Re: [Patch] mm/ksm.c is doing an unneeded _notify in write_protect_page.

[Andrea Arcangeli <aarcange@redhat.com>]

On Thu, Mar 11, 2010 at 06:01:59PM +0200, Izik Eidus wrote:
> On Thu, 11 Mar 2010 09:54:22 -0600
> Robin Holt <holt@sgi.com> wrote:
> 
> > 
> > ksm.c's write_protect_page implements a lockless means of verifying a
> > page does not have any users of the page which are not accounted for via
> > other kernel tracking means.  It does this by removing the writable pte
> > with TLB flushes, checking the page_count against the total known users,
> > and then using set_pte_at_notify to make it a read-only entry.
> > 
> > An unneeded mmu_notifier callout is made in the case where the known
> > users does not match the page_count.  In that event, we are inserting
> > the identical pte and there is no need for the set_pte_at_notify, but
> > rather the simpler set_pte_at suffices.
> > 
> > Signed-off-by: Robin Holt <holt@sgi.com>
> > To: Izik Eidus <ieidus@redhat.com>
> > Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
> > Cc: Chris Wright <chrisw@redhat.com>
> > Cc: linux-mm@kvack.org
> 
> Acked-by: Izik Eidus <ieidus@redhat.com>

Ack too. I misunderstood what you were talking about before, patch
makes it clear now ;).

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