Date:	Tue, 28 Jan 2014 10:23:15 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Taras Glek <tglek@...illa.com>
Cc:	John Stultz <john.stultz@...aro.org>,
	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>, 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 05:09:59PM -0800, Taras Glek wrote:
> 
> 
> 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.
> Mozilla is starting to use android's ashmem for discardable memory
> within a single process:
> https://bugzilla.mozilla.org/show_bug.cgi?id=748598 .
> 
> Volatile ranges do help with that specific(uncommon?) use of ashmem.

Thanks for the info.

I'd like to ask a question.
Do you prefer fvrange(fd, offset, len) or fadvise(fd, offset, len, advise)
inteface rather than current vrange syscall interface for vrange-file?

Because I think it would remove unnecessary mmap/munmap syscall for vrange
interface as well as out of address space in 32bit machine.

> 
> For Mozilla sharing memory across processes via ashmem is not a
> nearterm project. It's something that is likely to require
> significant rework. Process-local discardable memory can be
> retrofited in a more straight-forward fashion.
> 
> Taras

-- 
Kind regards,
Minchan Kim
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