linux-kernel - RE: swap on eMMC and other flash

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Date:	Thu, 12 Apr 2012 08:32:57 +0000
From:	"Luca Porzio (lporzio)" <lporzio@...ron.com>
To:	Arnd Bergmann <arnd@...db.de>, Minchan Kim <minchan@...nel.org>
CC:	정효진 <syr.jeong@...sung.com>,
	"'Alex Lemberg'" <Alex.Lemberg@...disk.com>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"'Rik van Riel'" <riel@...hat.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"kernel-team@...roid.com" <kernel-team@...roid.com>,
	"'Yejin Moon'" <yejin.moon@...sung.com>,
	"'Hugh Dickins'" <hughd@...gle.com>,
	"'Yaniv Iarovici'" <Yaniv.Iarovici@...disk.com>,
	"cpgs@...sung.com" <cpgs@...sung.com>
Subject: RE: swap on eMMC and other flash

Hi All,

> -----Original Message-----
> From: linux-mmc-owner@...r.kernel.org [mailto:linux-mmc-owner@...r.kernel.org]
> On Behalf Of Arnd Bergmann
> Sent: Tuesday, April 10, 2012 1:40 AM
> To: Minchan Kim
> Cc: 정효진; 'Alex Lemberg'; linaro-kernel@...ts.linaro.org; 'Rik van Riel';
> linux-mmc@...r.kernel.org; linux-kernel@...r.kernel.org; Luca Porzio
> (lporzio); linux-mm@...ck.org; kernel-team@...roid.com; 'Yejin Moon'; 'Hugh
> Dickins'; 'Yaniv Iarovici'; cpgs@...sung.com
> Subject: Re: swap on eMMC and other flash
> 
> On Tuesday 10 April 2012, Minchan Kim wrote:
> > I think it's not good approach.
> > How long does it take to know such parameters?
> > I guess it's not short so that mkfs/mkswap would be very long
> > dramatically. If needed, let's maintain it as another tool.
> 
> I haven't come up with a way that is both fast and reliable.
> A very fast method is to time short read requests across potential
> erase block boundaries and see which ones are faster than others,
> this works on about 3 out of 4 devices.
> 
> For the other devices, I currently use a fairly manual process that
> times a lot of write requests and can take a long time.
> 
> > If storage vendors break such fields, it doesn't work well on linux
> > which is very popular on mobile world today and user will not use such
> > vendor devices and company will be gone. Let's give such pressure to
> > them and make vendor keep in promise.
> 
> This could work for eMMC, yes.
> 

I like it ;)

> The SD card standard makes it impossible to write the correct value for
> most devices, it only supports power-of-two values up to 4MB for SDHC,
> and larger values (I believe 8, 12, 16, 24, ... 64) for SDXC, but a lot
> of SDHC cards nowadays use 1.5, 3, 6 or 8 MB erase blocks.
> 
> 	Arnd
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