Bootloader question

Peter Robinson pbrobinson at gmail.com
Wed Jun 3 05:34:16 EDT 2009


>> Don't believe everything you read on a wiki.
>> OFW has included support for partitioned NAND since the first production
>> shipments, dating back to January 2008.  The idea is to have a small
>> boot partition that can be in any format that OFW supports - JFFS2,
>> ext2, FAT, or even a .zip archive.  JFFS2 is just fine on a small
>> partition; the scan time for a few MB is negligeable. I have been
>> lobbying for such a structure for about 2 years now, but never managed
>> to get enough traction among the OS people to actually implement it in
>> the XO software distribution.  The OFW support for this is known to
>> work, as debxo uses it.
>
> I'm sorry, I didn't know that and I didn't want to imply OFW was not
> the right tool for the job.
>
> I'm just very concerned by the current time it takes for a vanilla
> olpc to be ready, especially when compared to any netbook running
> moblin, so I'm exploring various ways to fix the problem (actually
> rereading every documentation that was send to me explaining various
> aspect of the OFW before starting the UBIFS tests, but I have limited
> time and I'd like to spend in on the UI rather than  on the boot
> process)

A lot of the changes that you see in moblin are already in newer
kernels and even added to the boot process in Fedora which will be
part of the next XO software release. You also have to realise that a
atom cpu with a gig of ram and a relatively fast SSD are hardware wise
an order of magnitude faster than the current Gen 1 XO hardware. The
current stable release of the XO software is based on Fedora 9 and
even on my relatively fast Dell laptop running Fedora 11 the time to
boot from F-9 to F-11 has dropped by well over 2 minutes with all the
various improvements that have been made to kernel device scanning, X
startup and various other improvements.

> What would you suggest to have the kernel loaded in ram as quickly as
> possible? (I'd guess execute in place, but I think that's not
> possible) A fat partition with the zimage ?

The time it takes for a kernel to be loaded into RAM is hardware
dependant on things like the speed/bandwidth of the storage/bus/ram
etc

> I'd also like to remove the initrd to try to shave some seconds. I
> don't need any antitheft protection, I just want to protect the nand
> against a reflash with a non approved software image, which IMHO is
> the most interesting feature of OFW. But if that's too
> complicated/requires the initrd or some weird other stuff, I'll scrap
> that too.

I'm not sure you'll save that much by removing it. If you really want
to play with boot speed I suggest you flash on a copy of Fedora 11 and
then use some of their boot profiling tools to test and see where you
can save time.

> BTW, could you point me to some documentation explaining how to have
> OFW immediately boot a kernel, without fancy sound/screen/counter?
> (only prioritising USB or MMC, so that it boots first if a media is
> inserted or if a struck "esc" key is detected it gives a command
> prompt)

At a guess you'd need to recompile the OFW to remove them. I doubt it
will save much time.

> I'm open to any additional suggestions. (I'll consider the sysvinit
> optimisations later)

What version of XO software are you running? Have you tried SOAS or
one of the F11/rawhide test images to see if that improves speed at
all over 8.2.1?

Peter


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