Re: [PATCH] fix spurious OOM kills

[Andrew Morton]

Chris Ross <chris@xxxxxxxxxxxx> wrote:
>
> As I suspected, like a recalcitrant teenager it was sneakily waiting 
>  until everyone was out then it threw a wild party with several ooms and 
>  an oops. See below...

That's not an oops - it's just a stack trace.

>  This, obviously is still without Kame's patch, just the same tree as 
>  before with the one change you asked for.

Please ignore the previous patch and try the below.  It looks like Rik's
analysis is correct: when the caller doesn't have the swap token it just
cannot reclaim referenced pages and scans its way into an oom.  Defeating
that logic when we've hit the highest scanning priority does seem to fix
the problem and those nice qsbench numbers which the thrashing control gave
us appear to be unaffected.


diff -puN mm/vmscan.c~vmscan-ignore-swap-token-when-in-trouble mm/vmscan.c
--- 25/mm/vmscan.c~vmscan-ignore-swap-token-when-in-trouble	2004-11-16 20:30:00.000000000 -0800
+++ 25-akpm/mm/vmscan.c	2004-11-16 20:30:00.000000000 -0800
@@ -380,7 +380,7 @@ static int shrink_list(struct list_head 
 		if (page_mapped(page) || PageSwapCache(page))
 			sc->nr_scanned++;
 
-		referenced = page_referenced(page, 1);
+		referenced = page_referenced(page, 1, sc->priority <= 0);
 		/* In active use or really unfreeable?  Activate it. */
 		if (referenced && page_mapping_inuse(page))
 			goto activate_locked;
@@ -724,7 +724,7 @@ refill_inactive_zone(struct zone *zone, 
 		if (page_mapped(page)) {
 			if (!reclaim_mapped ||
 			    (total_swap_pages == 0 && PageAnon(page)) ||
-			    page_referenced(page, 0)) {
+			    page_referenced(page, 0, sc->priority <= 0)) {
 				list_add(&page->lru, &l_active);
 				continue;
 			}
diff -puN mm/rmap.c~vmscan-ignore-swap-token-when-in-trouble mm/rmap.c
--- 25/mm/rmap.c~vmscan-ignore-swap-token-when-in-trouble	2004-11-16 20:30:00.000000000 -0800
+++ 25-akpm/mm/rmap.c	2004-11-16 20:30:00.000000000 -0800
@@ -248,7 +248,7 @@ unsigned long page_address_in_vma(struct
  * 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, int ignore_token)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	unsigned long address;
@@ -288,7 +288,7 @@ static int page_referenced_one(struct pa
 	if (ptep_clear_flush_young(vma, address, pte))
 		referenced++;
 
-	if (mm != current->mm && has_swap_token(mm))
+	if (mm != current->mm && !ignore_token && has_swap_token(mm))
 		referenced++;
 
 	(*mapcount)--;
@@ -301,7 +301,7 @@ out:
 	return referenced;
 }
 
-static int page_referenced_anon(struct page *page)
+static int page_referenced_anon(struct page *page, int ignore_token)
 {
 	unsigned int mapcount;
 	struct anon_vma *anon_vma;
@@ -314,7 +314,8 @@ static int page_referenced_anon(struct p
 
 	mapcount = page_mapcount(page);
 	list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
-		referenced += page_referenced_one(page, vma, &mapcount);
+		referenced += page_referenced_one(page, vma, &mapcount,
+							ignore_token);
 		if (!mapcount)
 			break;
 	}
@@ -333,7 +334,7 @@ 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, int ignore_token)
 {
 	unsigned int mapcount;
 	struct address_space *mapping = page->mapping;
@@ -371,7 +372,8 @@ static int page_referenced_file(struct p
 			referenced++;
 			break;
 		}
-		referenced += page_referenced_one(page, vma, &mapcount);
+		referenced += page_referenced_one(page, vma, &mapcount,
+							ignore_token);
 		if (!mapcount)
 			break;
 	}
@@ -388,7 +390,7 @@ 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, int ignore_token)
 {
 	int referenced = 0;
 
@@ -400,14 +402,15 @@ 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, ignore_token);
 		else if (is_locked)
-			referenced += page_referenced_file(page);
+			referenced += page_referenced_file(page, ignore_token);
 		else if (TestSetPageLocked(page))
 			referenced++;
 		else {
 			if (page->mapping)
-				referenced += page_referenced_file(page);
+				referenced += page_referenced_file(page,
+								ignore_token);
 			unlock_page(page);
 		}
 	}
diff -puN include/linux/rmap.h~vmscan-ignore-swap-token-when-in-trouble include/linux/rmap.h
--- 25/include/linux/rmap.h~vmscan-ignore-swap-token-when-in-trouble	2004-11-16 20:30:00.000000000 -0800
+++ 25-akpm/include/linux/rmap.h	2004-11-16 20:30:00.000000000 -0800
@@ -89,7 +89,7 @@ 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, int ignore_token);
 int try_to_unmap(struct page *);
 
 /*
@@ -103,7 +103,7 @@ unsigned long page_address_in_vma(struct
 #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,i) TestClearPageReferenced(page)
 #define try_to_unmap(page)	SWAP_FAIL
 
 #endif	/* CONFIG_MMU */
_

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