm_reserv_lock(rv);
+	if (rv->object != object) {
+		vm_reserv_unlock(rv);
+		return (~(uint64_t)0);
+	}
+	vm_reserv_domain_lock(rv->domain);
+	if (rv->inpartpopq) {
+		TAILQ_REMOVE(&vm_rvd[rv->domain].partpop, rv, partpopq);
+		rv->inpartpopq = FALSE;
+	}
+	vm_reserv_domain_unlock(rv->domain);
+	uint64_t tsc = rdtscp();
+	vm_reserv_reclaim_contig(rv->domain, 16, 0, 0x80000000, 0x10000, 1);
+	tsc = rdtscp() - tsc;
+	vm_reserv_unlock(rv);
+	return (tsc);
+}
+
+#define	NOBJECTS	997
+
+/*
+ * To run a test, use the command: sysctl debug.vm_reserv_reclaim_contig=1
+ */
+static int
+debug_vm_reserv_reclaim_contig(SYSCTL_HANDLER_ARGS)
+{
+	vm_object_t object[NOBJECTS];
+	uint64_t total_tsc;
+	int error, i, j;
+
+	i = 0;
+	error = sysctl_handle_int(oidp, &i, 0, req);
+	if (error != 0)
+		return (error);
+	if (i != 0) {
+		for (j = 0; j < NOBJECTS; j++)
+			object[j] = debug_vm_reserv_reclaim_contig_pre();
+		total_tsc = 0;
+		for (j = 0; j < NOBJECTS; j++)
+			total_tsc += debug_vm_reserv_reclaim_contig_test(object[j]);
+		uprintf("\ncycles/break: %lu\n", total_tsc / NOBJECTS);
+		for (j = 0; j < NOBJECTS; j++)
+			vm_object_deallocate(object[j]);
+	}
+	return (0);
+}
+
+SYSCTL_PROC(_debug, OID_AUTO, vm_reserv_reclaim_contig, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
+    debug_vm_reserv_reclaim_contig, "I", "set to trigger vm_reserv_reclaim_contig event");
+
 /*
  * Returns the superpage containing the given page.
  */