Re: Demand paging

["Kedar Sovani" <kedar@calsoftinc.com>]

Yes, the x86 processor also has present / absent flags for the page
table/directory entries as well. So that they are allocate only when
required, otherwise those are empty.

That seems to be logical as well. The book by Turley gives you a good
insight into the x86 architecture, where you can look into the details.

rgds,
Kedar


Kedar S. Sovani
Calsoft Pvt. Ltd.
Pune.
----- Original Message -----
From: "Brad Lyon" <bradlyon@ntown.com>
To: <kernelnewbies@nl.linux.org>
Cc: <kernelnewbies@nl.linux.org>
Sent: Tuesday, October 01, 2002 7:46 PM
Subject: Re: Demand paging


>
> >
> >I think this combines with the ldt (local descriptor table). In this
> >table, you specify how long will be the memory segment for data, code
> >and stack. You could start a process with a virtual space of 1 or 2
> >MBytes by writing the appropiate values into his ldt and based on
this,
> >you would only need one page table (one page table takes 4Kb for
> >addressing 4MBytes).
> >
> >Is this correct?
>
>
> I don't think so.  This was driving me crazy recently, too.  I haven't
> tracked down all of the specific parts in the code, but I believe it
> creates page tables, and maybe page directory entries, too,  only as
they
> are actually requested.  The present/not present is probably used only
when
> the page has been (demand) loaded, then swapped back out.  More
details,
> anyone?
>
> Thanks for asking this, Pere, I'm in the middle of trying to
understand
> this, too.
>
> --
> Kernelnewbies: Help each other learn about the Linux kernel.
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