On Thu, Oct 25, 2012 at 05:44:31PM +0100, Will Deacon wrote: > On x86 memory accesses to pages without the ACCESSED flag set result in the > ACCESSED flag being set automatically. With the ARM architecture a page access > fault is raised instead (and it will continue to be raised until the ACCESSED > flag is set for the appropriate PTE/PMD). > > For normal memory pages, handle_pte_fault will call pte_mkyoung (effectively > setting the ACCESSED flag). For transparent huge pages, pmd_mkyoung will only > be called for a write fault. > > This patch ensures that faults on transparent hugepages which do not result > in a CoW update the access flags for the faulting pmd. > > Cc: Chris Metcalf <cmetcalf@xxxxxxxxxx> > Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> > Signed-off-by: Will Deacon <will.deacon@xxxxxxx> > --- > > Ok chaps, I rebased this thing onto today's next (which basically > necessitated a rewrite) so I've reluctantly dropped my acks and kindly > ask if you could eyeball the new code, especially where the locking is > concerned. In the numa code (do_huge_pmd_prot_none), Peter checks again > that the page is not splitting, but I can't see why that is required. In handle_mm_fault() we check if the pmd is under splitting without page_table_lock. It's kind of speculative cheap check. We need to re-check if the PMD is really not under splitting after taking page_table_lock. See section "Locking in hugepage aware code" in Documentation/vm/transhuge.txt -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
