using segmentation to manage memory in FreeBSD

[John Baldwin]

On Tuesday 08 March 2005 11:20 am, Kamal R. Prasad wrote:
> --- John Baldwin <jhb at FreeBSD.org> wrote:
> > On Tuesday 08 March 2005 09:05 am, Ravi Krishna
> >
> > wrote:
> > > Hi all!
>
> [snip]
>
> > Segments just provide a base + offset into the
> > virtual address space that is
> > backed by the TLB mappings, so to make this
> > practically useful would be a lot
> > more work than would first appear because your
> > segments have to map virtually
> > contiguous memory.
>
> If I had a processor with no MMU, but only memory
> protection and a segment register, can I port freebsd
> onto that architecture? I mean, use the segment
> register to provide for non-conflicting process
> spaces.

Well, it is theoretically possible, yes, but practically speaking I'd think it 
would be a lot of work.  The entire vm system assumes paging.  If you had a 
way of emulating some rather large pages using segmentation then perhaps you 
could do that.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org