diff --git a/sys/vm/swap_pager.c b/sys/vm/swap_pager.c
--- a/sys/vm/swap_pager.c
+++ b/sys/vm/swap_pager.c
@@ -729,8 +729,12 @@
 	 * estimating the number we need based on the number of pages
 	 * in the system.
 	 */
-	n = maxswzone != 0 ? maxswzone / sizeof(struct swblk) :
-	    vm_cnt.v_page_count / 2;
+	if (maxswzone > 0) {
+		n = maxswzone / sizeof(struct swblk);
+	} else {
+		n = vm_cnt.v_page_count / 2;
+		maxswzone = n * sizeof(struct swblk);
+	}
 	swpctrie_zone = uma_zcreate("swpctrie", pctrie_node_size(), NULL, NULL,
 	    pctrie_zone_init, NULL, UMA_ALIGN_PTR, 0);
 	swblk_zone = uma_zcreate("swblk", sizeof(struct swblk), NULL, NULL,
@@ -2669,21 +2673,22 @@
 }
 
 /*
- * Check that the total amount of swap currently configured does not
- * exceed half the theoretical maximum.  If it does, print a warning
- * message.
+ * Check that the total amount of swap does not exceed or approach the
+ * theoretical maximum, and print a warning if it does.
  */
 static void
 swapon_check_swzone(void)
 {
-
-	/* recommend using no more than half that amount */
-	if (swap_total > swap_maxpages / 2) {
+	if (swap_total > swap_maxpages) {
+		printf("warning: total configured swap (%lu pages) "
+		    "exceeds maximum supported amount (%lu pages).\n"
+		    "warning: increase kern.maxswzone "
+		    "or reduce amount of swap.\n",
+		    swap_total, swap_maxpages);
+	} else if (swap_total > swap_maxpages - swap_maxpages / 4) {
 		printf("warning: total configured swap (%lu pages) "
-		    "exceeds maximum recommended amount (%lu pages).\n",
-		    swap_total, swap_maxpages / 2);
-		printf("warning: increase kern.maxswzone "
-		    "or reduce amount of swap.\n");
+		    "exceeds recommended amount (%lu pages).\n",
+		    swap_total, swap_maxpages - swap_maxpages / 4);
 	}
 }