commit 3e51258346684f993b0a316547b2484249ac4c93
Author: Andriy Gapon <avg@icyb.net.ua>
Date:   Wed Dec 26 12:15:54 2012 +0200

    [wip] auto-tune NKPT on amd64 if compile-time value is not sufficient
    
    To do:	fix minidump code

diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index 8e06ff9..bddacc6 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -492,16 +492,25 @@ allocpages(vm_paddr_t *firstaddr, int n)
 
 CTASSERT(powerof2(NDMPML4E));
 
+static u_int nkpt = NKPT;
+static u_int nkpdpe = NKPDPE;
+
 static void
 create_pagetables(vm_paddr_t *firstaddr)
 {
 	int i, j, ndm1g;
 
+	if (*firstaddr + NBPDR > NKPT * NBPDR) {
+		nkpt = howmany((uintptr_t)*firstaddr, NBPDR) + 1;
+		nkpdpe = howmany(nkpt, NPDEPG);
+		printf("increased NKPT from %u to %u\n", NKPT, nkpt);
+	}
+
 	/* Allocate pages */
-	KPTphys = allocpages(firstaddr, NKPT);
+	KPTphys = allocpages(firstaddr, nkpt);
 	KPML4phys = allocpages(firstaddr, 1);
 	KPDPphys = allocpages(firstaddr, NKPML4E);
-	KPDphys = allocpages(firstaddr, NKPDPE);
+	KPDphys = allocpages(firstaddr, nkpdpe);
 
 	ndmpdp = (ptoa(Maxmem) + NBPDP - 1) >> PDPSHIFT;
 	if (ndmpdp < 4)		/* Minimum 4GB of dirmap */
@@ -523,7 +532,7 @@ create_pagetables(vm_paddr_t *firstaddr)
 	}
 
 	/* Now map the page tables at their location within PTmap */
-	for (i = 0; i < NKPT; i++) {
+	for (i = 0; i < nkpt; i++) {
 		((pd_entry_t *)KPDphys)[i] = KPTphys + (i << PAGE_SHIFT);
 		((pd_entry_t *)KPDphys)[i] |= PG_RW | PG_V;
 	}
@@ -536,7 +545,7 @@ create_pagetables(vm_paddr_t *firstaddr)
 	}
 
 	/* And connect up the PD to the PDP */
-	for (i = 0; i < NKPDPE; i++) {
+	for (i = 0; i < nkpdpe; i++) {
 		((pdp_entry_t *)KPDPphys)[i + KPDPI] = KPDphys +
 		    (i << PAGE_SHIFT);
 		((pdp_entry_t *)KPDPphys)[i + KPDPI] |= PG_RW | PG_V | PG_U;
@@ -765,7 +774,7 @@ pmap_init(void)
 	 * Initialize the vm page array entries for the kernel pmap's
 	 * page table pages.
 	 */ 
-	for (i = 0; i < NKPT; i++) {
+	for (i = 0; i < nkpt; i++) {
 		mpte = PHYS_TO_VM_PAGE(KPTphys + (i << PAGE_SHIFT));
 		KASSERT(mpte >= vm_page_array &&
 		    mpte < &vm_page_array[vm_page_array_size],
@@ -1983,7 +1992,7 @@ pmap_growkernel(vm_offset_t addr)
 	 * any new kernel page table pages between "kernel_vm_end" and
 	 * "KERNBASE".
 	 */
-	if (KERNBASE < addr && addr <= KERNBASE + NKPT * NBPDR)
+	if (KERNBASE < addr && addr <= KERNBASE + nkpt * NBPDR)
 		return;
 
 	addr = roundup2(addr, NBPDR);