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Date: Wed, 22 Jul 2009 09:12:08 +0200
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Subject: Re: UBI FS mounting time
From: Corentin Chary <corentin.chary@gmail.com>
To: Adrian Hunter <adrian.hunter@nokia.com>
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Cc: "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
	Bosi Daniele <Daniele.Bosi@mta.it>
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On Wed, Jul 22, 2009 at 8:44 AM, Adrian Hunter<adrian.hunter@nokia.com> wrote:
> Bosi Daniele wrote:
>>
>> We have a UBI+UBIFS 1GB partition on a NAND chip, which takes around 6s to
>> mount.
>>
>> We'd like to have the data available at least read-only earlier than that.
>>
>> We know UBI on principle needs to read the map of all blocks in order to
>> rebuild the logical view of the memory, but maybe there's another way around
>> it to make it available earlier...
>>
>> Someone know how?
>
> Some options are:
>
>
> a) Use another smaller partition that can mount first and provide some
> functionality while the larger partition mounts.
> b) Reduce the number of eraseblocks by combining them into larger logical
> blocks.
> c) Change UBI to write its mapping table when it is unloaded, so it can be
> read quickly when loading (still have to scan if UBI was not unloaded
> cleanly).

Do you know if someone is trying to implement that ?
I did some test, and using lzo/zlib it should be possible to store
such a mapping
store in only one PEB.
Then we can choose this PEB to be near the beginning of the
flash to speed up scanning (using ec and pnum to calculate a "score").
This is also possible to use an "anchor".




-- 
Corentin Chary
http://xf.iksaif.net - http://uffs.org