Re: RFC: A new MIPS64 ABI

[David Daney <ddaney at caviumnetworks dot com>]

On 02/14/2011 06:34 PM, Matt Thomas wrote:
> On Feb 14, 2011, at 6:26 PM, David Daney wrote:
>
> > On 02/14/2011 06:14 PM, Joe Buck wrote:
> > > On Mon, Feb 14, 2011 at 05:57:13PM -0800, Paul Koning wrote:
> > > > It seems that this proposal would benefit programs that need more than 2 GB but less than 4 GB, and for some reason really don't want 64 bit pointers.
> > > >
> > > > This seems like a microscopically small market segment.  I can't see any sense in such an effort.
> > >
> > > I remember the RHEL hugemem patch being a big deal for lots of their
> > > customers, so a process could address the full 4GB instead of only 3GB
> > > on a 32-bit machine.  If I recall correctly, upstream didn't want it
> > > (get a 64-bit machine!) but lots of paying customers clamored for it.
> > >
> > > (I personally don't have an opinion on whether it's worth bothering with).
> >
> > Also look at the new x86_64 ABI (See all those X32 psABI messages) that the Intel folks are actively working on.  This proposal is very similar to what they are doing.
>
> untrue.  N32 is closer to the X32 ABI since it is limited to 2GB.

It would only be 'untrue' if I had said it was *exactly like* the X32 thing.

Really n32 is, as you note, already quite similar to what X32 is trying 
to do.  My proposal is really for a small improvement to n32 to allow 
doubling the size of the virtual address space to 4GB.

David Daney