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SubjectRe: [PATCH -mm] vmscan: make mapped executable pages the first class citizen
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.

I'd prefer to make vm_flags an out-param, like this:

- int page_referenced(struct page *page, int is_locked,
+ int page_referenced(struct page *page, int is_locked, unsigned long *vm_flags,
struct mem_cgroup *mem_cont)

which allows reporting more versatile flags and status bits :)

Thanks,
Fengguang



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