[PATCH 1/3] mm, vmscan: count accidental reclaimed pages failed to put into lru

[Joonsoo Kim]

In shrink_(in)active_list(), we can fail to put into lru, and these pages
are reclaimed accidentally. Currently, these pages are not counted
for sc->nr_reclaimed, but with this information, we can stop to reclaim
earlier, so can reduce overhead of reclaim.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 0f615eb..5d60ae0 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -365,7 +365,7 @@ void *alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask);
 extern void __free_pages(struct page *page, unsigned int order);
 extern void free_pages(unsigned long addr, unsigned int order);
 extern void free_hot_cold_page(struct page *page, int cold);
-extern void free_hot_cold_page_list(struct list_head *list, int cold);
+extern unsigned long free_hot_cold_page_list(struct list_head *list, int cold);
 
 extern void __free_memcg_kmem_pages(struct page *page, unsigned int order);
 extern void free_memcg_kmem_pages(unsigned long addr, unsigned int order);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8fcced7..a5f3952 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1360,14 +1360,18 @@ out:
 /*
  * Free a list of 0-order pages
  */
-void free_hot_cold_page_list(struct list_head *list, int cold)
+unsigned long free_hot_cold_page_list(struct list_head *list, int cold)
 {
+	unsigned long nr_reclaimed = 0;
 	struct page *page, *next;
 
 	list_for_each_entry_safe(page, next, list, lru) {
 		trace_mm_page_free_batched(page, cold);
 		free_hot_cold_page(page, cold);
+		nr_reclaimed++;
 	}
+
+	return nr_reclaimed;
 }
 
 /*
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 88c5fed..eff2927 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -915,7 +915,6 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		 */
 		__clear_page_locked(page);
 free_it:
-		nr_reclaimed++;
 
 		/*
 		 * Is there need to periodically free_page_list? It would
@@ -954,7 +953,7 @@ keep:
 	if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc))
 		zone_set_flag(zone, ZONE_CONGESTED);
 
-	free_hot_cold_page_list(&free_pages, 1);
+	nr_reclaimed += free_hot_cold_page_list(&free_pages, 1);
 
 	list_splice(&ret_pages, page_list);
 	count_vm_events(PGACTIVATE, pgactivate);
@@ -1321,7 +1320,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 	if (nr_taken == 0)
 		return 0;
 
-	nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
+	nr_reclaimed += shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
 					&nr_dirty, &nr_writeback, false);
 
 	spin_lock_irq(&zone->lru_lock);
@@ -1343,7 +1342,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 
 	spin_unlock_irq(&zone->lru_lock);
 
-	free_hot_cold_page_list(&page_list, 1);
+	nr_reclaimed += free_hot_cold_page_list(&page_list, 1);
 
 	/*
 	 * If reclaim is isolating dirty pages under writeback, it implies
@@ -1438,7 +1437,7 @@ static void move_active_pages_to_lru(struct lruvec *lruvec,
 		__count_vm_events(PGDEACTIVATE, pgmoved);
 }
 
-static void shrink_active_list(unsigned long nr_to_scan,
+static unsigned long shrink_active_list(unsigned long nr_to_scan,
 			       struct lruvec *lruvec,
 			       struct scan_control *sc,
 			       enum lru_list lru)
@@ -1534,7 +1533,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
 	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
 	spin_unlock_irq(&zone->lru_lock);
 
-	free_hot_cold_page_list(&l_hold, 1);
+	return free_hot_cold_page_list(&l_hold, 1);
 }
 
 #ifdef CONFIG_SWAP
@@ -1617,7 +1616,8 @@ static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
 {
 	if (is_active_lru(lru)) {
 		if (inactive_list_is_low(lruvec, lru))
-			shrink_active_list(nr_to_scan, lruvec, sc, lru);
+			return shrink_active_list(nr_to_scan, lruvec, sc, lru);
+
 		return 0;
 	}
 
@@ -1861,8 +1861,8 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
 	 * rebalance the anon lru active/inactive ratio.
 	 */
 	if (inactive_anon_is_low(lruvec))
-		shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
-				   sc, LRU_ACTIVE_ANON);
+		sc->nr_reclaimed += shrink_active_list(SWAP_CLUSTER_MAX,
+					lruvec, sc, LRU_ACTIVE_ANON);
 
 	throttle_vm_writeout(sc->gfp_mask);
 }
@@ -2470,23 +2470,27 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 }
 #endif
 
-static void age_active_anon(struct zone *zone, struct scan_control *sc)
+static unsigned long age_active_anon(struct zone *zone,
+					struct scan_control *sc)
 {
+	unsigned long nr_reclaimed = 0;
 	struct mem_cgroup *memcg;
 
 	if (!total_swap_pages)
-		return;
+		return 0;
 
 	memcg = mem_cgroup_iter(NULL, NULL, NULL);
 	do {
 		struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
 
 		if (inactive_anon_is_low(lruvec))
-			shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
-					   sc, LRU_ACTIVE_ANON);
+			nr_reclaimed += shrink_active_list(SWAP_CLUSTER_MAX,
+					lruvec, sc, LRU_ACTIVE_ANON);
 
 		memcg = mem_cgroup_iter(NULL, memcg, NULL);
 	} while (memcg);
+
+	return nr_reclaimed;
 }
 
 static bool zone_balanced(struct zone *zone, int order,
@@ -2666,7 +2670,7 @@ loop_again:
 			 * Do some background aging of the anon list, to give
 			 * pages a chance to be referenced before reclaiming.
 			 */
-			age_active_anon(zone, &sc);
+			sc.nr_reclaimed += age_active_anon(zone, &sc);
 
 			/*
 			 * If the number of buffer_heads in the machine
-- 
1.7.9.5

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