Re: [PATCH 01/11] mm: page_alloc: handle MIGRATE_ISOLATE infree_pcppages_bulk()
From: Michal Nazarewicz
Date: Mon Dec 12 2011 - 09:23:12 EST
On Fri, Nov 18, 2011 at 05:43:08PM +0100, Marek Szyprowski wrote:
From: Michal Nazarewicz <mina86@xxxxxxxxxx>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9dd443d..58d1a2e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -628,6 +628,18 @@ static void free_pcppages_bulk(struct zone *zone, int count,
page = list_entry(list->prev, struct page, lru);
/* must delete as __free_one_page list manipulates */
list_del(&page->lru);
+
+ /*
+ * When page is isolated in set_migratetype_isolate()
+ * function it's page_private is not changed since the
+ * function has no way of knowing if it can touch it.
+ * This means that when a page is on PCP list, it's
+ * page_private no longer matches the desired migrate
+ * type.
+ */
+ if (get_pageblock_migratetype(page) == MIGRATE_ISOLATE)
+ set_page_private(page, MIGRATE_ISOLATE);
+
On Mon, 12 Dec 2011 14:42:35 +0100, Mel Gorman <mel@xxxxxxxxx> wrote:
How much of a problem is this in practice?
IIRC, this lead to allocation being made from area marked as isolated
or some such.
[...] I'd go as far to say that it would be preferable to drain the
per-CPU lists after you set pageblocks MIGRATE_ISOLATE. The IPIs also have
overhead but it will be incurred for the rare rather than the common case.
I'll look into that.
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, MichaÅ âmina86â Nazarewicz (o o)
ooo +----<email/xmpp: mpn@xxxxxxxxxx>--------------ooO--(_)--Ooo--
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