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

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Message-ID: <20130814164705.GD2706@gmail.com>
Date:	Thu, 15 Aug 2013 01:47:05 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Christoph Lameter <cl@...two.org>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	k.kozlowski@...sung.com,
	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Mel Gorman <mgorman@...e.de>, guz.fnst@...fujitsu.com,
	Benjamin LaHaise <bcrl@...ck.org>,
	Dave Hansen <dave.hansen@...el.com>, lliubbo@...il.com,
	aquini@...hat.com, Rik van Riel <riel@...hat.com>
Subject: Re: [RFC 0/3] Pin page control subsystem

Hi Christoph,

On Wed, Aug 14, 2013 at 04:36:44PM +0000, Christoph Lameter wrote:
> On Wed, 14 Aug 2013, Minchan Kim wrote:
> 
> > On Tue, Aug 13, 2013 at 04:21:30PM +0000, Christoph Lameter wrote:
> > > On Tue, 13 Aug 2013, Minchan Kim wrote:
> > >
> > > > VM sometime want to migrate and/or reclaim pages for CMA, memory-hotplug,
> > > > THP and so on but at the moment, it could handle only userspace pages
> > > > so if above example subsystem have pinned a some page in a range VM want
> > > > to migrate, migration is failed so above exmaple couldn't work well.
> > >
> > > Dont we have the mmu_notifiers that could help in that case? You could get
> > > a callback which could prepare the pages for migration?
> >
> > Now I'm not familiar with mmu_notifier so please could you elaborate it
> > a bit for me to dive into that?
> 
> Add a notifier callback for unpinning pages to the mmu notifier subsystem
> and then your drivers could register with the subsystem to get
> notifications when migration needs to occur etc.
> 

When I look API of mmu_notifier, it has mm_struct so I guess it works
for only user process. Right?
If so, I need to register it without user conext because zram, zswap
and zcache works for only kernel side.

-- 
Kind regards,
Minchan Kim
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