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    SubjectRe: [RFC][PATCH] vmscan: report vm_flags in page_referenced()
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    On Fri, May 8, 2009 at 1:17 PM, Wu Fengguang <fengguang.wu@intel.com> wrote:
    > On Thu, May 07, 2009 at 11:17:46PM +0800, Peter Zijlstra wrote:
    >> On Thu, 2009-05-07 at 17:10 +0200, Johannes Weiner wrote:
    >>
    >> > > @@ -1269,8 +1270,15 @@ static void shrink_active_list(unsigned
    >> > >
    >> > >           /* page_referenced clears PageReferenced */
    >> > >           if (page_mapping_inuse(page) &&
    >> > > -             page_referenced(page, 0, sc->mem_cgroup))
    >> > > +             page_referenced(page, 0, sc->mem_cgroup)) {
    >> > > +                 struct address_space *mapping = page_mapping(page);
    >> > > +
    >> > >                   pgmoved++;
    >> > > +                 if (mapping && test_bit(AS_EXEC, &mapping->flags)) {
    >> > > +                         list_add(&page->lru, &l_active);
    >> > > +                         continue;
    >> > > +                 }
    >> > > +         }
    >> >
    >> > Since we walk the VMAs in page_referenced anyway, wouldn't it be
    >> > better to check if one of them is executable?  This would even work
    >> > for executable anon pages.  After all, there are applications that cow
    >> > executable mappings (sbcl and other language environments that use an
    >> > executable, run-time modified core image come to mind).
    >>
    >> Hmm, like provide a vm_flags mask along to page_referenced() to only
    >> account matching vmas... seems like a sensible idea.
    >
    > Here is a quick patch for your opinions. Compile tested.
    >
    > With the added vm_flags reporting, the mlock=>unevictable logic can
    > possibly be made more straightforward.
    >
    > Thanks,
    > Fengguang
    > ---
    > vmscan: report vm_flags in page_referenced()
    >
    > This enables more informed reclaim heuristics, eg. to protect executable
    > file pages more aggressively.
    >
    > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
    > ---
    >  include/linux/rmap.h |    5 +++--
    >  mm/rmap.c            |   30 +++++++++++++++++++++---------
    >  mm/vmscan.c          |    7 +++++--
    >  3 files changed, 29 insertions(+), 13 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 +333,8 @@ 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)
    >  {
    >        struct mm_struct *mm = vma->vm_mm;
    >        unsigned long address;
    > @@ -385,7 +386,8 @@ out:
    >  }
    >
    >  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;
    > @@ -406,6 +408,7 @@ 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);
    > +               *vm_flags |= vma->vm_flags;

    Sometime this vma don't contain the anon page.
    That's why we need page_check_address.
    For such a case, wrong *vm_flag cause be harmful to reclaim.
    It can be happen in your first class citizen patch, I think.



    --
    Kinds regards,
    Minchan Kim
    --
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