[PATCH] RSS Container, make page_referenced() container aware

[Balbir Singh]

Hi, Pavel,

This patch should help with the shared page issue of one container
holding shared pages in a another container (the container that
brought in the page -- by first touch) hostage.

--
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL


Make page_referenced() container aware. Without this patch, page_referenced()
can cause a page to be skipped while reclaiming pages. This patch
ensures that other containers do not hold pages in a particular container
hostage. It is required to ensure that shared pages are freed from a container
when they are not actively referenced from the container that brought
them in

Signed-off-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
---

 include/linux/rmap.h |    5 +++--
 mm/rmap.c            |   26 ++++++++++++++++++++------
 mm/vmscan.c          |    4 ++--
 3 files changed, 25 insertions(+), 10 deletions(-)

diff -puN mm/vmscan.c~rss-implement-per-container-page-referenced mm/vmscan.c
--- linux-2.6.20/mm/vmscan.c~rss-implement-per-container-page-referenced	2007-04-26 23:28:44.000000000 +0530
+++ linux-2.6.20-balbir/mm/vmscan.c	2007-04-27 00:04:38.000000000 +0530
@@ -489,7 +489,7 @@ static unsigned long shrink_page_list(st
 		if (PageWriteback(page))
 			goto keep_locked;
 
-		referenced = page_referenced(page, 1);
+		referenced = page_referenced(page, 1, sc->cnt);
 		/* In active use or really unfreeable?  Activate it. */
 		if (referenced && page_mapping_inuse(page))
 			goto activate_locked;
@@ -852,7 +852,7 @@ force_reclaim_mapped:
 		if (page_mapped(page)) {
 			if (!reclaim_mapped ||
 			    (total_swap_pages == 0 && PageAnon(page)) ||
-			    page_referenced(page, 0)) {
+			    page_referenced(page, 0, sc->cnt)) {
 				list_add(&page->lru, &l_active);
 				continue;
 			}
diff -puN mm/rmap.c~rss-implement-per-container-page-referenced mm/rmap.c
--- linux-2.6.20/mm/rmap.c~rss-implement-per-container-page-referenced	2007-04-26 23:28:44.000000000 +0530
+++ linux-2.6.20-balbir/mm/rmap.c	2007-04-26 23:33:41.000000000 +0530
@@ -318,7 +318,7 @@ out:
 	return referenced;
 }
 
-static int page_referenced_anon(struct page *page)
+static int page_referenced_anon(struct page *page, struct rss_container *cnt)
 {
 	unsigned int mapcount;
 	struct anon_vma *anon_vma;
@@ -331,6 +331,13 @@ static int page_referenced_anon(struct p
 
 	mapcount = page_mapcount(page);
 	list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
+		/*
+		 * If we are reclaiming on behalf of a container, skip
+		 * counting on behalf of references from different
+		 * containers
+		 */
+		if (cnt && (vma->vm_mm->rss_container != cnt))
+			continue;
 		referenced += page_referenced_one(page, vma, &mapcount);
 		if (!mapcount)
 			break;
@@ -350,7 +357,7 @@ 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)
+static int page_referenced_file(struct page *page, struct rss_container *cnt)
 {
 	unsigned int mapcount;
 	struct address_space *mapping = page->mapping;
@@ -383,6 +390,13 @@ static int page_referenced_file(struct p
 	mapcount = page_mapcount(page);
 
 	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
+		/*
+		 * If we are reclaiming on behalf of a container, skip
+		 * counting on behalf of references from different
+		 * containers
+		 */
+		if (cnt && (vma->vm_mm->rss_container != cnt))
+			continue;
 		if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
 				  == (VM_LOCKED|VM_MAYSHARE)) {
 			referenced++;
@@ -405,7 +419,7 @@ static int page_referenced_file(struct p
  * 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)
+int page_referenced(struct page *page, int is_locked, struct rss_container *cnt)
 {
 	int referenced = 0;
 
@@ -417,14 +431,14 @@ int page_referenced(struct page *page, i
 
 	if (page_mapped(page) && page->mapping) {
 		if (PageAnon(page))
-			referenced += page_referenced_anon(page);
+			referenced += page_referenced_anon(page, cnt);
 		else if (is_locked)
-			referenced += page_referenced_file(page);
+			referenced += page_referenced_file(page, cnt);
 		else if (TestSetPageLocked(page))
 			referenced++;
 		else {
 			if (page->mapping)
-				referenced += page_referenced_file(page);
+				referenced += page_referenced_file(page, cnt);
 			unlock_page(page);
 		}
 	}
diff -puN include/linux/rmap.h~rss-implement-per-container-page-referenced include/linux/rmap.h
--- linux-2.6.20/include/linux/rmap.h~rss-implement-per-container-page-referenced	2007-04-26 23:28:44.000000000 +0530
+++ linux-2.6.20-balbir/include/linux/rmap.h	2007-04-26 23:29:31.000000000 +0530
@@ -8,6 +8,7 @@
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/spinlock.h>
+#include <linux/rss_container.h>
 
 /*
  * The anon_vma heads a list of private "related" vmas, to scan if
@@ -93,7 +94,7 @@ static inline void page_dup_rmap(struct 
 /*
  * Called from mm/vmscan.c to handle paging out
  */
-int page_referenced(struct page *, int is_locked);
+int page_referenced(struct page *, int is_locked, struct rss_container *cnt);
 int try_to_unmap(struct page *, int ignore_refs);
 
 /*
@@ -121,7 +122,7 @@ int page_mkclean(struct page *);
 #define anon_vma_prepare(vma)	(0)
 #define anon_vma_link(vma)	do {} while (0)
 
-#define page_referenced(page,l) TestClearPageReferenced(page)
+#define page_referenced(page,l,cnt) TestClearPageReferenced(page)
 #define try_to_unmap(page, refs) SWAP_FAIL
 
 static inline int page_mkclean(struct page *page)
_