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

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 22 Oct 2012 11:35:03 +0100
Will Deacon <will.deacon@arm.com> wrote:

> On Fri, Oct 19, 2012 at 07:49:55PM +0100, Andrew Morton wrote:
> > On Fri, 19 Oct 2012 10:10:16 +0100
> > Will Deacon <will.deacon@arm.com> 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@arm.com> 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!
> 
> Eek, that certainly wasn't intentional and it's compiling fine for me on
> -rc1 and -rc2 for both ARM (no THP) and x86 (with and without THP).
> 
> Please can you send the build failure?
> 
> > 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.
> 
> Happy to sort it out once I work out what's going wrong!

The patch "ARM: mm: Transparent huge page support for LPAE systems" is
not present in linux-next, so this patch ("mm: thp: Set the accessed
flag for old pages on access fault") will not compile?