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Subject[RFC][PATCH] vmscan: report vm_flags in page_referenced()
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;
if (!mapcount)
break;
}
@@ -418,6 +421,7 @@ 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 the encountered vma->vm_flags
*
* For an object-based mapped page, find all the places it is mapped and
* check/clear the referenced flag. This is done by following the page->mapping
@@ -427,7 +431,8 @@ static int page_referenced_anon(struct p
* This function is only called from page_referenced for object-based pages.
*/
static int page_referenced_file(struct page *page,
- struct mem_cgroup *mem_cont)
+ struct mem_cgroup *mem_cont,
+ unsigned long *vm_flags)
{
unsigned int mapcount;
struct address_space *mapping = page->mapping;
@@ -468,6 +473,7 @@ static int page_referenced_file(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;
if (!mapcount)
break;
}
@@ -481,29 +487,35 @@ static int page_referenced_file(struct p
* @page: the page to test
* @is_locked: caller holds lock on the page
* @mem_cont: target memory controller
+ * @vm_flags: collect the encountered vma->vm_flags
*
* Quick test_and_clear_referenced for all mappings to a page,
* returns the number of ptes which referenced the page.
*/
-int page_referenced(struct page *page, int is_locked,
- struct mem_cgroup *mem_cont)
+int page_referenced(struct page *page,
+ int is_locked,
+ struct mem_cgroup *mem_cont,
+ unsigned long *vm_flags)
{
int referenced = 0;

if (TestClearPageReferenced(page))
referenced++;

+ *vm_flags = 0;
if (page_mapped(page) && page->mapping) {
if (PageAnon(page))
- referenced += page_referenced_anon(page, mem_cont);
+ referenced += page_referenced_anon(page, mem_cont,
+ vm_flags);
else if (is_locked)
- referenced += page_referenced_file(page, mem_cont);
+ referenced += page_referenced_file(page, mem_cont,
+ vm_flags);
else if (!trylock_page(page))
referenced++;
else {
if (page->mapping)
- referenced +=
- page_referenced_file(page, mem_cont);
+ referenced += page_referenced_file(page,
+ mem_cont, vm_flags);
unlock_page(page);
}
}
--- linux.orig/mm/vmscan.c
+++ linux/mm/vmscan.c
@@ -598,6 +598,7 @@ static unsigned long shrink_page_list(st
struct pagevec freed_pvec;
int pgactivate = 0;
unsigned long nr_reclaimed = 0;
+ unsigned long vm_flags;

cond_resched();

@@ -648,7 +649,8 @@ static unsigned long shrink_page_list(st
goto keep_locked;
}

- referenced = page_referenced(page, 1, sc->mem_cgroup);
+ referenced = page_referenced(page, 1,
+ sc->mem_cgroup, &vm_flags);
/* In active use or really unfreeable? Activate it. */
if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
referenced && page_mapping_inuse(page))
@@ -1229,6 +1231,7 @@ static void shrink_active_list(unsigned
{
unsigned long pgmoved;
unsigned long pgscanned;
+ unsigned long vm_flags;
LIST_HEAD(l_hold); /* The pages which were snipped off */
LIST_HEAD(l_inactive);
struct page *page;
@@ -1269,7 +1272,7 @@ 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, &vm_flags))
pgmoved++;

list_add(&page->lru, &l_inactive);

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