Benjamin Herrenschmidt [off-list ref] writes:

On Mon, 2015-11-23 at 15:52 +0530, Aneesh Kumar K.V wrote:

quoted

This patch series attempt to update book3s 64 linux page table format to
make it more flexible. Our current pte format is very restrictive and we
overload multiple pte bits. This is due to the non-availability of free bits
in pte_t. We use pte_t to track the validity of 4K subpages. This patch
series free up pte_t of 11 bits by moving 4K subpage tracking to the
lower half of PTE page. The pte format is updated such that we have a
better method for identifying a pte entry at pmd level. This will also enable
us to implement hugetlb migration(not yet done in this series).

Before making the changes to the pte format, I am splitting the
pte header definition such that we now have the below layout for headers

This series actually completely removes the tracking of the subages,
right ? IE, it also halves the memory footprint of page tables, doesn't
it ?

No, that is done in the next series.

http://mid.gmane.org/1448274825-30289-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com

-aneesh