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Date: Wed, 22 Jul 2009 12:19:04 +0300
From: Adrian Hunter <adrian.hunter@nokia.com>
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To: Canella Matteo <Matteo.Canella@mta.it>
Subject: Re: UBI FS mounting time
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Canella Matteo wrote:
> Just to understand if we're doing things in the right way...
> we need more than 6 secs to mount 1 GB Nand Flash. 
> Does this sound a normal timing?

Yes

> This is the dmesg of the flash mounting:
> 
> [    6.694626] UBI: attaching mtd10 to ubi2
> [    6.698594] UBI: physical eraseblock size:   131072 bytes (128 KiB)
> [    6.705712] UBI: logical eraseblock size:    126976 bytes
> [    6.711154] UBI: smallest flash I/O unit:    2048
> [    6.715894] UBI: sub-page size:              512
> [    6.720533] UBI: VID header offset:          2048 (aligned 2048)
> [    6.726564] UBI: data offset:                4096
> [   12.802282] UBI: attached mtd10 to ubi2
> [   12.806179] UBI: MTD device name:            "nand"
> [   12.814531] UBI: MTD device size:            1024 MiB
> [   12.820304] UBI: number of good PEBs:        8185
> [   12.825069] UBI: number of bad PEBs:         7
> [   12.829495] UBI: max. allowed volumes:       128
> [   12.834144] UBI: wear-leveling threshold:    4096
> [   12.838891] UBI: number of internal volumes: 1
> [   12.843425] UBI: number of user volumes:     1
> [   12.847860] UBI: available PEBs:             0
> [   12.852325] UBI: total number of reserved PEBs: 8185
> [   12.857340] UBI: number of PEBs reserved for bad PEB handling: 81
> [   12.863479] UBI: max/mean erase counter: 6/3
> [   12.867807] UBI: background thread "ubi_bgt2d" started, PID 911

The possibility exists to double the eraseblock size by treating 2 eraseblocks as
though it was 1.  That should halve the UBI load time to 3 seconds but it would
use a bit more memory in UBIFS.  Of course you could double again, with yet
more memory required by UBIFS.