linux-kernel - Re: [RFC 0/3] Pin page control subsystem

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Message-ID: <20130813142338.GD13330@kvack.org>
Date:	Tue, 13 Aug 2013 10:23:38 -0400
From:	Benjamin LaHaise <bcrl@...ck.org>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	Minchan Kim <minchan@...nel.org>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Mel Gorman <mgorman@...e.de>, guz.fnst@...fujitsu.com,
	Dave Hansen <dave.hansen@...el.com>, lliubbo@...il.com,
	aquini@...hat.com, Rik van Riel <riel@...hat.com>,
	Tomasz Stanislawski <t.stanislaws@...sung.com>
Subject: Re: [RFC 0/3] Pin page control subsystem

On Tue, Aug 13, 2013 at 11:46:42AM +0200, Krzysztof Kozlowski wrote:
> Hi Minchan,
> 
> On wto, 2013-08-13 at 16:04 +0900, Minchan Kim wrote:
> > patch 2 introduce pinpage control
> > subsystem. So, subsystems want to control pinpage should implement own
> > pinpage_xxx functions because each subsystem would have other character
> > so what kinds of data structure for managing pinpage information depends
> > on them. Otherwise, they can use general functions defined in pinpage
> > subsystem. patch 3 hacks migration.c so that migration is
> > aware of pinpage now and migrate them with pinpage subsystem.
> 
> I wonder why don't we use page->mapping and a_ops? Is there any
> disadvantage of such mapping/a_ops?

That's what the pending aio patches do, and I think this is a better 
approach for those use-cases that the technique works for.

The biggest problem I see with the pinpage approach is that it's based on a
single page at a time.  I'd venture a guess that many pinned pages are done 
in groups of pages, not single ones.

		-ben

> Best regards,
> Krzysztof

-- 
"Thought is the essence of where you are now."
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