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From: Daniel Freedman <freedman@ccmr.cornell.edu>
Date: Sun, 6 Jan 2002 14:45:25 -0500
To: Marvin Justice <mjustice@austin.rr.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: i686 SMP systems with more then 12 GB ram with 2.4.x kernel ?
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Hi Marvin,

Thanks for the quick reply.


On Sun, Jan 06, 2002, Marvin Justice wrote:
> Is this what your looking for? Just below the definition of PAGE_OFFSET in 
> page.h:
> 
> /*
>  * This much address space is reserved for vmalloc() and iomap()
>  * as well as fixmap mappings.
>  */
> #define __VMALLOC_RESERVE	(128 << 20)

However, while it does seem to be exactly the definition for 128MB
vmalloc offset that I was looking for, I don't seem to have this
definition in my source tree (2.4.16):

  freedman@planck:/usr/src/linux$ grep -r __VMALLOC_RESERVE *
  freedman@planck:/usr/src/linux$ 

Any idea why this is so?

Thanks again,

Daniel

> On Sunday 06 January 2002 12:39 pm, Daniel Freedman wrote:
> > On Jan 01 2002, H. Peter Anvin (hpa@zytor.com) wrote:
> > > By author: Alan Cox <alan@lxorguk.ukuu.org.uk>
> > >
> > > > > 2. Isn't the boundary at 2^30 really irrelevant and the three
> > > > > "correct" zones are (0 - 2^24-1), (2^24 - 2^32-1) and (2^32 -
> > > > > 2^36-1)?
> > > >
> > > > Nope. The limit for directly mapped memory is 2^30.
> > >
> > > 2^30-2^27 to be exact (assuming a 3:1 split and 128MB vmalloc zone.)
> > >
> > >         -hpa
> >
> > For my better understanding, where's the 128MB vmalloc zone assumption
> > defined, please?
> >
> > I'm pretty sure I understand that the 3:1 split you refer to is
> > defined by PAGE_OFFSET in asm-i386/page.h
> >
> > But when I tried to find the answer in the source for the vmalloc
> > zone, I looked in linux/mm.h, linux/mmzone.h, linux/vmalloc.h, and
> > mm/vmalloc.c, but couldn't find anything there or in O'Reilly's kernel
> > book that I could follow/understand.
> >
> > Thanks for any pointers.
> >
> > Take care,
> >
> > Daniel

-- 
Daniel A. Freedman
Laboratory for Atomic and Solid State Physics
Department of Physics
Cornell University
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