Subject: Re: NKPDE changes
To: Jonathan Stone <jonathan@DSG.Stanford.EDU>
From: John S. Dyson <>
List: port-i386
Date: 11/20/1996 00:14:02
> Doesn't FreeBSD dynamically add kpde's  as necessary -- going back
> and adding the relevant entries to existing processes, if I recall
> John Dyson's message correctly?
Yep, I did.  It isn't that difficult (once you know what needs to be
done.)  The only time that we have problems now, is when our default
kernel address space gets overrun (it isn't an allocated number of
PDEs now, it is simply running out of space for them :-).)  At that
point, we are set up to reallocate the virtual size of the kernel with
changing a parameter, and then the trouble starts all over again :-).

Super-large servers with strange allocations can overrun our 256M kernel
space limitation, for example...  One can easily increase the kernel
size, to 512M, for example.  Note also, I saw that certain individuals
are having problems because of large sys5 shm regions.  Kernel VA space
is not the place for those buffers.  We have made some changes to fix
it, temporarily, until my total sysv shm rewrite to be more appropriate for
the FreeBSD VM system is done.  I really don't know if the NetBSD VM
code can accept the changes to fix the kernel VA SHM bug in the SYSV
SHM compatibility code.  (I was actually suprised that the SYSV shm
takes kernel VA space -- it simply is NOT necessary.)  (Question:
why map the SHM into the kernel, when the kernel never needs the region?)
A VM object is quite sufficient (modulo VM system bugs.)