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

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Message-ID: <20121019091016.GA4582@mudshark.cambridge.arm.com>
Date:	Fri, 19 Oct 2012 10:10:16 +0100
From:	Will Deacon <will.deacon@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	David Miller <davem@...emloft.net>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"mhocko@...e.cz" <mhocko@...e.cz>,
	"kirill@...temov.name" <kirill@...temov.name>,
	"aarcange@...hat.com" <aarcange@...hat.com>,
	"cmetcalf@...era.com" <cmetcalf@...era.com>,
	Steve Capper <Steve.Capper@....com>
Subject: Re: [PATCH v2] mm: thp: Set the accessed flag for old pages on
 access fault.

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@....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

Cheers,

Will
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