linux-kernel - Re: [RFC PATCH 0/3] Aggressively allocate the pages on cma reserved memory

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Message-ID: <20140515094718.GE23991@suse.de>
Date:	Thu, 15 May 2014 10:47:18 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Laura Abbott <lauraa@...eaurora.org>,
	Minchan Kim <minchan@...nel.org>,
	Heesub Shin <heesub.shin@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	'Tomasz Stanislawski' <t.stanislaws@...sung.com>
Subject: Re: [RFC PATCH 0/3] Aggressively allocate the pages on cma reserved
 memory

On Thu, May 15, 2014 at 11:10:55AM +0900, Joonsoo Kim wrote:
> > That doesn't always prefer CMA region. It would be nice to
> > understand why grouping in pageblock_nr_pages is beneficial. Also in
> > your patch you decrement nr_try_cma for every 'order' allocation. Why ?
> 
> pageblock_nr_pages is just magic value with no rationale. :)

I'm not following this discussions closely but there is rational to that
value -- it's the size of a huge page for that architecture.  At the time
the fragmentation avoidance was implemented this was the largest allocation
size of interest.

-- 
Mel Gorman
SUSE Labs
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