linux-kernel - Re: [PATCH 0/4] enable migration of driver pages

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Message-ID: <20150729124635.GW16722@phenom.ffwll.local>
Date:	Wed, 29 Jul 2015 14:46:35 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	Gioh Kim <gioh.kim@....com>, jlayton@...chiereds.net,
	bfields@...ldses.org, vbabka@...e.cz, iamjoonsoo.kim@....com,
	viro@...iv.linux.org.uk, mst@...hat.com, koct9i@...il.com,
	minchan@...nel.org, aquini@...hat.com,
	linux-fsdevel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	linux-mm@...ck.org, dri-devel@...ts.freedesktop.org,
	akpm@...ux-foundation.org, Gioh Kim <gurugio@...mail.net>
Subject: Re: [PATCH 0/4] enable migration of driver pages

On Wed, Jul 29, 2015 at 01:16:14PM +0100, Mel Gorman wrote:
> On Wed, Jul 29, 2015 at 12:55:54PM +0200, Daniel Vetter wrote:
> > On Wed, Jul 29, 2015 at 11:49:45AM +0100, Mel Gorman wrote:
> > > On Mon, Jul 13, 2015 at 05:35:15PM +0900, Gioh Kim wrote:
> > > > My ARM-based platform occured severe fragmentation problem after long-term
> > > > (several days) test. Sometimes even order-3 page allocation failed. It has
> > > > memory size 512MB ~ 1024MB. 30% ~ 40% memory is consumed for graphic processing
> > > > and 20~30 memory is reserved for zram.
> > > > 
> > > 
> > > The primary motivation of this series is to reduce fragmentation by allowing
> > > more kernel pages to be moved. Conceptually that is a worthwhile goal but
> > > there should be at least one major in-kernel user and while balloon
> > > pages were a good starting point, I think we really need to see what the
> > > zram changes look like at the same time.
> > 
> > I think gpu drivers really would be the perfect candidate for compacting
> > kernel page allocations. And this also seems the primary motivation for
> > this patch series, so I think that's really what we should use to judge
> > these patches.
> > 
> > Of course then there's the seemingly eternal chicken/egg problem of
> > upstream gpu drivers for SoCs :(
> 
> I recognised that the driver he had modified was not an in-tree user so
> it did not really help the review or the design. I did not think it was
> very fair to ask that an in-tree GPU driver be converted when it would not
> help the embedded platform of interest. Converting zram is both a useful
> illustration of the aops requirements and is expected to be beneficial on
> the embedded platform. Now, if a GPU driver author was willing to convert
> theirs as an example then that would be useful!

Well my concern is more with merging infrastructure to upstream for
drivers which aren't upstream and with no plan to make that happen anytime
soon. Seems like just offload a bit to me ... but in the end core mm isn't
my thing so not my decision.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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