Message-ID: <20140128010253.GD25066@bbox>
Date:	Tue, 28 Jan 2014 10:02:53 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	John Stultz <john.stultz@...aro.org>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Michel Lespinasse <walken@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Dhaval Giani <dhaval.giani@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Android Kernel Team <kernel-team@...roid.com>,
	Robert Love <rlove@...gle.com>, Mel Gorman <mel@....ul.ie>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Dave Chinner <david@...morbit.com>, Neil Brown <neilb@...e.de>,
	Andrea Righi <andrea@...terlinux.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Mike Hommey <mh@...ndium.org>, Taras Glek <tglek@...illa.com>,
	Jan Kara <jack@...e.cz>, Rob Clark <robdclark@...il.com>,
	Jason Evans <je@...com>, pliard@...gle.com
Subject: Re: [PATCH v10 00/16] Volatile Ranges v10

On Mon, Jan 27, 2014 at 04:42:27PM -0800, John Stultz wrote:
> On 01/27/2014 04:12 PM, Minchan Kim wrote:
> > On Mon, Jan 27, 2014 at 05:23:17PM -0500, KOSAKI Motohiro wrote:
> >> - Your number only claimed the effectiveness anon vrange, but not file vrange.
> > Yes. It's really problem as I said.
> > From the beginning, John Stultz wanted to promote vrange-file to replace
> > android's ashmem and when I heard usecase of vrange-file, it does make sense
> > to me so that's why I'd like to unify them in a same interface.
> >
> > But the problem is lack of interesting from others and lack of time to
> > test/evaluate it. I'm not an expert of userspace so actually I need a bit
> > help from them who require the feature but at a moment,
> > but I don't know who really want or/and help it.
> >
> > Even, Android folks didn't have any interest on vrange-file.
> 
> Just as a correction here. I really don't think this is the case, as
> Android's use definitely relies on file based volatility. It might be
> more fair to say there hasn't been very much discussion from Android
> developers on the particulars of the file volatility semantics (out
> possibly not having any particular objections, or more-likely, being a
> bit too busy to follow the all various theoretical tangents we've
> discussed).
> 
> But I'd not want anyone to get the impression that anonymous-only
> volatility would be sufficient for Android's needs.

Right. Thanks for the correction.

> 
> 
> (And to further clarify here, since this can be confusing... 
> shmem/tmpfs-only file volatility *would* be sufficient, despite that
> technically being anonymous backed memory. The key issue is we need to
> be able to share the volatility between processes.)
> 
> 
> > So, we might drop vrange-file part in this patchset if it's really headache.
> > But let's discuss further because still I believe it's valuable feature to
> > keep instead of dropping.
> 
> If it helps gets interest in reviewing this, I'm ok with deferring
> (tmpfs) file volatility, so folks can get comfortable with anonymous
> volatility. But I worry its too critical a feature to ignore.

Yes. I don't want to drop it without more discussion with real user
of it but the problem is it's very hard to find one to have extra time
to discuss it.


> 
> thanks
> -john
> 
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-- 
Kind regards,
Minchan Kim
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