linux-kernel - [PATCH 2/5]memhp: exclude isolated page from pco page alloc

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Date:	Mon, 29 Jun 2009 09:47:12 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	lkml <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, cl@...ux-foundation.org
Subject: [PATCH 2/5]memhp: exclude isolated page from pco page alloc

pages marked as isolated should not be allocated again. If such
pages reside in pcp list, they can be allocated too, so there is
a ping-pong memory offline frees some pages to pcp list and the
pages get allocated and then memory offline frees them again,
this loop will happen again and again.

This should have no impact in normal code path, because in normal
code path, pages in pcp list aren't isolated, and below loop will
break in the first entry.

Signed-off-by: Shaohua Li <shaohua.li@...el.com>
---
 mm/page_alloc.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

Index: linux/mm/page_alloc.c
===================================================================
--- linux.orig/mm/page_alloc.c	2009-06-26 09:41:10.000000000 +0800
+++ linux/mm/page_alloc.c	2009-06-26 09:44:07.000000000 +0800
@@ -1137,9 +1137,18 @@ again:
 
 		/* Allocate more to the pcp list if necessary */
 		if (unlikely(&page->lru == &pcp->list)) {
+			int get_one_page = 0;
 			pcp->count += rmqueue_bulk(zone, 0,
 					pcp->batch, &pcp->list, migratetype);
-			page = list_entry(pcp->list.next, struct page, lru);
+			list_for_each_entry(page, &pcp->list, lru) {
+				if (get_pageblock_migratetype(page) !=
+				    MIGRATE_ISOLATE) {
+					get_one_page = 1;
+					break;
+				}
+			}
+			if (!get_one_page)
+				goto failed;
 		}
 
 		list_del(&page->lru);


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