Linux kernel 's page table's entry use large page
size to make use of TLB. when physical memory less
than 4G. page size is 4MB,when larger than 4G(PAE
mode) ,page size is 2MB.
--- Amit Singh <amitsingh_blr@xxxxxxxxxxx> wrote:
> Hi
>
> googling on this didnt give me any useful links.
> Wld
> appreciate if someone throws some light on this.
>
> section 2.5.5.2 in Bover and Cesati - UTLK ,
> talks
> about the final kernel page table, with different
> sizes of physical RAM.
> case a), less than 896 MB, there the code for this
> is ...
>
> address = 0xc0000000;
> while (address < end) {
> pe = ....;
> set_pgd(pgd, __pgd(pe));
> ++pe;
> address += 0x400000;
> }
>
> here it is said that, address+=0x400000 line
> appears because the page size is 4MB.
> Similarly for the > 4GB case theres a
> corresponding
> line address+=)x200000(this time for page middle
> directory entry.
>
> Qestion : (taking case 1)Is this line there
> because
> the page size is 4MB or because, a page table
> dreictory entry points to a page table( 2 level
> paging), 10 bits are devoted to the page table(hence
> each table has 1024 entries), and the
> offset(assuming
> it to be 12 bits) makes PAGE_SIZE to be 4KB, hence
> one
> page directory entry points to )xc0000000, and the
> next points to an address 2^22= 4MB away.
> Similarly in the second case, the page size is
> not necessarily 2 MB, instead if it is 4KB, and page
> table has 512 entries(2^9), says that the next entry
> in pmd, shld point to a location , 2^21 = 2 MB away.
>
> regards
> Amit
>
>
>
> __________________________________
> Do you Yahoo!?
> Read only the mail you want - Yahoo! Mail SpamGuard.
>
> http://promotions.yahoo.com/new_mail
>
> --
> Kernelnewbies: Help each other learn about the Linux
> kernel.
> Archive:
> http://mail.nl.linux.org/kernelnewbies/
> FAQ: http://kernelnewbies.org/faq/
>
>
__________________________________
Do you Yahoo!?
Plan great trips with Yahoo! Travel: Now over 17,000 guides!
http://travel.yahoo.com/p-travelguide
--
Kernelnewbies: Help each other learn about the Linux kernel.
Archive: http://mail.nl.linux.org/kernelnewbies/
FAQ: http://kernelnewbies.org/faq/
