Large memory support in Linux

[Asaf Maruf]

Thanks...informative.

Asaf


On Jan 22, 2008 4:16 PM, Lennart Sorensen <lsorense-1wCw9BSqJbv44Nm34jS7GywD8/FfD2ys at public.gmane.org>
wrote:

> On Tue, Jan 22, 2008 at 04:06:00PM -0500, Asaf Maruf wrote:
> > Hello
> >
> > What is the maximum memory supported by the current Linux kernel? Will i
> > have to use the HUGEMEM kernel for a large memory configuration of 64G+
> or
> > 128G+.
>
> If you use x86 (i386-i686/k7/etc) then you need HIGHMEM4GB if you
> have more than 900MB, you need HIGHMEM64GB if you have more than about
> 3GB ram (basically if you have any memory mapped higher than 4GB address).
> x86 32bit can't addres more than 64GB no matter what you do.
>
> If you run amd64 (x86_64) then you don't have to worry about it.
> Maximum address range is at least 40bit on Opterons, while at least some
> Xeon's were limited to 36bit (64GB).  Not sure what the current physical
> address range on the modern Xeons is now.  I see IBM says one of their
> Xeon servers can run 512GB so that would be at least 39bit.
>
> So if the machine is 64bit capable, and can accept that much ram, then
> 32bit linux with HIGHMEM64G can use about 63GB of the ram.  64bit linux
> can use all of it with the standard config, since it doesn't have any
> settings for memory space.
>
> --
> Len Sorensen
> --
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