Subject: Re: panic: ptdi %x
To: Jukka Marin <>
From: Chris G Demetriou <Chris_G_Demetriou@UX2.SP.CS.CMU.EDU>
List: current-users
Date: 03/16/1996 17:26:59
> What is this:
> Mar 16 22:11:46 mui savecore: reboot after panic: ptdi %x

Recompile your kernel with a larger value of NKPDE (defined in

NetBSD/i386 uses a compile-time-constant number of kernel page table
pages (defined by NKPDE) to map the kernel.  When it runs out, it
dies.  This typically happens on machines with lots of memory, or in
other situtations where you end up wanting to map lots of physical
memory into kernel space.  (It usually happens on machines with lots of
memory because they have lots of buffers, which need to be mapped into
the kernel.)

I call this a 'bug'.  8-)

It's worth noting that BSD/OS (from BSDI) apparently solves this
by picking the number of kernel page table pages at boot time, which
means that (assuming their formula for the amount of mapping into
kernel space you can do is correct), they shouldn't crash by running
out of kernel page table entries.

I believe FreeBSD also solves this problem, but i don't know how.
Perhaps somebody who's familiar with their code could comment.