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Date: Wed, 27 Aug 2008 12:22:38 +0200
From: Kris Kennaway <kris@FreeBSD.org>
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Cc: freebsd-hackers@freebsd.org
Subject: Re: kvm on amd64 - >6G?
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Barry Boes wrote:
> With the advent of ZFS, Solaris users are devoting 30G or more to
> their ARC caches today.  If FreeBSD 8 is going to up the KVM size, is
> there a reason to not increase the limit to something that will not be
> reached in the lifetime of 8?  100GB?

It's easily configurable on HEAD.  From an email alc sent me:

----
This:

Index: amd64/include/pmap.h
===================================================================
--- amd64/include/pmap.h        (revision 180373)
+++ amd64/include/pmap.h        (working copy)
@@ -111,7 +111,7 @@

/* Initial number of kernel page tables. */
#ifndef NKPT
-#define        NKPT            32
+#define        NKPT            1023
#endif

#define NKPML4E                1               /* number of kernel PML4 
slots */
Index: amd64/include/vmparam.h
===================================================================
--- amd64/include/vmparam.h     (revision 180373)
+++ amd64/include/vmparam.h     (working copy)
@@ -163,7 +163,7 @@
  */

#define        VM_MAX_KERNEL_ADDRESS   KVADDR(KPML4I, NPDPEPG-1, 
NPDEPG-1, NPTEPG-1)
-#define        VM_MIN_KERNEL_ADDRESS   KVADDR(KPML4I, NPDPEPG-7, 0, 0)
+#define        VM_MIN_KERNEL_ADDRESS   KVADDR(KPML4I, 0, 0, 0)

#define        DMAP_MIN_ADDRESS        KVADDR(DMPML4I, 0, 0, 0)
#define        DMAP_MAX_ADDRESS        KVADDR(DMPML4I+1, 0, 0, 0)

will now get you this:

vm.kvm_free: 547729960960
vm.kvm_size: 549755809792

on HEAD.  :-)
----

Kris