Re: [PATCH 1/3] vmscan: report vm_flags in page_referenced()

[Wu Fengguang <fengguang.wu@intel.com>]

On Sun, May 17, 2009 at 09:36:44AM +0800, Minchan Kim wrote:
> On Sat, May 16, 2009 at 6:00 PM, Wu Fengguang <fengguang.wu@intel.com> wrote:
> > Collect vma->vm_flags of the VMAs that actually referenced the page.
> >
> > This is preparing for more informed reclaim heuristics,
> > eg. to protect executable file pages more aggressively.
> > For now only the VM_EXEC bit will be used by the caller.
> >
> > CC: Minchan Kim <minchan.kim@gmail.com>
> > CC: Johannes Weiner <hannes@cmpxchg.org>
> > CC: Peter Zijlstra <peterz@infradead.org>
> > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> > ---
> >  include/linux/rmap.h |    5 +++--
> >  mm/rmap.c            |   37 ++++++++++++++++++++++++++-----------
> >  mm/vmscan.c          |    7 +++++--
> >  3 files changed, 34 insertions(+), 15 deletions(-)
> >
> > --- linux.orig/include/linux/rmap.h
> > +++ linux/include/linux/rmap.h
> > @@ -83,7 +83,8 @@ static inline void page_dup_rmap(struct
> >  /*
> >  * Called from mm/vmscan.c to handle paging out
> >  */
> > -int page_referenced(struct page *, int is_locked, struct mem_cgroup *cnt);
> > +int page_referenced(struct page *, int is_locked,
> > +                       struct mem_cgroup *cnt, unsigned long *vm_flags);
> >  int try_to_unmap(struct page *, int ignore_refs);
> >
> >  /*
> > @@ -128,7 +129,7 @@ int page_wrprotect(struct page *page, in
> >  #define anon_vma_prepare(vma)  (0)
> >  #define anon_vma_link(vma)     do {} while (0)
> >
> > -#define page_referenced(page,l,cnt) TestClearPageReferenced(page)
> > +#define page_referenced(page, locked, cnt, flags) TestClearPageReferenced(page)
> >  #define try_to_unmap(page, refs) SWAP_FAIL
> >
> >  static inline int page_mkclean(struct page *page)
> > --- linux.orig/mm/rmap.c
> > +++ linux/mm/rmap.c
> > @@ -333,7 +333,9 @@ static int page_mapped_in_vma(struct pag
> >  * repeatedly from either page_referenced_anon or page_referenced_file.
> >  */
> >  static int page_referenced_one(struct page *page,
> > -       struct vm_area_struct *vma, unsigned int *mapcount)
> > +                              struct vm_area_struct *vma,
> > +                              unsigned int *mapcount,
> > +                              unsigned long *vm_flags)
> >  {
> >        struct mm_struct *mm = vma->vm_mm;
> >        unsigned long address;
> > @@ -381,11 +383,14 @@ out_unmap:
> >        (*mapcount)--;
> >        pte_unmap_unlock(pte, ptl);
> >  out:
> > +       if (referenced)
> > +               *vm_flags |= vma->vm_flags;
> >        return referenced;
> >  }
> >
> >  static int page_referenced_anon(struct page *page,
> > -                               struct mem_cgroup *mem_cont)
> > +                               struct mem_cgroup *mem_cont,
> > +                               unsigned long *vm_flags)
> >  {
> >        unsigned int mapcount;
> >        struct anon_vma *anon_vma;
> > @@ -405,7 +410,8 @@ static int page_referenced_anon(struct p
> >                 */
> >                if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
> >                        continue;
> > -               referenced += page_referenced_one(page, vma, &mapcount);
> > +               referenced += page_referenced_one(page, vma,
> > +                                                 &mapcount, vm_flags);
> >                if (!mapcount)
> >                        break;
> >        }
> > @@ -418,6 +424,7 @@ static int page_referenced_anon(struct p
> >  * page_referenced_file - referenced check for object-based rmap
> >  * @page: the page we're checking references on.
> >  * @mem_cont: target memory controller
> > + * @vm_flags: collect encountered vma->vm_flags
> 
> I missed this.
> To clarify, how about ?
> collect encountered vma->vm_flags among vma which referenced the page

Good catch! I'll resubmit the whole patchset :)

[ In fact I was thinking about changing those comments - and then
  forgot it over night. I should really put some notepad around me. ]

Thanks,
Fengguang