From 49255c619fbd482d704289b5eb2795f8e3b7ff2e Mon Sep 17 00:00:00 2001
From: Mel Gorman <mel@csn.ul.ie>
Date: Tue, 16 Jun 2009 15:31:58 -0700
Subject: page allocator: move check for disabled anti-fragmentation out of
 fastpath

On low-memory systems, anti-fragmentation gets disabled as there is
nothing it can do and it would just incur overhead shuffling pages between
lists constantly.  Currently the check is made in the free page fast path
for every page.  This patch moves it to a slow path.  On machines with low
memory, there will be small amount of additional overhead as pages get
shuffled between lists but it should quickly settle.

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 | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'mm/page_alloc.c')

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 512bf9a618c7..b09859629e93 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -168,6 +168,10 @@ int page_group_by_mobility_disabled __read_mostly;
 
 static void set_pageblock_migratetype(struct page *page, int migratetype)
 {
+
+	if (unlikely(page_group_by_mobility_disabled))
+		migratetype = MIGRATE_UNMOVABLE;
+
 	set_pageblock_flags_group(page, (unsigned long)migratetype,
 					PB_migrate, PB_migrate_end);
 }
-- 
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