Index: sys/kern/subr_blist.c
===================================================================
--- sys/kern/subr_blist.c
+++ sys/kern/subr_blist.c
@@ -190,6 +190,14 @@
 	    ((u_daddr_t)-1 >> (BLIST_BMAP_RADIX - (n + count))));
 }
 
+/*
+ * Return the argument with all but the least significant 1 bit cleared.
+ */
+static inline u_addr_t
+leastbit(u_addr_t val)
+{
+  return (val & -val);
+}
 
 /*
  * Use binary search, or a faster method, to find the 1 bit in a u_daddr_t.
@@ -569,7 +577,7 @@
 			if (gap_stats_counting(stats))
 				diff ^= 1;
 			while (diff != 0) {
-				bit = diff & -diff;
+				bit = leastbit(diff);
 				update_gap_stats(stats, i + bitpos(bit));
 				diff ^= bit;
 			}
@@ -644,8 +652,7 @@
 /*
  * BLST_LEAF_ALLOC() -	allocate at a leaf in the radix tree (a bitmap).
  *
- *	This is the core of the allocator and is optimized for the
- *	BLIST_BMAP_RADIX block allocation case.  Otherwise, execution
+ *	This is the core of the allocator.  Execution
  *	time is proportional to log2(count) + bitpos time.
  */
 static daddr_t
@@ -658,7 +665,17 @@
 	count1 = count - 1;
 	num_shifts = fls(count1);
 	mask = scan->bm_bitmap;
-	while ((-mask & ~mask) != 0 && num_shifts > 0) {
+	while (num_shifts > 0) {
+		if (leastbit(mask) == -mask) {
+			/*
+			 * Anding mask with right-shifted versions of itself
+			 * won't change mask, so there's no point in more
+			 * iteration, and growing range1 further will just
+			 * make hinting less effective.
+			 */
+			break;
+		}
+
 		/*
 		 * If bit i is set in mask, then bits in [i, i+range1] are set
 		 * in scan->bm_bitmap.  The value of range1 is equal to
@@ -666,9 +683,9 @@
 		 * while preserving these invariants.  The updates to mask leave
 		 * fewer bits set, but each bit that remains set represents a
 		 * longer string of consecutive bits set in scan->bm_bitmap.
-		 * If more updates to mask cannot clear more bits, because mask
-		 * is partitioned with all 0 bits preceding all 1 bits, the loop
-		 * terminates immediately.
+		 * The length of the 1-strings in scan->bm_bitmap represented
+		 * by a bit set in mask doubles, or one-less-than-doubles, with
+		 * each iteration.
 		 */
 		num_shifts--;
 		range_ext = range1 + ((count1 >> num_shifts) & 1);
@@ -781,7 +798,7 @@
 	 * Examine the nonempty subtree associated with each bit set in mask.
 	 */
 	do {
-		bit = mask & -mask;
+		bit = leastbit(mask);
 		digit = bitpos(bit);
 		i = 1 + digit * skip;
 		if (count <= scan[i].bm_bighint) {
@@ -1023,7 +1040,7 @@
 	mask = scan->bm_bitmap;
 	/* Examine the nonempty subtree associated with each bit set in mask */
 	do {
-		bit = mask & -mask;
+		bit = leastbit(mask);
 		digit = bitpos(bit);
 		blst_radix_print(&scan[1 + digit * skip], blk + digit * radix,
 		    radix, tab);