Re: [PATCH v2] mm: thp: Set the accessed flag for old pages onaccess fault.

From: Andrew Morton
Date: Fri Oct 19 2012 - 14:49:47 EST


On Fri, 19 Oct 2012 10:10:16 +0100
Will Deacon <will.deacon@xxxxxxx> wrote:

> On Thu, Oct 18, 2012 at 11:05:02PM +0100, Andrew Morton wrote:
> > On Wed, 17 Oct 2012 16:54:02 +0100
> > Will Deacon <will.deacon@xxxxxxx> 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.
> >
> > Confused. Where is the arm implementation of update_mmu_cache_pmd()?
>
> Right at the end of this patch, which was posted to the ARM list yesterday:
>
> http://lists.infradead.org/pipermail/linux-arm-kernel/2012-October/126387.html

I received and then merged a patch which won't compile!

Ho hum. I'll drop
mm-thp-set-the-accessed-flag-for-old-pages-on-access-fault.patch and
shall assume that you'll sort things out at the appropriate time.

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