Re: [PATCH RFC 2/3] proc/smaps: show amount of nonlinear ptes invma

[Konstantin Khlebnikov]

KOSAKI Motohiro wrote:
> On Mon, Apr 30, 2012 at 7:29 AM, Konstantin Khlebnikov
> <khlebnikov@xxxxxxxxxx>  wrote:
> > Currently, nonlinear mappings can not be distinguished from ordinary mappings.
> > This patch adds into /proc/pid/smaps line "Nonlinear:<size>  kB", where size is
> > amount of nonlinear ptes in vma, this line appears only if VM_NONLINEAR is set.
> > This information may be useful not only for checkpoint/restore project.
> >
> > Signed-off-by: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>
> > Requested-by: Pavel Emelyanov<xemul@xxxxxxxxxxxxx>
> > ---
> >   fs/proc/task_mmu.c |   12 ++++++++++++
> >   1 file changed, 12 insertions(+)
> >
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index acee5fd..b1d9729 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -393,6 +393,7 @@ struct mem_size_stats {
> >         unsigned long anonymous;
> >         unsigned long anonymous_thp;
> >         unsigned long swap;
> > +       unsigned long nonlinear;
> >         u64 pss;
> >   };
> >
> > @@ -402,6 +403,7 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr,
> >   {
> >         struct mem_size_stats *mss = walk->private;
> >         struct vm_area_struct *vma = mss->vma;
> > +       pgoff_t pgoff = linear_page_index(vma, addr);
> >         struct page *page = NULL;
> >         int mapcount;
> >
> > @@ -414,6 +416,9 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr,
> >                         mss->swap += ptent_size;
> >                 else if (is_migration_entry(swpent))
> >                         page = migration_entry_to_page(swpent);
> > +       } else if (pte_file(ptent)) {
> > +               if (pte_to_pgoff(ptent) != pgoff)
> > +                       mss->nonlinear += ptent_size;
>
> I think this is not equal to our non linear mapping definition. Even if
> pgoff is equal to linear mapping case, it is non linear. I.e. nonlinear is
> vma attribute. Why do you want to introduce different definition?

VMA attribute can be determined via presence of this field,
without VM_NONLINEAR it does not appears.
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