[PATCH 4/4] mm/page_alloc : relieve zone->lock's pressure for memory free

[Huang Shijie <shijie8@gmail.com>]

  Move the __mod_zone_page_state out the guard region of
the spinlock to relieve the pressure for memory free.

  Using the zone->lru_lock to replace the zone->lock for
zone->pages_scanned and zone's flag ZONE_ALL_UNRECLAIMABLE.

Signed-off-by: Huang Shijie <shijie8@gmail.com>
---
 mm/page_alloc.c |   33 +++++++++++++++++++++++----------
 1 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 290dfc3..dfd4be0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -530,12 +530,9 @@ static void free_pcppages_bulk(struct zone *zone, int count,
 {
 	int migratetype = 0;
 	int batch_free = 0;
+	int free_ok = 0;
 
 	spin_lock(&zone->lock);
-	zone_clear_flag(zone, ZONE_ALL_UNRECLAIMABLE);
-	zone->pages_scanned = 0;
-
-	__mod_zone_page_state(zone, NR_FREE_PAGES, count);
 	while (count) {
 		struct page *page;
 		struct list_head *list;
@@ -558,23 +555,39 @@ static void free_pcppages_bulk(struct zone *zone, int count,
 			page = list_entry(list->prev, struct page, lru);
 			/* must delete as __free_one_page list manipulates */
 			list_del(&page->lru);
-			__free_one_page(page, zone, 0, migratetype);
+			free_ok += __free_one_page(page, zone, 0, migratetype);
 			trace_mm_page_pcpu_drain(page, 0, migratetype);
 		} while (--count && --batch_free && !list_empty(list));
 	}
 	spin_unlock(&zone->lock);
+
+	if (likely(free_ok)) {
+		spin_lock(&zone->lru_lock);
+		zone_clear_flag(zone, ZONE_ALL_UNRECLAIMABLE);
+		zone->pages_scanned = 0;
+		spin_unlock(&zone->lru_lock);
+
+		__mod_zone_page_state(zone, NR_FREE_PAGES, free_ok);
+	}
 }
 
 static void free_one_page(struct zone *zone, struct page *page, int order,
 				int migratetype)
 {
-	spin_lock(&zone->lock);
-	zone_clear_flag(zone, ZONE_ALL_UNRECLAIMABLE);
-	zone->pages_scanned = 0;
+	int free_ok;
 
-	__mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
-	__free_one_page(page, zone, order, migratetype);
+	spin_lock(&zone->lock);
+	free_ok = __free_one_page(page, zone, order, migratetype);
 	spin_unlock(&zone->lock);
+
+	if (likely(free_ok)) {
+		spin_lock(&zone->lru_lock);
+		zone_clear_flag(zone, ZONE_ALL_UNRECLAIMABLE);
+		zone->pages_scanned = 0;
+		spin_unlock(&zone->lru_lock);
+
+		__mod_zone_page_state(zone, NR_FREE_PAGES, free_ok << order);
+	}
 }
 
 static void __free_pages_ok(struct page *page, unsigned int order)
-- 
1.6.5.2

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