Hi Don, On Thu, Jun 28, 2012 at 08:13:11AM -0700, Don Morris wrote: > On 06/28/2012 05:55 AM, Andrea Arcangeli wrote: > > We will set these bitflags only when the pmd and pte is non present. > > > > Just a couple grammar nitpicks. > > > They work like PROT_NONE but they identify a request for the numa > > hinting page fault to trigger. > > > > Because we want to be able to set these bitflag in any established pte > > these bitflags > > > or pmd (while clearing the present bit at the same time) without > > losing information, these bitflags must never be set when the pte and > > pmd are present. > > > > For _PAGE_NUMA_PTE the pte bitflag used is _PAGE_PSE, which cannot be > > set on ptes and it also fits in between _PAGE_FILE and _PAGE_PROTNONE > > which avoids having to alter the swp entries format. > > > > For _PAGE_NUMA_PMD, we use a reserved bitflag. pmds never contain > > swap_entries but if in the future we'll swap transparent hugepages, we > > must keep in mind not to use the _PAGE_UNUSED2 bitflag in the swap > > entry format and to start the swap entry offset above it. > > > > PAGE_UNUSED2 is used by Xen but only on ptes established by ioremap, > > but it's never used on pmds so there's no risk of collision with Xen. > > Maybe "but only on ptes established by ioremap, never on pmds so > there's no risk of collision with Xen." ? The extra "but" just > doesn't flow in the original. Agreed and applied, thanks! Andrea -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>