x32 abi support?

Alexander Larsson alexl at redhat.com
Wed May 16 20:11:56 UTC 2012

On Wed, 2012-05-16 at 21:37 +0200, drago01 wrote:
> On Wed, May 16, 2012 at 9:33 PM, Alexander Larsson <alexl at redhat.com> wrote:
> > On Wed, 2012-05-16 at 15:30 +0100, Matthew Garrett wrote:
> >> On Wed, May 16, 2012 at 04:28:31PM +0200, Lennart Poettering wrote:
> >>
> >> > Mhmm, so I was under the impression that x32 was mostly about increasing
> >> > the scalability of virtualized systems. i.e. run a higher number of
> >> > x32 containers/VM on an x86_64 host. Most server software that is run in
> >> > containers/VMs does not require 64bit address space, and hence using x32
> >> > for them should be quite benificial so that you can run more
> >> > containers/VMs per host. After all this would reduce memory and CPU
> >> > consumption of each, and due to smaller memory usage also result in less
> >> > IO?
> >>
> >> I was under the impression that it was to make Android work better on
> >> Intel. Scalable VMs are an interesting idea, but for a typical session
> >> how much RAM are we talking about?
> >
> > If you look at some contemporary VM hosting providers, like e.g.:
> > http://bloggerkhan.com/vps-hosting-vps-servers/185
> >
> > You'll see that most of them are in the 384-1024 meg of ram range, and
> > almost none are larger than 4 gigs. I'm sure most of these run 32bit
> > images, but the hosts are likely 64bit, so it seems to make quite some
> > sense to use an x32 ABI here.
> Can x32 run i686 software (multilib) ?
> Because not being able to run existing software might be a reason for
> many to want such a host.

x32 is not a kernel, so it doesn't "run software". The kernel you run is
a standard x86-64 one which can access all your physical memory, then
you have a 32bit userspace mode similar to i386-on-x86-64 but with a
different ABI that lets it use more x86-64 features while only using
32bit pointers (so each process can only use 4 gig of virtual memory).

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