linux-kernel - Re: [PATCH 2/4] mm/page_alloc: expands broken freepage to proper buddy list when steal

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Date:	Wed, 10 Dec 2014 10:55:02 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Rik van Riel <riel@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] mm/page_alloc: expands broken freepage to proper
 buddy list when steal

On 12/10/2014 07:38 AM, Joonsoo Kim wrote:
> On Mon, Dec 08, 2014 at 10:29:44AM +0100, Vlastimil Babka wrote:
>> On 12/08/2014 08:16 AM, Joonsoo Kim wrote:
>>> There is odd behaviour when we steal freepages from other migratetype
>>> buddy list. In try_to_steal_freepages(), we move all freepages in
>>> the pageblock that founded freepage is belong to to the request
>>> migratetype in order to mitigate fragmentation. If the number of moved
>>> pages are enough to change pageblock migratetype, there is no problem. If
>>> not enough, we don't change pageblock migratetype and add broken freepages
>>> to the original migratetype buddy list rather than request migratetype
>>> one. For me, this is odd, because we already moved all freepages in this
>>> pageblock to the request migratetype. This patch fixes this situation to
>>> add broken freepages to the request migratetype buddy list in this case.
>>
>> I'd rather split the fix from the refactoring. And maybe my
>> description is longer, but easier to understand? (I guess somebody
>> else should judge this)
>
> Your patch is much better to understand than mine. :)
> No need to judge from somebody else.
> After your patch is merged, I will resubmit these on top of it.

Thanks. I'm doing another evaluation focusing on number of unmovable 
pageblocks as Mel suggested and then resubmit with tracepoint fixed.

Vlastimil
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