Index: sys/vm/uma_core.c
===================================================================
--- sys/vm/uma_core.c
+++ sys/vm/uma_core.c
@@ -1084,6 +1084,11 @@
 	 * Check our small startup cache to see if it has pages remaining.
 	 */
 	mtx_lock(&uma_boot_pages_mtx);
+#ifdef DIAGNOSTIC
+	if (booted < UMA_STARTUP2)
+		printf("%s from \"%s\", %d pages left\n", __func__,
+		    zone->uz_name, boot_pages);
+#endif
 	if (pages <= boot_pages) {
 		mem = bootmem;
 		boot_pages -= pages;
Index: sys/vm/uma_int.h
===================================================================
--- sys/vm/uma_int.h
+++ sys/vm/uma_int.h
@@ -134,9 +134,13 @@
 #define UMA_SLAB_MASK	(PAGE_SIZE - 1)	/* Mask to get back to the page */
 #define UMA_SLAB_SHIFT	PAGE_SHIFT	/* Number of bits PAGE_MASK */
 
-#define UMA_BOOT_PAGES		64	/* Pages allocated for startup */
-#define UMA_BOOT_PAGES_ZONES	32	/* Multiplier for pages to reserve */
-					/* if uma_zone > PAGE_SIZE */
+/*
+ * UMA Slabs, UMA Hash,
+ * 4 / 6 / 8 / 12 / 16 / 32 / 64 / 128 / 256 Bucket,
+ * vmem, vmem btag, VM OBJECT, RADIX NODE, MAP,
+ * KMAP ENTRY, MAP ENTRY, VMSPACE, fakepg
+ */
+#define UMA_BOOT_ZONES		20
 
 /* Max waste percentage before going to off page slab management */
 #define UMA_MAX_WASTE	10
Index: sys/vm/vm_page.c
===================================================================
--- sys/vm/vm_page.c
+++ sys/vm/vm_page.c
@@ -109,6 +109,7 @@
 
 #include <vm/vm.h>
 #include <vm/pmap.h>
+#include <vm/vm_map.h>
 #include <vm/vm_param.h>
 #include <vm/vm_domainset.h>
 #include <vm/vm_kern.h>
@@ -145,7 +146,7 @@
 long vm_page_array_size;
 long first_page;
 
-static int boot_pages = UMA_BOOT_PAGES;
+static int boot_pages;
 SYSCTL_INT(_vm, OID_AUTO, boot_pages, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
     &boot_pages, 0,
     "number of pages allocated for bootstrapping the VM system");
@@ -466,7 +467,7 @@
 	vm_paddr_t end, high_avail, low_avail, new_end, page_range, size;
 	vm_paddr_t biggestsize, last_pa, pa;
 	u_long pagecount;
-	int biggestone, i, pages_per_zone, segind;
+	int biggestone, i, boot_zones, sizeof_zone, segind;
 
 	biggestsize = 0;
 	biggestone = 0;
@@ -496,18 +497,50 @@
 		vm_page_domain_init(&vm_dom[i]);
 
 	/*
-	 * Almost all of the pages needed for bootstrapping UMA are used
-	 * for zone structures, so if the number of CPUs results in those
-	 * structures taking more than one page each, we set aside more pages
-	 * in proportion to the zone structure size.
+	 * Pages needed for bootstrapping UMA are mostly used for zone
+	 * structures, which have variable size dependent on number of CPUs.
+	 * The very first two zones: zone of zones and zone of kegs are
+	 * fixed sized, and together take one extra page.
 	 */
-	pages_per_zone = howmany(sizeof(struct uma_zone) +
-	    sizeof(struct uma_cache) * (mp_maxid + 1) +
-	    roundup2(sizeof(struct uma_slab), sizeof(void *)), UMA_SLAB_SIZE);
-	if (pages_per_zone > 1) {
-		/* Reserve more pages so that we don't run out. */
-		boot_pages = UMA_BOOT_PAGES_ZONES * pages_per_zone;
-	}
+	boot_zones = UMA_BOOT_ZONES;
+	sizeof_zone = sizeof(struct uma_zone) +
+	    sizeof(struct uma_cache) * (mp_maxid + 1);
+	if (sizeof_zone > UMA_SLAB_SIZE)
+		boot_pages = boot_zones *
+		    howmany(sizeof_zone, UMA_SLAB_SIZE);
+	else
+		boot_pages = howmany(boot_zones,
+		    UMA_SLAB_SIZE / sizeof_zone);
+	boot_pages += 1;
+	/*
+	 * Also, each zone has a keg, that needs to be accounted for.
+	 */
+	boot_pages += howmany(sizeof(struct uma_keg) * boot_zones,
+	    UMA_SLAB_SIZE);
+	/*
+	 * Additionally, zones may require hash structure, and we take a
+	 * conservative approach that every zone allocates hash. This may
+	 * give us several extra pages.
+	 */
+	boot_pages += howmany(sizeof(struct slabhead *) *
+	    UMA_HASH_SIZE_INIT * boot_zones, UMA_SLAB_SIZE);
+
+	/* vm_map_startup() calls uma_prealloc(). */
+	boot_pages += howmany(sizeof(struct vm_map) * MAX_KMAP, UMA_SLAB_SIZE);
+
+#ifndef	UMA_MD_SMALL_ALLOC
+	/* vmem_startup calls uma_prealloc(). */
+	boot_pages += howmany(sizeof(struct vmem_btag) * BT_MAXALLOC,
+	    UMA_SLAB_SIZE);
+#endif
+	/*
+	 * Also,
+	 * kmem_init() does one allocation from "KMAP ENTRY",
+	 * kmem_init_zero_region() does one allocation from "vmem",
+	 * kmem_init_zero_region() does one allocation from "vmem btag",
+	 * pmap_init() does one allocation from "RADIX NODE".
+	 */
+	boot_pages += 4;
 
 	/*
 	 * Allocate memory for use when boot strapping the kernel memory