diff -ruN /usr/src.org/sys/kern/uipc_mbuf.c /usr/src/sys/kern/uipc_mbuf.c
--- /usr/src.org/sys/kern/uipc_mbuf.c	Sun Oct 15 00:54:28 2000
+++ /usr/src/sys/kern/uipc_mbuf.c	Sun Oct 15 02:18:34 2000
@@ -60,6 +60,7 @@
 int	max_datalen;
 int	nmbclusters;
 int	nmbufs;
+int	nmbcnt;
 u_long	m_mballoc_wid = 0;
 u_long	m_clalloc_wid = 0;
 
@@ -91,11 +92,14 @@
 	   &nmbclusters, 0, "Maximum number of mbuf clusters available");
 SYSCTL_INT(_kern_ipc, OID_AUTO, nmbufs, CTLFLAG_RD, &nmbufs, 0,
 	   "Maximum number of mbufs available"); 
+SYSCTL_INT(_kern_ipc, OID_AUTO, nmbcnt, CTLFLAG_RD, &nmbcnt, 0,
+	   "Maximum number of ext_buf counters available");
 #ifndef NMBCLUSTERS
 #define NMBCLUSTERS	(512 + MAXUSERS * 16)
 #endif
 TUNABLE_INT_DECL("kern.ipc.nmbclusters", NMBCLUSTERS, nmbclusters);
 TUNABLE_INT_DECL("kern.ipc.nmbufs", NMBCLUSTERS * 4, nmbufs);
+TUNABLE_INT_DECL("kern.ipc.nmbcnt", EXT_COUNTERS, nmbcnt);
 
 static void	m_reclaim __P((void));
 
@@ -119,7 +123,7 @@
 	/*
 	 * Setup the mb_map, allocate requested VM space.
 	 */
-	mb_map_size = nmbufs * MSIZE + nmbclusters * MCLBYTES + EXT_COUNTERS 
+	mb_map_size = nmbufs * MSIZE + nmbclusters * MCLBYTES + nmbcnt
 	    * sizeof(union mext_refcnt);
 	mb_map_size = roundup2(mb_map_size, PAGE_SIZE);
 	mb_map = kmem_suballoc(kmem_map, (vm_offset_t *)&mbutl, &maxaddr,
diff -ruN /usr/src.org/sys/sys/mbuf.h /usr/src/sys/sys/mbuf.h
--- /usr/src.org/sys/sys/mbuf.h	Sun Oct 15 00:54:55 2000
+++ /usr/src/sys/sys/mbuf.h	Sun Oct 15 01:46:34 2000
@@ -286,7 +286,7 @@
 #define MEXT_REM_REF(m) do {						\
 	KASSERT((m)->m_ext.ref_cnt->refcnt > 0, ("m_ext refcnt < 0"));	\
 	atomic_subtract_long(&((m)->m_ext.ref_cnt->refcnt), 1);		\
-	} while(0)
+} while(0)
 
 #define MEXT_ADD_REF(m) atomic_add_long(&((m)->m_ext.ref_cnt->refcnt), 1)