Re: [Vserver] ia32 Vserver guests accessing >4GB of memory on an amd_64 Vserver host?

From: Herbert Poetzl <>
Date: Wed 26 Jul 2006 - 14:59:11 BST
Message-ID: <>

On Tue, Jul 18, 2006 at 12:41:29AM -0700, EKC wrote:
> I have linux-vserver installed on a 2.6.17 debian amd_64 system. I
> have used debootstrap to create ia32 vserver guests on the amd_64
> host. So far, the ia32 guests seem to run just fine. I understand that
> each ia32 vserver cannot access more than 4gb of memory. However,
> can multiple ia32 vservers cumulatively use more than 4gb of RAM on
> a 64-bit system? I don't mind if each vserver is confined to 4gb of
> addressable memory. However, I don't want all of the vservers confined
> to the same 4gb address space when 16gb of memory is available on the
> server.

well, the 4GB is the so called 'virtual' address space
which is limited to 32bit (on ia32), which is shared
between userspace (normally 3GB) and kernel space (1GB).
as the name implies, it is virtual, and has no relation
to the physical memory addresses, so, unless the ia32
emulation does something terribly wrong, it should use
the whole physical memory for several guests ...

disclaimer: I haven't got around testing this on a
real 64bit environment ...

> So, if I install 16gb of memory in a 64-bit vserver host, can several
> 32-bit vserver guests together use more than 4gb of RAM? Or, do I have
> to run 64-bit guests?

of course, 64bit guests will get an additional boost
because many things are simply faster when done with
64bit registers instead of 32bit ones ...


> Thanks in advance
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Received on Wed Jul 26 15:11:17 2006

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