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