On Wed, Jun 01, 2011 at 09:15:29PM +0200, Andrea Arcangeli wrote: > On Wed, Jun 01, 2011 at 06:58:09PM +0100, Mel Gorman wrote: > > Umm, HIGHMEM4G implies a two-level pagetable layout so where are > > things like _PAGE_BIT_SPLITTING being set when THP is enabled? > > They should be set on the pgd, pud_offset/pgd_offset will just bypass. > The splitting bit shouldn't be special about it, the present bit > should work the same. This comment is misleading at best then. #define _PAGE_BIT_SPLITTING _PAGE_BIT_UNUSED1 /* only valid on a PSE pmd */ At the PGD level, it can have PSE set obviously but it's not a PMD. I confess I haven't checked the manual to see if it's safe to use _PAGE_BIT_UNUSED1 like this so am taking your word for it. I found that the bug is far harder to reproduce with 3 pagetable levels than with 2 but that is just timing. So far it has proven impossible on x86-64 at least within 27 hours so that has me looking at how pagetable management between x86 and x86-64 differ. Barriers are a big different between how 32-bit !SMP and X86-64 but don't know yet which one is relevant or if this is even the right direction. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>