linux-kernel - Re: [RFC] memory-hotplug: remove MIGRATE_ISOLATE from free_area->free

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Date:	Thu, 06 Sep 2012 14:59:53 +0200
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Mel Gorman <mel@....ul.ie>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: [RFC] memory-hotplug: remove MIGRATE_ISOLATE from free_area->free_list

> On Wed, Sep 05, 2012 at 07:28:23PM +0200, Michal Nazarewicz wrote:
>> If you ask me, I'm not convinced that this improves anything.

On Thu, Sep 06 2012, Minchan Kim wrote:
> At least, it removes MIGRATE_ISOLATE type in free_area->free_list
> which is very irony type as I mentioned. I really don't like such
> type in free_area. What's the benefit if we remain code as it is?
> It could make more problem in future.

I don't really see current situation as making more problems in the
future compared to this code.

You are introducing a new state for a page (ie. it's not in buddy, but
in some new limbo state) and add a bunch of new code and thus bunch of
new  bugs.  I don't see how this improves things over having generic
code that handles moving pages between free lists.

PS.  free_list does exactly what it says on the tin -> the pages are
free, ie. unallocated.  It does not say that they can be allocated. ;)

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
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