From: Weijie Yang <weijie.yang@samsung.com>
To: iamjoonsoo.kim@lge.com
Cc: "'Andrew Morton'" <akpm@linux-foundation.org>, mgorman@suse.de,
        "'Rik van Riel'" <riel@redhat.com>, vbabka@suse.cz,
        "'Johannes Weiner'" <hannes@cmpxchg.org>,
        "'Minchan Kim'" <minchan@kernel.org>,
        "'Weijie Yang'" <weijie.yang.kh@gmail.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH 3/3] mm: page_alloc: remove redundant
 set_freepage_migratetype() calls
Date: Tue, 09 Dec 2014 15:51:49 +0800
Message-id: <000301d01385$45554a60$cfffdf20$%yang@samsung.com>
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Sender: linux-kernel-owner@vger.kernel.org

The freepage_migratetype is a temporary cached value which represents
the free page's pageblock migratetype. Now we use it in two scenarios:

1. Use it as a cached value in page freeing path. This cached value
is temporary and non-100% update, which help us decide which pcp
freelist and buddy freelist the page should go rather than using
get_pfnblock_migratetype() to save some instructions.
When there is race between page isolation and free path, we need use
additional method to get a accurate value to put the free pages to
the correct freelist and get a precise free pages statistics.

2. Use it in page alloc path to update NR_FREE_CMA_PAGES statistics.

This patch aims at the scenario 1 and removes two redundant
set_freepage_migratetype() calls, which will make sense in the hot path.

Signed-off-by: Weijie Yang <weijie.yang@samsung.com>
---
 mm/page_alloc.c |    2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 616a2c9..99af01a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -775,7 +775,6 @@ static void __free_pages_ok(struct page *page, unsigned int order)
 	migratetype = get_pfnblock_migratetype(page, pfn);
 	local_irq_save(flags);
 	__count_vm_events(PGFREE, 1 << order);
-	set_freepage_migratetype(page, migratetype);
 	free_one_page(page_zone(page), page, pfn, order, migratetype);
 	local_irq_restore(flags);
 }
@@ -1024,7 +1023,6 @@ int move_freepages(struct zone *zone,
 		order = page_order(page);
 		list_move(&page->lru,
 			  &zone->free_area[order].free_list[migratetype]);
-		set_freepage_migratetype(page, migratetype);
 		page += 1 << order;
 		pages_moved += 1 << order;
 	}
-- 
1.7.10.4


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