On Mon, Apr 07, 2014 at 04:49:35PM +0100, Mel Gorman wrote: > 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.
Fwiw, we're using bit 11 for soft-dirty tracking, so i really hope worst case never happen. (At the moment I'm trying to figure out if with this set it would be possible to clean up ugly macros in pgoff_to_pte for 2 level pages). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
