RE: swap on eMMC and other flash

["Luca Porzio (lporzio)" <lporzio@micron.com>]

Hi All,

> -----Original Message-----
> From: linux-mmc-owner@vger.kernel.org [mailto:linux-mmc-owner@vger.kernel.org]
> On Behalf Of Arnd Bergmann
> Sent: Tuesday, April 10, 2012 1:40 AM
> To: Minchan Kim
> Cc: 정효진; 'Alex Lemberg'; linaro-kernel@lists.linaro.org; 'Rik van Riel';
> linux-mmc@vger.kernel.org; linux-kernel@vger.kernel.org; Luca Porzio
> (lporzio); linux-mm@kvack.org; kernel-team@android.com; 'Yejin Moon'; 'Hugh
> Dickins'; 'Yaniv Iarovici'; cpgs@samsung.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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