linux-kernel - Re: [PATCH 1/3] mm/page_alloc: don't break highest order freepage if steal

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Message-ID: <20150427080850.GF2449@suse.de>
Date:	Mon, 27 Apr 2015 09:08:50 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Vlastimil Babka <vbabka@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 1/3] mm/page_alloc: don't break highest order freepage if
 steal

On Mon, Apr 27, 2015 at 04:23:39PM +0900, Joonsoo Kim wrote:
> When we steal whole pageblock, we don't need to break highest order
> freepage. Perhaps, there is small order freepage so we can use it.
> 

The reason why the largest block is taken is to reduce the probability
there will be another fallback event in the near future. Early on, there
were a lot of tests conducted to measure the number of external fragmenting
events and take steps to reduce them. Stealing the largest highest order
freepage was one of those steps.

-- 
Mel Gorman
SUSE Labs
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