Re: [Xen-users] 32bit vs 64bit memory usage question

["Jamie Burns" <fantasticjamieburns@xxxxxxxxxxx>]

Thanks for your insight.

But nothing else in my Debian install uses up double memory.

Only XEN.

Why only XEN?

----- Original Message ----- 
From: "Ulrich Windl" <ulrich.windl@xxxxxxxxxxxxxxxxxxxx>
To: <xen-users@xxxxxxxxxxxxxxxxxxx>
Sent: Monday, February 05, 2007 3:28 PM
Subject: Re: [Xen-users] 32bit vs 64bit memory usage question


> On 5 Feb 2007 at 10:00, Tom Miller wrote:
>
> [...]
> > 64 bit pointers and 64 bit memory address slots are twice as big as
> > corresponding 32 bit ones.   So unless you have 4 GB of memory or more,
> > using 64bit software is actually slower for the system, not faster.
> Are you sure? You are not saying that 64-bit programs are twice as large 
> as 32-bit
> programs, do you? Besides of that I'd expect a 64-bit CPU to load a 64 bit 
> word
> from memory in the same speed as a 32-bit CPU would load a 32-bit word. 
> Also these
> AMD/Intel CPUs seem to have additional registers in 64bit mode.
>
> I think the memory overhead comes from (As Andrew S Tanenbaum explained in 
> one of
> his books about 10 years ago) the fact that the tables to manage the huge 
> 64 bit
> virtual address space are a great deal larger than those for 32-bit.
>
> Finally (as in HP-UX 11), a 64 bit OS does not mean that every program is 
> a 64-bit
> executable: a 32-bit Shell, Perl and Emacs is sufficient for most users 
> I'd think
> ;-)
>
> Regards,
> Ulrich
>
>
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users
>
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