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SubjectRe: [PATCH 17/50] mm: Do not flush TLB during protection change if !pte_present && !migration_entry
On Mon, Sep 16, 2013 at 06:35:47PM +0200, Peter Zijlstra wrote:
> On Tue, Sep 10, 2013 at 10:31:57AM +0100, Mel Gorman wrote:
> > NUMA PTE scanning is expensive both in terms of the scanning itself and
> > the TLB flush if there are any updates. Currently non-present PTEs are
> > accounted for as an update and incurring a TLB flush where it is only
> > necessary for anonymous migration entries. This patch addresses the
> > problem and should reduce TLB flushes.
> >
> > Signed-off-by: Mel Gorman <mgorman@suse.de>
> > ---
> > mm/mprotect.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/mprotect.c b/mm/mprotect.c
> > index 1f9b54b..1e9cef0 100644
> > --- a/mm/mprotect.c
> > +++ b/mm/mprotect.c
> > @@ -109,8 +109,9 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
> > make_migration_entry_read(&entry);
> > set_pte_at(mm, addr, pte,
> > swp_entry_to_pte(entry));
> > +
> > + pages++;
> > }
> > - pages++;
> > }
> > } while (pte++, addr += PAGE_SIZE, addr != end);
> > arch_leave_lazy_mmu_mode();
>
> Should we fold this into patch 7 ?

Looking closer at it, I think folding it into the patch would overload
the purpose of patch 7 a little too much but I shuffled the series to
keep the patches together.

--
Mel Gorman
SUSE Labs


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