Date: Tue, 16 Dec 2008 17:44:43 +0100
From: Andi Kleen <andi@firstfloor.org>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Martin Steigerwald <ms@teamix.de>, linux-kernel@vger.kernel.org,
       Andi Kleen <andi@firstfloor.org>, Ingo Molnar <mingo@elte.hu>
Subject: Re: physical memory limit of 64-bit linux
Message-ID: <20081216164443.GY25779@one.firstfloor.org>
References: <200812161556.25518.ms@teamix.de> <200812161654.17291.rjw@sisk.pl>
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On Tue, Dec 16, 2008 at 04:54:16PM +0100, Rafael J. Wysocki wrote:
> On Tuesday, 16 of December 2008, Martin Steigerwald wrote:
> > 
> > Hi!
> > 
> > What is the physical memory limit for 64-bit Linux? I read about 40 bit 
> > address bus for AMD Athlon X2 (1 TB) and 48 bit for Barcelona X4 (256 TB).
> > 
> > Is 64-bit linux able to use that amount - provided that one would manage to 
> > build it into a machine? Or does it have a lower limit?

It depends on which 64bit Linux; e.g. IA64 has larger limits.

> > Looking into the Google crystal ball gives unclear pictures... I tend to 
> > assume that Linux would handle it, but I am not sure.
> 
> IIRC, the current maximal virtual memory space size of the kernel on x86_64 is 2^46.

Correct.

-Andi

-- 
ak@linux.intel.com
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