Index: sys/kern/subr_blist.c
===================================================================
--- sys/kern/subr_blist.c
+++ sys/kern/subr_blist.c
@@ -90,6 +90,7 @@
 #ifdef _KERNEL
 
 #include <sys/param.h>
+#include <sys/sysctl.h>
 #include <sys/systm.h>
 #include <sys/lock.h>
 #include <sys/kernel.h>
@@ -382,6 +383,14 @@
     blist_destroy(save);
 }
 
+static long bighint_updates, bighint_reads, bighint_fails, bighint_blocks, bighint_resets;
+static SYSCTL_NODE(_debug, OID_AUTO, counters, CTLFLAG_RD, 0, "");
+SYSCTL_ULONG(_debug_counters, OID_AUTO, bighint_updates, CTLFLAG_RD, &bighint_updates, 0, "");
+SYSCTL_ULONG(_debug_counters, OID_AUTO, bighint_reads, CTLFLAG_RD, &bighint_reads, 0, "");
+SYSCTL_ULONG(_debug_counters, OID_AUTO, bighint_fails, CTLFLAG_RD, &bighint_fails, 0, "");
+SYSCTL_ULONG(_debug_counters, OID_AUTO, bighint_blocks, CTLFLAG_RD, &bighint_blocks, 0, "");
+SYSCTL_ULONG(_debug_counters, OID_AUTO, bighint_resets, CTLFLAG_RD, &bighint_resets, 0, "");
+
 #ifdef BLIST_DEBUG
 
 /*
@@ -686,6 +695,7 @@
 		 * Update bighint.  There is no allocation bigger than range1
 		 * starting in this leaf.
 		 */
+		atomic_add_long(&bighint_updates, 1);
 		scan->bm_bighint = range1;
 		return (SWAPBLK_NONE);
 	}
@@ -740,6 +750,7 @@
 		 * Update bighint.  There is no allocation bigger than range1
 		 * available in this leaf after this allocation completes.
 		 */
+		atomic_add_long(&bighint_updates, 1);
 		scan->bm_bighint = range1;
 	} else {
 		/* Clear the bits of mask at position 'hi' and higher. */
@@ -797,6 +808,7 @@
 		bit = mask & -mask;
 		digit = bitpos(bit);
 		i = 1 + digit * skip;
+		atomic_add_long(&bighint_reads, 1);
 		if (count <= scan[i].bm_bighint) {
 			/*
 			 * The allocation might fit beginning in the i'th subtree.
@@ -808,7 +820,9 @@
 					scan->bm_bitmap ^= bit;
 				return (r);
 			}
-		}
+			atomic_add_long(&bighint_fails, 1);
+		} else
+			atomic_add_long(&bighint_blocks, 1);
 		cursor = blk;
 	} while ((mask ^= bit) != 0);
 
@@ -817,8 +831,10 @@
 	 * scanned, and the last tree node is allocated, update bighint.
 	 */
 	if (scan_from_start && !(digit == BLIST_META_RADIX - 1 &&
-	    scan[i].bm_bighint == BLIST_MAX_ALLOC))
+	    scan[i].bm_bighint == BLIST_MAX_ALLOC)) {
+		atomic_add_long(&bighint_updates, 1);
 		scan->bm_bighint = count - 1;
+	}
 
 	return (SWAPBLK_NONE);
 }
@@ -866,6 +882,7 @@
 	 * If we just shoehorn it, a little extra overhead will be incurred
 	 * on the next allocation (but only that one typically).
 	 */
+	atomic_add_long(&bighint_resets, 1);
 	scan->bm_bighint = BLIST_MAX_ALLOC;
 
 	if (radix == BLIST_BMAP_RADIX)