From ed0ae21dc5fe3b9ad4cf1c7bb2bfd2ad596c481c Mon Sep 17 00:00:00 2001
From: Mel Gorman <mel@csn.ul.ie>
Date: Tue, 16 Jun 2009 15:32:07 -0700
Subject: [PATCH] page allocator: do not call get_pageblock_migratetype() more
 than necessary

get_pageblock_migratetype() is potentially called twice for every page
free.  Once, when being freed to the pcp lists and once when being freed
back to buddy.  When freeing from the pcp lists, it is known what the
pageblock type was at the time of free so use it rather than rechecking.
In low memory situations under memory pressure, this might skew
anti-fragmentation slightly but the interference is minimal and decisions
that are fragmenting memory are being made anyway.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/page_alloc.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 91e29b3ed2b6..8f334d339b08 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -452,16 +452,18 @@ static inline int page_is_buddy(struct page *page, struct page *buddy,
  */
 
 static inline void __free_one_page(struct page *page,
-		struct zone *zone, unsigned int order)
+		struct zone *zone, unsigned int order,
+		int migratetype)
 {
 	unsigned long page_idx;
 	int order_size = 1 << order;
-	int migratetype = get_pageblock_migratetype(page);
 
 	if (unlikely(PageCompound(page)))
 		if (unlikely(destroy_compound_page(page, order)))
 			return;
 
+	VM_BUG_ON(migratetype == -1);
+
 	page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
 
 	VM_BUG_ON(page_idx & (order_size - 1));
@@ -530,17 +532,18 @@ static void free_pages_bulk(struct zone *zone, int count,
 		page = list_entry(list->prev, struct page, lru);
 		/* have to delete it as __free_one_page list manipulates */
 		list_del(&page->lru);
-		__free_one_page(page, zone, order);
+		__free_one_page(page, zone, order, page_private(page));
 	}
 	spin_unlock(&zone->lock);
 }
 
-static void free_one_page(struct zone *zone, struct page *page, int order)
+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;
-	__free_one_page(page, zone, order);
+	__free_one_page(page, zone, order, migratetype);
 	spin_unlock(&zone->lock);
 }
 
@@ -565,7 +568,8 @@ static void __free_pages_ok(struct page *page, unsigned int order)
 
 	local_irq_save(flags);
 	__count_vm_events(PGFREE, 1 << order);
-	free_one_page(page_zone(page), page, order);
+	free_one_page(page_zone(page), page, order,
+					get_pageblock_migratetype(page));
 	local_irq_restore(flags);
 }
 
-- 
GitLab