UBI, no sub-pages support

UBI, no sub-pages support

[Angelo Dureghello]

Dear all,

i am running UBI/UBIFS on a TI AM1808 / OPAM-L cpu, MT29F1G08 NAND and
kernel 3.5.1.

MT29F1G08 has 128KB pages, and 2048B PEB's.

After first attempt to create UBI/UBIFS image using 512B sub-pages, i
had several UBI errors, so i realized sub-pages are not supported in the
OMAP-L driver at this kernel version (seems to start to be supported
form 3.10.x).

So i prepare the image from buildroot without subpage now, with these
settings:

      [ ] jffs2 root filesystem
      [*] ubifs root filesystem
      (0x1f000) UBI logical erase block size
      (0x800) UBI minimum I/O size
      (1024) Maximum LEB count
         ubifs runtime compression (gzip)  --->
         Compression method (no compression)  --->
      [*]   Embed into an UBI image
      (0x20000) UBI physical erase block size
      (0)     UBI sub-page size

buildroot/output/host/usr/sbin/mkfs.ubifs --space-fixup -d
buildroot/output/target -e 0x1f000 -c 1024 -m 0x800 -x zlib -o
buildroot/output/images/rootfs.ubifs


buildroot/output/host/usr/sbin/ubinize -o
buildroot/output/images/rootfs.ubi -m 0x800 -p 0x20000 ubinize.cfg

I executed both mtd-utils "runtest.sh" and integck, and had no issues.
Could you maybe confirm this settings are correct and i am not going
trough issues using the fs ?

Another question is: is there a UBI performance loss using pages as
minimal I/O (no subpages) or i can consider it insignificant ?

Many Thanks
Angelo Dureghello

Re: UBI, no sub-pages support

[Artem Bityutskiy]

On Tue, 2014-08-19 at 13:28 +0200, Angelo Dureghello wrote:
> Another question is: is there a UBI performance loss using pages as
> minimal I/O (no subpages) or i can consider it insignificant ?

I can only comment on this question - you should not lose performance,
but you'll have more NAND flash space consumed by UBI for its own
purposes, comparing to what you'd have if you had sub-pages.

IOW, sub-pages are mostly lessening the UBI space overhead.

The MTD web page has a section about the space overhead with some more
information.

-- 
Best Regards,
Artem Bityutskiy