Why is default value of NKPT so small? mfsroot

[John Baldwin]

On Friday 06 November 2009 2:19:51 pm Trever wrote:
> Does anyone know what the thinking is behind the default value of NKTP in /usr/src/sys/i386/include/pmap.h?
> 
> It seems to me that it's too small, though I'm wondering if there are some considerations in changing it's value that I should know about.
> 
> Too small because: making it a little more than twice as large (so you can get about a 300MB mfsroot to boot) means you can (by default) boot a standard FreeBSD system into memory, and I know I can't be the only one who would value that a great deal for many reasons.  As it stands you have to ax things out (like depenguinator does, for example).  Or you have to recompile the kernel.  
> 
> Does it have to be like this?
> 
> Which leads me to two more questions:
> - is it possible to change the NKTP value without recompiling the kernel?  I think there isn't but I'll ask.
> - is it possible to change the NKTP value without editing pmap.h (can I pass a variable into the kernel build process)?

I keep meaning to make NKPT a kernel option for i386.  Try this patch, it
should let you add 'options NKPT=xxx' to your kernel config.

Index: conf/options.i386
===================================================================
--- conf/options.i386	(revision 198997)
+++ conf/options.i386	(working copy)
@@ -12,6 +12,7 @@
 MAXMEM
 MPTABLE_FORCE_HTT
 MP_WATCHDOG
+NKPT			opt_pmap.h
 PERFMON
 PMAP_SHPGPERPROC	opt_pmap.h
 POWERFAIL_NMI		opt_trap.h
Index: i386/i386/mp_machdep.c
===================================================================
--- i386/i386/mp_machdep.c	(revision 198997)
+++ i386/i386/mp_machdep.c	(working copy)
@@ -30,6 +30,7 @@
 #include "opt_cpu.h"
 #include "opt_kstack_pages.h"
 #include "opt_mp_watchdog.h"
+#include "opt_pmap.h"
 #include "opt_sched.h"
 #include "opt_smp.h"
 
Index: i386/xen/mp_machdep.c
===================================================================
--- i386/xen/mp_machdep.c	(revision 198997)
+++ i386/xen/mp_machdep.c	(working copy)
@@ -31,6 +31,7 @@
 #include "opt_cpu.h"
 #include "opt_kstack_pages.h"
 #include "opt_mp_watchdog.h"
+#include "opt_pmap.h"
 #include "opt_sched.h"
 #include "opt_smp.h"
 

-- 
John Baldwin