[RFC][PATCH] mm: the page of MIGRATE_RESERVE don't insert into pcp

[KOSAKI Motohiro]

MIGRATE_RESERVE mean that the page is for emergency.
So it shouldn't be cached in pcp.

otherwise, the system have unnecessary memory starvation risk
because other cpu can't use this emergency pages.



Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
CC: Mel Gorman <mel@xxxxxxxxx>
CC: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>

---
 mm/page_alloc.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Index: b/mm/page_alloc.c
===================================================================
--- a/mm/page_alloc.c	2008-11-06 06:01:15.000000000 +0900
+++ b/mm/page_alloc.c	2008-11-06 06:27:41.000000000 +0900
@@ -1002,6 +1002,7 @@ static void free_hot_cold_page(struct pa
 	struct zone *zone = page_zone(page);
 	struct per_cpu_pages *pcp;
 	unsigned long flags;
+	int migratetype = get_pageblock_migratetype(page);
 
 	if (PageAnon(page))
 		page->mapping = NULL;
@@ -1018,16 +1019,25 @@ static void free_hot_cold_page(struct pa
 	pcp = &zone_pcp(zone, get_cpu())->pcp;
 	local_irq_save(flags);
 	__count_vm_event(PGFREE);
+
+	set_page_private(page, migratetype);
+
+	/* the page for emergency shouldn't be cached */
+	if (migratetype == MIGRATE_RESERVE) {
+		free_one_page(zone, page, 0);
+		goto out;
+	}
 	if (cold)
 		list_add_tail(&page->lru, &pcp->list);
 	else
 		list_add(&page->lru, &pcp->list);
-	set_page_private(page, get_pageblock_migratetype(page));
 	pcp->count++;
 	if (pcp->count >= pcp->high) {
 		free_pages_bulk(zone, pcp->batch, &pcp->list, 0);
 		pcp->count -= pcp->batch;
 	}
+
+out:
 	local_irq_restore(flags);
 	put_cpu();
 }


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