Index: src/sys/vm/uma_core.c
===================================================================
RCS file: /home/ncvs/src/sys/vm/uma_core.c,v
retrieving revision 1.100
diff -u -r1.100 uma_core.c
--- src/sys/vm/uma_core.c	4 Jul 2004 16:07:44 -0000	1.100
+++ src/sys/vm/uma_core.c	8 Jul 2004 18:28:23 -0000
@@ -1021,7 +1021,7 @@
 
 	keg->uk_rsize = rsize;
 
-	rsize += 1;	/* Account for the byte of linkage */
+	rsize += UMA_FRITM_SZ;	/* Account for the linkage */
 	keg->uk_ipers = (UMA_SLAB_SIZE - sizeof(struct uma_slab)) / rsize;
 	keg->uk_ppera = 1;
 
@@ -1044,6 +1044,11 @@
 		ipers = UMA_SLAB_SIZE / keg->uk_rsize;
 		if ((keg->uk_flags & UMA_ZONE_REFCNT) ||
 		    (ipers > keg->uk_ipers)) {
+#ifdef UMA_DEBUG
+			printf("UMA decided we need to go offpage for "
+			    "zone: %s, calculated ipers: %d\n",
+			    zone->uz_name, ipers);
+#endif
 			keg->uk_flags |= UMA_ZONE_OFFPAGE;
 			if ((keg->uk_flags & UMA_ZONE_MALLOC) == 0)
 				keg->uk_flags |= UMA_ZONE_HASH;
@@ -1131,12 +1136,13 @@
 		keg->uk_init = zero_init;
 
 	/*
-	 * The +1 byte added to uk_size is to account for the byte of
+	 * The +UMA_FRITM_SZ added to uk_size is to account for the
 	 * linkage that is added to the size in zone_small_init().  If
 	 * we don't account for this here then we may end up in
 	 * zone_small_init() with a calculated 'ipers' of 0.
 	 */
-	if ((keg->uk_size+1) > (UMA_SLAB_SIZE - sizeof(struct uma_slab)))
+	if ((keg->uk_size+UMA_FRITM_SZ) >
+	    (UMA_SLAB_SIZE - sizeof(struct uma_slab)))
 		zone_large_init(zone);
 	else
 		zone_small_init(zone);
@@ -1178,13 +1184,14 @@
 		int totsize;
 
 		/* Size of the slab struct and free list */
-		totsize = sizeof(struct uma_slab) + keg->uk_ipers;
+		totsize = sizeof(struct uma_slab) +
+		    keg->uk_ipers * UMA_FRITM_SZ;
 		if (totsize & UMA_ALIGN_PTR)
 			totsize = (totsize & ~UMA_ALIGN_PTR) +
 			    (UMA_ALIGN_PTR + 1);
 		keg->uk_pgoff = UMA_SLAB_SIZE - totsize;
 		totsize = keg->uk_pgoff + sizeof(struct uma_slab)
-		    + keg->uk_ipers;
+		    + keg->uk_ipers * UMA_FRITM_SZ;
 		/* I don't think it's possible, but I'll make sure anyway */
 		if (totsize > UMA_SLAB_SIZE) {
 			printf("zone %s ipers %d rsize %d size %d\n",
@@ -1465,6 +1472,7 @@
 	slabsize = UMA_SLAB_SIZE - sizeof(struct uma_slab);
 	slabsize /= UMA_MAX_WASTE;
 	slabsize++;			/* In case there it's rounded */
+	slabsize *= UMA_FRITM_SZ;	/* sz of ea freeref in account */
 	slabsize += sizeof(struct uma_slab);
 
 	/* Now make a zone for slab headers */
@@ -1480,7 +1488,7 @@
 	slabsize = UMA_SLAB_SIZE - sizeof(struct uma_slab_refcnt);
 	slabsize /= UMA_MAX_WASTE;
 	slabsize++;
-	slabsize += 4 * slabsize;
+	slabsize *= UMA_FRITMREF_SZ;
 	slabsize += sizeof(struct uma_slab_refcnt);
 	slabrefzone = uma_zcreate("UMA RCntSlabs",
 				  slabsize,
Index: src/sys/vm/uma_int.h
===================================================================
RCS file: /home/ncvs/src/sys/vm/uma_int.h,v
retrieving revision 1.24
diff -u -r1.24 uma_int.h
--- src/sys/vm/uma_int.h	31 May 2004 21:46:05 -0000	1.24
+++ src/sys/vm/uma_int.h	8 Jul 2004 18:28:23 -0000
@@ -232,10 +232,10 @@
 		unsigned long	_us_size;	/* Size of allocation */
 	} us_type;
 	SLIST_ENTRY(uma_slab)	us_hlink;	/* Link for hash table */
+	u_int16_t	us_freecount;		/* How many are free? */
 	u_int8_t	*us_data;		/* First item */
 	u_int8_t	us_flags;		/* Page flags see uma.h */
-	u_int8_t	us_freecount;	/* How many are free? */
-	u_int8_t	us_firstfree;	/* First free item index */
+	u_int8_t	us_firstfree;		/* First free item index */
 };
 
 /* The standard slab structure */
@@ -266,6 +266,15 @@
 #define	us_flags	us_head.us_flags
 #define	us_freecount	us_head.us_freecount
 #define	us_firstfree	us_head.us_firstfree
+
+/*
+ * These give us the size of one free item reference within our corresponding
+ * uma_slab structures, so that our calculations during zone setup are correct
+ * regardless of what the compiler decides to do with padding the structure
+ * arrays within uma_slab.
+ */
+#define	UMA_FRITM_SZ	(sizeof(struct uma_slab) - sizeof(struct uma_slab_head))
+#define	UMA_FRITMREF_SZ	(sizeof(struct uma_slab_refcnt) - sizeof(struct uma_slab_head))
 
 typedef struct uma_slab * uma_slab_t;
 typedef struct uma_slab_refcnt * uma_slabrefcnt_t;