linux-kernel - Re: [PATCH 08/10] mm/page_alloc: use get_onbuddy

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Message-ID: <20140714063401.GD11317@js1304-P5Q-DELUXE>
Date:	Mon, 14 Jul 2014 15:34:02 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan@...nel.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Laura Abbott <lauraa@...eaurora.org>,
	Heesub Shin <heesub.shin@...sung.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Ritesh Harjani <ritesh.list@...il.com>,
	t.stanislaws@...sung.com, Gioh Kim <gioh.kim@....com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/10] mm/page_alloc: use get_onbuddy_migratetype() to
 get buddy list type

On Mon, Jul 07, 2014 at 05:57:49PM +0200, Vlastimil Babka wrote:
> On 07/04/2014 09:57 AM, Joonsoo Kim wrote:
> >When isolating free page, what we want to know is which list
> >the page is linked. If it is linked in isolate migratetype buddy list,
> >we can skip watermark check and freepage counting. And if it is linked
> >in CMA migratetype buddy list, we need to fixup freepage counting. For
> >this purpose, get_onbuddy_migratetype() is more fit and cheap than
> >get_pageblock_migratetype(). So use it.
> 
> Hm but you made get_onbuddy_migratetype() work only with
> CONFIG_MEMORY_ISOLATION. And __isolate_free_page is (despite the
> name) not at all limited to CONFIG_MEMORY_ISOLATION.

get_onbuddy_migratetype() is only used for determining whether this
page is on isolate buddy list or not. So if !CONFIG_MEMORY_ISOLATION,
default value of get_onbuddy_migratetype() makes things correct.

But, I should write some code comment.

Thanks.
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