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. > Archive: http://mail.nl.linux.org/kernelnewbies/ > FAQ: http://kernelnewbies.org/faq/ > -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
