Mapping of ZONE_HIGHMEM in kernel address space in 32bit x86

[Paul Davies C]

It is an arbitrary question that popped in my mind. However, I came to know
that the constraints I stated in the previous mail is only restricted to
x86 only.Now besides my first questions , I have one more question, Why x86
only?


On Tue, May 14, 2013 at 2:34 AM, Sergio Andrés Gómez del Real <
sergio.g.delreal at gmail.com> wrote:

> Sure, I forgot what you said; precisely the mechanism allows to use
> lots of linear space without necessarily allocating physical memory
> (demand paging and the like).
> What about the rest of what I said? Is it correct or is there
> something wrong about it?
> Thanks.
>
> On 5/13/13, Valdis.Kletnieks at vt.edu <Valdis.Kletnieks at vt.edu> wrote:
> > On Mon, 13 May 2013 14:11:22 -0500, Sergio Andr said:
> >
> >> 2. When user applications allocates memory, the kernel must allocate
> >> virtual memory and physical memory, right?
> >
> > Wrong. If userspace allocates (say) 15M of memory, the kernel has every
> > right
> > to overcommit and not actually allocate either physical memory or backing
> > page
> > space for all 15M.  It instead maps it as a non-existent virtual address,
> > and
> > if/when the application actually touches the page, it generates a page
> > fault,
> > and *then* the kernel does the allocating of physical memory and maybe
> swap
> > space.
> >
> >
>



-- 
*Regards,*
*Paul Davies C*
vivafoss.blogspot.com
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