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Date: Thu, 25 Oct 2012 15:51:10 -0400 From: Johannes Weiner <hannes@...xchg.org> To: Will Deacon <will.deacon@....com> Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, mhocko@...e.cz, peterz@...radead.org, akpm@...ux-foundation.org, Chris Metcalf <cmetcalf@...era.com>, "Kirill A. Shutemov" <kirill@...temov.name>, Andrea Arcangeli <aarcange@...hat.com> Subject: Re: [PATCH v3] mm: thp: Set the accessed flag for old pages on access fault. 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@...era.com> > Cc: Kirill A. Shutemov <kirill@...temov.name> > Cc: Andrea Arcangeli <aarcange@...hat.com> > Signed-off-by: Will Deacon <will.deacon@....com> Acked-by: Johannes Weiner <hannes@...xchg.org> > 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. I don't either. If the thing was splitting when the fault happened, that path is not taken. And the locked pmd_same() check should rule out splitting setting in after testing pmd_trans_huge_splitting(). Peter? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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