On Mon, Apr 07, 2014 at 04:32:39PM +0100, David Vrabel wrote: > On 07/04/14 16:10, Mel Gorman wrote: > > _PAGE_NUMA is currently an alias of _PROT_PROTNONE to trap NUMA hinting > > faults. As the bit is shared care is taken that _PAGE_NUMA is only used in > > places where _PAGE_PROTNONE could not reach but this still causes problems > > on Xen and conceptually difficult. > > The problem with Xen guests occurred because mprotect() /was/ confusing > PROTNONE mappings with _PAGE_NUMA and clearing the non-existant NUMA hints. > I didn't bother spelling it out in case I gave the impression that I was blaming Xen for the problem. As the bit is now changes, does it help the Xen problem or cause another collision of some sort? There is no guarantee _PAGE_NUMA will remain as bit 62 but at worst it'll use bit 11 and NUMA_BALANCING will depend in !KMEMCHECK. -- Mel Gorman SUSE Labs -- 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>