[Vm-dev] 64 bit VM, source anyone?

[Philippe Marschall]

2007/12/5, goran at krampe.se <goran at krampe.se>:
>
> Hi!
>
> "Michael van der Gulik" <mikevdg at gmail.com> wrote:
> > On Dec 5, 2007 10:23 AM, <goran at krampe.se> wrote:
> > > PS. The reason I said "slowish" is that... well, it is definitely not
> > > much faster than my Pentium-M laptop. But after talking on IRC it became
> > > clear that those numbers may very well be the expected.
> >
> > Why would a 64-bit VM be slower?
> >
> > Would it be because it's moving twice as much memory around, or because it's
> > fiddling with 32-bit pointers using 64-bit registers?
> >
> > Gulik.
>
> Ok, some clarifications:
>
> 1. My numbers were for the 32-bit binary VM, not a 64 bit VM.
>
> 2. There are reasons going both ways regarding speed. On the AMD64
> architecture (see some details here: http://www.debian.org/ports/amd64)
> there is potential for higher speed through better abilities for the
> compiler BUT... there are also things slowing it down (8 bytes instead
> of 4 in lots of situations). Also, I don't know how/if the gnuifier is
> affected by this (perhaps not).
>
> As Phillipe's post suggests - the 32 bit VM is actually a tad faster on
> his box. It might be interesting to know if he has toyed with
> optimization flags.

Nah, he was happy that it worked.

Cheers
Philippe