diff --git a/sys/vm/memguard.c b/sys/vm/memguard.c
index 5d483b19a50..d4efc2b7123 100644
--- a/sys/vm/memguard.c
+++ b/sys/vm/memguard.c
@@ -69,7 +69,7 @@ static SYSCTL_NODE(_vm, OID_AUTO, memguard, CTLFLAG_RW, NULL, "MemGuard data");
 static u_int vm_memguard_divisor;
 SYSCTL_UINT(_vm_memguard, OID_AUTO, divisor, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
     &vm_memguard_divisor,
-    0, "(kmem_size/memguard_divisor) == memguard submap size");     
+    0, "(kmem_size/memguard_divisor) == memguard submap size");
 
 /*
  * Short description (ks_shortdesc) of memory type to monitor.
@@ -162,6 +162,7 @@ memguard_fudge(unsigned long km_size, const struct vm_map *parent_map)
 	u_long mem_pgs, parent_size;
 
 	vm_memguard_divisor = 10;
+	/* CTFLAG_RDTUN doesn't work during the early boot process. */
 	TUNABLE_INT_FETCH("vm.memguard.divisor", &vm_memguard_divisor);
 
 	parent_size = vm_map_max(parent_map) - vm_map_min(parent_map) +
diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
index a764788f2b9..64ca13075c6 100644
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -349,6 +349,9 @@ vm_page_startup(vm_offset_t vaddr)
 	/*
 	 * Allocate memory for use when boot strapping the kernel memory
 	 * allocator.
+	 *
+	 * CTFLAG_RDTUN doesn't work during the early boot process, so we must
+	 * manually fetch the value.
 	 */
 	TUNABLE_INT_FETCH("vm.boot_pages", &boot_pages);
 	new_end = end - (boot_pages * UMA_SLAB_SIZE);