Index: sys/powerpc/aim/mmu_oea64.c
===================================================================
--- sys/powerpc/aim/mmu_oea64.c
+++ sys/powerpc/aim/mmu_oea64.c
@@ -184,10 +184,12 @@
 
 static struct	pvo_entry *moea64_bpvo_pool;
 static int	moea64_bpvo_pool_index = 0;
-static int	moea64_bpvo_pool_size = 327680;
+static int	moea64_bpvo_pool_size = 0;
 SYSCTL_INT(_machdep, OID_AUTO, moea64_allocated_bpvo_entries, CTLFLAG_RD, 
     &moea64_bpvo_pool_index, 0, "");
 
+#define	BPVO_POOL_SIZE	327680 /* Sensible historical default value */
+#define	BPVO_POOL_EXPANSION_FACTOR	3
 #define	VSID_NBPW	(sizeof(u_int32_t) * 8)
 #ifdef __powerpc64__
 #define	NVSIDS		(NPMAPS * 16)
@@ -916,6 +918,14 @@
 	 * Initialise the bootstrap pvo pool.
 	 */
 	TUNABLE_INT_FETCH("machdep.moea64_bpvo_pool_size", &moea64_bpvo_pool_size);
+	if (moea64_bpvo_pool_size == 0) {
+		if (!hw_direct_map)
+			moea64_bpvo_pool_size = ((ptoa((uintmax_t)physmem) * sizeof(struct vm_page)) /
+			    (PAGE_SIZE * PAGE_SIZE)) * BPVO_POOL_EXPANSION_FACTOR;
+		else
+			moea64_bpvo_pool_size = BPVO_POOL_SIZE;
+	}
+
 	moea64_bpvo_pool = (struct pvo_entry *)moea64_bootstrap_alloc(
 		moea64_bpvo_pool_size*sizeof(struct pvo_entry), PAGE_SIZE);
 	moea64_bpvo_pool_index = 0;