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Date: Mon, 12 Dec 2011 14:42:29 +0000
From: Mel Gorman <mel@....ul.ie>
To: Michal Nazarewicz <mina86@...a86.com>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-media@...r.kernel.org, linux-mm@...ck.org,
linaro-mm-sig@...ts.linaro.org,
Kyungmin Park <kyungmin.park@...sung.com>,
Russell King <linux@....linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Ankita Garg <ankita@...ibm.com>,
Daniel Walker <dwalker@...eaurora.org>,
Arnd Bergmann <arnd@...db.de>,
Jesse Barker <jesse.barker@...aro.org>,
Jonathan Corbet <corbet@....net>,
Shariq Hasnain <shariq.hasnain@...aro.org>,
Chunsang Jeong <chunsang.jeong@...aro.org>,
Dave Hansen <dave@...ux.vnet.ibm.com>
Subject: Re: [PATCH 01/11] mm: page_alloc: handle MIGRATE_ISOLATE in
free_pcppages_bulk()
On Mon, Dec 12, 2011 at 03:23:02PM +0100, Michal Nazarewicz wrote:
> >On Fri, Nov 18, 2011 at 05:43:08PM +0100, Marek Szyprowski wrote:
> >>From: Michal Nazarewicz <mina86@...a86.com>
> >>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@....ul.ie> 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.
>
And I believe that nothing prevents that from happening. I was just
wondering how common it was in practice. Draining the per-cpu lists
should work as a substitute either way.
--
Mel Gorman
SUSE Labs
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