Subject: Re: [vserver] 32bit Guests on 64bit Host
From: Herbert Poetzl <herbert@13thfloor.at>
Date: Sun, 20 Dec 2009 14:56:40 +0100

On Sun, Dec 20, 2009 at 01:25:04PM +0100, Oliver Welter wrote:
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> Hi All,

> anybody can tell me, if there are drawbacks/issues, running 32bit
> systems on top of a 64bit host?

there should be none as long as the personality is set
properly and you have the 32bit compatibility enabled

> I am currently running debian etch with a self compiled
> 2.6.22-vs2.2.0.7 x86_64 on a 64bit Dual Athlon with 16GB of RAM.
> At the moment I have 64bit guests (gentoo) running on it but 
> for some reasons* I am overthinking to downgrade the guests to 
> 32bit.

> Main question is, whats about the 4GB Memory issue?
> I assume each guest can address only 4GB of memory but will the 
> guest spread the 4 Gigs across the available address space?

no, but it will be spread over the physical memory :)

> *Reason: First, I have still several 32bit host nodes so it would 
> be simpler for me to maintain my guest images. Second: It seems 
> that especially php is eating memory on 64bit systems without 
> any earnings.

usually 64bit code is more efficient on 64bit systems
than 32bit code, and often the larger address space
brings an advantage too ... of course, YMMV

best,
Herbert

> best regards

> Oliver

> - --
> Protect your environment -  close windows and adopt a penguin!
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